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: Agricultural -> dairy -> milk

Citations 53

"Determination Of Oxidized Ketone Bodies In Milk By Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 149, Issue 1 Pages 281-289
Peter Marstorp, Torbjörn AnfältLennart Andersson

Abstract: A flow injection method is described for the determination of oxidized ketone bodies in milk. Acetoacetate is decarboxylated to acetone at 100°C. Acetone is separated from the sample by gas diffusion through a teflon membrane and measured spectrophotometrically. The detection limit is 0.1 mM. Accuracy and reproducibility are good up to 5 mM. The sample capacity is up to 100 samples/h.
Acetone Ketones Spectrophotometry Gas diffusion Teflon membrane

"Evaluation Of A Dialysis Probe For Continuous Sampling In Fermentors And In Complex Media"
Anal. Chim. Acta 1984 Volume 163, Issue 1 Pages 135-141
C. F. Mandenius, B. Danielsson and B. Mattiasson

Abstract: The steam-sterilizable probe described yields samples suitable for, e.g., HPLC, flow injection analysis or enzyme calorimetry. The analyte is transferred from the sample to a flowing stream by passage through a dialysis membrane that is protected from fouling by the sample mixture by means of a magnetic stirring-bar rotating close to the membrane surface.
Dialysis Apparatus Membrane

"Continuous-flow Potentiometric Determination Of Horseradish Peroxidase With A Fluoride-selective Electrode"
Anal. Chim. Acta 1988 Volume 208, Issue 1-2 Pages 173-181
Peter W. Alexander and Carmelita Maitra

Abstract: The horse-radish peroxidase(I)-catalyzed oxidation of 0.104 M 4-fluoroaniline in 0.16 M acetate buffer (pH 4.6) by 4.45 mM H2O2 was monitored at 45°C with a F--selective electrode in a continuous-flow system (described with diagram; flow-rate 6.8 mL min-1). The detection limit was 1 miu mL-1 of I. Interference by I inhibitors was studied at 1 µM to 1 mM levels; Cu(II), Fe(III) and Co had little effect, whereas CN- and S2- caused considerable interference. The method was applied in the determination of I in turnip extract and milk.
Enzyme, horseradish peroxidase Electrode Sample preparation Potentiometry Heated reaction Interferences

"Study Of A Nickel-catalysed Glassy Carbon Electrode For Detection Of Carbohydrates In Liquid Chromatography And Flow Injection Analysis"
Anal. Chim. Acta 1991 Volume 248, Issue 1 Pages 117-125
I. G. Casella, E. Desimoni and T. R. I. Cataldi

Abstract: The electrochemical sensor was prepared by deposition of Ni from its nitrate solution on to a glassy carbon electrode. The electrode was dried in air at 35°C for 30 min, washed with water and conditioned for 2 h in 0.2 M NaOH solution with cycling between 0 and 0.8 V vs. Ag/AgCl. The electrode surface was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements with glucose. The peak currents were related to carbohydrate concentration. and scan rate, and in flow injection analysis measurements the peak area was inversely related to the flow rate. The sensor was applied to the carbohydrate LC analysis of milk and pear juice (both diluted 1000-fold with 0.2 M NaOH). It showed good background current stability, catalytic activity, detection limits and reproducibility.
Carbohydrates LC Electrode Electrode

"Automated Determination Of Lactulose In Milk Using An Enzyme Reactor And Flow Analysis With Integrated Dialysis"
Anal. Chim. Acta 1996 Volume 324, Issue 1 Pages 37-45
Michael Mayer, Meike Genrich, Wolfgang Künnecke and Ursula Bilitewski*

Abstract: The automated FIA method was based on the enzymatic hydrolysis of lactulose to fructose and galactose followed by the separation of fructose by dialysis and its detection by fructose dehydrogenase (FDH) catalyzed oxidation with ferricyanide as electron acceptor. The manifold allowed a sample stream (0.1 ml/min) to be merged with the reaction buffer stream (0.1 ml/min) containing 185 iu/ml β-galactosidase in phosphate buffer of pH 5. The flow was propelled through a reaction coil (1.3 m x 0.8 mm i.d.) operated at 50°C and the donor channel of the dialysis cell. The acceptor channel (64 mm x 2 mm x 0.5 mm) of the dialysis cell contained stationary 2 mM potassium ferricyanide in phosphate/citrate buffer of pH 5.5. After a dialysis period of 180 s, the acceptor solution was pumped through the FDH enzyme reactor to an amperometric detector where the ferrocyanate was re-oxidized. The amperometric detector was equipped with a screen-printed Pt electrode at +385 mV vs. Pt reference. The method was applied to the analysis of milk samples using a standard-addition calibration procedure. Lactulose concentrations of up to 12.28 mM were measured and these results were confirmed by a photometric method. The sampling frequency for the proposed method was 17 samples/h.
Lactulose Amperometry Electrode Dialysis Immobilized enzyme Method comparison Standard additions calibration Heated reaction

"Determination Of Cadmium, Lead And Copper In Milk And Milk Powder By Means Of Flow Potentiometric Stripping Analysis"
Talanta 1986 Volume 33, Issue 12 Pages 991-995
L. Alamestrand, D. Jagner and L. Renman

Abstract: A flow potentiometric stripping analysis procedure for the determination of cadmium, lead and copper in milk and milk powder samples is described. The instrumental arrangement consists of a glassy-carbon thin-layer cell through which six different solutions may be drawn by means of a peristaltic pump and magnetically operated valves. The glassy-carbon electrode is pre-coated with a film of mercury which can be employed for several analytical runs. The sample, diluted five-fold with Suprapur hydrochloric acid, is electrolysed for 0.5-4 min prior to stripping in Suprapur hydrochloric acid. Pump-rate, electrolysis time and potential, opening and closing of inlet valves and digital evaluation of stripping times are controlled automatically by the computer. The analytical results agree satisfactorily with the certified values for three milk powder reference samples. The detection limit for cadmium, lead and copper in milk samples after 4, 1 and 0.5 min of pre-electrolysis is 0.8, 4 and 8 µg/l., respectively. An analytical procedure for the determination of lead in samples containing high concentrations of tin is described.
Cadmium Copper Lead Potentiometric stripping analysis

"Flow Injection Analysis Of L-lactic Acid Using An Enzyme-polyion Complex - Coated Electrode As The Detector"
Talanta 1996 Volume 43, Issue 10 Pages 1815-1820
Fumio Mizutania,*, Soichi Yabukia and Yoshiki Hirataa

Abstract: An enzyme electrode for L-lactic acid was fabricated by applying 0.04 M potassium phosphate buffer of pH 7 containing 10 µM-lactate oxidase and 10 mM poly-L-lysine and the same buffer containing 20 mM poly(4-styrene-sulfonate) successively on a polished glassy carbon electrode. The electrode was then used in a FIA system. Serum or sour milk was injected into a carrier stream (0.5 ml/min) of 0.1 M potassium phosphate buffer of pH 7.7 which passed to a flow-through cell comprising the enzyme electrode a Ag/AgCl reference electrode, a stainless-steel auxiliary electrode and a PTFE gasket. The potential was set at 1 V. Calibration graphs were linear up to 2.5 mM lactic acid with a determinable concentration range up to 6 mM. The detection limit was 20 µM and the RSD (n = 100) was 1.4% for 2 mM lactic acid.
l-Lactic acid Electrode Electrode Electrode Buffer

"Evaluation Of Perchlorate Tolerant Photo-cured Calcium-selective Electrodes For Use In Flow Injection Potentiometry"
Talanta 1997 Volume 44, Issue 3 Pages 349-356
Lucy Tina Di Benedetto, Telis Dimitrakopoulos*, John R. Farrell and Peter J. Iles

Abstract: The electrode slope and sensitivity of the photo-cured Ca ISE described by Dimitrakopoulos et al. (Electroanal., 1996, 8, 391) were improved by dissolution of anhydrous CaCl2 into the membrane prior to curing. The membrane composition was as follows; 44.7% Ebcryl 600 (bisphenol A epoxyacrylate), 22.3% 1,6-hexanediol diacrylate, 5.3% Uvecryl P36 (copolymerizable benzophenone photoinitiator), 20.8% dioctyl phenylphosphonate, 5.9% calcium bis-[4-(1',1',3',3'-tetramethylbutyl)phenyl] phosphate ionophore, 0.5% potassium tetrakis(4-chlorphenyl) borate and 0.5% CaCl2. Measurements were made vs. Ag/AgCl/saturated KCl//10% KNO3. The detection limit was 1 µM-Ca2+ and the calibration graph was linear for 0.01-100 mM. The ISE also showed an improvement in selectivity over interfering divalent ions and a wider pH range. It was suitable for the determination of Ca in the presence of perchlorate by flow injection potentiometry. Calibration graphs were linear for 0.01-10 mM Ca in 100 mM NaCl and the sample throughput was 150 injections per h at a flow rate of 1.5 ml/min. The method was applied to HNO3/HClO4 digests of milk. Results agreed with those obtained by AAS.
Calcium(2+) Potentiometry Electrode Electrode Electrode Sample preparation Method comparison Selectivity Interferences

"Direct Determination Of Calcium In Milk On A Non-segmented Continuous-flow System"
Analyst 1979 Volume 104, Issue 1238 Pages 419-424
W. D. Basson and J. F. van Staden

Abstract: The determination of calcium in milk has been adapted to a non-segmented continuous-flow procedure at a sampling rate of up to 180 samples per hour. The values obtained compare favourably with those obtained by atomic-absorption spectrophotometry.
Calcium Spectrophotometry Dialysis Gas diffusion

"High Performance Liquid Chromatography Using A Color-forming Agent As A Component Of The Mobile Phase. Separation And Determination Of Magnesium And Calcium In Clinical Samples With O-cresolphthalein Complexan"
Analyst 1988 Volume 113, Issue 2 Pages 247-250
Jun'ichi Toei

Abstract: The cited determination was carried out on a column (5 cm x 4 mm) of TSK-GEL SP-2 SW. The optimum mobile phase (1 mL min-1) contained 0.2 M KCl, 0.02 M acetic acid - Na acetate buffer (pH 4.0) and 0.1 mM o-cresolphthalein complexan. Detection was at 575 nm after mixing the column eluate with 0.4 M NH3 - NH4Cl buffer (pH 10.4). Pre-treatment of samples (milk, urine, serum or saliva) removed protein-bound Ca; pre-treatment on Toyo-Pack SP cartridges to remove free Ca was unsuccessful. Transition metals and Na did not interfere at physiological concentration. The coefficient of variation (n = 7) for 2.1 ppm of Mg and 28.9 ppm of Ca in milk were 1.41 and 1.26%, respectively.
Calcium Magnesium Clinical analysis Spectrophotometry Interferences Post-column derivatization

"Simultaneous Determination Of Total And Free Calcium In Milk By Flow Injection"
Analyst 1990 Volume 115, Issue 5 Pages 605-608
Jacobus F. van Staden and Ancel van Rensburg

Abstract: A fast and reliable procedure for the determination of total and free calcium in milk is described. The method is based on the flow injection (Fl) technique. Total calcium is determined by atomic absorption spectrometry (AAS) (422.7 nm) and free calcium by spectrophotometry (580 nm). Interference in the determination of free calcium is eliminated by using a dialyser, which also separates the total and free calcium. Interference from phosphates in milk in the determination of total calcium by AAS is overcome by using a dinitrogen oxide-acetylene flame with the necessary suppression with K+. With 30 µL samples the Fl system covers a standard working range of 100-1500 mg L-1 of Ca2+. The system is suitable for the simultaneous determination of total calcium (relative standard deviation less than 1.30% for 1300-1500 mg L-1 of total calcium) and free calcium (relative standard deviation less than 0.85% for 120-170 mg L-1 of free calcium) in milk at a sampling frequency of about 60 samples h-1. The results obtained agree reasonably well with results from the AAS method. Milk samples (30 µL) were dialysed using a Technican Type C membrane incorporated in a flow injection manifold to separate free calcium. Total Ca was determined by AAS (N2O - C2H2 flame) with K+ suppression, whereas free Ca was determined spectrophotometrically at 580 nm using acidified cresolphthalein complexone as recipient stream. At 60 samples h-1 the working range was 100 to 1500 mg L-1 of free or total Ca; the corresponding coefficient of variation were 0.85 and 1.3 (n = 15).
Calcium Spectrophotometry Simultaneous analysis Dialysis Interferences Membrane

"Enzymic Flow Injection Determination Of Lactose In Milk With Online Dialysis"
Analyst 1993 Volume 118, Issue 7 Pages 855-858
Rosa Puchades, Angel Maquieira and Luis Torró

Abstract: A flow injection analysis system (diagram given) was developed for the cited determination. Milk was injected into a carrier stream of 0.06 M phosphate buffer (pH 7.6) containing 1 mM EDTA and the stream was passed through a dialysis unit. The stream was then passed through a β-galactose reactor, where the analyte was converted into glucose; the exit stream was then passed through a co-immobilized glucose oxidase-mutarotase reactor where the glucose reacted to form H2O2. A stream of 1 mM luminol in sodium carbonate (pH 11.3) converged with a stream of 8 mM potassium hexacyanoferrate(III) and after mixing, merged with the generated H2O2 stream and the resulting chemiluminescence was measured. All flow rates were 0.8 ml/min. The calibration graph was rectilinear for 20-200 mM lactose and the RSD (n = 11) was 0.49%. The recoveries ranged from 98-102% and the sampling frequency was 20 h-1. The method compared favourably with HPLC and chloramine-T methods.
Lactose Chemiluminescence Enzyme Dialysis

"Flow-through, Microwave-heated Digestion Chamber For Automated Sample Preparation Prior To Inductively Coupled Plasma Spectrochemical Analysis"
Analyst 1994 Volume 119, Issue 5 Pages 1003-1010
Laura J. Martines Stewart and Ramon M. Barnes

Abstract: A microwave-heated flow-through device for online stopped-flow sample digestion is described. The device consists of a digestion chamber (capacity 8 ml) fitted with glass inlet and outlet tubes and a reflux with a condenser attached (diagram given). The device was placed inside a microwave-heating system and used for the digestion of various biological samples. The sample and reagents were transported to the device by a peristaltic pump (concentrated acids were added manually). Digestion was effected with HNO3, HNO3/H2SO4 and H2O2 in several stages using various microwave heating powers and reaction times (details tabulated). After digestion, the solution was analyzed by ICP-AES. The method was used to determine several metals in milk, blood and urine. Quantitative results were obtained. The method afforded results comparable to those obtained by a high-pressure ashing method.
Metals Sample preparation Spectrophotometry Microwave Online digestion Stopped-flow

"Flow-through Photometric Sensor For Determination Of Sulfonamides"
Analyst 1994 Volume 119, Issue 7 Pages 1625-1628
M. T. Tena, M. D. Luque de Castro and M. Valcárcel

Abstract: The cited sensor was based on the integration of spectrophotometric detection and retention of the product of the Bratton-Marshall reaction and was used for determining sulfanilamide, sulfamethazine, sulfaquinoxaline and sulfathiazole. The flow injection manifold features two low-pressure peristaltic pumps, low-pressure injection valves and a Unicam Model 8625 UV spectrophotometer. The solid support packed in the flow cell was C18-bonded silica from Sep-Pak cartridges. The method did not require a de-bubbler to remove N2 from the flowing system. Linear ranges for the above analytes were 10^-1200 ng/ml with RSD of 2.6%. The method was used to determine the analytes in milk and water.
Sulfonamides Sensor Spectrophotometry C18 Solid phase detection

"Use Of Focused Microwaves For Expeditive Shortening Of Sample Pre-treatment: Digestion And Reduction Procedures Prior To Selenium Speciation As Selenium(IV) Or Selenium(VI)"
Analyst 1995 Volume 120, Issue 8 Pages 2171-2174
W. Bryce, A. Izquierdo and M. D. Luque de Castro

Abstract: Methods for sample digestion and reduction of Se(VI) to Se(IV) using a focused microwave digestor, prior to Se determination, are described. The sample digestion method consisted of a three-step microwave digestion programme, using HNO3 and H2O2 (details given). The reduction of Se(VI) to Se(IV) was carried out online in a flow injection manifold in a 1 m Teflon reactor placed in the microwave chamber, using 6 M HCl as reductant. After reduction, the sample stream was diluted online before Se(IV) determination by flow injection cathodic stripping voltammetry (details given). The methods were applied to various sample types, viz., milk, sausage, kidney and water, and reduced the time required for both sample digestion and Se(VI) reduction.
Selenium(VI) Selenium(IV) Sample preparation Voltammetry Heated reaction Microwave Speciation

"Three Component Flow Injection Analysis With Online Dialysis. Simultaneous Determination Of Free Calcium, Total Calcium And Total Chloride In Milk By Flow Injection Analysis And Online Dialysis"
Fresenius J. Anal. Chem. 1990 Volume 337, Issue 4 Pages 393-397
J. F. van Staden and A. van Rensburg

Abstract: Milk (30 µL) samples (at 1 sample per min) are directed to three different channels by the use of two dialysers in series. For the determination of free Ca, interference is eliminated by using the first dialyser (which also separates total and free Ca) and determination is by spectrophotometry at 580 nm. For the determination of total Ca by AAS at 422.7 nm, interference from phosphate is overcome by the use of N2O - acetylene flame with the necessary suppression with K ions. The second dialyser in series is used to eliminate interferences (e.g., from casein) before dialysed Cl is measured with a coated tubular chloride-selective electrode. The coefficient of variation for 110 to 170 mg L-1 of free Ca, 1000 to 1500 mg L-1 of total Ca and 1000 to 1800 mg L-1 of total Cl were >0.4, 1.0 and 0.3, respectively. This method compared with existing manual methods is faster, more accurate and reliable, and uses a single series of Ca standards for both total and free Ca determination.
Calcium Spectrophotometry Electrode Dialysis Simultaneous analysis Interferences

"Direct Determination Of Copper And Iodine In Milk And Milk Powder In Alkaline Solution By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 3 Pages 323-326
S. Stürup and Arne Büchert

Abstract: Milk powder (0.2 g) was dissolved in 50 mL 0.05 M KOH/0.07 M tetramethylammonium hydroxide, or 0.5 mL raw milk was diluted with 9.5 mL of the alkaline mixture. Each sample was spiked twice with 5 and 10 µg/l I2 and Cu for standard-addition calibration to overcome matrix effects. Analysis was performed using a FIA system with a 500 µL injection loop, the alkaline mixture as carrier and ICP-MS detection. The analyte masses were monitored at m/z 63 and 127. The measurement time was 70 s/injection, which resulted in a high sample throughput. The detection limits were 0.45 and 0.94 µg/l for I2 and Cu, respectively. The method was applied to monitoring over 100 milk samples.
Copper Iodine Mass spectrometry Interferences Standard additions calibration

"Flow Injection Analysis Of Lactose Using Covalently Immobilized β-galactosidase, Mutarotase, And Glucose Oxidase/peroxidase On A 2-fluoro-1-methylpyridinium Salt-activated Fractogel Support"
Anal. Biochem. 1991 Volume 194, Issue 1 Pages 16-24
Dyer Narinesingh, Valerie A. Stoute, Gershwin Davis and That T. Ngo

Abstract: Milk samples were analyzed for their lactose content using flow injection analysis and incorporating immobilized β-galactosidase or β-galactosidase/mutarotase and glucose oxidase/peroxidase bioreactors. These enzymes were immobilized, under mild conditions, on to a 2-fluoro-1-methylpyridinium salt-activated Fractogel support. The use of a phosphate buffer (0.15 M) was found to facilitate the rapid mutarotation of α-D-glucose and hence could obviate the need for the more expensive mutarotase. The chromogenic agents of choice for monitoring the reaction were 3-methyl-2-benzothiazolinone hydrazone and 3-dimethylaminobenzoic acid. Linearity was observed over the concentration range 16-160 µg/ml using lactose standards (r = 0.996). Between 30 and 40 milk samples/h can be analyzed. Comparisons are made with existing HPLC and alkaline methylamine methods for a range of milk matrices. The FIA method consistently gives the lowest standard deviations and coefficient of variation for the various milk matrices analyzed. Milk was incubated at 25°C for 10 min with concentrated HCl and then gravity-filtered. The filtrate was adjusted to pH 6.5 and mixed with 3-dimethylaminobenzoic acid and 3-methyl-2-benzothiazolinone hydrazone in phosphate buffer solution (pH 6.5). The mixture was subjected to flow injection analysis at 33°C on a column of β-galactosidase in series with a bioreactor of glucose oxidase - peroxidase, with detection at 590 nm. The calibration graph was rectilinear for 160 µg mL-1 of lactose and the coefficient of variation was 2.7 to 3.8% (n = 3). Between 30 and 40 samples per h can be analyzed.
Lactose Spectrophotometry Buffer Column Filtration Immobilized enzyme Method comparison pH Reactor Heated reaction

"Determination Of Sulfamethazine Residues In Milk By A Surface Plasmon Resonance-based Biosensor Assay"
Anal. Biochem. 1995 Volume 226, Issue 1 Pages 175-181
Sternesjo A., Mellgren C. and Bjorck L.

Abstract: The use of antibiotics and chemotherapeutics in animal husbandry has led to the occurrence of veterinary drug residues in all types of food of animal origin. Due to the specification of toxicologically based maximum residue levels for a large number of substances, existing control strategies need even faster and more sensitive methods to meet new and more rigorous regulations. The applicability of an immunosensor device for biospecific interaction analysis was investigated and the development of an assay for analysis of sulfamethazine (SMZ) in milk is described. SMZ was covalently immobilized to a carboxymethyldextran-modified gold film. Spiked samples with known concentrations of SMZ were prepared in HBS buffer and skim and raw milk for construction of standard curves. Polyclonal antibodies against SMZ were added to the sample and the immobilized surface was used to determine the amount of free antibodies by surface plasmon resonance detection. After each measurement the surface was regenerated by NaOH and HCl. In milk, the mean relative standard deviation of the assay was approximately 2% and the limit of detection less than 1 ppb. By introduction of a secondary sheep anti-rabbit antibody, the use of specific antibody could be reduced. Milk samples from the individual cow, herd, and tanker levels were analyzed and the relative standard deviations within each sample category were 4.4, 2.4, and 2.2%, respectively. The effect of some potential interferences, e.g., high somatic cells, bacterial contamination, and preservatives, was investigated. The results were not influenced in such a way that the risk for so-called false-positive findings was obvious.
Sulfamethazine Sensor Sensor

"Amperometric Determination Of Galactose, Lactose And Dihydroxyacetone Using Galactose Oxidase In A Flow Injection System With Immobilized Enzyme Reactors And Online Dialysis"
Anal. Lett. 1985 Volume 18, Issue 7 Pages 871-889
Hans Lundbăck; Bo Olsson

Abstract: In the flow injection system (described in detail) the H2O2 produced by the action of galactose oxidase on the cited compounds is detected amperometrically via a mediator. The H2O2 is fed into a stream of K4Fe(CN)6 and this solution is passed through a bed of peroxidase and thence to the wall-jet amperometric detector. The system was used to determine lactose(I) in milk, D-galactose(II) in urine and dihydroxyacetone(III) in the presence of glycerol. The rectilinear ranges for these three determinations were 0.05 to 300 mM I, 2 µM to 60 mM II and 0 to 0.5 M III
Lactose Galactose dihydroxyacetone Amperometry Electrode Dialysis Immobilized enzyme

"Flow Injection Analysis Of Chloride In Milk With A Dialyzer And A Coated Tubular Inorganic Chloride-selective Electrode"
Anal. Lett. 1986 Volume 19, Issue 13&14 Pages 1407-1419
Van Staden, J.F.

Abstract: A flow injection analysis system is described (manifold and flow diagram given), whereby samples (30 µL) are introduced into a carrier stream (3.9 mL min-1) of 1 M KNO3 and pumped through a dialyser (16 cm x 3 cm x 2.5 cm) to remove interfering compounds. The dialysed Cl- in the recipient stream (as for carrier stream) is measured with a coated tubular flow-through Cl--selective electrode. The optimization and performance of the system are discussed and the results for the analysis of 10 milk samples are compared with those obtained by the Volhard titration method. For 30 µL samples containing 0.25 to 5.0 g L-1 of Cl-, the coefficient of variation are <0.5% (n = 15).
Chloride Electrode Electrode Dialysis Interferences Method comparison Optimization

"Lactose Determination In Raw Milk With A Two-enzyme Based Electrochemical Sensor"
Anal. Lett. 1987 Volume 20, Issue 11 Pages 1803-1814
Pilloton, R.;Mascini, M.;Casella, I.G.;Festa, M.R.;Bottari, E.

Abstract: Pall Biodyne nylon 6-6 membranes (0.5 cm diameter) were treated for 1 h with 5 mL of 0.1 M 1-ethyl-3-(-3-dimethylaminopropyl)carbodi-imide in 0.1 M phosphate buffer (pH 4.4). -Galactosidase (I; 1 mg) and glucose oxidase (II; 1 mg) were spread on the membranes which were stored for 18 h. The non-covalently bound enzyme was washed from the membrane surface with 1 M NaCl in 0.1 M phosphate buffer (pH 7.0). Alternatively, 2 l of a 10 mg mL-1 enzyme solution (2 mg of I, 8 mg of II) was spread directly on to the surface of Pall Biodyne Immunoaffinity membranes. After 1 h, the membranes were washed with the same wash solution The enzymatic membrane was coupled with a H2O2-specific amperometric sensor for the determination of lactose in milk. The H2O2 produced was measured with a platinum electrode at +650 mV vs. Ag - AgCl. The method was very simple and rapid.
Lactose Electrode Sensor Immobilized enzyme

"Amperometric Determination Of Lactic Acid. Applications On Milk Samples"
Anal. Lett. 1988 Volume 21, Issue 5 Pages 727-740
Pilloton, R.;Nwosu, T.N.;Mascini, M.

Abstract: A H2O2-selective electrode (Instrumentation Lab., Milan) was coated with L-lactate oxidase as active ingredient, immobilized on a nylon net and protected by a cellulose acetate dialysis membrane, and was applied in the determination of lactate in milk in a flow injection analysis system in which the flow rate was 0.2 mL min-1, the detector cell was of ~40 µL dead volume and amperometric detection was at +0.65 V vs. a Ag - AgCl reference electrode. The carrier stream was 0.1 M phosphate buffer at pH 7.0. The calibration graph was rectilinear up to 75 µM-lactate.
Lactic acid Amperometry Electrode Cellulose acetate Membrane Immobilized enzyme Dialysis

"A Photocured Calcium Ion-selective Electrode For Use In Flow Injection Potentiometry That Tolerates High Perchlorate Levels"
Electroanalysis 1996 Volume 8, Issue 4 Pages 391-395
Telis Dimitrakopoulos*, John R. Farrell, Peter J. Iles

Abstract: A poly(methylmethacrylate) [PMMA] wall-jet electrode flow cell (2 µL dead volume) accommodating a commercial PMMA ISE (12 mm diameter) with an embedded Cu disk (6 mm diameter) coated with a Ca selective photo-cured membrane (preparation described) based on the calcium bis[4-(1,1,3,3-tetramethylbutyl)phenyl]phosphate ionophore and a lipophilic additive, potassium tetrakis(p-chlorophenyl) borate. Carrier and reference streams of 0.1 M NaCl were pumped (1.5 ml/min) through the flow cell and over a Ag/AgCl reference electrode with potentiometric detection. A 100 µL sample was injected into the carrier stream manually. Calibration plots (E/mV) exhibited log-linearity for 0.01-10 mM Ca(II) in CaCl2, which was unchanged in a 0.01 M NaCl/0.01 M NaClO4 (9:1) or 0.1 M NaClO4. The detection limit was 1 µM-Ca(II). The photo-cured electrode was satisfactory for Ca(II) measurements in the presence of high perchlorate levels and was used to measure total Ca(II) in full-cream milk. Results were in good agreement with those obtained by AAS.
Calcium Electrode Potentiometry Method comparison

"Voltammetric Behaviour And Ion-chromatographic Detection Of Nitrite At A Dispersed-platinum Glassy-carbon Electrode"
Electroanalysis 1997 Volume 9, Issue 8 Pages 596-601
Innocenzo G. Casella*, Anna M. Salvi

Abstract: The electrode was prepared by depositing 10 µL of 10 mM PtCl4 onto the surface of a glassy carbon electrode and drying at 40°C for 30 min. The electrode was conditioned in 0.1 M NaH2PO4 by cycling the potential between -0.3 and 1.3 V using a SCE reference electrode and a Pt foil counter electrode. Cyclic voltammograms were recorded over the same potential range at a scan rate of 50 mV/s. No significant interferences were observed in the presence of SDS, BSA, chloride, glycine, acetaldehyde, nitrate, sulfate, acetate and lactose. The electrode was used as an amperometric sensor for FIA systems and ion-chromatographic separations using an applied potential of 1.1 V. The detection limit was 15 nM. Calibration graphs were linear up to 0.5 mM. The method was used for the analysis of milk and pear juice. Recoveries were >85%.
Nitrite Amperometry Electrode Electrode Voltammetry Interferences

"Monitoring Of Veterinary Drug Residues By A Combination Of Continuous-flow Techniques And Column-switching High Performance Liquid Chromatography. 1. Sulfonamides In Egg, Meat And Milk Using Post-column Derivatization With Dimethylaminobenzaldehyde"
J. Chromatogr. A 1988 Volume 435, Issue 1 Pages 97-112
M. M. L. Aerts and W. M. J. Beek, U. A. Th. Brinkman

Abstract: Aqueous NaCl - NaN3 extracts or dilutions of egg, meat or milk were dialysed online vs. water or dilute buffer solution in a flat cellulose membrane. The diffusate was passed through an XAD-4 column (6 cm x 4.6 mm) and the drugs were back-flushed on to a LiChrosorb RP-8, Cp TM-Spher C18 or µBondapak C18 column for HPLC with detection at 280 nm, or at 450 nm following post-column derivatization with 4-dimethylaminobenzaldehyde. The choice of stationary and mobile phases is discussed, and capacity factors are reported for 14 drugs on the three columns with three aqueous acetonitrile-based mobile phases. The fully automated technique (flow scheme given) permits the determination of both polar and apolar sulfonamides as well as dapsone in concentration. 5 to 20 µg kg-1, with coefficient of variation of 4 to 10% and recoveries of 85 to 90%.
HPIC Spectrophotometry Post-column derivatization

"Online Sample Processing And Analysis Of Diol Compounds In Biological Fluids"
J. Chromatogr. A 1988 Volume 456, Issue 1 Pages 93-104
Karl-Siegfried Boos* and Bernd Wilmers, Eckhard Schlimme, Richard Sauerbrey

Abstract: A coupled dual-column system with optional post-column derivatization (illustrated) was used for online sample processing, trace enrichment and analysis for aromatic 1,2-diol and aliphatic cis-diol biomolecules. Catecholamines were determined in human urine acidified to pH 3.0 to 3.5 with 10 M HCl; noradrenaline and adrenaline were determined in plasma and serum treated with 10 M NaOH to pH 7 and ribonucleosides were determined in urine, serum and milk acidified to pH 4 with concentrated formic acid. Aliquots of the sample solution were applied to the HPLC system consisting of a pre-column and an analytical column. Catecholamines and ribonucleosides were detected by fluorescence and UV spectrometry, respectively. The pre-column packing, phenylboronic acid-modified silica (Hagemeier et al., Ibid., 1983, 268, 291), allowed simultaneous covalent affinity and size-exclusion chromatography.
Catecholamines Diols Ribonucleosides LC SEC Fluorescence Spectrophotometry Post-column derivatization

"Directly Coupled Sample Treatment-high Performance Chromatography For Online Automatic Determination Of Liposoluble Vitamins In Milk"
J. Chromatogr. A 1995 Volume 694, Issue 2 Pages 399-406
M. M. Delgado-Zamarre&ntilde;o*, A. Sanchez-Perez, M. C. Gomez-Perez and J. Hernandez-Mendez

Abstract: An automated sample treatment and analysis system for the determination of vitamins A, E and cholecalciferol in both powdered and liquid milk is described. Powdered milk (0.5-2 g) was dissolved in 25 mL water and liquid milk was diluted with water to 30%. The samples were hydrolyzed using a two-channel system in a coiled PTFE tubing reactor (5 m x 0.5 mm i.d.) using 60% aqueous NaOH/10% ascorbic acid/ethanol (3:1:10). A third channel containing 2.5 M acetic acid was used to neutralize the solution before pre-concentration on a Sep-Pak C18 cartridge for 5 min. The cartridge was washed with H2O/methanol (3:2) for 4 min. The vitamins were eluted with methanol into a 100 µL injection loop, then analyzed on a 5 µm Brownlee OD-224 RP-18 column (22 cm x 3.2 mm i.d.) with a 7 µm RP18 guard column (1.5 cm x 3.2 mm i.d.), 2.5 mM acetic acid/sodium acetate buffer in aqueous 99% methanol as mobile phase (1 ml/min), UV detection at 280 nm and electrochemical detection at 1.3 V. Recoveries (n = 10) were 80-105% and day-to-day RSD (n = 10) were 1.2-6.8%.
Cholecalciferol Vitamin A Vitamin E HPLC C18 Preconcentration

"Electrochemical Detection Of Pyrroloquinoline Quinone Coupled With Its Catalytic Function By Liquid Chromatography"
Anal. Sci. 1993 Volume 9, Issue 2 Pages 207-211

Abstract: Samples of milk and swine serum were deproteinized by addition of 30% trichloroacetic acid. After centrifuging, the supernatant solution was acidified with HCl to pH 0.5 and extracted with butanol. A portion (20 µL) was analyzed by HPLC on a Cosmosil 5C-18AR column (25 cm x 4.6 mm) with methanol - 6 mM H3PO4 (3:7) containing 5 µM-K3Fe(CN)6 as mobile phase (1 mL min-1). Post-column derivatization was carried out by mixing the column eluate with a stream (0.2 mL min-1) of 3 M glycine - 2.5 M ammonium buffer. The reaction coil consisted of a Teflon tube (17.5 m x 0.5 mm) maintained at 25°C. Electrochemical detection was used with a vitreous-carbon working electrode, a Ag - AgCl reference electrode and a stainless-steel tube counter electrode. Calibration graphs were rectilinear from 0.2 pM- (detection limit) to 6 µM-pyrroloquinoline quinone. The method was also applied to table vinegar.
Pyrroloquinoline-quinone HPLC Electrode Catalysis Post-column derivatization

"Determination Of Short-chain Fatty Acids In Raw Milk Using A Microbial Sensor And The Relationship With Milk Quality"
Anal. Sci. 1994 Volume 10, Issue 4 Pages 683-685

Abstract: The sensor comprised an immobilized microbial membrane (preparation details given) attached to a PTFE membrane and an O2 electrode. The microbial membrane was fixed to the OI2 electrode by a dialysis membrane of a cellulose tubing. In the FIA system milk (20 µL) was injected into the carrier solution of 0.2 M potassium phosphate buffer of pH 7 (1 ml/min) which passed through a mixing coil (60 cm x 0.8 mm i.d.) to a flow-through cell equipped with the microbial electrode. The concentration of the short-chain fatty acids in the milk was expressed as the concentration equivalent to butyric acid. The sampling frequency of the microbial sensor was 15 samples/h. The calibration graph was linear for 0.11-2.8 mM butyric acid. The microbial sensor was applied to the evaluation of milk quality.
Fatty acids, free Sensor Dialysis

"Flow Injection Analysis Of Lactose In Milk Using A Chemically Modified Lactose Electrode"
Agric. Biol. Chem. 1985 Volume 49, Issue 7 Pages 2131-2135
Kiyoshi MATSUMOTO, Osamu HAMADA, Hiroyuki UKEDA and Yutaka OSAJIMA

Abstract: Milk was injected into a flow stream of 0.1 M phosphate buffer (pH 7.5) and mixed before electrochemical detection with β-D-galactosidase and glucose oxidase immobilized on a vitreous-carbon electrode (prep. described) and, to detect electrochemical interference, a non-enzymatic electrode at +0.95 V vs. a SCE. The calibration graph was rectilinear for 0.1 to 1.5 mM and the coefficient of variation (n = 10) was <2% with 0.4 mM lactose.
Lactose Electrode Interferences Immobilized enzyme

"Chemiluminescent And Spectrophotometric Determination Of Peroxidase And Lactoperoxidase In Foods Using Flow Injection"
Analusis 1994 Volume 22, Issue 2 Pages 76-81

Abstract: Fresh or frozen vegetables were homogenized with 10 mM Tris hydrochloride buffer of pH 7 containing 1 M KCl. The mixture was centrifuged and the extract was purified on a Sep-Pak C18 cartridge. The resulting solution was injected into a carrier stream of 3 mM H2O2 (1 ml/min). The carrier and the reagent stream, 1.5 mM luminol in 0.1 M Na2CO3 buffer of pH 8.5 (1 ml/min) were mixed in a coil (30 cm x 0.5 mm i.d.) and the chemiluminescence was measured with a photomultiplier. The calibration graph was linear for 25-500 nM-peroxidase; RSD was 1.95% (n = 15) for 250 nM. Yogurt or curd was treated as above, but with a filtration step before the Sep-Pak cartridge. Milk was treated with rennet to precipitate the proteins, the mixture was filtered and passed through the Sep-Pak cartridge. The solution was injected into the carrier, 2 mM H2O2 (1.4 ml/min) and, after mixing, the carrier was merged with 5 mM guaiacol solution in 0.1 M phosphate buffer of pH 7 (1.4 ml/min) and mixed in a coil (80 cm x 0.5 mm i.d.) with detection at 436 nm. The calibration graph was linear from 25-300 nM-lactoperoxidase; RSD (n = 15) were 1.09 and 0.76%, for 20 and 200 nM, respectively.
Enzyme, peroxidase Enzyme, lactoperoxidase Chemiluminescence Spectrophotometry

"A Microdialysis Fibre Based Sampler For Flow Injection Analysis: Determination Of L-lactate In Biofluids By An Electrochemically-synthesized Bilayer Membrane-based Biosensor"
Biosens. Bioelectron. 1996 Volume 11, Issue 4 Pages 419-425
F. Palmisano, D. Centonze, M. Quinto and P. G. Zambonin*

Abstract: A microdialysis sampler consisting of Spectra/por hollow-fiber regenerated cellulose (150 µm i.d; 9000 da mol. wt. cut-off) was inserted for ~2 cm in tygon tubing (10 cm x 0.5 mm i.d.) and sealed in. This sampler was used online for FIA to dilute the sample and remove surface active agents. FIA was carried out using a Gilson minipuls 3 pump, a six-way low pressure injection valve, a wall-jet flow-through cell, a PAR 400 detector and a Y-t chart recorder (schematic given). The sampler was coupled with a Pt/overoxidized polypyrrole/lactata oxidase/poly-o-phenylenediamine biosensor; preparation described previously (Anal. Chem.), 1995, 67, 1005). The enzyme electrodes were fitted to the wall-jet flow-through cell and left overnight at ± 0.7 V in 0.1 M phosphate buffer of pH 7 to complete poly (pyrrole) overoxidation. Calibration graphs were linear up to 10 mM lactate for standard lactate solutions. The method was applied to the analysis of bovine foetal serum; RSD was 1%. This technique can be used to analyze complex matrices such as serum, milk and yogurt with no sample pretreatment. A microdialysis fiber based, low volume sampler is described which can be used in flow injection analysis (FIA) when an on-line dilution of the sample and/or removal of high molecular weight interferents is required. This device used in combination with a lactate amperometric biosensor based on lactate oxidase electrochemically immobilized in a bilayer membrane of poly(o-phenylendiamine) and overoxidized poly(pyrrole) permits the extension of the linear range of response up to 10 mM lactate. Combining microdialysis sampling with FIA and amperometric detection at an interference-free and fast-response biosensor, lactate determination in complex media such as serum, milk and yoghurt can be easily achieved with a high sample throughput and no sample pre-treatment.
l-Lactate Sensor Electrode Electrode Electrode Electrode Interferences Hollow fiber membrane Dialysis

"Flow Injection Analysis Of L-lactate With Lactate Dehydrogenase Immobilized In An Open Tubular Reactor"
Bunseki Kagaku 1984 Volume 33, Issue 12 Pages 642-647
Morishita, F.;Hara, Y.;Kojima, T.

Abstract: Lactate dehydrogenase was attached covalently to silica whiskers within a glass capillary tube (300 cm x 0.3 mm). The sample solution was injected into a carrier stream that was 2 mM in NAD+, and the NADH produced was detected fluorimetrically at 470 nm (excitation at 340 nm). The flow rate of the carrier stream, the length of the reactor tube and the pressure drop across the reactor tube, and the resulting degree of dilution of the sample band, are shown graphically as functions of the reaction time for different sampling rates and reactor-tube diameter The mean coefficient of variation (n = 4 or 5) of the peak height for injections (120 h-1) of 0.01 to 1 mM L-lactate and a reaction time of 20 s was ~2%.
l-Lactate Fluorescence Immobilized enzyme Open tubular reactor

"Flow Injection Determination Of Sugars In Foods By Use Of A Porphinatotitanium(IV) Reagent"
Bunseki Kagaku 1995 Volume 44, Issue 5 Pages 355-362
Yokoi, Y.;Matsubara, C.;Takamura, K.

Abstract: Sample solution (20 µL) was injected into a stream (0.4 ml/min) of 0.05 M phosphate buffer/1 mM MgCl2 (pH 6.6). To determine glucose, the stream passed directly to a column of glucose oxidase, merged with a stream (0.4 ml/min) of 30 µM-oxo-[5,10,15,20-tetra-(4-pyridyl)porphinato]titanium(IV), and then passed through a mixing coil (15 m x 0.5 mm i.d.) maintained at 75°C before absorbance measurement at 450 nm. To determine maltose, lactose or sucrose, the stream after injection of the sample passed first through a column of glucose oxidase/catalase, then through a column of α-glucosidase, β-galactosidase, or β-fructofuranosidase/aldose 1-epimerase, respectively, and then through a column of glucose oxidase before merging with the reagent stream. Calibration graphs for glucose and for maltose, lactose or sucrose were linear over the ranges 0.5-500 µM and 1-1000 µM, respectively, and the respective RSD (n = 10) at 100 µM-glucose, -maltose, -lactose or -sucrose were 0.74, 0.84, 0.49 and 0.75%. The four carbohydrates were determined in milk, soft beverages and wine.
Glucose Maltose Lactose Sucrose Spectrophotometry Immobilized enzyme Heated reaction

"A Poly(o-aminophenol) Modified Electrode As An Amperometric Hydrogen Peroxide Biosensor"
Electrochim. Acta 1998 Volume 43, Issue 23 Pages 3533-3539
Mar&iacute;a Ana Vald&eacute;s Garc&iacute;a, Paulino Tu&ntilde;&oacute;n Blanco* and Ari Ivaska

Abstract: An enzymatic biosensor for hydrogen peroxide based on a horseradish peroxidase (HRP)-ferrocene carbon paste modified electrode and coated with a layer of electrochemically generated poly(o-aminophenol) is reported. A linear calibration curve is obtained over the range 1 x 10^-8 M to 1 x 10^-5 M. The biosensor responds to hydrogen peroxide ina few seconds and has a detection limit of 8.5 x 10^-9 M. The response of the biosensor is diffusion controlled at low substrate concentrations. Flow injection assays of hydrogen peroxide at a sampling rate of 150 injections per hour with a relative standard deviation of 0.8% (50 samples) are possible. Applicability of the sensor for measurement of hydrogen peroxide in real samples (milk) was demonstrated.
Hydrogen peroxide Amperometry Electrode Electrode Electrode Apparatus Detector

"Detection Of Bacterial Contamination In Sterile UHT Milk Using An L-lactate Biosensor"
Enzyme Microb. Technol. 1993 Volume 15, Issue 6 Pages 508-512
Petr Skladal, Marco Mascini, Claudio Salvadori and Gianfranco Zannoni

Abstract: The fermentation of milk inoculated with bacteria was monitored amperometrically using an L-lactate biosensor and a flow injection system. This approach was compared with the measurement of pH. The effects of Enterococcus faecalis, Bacillus coagulans, Enterobacter sakazakii, Staphylococcus aureus, and Bacillus sphericus were investigated. The most promising results were obtained for Staphylococcus aureus, whose fermentation increases milk pH.
l-Lactate Amperometry Sensor Process monitoring

"Milk Acetone And Milk Urea As Markers Of Subclinical Disturbances In Dairy Herds"
FIAstar Newsletter 1986 Volume 5, Issue 1 Pages 1-NA
Andersson, L.

Abstract: NA
Acetone Urea Spectrophotometry Gas diffusion Tecator

"Determination Of Nitrate And Nitrite In Milk And Milk Products By Flow Injection Analysis"
FIAstar Newsletter 1987 Volume 6, Issue 1 Pages 1-NA
Munksgaard, L.L.;Thymark, L.

Abstract: NA
Nitrate Nitrite Spectrophotometry Tecator

"Fluorimetric Flow Injection Determination Of Hydroperoxides In Foodstuffs"
Food Chem. 1993 Volume 46, Issue 3 Pages 301-305
Tom&aacute;s P&eacute;rez-Ruiz*, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s and Otilia Val

Abstract: A reliable and sensitive stopped-flow injection method is described for the determination of hydrogen peroxide, cumene hydroperoxide and tert-butyl hydroperoxide. It is based on the oxidation of leuco-phloxin to the fluorescent phloxin by hydroperoxide and haematin. Linear calibration graphs were obtained between 4 times 10^-6 and 8 times 10^-5 M, with a sampling-rate of 25 samples h-1. The detection limit, defined as three standard deviations of the reagent blank, was 1.5 times 10^-7 M. The usefulness of the method was tested in the determination of lipohydroperoxides in six commercial oil samples and of hydrogen peroxide in six milk samples of different levels of skimming. The results agreed closely with those obtained by the iodometric method.
Hydrogen peroxide Cumylhydroperoxide t-Butylhydroperoxide Fluorescence Method comparison Stopped-flow

"Flow Injection Titration Of Chloride In Food Products With A Silver Tubular Electrode Based On An Homogeneous Crystalline Membrane"
Food Chem. 1994 Volume 50, Issue 4 Pages 423-428
Isabel M. P. L. V. O. Ferreira, Jos&eacute;L. F. C. Lima* and Ant&oacute;nio O. S. S. Rangel

Abstract: Wine, milk, beer and vinegar were tested for chloride by pseudo-titration using FIA and potentiometric detection. Sample was injected into a carrier stream composed of 20 µM-AgNO3/0.1 M KNO3 and directed to a well-stirred mixing chamber. The decrease in the Ag concentration was monitored by an Ag tubular electrode with a crystalline membrane of AgS prepared by mixing equal volumes of equimolar (0.1M) AgNO3 and Na2S solution, filtering and drying at 100°C for 24 h. After grinding, the membrane discs were prepared by pressing 0.25 g of sensor at high pressure to produce discs 10 mm in diameter and 0.4 mm thick. The membrane was set into a support (details given). The operating characteristics of the tubular electrode were compared with conventional electrodes and found to be similar. The optimum Ag concentration in the carrier stream was 0.1 mM and optimum carrier flow rate was 8.1 ml/min. Calibration graphs were linear from 10^-500 mg/l, 100-1800 mg/l and 40-500 mg/l for wine, milk and beer, and vinegar, respectively. Sampling rate varied from 120-136 samples/h. A comparison with reference procedures showed maximum RSD of 6, 0.3 and 1% for wine and milk, beer, and vinegar, respectively.
Chloride Electrode Potentiometry Titrations Well stirred mixing chamber Optimization Indirect

"Drug Dissolution Studies In Milk Using The Automated Flow Injection Serial Dynamic Dialysis Technique"
Int. J. Pharm. 1986 Volume 33, Issue 1-3 Pages 125-136
P. Macherasa,*, M. Koupparisb,* and C. Tsaprounisa

Abstract: The application of flow injection serial dynamic dialysis (FISDD) technique to monitor dissolution studies in complex media is described. The method is based on the study of the kinetics of the simultaneous dissolution and dialysis processes. Commercial formulations of salicylamide, propantheline bromide, nitrofurantoin and acetaminophen were used to investigate the utility of the FISDD technique for studying the dissolution of drugs in low fat milk. The latter was utilized as a food simulating medium. Dissolution studies were also conducted in phosphate buffer of pH 6.5. In each case the FISDD system was coupled with the rotating basket apparatus. The determination of the dialyzable drugs was performed automatically by the FIA analyzer. A fully automated monitoring of dissolution of drugs in milk and buffer was achieved. In all cases the dissolution rate of drugs in milk was lower than the corresponding rate in the aqueous buffer. The potential significance of this system with respect to the in vitro study of dissolution of drugs in food simulating media is discussed. This system could be used either to reveal or explore food-drug and/or food-formulation interactions anticipated or observed in vivo.
Drugs Dialysis Dissolution rate

"Dissolution Of Four Controlled-release Theophylline Formulations In Milk"
Int. J. Pharm. 1987 Volume 36, Issue 1 Pages 73-80
P. Macherasa*, M. Koupparis* and E. Apostolellia

Abstract: The dissolution of 4 controlled-release theophylline formulations was studied in a low-fat (0.75%) milk and in a buffer of pH 6.5. A flow injection dialysis-UV spectrophotometric method was developed to determine the drug in the milk samples. Calibration curves were linear up to 250 µg/ml for theophylline and aminophylline and up to 450 µg/ml for choline theophyllinate, with detection limits of 18.5, 5.4, and 14.7 µg/ml, respectively, in a 5.0 mL minimum sample volume. Lower dissolution profiles in milk than in buffer were observed for 3 of the formulations examined. One theophylline formulation exhibited relatively similar dissolution profiles in both media. The use of milk as a food-stimulating medium in dissolution studies is suggested for the in vitro evaluation of the release drugs from controlled release-formulations. The proposed technique can be applied in such studies.
Theophylline Spectrophotometry Dissolution rate Dialysis

"Flow Injection System With Potentiometric Detection For The Determination Of Urea Content In Milks"
J. Agric. Food Chem. 1998 Volume 46, Issue 4 Pages 1386-1389
Jos&eacute; L. F. C. Lima, Cristina Delerue-Matos, and M. Carmo V. F. Vaz

Abstract: Two variant manifolds of a flow injection analysis (FIA) system are described for the determination of urea content in milks. This determination consists of the enzymatic reaction of urea with urease in which ammonium ion is formed. Ammonium is converted to ammonia by adding a NaOH solution and then led to a gas diffusion unit in which it diffuses to an acceptor channel (Tris/HCl, pH 7.5). Here, it is reconverted to ammonium ion and determined by a tubular configuration electrode sensitive to this ion. One of the FIA manifolds is based on the merging zones technique, whereas the other uses an immobilized enzyme. The results obtained were compared with those given by the Boehringer UV test and by the Official Method of Analysis of the Association of Official Analytical Chemists which can be applied to animal feed and adapted to the matrix studied. The relative deviation was less than 5%, and the precision of the developed methodologies considering RDS (%) was always less than 2%.
Urea Electrode Electrode Potentiometry Immobilized enzyme Gas diffusion Merging zones Volatile generation Method comparison Standard method

"Amperometric Bi-enzyme Based Biosensor For The Detection Of Lactose - Characterization And Application"
J. Chem. Technol. Biotechnol. 1990 Volume 49, Issue 3 Pages 255-265
Dorothea Pfeiffer, Edmundas V. Ralis, Alexander Makower, Frieder W. Scheller

Abstract: A 50 µL portion of 5% gelatin solution was mixed with β-galactosidase (I) from Escherichia coli (10.0 iu), Bifidobacterium adolescentes (4.0 iu) and Curvularia inaequalis (10.0 iu) and spread on 1 cm2 of polyethylene support (cf. Scheller et al., DD Patent 150 500, 1979). Additionally, cross-linking using polyvinylisocyanate (40 mL of 5% solution cm-2) was used (cf. Nentwig et al. DD Patent 277 888 4, 1985). The bi-enzyme membrane, obtained by combining a commercial glucose oxidase layer with a I layer between two cellulose membranes, was used to cover Clark-type electrodes which were then used manually or in a continuous-flow system at +600 mV vs. Ag - AgCl. The electrode was used to determine lactose (II) in milk, whey, baby foods, cottage cheese and bovine urine. The calibration graph was rectilinear for 25 mM II; the detection limit was 20 µM. In the analysis of milk, the coefficient of variation (n = 20) was 2%. Results compared well with those obtained by IR spectroscopy and photometry.
Lactose Amperometry Electrode Sensor Enzyme Membrane Calibration Detection limit Method comparison

"Determination Of Neutral Fat In Milk By Amperometric Flow Injection Analysis With Immobilized Enzyme Reaction"
J. Flow Injection Anal. 1991 Volume 8, Issue 2 Pages 136-147
Seiichi Higuchi, Kiyoshi Matsumoto and Yutaka Osajima

Abstract: The method is based on hydrolyis of neutral fat by triacylglycerol lipase (I) - carboxylesterase (II) and glycerol dehydrogenase (III)-catalyzed oxidation of glycerol, after which the NADH produced is monitored amperometrically. The cited sensor is made from I and II co-immobilized on aminopropyl-substituted controlled-pore glass and from III immobilized on Amino-Cellulofine. For application, an emulsion of milk in 6% bovine serum albumin solution is diluted with buffer solution prepared from 0.125 M carbonate buffer of pH 9.5 containing 30 mM (NH4)2SO4 and 1% of Triton X-100, and a portion is injected into the analyzer. (diagram given) for the determination of neutral fat at 25°C with the above-mentioned buffer as carrier stream at 1 mL min-1. When determining triolein, the relationship between response and concentration. is rectilinear for 0.0128 to 0.0853%; the coefficient of variation was 0.87%. Results were comparable with those obtained by the Wako triglyceride G-test method.
Triolein Fatty acids Amperometry Buffer Controlled pore glass Immobilized enzyme pH Triton X Surfactant

"Routine Analysis Of Acetone In Milk By Flow Injection Analysis"
Kiel. Milchwirtsch. Forschungsber. 1986 Volume 38, Issue 3 Pages 205-213
Diekmann, L.;Pabst, K.;Gravert, H.O.

Abstract: In milk samples from 109 cows of the experimental herd Schaedtbek, and 6677 cows in 162 dairy herds nearly 43,000 acetone [67-64-1] measurements were made by flow injection analysis (FIA). Untreated and preserved milk samples were pumped in exact dosages into a diffusion cell with a Teflon membrane, where the acetone diffuses into a reaction stream with hydroxylamine and methyl orange, and the reaction is recorded photometrically. With the equipment of Tecator Co. about 100 determinations/h could be made.
Acetone Spectrophotometry Gas diffusion Tecator

"Determination Of Nitrites And Nitrates In Milk And Its Products Using Flow Injection Analysis"
Latte 1988 Volume 13, Issue 5 Pages 410-411
Munksgaard, L.L.;Thymark, L.

Abstract: International Dairy Federation methods for the determination of nitrites and nitrates in dairy products were adapted to flow injection analysis (FIA). Samples were defatted and deproteinized, nitrates were reduced to nitrites, and the nitrites were reacted with sulfanilamide and N-naphthylethylenediamine to form a colored product absorbing at 538 nm. The limit of detection for both nitrites and nitrates was <1 mg/kg. At 10 mg/kg the recovery of nitrates was 90-102% and the relative standard deviation was 2-11%. FIA permitted anal. of ~80 samples per day. FIA was superior to manual anal. in terms of all measures of performance. (SFS)
Nitrate Nitrite Spectrophotometry Method comparison

"Automated Determination Of Nitrate And Nitrite In Milk And Dairy Products By Continuous-flow Analysis"
Milchwissenschaft 1979 Volume 34, Issue 7 Pages 414-416
Nijhuis, H.;Heeschen, W.;Bluethgen, A.

Abstract: Nitrate is reduced to nitrite by means of an organic hydrazine sulfate solution Nitrite reacts with sulfanilamide and N-(-1-naphthyl)ethylendiamine-2HCl in an azo reaction. The resulting color is measured at 520 nm. For the determination of nitrate and nitrite contents in 1 sample the anal. must be carried out twice: first without hydrazine solution for the determination of the total amt. of nitrate and nitrite. The nitrate content is calculated from the difference of both measurements. The relative standard deviation is 0.66%. The recovery is 100% for nitrite and 99.7% for nitrate. Preservation of milk samples is possible by cooling (up to 3 days at 5°C) or freezing (up to 14 days at -20°C. (SFS)
Nitrite Nitrate Spectrophotometry Speciation

"Determination Of Chloride Ion In Milk By Flow Injection Spectrometer With A Dialyzer"
Shipin Yu Fajiao Gongye 1990 Volume 5, Issue 2 Pages 76-77
Fan Shihua

Abstract: The Van Staden method was adapted for determination of chloride in milk by flow injection spectrophotometry with a dialyzer. Chloride was dialyzed from milk into a chamber to react with Hg(SCN)2 and Fe(III) to form Fe(SCN)2+. Fe(SCN)2+ was determined by spectrophotometry at 480 nm. Recovery was 97-108%.
Chloride Spectrophotometry Dialysis Indirect

"Ion-exchange Chromatographic Determination Of Lactulose And Epilactose In The Presence Of Lactose And Other Carbohydrates In Milk And Milk Products"
Z. Lebensm. Unters. Forsch. 1985 Volume 181, Issue 5 Pages 408-411
Ernst H. Reimerdes und K. -D. Rothkitt

Abstract: The fat and protein from heated milk and reconstituted milk powder are removed by treatment with Carrez I and II solution and filtration. The carbohydrates in the filtrates are determined on a column (7.5 cm x 6 mm) of Dionex DA-X8-11 with a pre-column (5 cm x 9 mm) of Dowex 1-X4, and with gradient elution with (A) 0.15M, 0.2M, 0.4 M (each of pH 8.0), 0.8 M (pH 8.3) and 0.15 M (pH 8.0) borate buffers or (B) 0.2M, 0.3 M (each of pH 8.0), 0.8 M (pH 8.3) and 0.2 M (pH 8.0) borate buffers. Post-column derivatization is effected with Cu(I) bicinchoninate and detection is at 570 nm. By using system A, lactulose and epilactose were determined, even in the presence of large amounts of lactose; use of buffer system B permitted detection of lactulose in the presence of fructose. In addition, other carbohydrates, e.g., ribose, mannose, galactose and glucose, can be determined simultaneously.
Lactulose Epilactose HPIC Spectrophotometry Post-column derivatization

"D- And L-lactate Determination In Dairy Products: Presentation Of A Fast Automated Analysis System"
Z. Lebensm. Unters. Forsch. 1995 Volume 201, Issue 6 Pages 537-540
Thomas Becker, Hanns-Ludwig Schmidt and Erika Lechner

Abstract: A flow injection system is presented, which is versatile, automated and has an integrated enzyme system. Its efficiency at determining D- and L-lactate separately in dairy products is compared with the officially used reference method (DIN 10335). By means of a mathematical elimination of matrix effects, the pretreatment steps can be clearly reduced. As a result of the immobilization of the enzymes, an appropriate automation software and an adaptation of the system developed to the given medium, the analysis could be performed within 5 min and was distinctly cheaper than alternative methods. The values determined in 15 different dairy products deviated from those of the reference method by 3% at a maximum. (21 References)
d-Lactate l-Lactate Spectrophotometry Immobilized enzyme Standard method

"Determination Of Milk Urea By Flow Injection Analysis"
Zentralbl. Veterinarmed. A 1986 Volume 33, Issue 1 Pages 53-58
G. Andersson, L. Andersson, G. Carlstr&ouml;m

Abstract: A method for flow injection analysis of urea in milk is described. The sample is introduced into a current of urease solution in which urea is enzymatically split into carbon dioxide and ammonia. After adding sodium hydroxide, the free ammonia diffuses through a teflon membrane into a stream of phenol red solution. The change of color in the indicator solution caused by the ammonia-induced pH alteration is measured in a flow photometer. The accuracy of the method is shown to be good, and the capacity is about 100 samples per hour.
Urea Spectrophotometry Indirect Gas diffusion Teflon membrane