A simple and rapid method was developed for the determination of benzoic acid, sorbic acid and dehydroacetic acid in margarine by high performance liquid chromatography (HPLC).
A 1.0g sample of margarine in a 50ml centrifuge tube with 50ml of distilled water was warmed to an almost completely molten state, and shaken vigorously. The water layer was taken out and a portion of it was filtered through a 0.45μm pore membrane filter. The filtrate was injected into an HPLC column (4.6×50mm) packed with Unisil Q C₁₈ (5μm). The column was eluted with a mixture of 0.03M sodium acetate-acetic acid buffer (pH 5.0)-methanol (4:1). The preservatives were detected with a UV-spectrophotometer set at 225nm.
Average recovery of individual preservatives from margarine was more than 96%. The detection limits were benzoic acid 0.5mg/kg, sorbic acid 0.7mg/kg and dehydroacetic acid 1.0mg/kg. There is no substantial difference in the recoveries from margarine of these preservatives between the proposed method and the steam distillation-GC method.