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 -> grain -> maize

Citations 11

"Fluorimetric Determination Of Aflatoxins By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1988 Volume 332, Issue 7 Pages 809-812
Fernando Lazaro, M. Dolores Luque de Castro and Miguel Valcarcel

Abstract: Peanuts (100 g) are extracted by shaking with 500 mL of aqueous 55% methanol plus 200 mL of hexane and 4 g of NaCl. A 25 mL portion of the aqueous methanol phase is extracted with 25 mL of CHCl3, the CHCl3 is evaporated under N, and the residue is dissolved in 5 mL of methanol. The solution is diluted to 10 mL with water, filtered through nylon 66 (0.45 µm) and extracted with 10 mL of CHCl3. The extract is evaporated, the residue is dissolved in 1 mL of methanol, and the solution is diluted to 5 mL with water. Maize or tapioca (50 g) is mixed with 10 g of diatomaceous earth and extracted with 150 mL of aqueous 85% acetone, the mixture is filtered, and 50 mL of the filtrate is mixed with 20 mL of saturated (NH4)2SO4 solution, 130 mL of water and 10 g of diatomaceous earth. This mixture is filtered, and 100 mL of the filtrate is extracted with 3 mL of benzene. The extract is evaporated under N, the residue is dissolved in methanol and the solution diluted with water as before. Each sample solution was injected into a stream of aqueous 40 µM-Br, and the fluorescence was monitored at 470 nm. From 0.5 to 200 ng mL-1 of total aflatoxins (B1, B2, G1 and G2) could be determined. The method is very rapid, the residence time for each flow injection peak being only 6 s.
Aflatoxins Fluorescence

"Fluorimetric Determination Of Aflatoxins In Foodstuffs By High Performance Liquid Chromatography With Flow Injection Analysis"
J. Chromatogr. A 1988 Volume 448, Issue 1 Pages 173-181
F. Lázaro, M. D. Luque de Castro and M. Valcárcel

Abstract: Aflatoxins were extracted from peanuts and maize (methods given). Portions of the extract were injected in to a column (20 cm x 4 mm) of Nucleosil 120 (5 µm) for HPLC with a mobile phase (0.7 mL min-1) of water - methanol - acetonitrile (94:59:47) and fluorimetric detection at 440 nm (excitation at 360 nm) after flow injection derivatization of aflatoxins B1 and G1 with Br. Calibration graphs were rectilinear from 0.5 to 200 ng mL-1 of aflatoxins G2, G1, B2 and B1. The coefficient of variation (n = 11) were 1.7, 1.0, 1.7 and 1.8%, respectively.
Aflatoxin B1 Aflatoxin B2 Aflatoxin G1 Aflatoxin G2 HPLC Fluorescence Merging zones Optimization 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

"Amino-acid Analysis Of Feedstuff Hydrolysates By Pre-column Derivatization With Phenyl Isothiocyanate And Reversed-phase High Performance Liquid Chromatography"
Cereal Chem. 1987 Volume 64, Issue 4 Pages 226-229
R. G. Elkin and A. M. Wasynczuk

Abstract: Maize, peanut meal, two sorghum varieties and a maize - soya-bean meal-based complete mixed feed were either untreated or oxidized with performic acid before hydrolysis with HCl. Amino-acids in the hydrolysate were derivatized with phenyl isothiocyanate and the resulting phenylthiocarbamoyl derivatives were analyzed by HPLC on a column (15 cm x 3.9 mm) of Pico-Tag operated at 33°C. Elution was effected with a gradient from 90 to 0 to 90% of 0.14 M Na acetate containing 0.7 mL L-1 of triethanolamine in aqueous 60% acetonitrile and detection was at 254 nm. Amino-acids were also determined in hydrolysates by cation-exchange chromatography (J. Assoc. Off. Anal. Chem., 1985, 68, 1028) and post-column derivatization with ninhydrin. Amino-acid values by HPLC generally agreed with those by cation-exchange chromatography. Complete separation of 17 hydrolysate amino-acids plus methionine and cysteic acid was achieved in 25 min by HPLC and, thus, use of modular HPLC equipment provides a viable alternative to the use of amino-acid analyzers.
Amino Acids HPLC Spectrophotometry Heated reaction Post-column derivatization Pre-column derivatization

"Chromatographic Quantitation Of Free Amino-acids: S-methylmethionine, Methionine And Lysine In Corn"
Commun. Soil Sci. Plant Anal. 1991 Volume 22, Issue 17-18 Pages 1873-1882
Grunau, J.A.;Swiader, J.M.

Abstract: Dried, powdered corn kernels (500 mg) were extracted with 3.5% sulfosalicylic acid for 15 to 20 min at room temperature The mixture was centrifuged, the supernatant (3.0 ml) was combined with 20 mM canavanine as internal standard and 7 M NaOH to give pH 2.2, and the solution was pre-filtered then ultra-filtered. The extract was diluted 1:1 with Pickering Lithium Diluent (pH 2.20). The amino-acids and other ninhydrin-positive substances were analyzed on a modified HP1090 liquid chromatograph at 43°C, with gradient elution using Li citrate of pH 2.75 and 7.50 (0.30 mL min-1), post-column derivatization at 130°C with ninhydrin (0.3 mL min-1) and detection at 570 nm. The detection limit was 20 pM of S-methylmethionine (1 µM for a 20 µL injection). Free methionine and lysine were also measured.
Amino Acids Lysine Methionine S-Methylmethionine HPLC Filter Heated reaction pH Post-column derivatization

"Comparison Of Post-column Derivatization - Liquid Chromatography With Thin-layer Chromatography For Determination Of Aflatoxins In Naturally Contaminated Corn"
J. AOAC Int. 1990 Volume 73, Issue 4 Pages 579-581
Beaver, R.W.;Wilson, D.M.;Trucksess, M.W.

Abstract: Samples were ground to pass through a 20-mesh sieve, then extracted and cleaned up by open-column chromatography as in the AOAC CB method 968.22 ('Official Methods of Analysis', 15th Ed., AOAC, Arlington, VA, 1990). Portions of the resulting concentrate were evaporated under N at 40°C, and the residue was dissolved in aqueous 50% acetonitrile for analysis on a column (25 cm x 4.6 mm) of Ultrasphere PTH C18 (5 µm) at 50°C, with aqueous 50% methanol as mobile phase and post-column reaction with 0.2% iodine solution in aqueous 1% methanol in a 10-ft coil at 75°C. Fluorimetric detection was at 421 nm (excitation at 361 nm). Portions of the same extracts were analyzed by TLC (loc. cit.); results correlated well, and those for aflatoxin B1 by the two methods were equivalent, but the results for aflatoxin B2 by LC were only half those obtained by TLC. Interference precluded the LC determination of aflatoxin G1 at low concentration.
Aflatoxin B1 Aflatoxin B2 LC Fluorescence Sample preparation Column Interferences Heated reaction Post-column derivatization Method comparison

"Immunoaffinity Column Coupled With Solution Fluorimetry Or Liquid Chromatography Post-column Derivatization For Determination Of Aflatoxins In Corn [maize], Peanuts And Peanut Butter: Collaborative Study"
J. AOAC Int. 1991 Volume 74, Issue 1 Pages 81-88
Trucksess MW, Stack ME, Nesheim S, Page SW, Albert RH, Hansen TJ, Donahue KF.

Abstract: The preliminary evaluation of the Aflatest P immunoaffinity column (Vicam, Somerville, MA) reported previously (Ibid., 1990, 73, 425) has been followed by an AOAC - IUPAC collaborative study. Each participating laboratory received samples of naturally contaminated maize and of maize, peanuts and peanut butter containing added aflatoxins (30, 20 and 10 ng g-1, respectively). Total aflatoxins were determined by fluorimetry in solution with Br; individual aflatoxins by reversed-phase LC with post-column derivatization with I. For total aflatoxins, recoveries were 105 to 123% and coefficient of variation for repeatability and reproducibility were 11.8 to 16.6 and 11.0 to 33.1%, respectively. For individual aflatoxins, the corresponding ranges were 81 to 83, 5.2 to 17.2 and 4.7 to 50.8%. Use of immunoaffinity columns with either method of determination is recommended as official first action.
Aflatoxins LC Fluorescence Post-column derivatization

"Comparison Of An ELISA-based Screening Test With Liquid Chromatography For The Determination Of Aflatoxins In Corn [maize]"
J. AOAC Int. 1991 Volume 74, Issue 5 Pages 827-829
Beaver RW, James MA, Lin TY

Abstract: The CITE PROBE ELISA kit (Idexx Corp., Portland, ME) was compared with extraction and cleanup by the method of Thean et al. (Ibid., 1980, 63, 631) followed by LC with post-column derivatization with iodine as described previously (Ibid., 1990, 73, 579). The CITE PROBE is concluded to be a reliable screening method for detection of 5 ng g-1 of aflatoxins in maize.
Aflatoxins LC Sample preparation Extraction Method comparison Post-column derivatization

"Aflatoxin Analysis By Reversed-phase HPLC Using Post-column Derivatization For Enhancement Of Fluorescence"
J. Liq. Chromatogr. Relat. Technol. 1986 Volume 9, Issue 1 Pages 103-112
P. G. Thiel; S. Stockenstrom; P. S. Gathercole

Abstract: Aflatoxins extracted from maize, peanut butter, sorghum malt or duckling mash were subjected to HPLC on a column (7.5 cm x 4.6 mm) of Altex Ultrasphere ODS (3 µm) with a mobile phase (1 mL min-1) of 0.01 M KH2PO4 - acetonitrile - methanol (39:9:7); the eluate was treated with saturated aqueous iodine at 60°C before the fluorescence was measured at 440 nm (excitation at 365 nm). The calibration graphs were rectilinear for 1.16, 0.48, 1.48 and 0.84 ng µL-1 for aflatoxins B1, B2, G1 and G2, respectively.
Aflatoxin B1 Aflatoxin B2 Aflatoxin G1 Aflatoxin G2 HPLC Fluorescence Heated reaction Post-column derivatization

"The Action Of Gravity In Agravitropic Zea Primary Roots: Effect Of Gravistimulation On The Extracellular Free-Ca2+ Content In The 1-mm Apical Root Tip In The Dark"
Planta 1994 Volume 192, Issue 3 Pages 379-383
Takashi Suzuki, Chiharu Takeda and Tamami Sugawara

Abstract: Gravity stimulation in darkness was examined in agravitropic maize cv. Golden Cross Bantam 70 primary roots. Contents of diffusible and nitric-acid-extractable Ca2+ in 1-mm apical tips of roots gravistimulated in the dark were measured by flow injection analysis as free Ca2+ and bound Ca2+, respectively. The free-Ca2+ content increased transiently, reaching a maximum 0.5 h after gravistimulation. This transient increase was also observed when gravistimulation was applied by changing the orientation of the roots back from horizontal to vertical again. On the other hand, the bound-Ca2+ content decreased transiently following gravistimulation. Furthermore, when the root caps treated with 10 mM 2-(N-morpholino) ethane-sulfonic acid buffer, the elevation of free Ca2+ following gravistimulation was prevented. These results indicate that gravity perception and the initial transduction steps proceed in the dark, and that the elevation of free Ca2+ brought about by the interaction of Ca2+/H+ in the apoplast of root tips may be involved in transmission of the gravity signal.

"An Analysis Of Avidin, Biotin And Their Interaction At Attomole Levels By Voltammetric And Chromatographic Techniques"
Anal. Bioanal. Chem. 2005 Volume 381, Issue 6 Pages 1167-1178
Rene Kizek, Michal Masarik, Karl J. Kramer, David Potesil, Michele Bailey5, John A. Howard, Borivoj Klejdus, Radka Mikelova, Vojtech Adam, Libuse Trnkova6 and Frantisek Jelen

Abstract: The electroanalytical determination of avidin in solution, in a carbon paste, and in a transgenic maize extract was performed in acidic medium at a carbon paste electrode (CPE). The oxidative voltammetric signal resulting from the presence of tyrosine and tryptophan in avidin was observed using square-wave voltammetry. The process could be used to determine avidin concentrations up to 3 fM (100 amol in 3 µL drop) in solution, 700 fM (174 fmol in 250 µL solution) in an avidin-modified electrode, and 174 nM in a maize seed extract. In the case of the avidin-modified CPE, several parameters were studied in order to optimize the measurements, such as electrode accumulation time, composition of the avidin-modified CPE, and the elution time of avidin. In addition, the avidin-modified electrode was used to detect biotin in solution (the detection limit was 7.6 pmol in a 6 µL drop) and to detect biotin in a pharmaceutical drug after various solvent extraction procedures. Comparable studies for the detection of biotin were developed using HPLC with diode array detection (HPLC-DAD) and flow injection analysis with electrochemical detection, which allowed biotin to be detected at levels as low as 614 pM and 6.6 nM, respectively. The effects of applied potential, acetonitrile content, and flow rate of the mobile phase on the FIA-ED signal were also studied.
Avidin Electrode Detector