University of North Florida
Browse the Citations
-OR-

Contact Info

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

View Stuart Chalk's profile on LinkedIn

Feed

Classification: Agricultural -> feed

Citations 45

"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

"Flow Injection Determination Of Ammonia In Kjeldahl Digests By Gas Diffusion And Conductometry"
Anal. Chim. Acta 1987 Volume 193, Issue 1 Pages 19-27
Celio Pasquini and Lourival Cardoso de Faria

Abstract: The digest (100 µL) was injected into a stream of water (1.6 mL min-1) and mixed with a stream of 2 M or 3 M NaOH containing 1% of EDTA (1.6 mL min-1) at ambient temperature The resulting stream was passed (3.2 mL min-1) to a diffusion cell and the NH3 was allowed to diffuse through a PTFE membrane into a second water stream, which was passed into a flow cell for conductometric determination of NH3. The manifold was constructed from polyethylene tubing (0.8 mm i.d.). There was no interference from 1.25 M H2SO4, 7 to 30 g L-1 of K2SO4, 6 mM Ca(II), Fe(III), Al(III), Mg, Zn(II), Cu(II) or Se(IV) or 3 mM Hg(II) in the determination of 2 mM or 3 mM NH3. The method was applied to samples of vegetables, animal feeds and fertilizers, and results agreed with those by a distillation - titration method. In the determination of 1 to 4% of N the coefficient of variation (n = 5) was 1%. The sampling rate was ~100 h-1.
Ammonia Conductometry Gas diffusion Interferences Method comparison Teflon membrane Kjeldahl

"Automated Flow Injection Determination Of Sulfonamides By The Bratton-Marshall Reaction For Clinical Analysis, Assays And Dissolution Studies Of Formulation"
Anal. Chim. Acta 1988 Volume 204, Issue 1-2 Pages 271-283
M. A. Koupparis and P. I. Anagnostopoulou

Abstract: Two flow injection manifolds are described based on the Bratton - Marshall reaction, one for 2 to 20 mg L-1 of sulfonamide and the other for 0.5 to 5 mM. N-(1-Naphthyl)ethylenediammonium chloride is used as chromogenic reagent with detection at 545 nm. The method was used in the determination of sulfonamides in serum, urine, feeds and formulations, and for automated dissolution studies of tablets. The detection limit was 0.6 to 1.1 mg l-1, and the coefficient of variation was <0.5% (n = 10). The analysis rate was 72 samples h-1. The pseudo-titrimetric method gave a 1.3% mean difference from the HPLC technique.
Sulfonamides Clinical analysis Spectrophotometry Dissolution rate Method comparison Chromogenic reagent

"Flow Injection System For The Amperometric Determination Of Xylose And Xylulose With Co-immobilized Enzymes And A Modified Electrode"
Anal. Chim. Acta 1988 Volume 213, Issue 1-2 Pages 139-150
E. Dominguez and B. Hahn-H&auml;gerdal, G. Marko-Varga and L. Gorton

Abstract: A purpose-built flow injection analysis system was constructed that incorporated a 25 µL reactor containing xylose isomerase (omitted in determination of xylose alone), aldose 1-epimerase and glucose dehydrogenase immobilized on CPG-10 glass beads (37 to 74 µm diameter; 51.5 nm pore size). The NADH produced from NAD+ incorporated in the carrier solution [0.1 M phosphate buffer (pH 7.0) containing Mg] was detected electrochemically with use of a dye-modified graphite electrode in a wall-jet configuration (cf. Appleqvist et al., Anal. Abstr., 1985, 47, 12D151). Up to 30 determinations per hour were possible and calibration graphs were rectilinear for up to 2 mM xylose or -xylulose.
Xylose Xylulose Amperometry Electrode Sample preparation Controlled pore glass Extraction Immobilized enzyme

"Flow Injection Spectrophotometric Determination Of Lysine In Feed Samples"
Anal. Chim. Acta 1993 Volume 281, Issue 3 Pages 593-600
J. Saurina and S. Hern&aacute;ndez-Cassou

Abstract: Extracts of commercial feeds (prep. described) were injected into a stream of water (0.75 ml/min) which was merged with pre-mixed streams of 0.1 M Na2CO3/0.075 M NaOH buffer of pH 9.7 (0.6 ml/min) and 1 mM sodium 1,2-naphthaquinone-4-sulfonate in 0.1 M HCl (0.75 ml/min), and carried to a reaction coil (10 m x 0.35 mm) immersed in a water bath at 80°C (diagram given). Detection was at 303 or 480 nm, or from 390-590 nm at 2 nm intervals. Spectra (averages of five individual spectra) were recorded every 3 s and data were processed by computer. With detection at 480 nm, the calibration graph was linear from 1.9 µM- (detection limit) to 0.15 mM lysine and the within-day RSD was 0.8%. The method was more sensitive at 303 nm but the precision was worse. At 480 nm, only hydroxylamine and primary and secondary amino-compounds (10-fold excess) interfered (at 0.1 mM lysine). For feed samples, multivariate calibration by principal component regression and partial least squares regression was used to make the method specific for lysine. Results agreed well with those obtained using a standard AutoAnalyzer procedure.
Lysine Spectrophotometry Interferences Multivariate calibration Partial least squares

"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

"Calibration Methods For Determination Of Ammonium And Excess Acid In Kjeldahl Digests By Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 343, Issue 3 Pages 183-190
Robert Tryzell and Bo Karlberg*,*

Abstract: Calibration methods were evaluated for determining ammonium in Kjeldahl digests by flow injection spectrophotometry. The FIA method was based on the separation of gaseous NH3 from a NaOH carrier stream using a gas diffusion unit fitted with a Celgard 2400 membrane. The NH3 was collected in an indicator mixture of bromcresol purple/bromthymol blue/cresol red and the absorbance was measured at 590 nm. The Kjeldahl digests were prepared digesting a 1 g sample with 7 g K2SO4, 0.8 g CuSO4.5H2O and 12 mL H2SO4 for 1 h at 420°C. Univariate calibration based on peak areas allowed accurate and precise determination of ammonium when the injection volume was small, viz., Calibration by partial least squares using the entire response curve (1098 data points) allowed both the ammonium and the excess acid to be determined from a single sample injection. Calibration standards containing five concentration levels of ammonium (40, 100, 200, 300 and 400 ppm) and six levels of H2SO4 (0, 0.105, 0.248, 0.330, 0.413 and 0.495 mol/l) were used. The lowest root mean square error of prediction ( The PLS calibration method was used to determine the protein content of feed.
Protein Ammonium Acids Spectrophotometry Chemometrics Multicomponent Gas diffusion Partial least squares Celgard Kjeldahl

"Amperometric Lysine Bio-probes Analysis In Feeds"
Talanta 1993 Volume 40, Issue 8 Pages 1301-1306
M. G. Lavagnini, D. Moscone and G. Palleschi*, D. Compagnone, C. Cremisini

Abstract: To prepare the biosensor probes, on an inverted electrode jacket were placed, in order, a cellulose acetate protective membrane, an Immobilon membrane containing immobilized lysine oxidase, and a polycarbonate membrane to exclude proteins and bacteria (details given). A Pt electrode (polarized at +650 mV vs. Ag/AgCl) was inserted into the jacket, which was secured with an O-ring and filled with 0.1 M KCl. The best response was attained by immobilizing the enzyme using a BSA/glutaraldehyde procedure (c.f. Villata et al., Anal. Chim. Acta, 1991, 245, 63) and by using a 0.8 µm polycarbonate membrane. The optimum pH was 5-7.5 and the best compromise temperature was 25°C. The calibration graph was linear from 0.5 µM (detection limit) to 1 mM lysine with a RSD of 5%. Arginine and ornithine interfered. The probe lost 70% of its activity after 10 days but was then stable for >90 days; it could be used for >300 analyzes. The probe was applied in the continuous-flow and FIA (using an electrochemical wall-jet cell and a flow rate of 0.2 ml/min) of hydrolysates (prep. given) of animal feed; sample throughput was 12/h and 20/h, respectively, and results correlated well with those of HPLC.
Lysine Amperometry Sensor Interferences

"Use Of Non-segmented High-speed Continuous-flow Analysis For The Determination Of Calcium In Animal Feeds"
Analyst 1978 Volume 103, Issue 1224 Pages 296-299
W. D. Basson and J. F. Van Staden

Abstract: Calcium is a basic component in animal feeds and its level plays an important role in livestock rations for optimum animal performance. The ever increasing number of samples presented for calcium analyzes has led to an increasing demand for rapid and precise chemical procedures. This paper describes the use of a non-segmented high-speed continuous flow system for this purpose. One of us(5) has discussed the theoretical advantages of non-segmented systems, described suitable equipment and mentioned some of the precautions to be taken in using it. The method permits a faster sampling rate than segmented continuous flow, in the present case about 300 per hour.Most continuous flow analytical procedures use a procedure similar to that of Kessler and Wolfman,(1) with cresolphthalein complexone reagent and diethylamine - sodium acetate as a base component. This method was improved by Gitelman(2) who eliminated interference from magnesium by adding quinolin-8-ol. Roach(3) reported the application of cresolphthalein complexone and diethylamine - sodium acetate as a base and a sampling rate of 60 samples per hour for the determination of calcium in animal feeds. This method was modified by Moorehead and Biggs4 by replacing the toxic, volatile diethylamine with the more stable non-toxic 2-amino-2-methylpropan-1-ol reagent as a base solution. In the work described here, this method has been adapted for the high-speed determination of calcium in animal feeds in the range 0.5--5% of calcium at a rate of 300 samples per hour.
Calcium Spectrophotometry Method comparison

"Automated Catalytic Method For The Routine Determination Of Molybdenum In Plant Materials"
Analyst 1979 Volume 104, Issue 1239 Pages 552-559
B. F. Quin and P. H. Woods

Abstract: Molybdenum is determined by its catalytic effect on the liberation of iodine from iodide by hydrogen peroxide. The detection limit (twice the standard deviation of the blank) is 0.01 p.p.m. in plant material, using a 0.25-g sample. Interference from iron is eliminated by preventing any reduction to iron(II) before complexation with fluoride. High concentrations of salts, other metals and phosphate do not interfere, and agreement with established routine methods is very good.
Molybdenum Catalysis

"Simultaneous High Performance Liquid Chromatographic Determination Of Monensin, Narasin And Salinomycin In Feeds Using Post-column Derivatization"
Analyst 1985 Volume 110, Issue 11 Pages 1283-1287
W. John Blanchflower, Desmond A. Rice and John T. G. Hamilton

Abstract: Samples (20 g) are extracted with methanol (50 ml) and the solution are analyzed on a column (25 cm x 4.6 mm) of Partisil 5ODS-3 reversed-phase material, with methanol - water - anhydrous acetic acid (940:59:1) as the mobile phase (0.7 mL min-1). The eluate is mixed with a solution comprising 10% vanillin and 2% H2SO4 in methanol, in a reaction coil maintained at 70°C; the absorption of the color produced is measured at 520 nm. The limits of detection are 0.25 mg kg-1 for monensin and 0.5 mg kg-1 for narasin and salinomycin with recoveries ranging from 95 to 108% at concentration. levels between 2.5 and 100 mg kg-1. The coefficient of variation are between 0.91 and 3.6% (n = 5 or 10) in the range 3.81 to 99.37 mg kg-1.
Monensin Narasin Salinomycin HPLC Spectrophotometry Post-column derivatization Heated reaction

"Simultaneous Determination Of Several Amino Acids With Multivariate Calibration Methods By Using A Continuous-flow System"
Analyst 1995 Volume 120, Issue 2 Pages 305-312
J. Saurina and S. Hern&aacute;ndez-Cassou

Abstract: A method for the resolution of mixtures of four amino-acids, viz., phenylalanine, lysine, tryptophan and proline, is described. A stream (0.4 ml/min) of 1 mM sodium 1,2-naphthoquinone-4-sulfonate in 0.1 M HCl was mixed with a stream (0.3 ml/min) of 0.1 M Na2CO3/0.75 M NaOH buffer of pH 10. The resulting solution was merged with the sample solution (0.4 ml/min) and the mixture was passed through a PTFE reaction coil (10 m x 0.35 mm i.d.) maintained at 70°C. Absorption spectra were recorded from 290-590 nm in steps of 1 nm. Two multivariate calibration procedures, viz., principal-component regression and partial-least-squares regression, were applied to the spectra (details given). Partial-least-squares regression provided the most accurate predictions of the amino-acid composition. The method was used to determine several amino-acids in extracts of commercial feeds. The results agreed with those obtained with the standard amino-acid autoanalyzer. procedure.
Amino Acids Lysine Phenylalanine l-Proline Tryptophan Spectrophotometry Sample preparation Method comparison Multivariate calibration Heated reaction

"Consecutive Determination Of Nitrogen, Phosphorus And Calcium In Animal Feeds On A Single Channel Flow Injection Analyzer With A Common Analytical Manifold"
Fresenius J. Anal. Chem. 1982 Volume 311, Issue 1 Pages 23-26
W. D. Basson

Abstract: A procedure is described for the consecutive determination of N, P and Ca in animal feeds by means of a single-channel flow injection analyzer with common manifold. The sample is decomposed with K2SO4, HgO and H2SO4 and is directly injected into the system after dilution. The following reagents are employed: phenol/hypochlorite for N (protein), molybdate/ascorbic acid for P and cresolphthalein complexone/aminomethylpropanol for Ca. Comparison with the results of the Kjeldahl, vanadate and AAS methods, respectively, revealed good agreement.
Calcium Nitrogen Phosphorus Spectrophotometry

"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

"Rapid Determination Of Aflatoxin B1 In Dutch Feeding-stuffs By High Performance Liquid Chromatography And Post-column Derivatization"
J. Chromatogr. A 1983 Volume 282, Issue 1 Pages 457-462
L. G. M. Th. Tuinstra and W. Haasnoot

Abstract: Pre-treatment involves extraction with CHCl3 and clean-up by two-directional t.l.c. on silica gel. Extracts are spotted along the middle line of a t.l.c. plate, and development is effected in one direction with ethyl ether, then, after the area of migration has been cut away, in the opposite direction with CHCl3 - acetone (22:3) containing 0.2% of water to cause the aflatoxin to migrate. Acetone - CH2Cl2 (2:3) is used to extract the aflatoxin from the silica gel for subsequent HPLC analysis on Microsphere C18 at 60°C with aqueous 30% acetonitrile as mobile phase. The eluate is mixed with saturated aqueous iodine and, after reaction at 60°C, aflatoxin B1 is determined fluorimetrically at >420 nm (excitation at 360 nm). With the post-column reaction, sensitivity is improved 50-fold, enabling <1 ppb to be detected.
Aflatoxin B1 HPLC Fluorescence Heated reaction Post-column derivatization

"Fluorimetric Determination Of Menadione [menaphthone] Sodium Bisulfite (vitamin K3) In Animal Feed And Pre-mixes By High Performance Liquid Chromatography With Post-column Derivatization"
J. Chromatogr. A 1984 Volume 301, Issue 2 Pages 441-447
A. J. Speek, J. Schrijver and W. H. P. Schreurs

Abstract: Menaphthone sodium bisulfite(I) was extracted from the feed with aqueous 40% ethanol and converted into menaphthone(II) by treatment with tannin; II was then extracted into hexane for determination on a column (25 cm x 4.6 mm) of ODS-Hypersil (5 µm) by elution isocratically at 0.6 mL min-1 with 40% ethanol. The eluate was passed to a post-column reactor for reduction of II with NaBH4 and the product was measured fluorimetrically at 425 nm (excitation at 325 nm). The concentration. of I in the original sample was calculated from peak heights relative to a standard solution A rectilinear calibration graph was obtained over the range 0.02 ppm (the detection limit) to 20%. At >15 ppm, the results agreed well with those by an established colorimetric method, but for lower concentration. the HPLC method is preferred because of its higher specificity and sensitivity. For six analyzes of a rat-breeding diet, the mean recovery was 94.4% and the coefficient of variation was 6%.
Menadione HPLC Fluorescence Method comparison Post-column derivatization Reactor

"Sample Cleanup And Post-column Derivatization For The Determination Of Aflatoxin B1 In Feedstuffs By Liquid Chromatography"
J. Chromatogr. A 1987 Volume 396, Issue 1 Pages 389-394
W. A. Traag, J. M. P. van Trijp, L. G. M. Th. Tuinstra, and W. Th. Kok

Abstract: Ground cattle feed (25 g) was extracted with CHCl3 in the presence of water and Celite, the mixture was filtered, and the filtrate was passed through a Sep-Pak Florisil mini-column. After the column was rinsed with CHCl3 and methanol, the aflatoxins were eluted with aqueous 90% acetone. The acetone was evaporated off, water was added and the solution was passed through a Sep-Pak C18 mini-column. The column was eluted with aqueous 15% acetone and a 250 µL aliquot was injected on to a column (10 cm x 3 mm) of LiChrosorb RP-18 (5 µm). The mobile phase was water - methanol - acetonitrile (13:7:4) at 0.5 mL min-1. Post-column derivatization was performed by addition of 1 mM KBr and 1 mM HNO3 to the mobile phase and electrochemical generation of Br. Fluorescence detection was performed at >420 nm (excitation at 360 nm). The solid-phase cleanup showed improved reproducibility, and the simplified derivatization with Br gave the same detection limit (~10 µg kg-1) for aflatoxin B1 as the iodine method.
Aflatoxin B1 HPLC Fluorescence Electrochemical reagent generation Post-column derivatization

"Detection Of Zearalenone In Cereal Extracts Using High Performance Liquid Chromatography With Post-column Derivatization"
J. Chromatogr. A 1991 Volume 588, Issue 1-2 Pages 47-52
Michael T. Hetmanski* and Keith A. Scudamore

Abstract: Sample extracts were prepared according to previous techniques (c.f., J. Assoc. Off. Anal. Chem., 1979, 62, 1265 and Food Addit. Contam., 1989, 6, 35) and analyzed by HPLC on a column (25 cm x 4.6 mm) of Spherisorb ODS-1 (5 µm) with a mobile phase (1 mL min-1) of aqueous 80% methanol. The eluate was derivatized in a PTFE coil with 0.25 M aluminum chloride solution at ~50°C and zearalenone and zearalenol were detected fluorimetrically at 440 nm (excitation at 285 nm). The described methods led to a 5-fold increase in the fluorescence response of the cited mycotoxins without significantly affecting the level of background interference from co-extractives from cereal and animal feed samples.
Zearalenone HPLC Fluorescence Column Interferences Post-column derivatization

"Multimycotoxin Detection And Cleanup Method For Aflatoxins, Ochratoxin And Zearalenone In Animal Feed Ingredients Using High Performance Liquid Chromatography And Gel-permeation Chromatography"
J. Chromatogr. A 1993 Volume 629, Issue 2 Pages 229-235
Catherine Dunne, Mary Meancy and Malcolm Smyth, Louis G. M. Th. Tuinstra

Abstract: A finely ground sample (25 g) of animal feed was shaken for 30 min with Celite, 1 M HCl and CH2Cl2 and the mixture was filtered. The filtrate was evaporated to near dryness and the residue was reconstituted in CH2Cl2 - ethyl acetate containing formic acid. A portion of the filtered extract was then cleaned up by gel-permeation chromatography on a glass column (6 cm x 6 mm) packed with Bio-Beads SX-3 gel. Elution was effected at 0.3 mL min-1 with CH2Cl2 - ethyl acetate - formic acid (499:499:2), and the eluate fraction collected between 25 and 45 min was extracted by shaking with water. The lower organic layer was dried by passage through anhydrous Na2SO4 and evaporated to near dryness. The residue was sonicated with aqueous 15% acetone and analyzed by HPLC on a column of Chromsphere RP-C18, with gradient elution with water - methanol - acetonitrile (13:7:4) containing 1 mM HNO3 and 1 mM KBr, and 0.01 M H3PO4 - acetonitrile (1:1) (program given). Post-column derivatization was performed with Br produced electrochemically from KBr in the mobile phase, followed by fluorimetric detection. Aflatoxins B1, B2, G1 and G2, ochratoxin A and zearalenone (I) were determined in animal feed including maize, palm and wheat with recoveries of >81% and limits of detection of 0.6 ng for I and 0.05 ng for the other analytes.
Mycotoxins Aflatoxin B1 Aflatoxin B2 Aflatoxin G1 Aflatoxin G2 Ochratoxin A Zearalenone HPLC Fluorescence Post-column derivatization Electrochemical reagent generation

"Determination Of Amino-acids By Ion-pair Liquid Chromatography With Post-column Derivatization Using 1,2-naphthoquinone-4-sulfonate"
J. Chromatogr. A 1994 Volume 676, Issue 2 Pages 311-319
J. Saurina and S. Hern&aacute;ndez-Cassou*

Abstract: Amino-acids were analyzed by ion-pair HPLC on a column (15 cm x 4.6 mm) of Spherisorb ODS-2 (5 µm) with gradient elution (0.8 ml/min) of 20 mM phosphoric acid/20 mM sodium dihydrogen phosphate/15 mM SDS as eluent A and (25 mM phosphoric acid/25 mM sodium dihydrogen phosphate - 18.5 mM SDS)/propan-2-ol (4:1) as eluent B; 0% B (held for 10 min) to 100% B over 75 min to 0% B (held for 2 min) over 3 min. The column outlet was coupled online to a two channel derivatization system. The reagents 1,2-naphthoquinone-4-sulfonate and 15 mM sodium hydrogen carbonate/0.185 M sodium carbonate were mixed and merged with the column eluate in a reaction coil (4 m x 1.1 mm) at 65°C and spectrophotometric detection at 305 nm. The calibration graph was linear up to 32 nmol for lysine with a detection limit of 0.09 nmol. For the nine amino-acids tested, the repeatability was >4%, reproducibility was >5% and the detection limits were 0.09-0.33 nmol. The method was applied to the determination of amino-acids in animal feed and powdered milks.
Amino Acids HPLC Spectrophotometry Post-column derivatization Heated reaction

"High Performance Liquid Chromatographic Determination Of Clenbuterol And Cimaterol Using Post-column Derivatization"
J. Chromatogr. B 1991 Volume 564, Issue 2 Pages 537-549
Dirk Courtheyn*, Carlo Desaever and Roland Verhe

Abstract: Animal tissues, faeces and feeding-stuffs were extracted with dilute 0.5 M HCl saturated with ethyl acetate; the resulting extracts or liquid samples, e.g., urine, plasma, blood and bile were purified on Chem Elut CE 120 columns and eluted with toluene - CH2Cl2. The eluate was mixed with 0.1 M HCl, ultrasonicated and centrifuged before a portion of the mixture was analyzed by HPLC on a column (15 cm x 4.6 mm) of Nova-Pak C18 (4 µm) with 25 mM sodium dodecyl sulfate and 0.02 M anhydrous acetic acid buffer of pH 3.5 containing 1 M NaOH - acetonitrile (53:47) as mobile phase (1.3 mL min-1). The eluate was derivatized with use of three reagents (details given) before the absorbance was measured at 537 and 493 nm for cimaterol and clenbuterol, respectively. Detection limits for liquid and solid samples were 0.1 ng mL-1 and 0.2 ng g-1, respectively. Results agreed well with those obtained by high performance TLC and GC - MS.
Cimaterol Clenbuterol HPLC Spectrophotometry Buffer Column Detection limit pH Post-column derivatization

"Flow Injection Analysis Of Feed And Premix For Monensin And Salinomycin"
Anal. Sci. 1987 Volume 3, Issue 5 Pages 441-444
Y. SUZUKI, N. ARAI and M. OKAMOTO

Abstract: Samples (5 g) of feed or pre-mix were extracted with 100 mL of ethanol for 15 min and, after filtration, the filtrate was analyzed by flow injection spectrophotometry. Sample solution (100 µL) was injected into the carrier solution (ethanol; 0.5 mL min-1), this stream was mixed with the reagent solution (0.5 mL min-1) consisting of ethanolic 1% H2SO4 - 1% 4-dimethylaminobenzaldehyde, and the resulting stream was allowed to react in a coil at 78°C. The absorbance of the effluent was measured at 578 nm for monensin and 600 nm for salinomycin. Calibration graphs were rectilinear for 2 to 10 ppm for both analytes. Recoveries ranged from 96.9 to 103.2%. Analysis time was ~20 min.
Monensin Salinomycin Spectrophotometry Heated reaction Optimization

"Selective Biosensing Of L-lysine By A Low-temperature Flow Injection Technique Using An Immobilized Lysine Oxidase Reactor"
Anal. Sci. 1996 Volume 12, Issue 1 Pages 87-90
R. L. C. CHEN, M.-H. LEE and K. MATSUMOTO

Abstract: A method for the determination of L-lysine (lysine; I) using a H2O2 electrode as a biosensor device in an enzymatic FIA system is presented and used to analyze the concentration of I in fish feed. Squid or white-fish meal (10 g) was suspended in 100 mL 0.1 M phosphate buffer of pH 7.3 (buffer A) and the suspension was incubated with protease (10 000 U Denazyme AP) for a definite time. The reaction mixtures were incubated at 90°C for 10 min and centrifuged at 11 000 g for 1 h. The supernatants were filtered (0.45 µm) and a 20 µL portion of the filtrate was injected into a carrier stream of buffer A (3 ml/min) of an automated flow injection system (schematic shown). A computer-controlled switching valve downstream allowed the carrier to pass alternately through a lysine oxidase (LO)-immobilized aminopropyl-glass (APG, pore size 70 nm, 80-120 mesh) enzyme reactor and aa identical reactor containing APG only. The H2O2 (I) produced by the enzyme reactor was detected electrochemically at 10°C. The calibration graph was linear up to the mM range of I and the detection limit was of the order of tens of µM. The RSD (n = 8) was 1.45% for 0.5 mM I. Results agreed well with those obtained by HPLC.
l-Lysine Amperometry Electrochemical analysis Sensor Method comparison Immobilized enzyme Buffer Computer Glass beads Valve

"Determination Of Terbium By Flow Injection Analysis And Fluorescence"
Acta Cient. Venez. 1982 Volume 33, Issue 2 Pages 99-102
Burguera, J.L.;Burguera, M.;Gallignani, M.

Abstract: Tb (1 x 10^-2 - 100 mg mL-1) is determined by measuring the fluorescence of the ternary complex Tb(III)-EDTA-sulfosalicylic acid at 545 nm, and an excitation wavelength of ~320 nm. The flow injection analysis technique is used for monitoring the fluorescent reaction. A sample throughout of 90 anal. per h is possible and the relative standard deviation is <4.0% for ~80 pg Tb in 8 uL samples. No interferences was noted from 30-fold excesses of 10 metal ions. (SFS)
Terbium Fluorescence Interferences

"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

"Spectrophotometric Determination Of Trace Iodide By Flow Injection Analysis"
Fenxi Huaxue 1996 Volume 24, Issue 6 Pages 720-723
Wang, P.;Shi, S.J.

Abstract: Portions of standard iodide (I) solution were injected into a flow injection analyzer. (schematic shown) and treated with a mixture of 1% bromine and 2% H3PO4 in water in a reaction coil (5 cm x 0.7 mm i.d.). The mixed solution was treated with aqueous 6% sulfosalicylic acid in a second coil (94 cm x 0.7 mm i.d.) and the absorbance of the colored product formed was measured at 580 nm. The calibration graph was linear up to 1 mg/l I. The RSD was 3.3%. Sampling frequency was 80 runs per h. There was little interference. The method was applied to the analysis of iodine-containing tablets, table salt, animal feed and kelp, with recovery of 90-97.5%.
Iodide Spectrophotometry Interferences

"Comparison Of Six Methods Of Analysis For The Determination Of Aflatoxin B1 In Feeding-stuffs Containing Citrus Pulp"
Food Addit. Contam. 1988 Volume 5, Issue 3 Pages 321-332
Van Egmond HP, Paulsch WE, Sizoo EA

Abstract: A method is described for the determination of aflatoxins B1, B2, G1 and G2 at levels of ~13, ~5, ~10 and ~4 µg kg-1, respectively, in feeding-stuffs containing citrus pulp. The sample is extracted with CHCl3 and the extract is cleaned up on a Sep-Pak Florisil cartridge followed by a Sep-Pak C18 cartridge. The final eluate (aqueous acetone) is analyzed by HPLC with a Chrompack stainless-steel column (15 cm x 4.6 mm) of LiChrosorb 5 RP 18 (5 µm) and a mobile phase (1 mL min-1) of water - methanol - acetonitrile (13:7:4); detection was by fluorescence at 430 nm (excitation at 360 nm) after post-column derivatization with iodine. The recovery of aflatoxin B1 was 86% and the detection limit was ~1 µg kg-1. The method is preferred over five other methods, e.g., the official European Commission method (Off. J. Eur. Communities, 1976, L102, 8) and that of Tuinstra and Haasnoot (Anal. Abstr, 1984, 46, 7G21).
Aflatoxin B1 HPLC Fluorescence Method comparison Post-column derivatization

"A Simple Quantitative HPLC Method For Determination Of Aflatoxins In Cereals And Animal Feedstuffs Using Gel-permeation Chromatography Clean-up"
Food Addit. Contam. 1989 Volume 6, Issue 1 Pages 35-48
Hetmanski MT, Scudamore KA

Abstract: A 25-g powdered sample was shaken for 30 min with Hyflo Supercel filter aid (13 g), water (12.5 ml) and CH2Cl2 (125 ml), and the mixture was filtered. The residue was washed with CH2Cl2 (3 x 25 ml), and the combined filtrate and washings were evaporated to incipient dryness under N. The residue was dissolved in 10 mL of CH2Cl2 - hexane (3:1), and a 5 mL aliquot was cleaned up on a column (50 cm x 2.5 cm) of Bio-Beads S-X3; the column was washed (4 mL min-1) with CH2Cl2 - hexane (3:1), and 5 mL fractions were collected. Fractions 17 to 22 were evaporated under N, the residue was re-evaporated from CH2Cl2 and a solution of the residue in aqueous 50% acetonitrile (2 ml) was analyzed by HPLC on a column (25 cm x 4.6 mm) of Spherisorb ODS 1 (5 µm). The mobile phase (0.75 mL min-1) was water - acetonitrile - methanol (6:3:1), and fluorescence detection at 440 nm (excitation at 360 nm) was used after post-column derivatization with iodine. Recoveries of aflatoxins from wheat, maize and feeds were 80, 70 and 65%, respectively. The determination limit was 1 µg kg-1.
Aflatoxins GPC HPLC Fluorescence Post-column derivatization

"Analysis Of Aflatoxins (B1, B2, G1 And G2) In Rodent Feed By HPLC Using Post-column Derivatization And Fluorescence Detection"
J. Agric. Food Chem. 1991 Volume 39, Issue 1 Pages 137-140
Manuel Holcomb and Harold C. Thompson

Abstract: To the feed sample (50 g), NaCl (5 g) was added and the mixture was extracted with 70% methanol. A diluted portion of the filtered extract was purified on an Aflatest P monoclonal antibody affinity column. After washing with water, the aflatoxins were eluted with methanol. A portion (50 µL) was analyzed by HPLC on a Supelco reversed phase C18 column (25 cm x 4.6 mm) equipped with a guard column; water - methanol - acetonitrile (5:4:1) was used as mobile phase (0.8 mL min-1). Post-column derivatization was effected by reaction with a stream of 0.2% iodine solution; the reactor coil was heated to 68°C. Fluorescence detection at 440 nm with excitation at 365 nm was used. Response was rectilinear up to 1 ng of injected analyte for aflatoxins B1, B2 and G1 and up to 0.5 ng for G2. Detection limits were 0.25 ppb for B1, B2 and G1 and 0.12 ppb for G2.
Aflatoxin B1 Aflatoxin B2 Aflatoxin G1 Aflatoxin G2 HPLC Fluorescence Column Detection limit Heated reaction Post-column derivatization PPB

"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

"Automated Free Fatty Acid Determination Using Flow Injection Analysis Solvent Extractions"
J. Am. Oil Chem. Soc. 1987 Volume 64, Issue 7 Pages 1004-1007
John S. Canham and Gilbert E. Pacey

Abstract: The sample (100 µL) was injected into the carrier (toluene) stream which then segmented with the reagent (Cu(II) - pyridine) stream and passed (1.4 mL min-1) through a coil of PTFE tubing (0.5 m x 0.5 mm). The stream then entered the membrane separator (3.5 cm x 0.2 cm) and the absorbance of the toluene phase, containing the Cu(II) - fatty acid complex, was measured at 699 nm. The calibration graph was rectilinear in the range 60 µM to 6 mM oleic acid. Precision was ~1%. Solvent-extraction flow injection analysis (flow diagram presented) improved the rate of sampling, sensitivity and precision, and reduced the amount of reagent used and the hazards from toxic fumes.
Fatty acids, free Spectrophotometry Sample preparation Optimization Phase separator Solvent extraction Teflon membrane

"Semiautomated Method For Simultaneous Determination Of Phosphorus, Calcium, And Crude Protein In Animal Feeds"
J. AOAC Int. 1977 Volume 60, Issue 4 Pages 845-852
Hambleton, Larry G.

Abstract: A semiautomated method was developed for the simultaneous delermination of phosphorus, calcium, and crude protein in animal feeds. Samples are digested with a block digcstor, diluted to volume, and analyzed at the rate of 40 samples/hr. Protein is determined by the official AOAC method, by measuring the absorbance of an ammonia-salicylate complex at 660 nm. Phosphorus and calcium arc determined by measuring the absorbances of the molybdovanadophosphate and calcium-cresolphthalein complexes at 420 and 570 nm. respectively. Samples are weighed according to the amount of protein they contain. Over 90% of the mixed animal feed samples analyzed for phosphorus and calcium fall within the range of the instrument; provisions are made for single determinations on those samples; that fall outside the specified ranges. Results correlate well for the semiautomatcd method and official AOAC methods on mixed feed check samples and NBS Standard Reference Orchard Leaves.
Calcium Phosphorus Protein Spectrophotometry Simultaneous analysis Technicon

"Use Of Post-column Derivatization In Liquid Chromatographic Determination Of Sulfamethazine [sulfadimidine] And Sulfathiazole In Feeds And Feed Pre-mixes"
J. AOAC Int. 1982 Volume 65, Issue 4 Pages 823-827
Stringham R W; Mundell E C; Smallidge R L (SFS)

Abstract: Sulfonamide drugs are extracted from feed and feed premixes by shaking with 0.15N HCl in 25% methanol. The extract is diluted, clarified, and chromatographed on a reverse phase C18 column. Mobile phases used are methanol-2% acetic acid (35 + 65) and acetonitrile-2% acetic acid (18 + 82) for sulfamethazine (SMT) and sulfathiazole (STZ), respectively. A solution of dimethylaminobenzaldehyde (DMAB) is added to the column eluate and the resulting sulfonamide-DMAB complex is detected at 450 nm. The method was tested for linearity, recovery, and precision across a broad sample range. Recovery was 100.6±2.3% and 96.3±1.6% for STZ and SMT, respectively. Linearity was excellent (r2 = 0.9985 for STZ and r2 = 0.9996 for SMT) as was within-day precision (RSD = 2.00% for STZ and 1.52% for SMT). The method was compared with the Bratton-Marshall colorimetric method. Analysis of 14 STZ and 15 SMT samples failed to detect any bias between the 2 methods. Some practical aspects of the use of this technique are discussed.
Sulfamethazine Sulfathiazole HPLC Spectrophotometry Post-column derivatization Method comparison

"Simultaneous Determination Of Protein (nitrogen), Phosphorus, And Calcium In Animal Feeds By Multichannel Flow Injection Analysis"
J. AOAC Int. 1983 Volume 66, Issue 3 Pages 718-726
van Staden JF.

Abstract: A 3-channel flow injection procedure was developed, which enables the simultaneous determination of protein, phosphorus, and calcium in a wide range of animal feeds from a single digestion. Samples are digested with a block digestor, diluted, and analyzed at a rate of 82 samples/h. Protein (nitrogen) as ammonia is determined colorimetrically by the indophenol method. Phosphorus and calcium are determined by measuring the absorbances of the molybdenum blue and calcium-cresolphthalein complexes at 660 and 580 nm, respectively. Protein is determined in the range from 0 to 75%, phosphorus in the range from 0 to 6%, and calcium in the range from 0 to 6%. The results obtained do not differ significantly from those obtained by proven manual methods, and considerable time, space, and reagents are saved.
Proteins Phosphorus Calcium Sample preparation Spectrophotometry Complexation Multichannel Method comparison

"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

"Disposable Cartridge Extraction Of Retinol And α-tocopherol From Feedstuffs"
J. AOAC Int. 1985 Volume 68, Issue 6 Pages 1121-1125
Bourgeois CF, Hel SH, Belliot JP, George PR, Slomianny CA

Abstract: Samples (50 or 100 g) were hydrolyzed under reflux for 20 min in a N atmosphere in a mixture of pyrogallol solution [1 g L-1 in methanol - ethanol - water (19:5:1); 400 ml] and KOH (700 g l-1; 80 ml), and an aliquot (40 ml) was made up to 50 mL with aqueous 20% ascorbic acid. A portion was adsorbed on a silica gel (10 g) disposable cartridge and eluted with 2,2,4-trimethylpentane, and retinol and α-tocopherol in the eluate were determined by liquid chromatography and continuous-flow analysis, respectively. The coefficient of variation (n = 5 or 10) were 1.9 to 4.4% and recoveries were 85 to 114%. The proposed technique was compared with conventional liquid - liquid partition techniques and was found to be at least as quantitative and considerably faster.
α-Tocopherol Retinol Sample preparation Method comparison

"Extraction Of Sulfamethazine From Feed Samples"
J. AOAC Int. 1988 Volume 71, Issue 2 Pages 302-303
Blanchflower WJ, Rice DA

Abstract: Eight solvent systems based on aqueous NH3, anhydrous acetic acid, acetone, acetonitrile, CHCl3, methanol, water and HCl were evaluated for the extraction of sulfadimidine in feeding-stuffs. The extracts were analyzed by a previously described HPLC method with post-column derivatization with dimethylaminobenzaldehyde (cf. Stringham et al., Anal. Abstr., 1983, 44, 1G18). The highest recoveries were obtained with aqueous 75% methanol containing 2% of acetic acid. Pelleting and milling of samples (2 mm) decreased recovery with some extractants.
Sulfamethazine HPLC Sample preparation Post-column derivatization

"Liquid Chromatographic Determination Of Aflatoxins In Feedstuffs Containing Citrus Pulp"
J. AOAC Int. 1988 Volume 71, Issue 5 Pages 957-961
Paulsch WE, Sizoo EA, van Egmond HP

Abstract: The sample was extracted with CHCl3 and the extract was cleaned up on Sep-Pak Florisil and Sep-Pak C18 cartridges, the cited compounds being eluted with acetone - water (9:1 and 3:17, respectively). The eluate was analyzed on a column (15 cm x 4.6 mm) of LiChrosorb RP-18 (5 µm) with water - methanol - acetonitrile (13:7:4) as mobile phase (0.4 mL min-1), and detection by fluorescence at 400 nm (excitation at 365 nm) with (for B1 and G1) or without (for B2 and G2) post-column derivatization with iodine. The response was rectilinear from 0.1 to 3 ng. Recoveries from dairy rations fortified with 13, 5, 10, and 4 µg kg-1 of aflatoxins B1, B2, G1 and G2 were 87, 86, 81 and 82% with coefficient of variation (n = 12) of 3.1, 3.6, 5.2 and 3.8%, respectively.
Aflatoxin B1 Aflatoxin B2 Aflatoxin G1 Aflatoxin G2 HPLC Fluorescence Post-column derivatization

"Liquid Chromatographic Determination Of Aflatoxins, Ochratoxin A And Zearalenone In Grains, Oilseeds And Animal Feeds By Post-column Derivatization And Online Sample Cleanup"
J. AOAC Int. 1989 Volume 72, Issue 2 Pages 336-341
Chamkasem N, Cobb WY, Latimer GW, Salinas C, Clement BA

Abstract: Cereal, oilseed or animal feed (50 g) was extracted with aqueous acetonitrile - KCl - H3PO4 for 1 h, and the extract was filtered, diluted with water, and analyzed (0.3 ml) on an Econosphere C18 (5 µm) column (15 cm x 4.6 mm) equipped with a cleanup pre-column (5 cm x 4.6 mm) of Adsorbosphere C18 (10 µm) and operated with gradient elution (details given) with 5 mM Na2HPO4 buffer (pH 3.7), methanol and acetonitrile at 1.5 mL min-1 and post-column derivatization with saturated aqueous iodine in a reaction coil at 90°C for fluorimetric detection at 425 nm (excitation at 360 nm). Calibration graphs were rectilinear for up to 300 ppb of aflatoxins B1, B2, G1 and G2 and ochratoxin A and up to 1000 ppb of zearalenone in the samples; the corresponding limits of determination were 5 and 30 ppb.
Aflatoxin B1 Aflatoxin B2 Aflatoxin G1 Aflatoxin G2 Ochratoxin A Zearalenone HPLC Fluorescence Sample preparation Post-column derivatization Buffer PPB

"Online Monitoring Of An Animal Cell Culture With Multi-channel Flow Injection Analysis"
J. Biotechnol. 1994 Volume 37, Issue 3 Pages 253-264
Jens J. van der Pola,*, Uwe Spohnb, Rolf Eberhardta, Jochem Gaetgensa, Manfred Bisellia, Christian Wandreya and Johannes Tramperc

Abstract: A multi-channel flow injection analysis system was used for online monitoring of a continuous animal cell culture with high cell density. With this system, the glucose, lactate and glutamine concentration were determined using immobilized dehydrogenases, ammonium using an aqueous o-phthaldialdehyde solution. Glutamine concentration was determined on the basis of the difference between a glutamine and a glutamate measurement. To prevent disturbance of the measurement and pollution of the system, the analytes in the sample were separated from high molecular compounds by online dialysis. Online gas dialysis was used to avoid interference of other amino groups with the ammonium determination. In addition, dialysis was used as a dilution step. The measurement time for all four components was 42 min. This time included a final washing period after the analysis cycle. The system was calibrated once a day. Two continuous cultivations of a hybridoma cell line immobilized in open-porous glass carriers were monitored, using a fluidized bed reactor as cultivation system. The concentration of glutamine, glucose and ammonium determined with the online FIA system were in good agreement with the off-line data determined once a day. Only the lactate data showed some deviation. The immobilized enzyme reactors could be used for up to 3000-5000 injections. During the first cultivation, lasting 200 h, the start up period of the reactor was monitored. The online measurements described much better the time- course of the concentrations than the off-line data. It was possible to estimate the growth rate of the cells in the micro-carriers by the on- line data. In the course of the second cultivation, which lasted almost 1000 h, the influence of the dissolved oxygen concentration on the cell metabolism was monitored. It was noted that a sudden change of the glutamine concentration in the feed caused a fast change of the consumption and production rate of the measured metabolites.
Glucose Lactate Glutamine Biotechnology Immobilized enzyme Method comparison Process monitoring Interferences Dialysis Multichannel

"FIA Photometric Determination Of Calcium In Feed"
Lihua Jianyan, Huaxue Fence 1998 Volume 34, Issue 7 Pages 315-317
Dong, M.;Li, L.

Abstract: A method for the determination of Ca in feed by FIA photometry was presented. A red complex was formed by the reaction of fluorexon with Ca2+ in 0.20 M NaOH. A solution of triethanolamine (30 g/L) was used as carrier. The determining wavelength was 510 nm, and the linear range 0-10.0 µg/mL. The method was used to determine Ca in feed, the results were consistent with those obtained by KMnO4 titration, the relative standard deviation was 1.7-4.3%.
Calcium Spectrophotometry Method comparison

"New Approach For Wide-range Flow Injection Spectrophotometry: Determination Of Cobalt In Livestock Mineral Supplements"
Quim. Anal. 1989 Volume 8, Issue 2 Pages 129-137
Martinelli, M.;Bergamin, H.;Arruda, M.A.Z.;Zagatto, E.A.G.

Abstract: Samples (1.0 g) were mineralized with concentrated HCl (20 ml) by heating to near dryness at 80°C, 5 M HCl (5 ml) was added and the filtered solution was diluted to 100 mL with water. The complexing agent was aqueous Nitroso-R salt (0.2 g l-1). A flow diagram of the system is given; effects of coil lengths, reagent concentration, pH, and interfering and masking agents are reported. A variation of the sequential injection process is used, in which two sample plugs are injected into the carrier stream and allowed to overlap. The absorbance was measured at 516 nm, and Beer's law was obeyed up to 50 mg L-1 of Co. The system is stable and capable of analyzing up to 40 samples h-1; the coefficient of variation (n = 7) was 1.2% for 7.95 mg L-1 of Co. Results agreed with those obtained by ICP-AES.
Cobalt Sample preparation Spectrophotometry Method comparison Optimization Interferences

"Determination Of Starch In A Flow Injection System With Immobilized Enzymes"
Swed. J. Agri. Res. 1990 Volume 20, Issue 1 Pages 27-29
Bengtsson, S.;Larsson, K.

Abstract: Starch in ground samples (40 to 50 mg) of 36 compound feeds was hydrolyzed with a thermostable α-amylase (Termamyl) for 30 min at 95°C and determined by flow injection analysis with a carrier stream of 25 mM citrate buffer of pH 4.5 (0.8 mL min-1) and three packed-bed enzyme reactors containing (i) immobilized glucan 1,4-α-glucosidase, (ii) co-immobilized glucose oxidase, aldose 1-epimerase and (iii) peroxidase. The chromogenic reagent, 2 mM chromotropic acid and 1 mM 4-aminophenazone in citrate - phosphate buffer (pH 7) was added to the carrier stream, between reactors (i) and (ii), and H2O2 produced was detected spectrophotometrically at 590 nm. The detection limit was 2 µg mL-1 of starch. Results correlated well with a reference method (r = 0.992).
Starch Spectrophotometry Immobilized enzyme Buffer Detection limit Standard method Method comparison Chromogenic reagent

"Applications Of Flow Injection To Samples Of Agricultural Interest"
Tec. Lab. 1985 Volume 9, Issue 120 Pages 18-24
Martinez Calatayud, J.

Abstract: A review is presented, with 50 references, of methods applicable to soil, plants, fertilizers and water.
Review