University of North Florida
Browse the Citations

Contact Info

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

View Stuart Chalk's profile on LinkedIn


Classification: Food -> bread

Citations 3

"Photochemical Spectrophotometric Determination Of Riboflavine And Riboflavine 5'-phosphate By Manual And Flow Injection Methods"
Analyst 1994 Volume 119, Issue 6 Pages 1199-1203
Tomás Perez-Ruiz, Carmen Martínez-Lozano, Virginia Tomás and Otilia Val

Abstract: For the manual analysis, 0.2 M phosphate buffer of pH 7.2 was mixed with 3% Triton X-100, 1 mM MnSO4 and 16 mM dianisidine. Sample solution was added to the mixture before dilution with water. The solution was irradiated at 25°C and the absorbance at 460 nm was recorded as a function of the irradiation time. Calibration graphs were linear from 0.1-5 µM-riboflavine (I) and -riboflavine 5'-phosphate (II) with an RSD of 0.68%. For FIA, three reagent streams, viz, 2 mM dianisidine containing 0.45% Triton X-100 (0.7 ml/min), 0.1 M phosphate buffer of pH 7.2 (0.7 ml/min) and 0.1 mM MnSO4 (0.7 ml/min), were mixed. Sample solution was injected into the mixed reagent stream (2.1 ml/min) and transported to a reaction coil (100 cm x 0.5 mm i.d). The flow was stopped, the solution irradiated for 60 s and the absorbance at 460 nm was measured. A diagram of the manifold used is given. Calibration graphs were linear from 1-10 µM-I and -II; corresponding RSD were 1.3 and 1.1%. The throughput was 40 samples/h. Recoveries were quantitative for both methods. The methods were applied to multivitamin preparations and fortified bread.
Spectrophotometry Buffer Triton X Surfactant Photochemistry Stopped-flow

"Evaluation Of An HPLC Method For The Determination Of Phylloquinone (vitamin K1) In Various Food Matrices"
J. Agric. Food Chem. 1994 Volume 42, Issue 2 Pages 295-300
Sarah L. Booth, Kenneth W. Davidson, and James A. Sadowski

Abstract: Phylloquinone was extracted from vegetable juice, cows milk, spinach, bread and beef with propan-2-ol/hexane (details given) with 2,3-dihydrophylloquinone or 2-methyl-3-(3,7,11,15,19-pentamethyl-2-eicosenyl)-1,4-naphthalenedione added (internal standards; details given). The extracts under went solid-phase extraction on silica columns (described) with elution effected by hexane/ethyl ether (93:3). Beef extracts were further purified by HPLC on a C18 column (described). The purified extracts were dissolved in methanol containing 10 mM ZnCl2, 5 mM acetic acid and 5 mM sodium acetate (milk extracts were dissolved in 10 mM ZnCl2, 5 mM acetic acid and acetonitrile) and analyzed on an Hypersil ODS (3 µm) column (15 cm x 4.6 mm i.d.) with a mobile phase (1 ml/min) of methanol/CH2Cl2 (9:1) containing 5 ml/l of 2 M ZnCl2, 1 M acetic acid and 1 M sodium acetate with fluorescence detection at 418 nm (excitation at 244 nm) after post-column derivatization in an online chemical reactor (50 mm x 2 mm) with Zn metal (200 mesh). Intra- and inter-day RSD were 6.6-13.6% with between sample RSD (n = 10) of 7.8% (milk), 32.6% (spinach) and 44.6% (vegetable juice).
Vitamin K1 HPLC

"Liquid Chromatographic Analysis Of Thiamine And Its Phosphates In Food Products Using Amprolium As An Internal Standard"
J. Micronutr. Anal. 1986 Volume 2, Issue 3 Pages 189-199
Huang, M. H.A.

Abstract: Samples of food (e.g., pork, chicken, ham, bread, cereal, almonds or peanut butter) were blended (if necessary) and mixed with 5% sulfosalicylic acid solution and amprolium (internal standard). The mixture was extracted with hexane, and the extract was cleaned-up on a column (30 cm x 6 mm) of Bio-Rad AG 2-X8 anion-exchange resin with elution by using 0.1 M sodium phosphate buffer (pH 5.5). The eluate was analyzed by HPLC on a column (3 cm x 3 mm) of C18 material (3 µm) with a mobile phase (1 mL min-1) of two 0.1 M sodium phosphate buffers (pH 5.5 and 2.6) for 6 min and 19 min, respectively. Fluorimetric detection was at 432 nm (excitation at 339 nm) after post-column derivatization of thiamine and its phosphates to their thiochrome derivatives.
Thiamine Thiamine monophosphate HPLC Fluorescence Post-column derivatization