Liquid chromatographic determination of six sulfonamide residues in animal tissues using postcolumn derivatization

A sensitive and reproducible liquid chromatographic method is described for the simultaneous determination of sulfonamide residues in animal livers and kidneys. The selectivity of the method is enhanced significantly through the use of postcolumn reaction with p-dimethylaminobenzaldehyde, followed by detection at 450 nm. Consequently, the cleanup is simplified; it consists of removal of fatty material by partitioning the sample extract into an acetonitrile-hexane system. The sulfonamides used for this study were sulfadiazine, sulfapyridine, sulfamerazine, sulfadimidine, sulfamethoxypyridazine, and sulfaquinoxaline. At the level of 100 micrograms/kg, the recoveries ranged from 70 to 104% and were dependent on the nature of the matrix and the particular sulfonamide. The coefficients of variation are 2-10% at this level. The detection limit was 20 micrograms/dg.

Reverse-phase liquid chromatographic determination of benzoic and sorbic acids in foods

An isocratic liquid chromatographic (LC) technique is described for the determination of benzoic acid and sorbic acid in foods such as beverages, fruits, seafood, vegetables, sauces, and dairy, bakery, and confectionery products. A C18 column is used with methanol-phosphate buffer (5 + 95) as mobile phase and 4-hydroxyacetanilide or 3,5-dinitrobenzoic acid as internal standard. Sample preparation is simple, rapid, and produces a sample extract that has a minimum effect on the column performance and life. Specificity of the method was checked against common food additives such as L-ascorbic acid, caffeine, artificial sweeteners (saccharin, cyclamate, aspartame), antioxidants (BHT, BHA) and artificial colors. Also described are 2 procedures for confirmation of the preservatives, using either redox reaction of sorbic acid with potassium permanganate or gas chromatography/mass spectrometry. Mean recoveries of 90-105% were obtained with a precision of 1-6% and a detection limit of 20 mg/kg for the 2 preservatives.

Capillary gas chromatographic-mass spectrometric study of the effect of solvents on metoprolol and other aryloxypropanolamines

When metoprolol in methanol was analysed by capillary gas chromatography (GC), an additional peak was observed; mass spectrometry (MS) showed this additional peak to have a molecular weight 12 dalton higher than that of the parent compound. A similar phenomenon was observed with other beta-adrenergic blocking aryloxypropanolamines in methanol or dichloromethane. Capillary GC-MS using deuterated solvents as isotopic markers showed that a methylene group from the solvents was incorporated into the parent molecule. The structure of the observed products and the mechanism of their formation are proposed.