Chromatography and Electrophoresis

A combined extraction/HPLC procedure was used to study the extractability of all gluten protein types from wheat flour and bread under both non-reducing and reducing conditions. The results indicate that the extractability of gliadin from bread with 60% ethanol under non-reducing conditions is strongly reduced. a - and g -gliadins are much more affected than w -gliadins, and less gliadin was extracted from the crust than from the crumb. For a complete extraction of gliadins from bread, reducing conditions and increased temp. are required. The recovery of gliadin added to flour before dough mixing and breadmaking is 98%. (Shortened author's abstract.) (20 references.) D.E.

99/00639*   Experimental and statistical approach for validating an HPLC assay for the determination of vitamin A in flour and milk powder for children. Aké M., Contento A.M., Mandrou B., Blanchin B., Fabre H. Chromatographia, 1998, 47, June, 716-720.

The validity of an HPLC method for the determination of vitamin A in flour and milk powder was assessed with regard to specificity, linearity, recovery, precision, limits of detection and quantification. (12 references.) P.D.C.

99/00640*   Monitoring biologically active amines in cereals and cereal based food products by HPLC. Farkas S., Hajós G. Chromatographia, 1998, 48, July, 37-42.

Biologically active amines (putreanine sulphate, N-acetyl putrescine, putrescine, cadaverine, histamine, agmatine, N-acetyl spermidine, spermidine, spermine) were separated and quantified in flour and cereal products by a liquid chromatographic method. The method consisted of the separation of ion pairs formed between the amines and octanesulphonic acid on a reversed-phase column, postcolumn derivatisation with o-phthaldehyde-2-mercaptoethanol and spectrofluorometric detection. (Shortened authors’ abstract.) (14 references.) P.D.C.

99/00641   Determination and survey of ochratoxin A in wheat, barley, and coffee – 1997. Trucksess M.W., Giler J., Young K., White K.D., Page S.W. Journal of AOAC International, 1999, 82, Jan./Feb., 85-89.

A modified liquid chromatographic method for determining ochratoxin A in green coffee was applied to wheat, barley, green coffee and roasted coffee. Recoveries of ochratoxin A from the four commodities spiked over the range 1-4 ng/g were 71-96%. The limit of detection was about 0.03 ng/g. Ochratoxin A contamination at > 0.03 ng/g was found in 56 of 383 wheat samples and 11 of 103 barley samples from the USA. Only four samples of wheat and one of barley were contaminated above a level of 5 ng/g. (Shortened authors’ abstract.) (11 references.) A.C.G.

99/00642   Preparative method for isolating a -zearalenol and zearalenone using extracting disk. Ware G.M., Zhao Y., Kuan S.S., Carman A.S. Journal of AOAC International, 1999, 82, Jan./Feb., 90-94.

The conversion of a liquid chromatographic method for the determination of zearalenol and zearalenone in maize, using liquid-liquid partition to the solid-phase extraction disk format, is described. Zearalenol and zearalenone were added at levels ranging from 10 to 2000 ng/g to a control sample of maize. Recoveries of both toxins from the spiked samples were 106.3 and 103.8%, with coefficients of variation of 7.6 and 13.0%, respectively. It is estimated that the method has a reliable limit of quantitation and limit of detection of around 40 and 10 ng/g, respectively, for each toxin. (22 references.) A.C.G.

99/00643   A validated liquid chromatographic method for determining folates in vegetables, milk powder, liver, and flour. Konings E.J.M. Journal of AOAC International, 1999, 82, Jan./Feb., 119-127.

A liquid chromatographic procedure, using affinity chromatography to clean up extracts, was elaborated for determining folates in foods. The method was used to determine folates in vegetables, milk powder, liver and flour and the results are claimed to be satisfactory, reliable and reproducible. It is stated that good estimates of monoglutamates, polyglutamates and matrix-bound folates can be made. A combined treatment of the food extract with rat plasma conjugase, amylase and protease is recommended for determination of total folate contents. (36 references.) A.C.G.

99/00644   Determination of niacin in infant formula and wheat flour by anion-exchange liquid chromatography with solid-phase extraction cleanup. LaCroix D.E., Wolf W.R., Vanderslice J.T. Journal of AOAC International, 1999, 82, Jan./Feb., 128-133.

A simple, rapid, solid-phase extraction (SPE) procedure, incorporating aromatic sulphonic acid SPE and sulphonated Florisil SPE columns in a rapid cleanup, has been developed for separation and cleanup of niacin from a complex food matrix digest. Niacin contents of infant formula and wheat flour reference materials were determined in order to validate the method. (21 references.) A.C.G.

99/00645*   Determination of organo-phosphorus pesticides in wheat flour by supercritical fluid extraction and gas chromatography with nitrogen-phosphorus detection. Kim D.H., Heo G.S., Lee D.W. Journal of Chromatography A, 1998, 824, No.1, 63-70.

The method used extraction of organophosphorus pesticides from wheat flour using supercritical carbon dioxide at 206.8 bar and 60°C, followed by quantitation using gas chromatography with nitrogen-phosphorus detection without clean-up of the extracts. The method was able to determine the pesticides ethoprophos, diazinon, chlorpyrifos methyl, fenitrothion, parathion, phenthoate and EPN in samples at the 10 ng/g level. (Shortened authors’ abstract.) (22 references.) P.D.C.

99/00646*   GC/MS procedure for analysis of synthetic pyrethroid residues in treated cereals. Hajslová J., Kosinková P., Kocourek V., Poustka J., Holadová K Czech Journal of Food Science, 1997, 15, No.1, 1-12.

Grains were extracted with ethyl acetate and gel permeation chromatography was employed for clean-up of crude extracts. High resolution gas chromatography with a mass selective detector performed in selected ion monitoring mode was used for isomeric separation of these insecticides and their subsequent quantitation. The recoveries at 0.1 mg/kg spiking level were 90-99%. The detection limits ranged from 0.0002 to 0.05 mg/kg. Compared with existing methods, the procedure presented in this study was less laborious and highly selective. (Modified authors’ abstract.) (10 references.) P.D.C.

99/00647*   Fractionation of wheat gliadins by counter-current distribution using an organic two-phase system. Truust H., Johansson G. Journal of Chromatography B, 1998, 711, No.1/2, 245-254.

A liquid-liquid two-phase system based on N,N-dimethylformamide and the two polymers, poly(ethyleneglycol) and Ficoll, useful for partitioning of hydrophobic proteins, has been developed. The system has been applied to a counter-current distribution process in 56 steps for analysing the heterogeneity of proteins extracted with N,N-dimethylformamide from wheat flour. The counter-current distribution patterns of proteins extracted from eight kinds of wheat have been analysed. The minimum number of hypothetical proteins necessary to describe the patterns was found to be seven. The relative amount of these hypothetical components varied among the wheats. (Authors’ abstract.) (22 references.) P.D.C.

99/00648   Linking extraction and purification of maize samples for fumonisin analysis. Velázquez C., Liovera M., Peña E., Sala N., Canela R. Food Additives and Contaminants, 1999, 16, March, 125-128.

A new method for the analysis of fumonisins in maize is described. The method integrated the extraction and purification of maize samples into one step and involved the introduction of 1 g of ground maize into the top of a SAX column followed by sequential elution using different solvent mixtures. The new method compared favourably with other known methods. (25 references,) P.D.C.

99/00649   Fat contents of cereal foods: comparison of classical with recently developed extraction techniques. Zou W., Lusk C., Messer D., Lane R. Journal of AOAC International, 1999, 82, Jan./Feb., 141-150.

Eight cereal products ranging from a fat-free ready-to-eat cereal to a full-fat high-ratio cake mix were subjected to analyte separation by anhydrous diethyl ether extraction (EE), acid hydrolysis/mixed ether extraction (AH), solid-phase extraction (SPE), and supercritical fluid extraction (SFE) with carbon dioxide and with carbon dioxide modified with 15% ethanol (SFE_mod). Gravimetric analyses of extracts indicated higher crude fat values by AH than by EE, SFE or SFE_mod. Extractions followed by fatty acid ester analysis also produced higher triglyceride means by AH than by other methods. Therefore, for labelling purposes, AH seems most appropriate. SFE and SPE offer the advantages of reduced solvent vol., short extraction times and ease of laboratory automation. (Modified authors’ abstract.) (29 references.) A.C.G.

99/00650*   High-performance capillary electrophoresis of cereal proteins. Bean S.R., Bietz J.A., Lookhart G.L. Journal of Chromatography A, 1998, 814, No.1/2, 25-41.

The development of charge- and size-based high-performance capillary electrophoresis (HPCE) for analysis of cereal grain proteins is reviewed. The major methods used for wheat protein free zone capillary electrophoresis are described. Its applications in cultivar differentiation, characterisation of proteins and protein classes, classification and quality prediction and breeding are considered. (91 references.) D.E.