Quantitative High Performance Thin Layer Chromatographic Determination of Organic Acid Preservatives in Beverages

A simple quantitative HPTLC method for the determination of sorbic acid, benzoic acid, and dehydroacetic acid in beverages without extraction or cleanup is described. Aliquots of samples and standards are chromatographed on preadsorbent silica gel or C-18 bonded silica gel plates containing fluorescent indicator, and the zones, which quench fluorescence, are compared by scanning densitometry. Recoveries of the acids from wine and juices spiked at 50–300 ppm averaged 98%, and the coefficient of variation of replicate analyses ranged from 2–5%. Commercial sodas containing unknown amounts sodium benzoate and iced teas containing potassium benzoate were analyzed by the method, and the tea analyses were validated by standard addition. The advantages of the TLC method relative to current HPLC and absorption spectrometric procedures are described.