[Various methods for the determination of preservatives in food. I. Extraction and spectrophotometric determinations...

In the Federal Republik of Germany formic acid, benzoic acid, propionic acid, sorbic acid and the esters of p-hydroxybenzoic acid were permitted as food-additives. They can be extracted together from acidified materials by means of perforation with ether. During distillation the preservatives are fixed by sodium hydroxide. The alkaline extract can then be used directly for various photometric (Part I) and chromatographic (Part II) determinations. All preservatives except propionic acid can be identified and determined by simple and specific color reaction. From the alkaline extract, benzoic acid, sorbic acid and the esters of p-hydroxybenzoic acid can be separated as the free acid by thin-layer chromatography on silica gel. Determination of the remission at 232 nm and 260 nm and of the reduction in fluorescence are employed for the photometric in situ evaluation of the thin-layer chromatograms.