University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

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Classification: Food

Citations 141

"Simultaneous Determination Of Nitrite And Nitrate In Various Samples Using Flow Injection With Spectrophotometric Detection"
Anal. Chim. Acta 1999 Volume 382, Issue 1-2 Pages 15-21
Ali A. Ensafi and A. Kazemzadeh

Abstract: A direct spectrophotometric method for the simultaneous determination of nitrite and nitrate by flow injection analysis has been developed. The method is based on catalytic effect of nitrite on the oxidation of gallocyanine by bromate in acidic media and the decrease in absorbance of the system at 530 nm. The injected sample is split into two segments. One of the streams was directly treated with the above reagents and passed to the sample how cell of the spectrophotometer. The decrease in absorbance at 530 nm is due to the nitrite. The other stream was passed through a reductor minicolumn containing copperized-cadmium, where reduction of nitrate to nitrite occurs, and then the sample was treated with the mixed reagents and was passed through the same cell of the spectrophotometer. The total nitrite concentration initially plus that produced was determined. The influences of reagent concentration and manifold parameters were studied. The effect of potential interfering ions was examined. Nitrite and nitrate can be determined for the range of 0.010-2.500 µg mL-1 and 0.020-3.500 µg mL-1, respectively. The sampling rate of analysis was 20±3 hr-1, with 3s detection limits of 0.001 and 0.002 µg mL-1 for nitrite and nitrate, respectively. Nitrite and nitrate were determined in food and water samples by the proposed method with satisfactory results.
Nitrate Nitrite Spectrophotometry Catalysis Indirect Reduction column Simultaneous analysis Optimization Interferences

"Development Of An Interferent Free Amperometric Biosensor For Determination Of L-lysine In Food"
Anal. Chim. Acta 2000 Volume 412, Issue 1-2 Pages 111-119
S. C. Kelly, P. J. O'Connell, C. K. O'Sullivan and G. G. Guilbault

Abstract: A highly selective, fast responding amperometric biosensor is described, useful for the determination of L-lysine in food. Common electrochemical interferences, like acetoaminophen and ascorbic acid have zero response at +100 mV applied onto a ruthenium/rhodium coated glassy carbon electrode covered with 1,2-diaminobenzene polymer. This novel transducer was coupled with L-lysine α-oxidase purified from Trichoderma viride and at the appropriate pH, classic substrate interferences from L-ornithine, L-arginine and L-phenylalanine are reduced to 3.4, 1.1 and 0.7% of the response to L-lysine (taken as 100%). No other amino acids respond. The sensor is inexpensive to produce, has excellent repeatability and very good reproducibility. Thus, the L-lysine (protein) content of foods can be almost specifically determined following rapid microwave digestion of the product.
l-Lysine Amperometry Sensor Electrode Sample preparation Interferences Detector

"Preparation Of Reagents For The Determination Of Fumonisin B1 By Flow Injection Immunoanalysis"
Anal. Chim. Acta 2000 Volume 414, Issue 1-2 Pages 51-60
Ja-an A. Ho and Richard A. Durst

Abstract: Methods for the synthesis of fumonisin B1 (FmB1) immunoconjugates and for the preparation of FmB1-tagged liposomes were developed and studied. Keyhole limpet hemocyanin-fumonisin B1 (KLH-FmB1) was synthesized using both the classical glutaraldehyde (GA) protocol and a modified 2-step GA protocol. The immunoconjugate was then used to raise polyclonal antibodies in Rambouilet sheep. The covalent coupling of FmB1 to the outer surface of the liposomes involved the derivatization of the FmB1 with a maleimide group which was allowed to react with a sulfhydryl group on the liposome surface. The maleimide group was introduced into the FmB1 via a hetero-bifunctional reagent sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate (sulfo-SMCC). The sulfhydryl group was generated by the deacetylation of an acetylthioacetate group that was incorporated into the lipid bilayer after the interaction of dipalmitoyl phosphatidyl ethanolamine (DPPE) with N-succinimidyl-S-acetylthioacetate (SATA). The sheep anti-FmB1 polyclonal antibodies as well as sulforhodamine B (SRB) dye-encapsulating, FmB1-tagged liposomes were used subsequently in the development of a Flow injection Liposome ImmunoAnalysis (FILIA) system for the detection of FmB1 in food.
Fumonisin B1 Immunoassay Instrumentation

"Development Of A Flow Injection Liposome Immunoanalysis System For Fumonisin B1"
Anal. Chim. Acta 2000 Volume 414, Issue 1-2 Pages 61-69
Ja-an A. Ho and Richard A. Durst

Abstract: Fumonisins are a group of naturally occurring mycotoxins produced by several species of the fungus Fusarium (mainly moniliforme) and occur worldwide on corn intended for human and animal consumption. Contamination of food and feed with fumonisins has been implicated in and associated with a number of diseases in both livestock as well as human beings. In this study, a Flow injection Liposome ImmunoAnalysis (FILIA) system was developed for the heterogeneous quantitative determination of fumonisin B1 (FmB1). The immunoassay is based on the competition between FmB1 and sulforhodamine B (SRB) dye-encapsulating, FmB1-tagged liposomes for a limited number of antibody binding sites. The antibodies are immobilized via protein A in a capillary immunoreactor column, and 35% MeOH is used for the regeneration of antibody binding sites after each measurement, which allows the immunoreactor to be used for up to 70 sequential sample injections without any loss of reactivity. Sample pre-concentration is not needed and a single assay can be performed in less than 11 min. The calibration curve for FmB1 in Tris-buffered saline (TBS) solution had a working range of 1-1000 ng/ml.
Fumonisin B1 Immunoassay Sensor Capillary Immobilized antibody Reactor

"Analytical Pervaporation: An Advantageous Alternative To Headspace And Purge-and-trap Techniques"
Chromatographia 2000 Volume 52, Issue 5-6 Pages 265-272
M. D. Luque de Castro and L. Gámiz-Gracia

Abstract: An overview of the principles and general applications of analytical pervaporation is presented. The different designs of both the analytical pervaporation module and the continuous manifolds to which the pervaporator is connected are discussed. The versatility of this non-chromatographic continuous separation technique for circumventing some of the shortcomings encountered in the automation of the overall analytical process is shown. Examples of methods developed for samples (both liquid and solid) in the environmental, food and beverage, and clinical and pharmaceutical fields are shown. The potential of pervaporation as an alternative to static and dynamic well-established approaches such as headspace and purge-and-trap sampling prior to gas-chromatographic separation is demonstrated. Examples of this approach involving both solid and liquid samples are discussed.
Spectrophotometry Review Pervaporation

"Kinetic-turbidimetric Determination Of Phytic Acid By Sequential Injection Analysis"
Anal. Chim. Acta 2000 Volume 409, Issue 1-2 Pages 9-16
J. G. March, B. M. Simonet and F. Grases

Abstract: A sequential injection analysis method with kinetic-turbidimetric detection for the determination of phytic acid is described. The method is based on the diminution of the calcium oxalate crystallisation reaction rate in the presence of phytic acid. Such a crystallisation rate has been evaluated from the increase of turbidity with time. A linear calibration graph was obtained from 0.05 to 0.6 mg L-1 phytic acid and the relative standard deviation (n=5) was 2.0% for a standard of 0.25 mg L-1 phytic acid. The method was applied to the determination of phytic acid in food samples (after purification by anion exchange chromatography) and compared with an indirect extraction-spectrophotometric determination based on the hydrolysis of phytic acid and determination of released phosphate.
Phytic acid Turbidimetry Kinetic Sequential injection Indirect Method comparison

"Electrochemical Sensor Arrays"
Crit. Rev. Anal. Chem. 1999 Volume 29, Issue 2 Pages 133-153
Raluca-Ioana Stefan, Jacobus F. Van Staden and Hassan Y. Aboul-Enein

Abstract: The importance of sensor arrays in environmental, food and clinical analysis is discussed. The possible designs of sensor arrays is shown. The most reliable mathematical models for data processing are presented. The importance of different types of electrochemical sensor arrays in analytical chemistry as well as their performances are shown.
Sensor Electrochemical analysis Chemometrics Non-immobilized enzyme Review

"Microwave-assisted Sample Preparation In Sequential Injection: Spectrophotometric Determination Of Magnesium, Calcium And Iron In Food"
Anal. Chim. Acta 2000 Volume 413, Issue 1-2 Pages 41-48
Cláudio C. Oliveira, Raquel P. Sartini and Elias Ayres Guidetti Zagatto

Abstract: A sequential injection system for spectrophotometric analysis of foods and similar involving direct sample introduction as a natural suspension or as slurry is proposed. Sample and concentrated nitric acid are sequentially aspirated and directed towards a digestion bomb located inside a microwave oven where sample decomposition takes place. After digestion, aliquots of the processed sample and randomly selected reagents are sequentially aspirated towards the holding coil and pumped towards the detector. As application, magnesium, calcium and iron were determined in milli, soft drinks and similar by using o-cresolphthalein (with or without EGTA addition) and o-phenanthroline as color forming reagents. The system is versatile, and yields reproducible results (RSD <0.04 for 5.0-50.0 mg L-1 Mg, 15.0-150 mg L-1 Ca and 2.0-20.0 mg L-1 Fe) in agreement with flame atomic absorption spectrometry involving the manual sample digestion procedure.
Magnesium Calcium Iron Spectrophotometry Sample preparation Sequential injection Method comparison Online digestion

"Flow Injection Catalytic Spectrophotometric Determination Of Oxalic Acid Using The Redox Reaction Between Victoria Blue B And Dichromate"
Anal. Chim. Acta 2000 Volume 406, Issue 2 Pages 303-308
Zhi-Qi Zhang and Xiao-Qin Xu

Abstract: A flow injection catalytic method is developed for the determination of oxalic acid based on its catalytic effect on the redox reaction between Victoria blue B and potassium dichromate in dilute sulfuric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of Victoria blue B at the maximum absorption wavelength of 618 nm. A calibration graph from 1.0 to 80.0 µg mL-1 of oxalic acid and a detection limit of 0.8 µg mL-1 was obtained. The sampling rate was about 22 samples per hour. The proposed method is simple and inexpensive. The applicability of the method was demonstrated by the determination of oxalic acid in vegetable food, such as spinach and mushroom.
Oxalic acid Spectrophotometry Catalysis Indirect

"Determination Of The Antioxidant Octylgallate In Food Using A Polypyrrole Electrode Modified With Nickel Phthalocyanine Complex. First Measurements In A FIA System"
Quim. Anal. 1999 Volume 18, Issue 2 Pages 209-216
A. Guadarrama, C. de la Fuente, J.A. Acu&ntilde;a, M.D. V&aacute;zquez, M.L. Tasc&oacute;n and P. S&aacute;nchez-Batanero

Abstract: A polypyrrole film doped with tetrasulfonated nickel (II) phthalocyanine complex, coated by electrochemical polymerisation on a platinum surface, was proved as a good electrochemical detector for the voltammetric analysis of the octylgallate (OG) in food. During the electrode generation, the potential of the Pt electrode was controlled at +0.8 V (versus Ag/AgClI/KCl(s) electrode) in aqueous solution. The detection is based on the electrocatalytic properties of the modified conducting polymer. Cyclic voltammograms showed a well-defined oxidation peak for OG. The influence of pH and of methanol/water ratio in the OG observed response, the cyclic voltammetry and difference pulse voltammetry experimental conditions, as well as, the influence of the presence of other phenolic antioxidants were optimized. A detection limit in the order of micromolar concentration was estimated. The developed analytical method was applied to the determination of OG in food, showing its validity. On the other hand, we have used the polymeric electrode in a FIA system, opening new possibilities for future investigations.
Octylgallate Voltammetry Electrode

"Flow Injection Analysis With A Fluorimetric Detector For Determinations Of Glycine And Albumin"
Anal. Chim. Acta 1979 Volume 106, Issue 2 Pages 395-399
Joy I. Braithwaite and J. N. Miller

Abstract: Flow injection analysis with fluorometric detection was used in the determination of glycine and albumin, with o-phthalaldehyde being used in determination of the latter. Preliminary variables and applications of flow injection analysis were examined, using quinine sulfate and m-hydroxybenzoic acid which are intrinsically fluorescent. System response was linear in the range of 0-8 µg/mL for glycine and concentrations as low as 2 pg/mL were detectable. The level of glycine in orange juice and dietetic cola was 0.33-0.41 and 0.17 g/dL, respectively. Serum albumin determinations flow injection analysis had a relative standard deviation of 1.8%. The method allowed sampling rates of 180/h for both glycine and albumin.
Glycine Albumin Clinical analysis Fluorescence Optimization

"Preconcentration And Differential Pulse Voltammetry Of Butylated Hydroxyanisole At A Carbon Paste Electrode"
Anal. Chim. Acta 1983 Volume 154, Issue 1 Pages 87-94
Joseph Wang and Bassama A. Freiha

Abstract: Butylated hydroxyanisole (I) and tocopherols were pre-concentrated by accumulation on carbon-paste electrodes (2.5 g of Acheson graphite, grade 38, plus 1.5 g of Dow Corning silicone grease). After pre-concentration for 5 min, a detection limit of ~20 µM-I was obtained. Enhanced selectivity was achieved by transferring the electrode to an electrolytic blank solution before the measurement step; this enabled the surface-bound species to be measured without interference from species in solution The differential pulse stripping response was evaluated with respect to concentration. dependence, reproducibility, pre-concentration period, detection limit and other variables. The cited method was used in the selective detection of I in a flow injection system based on a recently developed manifold procedure (Anal. Chem., 1983, 55, 1285). The method was applied to, e.g., soft drinks, maize oil and multivitamin tablets.
Butylated hydroxyanisole Tocopherols Electrode Voltammetry Interferences Preconcentration

"Simultaneous Determination Of Hypoxanthine, Inosine, Inosine-5'-phosphate And Adenosine-5'-phosphate With A Multielectrode Enzyme Sensor"
Anal. Chim. Acta 1984 Volume 164, Issue 1 Pages 139-146
Etsuo Watanabe, Shunsuke Tokimatsu and Kenzo Toyama, Isao Karube, Hideaki Matsuoka and Shuichi Suzuki

Abstract: A multielectrode enzyme sensor for the simultaneous determination of adenosine-5'-phosphate (AMP), inosine-5'-phosphate (IMP), inosine (HXR) and hypoxanthine (HX)in fish meat was developed by assembling four enzyme sensors for AMP, IMP, HXR and HX in a flow cell. These compounds were determined from oxygen consumption according to the following reactions: AMP→IMP→HXR→HX→Uric acid where AD is AMP deaminase, NT is 5'-nucleotidase, NP is nucleoside phosphorylase and XO is xanthine oxidase. Enzymes were covalently bound to a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane and glutaraldehyde. Sensors for HX, HXR, IMP and AMP were prepared by attaching membranes of XO, XO---NP, XO--- NP---NT, and of XO---NP---NT and AD, respectively, to four oxygen electrodes. Samples extracted from sea bass, bream, flounder, abalone and arkshell were analyzed within 5 min, from the simultaneous response curves of the four electrodes. Results obtained by the multisensor system were in good agreement with those determined by each single electrode.
Electrode Sensor Apparatus

"Stopped-flow Injection Determination Of Copper(II) At The Ng/ml Level"
Anal. Chim. Acta 1984 Volume 165, Issue 1 Pages 177-185
F. L&aacute;zaro, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: The catalytic action of Cu(II) on the di-2-pyridyl ketone hydrazone - H2O2 system is quantitative. The oxidation product shows an intense blue fluorescence at 427 nm (excitation at 350 nm) in a strongly acidic medium. The sampling rate (72 h-1), coefficient of variation (1.4%) and freedom from interference from most foreign ions allow determination of 0.2 to 300 ng mL-1 of Cu in foods (e.g., fruits and rice) and blood serum.
Copper(II) Fluorescence Interferences Catalysis Stopped-flow PPB

"Comparison Of Two Fibre-optic L-glutamate Biosensors Based On The Detection Of Oxygen Or Carbon Dioxide, And Their Application In Combination With Flow Injection Analysis To The Determination Of Glutamate"
Anal. Chim. Acta 1991 Volume 248, Issue 2 Pages 351-359
Bernd A. A. Dremel and Rolf D. Schmid, Otto S. Wolfbeis

Abstract: Food or pharmaceutical prep. was dissolved in boiling H20 and the mixture was filtered. The filtrate was subjected to flow injection analysis with mixing with the carrier solution [0.1 M potassium phosphate buffer (pH 7.0 or 5.0)] and passing through an air damper before detection in the flow-through cell with use of a glutamate biosensor. The biosensor was based on (i) oxygen optrode with immobilized glutamate oxidase, or (ii) carbon dioxide optrode with immobilized glutamate decarboxylase. Detection was at 495 or 560 nm (excitation at 400 or 460 nm) for detectors (i) and (ii), respectively. The corresponding calibration graphs were rectilinear for 0.02 to 1 mM and 0.1 to 2.5 mM glutamate. The coefficient of variation were ~3% (n = 5). Interference from volatile acids was observed with detector (ii). Detector (i) was recommended.
Carbon dioxide Glutamate Oxygen Fluorescence Sensor Optrode Buffer Immobilized enzyme Interferences Optical fiber

"Fully Automated System For The Continuous Monitoring Of Ammonium Ion In Fish-farming Plant Seawater By Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 345-349
Hideki Muraki*, Keiro Higuchi, Masanori Sasaki, Takashi Korenaga, Kyoji T&ocirc;ei

Abstract: The sample (200 µL) is introduced by an automatic injector into 3.5% NaCl solution as carrier (which has the same relative density as seawater). This stream is merged with aqueous 10% Na salicylate - 1.9% K Na tartrate, then mixed with NaClO solution (6% of active Cl) - 0.5 M NaOH (1:99) in a 2-m reaction coil at 80°C before detection at 600 nm. Calibration is rectilinear for up to 3.0 mg L-1 of ammonium-N, and at 1.0 mg L-1 the coefficient of variation was 0.35% (n = 20). Under the conditions used, common anions, Na+, Ca2+, Mg2+ and Fe3+ do not interfere. The method was applied to fish-farming seawater. An automated system for the continuous monitoring of NH4+ in fish farming plant seawater is described. The sample is introduced into a carrier stream by an automated sample injector and merged with a reagent solution containing Na salicylate and Na nitroprusside. The sample stream is then mixed with a second reagent solution containing NaClO and heated at 50°C. The absorbance of the resulting solution is monitored at 660 nm. The calibration graph was linear up to at least 3.0 mg NH4+-N/L. The relative standard deviation for 20 injections of samples containing 1.0 mg NH4+-N/L was 0.35%. The interference from Ca2+ and Mg2+ was masked with K Na tartrate. The interference due to amino acids and proteins present in fish foods and wastes was eliminated by adjusting the pH to 6-7 when the sample merged with the 1st reagent solution
Ammonia Spectrophotometry Heated reaction Interferences Automation

"Determination Of L-glutamate By Amperometric Flow Injection Analysis Using Immobilized Glutamate Oxidase: Manifold For Simultaneous Detection Of Component Signal And Blank Signal"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 155-159
Kiyoshi Matsumoto*, Koji Sakoda and Yutaka Osajima

Abstract: The system described (with diagrams) allows simultaneous detection of the L-glutamate (I) signal and the blank value. A microtube pump propels the carrier solution (0.1 M phosphate buffer of pH 7) and the sample solution to a 16-position switching valve; the carrier line includes an air damper, and two 180 µL sample loops are linked to the valve for injection. The stream of solution then passes through a glass tube (10 cm x 2 mm i.d.) containing glutamate oxidase immobilized on Amino-Cellulofine by means of glutaraldehyde (method described) or (for blank measurement) an enzyme-free Amino-Cellulofine column to a potentiostat (Anal. Chem., 1988, 60, 147) maintained at +0.65 V vs. Ag - AgCl for amperometry of the H2O2 produced. The blank signal is obtained from a sample that has passed through the blank reactor; the carrier solution is used to set the baseline. Response to L-aspartate and L-glutamine was only 0.48 and 0.25%, respectively, relative to that for I; complete selectivity for I over L-aspartate is attainable at pH 6.0. Sensor response is maintained for 15 days. Peak current is rectilinearly related to I concentration. from 0.01 to 0.3 mM; the coefficient of variation at 0.3 mM was 1.7% (n = 10). The method was applied to a range of foods. L-Glutamate oxidase was immobilized on Amino-Cellulofine and used as an enzyme reactor in a flow injection system. The hydrogen peroxide produced was monitored amperometrically. A new configuration is described for the determination of L-glutamate in food samples for which the matrix provides varying blank values. The peak current was linearly related to L-glutamate concentration. in the range 0.01-.03 mM, and the relative standard deviation was 1.7% in ten successive assays at the 0.3 mM level. The proposed method was used for seasoning anal. and compared well with results obtained with an L-glutamate kit (enzymatic, spectrophotometric) method.
l-Glutamate Amperometry Signal enhancement Method comparison Immobilized enzyme pH

"Determination Of Cadmium In Foodstuffs And Plant Materials By Flow Injection Spectrophotometry Including Ion Exchange"
Anal. Chim. Acta 1995 Volume 306, Issue 2-3 Pages 343-349
Jos&eacute;A. Gomes Neto, H. Bergamin Filho, Raquel P. Sartini and Elias Ayres G. Zagatto*

Abstract: Dried powdered food or plant material (1 g) was digested with 10 mL of HNO3 for 30 min at 50°C; 2 mL of 30% H2O2 was added and the mixture evaporated to near dryness at 110°C. The residue was dissolved in 10 mL of 0.1 M HNO3 and diluted to 25 mL with water for FIA. The sample stream (3.8 ml/min) merged with an acidic NaCl stream (1.2 ml/min) then the flow passed through a strongly basic AG1 X-8 BioRad column (1 cm x 5 mm i.d.) and the Cd chlorocomplexes were retained. The flow-through the column was reversed and the analyte was eluted with 2 M NaNO3/0.1 M HNO3 (2.9 ml/min). The flow was merged with 75 µg Cd in 0.25 M ammonium acetate solution (1.2 ml/min) and then a second reagent stream which had been formed by merging 0.5 mM Malachite green and 2 M KI in 0.5% ascorbic acid (both at 0.5 ml/min); detection was at 690 nm. The detection limit was 0.11 µg/l Cd; RSD for sample digests containing 19.7 and 5.12 µg/l Cd were 2.26% and 2.72%, respectively (n = 12). The method was validated by analyzing standard reference materials (rice flour, pig kidney, dried copepoda) containing 0.75-2.71 µg/g Cd (results given). A second anion-exchange column was added to the FIA system to enable the analysis of samples which had been mineralized with HNO3/perchloric acid.
Cadmium Ion exchange Spectrophotometry Biorad Reference material

"Preconcentration Of An Analyte Dialysate In A Flow Injection System"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 214-221
J. F. van Staden* and C. J. Hattingh

Abstract: An FIA system with online dialysis, pre-concentration by ion-exchange and detection by AAS was evaluated and optimized. The various functions of the system were controlled by a time regulated system from a computer. The system was used to determine Cu in vitamin and mineral food supplements for dogs and cats. A 2 g portion of the food supplement was shaken with water for 30 min and the resulting slurry was diluted to 1000 mL with ammonium acetate/ammonia buffer at pH 8.7 (buffer A). After allowing insoluble material to settle, 22 µL of the supernatant was injected into the donor stream (buffer A, 2.5 ml/min) of the FIA manifold. After passing through the dialyser unit, the acceptor stream (buffer A, 1.4 ml/min) was propelled through an Dionex OnGuard-H ion-exchange column (1.2 cm x 1.4 mm i.d.). The flow-through the ion-exchange column was reversed and the retained Cu was eluted by injecting 1 mL of eluent into the buffer stream. Cu was determined by AAS at 324.6 nm with N2O/acetylene flame. The eluent contained 1 M HCl, 1 M HNO3 and 0.1 M NaCl. The results obtained using a calibration graph covering the range 0.5-5 mg/l Cu were in agreement with manufacturers` specifications and comparable to those obtained by direct AAS measurement. The detection limit in the food supplement was 0.015% with a 2 g sample and the RSD (n =15) was 5.74%.
Copper Spectrophotometry Preconcentration Dialysis Resin Method comparison Optimization

"Development Of A Chemiluminescence Detector With Photodiode Detection For Flow Injection Analysis And Its Application To L-lactate Analysis"
Anal. Chim. Acta 1995 Volume 316, Issue 3 Pages 323-327
Akihide Hemmia, Kaoru Yagiudaa, Naomi Funazakia, Satoshi Itoa, Yasukazu Asano*, Toshihiko Imatob, Kenji Hayashic and Isao Karubed

Abstract: A low cost chemiluminescence detector with a photodiode for flow injection analysis of L-lactate in food was developed for quality control in food industry. In this system, L-lactate is oxidized by the enzymatic reaction with L-lactate oxidase immobilized on the column to produce hydrogen peroxide. Then chemiluminescence caused by mixing hydrogen peroxide with the chemiluminescence reagent was detected by the photodiode. This light intensity was proportional to L-lactate concentration. For detecting weak chemiluminescence efficiently a flow-through cell of the detector was specially designed. A photodiode was used for the purpose of reducing the costs of FIA systems instead of a photomultiplier tube. As a result, a linear working curve was obtained from 10^-7 to 10^-3 mol L-1 L-lactate concentration. We applied the present system with a photodiode detector for food samples and compared the results with those obtained by the conventional HPLC method. The data obtained by the present FIA method were fairly in good agreement with those obtained by the conventional HPLC method. The correlation factor and regression line between both methods were 0.992 and Y= 1.07X-0.15, respectively. The present FIA system with the photodiode detector is available as a simple, easy-handling instrument for quality control in food industry. (8 References)
l-Lactate Chemiluminescence Photodiode Method comparison

"A Combined Sampling And Delay Unit For Flow Injection Analysis. The Automated Determination Of 2-thiobarbituric Acid-reactive Substances In Foods"
Anal. Chim. Acta 1996 Volume 322, Issue 1-2 Pages 69-76
S&oslash;ren Storgaard J&oslash;rgensen* and Gitte S&oslash;rensen

Abstract: A sampling and delay unit for FIA is described that permits individual samples to be retained for a specified time before being propelled to the detector. The unit consists of two discs (13 cm diameter) fitted together in the horizontal plane. Eight pairs of holes are drilled in the lower disc and a reaction coil is fitted to each pair. Two pairs of holes are drilled in the upper disc in positions that coincide with the holes in the lower disc. By rotating the lower disc with respect to the upper disc, sequential access is obtained to each reaction coil for removing the reaction mixture and recharging. The reaction coils are immersed in a water bath for temperature-controlled reactions. The unit was used for the automated determination of 2-thiobarbituric acid-reactive substances in foods, a measure of lipid oxidation. The method was based on the spectrophotometric detection at 532 nm of the red chromophore formed by reaction of 2-thiobarbituric acid with the product of lipid oxidation. The calibration graph obtained by the proposed automated method showed good correlation with that obtained by a manual method. Meat samples were analyzed by both methods and the results are compared.
2-thiobarbituric acid Spectrophotometry Heated reaction Reactor

"A Robotic-flow Injection Approach To The Fully Automated Determination Of Starch In Food"
Anal. Chim. Acta 1996 Volume 333, Issue 3 Pages 205-213
A. Velasco-Arjona and M. D. Luque de Castro*

Abstract: A focused microwave digester was used as a peripheral of a robotic station to speed up analyte hydrolysis in the colorimetric determination of starch in foods by the neocuproine method. The station was connected to a flow injection manifold that effected filtration, dilution, derivatization and spectrophotometric detection. The steps in the automated robotic FIA method are described schematically. FIA was carried out at 70°C with a 45.3 µL injection, a flow rate of 1.4 ml/min, 0.6 M NaOH, neocuproine reagent and detection at 460 nm. The robotic-FIA method was compared with manual and robotic methods in the analysis of starch in bakery products. Duplicate analyzes of three solid samples took 5 h rather than the 15 h required by the robotic station alone or the 5 h/sample taken by the manual method.
Starch Automation Robot

"Determination Of L-asparagine Using Flow Injection Systems With Spectrophotometric And Potentiometric Detection"
Anal. Chim. Acta 1996 Volume 336, Issue 1-3 Pages 113-122
Kathrin Stein*, Renbing Shi and Georg Schwedt

Abstract: Two FIA methods were developed for determining asparagine in foods. The first method was based on the catalyzed hydrolysis of asparagine by immobilized asparaginase to yield NH3. The NH3 diffused through a PTFE membrane and was detected (i) spectrophotometrically using an acid-base indicator solution as the acceptor or (ii) potentiometrically using a pH electrode and water as the acceptor. The linear ranges and RSD (n = 5) were 0.2-2.3 mM and 1.7% (at 0.75 mM asparagine), respectively, for spectrophotometric detection and 0.1-4 mM and 2.5% (at 1 mM asparagine), respectively, for potentiometric detection. The sampling frequency was 35/h. The second method used a biosensor fabricated by attaching a membrane with immobilized asparaginase on to a pH electrode. The linear range and RSD (n = 5) of this method were 0.1-2 mM and 2.3% (at 1 mM asparagine), respectively. The sampling frequency was 30/h. The methods were applied to apple and orange juice, oranges and asparagus. The sample preparation procedure involved diluting the fruit juices or filtering the homogenates of the solid foods. Recoveries of 50 mg/l or 50 mg/100 g asparagine from spiked foods were >94.3%.
l-asparagine Potentiometry Electrode Spectrophotometry Sensor Immobilized enzyme Teflon membrane Gas diffusion

"Continuous-flow Determination Of Natural And Synthetic Antioxidants In Foods By Gas Chromatography"
Anal. Chim. Acta 1998 Volume 359, Issue 1-2 Pages 47-55
M. Gonz&aacute;lez, E. Ballesteros, M. Gallego and M. Valc&aacute;rcel*

Abstract: A simple, rapid continuous-flow method with gas chromatography detection for the simultaneous determination of natural and synthetic antioxidants (α-tocopherol, α-tocopheryl acetate, 2,6-di-tert-butyl-p-hydroxytoluene, tert-butyl-4-hydroxyanisole and tert-Bu hydroquinone) is proposed. A solid phase extractor is coupled to the flow system to isolate antioxidants from the sample matrix. During extraction, analytes are released from ~70% of the triglycerides present in fats and oils by using XAD-7 sorbent; after selective elution with 400 µL of 2-propanol, only ~0.7-0.8% of total triglycerides originally present in the sample remain in the final ext. XAD-7 adsorbs 70-95% of the antioxidants except BHT of which only ~30% is adsorbed. The proposed method is considered an effective alternative to earlier procedures.
Antioxidants tert-Butylhydroxytoluene GC Solid phase extraction

"Sample Preparation In Sequential Injection Analysis. Spectrophotometric Determination Of Total Phosphorus In Food Samples"
Anal. Chim. Acta 1998 Volume 371, Issue 1 Pages 57-62
Cl&aacute;udio Celestino Oliveiraa, Elias Ayres Guidetti Zagattoa,*, Alberto N. Ara&uacute;djob and Jos&eacute; Luis F. Costa Limab

Abstract: A sequential injection (SI) procedure involving inline sample preparation is proposed. A natural suspension or a slurry is transported together with nitric acid towards a home-made digestion bomb placed inside a microwave oven for subsequent digestion. The sample zone is stopped inside the oven and, after digestion, directed in reverse flow towards a holding coil and then towards detection. This is a good strategy because the SI system is versatile; the formed air bubbles are efficiently disposed of, thus avoiding the need for a debubbler unit, and the digestion bomb acts also as a mixing device promoting easy homogenization regardless of the number of required reagents. As application, the spectrophotometric determination of total phosphorus in foodstuffs based on the molybdenum blue method was selected. The proposed system is very robust and yields reproducible measurements, (RSD usually <3%) for 20.0-400.0 mg L-1 P-PO4. Results are in agreement with a conventional spectrophotometric procedure involving manual sample digestion.
Phosphorus Spectrophotometry Sample preparation Microwave Online digestion Method comparison Sequential injection

"Simultaneous Determination Of Iron(III) And Vanadium(V) By Use Of A Kinetic - Spectrophotometric And Rapid Mixing Flow System"
Talanta 1991 Volume 38, Issue 10 Pages 1159-1162
Hong-Bin He, Yun-Xiang Ci*, Wen-Bao Chang and Wen-Ling Gong,

Abstract: Food sample (2 g) was heated with 20 mL of 67% HCO3 - 70% HClO4 (1:1) until almost dry and diluted to 25 mL with 0.01 M HCl. Sample solution was merged with chromotropic acid solution and KBrO3 with use of a pump before reaction in a flow cell and detection at 420 nm. The flow system (illustrated) employs a rapid sample and reagent introduction manifold, in which valves and carrier streams are omitted without decreasing the precision or increasing the sample consumption relative to FIA. Satisfactory results were obtained in the simultaneous determination of Fe(III) by its color reaction and VV by its catalytic effect. Calibration graphs were rectilinear from 0.15 to 15 µg mL-1 of Fe(III) and from 3 to 700 ng mL-1 of VV; corresponding coefficient of variation (n = 10) were 0.6 and 2%. Recoveries were 98% in raisins, milk powder and biscuits.
Iron(III) Vanadium(V) Spectrophotometry Catalysis Kinetic

"Online Alumininium Preconcentration On Chelating Resin And Its Flow Injection Analysis - Spectrofluorimetric Determination In Foods And Dialysis Concentrates"
Talanta 1991 Volume 38, Issue 12 Pages 1387-1392
P. Fern&aacute;ndez, C. P&eacute;rez Conde, A. Guti&eacute;rrez and C. C&aacute;mara*,

Abstract: A selective and sensitive technique whereby Al is complexed with 5,7-dibromoquinolin-8-ol and extracted into ethyl ether before separation from interferants in a chelating micro-column and spectrofluorimetric determination at 525 nm (excitation at 400 nm). Other complexes and solvent systems are considered but are found to be inferior. Batch- and flow injection methods are studied and the latter is found to be the most selective. Optimum conditions are 0.05 M acetic acid buffer of pH 5.5 with complex concentration. in ethyl ether of 0.05%, aqueous and organic flow rates of 0.36 and 0.62 mL min-1, respectively, for a 185 µL sample injection volume. The calibration graph is rectilinear from 1 to 50 ng mL-1 of Al; detection limit is 0.3 ppb Al with coefficient of variation at 4 ppb of 3%. The method is applied in dialysis fluids, foods and tap water.
Aluminum Fluorescence Chelation Column Preconcentration PPB Interferences Dialysis Resin

"Determination Of Trace Amounts Of Tin By Flow Injection Hydride-generation Atomic Absorption Spectrometry With Online Ion-exchange Separation And Preconcentration"
Talanta 1992 Volume 39, Issue 4 Pages 383-390
Zhaolun Fang and Lijing Sun, Elo H. Hansen, Jes E. Olesen and Lina M. Henriksen

Abstract: Canned food digests prepared as previously described (Dabeka et al., J. Assoc. Off. Anal. Chem., 1985 ,68, 209) were diluted with water and 2 M HCl before application at 8 mL min-1 to a Dowex 1-X8 strongly basic anion exchanger (80 to 100 mesh). Tin, as its chlorostannate complex, was eluted with 0.1 M HNO3 into a hydride-generation manifold and merged with NaBH4 reductant solution containing 0.05 M NaOH (both streams at 11 mL min-1). The stannane formed was stripped from solution by Ar (90 mL min-1) and passed with evolved H to a gas-liquid separator before analysis by AAS. For a 2.7 mL sample the analyte enrichment factor was 3.5 and the detection limit was 0.08 µg L-1 at a sampling rate of 72 h-1. The coefficient of variation was 2.5% at the 10 µg L-1 level and recoveries were from 94 to 102%. Potential interferents could be tolerated in 1000-fold excess, however a 100 to 1000-fold excess of Cu(II) decreased the signal by 10 to 15%. A hydride generation atomic absorption spectrometric (AAS) method with flow injection (FI), aimed at developing a practical routine assay for the determination of tin in food digests, is described. In order to modify the sample matrix and to achieve optimized and reproducible conditions for the hydride generation reaction, the analyte is initially converted into its chlorostannate complex, thereby allowing it to be separated and pre-concentrated online on an incorporated micro-column packed with a strongly basic anion-exchanger and subsequently to be eluted by diluted nitric acid under strictly controlled conditions. Optimum acidic conditions for the FI hydride generation AAS system were given by 0.01-0.5 M nitric acid. At a consumption of 2.7 mL sample volume, aspirated by time-based injection, the procedure resulted in an enrichment factor of 3.5 and yielded a detection limit of 0.08 µg/L (3s) at a sampling frequency of 72/h. The precision was 2.5% rsd at the 10 µg/L level. Potential interferents, such as Ni(II), Co(II), Zn(III) could, at a Sn level of 10 µg/L, be tolerated at an excess of 1000 times without impairing the assay, while a 100-1000-fold excess of Cu(II) decreased the signal by 10^-15%. Recoveries in the range of 94-102% were obtained for canned food sample digests spiked with 10 µg/L Sn.
Tin Ion exchange Sample preparation Spectrophotometry Preconcentration Volatile generation Phase separator Optimization Timed injection Interferences Volatile generation

"Fluorimetric Determination Of Nitrite"
Talanta 1993 Volume 40, Issue 7 Pages 1009-1011
Nianqin Jie, Jinghe Yang and Fanqin Meng,

Abstract: A sensitive and rapid fluorimetric method for the determination of nitrite is described. The method is based on the reaction of nitrite with tryptophan to form a highly fluorescent compound in alkaline medium. The method has been applied in the determination of nitrite in water and food samples. [References: 16]
Nitrite Fluorescence

"Immobilization Of Glutamate Dehydrogenase On Glass Derivatives: A Method For The Assay Of Glutamates In Real Samples With Simplex Optimized Automated FIA-system"
Talanta 1994 Volume 41, Issue 9 Pages 1561-1567
Constantine D. Stalikas, Miltiades I. Karayannis and Stella Tzouwara-Karayanni*

Abstract: An enzymatic method for the determination of glutamic acid in food samples and pharmaceuticals is described. -Glutamate dehydrogenase (GLDH) from beef liver was immobilized on isothiocyanate modified Controlled Pore Glass for the construction of a packed bed reactor. The NADH produced from the enzymatic reaction was monitored fluorimetrically. The working curve is linear up to 200 mol/l glutamate for an injection volume of 58 l. The detection limit of the method is 0.3 mol/l. The composite modified simplex was employed for the selection of the proper experimental conditions using an in-house flow injection manifold. Many interfering species and several amino acids were tested to verify the specificity of the enzyme reactor. The system works selectively for glutamic acid. The method is ideally suited to the assay of glutamic acid in a large number of samples because of its simplicity, stability and low cost. Forty-five samples per hour can be analyzed with a relative standard deviation better than 2%. The reactor is stable for a period of more than four months under specified storage conditions. The accuracy of the proposed method is tested by comparison of the results with those obtained by the official methods and the manufacturer's specifications for the analyzed samples. Good correlation was attained. Recovery experiments showed results between 97 and 104%.
Glutamate Immobilized enzyme Simplex Optimization Glass

"Amperometric Detection Of Uric Acid And Hypoxanthine With Xanthine Oxidase Immobilized And Carbon Based Screen-printed Electrode"
Talanta 1997 Volume 44, Issue 11 Pages 2151-2159
M-A. Carsol, G. Volpe and M. Mascini*

Abstract: Carbon-based screen-printed electrodes are suitable for uric acid detection. Xanthine oxidase (XO) was immobilized either directly on the surface of the electrode or in a reactor with CPG aminopropylsilane in a FIA assembly. Higher reproducibility and lifetime was obtained with the reactor. Optimum conditions were found for the determination of Hypoxanthine (Hx), Inosine (HxR) and Inosine monophosphate (IMP). Calibration curves for IMP, HxR and Hx are linear up to 50 µM with detection limit of 1 µM for 50 µl injection. One assay is completed within 30 s. The reproducibility of 20 µM of Hx was obtained with CV 2%.
Uric acid Hypoxanthine Electrode Electrode Amperometry Immobilized enzyme Controlled pore glass Optical isomers

"Amperometric Enzyme Electrode System For The Flow Injection Analysis Of Glucose"
Analyst 1986 Volume 111, Issue 6 Pages 605-609
G. J. Moody, G. S. Sanghera and J. D. R. Thomas

Abstract: An amperometric glucose sensor constructed by immobilization of glucose oxidase on nylon net, essentially as described by Mascini et al., (cf. Anal. Abstr., 1983, 45, 2J175), was used as the anode in a flow-through cell, which was also equipped with a vitreous-carbon auxiliary electrode and a silver - AgCl reference electrode. Sample solution (500 µL) were injected into a 0.1 M phosphate buffer (pH 7) carrier stream (2.3 mL min-1), and the H2O2 produced by oxidation of the glucose at the electrode surface was determined at +600 mV. Calibration graphs were rectilinear (log. - log. scale) in the range 0.025 to 2 mM, and at the 2.5 and 5.0 mM levels the coefficient of variation were 1.3 and 2.9%, respectively (n = 10). Interference from a 10-fold excess (relative to glucose) of galactose, maltose, arabinose, fructose, sucrose, lactose or saccharin was relatively small. Results obtained for various foods agreed with those obtained by an enzyme test kit or an instrumental glucose analyzer.. Membranes were stable for up to 4 months when stored in buffer solution at 4°C.
Glucose Amperometry Electrode Immobilized enzyme Interferences

"Flow-through Multi-enzyme Electrodes For The Determination Of Lactose"
Analyst 1989 Volume 114, Issue 12 Pages 1587-1592
Junainah Abdul Hamid, G. J. Moody and J. D. R. Thomas

Abstract: One-, two-, three- and four-enzyme electrodes were made by immobilizing β-galactosidase, aldose 1-epimerase, glucose oxidase and galactose oxidase in six combinations on nylon netting (cf. Moody et. al., Ibid., 1986, 111, 605) that was fixed over a Pt indicator electrode for use in a flow injection system, and lactose was determined amperometrically by detecting the produced H2O2 at 0.6 V vs. Ag - AgCl. The best combination comprised the first three of the cited enzymes; the electrode showed good response and rectilinear range (3 µM to 2 mM lactose), short response times (15 to 20 s), and only a 5% reduction in signal after 18 h in a continuous-flow of 1 mM lactose. Glucose present in food samples was determined independently with a glucose electrode.
Lactose Electrode Electrode Amperometry Immobilized enzyme Nylon

"Enzymic Determination Of Ammonia In Food By Flow Injection"
Analyst 1990 Volume 115, Issue 9 Pages 1243-1246
Lucia Canale-Gutierrez, Angel Maquieira and Rosa Puchades

Abstract: Ammonia in food samples was determined by its reaction in an immobilized enzyme reactor containing glutamate dehydrogenase (GIDH) in a flow injection system, by measuring the decrease in the absorbance of ultraviolet radiation by reduced nicotinamide adenine dinucleotide (NADH). There was a linear relationship (r = 0.9995) between peak height and ammonia concentration over the range 0.05-0.6 mM. The detection limit was 0.005 mM for an injection volume of 19 µL. Sampling frequency was 60 h-1 and the precision was better than 1.09% for 11 successive assays. The interference effect of urea and ascorbic acid at concentrations greater than 100 mg per 100 g of product should be taken into account. The interference caused by glycine, creatinine and amino acids is negligible. Only a 20% loss in the activity of the GIDH column was observed after 500 determinations during a 3-month period. Samples were extracted by a modification of the method of Parris and Foglia (Anal. Abstr., 1984, 46, 1F8). The extract was mixed with a carrier stream of 0.1 M phosphate buffer (pH 8), containing 1 mM EDTA, 0.2 mM NADH and 0.1 M oxoglutarate and was passed into a reactor containing immobilized glutamate dehydrogenase and the decrease in the absorbance was measured at 340 nm. The response was rectilinear from 0.05 to 0.6 mM of NH4+ with a limit of detection of 5 µM for a 19 µL injection. The coefficient of variation (n = 11) for 0.25 mM was 1.09%. Urea and ascorbic acid interfered significantly at concentration. >1000 ppm.
Ammonia Immobilized enzyme Interferences Activity Detection limit

"Automated Enzyme Packed-bed System For The Determination Of Vitamin C In Foodstuffs"
Analyst 1991 Volume 116, Issue 6 Pages 569-572
Simon Daily, Susan J. Armfield, Barry G. D. Haggett and Mark E. A. Downs

Abstract: A microprocessor controlled flow injection system is described for the determination of vitamin C in foodstuffs. The system is based on amperometric detection at a wall-jet electrode coupled with an ascorbate oxidase packed bed. A commercially available Cartesian robotic auto-sampler-dilutor is used as a means of fully automating the sample handling and dilution. Dithiothreitol (DTT) is used to reduce dehydroascorbic acid to ascorbic acid and to stabilize ascorbic acid standard solutions. Initially, the system was connected in series with a high performance liquid chromatography column and ultraviolet (UV) detector to allow identification of possible interferents and to allow comparative evaluation of results. The system showed a linear response to the concentration of L-ascorbic acid in the range 1-200 µg mL-1 and was capable of detecting total vitamin C in a range of foodstuffs at a sample throughput of 15 samples h-1. Correlations to existing methods of 0.98 were obtained.
Ascorbic acid Amperometry HPLC Spectrophotometry Automation Immobilized enzyme Interferences Robot

"Immobilization Of Glutamate Oxidase On Non-porous Glass Beads. Automated Flow Injection System For The Assay Of Glutamic Acid In Food Samples And Pharmaceuticals"
Analyst 1993 Volume 118, Issue 6 Pages 723-726
Constantine D. Stalikas, Miltiades I. Karayannis and Stella M. Tzouwara-Karayanni

Abstract: The assay involved the immobilization of glutamate oxidase on non-porous glass beads for the construction of single-bead string reactors (SBSR). The Trinder reaction was used for the entrapment of the H2O2 generated by the enzymatic reaction. The flow injection system consisted of a four-way pneumatically actuated injection valve, an eight-channel peristaltic pump and a filter spectrophotometer equipped with a fiber optic for the transmission of the light from the source to the flow-through cell for measurement. The sample solution containing glutamic acid (I) or glutamate was injected into the carrier stream (phosphate buffer, pH 7.8) and flowed through the SBSR with the immobilized enzyme in a 0.8-mm Teflon tube. The H2O2 was mixed with Trinder's reagent in phosphate buffer and proceeded through a second reactor with untreated glass beads. Detection was at 510 nm. The calibration graph was rectilinear from 10 to 500 µM-Iand the coefficient of variation (n = 6) was 1.8%. The detection limit was 5 µM-I. Recoveries ranged from 97 to 105%.
Glutamic acid Spectrophotometry Immobilized enzyme Glass beads Single bead string reactor

"Flow Injection Chemiluminescence Method For The Selective Determination Of Chromium(III)"
Analyst 1993 Volume 118, Issue 6 Pages 643-647
Rosario Escobar, Qingxiong Lin, Alfonso Guira&uacute;m and Francisco F. de la Rosa

Abstract: The cited determination was based on the measurement of light emitted from the Cr(III)-catalyzed oxidation of luminol by H2O2. The flow cell of the flow injection system was a coiled PTFE tube (1 mm i.d.). Luminol and H2O2 were dissolved in 0.2 M CO32- - HCO3- buffer. Luminol and H2O2 were mixed in the flow system and then with the flow of water in which the sample was injected. The chemiluminescence was recorded as a function of time over 5 s. The max. emission intensity was proportional to the Cr(III) concentration. in the sample. The addition of 0.1 mM EDTA reduced interference from other metal cations. The calibration graph was rectilinear from 0.01 (detection limit) to 6 ppb of Cr(III). The cited method was applied in the determination of Cr(III) in water and food. Recoveries ranged from 96 to 110% and 92 to 108.5% in food and water samples, respectively. The coefficient of variation (n = 15) was 2.5%.; the method can analyze up to 70 samples h-1.
Chromium(III) Chemiluminescence Interferences

"Photokinetic Determination Of Riboflavin And Riboflavin 5'-phosphate Using Flow Injection Analysis And Chemiluminescence Detection"
Analyst 1994 Volume 119, Issue 8 Pages 1825-1828
Tom&aacute;s P&eacute;rez-Ruiz, Carmen Mart&iacute;nez-Lozano, Antonio Sanz and Virginia Tom&aacute;s

Abstract: In a photolysis cell were placed 2 mL of 0.1 M phosphate buffer of pH 6, 1 mL of 0.1 M EDTA, 1 mL of 1.8 µM-iron(III) ammonium sulfate, 1 mL of 0.5 mM H2O2 and an appropriate volume of sample solution to yield a final riboflavin or riboflavin 5'-phosphate concentration of 0.1-5 µM. The solution was diluted to 10 mL with water and irradiated for 60 s at 25°C. A 35 µL portion of the photolysed solution was injected into a carrier stream (1.7 ml/min) of 1 M phosphate buffer of pH 12 and mixed with a reagent stream (1.7 ml/min) containing 0.1 mM luminol and 3 µM-haematin. The mixture was transported to a flow cell and the light emitted from the chemiluminescence reaction was measured. Diagrams of the photolysis cell and flow injection manifold used are given. The calibration graph was linear from 0.1-3 µM-riboflavin and riboflavin 5'-phosphate. RSD (n = 10) were 0.9-1.3%. The method was applied to animal tissues, foods and pharmaceuticals.
Chemiluminescence Kinetic Photochemistry

"Organic-phase Enzyme Biosensor For Moisture Determination In Food Products"
Analyst 1994 Volume 119, Issue 9 Pages 2001-2003
Saverio Mannino, Maria Stella Cosio and Joseph Wang

Abstract: The cited biosensor was prepared by mixing 5 mg tyrosinase with 300 mg ceresin paste. The cavity of the working electrode was filled with the resulting paste and the surface was smoothed. The electrode was used in a flow injection system to determine moisture in several foods. Butter and margarine were diluted 50-fold with acetonitrile. Biscuits, orangeade and chicken soup were lyophilized, diluted 10- or 20-fold with acetonitrile and filtered. A portion (50 µL) of the sample solution was injected into a carrier stream (0.7 ml/min) of 0.5 mM catechol in acetonitrile and transported to the biosensor. The amount of moisture present was determined amperometrically by applying a potential of -250 mV vs. Ag/AgCl to the biosensor, and measuring the current produced. The calibration graph was linear from 0.1-1% of H2O; the detection limit was 0.072%. The RSD (n = 7) was 3.2% and the throughput was 50 samples/h. The results obtained agreed with those obtained by official methods.
Water Sensor Electrode Amperometry

"Assessment Of Quality Of Flow Injection Methods Used In Food Analysis"
Analyst 1995 Volume 120, Issue 9 Pages 2393-2400
J. M. L&oacute;pez-Fern&aacute;ndez, A. R&iacute;os and M. Valc&aacute;rcel

Abstract: A review is presented of the quality of flow injection (FI) methods used in food analysis. Over 200 FI methods are evaluated for quality in terms of accuracy, applicability, precision, selectivity, sensitivity, determination range and sample throughput. A quality scale is proposed that enables the most appropriate method to be chosen for a given type of food analysis. (129 references).
Review Linear dynamic range Selectivity Sensitivity Quality

"Flow Injection Methods For Determination Of L-glutamate Using Glutamate Decarboxylase And Glutamate Dehydrogenase Reactors With Spectrophotometric Detection"
Analyst 1996 Volume 121, Issue 9 Pages 1305-1309
Renbing Shi and Kathrin Stein

Abstract: Three flow injection methods for glutamate determination are described. In method A, glutamate was passed through a reactor containing immobilized glutamate decarboxylase. The CO2 produced diffused through a Teflon membrane into an acid-base indicator acceptor solution and was determined spectrophotometrically at 430 nm. In method B, glutamate was mixed with NAD+ and reacted with immobilized glutamate dehydrogenase. The NADH formed was measured spectrophotometrically at 340 nm. Method C was similar to method B, except that the stopped-flow approach was used in order to reduce the consumption of NAD+. The calibration graphs were linear for 2-20, for 0.05-0.6 and for 0.2-1 mM glutamate for methods A, B and C, respectively. The RSD (n = 5) were 1.9-2.8%. Recoveries of glutamate were 95-101%. The throughput was 30 samples/h for all three methods. The methods were applied to various foods.
Glutamate Spectrophotometry Stopped-flow Manifold comparison Teflon membrane Immobilized enzyme

"Application Of Oscillating-reaction-based Determinations To The Analysis Of Real Samples"
Analyst 1997 Volume 122, Issue 3 Pages 287-292
Rafael Jim&eacute;nez-Prieto, Manuel Silva and Dolores P&eacute;rez-Bendito

Abstract: The use of an oscillating reaction involving the H2O2/NaSCN/CuSO4 system in an alkaline medium for the continuous-flow analysis of real samples by the analyte pulse perturbation technique is described. The method involves the addition of small amounts of the analyte to the oscillating system and measuring the changes in the oscillation amplitude and/or oscillation period produced. The method was applied to the determination of vanillin (I) in food, paracetamol (II) in pharmaceuticals, and ascorbic acid (III) in orange juice and pharmaceuticals. The calibration graphs were linear from 1-40, 0.5-6 and 0.5-5 µmol I, II and III, respectively. RSD were n = 11). Sample throughput was 6-10 samples/h.
Acetaminophen Ascorbic acid Vanillin Spectrophotometry Oscillating chemical reaction Indirect

"Amperometric Bienzymic Sensor For Aspartame"
Analyst 1997 Volume 122, Issue 5 Pages 487-490
D. Compagnone, D. O'Sullivan and G. G. Guilbault

Abstract: The cited sensor was fabricated by covalent immobilization of alcohol oxidase and α-chymotrypsin on to a polycarbonate membrane via glutaraldehyde. A cellulose acetate membrane was applied over the immobilized enzymes and used to attach the assembly to the surface of a Pt electrode. Amperometric measurements of aspartame (I) were performed in 0.1 M phosphate buffer of pH 7.5 with the Pt electrode polarized at +650 mV vs. Ag/AgCl. Calibration graphs were linear from 1-750 µM I using batch and flow-through methods, and up to 1 mM I using a flow injection method. Detection limits were 0.2-1 µM; RSD were 1.8-4% (n = 10). Different strategies for eliminating interfering compounds, including the use of an additional alcohol oxidase/catalase membrane and signal subtraction using an alcohol electrode, were employed. The sensor was applied to various foods; recoveries were 95-106%. An amperometric enzyme electrode for the determination of aspartame was developed by covalent immobilization of alcohol oxidase and α-chymotrypsin. A platinum based hydrogen peroxide electrode was used as the detector. Excellent sensitivity was obtained using batch, flow-through and flow injection methods with detection limits of 2 x 10^-7, 4 x 10^-7 and 10^-6 mol L-1, respectively. Different strategies for eliminating interfering compounds, including the introduction of an additional alcohol oxidase-catalase membrane and signal subtraction using an alcohol electrode, were employed. A recovery study on seven food samples was carried out and the results were satisfactory.
Aspartame Amperometry Sensor Electrode Electrode Interferences Immobilized enzyme Polycarbonate membrane Cellulose acetate

"Selective Fluorescent Chemosensor For Fructose"
Analyst 1998 Volume 123, Issue 1 Pages 155-158
G. Pina Luis, M. Granda, R. Bad&iacute;a and Marta Elena D&iacute;az-Garc&iacute;a

Abstract: A chemosensing system for the selective recognition of fructose based on a reverse photoinduced electron transfer process was developed. A fluorescent boronic acid, m-dansylaminophenylboronic acid, reacts with fructose to produce an electron transfer, which results in the fluorescence quenching of the dye. The addition of the sugar shifted the pKa from 8.13 to 7.80. A possible sensing mechanism is proposed. The anal. figures determined in a batch approach were detection limit 5 x 10^-6 M, repeatability of 1% at the 1 x 1004 M fructose level and linear calibration up to 3 x 10^-4 M. A flow injection system was also examined and after the experimental conditions had been optimized a selectivity study showed that only galactose (at a 1:2 fructose to galactose molar ratio) gave apositive deviation. Several food samples were analyzed by the proposed flow injection procedure and the results agreed with those obtained using an enzymatic kit for food anal.
Fructose Fluorescence Quenching Method comparison Optimization

"Speciation Analysis Of Chromium(III) And Chromium(VI) Using Flow Injection Analysis With Fluorometric Detection"
Analyst 1998 Volume 123, Issue 5 Pages 1005-1009
Evangelos K. Paleologos, Spyros I. Lafis, Stella M. Tzouwara-Karayanni and Miltiades I. Karayannis

Abstract: A relatively simple, sensitive, selective, automatic fluorometric method for the simultaneous determination of Cr(III) and Cr(VI) by flow injection analysis (FIA) was developed. The method is based on the selective oxidation of the nonfluorescing reagent 2-(α-pyridyl)thioquinaldinamide (PTQA), which with Cr(VI) yields an intensely fluorescent product (λex = 360 nm; λem = 500 nm). Cr(III) is oxidized online to Cr(VI) with sodium metaperiodate and the Cr(VI) is subsequently treated with PTQA. Fluorescence due to the sum of Cr(III) and Cr(VI) is measured and Cr(III) is determined from the difference in fluorescence values. The effects of various anal. parameters, such as acidity, flow rate, sample volume, temperature, reagent concentration and interfering species, were studied. Kinetic studies using both the stopped-flow technique and the FIA procedure were used to study and optimize the oxidation conditions for Cr(III) from its oxidation efficiency. The calibration graphs were rectilinear in the ranges 0.1-10 µg mL-1 for Cr(VI) and 0.1-1.0 µg mL-1 for Cr(III). The method was successfully verified by performing recovery experiments of Cr in several standard reference materials (peach leaves, sediments and tea), and it was applied to the speciation analysis of Cr(III)-Cr(VI) in environmental waters (mineral, tap and distilled water), a food sample (tomato juice) and synthetic mixtures. Up to 30 samples per h can be analyzed with a relative standard deviation of ~0.1-2%.
Chromium(III) Chromium(VI) Fluorescence Speciation Stopped-flow Kinetic Reference material Indirect Interferences Optimization

"Sample Analysis By Online Isotope-dilution Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 8 Pages 761-766
Alexandra L&aacute;sztity, Mikl&oacute;s Viczi&aacute;n, Xioaru Wang and Ramon M. Barnes

Abstract: A system for online isotope-dilution ICP-MS was developed by coupling commercial flow injection instruments with an ICP-MS instrument. The performance of the system was investigated by determination of Pb in various standard reference materials (including soil, sediment, paint, blood and food), with dilution with 206Pb or radiogenic Pb isotope standards. Both steady-state merging and multiple injections were employed, the former being preferred, the precision was 1%.
Lead Mass spectrometry Mass spectrometry Reference material

"Inductively Coupled Plasma Spectrometry In The Study Of Childhood Soil Ingestion. 2. Methodology"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 8 Pages 727-735
Xioaru Wang, Alexandra L&aacute;sztity, Mikl&oacute;s Viczi&aacute;n, Yescheskel Israel and Ramon M. Barnes

Abstract: In a study aimed at quantifying the amount of soil ingested by infants and toddlers, faeces and urine collected in commodes or on diapers, together with home and pre-school dust, soil and food samples, were analyzed for Al, Ba, Mn, Si, Ti, V, Y and Zr by ICP-AES with multi-channel and sequential instruments, and V, Y and Zr were also determined by ICP-MS with flow injection sample introduction. Protocols are described for sample prep., and for online dilution and calibration for ICP-MS. Results obtained on standard solution and on reference soil and dust were in good agreement with certified or recommended values, and results by ICP-AES and ICP-MS were not statistically different, although those by ICP-MS were more precise. Flow injection ICP-MS is recommended for determining V, Y and Zr, which are present at low concentration.
Aluminum Barium Manganese Silicon Titanium Yttrium Sample preparation Spectrophotometry Mass spectrometry Reference material

"Atomic Spectrometry Update: Clinical And Biological Materials, Foods And Beverages"
J. Anal. At. Spectrom. 1991 Volume 6, Issue 3 Pages 69R-107R
Simon Branch, Helen M. Crews, David J. Halls and Andrew Taylor

Abstract: This Update contains reviews on recent developments in the application of atomic spectrometry to the analysis of clinical and biological materials and of foods and beverages. These two reviews cover the references 90/1159-90/4166 and 91/1-91/825 which are listed fully as Atomic Spectrometry Update References in Volumes 5 and 6 of JAAS, respectively. A list of references to published papers in abbreviated form appears at the end of this Update. The Tables, in an improved format, summarise the methods and studies covered in these reviews. Last year's Update (J. Anal. Atomic Spectrom., 1990, 5, 75R) covered developments in the preceding year.
Fluorescence Mass spectrometry Spectrophotometry Voltammetry Clinical analysis Review Supercritical fluid Reference material Principal component analysis

"Repetitive Determinations Of Amylase, Maltose, Sucrose And Lactose By Sample Injection In Closed Flow-through Systems"
Anal. Chem. 1978 Volume 50, Issue 12 Pages 1665-1670
D. P. Nikolelis and Horacio A. Mottola

Abstract: Conditions have been developed for the repetitive determination of amylase and some disaccharides by coupling enzyme-catalyzed reactions yielding glucose as a product with the glucose oxidase catalyzed oxidation of this sugar. Determinations have been performed by sample injection into a continuously circulated reagent mixture and monitoring of oxygen depletion with a three-electrode amperometric system. Maltose, sucrose, and lactose in the range of 50 to 500 mg/100 mL, 10 to 250 mg/100 mL, and 25 to 250 mg/100 mL, respectively, and amylase in the range of 50 to 500 units/100 mL have been determined with relative errors and relative standard deviations (population) of about 2%. The maximum determination rate is 240 injections/h for maltose, 700 injections/h for sucrose and lactose; and 120 injections/h for amylase at room temperature. Applications to real samples (a variety of food products, human blood serum, and serum calibration references and controls) are reported.
Disaccharides α-Amylase Maltose Sucrose Lactose Clinical analysis Electrode Closed loop

"Automated Multiple Flow Injection Analysis For Flame Atomic Absorption Spectrometry"
Anal. Chem. 1979 Volume 51, Issue 8 Pages 1201-1205
Wayne R. Wolf and Kent K. Stewart

Abstract: Nonsegmented continuous-flow analysis, termed flow injection analysis (FIA), was adapted for the automation of sample introduction in flame atomic spectroscopy. Automated multiple flow injection analysis (AMFIA) entails insertion of discrete µvolumes of liquid sample into a constantly flowing solvent stream which is pumped directly into the nebulizer of an atomic absorption spectrometer. This allows analysis of discrete µvolume samples (25-300 µL), with high precision (2% relative standard deviation), low detection limits (3 ng for Zn and 4 ng for Cu) and speed of analysis (120-80 samples/h). Identical results are obtained for Zn and Cu content of food digests and NBS Standard Reference Materials with the AMFIA system and anal. by direct aspiration of the same sample solutions.
Copper Zinc Sample preparation Spectrophotometry Automation Method comparison Reference material

"Automated Determination Of Arsenic And Selenium By Atomic Absorption Spectrometry With Hydride Generation"
Anal. Chem. 1984 Volume 56, Issue 12 Pages 2059-2063
Hisatake Narasaki and Masahiko Ikeda

Abstract: Hydrides are evolved in a Pyrex mixing tube (15 cm x 2 mm), collected in a gas - liquid separator up to an appropriate pressure, and then swept automatically into an a.a.s. furnace. Consumption of reagents is minimized. Introduction of trace water into the furnace prevents any decrease in sensitivity. The sensitivities for As(V) and Se(IV) were 0.01 and 0.004 absorbance unit per ng, respectively. Recoveries were quantitative when samples were pre-treated with Chelex 100 resin to remove interfering species. Biological standard reference materials (decomposed initially by HNO3, H2SO4 and HClO4) and river water samples were analyzed for As and Se; the water samples taken were 25 to 50 mL and 250 to 500 ml, respectively.
Arsenic Selenium Spectrophotometry Chelex Interferences Reference material Phase separator

"Simultaneous Determination Of Glucose, Fructose, And Sucrose In Mixtures By Amperometric Flow Injection Analysis With Immobilized Enzyme Reactors"
Anal. Chem. 1988 Volume 60, Issue 2 Pages 147-151
Kiyoshi Matsumoto, Hideaki Kamikado, Hiroaki Matsubara, and Yutaka Osajima

Abstract: The flow injection system (described) incorporated three immobilized-enzyme reactors (prep. described), one each for glucose(I), fructose(II) and sucrose(III), in parallel, a I-eliminating enzyme reactor (placed in series with the III reactor), and a multi-channel flow-through amperometric detector. Sample solution was injected into the system by an injection valve and into each of the three carrier streams by valve switching. For I determination, the carrier stream was 0.1 M phosphate buffer (pH 6.0), the reactor contained immobilized I oxidase, and the H2O2 produced was determined at +0.65 V vs. Ag - AgCl. For II determination, the carrier stream was McIlvaine buffer (pH 5.0) containing 6 mM K3Fe(CN)6 and 0.1% of Triton X-100, the reactor contained immobilized II 5-dehydrogenase, and the Fe(CN)64- formed was determined at +0.385 V vs. Ag - AgCl. For III determination, the carrier stream was 0.1 M phosphate buffer (pH 7.0), the reactor contained immobilized β-fructofuranosidase, aldose 1-epimerase and I oxidase, and the H2O2 formed was determined as before. The coefficient of variation (n = 10) for 1 mM I, -II and -III were 1.8, 1.8 and 1.6%, respectively. Calibration graphs (response vs. concentration.) were rectilinear from 0.02 to 1 mM for I, II and III. The method was applied to food samples.
Glucose Fructose Sucrose Amperometry Immobilized enzyme Multicomponent Triton X Valve Surfactant

"Online Preconcentration And Volatilization Of Iodine For Inductively Coupled Plasma Atomic-emission Spectrometry"
Anal. Chem. 1991 Volume 63, Issue 21 Pages 2539-2542
Scott P. Dolan, Scott A. Sinex, Stephen G. Capar, Akbar Montaser, and Robert H. Clifford

Abstract: The limit of detection for iodine in ICP-AES is 154 µg mL-1, too high to be of use in food analysis. Conversion of I- (and IO3-) to I2 before nebulization increased the transport efficiency and hence the sensitivity. Oxidation to I2 was achieved online by mixing the acidified test solution with H2O2. The signal at 183.04 nm was enhanced by a factor of 33 for an Ar ICP and of 100 for a He ICP, with sensitivities of 5 and 9 ng mL-1, respectively. In the flow injection mode, I- and IO3- were adsorbed on a membrane disc containing AG1-X8 anion-exchange resin. The membrane was washed and the anions were eluted with 4 M HNO3, with simultaneous oxidation to I2. The detection limit for I- was thereby improved to 0.75 ng mL-1. A further improvement by a factor of 8 is required to match the sensitivity of the current spectrophotometric method.
Iodine Spectrophotometry Detection limit Resin Preconcentration

"Aqueous Nitrite Ion Determination By Selective Reduction And Gas Phase Nitric Oxide Chemiluminescence"
Anal. Chem. 1995 Volume 67, Issue 1 Pages 220-224
Andrew J. Dunham, Robert M. Barkley, and Robert E. Sievers

Abstract: An improved method of flow injection analysis for aqueous nitrite ion exploits the sensitivity and selectivity of the nitric oxide (NO) chemiluminescence detector. Trace analysis of nitrite ion in a small sample (5-160 ml) is accomplished by conversion of nitrite ion to NO by aqueous iodide in acid. The resulting NO is transported to the gas phase through a semipermeable membrane and subsequently detected by monitoring the photoemission of the reaction between NO and ozone (O3). Chemiluminescence detection is selective for measurement of NO, and, since the detection occurs in the gas-phase, neither sample coloration nor turbidity interfere. The detection limit for a 100 mL sample is 0.04 ppb of nitrite ion. The precision at the 10 ppb level is 2 relative standard deviation, and 60-180 samples can be analyzed per hour. Samples of human saliva and food extracts were analyzed; the results from a standard colorimetric measurement are compared with those from the new chemiluminescence method in order to further validate the latter method. A high degree of selectivity is obtained due to the three discriminating steps in the process: (1) the nitrite ion to NO conversion conditions are virtually specific for nitrite ion, (2) only volatile products of the conversion will be swept to the gas phase (avoiding turbidity or color in spectrophotometric methods), and (3) the NO chemiluminescence detector selectively detects the emission from the NO + O3 reaction. The method is free of interferences, offers detection limits of low parts per billion of nitrite ion, and allows the analysis of up to 180 mL-sized samples per hour, with little sample preparation and no chromatographic separation. Much smaller samples can be analyzed by this method than in previously reported batch analysis methods, which typically require 5 mL or more of sample and often need chromatographic separations as well. Copyright 1995, American Chemical Society.
Nitrite Chemiluminescence Sample preparation Method comparison Indirect Interferences PPB

"Application Of Flow Injection Techniques For The Analysis Of Inorganic Anions"
Fresenius J. Anal. Chem. 1985 Volume 320, Issue 5 Pages 451-456
J. M&ouml;ller and B. Winter

Abstract: A review is presented, with 113 references. Some improvements in the determination of sulfur anions by flow injection analysis are also described. A survey of applications of flow injection analysis for the analysis of inorganic anions is given in form of a table. The turbidimetric determination of sulphate is improved by the intermittent addition of a wash solution via a separate pump. A comparison of results for the determination of sulphate in surface waters using the barium-methylthymol blue method and ion-chromatography shows good agreement. For the determination of sulphite a gas-diffusion technique is used. The method allows 90 injections/h and shows good reproducibility, 1% RSD for consecutive injections of standards at the 10 mg/l SO2-level. As the sample line is physically separated from the detection line, the method is insensitive to matrix effects from colored or turbid samples. Results for the determination of free and total sulphite in wine, beer and fruit juices are given.
Anions Sulfur compounds Sulfate Sulfite Spectrophotometry Gas diffusion Intermittent pumping Review Tecator

"Determination Of Vitamin B1 In Food By High Performance Liquid Chromatography And Post-column Derivatization"
Fresenius J. Anal. Chem. 1992 Volume 343, Issue 1 Pages 155-156
A. Bognar

Abstract: Food was heated with 0.1 M H2SO4 at 120°C for 30 min followed by hydrolysis with Taka diastase at pH 5 and 45°C for 15 h. The solution was analyzed on a column (12.5 cm x 4 mm) of LiChrospher RP 18 (5 µm) with aqueous 33% methanol containing 0.1% hexanesulfonic acid, pH 3.6, as mobile phase (1.5 mL min-1). Detection was by post-column derivatization with 0.04% K3[Fe(CN)6] in 1.5% NaOH and fluorimetric measurement at 425 nm (excitation at 370 nm). The calibration graph was rectilinear between 40 and 400 ng mL-1 with recoveries of added thiamine between 98 and 100%. The coefficient of variation (n = 3) were 1 to 10%. By using another detector at 525 nm (excitation at 467 nm) before derivatization, vitamin B2 could be simultaneously determined.
Vitamin B1 Vitamin B2 Sample preparation HPLC Fluorescence Post-column derivatization Simultaneous analysis

"Microbiological Assay For Chemical Species Of Selenium In Foods Utilizing Escherichia Coli Formate Dehydrogenase"
Fresenius J. Anal. Chem. 1993 Volume 345, Issue 2-4 Pages 243-246
Elizabeth Tschursin and Wayne R. Wolf

Abstract: The assay method depends on the fact that the formate dehydrogenases present in E. coli depend on the presence of Se for their synthesis. Samples were mixed with a minimal medium and incubated at 37°C for 22 or 32 h, depending on the cell strain, and the CO2 evolved was determined with an IR analyzer.. Dose response curves for selenite, selenocystine and selenomethionine showed sensitivities down to the pmol mg-1 range. A wheat gluten reference sample (NIST 8418) was hydrolyzed with 6 M HCl and was fractionated on an AG 50 W-X8 column; the hydrolysate was eluted with Li+ buffers of pH 2.2, 7.5 and 13. The pH 7.5 fraction was analyzed for amino-acids on a cation-exchange column, with post-column derivatization with o-phthalaldehyde and fluorescence detection. This fraction was also tested in the bioassay. Analysis for selenomethionine (I; the main Se compound in gluten) was complicated by a matrix effect by the much more abundant methionine and possible interference by seleno-cystine, which is more sensitive in the assay. These problems must be overcome before I can be determined in foods and reference materials.
Selenium Selenomethionine Fluorescence Post-column derivatization Reference material Interferences

"Biocatalysis And Biorecognition In Nonaqueous Media. Some Perspectives In Analytical Biochemistry"
Microchim. Acta 1995 Volume 120, Issue 1-4 Pages 231-242
Lorenzo Braco

Abstract: A review is presented. The basic principles and advantages of non-aqueous enzymology are outlined and its analytical applications are discussed with reference to batch analysis in organic media, flow injection enzyme reactors operating in organic media, organic-phase enzyme electrodes and enzyme-based gas-phase biosensors. Analytical applications of antibodies and abzymes in non-aqueous media are discussed and the potential of molecular imprinting techniques to generate specific recognition systems is considered. (56 references). Biocatalysis and, to a lesser extent, biorecognition in non-aqueous media (including organic solvents as well as supercritical fluids and gases) constitute at present an exciting research area which has already demonstrated its biotechnological potential in numerous, varied applications. Less attention, however, has been paid to its analytical possibilities, even though many advantages have been postulated and a wide range of poorly water-soluble analytes are present in samples (or waste materials) from food and drink, petrochemical, pharmaceutical, military and other industries. The main approaches, developed in recent years to exploit the use of enzymes, antibodies or antibody mimics in water-restricted environments for analytical purposes, as well as possible future directions are briefly discussed.
Sensor Immobilized enzyme Reverse micelle Review Catalysis

"Flow Injection Method For The Fluorimetric Determination Of Zinc With 8-(benzenesulfonamido)quinoline"
Microchim. Acta 1996 Volume 124, Issue 1-2 Pages 73-79
Ramon Compa&ntilde;&oacute;, Ra&uacute;l Ferrer, Jacinto Guiteras and Mar&iacute;a D. Prat

Abstract: Sample (100 µL) was injected into a carrier stream (3.8 ml/min) comprising a mixture (4:4:1) of 0.19 M SDS, Tris hydrochloride buffer of pH 8.5 and 0.14 mM 8-(benzenesulfonamido)quinoline and the fluorescence was measured at 496 nm (excitation at 364 nm). Sample throughput was ~145/h. The working range was 0.5-700 µg/l Zn, the detection limit was 0.2 µg/l and the RSD were 1.1% and 1% at 50 and 150 µg/l Zn, respectively. Calibration graphs were linear for 0.5-50, 10^-200 and 50-700 µg/l, Zn. Tolerance levels for interfering ions are tabulated. The method was applied to food after mineralization with HNO3. Measurements were made at pH 7.5 to avoid interference from Mg. Results agreed with those obtained by AAS.
Zinc Fluorescence Interferences

"A Novel Flow Injection System For Simultaneous Determination Of Nitrate And Nitrite Based On The Use Of A Zinc Reductor And A Bulk Acoustic Wave Impedance Detector"
Microchem. J. 1998 Volume 59, Issue 3 Pages 341-350
Xiao-Li Su, Po Chen, Xiao-Ge Qu, Wan-Zhi Wei and Shou-Zhuo Yao

Abstract: A novel flow injection system was developed for the simultaneous determination of nitrate and nitrite present in water, foodstuffs, and human saliva. The system is based on the use of a Zn-filled reduction column and a bulk acoustic wave impedance sensor (BAWIS) as detector. With water as carrier stream, both nitrate and nitrite are converted online to NH3, whereas with sulfamic acid, only nitrate is converted to NH3. The NH3 formed diffuses across a PTFE membrane and is trapped in an acid stream causing a change in the solution conductance, which was monitored by a BAWIS detector. At a throughput of ~60 h-1, the proposed system exhibited a linear response to the concentration. of nitrate and nitrite from 2.5 µM to 1.00 mM, with detection limits of 1.7 and 1.8 µM, respectively, and the relative standard deviation of the peak heights (n = 6) ranged between 0.83 and 1.75% for the entire working range. In anal. of real samples, the simultaneous determination of nitrate and nitrite was achieved by the proposed method with a simple change of the carrier stream between water and sulfamic acid, and the results agreed well with those of conventional colorimetry. (c) 1998 Academic Press.
Nitrate Nitrite Conductometry Sensor Gas diffusion Reduction column Teflon membrane Simultaneous analysis

"Development And Application Of An Immobilized Enzyme Electrode For The Determination Of Sulfite In Foods And Feeds"
Anal. Lett. 1991 Volume 24, Issue 4 Pages 551-555
Nabirahni, M.A.;Vaid, R.R.

Abstract: An electrode incorporating sulphite oxidase immobilized (by the bovine serum albumin - glutaraldehyde method) on pig intestine was developed for determining SO32-; the method involved amperometric detection of H2O2 formed in the oxidation reaction. Optimum assay conditions comprised 25 mM Tris buffer of pH 8.76 at 35°C. The linear dynamic range of the electrode was 5.5 to 500 M SO32- for the initial-rate method and 5.2 M to 1.0 mM for the steady-state method. Nitrite interfered in the determination of SO32-; relative to SO32-, the responses to HSO3- and S2O52- were 68 and 110%, respectively. Results with the electrode were well correlated (r = 0.952) with those by the reference Monier - Williams method.
Sulfite HPIC Electrode Apparatus Detector Immobilized enzyme

"Dextrose Sensor In Food Analysis"
Anal. Lett. 1995 Volume 28, Issue 7 Pages 1173-1180
Wei, D.;Lubrano, G.J.;Guilbault, G.G.

Abstract: Non-viscous liquids were measured without any sample preparation of after dilution with 0.1 M phosphate buffer of pH 7 for FIA and spectrophotometry. Carbonated drinks were diluted at 5°C; viscous samples and powders were diluted with phosphate buffer; and dry solids were ground to a powder before dilution. For steady-state measurements, a 100-200 l sample was added to 5 mL 0.1 M phosphate buffer of pH 7. The steady state of the amperometric glucose biosensor was measured. For FIA, the sample was diluted with 0.1 M phosphate buffer of pH 7 and injected (100 l) into a carrier stream of phosphate buffer (loc. cit). Peak heights were recorded. Flow-rates of 1 ml/min and the wall-jet mode were used for different food types. The calibration graph had a greater linear range (20-200 ng/dl) for the FIA method compared with the steady-state method. Good precision (RSD <10%), a fast response time (30 s) and a 1-2 min recovery time were observed. The biosensor was stable for similar4 months. The results compared well with those obtained by spectrophotometry.
Dextrose Sensor

"Fast Analysis Of Lysine In Food Using Protein Microwave Hydrolysis And Electrochemical Biosensor"
Anal. Lett. 1996 Volume 29, Issue 7 Pages 1125-1137
Marconi, E.;Panfili, G.;Messia, M.C.;Cubadda, R.;Compagnone, D.;Palleschi, G.

Abstract: Sample (equivalent to 100-140 mg protein) was hydrolyzed with 6 or 8N-HCl under N2 in a 630 W microwave digestion system (Mod. MSD 2000; CEM Corp.). The hydrolysis conditions were: 80% power, 100°C, 100 psi for 1 min for the first cycle; and 80% power, 155°C, 100 psi for 5 min for the second cycle. The hydrolysate (20 µL) was injected into a flow injection system equipped with a lysine probe comprising an amperometric H2O2 transducer and lysine oxidase covalently immobilized on a preactivated polymeric support. At pH 4.2, interference from arginine was insignificant and the calibration range was linear from 0.01-0.5 mM lysine. The optimum flow rate was 200 µL/min at which phenylalanine interference is at a minimum. The result compared well with those obtained by traditional hydrolysis - ion-exchange chromatographic procedures with relative errors of 10%.
Lysine Sensor Sample preparation Interferences

"Flow Monitoring Of Glutamate And Aspartate In Foods And Pharmaceutical Products With Immobilized Bienzyme Electrochemical Cells"
Electroanalysis 1992 Volume 4, Issue 9 Pages 851-857
G. Palleschi*, M. G. Lavagnini, D. Compagnone, P. Bertocchi, D. Moscone

Abstract: Electrochemical thin-layer and wall-jet amperometric cells incorporating an Immobilon-AV immunoaffinity membrane on which L-glutamate oxidase and aspartate aminotransferase were covalently co-immobilized were used in continuous-flow and flow injection analysis. The flow-through system gave higher sensitivity and the flow injection system gave better reproducibility and faster response. The wall-jet cell was the more suitable for flow injection analysis. The flow injection technique was used to determine glutamate (I) in foods and aspartate (II) in pharmaceuticals. The calibration graphs were rectilinear for 1 to 500 and 10 to 500 µmM of I and II, respectively; corresponding detection limits were 1 and 5 µM. Results correlated well with those obtained by HPLC. Electrochemical enzyme cells for glutamate and aspartate anal. have been assembled and used in continuous-flow and in flow injection analysis. The enzymes, glutamate oxidase (GOD) and aspartate amino-transferase (AST), were co-immobilized on an Immobilon Immuno-affinity membrane, which was placed into a three-electrode, flow-through cell. Additional protective membranes were used to reduce the electrochemical interferences and to protect the immobilized enzymes. Thin-layer and wall-jet cells were used and compared. Calibration curves for glutamate and aspartate showed a linearity range of 1-500 µmol/L and 10^-500 µmol/L respectively. The sensitivity was higher using the flow-through system with a response time of 2 min. Better reproducibility was achieved using the FIA procedure with a response time of less than 1 min. Glutamate in food and aspartate in some pharmaceutical products were determined Results were compared and correlated well with an HPLC procedure.
Glutamate Aspartate Electrode Method comparison Immobilized enzyme Interferences

"Investigation Of Batch Measurements With Immobilized Enzyme Reactors And Amperometric Electrodes"
Electroanalysis 1995 Volume 7, Issue 8 Pages 785-787
Aziz Amine, Giuseppe Palleschi

Abstract: The optimization of all parameters which govern the response of a biosensor is generally very difficult. Flow-injection analysis with an immobilized enzyme reactor (IER) is considered as a complementary method or possibly an alternative to a biosensor. Similarly, the proposed batch experiments with an IER, can in many instances advantageously replace the biosensor. The principle consists of successive insertions of appropriate IERs into the cell solution after a steady-state current output has been recorded from the interfering species present in the solution. Selected examples of enzymatic assays in food samples, aimed either at eliminating electrochemical interferences or allowing multi-substrate determinations are reported and discussed.
Amperometry Interferences Immobilized enzyme

"High Performance Liquid Chromatography Separation Of Some Mono- And Disaccharides With Detection By A Post-column Enzyme Reactor And A Chemically Modified Electrode"
J. Chromatogr. A 1987 Volume 408, Issue 1 Pages 157-170
Gy&ouml;rgy Marko-Varga

Abstract: The effluent from a chromatographic column was mixed with nicotinamide adenine dinucleotide coenzyme (NAD+) buffer and passed through a packed-bed reactor containing immobilized glucose dehydrogenase. Oxidation of the carbohydrates emerging from the column produced an equivalent amount of reduced coenzyme (NADH), which was detected electrochemically using an electrode modified with 7-dimethylamino-1,2-benzophenoxazine (Meldola Blue). Separation was effected in three different chromatographic systems containing a protonated ion exchanger, a calcium(II)-saturated or a lead(II)-saturated ligand exchange column. Separation, detection and k? values are reported for glucose, 2-deoxyglucose, xylose, mannose, cellobiose, lactose, ribose and glucosamine. The detection limit was 2 ng for a 20-l injection of glucose and the response was linear up to 6300 ng. Samples from fermentation of penicillin were analyzed for lactose and glucose with the described detector. A comparison with the recordings from a refractive index detector showed that the selectivity of the enzymes and the modified electrodes are necessary for the determination of glucose and lactose.
Monosaccharides Disaccharides Amperometry HPLC Electrode Immobilized enzyme Post-column derivatization

"Determination Of Organic Acids, Amino Acids And Saccharides By High Performance Liquid Chromatography And A Post-column Enzyme Reactor With Amperometric Detection"
J. Chromatogr. A 1992 Volume 591, Issue 1-2 Pages 165-173
R. M&ouml;gele, B. Pabel and R. Galensa

Abstract: Organic acids, amino acids, and sugars are separated by HPLC and converted online by immobilized enzymes. The enzymes employed are covalently bound to a synthetic carrier. H2O2, which is produced in the reaction with oxidases, makes possible the application of an electrochemical detector. This arrangement combines the separation efficiency of HPLC, the substrate specificity of enzymes, and the high sensitivity of electrochemical detection. The enzymes act according to known reaction mechanisms, but coupling with HPLC leads to a promising extension in the field of biosensors. The simple pretreatment of the samples (often a dilution step is sufficient) allows a rapid anal. of foods and biological or clinical extracts. The examples presented demonstrate the very high sensitivity of the method with detection limits in the nano- to picomolar range, and a wide field of application.
Acids, organic Amino Acids Saccharides HPLC Amperometry Sensor Post-column derivatization Immobilized enzyme Indirect

"Online Dialysis With High Performance Liquid Chromatography For The Automated Preparation And Analysis Of Sugars And Organic Acids In Foods And Beverages"
J. Chromatogr. A 1995 Volume 705, Issue 2 Pages 195-203
Eric V&eacute;rette*, Fran&ccedil;ois Qian and Fabrice Mangani

Abstract: A quick, simple and robust technique is described for on-line clean-up and analysis of raw liquid food samples containing complex matrices such as dairy products, soft drinks, and fermented beverages. A completely automated sample preparation system (ASTED XL) provides an efficient way of removing macromolecular and microparticulate interferents by high-performance dialysis, prior to HPLC analysis of the sugars, organic acids and related compounds. Processing samples on-line in the concurrent mode permitted both high reproducibility and optimal throughput.
Sugars Acids, organic HPLC Sample preparation Dialysis

"Anion-exchange Chromatography With Electrochemical Detection Of Alditols And Sugars At A Cu2o-carbon Composite Electrode"
J. Chromatogr. A 1997 Volume 773, Issue 1-2 Pages 115-121
Tommaso R. I. Cataldia,*, Diego Centonzea, Innocenzo G. Casellaa and Elio Desimonib

Abstract: An anion-exchange column coupled with an amperometric sensor was used for the quantitative analysis of alditols and simple sugars. The sensing electrode is composed of cuprous oxide dispersed in a graphite powder-polyethylene composite matrix. The resulting Cu2O-carbon composite electrode is stable in alkaline media and possesses good sensitivity, wide linear dynamic ranges and low detection limits for alditols, mono- and disaccharides. Alditols and carbohydrates are weakly ionizable compounds, so an anion-exchange column was employed for their chromatographic separation with an alkaline eluent. The separation problems due to the presence of low but uncontrolled amounts of carbonate in the alkaline mobile phase have been largely solved by the addition of Ca2+ or Ba2+ at a millimolar level and the consequent formation of carbonate insoluble salts. Using this strategy, the alkaline eluent provides improved separations without compromising the column's lifetime, electrode performance and chromatographic system. Under the optimal operating conditions, the detection limits of D-sorbitol, D-mannitol and D-glucose were 50, 40 and 80 pmol, respectively, with a linear concentration range up to 5 mM. Examples of applications, which include the separation and detection of D-sorbitol, D-mannitol and common sugars present in food samples, are illustrated. 35 References
Alditols Sugars Sorbitol d-Mannitol d-Glucose Amperometry Electrode Electrode Ion exchange Optimization

"Determination Of Ochratoxin A At The Ppt Level In Human Blood, Serum, Milk And Some Foodstuffs By High Performance Liquid Chromatography With Enhanced Fluorescence Detection And Immunoaffinity Column Cleanup: Methodology And Swiss Data"
J. Chromatogr. B 1995 Volume 666, Issue 1 Pages 85-99
Bernhard Zimmerli* and Rudolf Dick

Abstract: An improved specific analytical method for ochratoxin A (OA) is presented, combining HPLC separation with enhanced fluorescence detection by post-column addition of ammonia. Commercial immunoaffinity columns (Biocode) were for the first time applied to the cleanup of extracts of body fluids; they could be used up to 20 times for blood serum. The extraction efficiency of OA from human serum and milk as well as its derivatization to esters were studied and improved. The quantitation limit for OA was improved and estimated at 5-10 pg/g for human milk and serum. The mean recovery of OA from serum and milk was estimated at 85%. The overall coefficient of variation for OA determinations in serum, milk and selected foodstuffs was estimated at 10% (concentration range 0.01-5 ng/g). The method was applied to sera of 368 blood donors, 10 pairs of maternal and fetal sera, as well as to 40 human milk samples and selected foodstuffs; the results are discussed.
Ochratoxin A HPLC Fluorescence Post-column derivatization

"Optimization Of A Polarized Photometric Detector Equipped With A Split-type Flow Cell And Its Analytical Application To Oligo-saccharides"
J. Pharm. Biomed. Anal. 1997 Volume 15, Issue 9-10 Pages 1383-1387
Atsushi Yamamoto*, Toshihiko Wataya, Kazuichi Hayakawa, Akinobu Matsunaga, Masayuki Nishimura and Motoichi Miyazaki

Abstract: A novel, non-modulated polarimeter called a polarized photometric detector (PPD) was previously described by the authors. The PPD enables the measurement of the optical rotation of chiral compounds as a change in absorbance by placing two linear polarizers on either side of a flow cell of a conventional photometric detector. The present study describes the optimization of the conditions of PPD for highly sensitive detection of saccharides. To maximize the light intensity, the light balancing filter and slit were removed from the detector (Shimadzu model SPD-10AV). These modifications resulted in an approximately 15-fold increase in the incident light intensity when the maximum current was applied to the lamp. When this intense light was transmitted through the polarizers, the signal intensity followed the theoretical equation for phase angles up to around 1 rad. If the energy of the transmitted light was less than 700 mV, however, the baseline noise was too great to determine the chiral analyte accurately. Setting the phase angle between two polarizers at 50°C and the detection wavelength at 400 nm provided the most suitable conditions. This detector was applicable for the determinations of oligosaccharides in foodstuffs separated by HPLC using gradient elution.
Oligosaccharides Polarimetry Spectrophotometry Instrumentation Flowcell Optimization

"Stopped-flow Time Difference Analysis. A Review"
Anal. Sci. 1988 Volume 4, Issue 5 Pages 445-454

Abstract: A novel analytical method which includes absorbance measurements by using stopped-flow apparatuses was developed, which can be applied to determine absorbance changes as low as 0.002 O.D, with good precision in a time range of less than seconds, even for background absorbances of 1.5 to 2.0 O.D. This method, termed 'stopped -flow time difference analysis' (abbreviated to SFTDA), utilizes the progress curve of a reaction for both quantitative and qualitative analyzes, based on the absorbance change and the rate of reaction, respectively. A differential kinetic analysis of mixed components is possible, due to the different reaction rates of the components, which can also be effective to exclude interference by coexisting materials. Several examples of the applications of the SFTDA method with macro-apparatuses are described, which include a determination of ascorbic acid down to 10^-7 M, a highly sensitive determination of inorganic phosphate of ppb and sup-ppb level in environmental water, and an improvement in several characteristics of the methods for protein determination. Two types of microstopped- flow apparatuses were built, which need only 1/10 of the sample amount necessary for conventional macro-apparatuses, and still have a comparable performance. Their utility in clinical chemistry is demonstrated.
Protein Clinical analysis Spectrophotometry Review Stopped-flow

"Research And Development Topics In Analytical Chemistry"
Anal. Proc. 1981 Volume 18, Issue 1 Pages 7-26
C. Southway, L. S. Bark, J. Marshall, L. Bezur, R. Fakhrul-Aldeen, J. M. Ottaway, M. R. Cave, D. M. Kaminaris, L. Ebdon, D. J. Mowthorpe, C. M. Ashworth, S. L. Castleden, G. F. Kirkbright, Adrian A. Baker, James B. Headridge, S. Forbes, Samuel J. Lyle and

Abstract: The following are summaries of seven of the papers presented at the Research and Development Topics in Analytical Chemistry Meeting of the Analytical Division held'on April 1st and 2nd, 1980, at the University of Kent at Canterbury. Summaries of five other papers were published in the December, 1980, issue of Analytical Proceedings (p. 533).
Bismuth Thorium-232 Copper Osmium Coprostanol

"Simultaneous Determination Of Nitrites And Nitrates By Flow Injection Analysis"
Agrochemia 1988 Volume 28, Issue 4 Pages 119-122
Karlicek, R.;Dolejsova, J.;Polasek, M.

Abstract: The method involves the reaction of NO2- with sulfanilamide and N-(1-naphthyl)ethylenediamine in acid solution, with absorbance measurement of the red dye. Nitrite (0.02 to 2 mg l-1) was determined directly in extracts of feed, food or soil; NO3- (0.5 to 20 mg l-1) was determined in the same sample after reduction by metallic Cd. Automated analysis of 45 samples h-1 was possible.
Nitrite Nitrate Sample preparation Spectrophotometry Simultaneous analysis

"Determination Of Chloride In Food By Segmented Continuous-flow Analysis (CFA) And Flow Injection Analysis (FIA)"
Alimentaria 1991 Volume 28, Issue 222 Pages 57-59
Leon, J.A.;Centrich, F.

Abstract: Chloride in meat, canned food and cheese was determined by continuous-flow analysis and flow injection analysis methods based on the formation of a SCN- - Fe3+ complex with the displacement of SCN- from Hg(SCN)2 by Cl-. Determination limits were 60 and 50 ppm of NaCl by continuous-flow analysis and flow injection analysis, respectively. Results were in good agreement with those obtained by a titrimetric method. Turbid and strongly colored samples required dialysis before analysis.
Chloride Sample preparation Spectrophotometry Dialysis Segmented flow Method comparison

"Flow Injection Analysis: Its Possibilities And Applications In Food Analysis"
An. Bromatol. 1986 Volume 37, Issue 1 Pages 197-205
Luque De Castro, M.D.

Abstract: Flow injection analysis and its applications to food analysis are reviewed. (59 references).
Review Optimization

"Automated Determination Of Vitamin C In Food Stuffs And Biological Materials"
Analusis 1989 Volume 17, Issue 9 Pages 519-525
Bourgeois, C.F.;Chartois, H.R.;Coustans, M.F.;George, P.R.

Abstract: The sample (e.g., organ tissue, blood plasma, foodstuff) is extracted with aqueous 5% metaphosphoric acid and the extract is placed in an automated apparatus. Ascorbic acid is oxidized by iodine to dehyroascorbic acid, which is coupled with 4,5-dimethyl-1,2-phenylenediamine to give a fluorescent quinoxaline derivative. This compound is extracted into isoamyl alcohol, back-extracted into a basic aqueous solution where it forms a hydrophilic salt, and the fluorescence is measured against that of a borate buffer. Compared with conventional fluorimetric methods the measurement is carried out in an almost pure solution, thus minimizing matrix interferences. The mean recovery was 98.7%, the coefficient of variation was 1.4% and the sensitivity was 20 ng mL-1.
Ascorbic acid Fluorescence Sample preparation Automation Redox Extraction Buffer Sensitivity Apparatus Interferences

"Enzyme Entrapped Polypyrrole Modified Electrode For Flow Injection Determination Of Glucose"
Biosens. Bioelectron. 1990 Volume 5, Issue 2 Pages 149-156
M. Trojanowicz, W. Matuszewski and M. Podsiada

Abstract: Immobilization of glucose oxidase in electropolymerized polypyrrole film on the surface of a platinum wire electrode, provides a convenient sensor for flow injection glucose determination. An upper limit of linear response for 100 µL injected sample volume was estimated as 20 mM, whereas a 500 µL injected sample volume gave an estimated detection limit of 0.5 mM. A simple electrode preparation procedure allows quick electrode renewal before each series of measurements. A Pt wire electrode was cleaned electrochemically in aqueous Na2HPO4 (50 g l-1) - KOH (20 g l-1) at 80°C by multiple polarizaiton. Electropolymerization was carried out at room temperature for 10 s at 0.8 V vs. the SCE in a solution containing glucose oxidase (1 g) and freshly distilled pyrrole (20 µL) in 6 mL of deaerated 0.1 M KCl. The electrode was used in a flow injection system (illustrated) with a 60-cm delay coil and a flow-through detector. The upper limit of rectilinear response for a 100 µL sample was 20 mM; for a 500 µL sample, the detection limit was 0.5 mM. The electrode signal declined by 20% after 5 days, but the active layer was easily renewed, and the system was applicable in clinical and food analysis.
Glucose Electrode Electrode Immobilized enzyme Detection limit Detector

"An FIA Biosensor System For The Determination Of Phosphate"
Biosens. Bioelectron. 1991 Volume 6, Issue 7 Pages 581-587
K. B. Male and J. H. T. Luong*

Abstract: A flow injection analysis (FIA) biosensor system for the determination of phosphate was constructed using immobilized nucleoside phosphorylase and xanthine oxidase and an amperometric electrode (platinum vs silver/silver chloride, polarized at 0.7 V). When a phosphate- containing sample was injected into the detection cell, phosphate reacted with inosine in the carrier buffer to produce hypoxanthine and ribose-1-phosphate in the presence of nucleoside phosphorylase. Hypoxanthine was then oxidized by xanthine oxidase to uric acid and hydrogen peroxide, which were both detected by the amperometric electrode. The response of the FIA biosensor system was linear up to 100 µM phosphate, with a minimum detectable concentration of 1.25 µM phosphate. Each assay could be performed in 5-6 min and the system could be used for about 160 repeated analyzes. This system was applicable for the determination of phosphate in various food products and plasma, and the results obtained agreed well with those of the enzymatic assay. The development and performance of the cited flow injection system for phosphate determination are described. The biosensor incorporates purine-nucleoside phosphorylase (I) and xanthine oxidase (II), co-immobilized on a pre-activated nylon membrane and attached to the tip of a amperometric electrode (Pt vs. Ag - AgCl, polarized at 0.7 V). On injection of the sample solution into the flow cell, phosphate reacts with 1 mM inosine in the carrier buffer solution [100 mM imidazole - 100 mM NaCl (pH 7)] in the presence of I to produce hypoxanthine and ribose 1-phosphate. The hypoxanthine is then oxidized by II to uric acid and H2O2, which are detected by the amperometric electrode. The system response was rectilinear up to 100 µM-phosphate, with a detection limit of 1.25 µM. The response time was 2 min, the assay time was 5 to 6 min, and the system could be used for ~160 analyzes. The method was applied to phosphate determination in plasma and various food products. The results agreed well with those obtained by enzyme assay.
Phosphate Amperometry Electrode Electrode Sensor Biotechnology Buffer Immobilized enzyme Method comparison Sensitivity

"Improvement Of The Selectivity Of An Flow Injection Analysis Amperometric Biosensor System For Glucose"
Biosens. Bioelectron. 1993 Volume 8, Issue 5 Pages 239-247
K. B. Male and J. H. T. Luong*

Abstract: In the cited flow injection analysis system, samples (75 µL) were injected into a stream (31 ml/h) of 1 mM acetate buffer of pH 4-7.2 and carried to a column (12 cm x 2.54 mm i.d.) of acetate AG 1-X8 anion-exchange resin (200-400 mesh) to remove interfering substances including uric acid and ascorbic acid. The stream then merged with a stream (31 ml/h) of 100 mM acetate buffer of pH 5.5 containing 1 M NaCl and passed through an enzyme reactor column (6 cm x 2.54 mm i.d.) prepared by immobilizing glucose oxidase onto aminopropyl glass beads using glutaraldehyde (details given) and packing the beads into Tygon tubing. H2O2 was determined using an amperometric flow cell with an Immunodyne membrane (3 µm) and a Pt electrode held at +700 mV vs. Ag/AgCl. The optimum pH for ascorbic acid and uric acid removal were 4 and >6, respectively; the anion-exchange column was less efficient at removing paracetamol. The calibration graph was linear for up to 1 mM glucose and the detection limit was 10 µM. Reproducibility was good and the enzyme reactor was stable for >2000 analyzes; sample throughput was 17/h. The method was applied to urine, plasma, fruit juices and pea and bean seed extracts (details given). A flow injection analysis (flow injection analysis) biosensor system has been developed for the determination of glucose from urine, blood plasma and foodstuffs. Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an enzyme column. The hydrogen peroxide released from the conversion of glucose to gluconic acid was monitored by a platinum electrode vs. silver/silver chloride poised at +700 mV. As a novel aspect to the improvement of the selectivity of the biosensor system, an anion exchange column was placed upstream to remove uric acid, ascorbic acid or acetaminophen, three major electroactive interfering substances which usually occur in urine and blood plasma. Among several resins tested, the effective adsorption of uric and ascorbic acids could be accomplished using an acetate anion exchanger, and the selectivity coefficient was pH dependent. The binding of acetaminophen to the resin was much less efficient and, in all cases, the selectivity coefficient was independent of the operating temperature up to 37°C. When applied to real samples, the data obtained by the biosensor system compared well with those of the standard hexokinase assay. The immobilized glucose oxidase could be reused for at least 2000 repeated analyzes without loss of its original activity.
Glucose Amperometry HPIC Electrode Sensor Biotechnology Selectivity Immobilized enzyme Interferences Glass beads

"Amperometric Mediated Carbon-paste Biosensor Based On D-fructose Dehydrogenase For The Determination Of Fructose In Food Analysis"
Biosens. Bioelectron. 1997 Volume 12, Issue 12 Pages 1233-1243
Pedro A. Paredesa, Josefina Parelladaa, V&iacute;ctor M. Fern&aacute;ndezc, Ioanis Katakisb and Elena Dom&iacute;ngueza,*

Abstract: A new mediated amperometric biosensor for fructose is described. The sensor is based on a commercially available D-fructose dehydrogenase. The enzyme is incorporated in a carbon paste matrix containing Os(bpy)(2)Cl-2 as redox mediator that achieves electron transfer at 0.1 V (versus Ag/AgCl) with maximum apparent current densities of 1.2 mA/cm(2). The dependence of the steady-state current on the loading of the mediator and the enzyme, other electrode construction parameters, the operating potential, the pH and the temperature was studied. In the steady-state mode the response current was directly proportional to D-fructose concentration from 0.2 to 20 mM with a detection limit of 35 µM (signal-to-noise ratio, S/N, 3). In the flow injection analysis mode the response current was directly proportional to D-fructose concentration from 0.5 to 15 mM with a detection limit of 115 µM (S/N 3). The sensor was used for the determination of fructose in food samples in a flow injection system and validated with a commercial enzyme kit. (C) 1998 Elsevier Science S.A. 32 References
d-Fructose Amperometry Sensor Electrode Immobilized enzyme Optimization

"Rapid Determination Of Glucose And Sucrose By An Amperometric Glucose-sensing Electrode Combined With An Invertase/mutarotase-attached Measuring Cell"
Biosens. Bioelectron. 1997 Volume 12, Issue 9-10 Pages 1013-1020
Fumio Mizutania,* and Soichi Yabukia

Abstract: Glucose and sucrose are simultaneously determined by the use of an enzyme sensor system consisting of a glucose-sensing electrode based on a lipid-modified glucose oxidase and a measuring cell that contains an invertase/mutarotase-coimmobilized layer. From the current response of the enzyme electrode after the addition of a glucose/sucrose mixture, the concentrations of the two kinds of sugars can be separately determined: the concentration of glucose (0 . 2 µM-3 mM) is determined from the steady-state current increase obtained from 2 to 6s after the addition of the mixture, and that of sucrose (10 µM-6 mM), from the rate of current increase from 8 to 20 s after the addition. The relative standard deviations are 1 . 7% for glucose and 3 . 1% for sucrose (n = 10). The system can be applied to the rapid determination of glucose and sucrose in food samples.
Glucose Sucrose Amperometry Sensor Electrode Nafion membrane Simultaneous analysis

"High-throughput Flow Injection Analysis Of Glucose And Glutamate In Food And Biological Samples By Using Enzyme/polyion Complex-bilayer Membrane-based Electrodes As The Detectors"
Biosens. Bioelectron. 1998 Volume 13, Issue 7-8 Pages 809-815
Fumio Mizutani*, Yukari Sato, Yoshiki Hirata and Soichi Yabuki

Abstract: The concentration of glucose was determined by a combination of flow injection analysis (FIA) with amperometric enzyme sensor detection. The enzyme sensor was prepared by immobilizing glucose oxidase on an electrode coated with a polyion complex layer consisting of poly-L-lysine and poly(4-styrenesulfonate). The inner, polyion complex layer was useful for preventing electrochemical interferents (e.g., L-ascorbic acid, uric acid and acetaminophen) from reaching the electrode surface, which was effective for reducing the interferential responses upon the injections of biological and food samples. The sensor-based system could be used for the determination of glucose from 10 µM to 3 mM with the sampling rate of 180 h-1, and was stable for more than 2 mo. An FIA system for determining L-glutamic acid (3 µM-0.5 mM) was also prepared by using an enzyme electrode based on a glutamate oxidase/polyion complex-bilayer as the detector.
Glucose l-Glutamic acid Amperometry Electrode Electrode Interferences Apparatus Detector

"Anomeric Specificity Of Glucose Uptake Systems In Lactococcus Cremoris, Escherichia Coli, And Saccharomyces Cerevisiae: Mechanism, Kinetics, And Implications"
Biotechnol. Bioeng. 1992 Volume 40, Issue 1 Pages 137-146
Stig Benthin*, Jens Nielsen, John Villadsen

Abstract: The mechanism and kinetics of the glucose uptake systems of three representative microorganisms are studied during cultivation in a chemostat. The three microorganisms are Lactococcus cremoris, Escherichia coli, and Saccharomyces cerevisiae. Two models describing respectively competitive and independent uptake of the two glucose anomers are tested on experimental data where α- and β-glucose are determined by flow injection analysis after pulse addition of the pure anomers to a chemostat. The very accurate experimental results are used to give a convincingly clear model discrimination for all three microorganisms. The uptake of glucose by S. cerevisiae occurs by a competitive mechanism with preference for α-glucose (Kα = 32 mg/L and K(beta) = 48 mg/L). Surprisingly, the glucose uptake by the two bacteria is shown to be mediated by anomer specific transport systems with no competitive inhibition from the other glucose anomer. This novel finding has not been described in the literature on the phosphotransferase system. In L. cremoris the relative uptake rates of the glucose anomers match the equilibrium composition exactly (36% α- glucose). In E. coli the relative uptake rate of α- glucose at glucose unlimited growth is 26%, which means preference for β-glucose. However, the saturation constants of the two sites in E. coli are Kα = 2 mg/L and K(beta) = 15 mg/L, and a preference for α-glucose is exhibited at very low glucose concentrations. The results are of considerable importance in relation to enzyme based on- line measurements during fermentations as well as to the modeling of glucose limited growth and product formation.
β-d-Glucose α-d-Glucose

"Simultaneous Determination Of Components In Food By FIA Including Parallel Configuration Of Enzyme Columns"
Bunseki 1990 Volume 1990, Issue 5 Pages 379-383
Matsumoto, K.

Abstract: A review is presented, with 8 references, of the use of FIA and immobilized-enzyme columns in the determination of components, e.g., glucose, fructose, sucrose, lactic acid and ethanol in food products. Procedures and instrumentation are discussed.
Glucose Fructose Sucrose Ethanol Lactic acid Enzyme Column Immobilized enzyme Review

"Determination Of Arsenic And Selenium By Hydride Generation Atomic Absorption Spectrometry (flow Injection Or Continuous-flow) Method Combined With A Hydride Collecting Trap"
Can. J. Anal. Sci. Spectrosc. 1995 Volume 40, Issue 5 Pages 117-124
Siska, R.;Borszeki, J.;Gegus, E.

Abstract: A hydride collecting cold trap hydride generation AAS method has been developed using a flow injection (FI) or a continuous-flow (CF) system, applicable to the high sensitivity determination of arsenic and selenium, characterized by a detection limit of 10^-20 pg/mL. The best relative detection limits and sensitivity for this system could be achieved using the CF operation mode. Accuracy and reproducibility of the method were investigated by the analysis of dilute solutions produced by decomposition of international CRM samples of various types. The results of the determinations agree well with the certified values. Reproducibility of the measurements is good considering especially the extreme low initial concentrations. The remarkable feature of the method is the relatively low blank value which is partly due to the use of high purity acids and reagents, and partly to the very low risk of contamination when the work is done in a closed system. Further on, several water samples were investigated by this method, the arsenic and selenium content of which could not be determined previously. Also numerous food samples having low content of As and Se were analyzed. (12 references)
Arsenic Selenium Spectrophotometry Cold trap Optimization Reference material Volatile generation Volatile generation

"Online Sample Preparation With Flow Injection Analysis: Avoiding Additional Preparation Steps"
Chem. Rundsch. 1987 Volume 40, Issue 11 Pages 11-NA
Winter, B.

Abstract: As illustrated by the determination of NH4+ and of surfactants, it is shown that single stages or the entire sample preparation can be integrated by use of flow injection analysis. Problems of the matrix in determining NH4+ in, e.g., waste water, soil extracts or acid digests of food are discussed; the NH4+ can be separated from the matrix by gas diffusion from NaOH medium into a receptor stream for photometric detection. Surfactants can be separated from environmental, food or pharmaceutical samples by liquid - liquid ion-pair extraction into CHCl3, with use of a PTFE membrane as phase separator and photometric detection. Flow diagrams for these analyzes are presented.
Ammonium Surfactants Sample preparation Spectrophotometry Gas diffusion Online digestion Ion pair extraction Phase separator Teflon membrane Tecator

"Environmental Immunoassays And Other Bioanalytical Methods: Overview And Update"
Chemosphere 1997 Volume 34, Issue 5-7 Pages 1011-1025
James Sherry

Abstract: Immunoassays and bioanalytical techniques can aid the cost effective detection and quantification of trace contaminants in the environment, food, and human and animal populations. This overview of recent progress shows that rapid advances have occurred in the development and validation, of assays for many contaminants of both industrial and agricultural origin. Promising antibody based techniques such as immunoaffinity chromatography, biosensors, and flow injection immunoanalysis continue to evolve. Such techniques can not only help lower costs and improve efficiency, but can also allow the range of hypotheses that can be tested in many environmental studies to be broadened by permitting the determination of trace residues in small volume samples that would be otherwise difficult to analyze.
Biochemical analysis Immunoassay Sensor Review

"Biosensors And Flow Injection Analysis"
Curr. Opin. Biotechnol. 1992 Volume 3, Issue 1 Pages 31-39
Chien-Yuan Chen and Isao Karube

Abstract: A review is presented, with 56 references. Applications of the technique, viz. diagnostic analysis, analysis of food and agricultural products, environmental analysis, are discussed. Combining flow injection analysis with a biosensor is a novel biosensing process which has allowed speedy and accurate analysis. Diagnostic analysis is the most important application for biosensing flow injection analysis, but other applications include bioprocess monitoring, analysis of food and agricultural products, as well as environmental analysis. In addition, the analysis of compounds, such as explosives and abused drugs, and monitoring of Salmonella, the microorganism that causes food poisoning, have been reported.
Sensor Review Process monitoring

"Determination Of Glucose And Fructose With An Immobilized-enzyme Reactor"
Dtsch. Lebensm. Rundsch. 1989 Volume 85, Issue 4 Pages 103-108
Koch, M.;List, D.

Abstract: Directions are given for co-immobilizing hexokinase and glucose-6-phosphate dehydrogenase (with or without glucose-6-phosphate isomerase) on Eupergit C (Roehm); use of freeze-dried enzymes and a thin layer of carrier gave preparations with a load of up to 100 mg g-1 of total enzyme. The product, packed in columns (3 cm x 4 mm), was used for continuous-flow analysis of, e.g., fruit juices. The mobile phase contained buffer (pH 7.6), triethanolamine, ethyl 4-hydroxybenzoate, Mg salt, 2% (v/v) of propan-2-ol, ATP, and NAD+ or NADP+. The NADH or NADPH produced was detected at 340 nm. Conversion of glucose was quantitative at flow rates of 0.4 to 0.5 mL min-1. The calibration graph was rectilinear up to 1.6 mM, with a detection limit of 3.5 µM. Fructose was determined after conversion into glucose by the isomerase, but this conversion was not quantitative at any reasonable flow rate (~50% at 0.4 mL min-1). The columns were very stable, and each could convert up to 120 µmol of glucose, corresponding to 15,000 analyzes in triplicate. Results for glucose by this method were well correlated with those by a reference method involving use of enzymes in solution (r = 0.996).
Glucose Fructose Spectrophotometry Immobilized enzyme Column Buffer Method comparison Standard method

"Flow Injection Analysis Of Carbonate, Sulfite And Acetate In Food"
Dtsch. Lebensm. Rundsch. 1996 Volume 92, Issue 10 Pages 323-328

Abstract: For carbonate, drinking water was analyzed directly, mineral water was ultrasonically degassed, and orange drink was ultrasonically degassed and diluted with water (1:2). Sulfite in white wine was determined directly. For acetate, pickled gherkins and pepperoni were extracted with water. Solutions were injected into a water carrier, the stream was mixed with 5 mM H3PO4 to release the acidic gas or vapor, and this diffused into bromocresol violet/bromothymol blue/cresol red/KCl indicator in carbonate buffer (pH 8.3) for photometric detection at 430 nm or into dilute NaOH of pH 9.5 for potentiometric detection, or into iodine/KI/starch solution of pH 9.5 for photometric detection of sulfite at 620 nm. Alternatively, for acetate, the sample solution was adjusted to pH 8.4 with NaOH and injected into FeCl3 for photometric determination of the Fe-acetate complex at 405 nm. Conditions were optimized (details given), and means of overcoming interference are given. The iodimetric method was preferred for sulfite. Results agreed well with those of standard methods.
Sulfite Carbonate Acetate ion Spectrophotometry Potentiometry Interferences Standard method Method comparison Optimization

"Determination Of Cholesterol-content In Food Products And Possibilities Of Automation Of Measurement"
Elelmez. Ip. 1998 Volume 52, Issue 6 Pages 169-173
T&ouml;m&ouml;sk&ouml;zi S&aacute;ndo- Baticz Orsolya- &Ouml;rsi Ferenc

Abstract: A flow injection (FIA) method, based on enzymatic reactions was developed for measurement of total cholesterol-content. The new method was tested by prepared commercial food samples. Direct sapon. was used as sample preparation After sapon. the nonsaponificable fraction was dissolved in distilled water with detergent-content (sodium-cholate as detergent). For all experiments combined enzyme-reagent was used. It was found that this method is suitable for rapid automatic measurement of cholesterol-content from food of animal origin. The results showed that the FIA technique could be an alternative to standard gas-chromatography method.
Cholesterol Sample preparation Enzyme Method comparison

"Determination Of Traces Of Zinc By Flow Injection Spectrophotometry With 2-hydroxy-3-[(4-phenylazophenyl)triazeno]-5-sulfobenzoic Acid"
Fenxi Huaxue 1996 Volume 24, Issue 12 Pages 1472-1472
Guo, Z.X.;Zhang, S.Y.

Abstract: With 0.05 M Na2B4O7/NaOH buffer of pH 10.8 as the carrier stream (5.2 ml/min), ethanolic 0.68 mM reagent/aqueous 4% emulsifier OP (unspecified)/H2O (20:3:77) as the reagent stream (5.2 ml/min) and detection at 520 nm, the calibration graph was linear for 0.072-0.05 mg/l of Zn, with a detection limit of 0.036 mg/l. Masking with NaF/potassium sodium tartrate/sodium sulfosalicylate permitted the tolerated amounts of Al(III), Fe(III), Cd(II) and Hg(II) to be greatly increased. The method was used in the analysis of human hair, rice, flour and tap water, with recoveries of 70.9-100.5%. The results were compared with those obtained by dithizone-extraction spectrophotometry.
Zinc Spectrophotometry Sample preparation Dithizone Extraction

"Flow Injection Analysis. A New Technique In Analytical Chemistry"
FMBRA Bull. 1985 Volume 5, Issue NA Pages 210-NA
Osborne, B.G.;Barrett, G.M.

Abstract: NA
Bromate Iron Spectrophotometry Tecator

"Automated Food Analysis Using Continuous-flow Analytical Systems"
Food Anal. 1984 Volume 1, Issue 2 Pages 247-294
Ram B. Roy

Abstract: A review with 85 references on applications of continuous-flow analysis systems for food analysis. (SFS)

"Determination Of Reducing Sugars By The Neocuproine Method Using Flow Injection Analysis"
Food Chem. 1992 Volume 43, Issue 1 Pages 65-69
Miguel Peris-Tortajada, Rosa Puchades and Angel Maquieira*

Abstract: A flow injection method was optimized for the cited determination. A 143 µL sample was injected into a stream of Cu(II) - neocuproine reagent (prep. described) at 1.15 mL min-1 and the mixture was passed through a dialysis unit and a reactor (100-cm long). The eluting stream was merged with 0.5 M NaOH, at 1.15 mL min-1, and passed through a reactor (200-cm long) at 65°C before the absorbance of the solution was measured at 460 nm. Recoveries are tabulated for three dialysis membranes. Recoveries of reducing sugars from wine and foods were ~100%.
Sugars, reducing Spectrophotometry Optimization Dialysis Membrane Heated reaction

"Comments On The Standard Fluorometric Determination Of Riboflavin In Foods And Biological Tissues"
Food Chem. 1992 Volume 43, Issue 1 Pages 79-82
L. F. Russell* and Joseph T. Vanderslice

Abstract: The vitamin B-2 content of foods has historically been determined as total riboflavin (TRF), and the most common method of TRF analysis has been the AOAC standard fluorometric procedure. A modification of this method to permit the use of flow injection analysis (FIA) is reported here. a number of foods were analyzed and the results generally agreed with the published values. However, the standard method was not found to be universally suitable for all types of samples.
Riboflavine Fluorescence Method comparison Standard method

"Simultaneous Determination Of Maltose And Glucose Using A Dual-electrode Flow Injection System"
Food Chem. 1995 Volume 52, Issue 2 Pages 187-192
Hong-Bo Qu, Xian-En Zhang* and Shu-Zheng Zhang

Abstract: Glucose oxidase (GOD) membranes were prepared by dropping 3 µL of 20% BSA and 2 µL of 2.5% glutaraldehyde solution on to a porous Teflon membrane where they were mixed, spread and left to stand for 30 min at 30°C. The amyloglucosidase/glucose oxidase (A/G) membrane was prepared in the same way but with 5 µL of amyloglucosidase mixed with 6 µL glutaraldehyde solution. The membranes were covered with a dialysis membrane and fixed over an O2 electrode tip to form part of a FIA system (diagram given); 25 µL of the sample was injected into the water flow stream (2.86 mL/min) at 37±0.05°C and the electrode output was recorded. Calibration graphs were linear from 0.3-30 mM/l of sugar with RSD of 3.2% and 1.6% for the GOD and A/G electrode, respectively. Highly active enzyme membranes were made which showed no decay in 20 days. The method was comparable with the Fehling titration method and could be used for online monitoring and control in industrial processes.
Glucose Maltose Electrode Electrode Process control Dialysis

"Review Of Chemiluminescent Methods In Food Analysis"
Food Chem. 1996 Volume 55, Issue 1 Pages 7-15
M. J. Navas and A. M. Jim&eacute;nez

Abstract: The purpose of the present review is to sketch out the scope of chemiluminescence in food analysis. Practical considerations are discussed. Specific applications to the determination of N-nitroso compounds, sugars, food oxidation, hormonal anabolics and metabolites, metals and other interesting compounds. There is also discussion on how alcohols, enzymes, etc. have been revised. Possibilities and limitations of the various reaction and detection systems are evaluated.
Chemiluminescence Review

"Effect Of Processing On The Content Of β-N-oxalyl-α,β-diaminopropionic Acid (β-ODAP) In Grass Pea (Lathyrus Sativus) Seeds And Flour As Determined By Flow Injection Analysis"
Food Chem. 1998 Volume 62, Issue 2 Pages 233-237
Girma Akalu, Gillis Johanssonband Baboo M. Nair

Abstract: The effect of cooking, roasting, autoclaving and fermentation on the content of β-ODAP in the whole seeds and flour of grass pea (Lathyrus sativus) were studied at different levels of temp., time, pH, degree of soaking and moisture content. The method of determination used was flow injection anal., with immobilized glutamate oxidase and horseradish peroxidase. The whole seeds flour was found to contain about 922 mg 100 g-1 β-ODAP in dry wt. basis. The reduction of β-ODAP content, in samples which were cooked for 60 min and roasted (150°C for 60 min) was 57% and 82%, respectively. The content of β-ODAP in dry seeds autoclaved for 30 min also showed a significant (p = 0.05) reduction by 39%, as compared to that of raw whole seeds. Similarly, by cooking of presoaked seeds the content of β-ODAP was reduced by up to 67%. Neither the back-slopped fermentation process nor the spontaneous fermentation were effective in reducing the content of β-ODAP. Whereas roasting and autoclaving of the milled samples caused significant (p = 0.05) reduction in the content of β-ODAP up to 30% and 50%, respectively., compared to that of raw whole seeds.
β-N-Oxalyl-L-α,β-diaminopropionic acid Immobilized enzyme

"Application Of Flow Injection Analysis Technique In The Food Technology Industry"
Prumysl Potravin 1993 Volume 44, Issue 4 Pages 166-168
Karlicek, R.

Abstract: A review with 21 references. The common discrete automatic analyzers as well as the centrifugal separator analyzers are relatively complicated in their use. A new original approach to chemical analyzes is their performing in continuous flow analyzers, e.g. Technicon Auto-Analyzer. Cost consideration has recently resulted in a preference for flow injection analysis (FIA), which is believed to be the simplest automation technique available at present, being partly or fully automated, with a continuous flow and controlled dispersion. The reaction products are measured in flow detectors giving its output on a recorder. The characteristics of the method, its instrumentation, equipment suppliers, ways of a practical application solution, and the application fields of this technique especially in anal. of liquid food substances are described. (SFS)

"Overview Of Rapid Methods And Automation In Food Microbiology With Emphasis On Flow Injection Analysis"
Lebensm. Wiss. Technol. 1991 Volume 24, Issue 3 Pages 189-197
Lemieux, L.;Puchades, R.;Simard, R.E.

Abstract: Current status and future developments in the field of rapid methods and automation in food microbiology are reviewed. Use of flow injection techniques applied to food quality control is also discussed. Headings include: Detection of biomass and microbial contamination; Bioluminescence assays; Continuous flow analysis; Segmented flow analysis applications; Flow injection analysis; FIA applications; New trends; and Future possibilities.
Automation Review

"From FIA To Bio-probes - Biochemical Analytics In Examples Of Application"
GIT Fachz. Lab. 1990 Volume 34, Issue 9 Pages 1045-1046
Bilitewski, U.;Schmid, R.D.

Abstract: A review is presented on the application of online analytical systems (FIA and in situ electrodes) for the enzymatic or immunochemical analysis of e.g., fermentation liquors, drinking water and foodstuffs. (22 references).
Electrode Sensor Review Enzyme

"Sulfite Determination Of Foods And Beverages"
Ind. Bevande 1988 Volume 17, Issue 97 Pages 398-400
Cipriani, I.

Abstract: Alternatives to the Monier-Williams assay for sulfites are outlined. In one procedure, a Kjeltec distillation app. is used to produce SO2, which is then trapped and titrated with NaOH. Alternatively, flow-injection anal. and colorimetry may be used. The reagents employed are either pararosaniline (which forms a complex with SO2 that absorbs at 560 nm) or malachite green (decolorization by SO2, monitored at 615 nm). When applied to food and wine, all 3 alternative procedures gave values that were consistent with the Monier-Williams method. (SFS)
Sulfite Spectrophotometry Method comparison

"Simultaneous Flow Injection Determination Of Diquat And Paraquat In Foodstuffs, Natural Waters And Biological Fluids"
Int. J. Environ. Anal. Chem. 1991 Volume 44, Issue 4 Pages 243-252
T. P&eacute;rez Ruiz; C. Martinez Lozano; V. Tom&aacute;s

Abstract: Sample (100 g) of pulped potato tubers was macerated with water and 18N-H2SO4 for ~3 min before refluxing for 5 h and filtration. Human serum (1 ml), was subjected to protein separation with sulfosalicylic acid before filtration. The filtrates and a diluted sample of synthetic urine were then analyzed for diquat (I) and paraquat (II) by the standard additions method in a dual-channel, dual-detector, flow injection system. Sample was split 1:4 (I:II) into two channels and I and I were merged (at 0.6 mL min-1) with streams of 0.1% sodium dithionite in 0.5 M borax buffer (pH 8) and 0.5% sodium dithionite in 0.5 M ammonia buffer (pH 9), respectively. I was then determined spectrofluorimetrically at 497 nm (excitation at 428 nm) and II was determined spectrophotometrically at 605 nm. The calibration graphs were rectilinear from 0.06 to 10 µg mL-1 of I and 0.2 to 20 µg mL-1 of II; detection limits were 7 µg L-1 for I and 36 µg L-1 for II. The analysis rate was 70 samples h-1. The method was applied to the determination of I and II in potable water.
Diquat Paraquat Fluorescence Spectrophotometry Buffer Dual detection Filtration Standard additions calibration

"Determination Of Environmental Contaminants In Foods By Liquid Chromatography - An Overview"
Int. J. Environ. Anal. Chem. 1992 Volume 49, Issue 1-2 Pages 15-29
J. F. Lawrence

Abstract: Gas chromatography (GC) has long been used for the determination of trace levels of environmental contaminants in many different types of samples The technique has reached an advanced state of development. However, there are many types of contaminants which are not amenable to GC due to thermal instability or poor volatility and thus high performance liquid chromatography (LC) has become the preferred technique for their analysis. Included in this group are certain agricultural, industrial and natural contaminants which may find their way into food for human consumption. This paper discusses approaches to the LC determination of selected contaminants in foods. The techniques involve extraction and clean-up of the samples followed by direct analysis or pre- or post-column derivatization with either UV absorption of fluorescence detection. The potential of LC-mass spectrometry and chemical derivatization for confirmation of identity is also discussed.
Polynuclear aromatic hydrocarbons Pesticides HPLC Mass spectrometry Review Post-column derivatization Optimization

"Immunochemical Techniques And Immunosensors For The Analysis Of Dealkylated Degradation Products Of Atrazine"
Int. J. Environ. Anal. Chem. 1996 Volume 65, Issue 1-4 Pages 113-126
Wittmann, C.

Abstract: Field format dipstick and automated flow injection immunoanalysis (FIIA) methods are described. De-ethylatrazine, the major metabolite of atrazine, was chosen as representative analyte and was dissolved in ethanol. For the dipstick format, antibodies were immobilized on a nylon membrane. For the FIIA method, microglass beads (diameter 50-100 µm), surface modified with carboxylic groups, were used as support. Horseradish peroxidase was used as tracer and goat anti-rabbit IgG as primary antibody. The dipstick format gave a measurement range of 0.1-10 µg/l de-ethylatrazine, the FIIA 0.01-10 µg/l. Both formats enabled water and liquid food samples to be measured without the need for enrichment or clean-up steps. For soil samples, two extraction steps can be eliminated from the normal requirements for GC analysis. The two immunoassays gave results in good agreement with those from GC.
Atrazine Immunoassay Sensor Glass beads Immobilized enzyme Method comparison Nylon

"Development Of A Flow Injection Analysis Immunosensor For The Detection Of Escherichia Coli"
Int. J. Food Microbiol. 1995 Volume 27, Issue 2-3 Pages 129-137
P. Bouvrette and J. H. T. Luong*

Abstract: A flow injection immunoanalysis system has been developed for the detection of Escherichia coli in artificially contaminated food samples. Anti-E. coli antibodies were covalently immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an immunoreactor. After adsorption of the cells onto anti-E. coli antibody bound glass beads, 4-methylumbelliferyl-β-D-glucuronide was injected into the system which was then hydrolyzed by the adsorbed E. coli cells containing β-D-glucuronidase, an enzyme which is very specific to E. coli and to a few other strains of Shigella. Fluorescent 4- methylumbelliferone released from the enzymatic reaction was then detected by a fluorimeter. Owing to the specificity of the antibody towards E. coli, the FIA system was very selective for detection of E. coli whereas Shigella boydii, another GUD-positive bacterium, did not give any response. The FIA system was successfully used for detecting as low as 5 x 10(7) CFU/ml E. coli in less than 30 min and was reusable for at least 300 repeated assays. The immunoreactor yielded reproducible results during 3 months of experimentation if stored overnight at 4°C in carrier buffer containing 0.05 to 0.25% Tween 20.
Bacteria, echerichia coli Immunoassay Fluorescence Biotechnology Sensor Glass beads Immobilized antibody

"Flow Injection Analysis - A New Technique For Food And Beverage Analysis"
Int. J. Food Sci. Technol. 1988 Volume 23, Issue 6 Pages 541-554
Osborne, B.G.;Tyson, J.F.

Abstract: A review is presented, with 49 references.

"Determination Of Vitamin B6 In Foods And Other Biological Materials By Paired-ion High Performance Liquid Chromatography"
J. Agric. Food Chem. 1985 Volume 33, Issue 3 Pages 359-363
Jesse F. Gregory and Debra Feldstein

Abstract: Food, human plasma or milk, or rat liver or muscle samples, were homogenized in sulfosalicylic acid with 4'-deoxypyridoxine (as internal standard) and CH2Cl2. After centrifugation, the aqueous phase was applied to a column of Bio-Rad AG2-X8 anion-exchange resin (200 to 400 mesh; Cl- form) with 0.1 M HCl as mobile phase. The fraction containing pyridoxine was subjected to HPLC on a column (3 cm x 4.6 mm) of octadecylsilica (3 µm) with gradient elution with 0 to 2.5% of propan-2-ol in 33 mM potassium phosphate - 8 mM octanesulfonic acid (pH 2.2). Post-column derivatization was with NaHSO3 in 1 M sodium phosphate buffer (pH 7.5) and fluorescence detection was at 400 nm (excitation at 330 nm). The coefficient of variation were <2%; recoveries were 78.7 to 103.2%. Good correlation with published data was achieved.
Vitamin B6 Pyridoxine HPLC Ion exchange Fluorescence Post-column derivatization

"Solid-phase Spectrophotometry"
J. Anal. Chem. 1995 Volume 50, Issue 4 Pages 440-446
Brykina, G.D.;Marchenko, D.Y.;Shpigun, O.A.

Abstract: A review is presented of the trends in development of solid-phase spectrophotometry over the last 6 years. The measurement technique and the sample preparation were considered the most important factors for precise results. (54 references).
Metals, rare earth HPLC Ion exchange Review Solid phase detection

"Immunoassay Of Pesticides: An Update"
J. AOAC Int. 1995 Volume 78, Issue 4 Pages 1079-1090
Bennett M. Kaufman and Marion Clower, Jr

Abstract: A review is presented to update information previously reported in 1991 (J. Assoc. Off. Anal. Chem., 1991, 74, 239) dealing with the measurement of pesticide levels in foods and crops by immunoassay. New immunoassays are discussed together with refinements of the common enzyme-based solid-phase assays such as use of coated magnetic particles, antibody-coated crystals and continuous-flow devices. (111 references). Measurement of levels of pesticide residues in foods and crops most often requires extensive cleanup and instrumental techniques such as gas chromatography. Immunoassay measurement techniques, on the other hand, may be used directly on the test portion or require only minimal cleanup. Further refinements of the common antibody-enzyme-based solid-phase assays, such as use of coated magnetic particles, antibody-coated crystals, and continuous-flow devices, have extended the measurement range and applicability of these assays. Likewise, new immunoassays for pesticides have been developed, and existing assays have been refined, optimized, and more completely characterized and validated. In addition to their ability to accurately and reliably measure amounts of residues present in food and crops, immunoassays can be readily used as rapid screening methods for contaminants in field samples. We have previously reviewed much of the work in the area of pesticide immunoassay; this report updates previous information and discusses some new immunoassay techniques.
Pesticides Immunoassay Review

"Semi-automated Fluorimetric Method For Determination Of Vitamin C In Foods: Collaborative Study"
J. AOAC Int. 1983 Volume 66, Issue 6 Pages 1371-1376
DeVries JW

Abstract: The automated continuous-flow procedure of Egberg et al. (cf. Anal. Abstr., 1977, 33, 2F52), which is based on the manual AOAC method 43.061-43.067, was studied collaboratively by five laboratories. The inter-laboratory coefficient of variation averaged 11.1% for the manual method and 5% for the automated method. The automated method has been adopted official first action.
Ascorbic acid Fluorescence Standard method

"Automated Determination Of α-tocopherol In Food And Feed. 2. Continuous-flow Technique"
J. AOAC Int. 1984 Volume 67, Issue 3 Pages 631-634
Bourgeois CF, George PR, Cronenberger LA

Abstract: A modification is described of the manual method of Part I (see preceding abstract) for determination of α-tocopherol(I) to provide a continuous-flow-through method. The method is highly specific; natural homologues of I do not interfere. The high sensitivity of the method permits determination of I in very dilute solution, which suppresses matrix effects and renders the results reliable. Fifty determinations can be made in one day.
α-Tocopherol Interferences

"Automated Sample Cleanup For Pesticide Multiresidue Analysis. 2. Design And Evaluation Of Column-chromatography Module"
J. AOAC Int. 1984 Volume 67, Issue 4 Pages 783-789
Gretch FM, Rosen JD

Abstract: An automated system for the clean-up of food extracts for subsequent g.l.c. analysis consists of a solvent-partitioning module, as described in Part I (Anal. Abstr., 1984, 46, 10F15), and a column-chromatographic module. The latter module comprises a number of short Florisil columns connected to a continuous-flow sampler via a 10-port sampling valve with two large-volume holding coils and a 60-port switching valve. The system allows for the concurrent elution of the contents of one column (with two different solvents) and loading of a subsequent column. The automated procedure requires only 20% of the solvents and adsorbents needed in the manual procedure and is three times faster.
Pesticides HPLC Sample preparation Solvent extraction Valve

"Determination Of Phosphocholine With An Alkaline Phosphatase Reactor Using Flow Injection System"
J. Chem. Soc. Pak. 1995 Volume 17, Issue 1 Pages 25-28
Yaqoob, M.;Hussain, G.;Masoom, M.

Abstract: Sample (90 µL) was injected into a 0.1 M Tris hydrochloride buffer pH carrier stream (0.9 ml/min) via a rotary valve (a diagram of the flow injection manifold is given). The stream then passed through an enzyme column (3 cm x 2.5 mm i.d.) immobilized with alkaline phosphatase and crosslinked with glutaraldehyde. The resulting stream was merged with 0.005 M ammonium molybdate and 0.9% ascorbic acid reducing agent (0.6 ml/min) in an 80 cm mixing coil. The formation of molybdenum blue was monitored spectrophotometrically at 660 nm. The sample rate was 45 samples/h. The detection limit was 10 µM-phosphocholine and the RSD (n = 10) was 1%. Sample (90 µL) was injected into a Tris hydrochloride buffer stream (0.9 ml/min) via a manifold (diagram given) and passed through an enzyme column (3 cm x 2.5 mm i.d.) of alkaline phosphatase. The resulting stream was merged with 0.05 M ammonium molybdate and 0.9% ascorbic acid in a 80 cm coil. The absorbance of the Molybdenum blue formed was measured at 660 nm. The detection limit was 10 µM with an RSD (n = 10) of 1%. The sampling rate was up to 45 samples/h. The system may also be used for the analysis of biological and food samples.
Phosphocholine Spectrophotometry Immobilized enzyme

"Comparison Of Two Enzyme Sequences For A Novel L-malate Biosensor"
J. Chem. Technol. Biotechnol. 1997 Volume 68, Issue 1 Pages 31-36
Nenad Gajovic*, Axel Warsinke, Frieder W. Scheller

Abstract: Two novel amperometric biosensors for the determination of L-malic acid in food samples have been compared. Both sensors make use of a Clark-type O-2-electrode but differ in the enzymes used. The first sensor is composed of malate dehydrogenase (decarboxylating), also known as 'malic enzyme' (MDH(dec.), EC and pyruvate oxidase (POP, EC It covers a linear detection range from 1 µmol L-1 to 0.9 mmol L-1 L-malate, with a response time of 1.5 min (t(90)) and a relative standard deviation of 3.5%. Measurements with real samples offered a good correlation with the standard enzymatic assay (difference±7%) Stored at room temperature, the response of the sensor is constant for 8 days. The second biosensor is based on the three enzyme sequence malate dehydrogenase (MDH, EC, oxaloacetate decarboxylase (OAC, EC and pyruvate oxidase (POP, EC It has a non-linear calibration curve. Concentrations from 5 µmol L-1 to 1 mmol L-1 L-malate can be detected, within a response time of 1.5 min and with a relative standard deviation of 20%. The lower detection limit for L-malate is 2 µmol L-1. The response is constant for 10 days when the sensor is stored at room temperature. 11 References
l-Malate Potentiometry Electrode Sensor Detection limit Immobilized enzyme Method comparison

"Flow Injection Analysis Of Hydrogen Peroxide And Their Application To Determinations Of Biological Substances"
J. Flow Injection Anal. 1995 Volume 12, Issue 1 Pages 23-34
Matsubara, C.

Abstract: Flow injection analysis of hydrogen peroxide using immobilized oxidase enzyme reactors are useful for the determination of trace amounts of biological substances in serum and foods, such as glucose, oxalate. Recent examples of reserch in these areas are presented in this review.
Hydrogen peroxide Electrode Review

"Determination Of Phytic Acid In Foods By Ion Chromatography With Post-column Derivatization"
J. Food Sci. 1985 Volume 50, Issue 2 Pages 541-542
Phillippy, B.Q.;Johnston, M.R.

Abstract: Extracts of infant formula powder, soya flour, soya isolate, wheat bran and wheat bread were directly injected into a Dionex model 12 Auto Ion Analyzer without need for a pre-purification step. Ion Separator AG3 (guard) and AS3 (analytical) columns were used with 0.11 M HNO3 as mobile phase. The eluate from the analytical column was directed into a Dionex reactor and combined with 0.1% Fe(NO3)3 solution in 2% HClO4: absorbance of the mixture was measured at 290 nm. Over-all recovery was 96 ± 4%. Results were compared with those obtained by an ion-exchange procedure. Ion chromatography gave generally lower values for phytic acid(I) compared with ion exchange: this was attributed to the latter method also measuring interfering substances, including breakdown products of I
Phytic acid HPIC Spectrophotometry Interferences Post-column derivatization

"Piezoelectric Biosensor For Detection Of Salmonella-typhimurium"
J. Food Sci. 1997 Volume 62, Issue 5 Pages 1067-1071
Ye J, Letcher SV, Rand AG

Abstract: A flow injection analysis (FIA) system was developed based on a piezoelectric biosensor for detection of Salmonella typhimurium. The anti-Salmonella spp antibody was immobilized onto the gold electrode coated quartz crystal surface through a polyethylenimine-glutaraldehyde (PEG) technique and dithiobis-succinimidyl propionate (DSP) coupling. The PEG technique proved more successful for FIA applications than the DSP coupling. The biosensor had responses of 23-47 Hz in 25 min when the PEG immobilization technique was employed, with R-2>0.94 for Salmonella typhimurium concentrations of 5.3 x 10(5) to 1.2 x 10(9) CFU/mL. 17 References
Bacteria, salmonella Piezoelectric crystal Sensor Sensor Electrode Electrode

"Potentiometric Biosensor For Detection Of L-malate And D-isocitrate Employing A Carbonate Selective Electrode And Enzyme Immobilization For Flow Injection Analysis"
Prev. Nutr. Food Sci. 1998 Volume 3, Issue 1 Pages 36-42
In-Sook Kwun, Meera Kim

Abstract: Ion-selective eleltrodes(ISEs) are simple electrodechemical devices for the direct measurement of ions in the samples. A novel potentiometric biosensor for the determination of L-Malate or D-isocitrate has been developed by using CO2-3 -ISE-FIA system was composed of a pump, an injector, a malic enzyme or isocitric dehydrogenase enzyme reactor, a CO2-3 -ISE, a pH/mV meter, and an integrater. The various factors, such as buffer capacity types of plstericizer and polymer, were optimized for the CO2-3 selectivity. In this novel CO2-3 --ISE-FIA system, the potential difference due to the amount of CO2-3 produced from each enzyme reaction was proportional to the amount of L-malate or D-isocitrate.
l-Malate d-Isocitrate Potentiometry Sensor Electrode Immobilized enzyme

"Automated Analysis Of Total Vitamin C In Foods"
J. Micronutr. Anal. 1989 Volume 6, Issue 2 Pages 109-117
Vanderslice J.T.; Higgs D.J.

Abstract: To determine the sum of ascorbic and dehydroascorbic acids (I and II, respectively), the fruit or vegetable sample is extracted in a robotic system with metaphosphoric acid - acetic acid, the extract is filtered (0.45 µm), and the filtrate is passed through a preparative C18 column into autosampler phials. The resulting solution is subjected to flow injection analysis, with 0.1 M citrate buffer (pH 4.0) containing 5 mM EDTA as initial carrier; this stream is mixed with aqueous 2.5 mM HgCl2 as oxidant for I and then with aqueous 3.1 mM o-phenylenediamine as fluorigenic reagent for total II at 70°C before fluorescence measurement (cf. J. Chromatogr. Sci., 1984, 22, 485). The only manual operation is the transfer of the autosampler phials to the autosampler.
Ascorbic acid dehydroascorbic acid Fluorescence Buffer

"Determination Of Free Fatty Acids In Foods By Flow Injection"
J. Sci. Food Agric. 1994 Volume 66, Issue 4 Pages 473-478
Rosa Puchades*, Alicia Suescun, Angel Maquieira

Abstract: Milk fat from cow and ewe milk was extracted by the method of Garcia Olmedo et al. (Anal. Bromatol., XXXI, 227) using a rotary evaporator instead of a Soxhlet extractor. Cocoa butter was extracted using the industrial process of NATRA SA (Valencia, Spain). The extracts or olive oils were homogenized with toluene in an ultrasonic bath and the homogenate injected into a carrier stream of toluene (0.95 ml/min). The carrier stream merged with a reagent stream of aqueous copper acetate/pyridine reagent of pH 6.1 (0.84 ml/min) and the solutions were mixed in a reaction coil (30 cm x 3 mm diameter). The mixed solution passed into a phase separator containing a lipophilic membrane and the copper-pyridine colored complex in the organic phase was measured spectrophotometrically at 716 nm. The calibration graph for oleic acid was linear for 0.1-5 M with reproducibility RSD (n = 12) of 1.9% at 0.3 mM and 0.8% at 2 mM. The precision RSD (n = 3) was 1.09% and recoveries were 98-101%. The effects of interferences on the method is discussed.
Fatty acids, free Spectrophotometry Method comparison

"Carbon-13 - Carbon-12 Determinations Made Easy With GC - C - IRMS"
Lab. Equip. Dig. 1991 Volume 29, Issue 5 Pages 15-17
Crossley, N.

Abstract: The principles of isotope-ratio MS and its use in dual-inlet and continuous-flow mode are described. Its application in conjunction with combustion of samples to yield CO2, which is then separated by GC, is outlined and details are given of the VG Isotech Optima instrument, which incorporates a trap for water and heart-cut facilities to divert part of the GC effluent away from the FID. The technique may be used in biomedicine, petroleum geochemistry and the food and fragrance industries.
Carbon-12 Carbon-13 GC Mass spectrometry Isotope ratio

"Application Of FIA Techniques To Food Analysis"
Lebensm. Wiss. Technol. 1989 Volume 22, Issue 5 Pages 254-263
Lemieux, L.;Puchades, R.;Simard, R.E.

Abstract: A review is presented with 113 references. The application of flow injection analysis to the determination of sugars, nitrogenous compounds, heavy metals, halogen-containing ions and other minor components is discussed.
Sugars Metals, heavy Nitro compounds Review

"Progress Of The Study On The Photometric Analysis Of Ascorbic Acid"
Lihua Jianyan, Huaxue Fence 1996 Volume 32, Issue 4 Pages 239-241
Zhang, W.D.;Wang, J.B.

Abstract: A review is presented, covering literature published between 1990-1995, of determination of ascorbic acid in foods, biological materials and drugs by e.g., conventional photometry, flow injection absorptiophotometry and catalytic-kinetic photometry. (27 references).
Ascorbic acid Spectrophotometry Review Optosensing

"Determination Of Arsenic And Selenium By Injection Combined With Cold-trap Collection Of Hydride And Continuous-flow Hydride Atomic Absorption Technique"
Magy. Kem. Foly. 1996 Volume 102, Issue 3 Pages 248-256
Siska, R.;Borszeki, J.;Gegus, E.

Abstract: Continuous-flow and flow injection hydride-generation AAS methods for the determination of As and Se are described, which involve collection of hydrides in a cold trap (diagrams of manifolds given). The detection limits were 10^-20 pg/ml. The results obtained for international standards agreed with the internationally accepted values. Reproducibility was good. The methods were applied to environmental materials (food and water).
Arsenic Selenium Spectrophotometry Cold trap Reference material

"Flow Injection Analysis Of Lipid Hydroperoxides"
Nihon Yukagakkaishi 1998 Volume 47, Issue 10 Pages 1053-1059

Abstract: Flow injection methods for lipid hydroperoxides were reviewed with 18 references. The sample loaded on the system is mixed with a reagent on line followed by a reaction and detection in series. These methods make it possible to determine lipid hydroperoxides easily and rapidly. It is required that the detection methods of FIA have rapid response, high specificity, high sensitivity and free from the effect of coexistent substances. Fluorometric detection with diphenyl-1-pyrenylphosphine was one of the most suitable methods for this purpose, the FIA using this reagent made it possible to analyze lipid hydroperoxides at 10^-13 mole level within 2 min intervals and with almost no effects by coexistent antioxidn. agents. This method was successfully applied for edible oils and some foods. Other detection methods such as colorimetry of I3- and a chemiluminescence method also described.
Hydroperoxides, lipid Fluorescence Chemiluminescence Spectrophotometry Review

"Flow Injection Analysis System For Conductometric Measurement Of Sugar Content. Study On Electrochemical Measurement Of Sugar Content Of Food, Part VII "
Nippon Shokuhin Kagaku Kogaku Kaishi 1985 Volume 32, Issue 8 Pages 576-581
Takakazu NOMURA, Hiroyuki UKEDA, Kiyoshi MATSUMOTO, Yutaka OSAJIMA

Abstract: A conductometric flow injection analysis system for measuring sugar content in food was constructed and several component of this system were investigated. The controlled-current four-electrode method was used for conductance measurements, and then the cell constant of this system was not affected by flow rate (0-5 mL min-1). The most preferrable conditions for optimum operation of the system were as follows: mixing coil length 80 cm (i.d.=0.8 mm), injection volume 0.68 ml, flow rate 2.3 mL min-1. Over the range of 5 to 30% (w/w), the linear response was obtained and the coefficient of variation was 0.20% at 20% (w/w) sucrose for 10 successive assays. The measuring time was about 3 min for each of these assays. The sugar content in citrus juice estimated with this system agreed with that obtained from phenol-sulfuric acid method within an error of 0.20% (w/w).
Sucrose Conductometry Method comparison

"Approach For Conductometric Flow-injection Analysis Of Salt Content In Food"
Nippon Shokuhin Kagaku Kogaku Kaishi 1985 Volume 33, Issue 1 Pages 61-66
Kiyoshi MATSUMOTO, Koh-ichi ISHIDA, Yutaka OSAJIMA

Abstract: The four-electrode cell system described earlier (Agric. Biol. Chem., 1984, 48, 2211) was applied to enable a.c. conductometric measurement of NaCl in foods (cf. Okayama et al., Anal. Abstr., 1981, 40, 6F40) in a flow-injection system. Because the samples of soy and Worcestershire sauce had high (12 to 22%) salt content, further sample dilution in a preliminary mixing coil was required. For injections of aqueous 15% NaCl, the coefficient of variation (n = 10) was 0.22%. Up to 70 samples h-1 could be analyzed and simple detergent cleaning of the system was effective.
Sucrose Conductometry Surfactant

"Correction For Conductometric Flow Injection Analysis Of The Salt Content In Food"
Nippon Shokuhin Kagaku Kogaku Kaishi 1986 Volume 33, Issue 5 Pages 345-348
Kiyoshi MATSUMOTO, Koh-ichi ISHIDA, Yutaka OSAJIMA

Abstract: The temperature correction and the check system of the conductometric flow injection analysis for measuring the salt content in food were proposed. The temperature dependences were approximated by linearity at 5°C interval around the center temperature of 20°C, and the resulting slopes (dC/dt) of the straight lines were calculated. The temperature coefficients were defined as the quotients where dC/dt where devided by observed conductivities (Cs) at standard temperature (Ts: nearer temperature to 20°C in each temperature section). Temperature coefficient, α=dC/(Cs dt) One can calculate the conductivity (Ct) at an arbitrary temperature (t) within each temperature section by following equation. Ct=Cs{1+(t-Ts)αn} where, αn means the temperature coefficient of the specific temperature section to which t belongs. The availability of this correction method was evaluated under different temperatures and resulted in good agreement with biases less than 0.2% (w/w) designated as NaCl.
Chloride Conductometry Heated reaction

"The Method Of Flow Injection Analysis And The Use Of Immobilized Glucose Oxidase: Glucose Determination In Food Products"
Potravin. Vedy 1991 Volume 9, Issue 2 Pages 81-88
Solich, P.;Karlicek, R.;Polasek, M.;Valentova, O.; Marek, M.

Abstract: Glucose was determined in foods by flow injection analysis (FIA) combined with the use of immobilized glucose oxidase. H2O2, a product of glucose oxidase, was detected on the basis of its Mo-catalyzed reaction with I-. The I2 produced forms a blue complex with starch and is determined at 585 nm. The calibration graph is linear in the range 0.25-0.8 mM glucose, with a relative standard deviation of 1.53 for 8 measurements at a glucose concentration. of 0.51 mM. The FIA method was used to determine glucose in candies and cookies. Accuracy, sensitivity, and speed are advantages of the proposed method. (SFS)
Glucose Spectrophotometry Immobilized enzyme

"Determination Of Lead And Cadmium In Food Samples By Flow Injection Atomic Absorption Spectrometry"
Quim. Anal. 1987 Volume 6, Issue 1 Pages 52-59
Becerra, G.;Burguera, J.L.;Burguera, M.

Abstract: Samples are dried at 105°C, then wet-ashed with 30% H2O2 solution at 50°C and subsequently at 110°C after adding HNO3. The solution is evaporated and the residue is dissolved in 0.1 M HNO3 before analysis with a flow system as described by Fukamachi and Ishibashi (Anal. Chim. Acta, 1980, 119, 383) and air - acetylene flame AAS. Standards are analyzed similarly and peak heights are measured and averaged. Detection limits for a 10-g sample are 0.23 and 0.05 µg g-1 of Pb and Cd, respectively. Results obtained on NBS bovine liver and oyster tissue agreed well with the certified values.
Cadmium Lead Sample preparation Spectrophotometry Reference material

"Spectrophotometric Flow Injection Screening Analysis Of Foodstuffs For Lead And Cadmium Exploiting Ion Association"
Quim. Anal. 1996 Volume 15, Issue 2 Pages 161-166
Piedade Sartini, R.;Gomes Neto, J.A.;Silva Lopes, T.I.M.;Zagatto, E.A.G.

Abstract: The method was based on formation of ternary complexes between Pb(II) or Cd(II) with iodide and Malachite green (MG). Sample (500 µL) was injected into a 0.05 M HNO3 carrier stream (3.2 ml/min) which merged (i) a mixture of 1 M ammonium acetate/1 mM picolinic acid/0.2% 1,10-phenanthroline buffer (0.4 ml/min) and 1.2 mg/l Pb (0.4 ml/min) and (ii) a mixture of 0.5 mM MG (0.4 ml/min) and 2 M KI/0.3% L(+)-ascorbic acid (0.4 ml/min). Detection was by absorbance measurement at 690 nm. Calibration graphs were linear for up to 500 µg/l Pb and 150 µg/l Cd and detection limits were 10 and 2 µg/l, respectively. At concentrations of less than 100 µg/l Pb and 25 µg/l Cd the analytical signals were additive and hence the method could be used to screen HNO3/H2O2 digests of foodstuffs for Pb and Cd. The sampling rate was 70/h. To determine Pb, a pre-concentration Chelex-100 column was coupled to the FIA manifold and the retained Pb was eluted with 0.3 M HNO3. With this modified manifold the linear range was 10^-250 µ/l Pb and the detection limit was 4 µg/l. The sampling rate was 45/h. Results were precise (RSD
Cadmium Spectrophotometry Chelex Column Preconcentration

"Flow Injection Analysis. 2. Equipment And Analytical Applications"
Rev. Chim. 1990 Volume 41, Issue 7-8 Pages 623-628
Danet, A.F.;Luca, C.

Abstract: A review is presented, with 22 references, of the principles and applications of the cited technique for the analysis of food stuffs, agricultrual products, drugs, products of biotechnology and environmental pollutants.
Biotechnology Review

"Study Of The Enzyme Electrode Based On Glutamate Oxidase"
Shengwu Gongcheng Xuebao 1993 Volume 9, Issue 3 Pages 277-281
Yang Qingling, Bi Kewan

Abstract: A diffusion-controlled enzyme electrode was constructed for L-glutamate determination. The glutamate oxidase was immobilized between the cellulose acetate membrane and polycarbonate membrane using serum albumine and glutaraldehyde. The enzyme membrane was attached on the hydrogen peroxide probe surface moistened with electrolyte. The linear range of the enzyme electrode extends up to 1000 mg/L. A FIA system using the enzyme electrode was developed. The system exhibited good linearity (5-8000 mg/L with r = 0.9998), rapid response time (less than 20 s, and good selectivity. The electrode can be used continually for more than 2 weeks. The coefficient of variation (CV) of 41 times measurements at the glutamate concentration of 4000 mg/L is 2.8%. So its application to fermentation process control and food analysis is very promising.
Glutamate Electrode Process control

"Determination Of Nitrite In Water And Foods By Flow Injection Analysis"
Shipin Yu Fajiao Gongye 1989 Volume 5, Issue 5 Pages 75-77
ZHAO Fenglin ; Yao Jie ; Feng Jianzhang ; Ma Huichang

Abstract: An automated analyzer. system was used to determine NO2- in food and water samples. The sample was injected into the flow tubes of the analyzer. and reacted with aminophenylsulfonic acid and α-aminonaphthalene salt to form a purple-red product. Spectrophotometric detection was at 540 nm. The method was applied in the analysis of pickled cucumber, pickled vegetable and natural water.
Nitrite Spectrophotometry Automation

"Immobilized Enzymes As Tools In Food Analysis"
Z. Lebensm. Unters. Forsch. 1994 Volume 199, Issue 3 Pages 171-182
Georg Schwedt and Kathrin Stein

Abstract: A lot of publications described the possibilities of using selective enzymatic reactions in analysis, but not much authors described applications for the analysis of real samples. In this paper important publications, which described different applications in food analysis, are reviewed. In the first section the use of biosensors for food analysis, in the second section the combination of immobilized enzymes and flow injection analysis and in the last section the use of immobilized enzymes in combination with HPLC are described. Most of the applications described used enzymes for the determination of sugars mainly glucose, but also methods for the determination of inhibitors in foods are described.
Glucose HPLC Electrode Sensor Immobilized enzyme Review

"Simultaneous Determination Of Iron, Copper And Cobalt In Food Samples By CCD-diode Array Detection-flow Injection Analysis With Partial Least Squares Calibration Model"
J. Phys: Conf. Ser. 2006 Volume 28, Issue 1 Pages 66-69
Jianping Mi, Yuanqian Li*, Xiaoli Zhou, Bo Zheng and Ying Zhou

Abstract: A flow injection-CCD diode array detection spectrophotometry with partial least squares (PLS) program for simultaneous determination of iron, copper and cobalt in food samples has been established. The method was based on the chromogenic reaction of the three metal ions and 2- (5-Bromo-2-pyridylazo)-5-diethylaminophenol, 5-Br-PADAP in acetic acid - sodium acetate buffer solution (pH5) with Triton X-100 and ascorbic acid. The overlapped spectra of the colored complexes were collected by charge-coupled device (CCD) - diode array detector and the multi-wavelength absorbance data was processed using partial least squares (PLS) algorithm. Optimum reaction conditions and parameters of flow injection analysis were investigated. The samples of tea, sesame, laver, millet, cornmeal, mung bean and soybean powder were determined by the proposed method. The average recoveries of spiked samples were 91.80%~100.9% for Iron, 92.50%~108.0% for Copper, 93.00%~110.5% for Cobalt, respectively with relative standard deviation (R.S.D) of 1.1%~12.1%. The sampling rate is 45 samples h-1. The determination results of the food samples were in good agreement between the proposed method and ICP-AES.
Clonidine Cobalt Copper Spectrophotometry Partial least squares Triton X Method comparison Optimization

"A New Setup Of Flow Injection-diode Array Detection-laser Induced Fluorescence Spectrophotometry For Simultaneous Determination Of Copper And Iron In Food Samples"
Proc. SPIE 2003 Volume 4829, Issue 1 Pages 534-536
Yuanqian Li, Jingguo Yang, Ying Zhou, and Yuanqiang Ha

Abstract: A new setup for collection and detection of fluorescence spectrum using a double-frequency Nd-YAG laser as incident light source and coupled with multichannel CCD (charge coupled device) detector and flow injection system was described in this paper. The parameters of the setup were optimized. Fluorescence spectra are measured in the range of 350 nm ~ 700 nm with the wavelength resolution of 0.3 nm and spectral response sensitivity of detector is 0.1 LX. High S/N ratio fluorescence spectrum of Rhodamine B (RhB) solution was measured and the detection limit is 10^-9 mol L-1. The setup has been applied to the simultaneous determination of Cu and Fe in food samples. The determination is based on the fluorescence quenching reaction owing to catalytic effects of the metallic ions on the oxidation reaction of RhB and H2O2. The fluorescence spectra of RhB are collected by CCD diode array detector and the overlapping spectra are processed using artificial neural networks (ANN) algorithm. The experimental variables were optimized and the proposed method is validated on determination of Cu and Fe in a wheat reference material and the food samples. The determination results of samples are in good agreement between the proposed method and Atomic Absorption Spectrophotometry (AAS). The average spiked recoveries are 93.3% ~ 95.8% for Cu and 93.4% ~ 100.2% for Fe with relative standard deviation of 0.6% ~ 7.5%.
Copper Iron Fluorescence

"Versatility Of The Titanium(IV)–Porphyrin Reagent For Determining Hydrogen Peroxide"
Bull. Chem. Soc. Jpn. 2003 Volume 76, Issue 10 Pages 1873-1888
Kiyoko Takamura and Chiyo Matsubara

Abstract: Hydrogen peroxide has been an important analyte in many fields for many years. The Ti-TPyP reagent, i.e., an acidic aqueous solution of oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) complex, was developed as a highly sensitive spectrophotometric reagent for determining traces of hydrogen peroxide. Following the addition of hydrogen peroxide to the reagent, the absorbance at 432 nm decreased and a new peak appeared at 450 nm (the Soret band) accompanied by the consumption of the complex and the formation of its monoperoxo complex, respectively. The degrees of the absorbance changes were found to be proportional to the hydrogen peroxide concentration with the apparent molar absorptivities of 1.9 x 105 (432 nm) and 1.1 x 105 (450 nm) M-;1 cm-;1 (1 M = 1 mol dm-;3). Both values are much larger than those obtained by the conventional analysis methods. Based on these facts, the determination of hydrogen peroxide was made by a batch method and a flow injection analysis (FIA) method with the detection limits of 25 pmol and 0.5 pmol per test, respectively. In this account, the Ti-TPyP reagent is assessed for determining hydrogen peroxide in rainwater and in the atmosphere, and for determining several components in foods and biofluids mediated by appropriate oxidase enzymes, to demonstrate its potential for a broad range of applications.
Hydrogen peroxide Spectrophotometry Optimization Method comparison