Thin layer chromatographic identification of preservatives in food
Tjan, G.H.; Konter, T.
Journal - Association of Official Analytical Chemists 55(6): 1223-1225
1972
ISSN/ISBN: 0004-5756 PMID: 4669107 Document Number: 48519
A thin layer chromatographic method is described for the identification of benzoic, phydroxybenzoic, salicylic, and sorbic acids in foods. The preservatives are extracted from food with petroleum ether-ethyl ether (1+1); the acid preservatives are converted to their sodium salts by addition of sodium bicarbonate and the esters of p-hydrobenzoic acid remain in the organic layer. The acid preservatives are spotted on activated silica gel G plates and the plates are developed in a mobile solvent containing ammonia. The preservatives are detected by spraying with bromocresol purple. The ester preservatives are spotted on silica gel G plates with and without a fluorescent indicator; the plates are developed with benzeneethyl acetate (4+1) and then viewed under shortwave ultraviolet light or sprayed with bromocresol purple.