[Isotachophoretic determination of preservatives (author's transl)]

The preservatives sorbic acid, benzoic acid, methyl-, ethyl-, propylester of p-hydroxybenzoic acid and propionic acid can be determined quantitatively in one step by isotachophoretic separation based on the different electrophoretic mobilities of these compounds. The determination involves a direct extraction step in the so called Extrelut-columns, where the preservatives are separated from the food sample, mainly from the lipid phase. The whole analysis procedure is short and recoveries for the preservatives in the samples tested are very good. There is no interference by other substances and the range of concentrations for which a determination is possible is large and encompasses virtually all concentrations used in commercial practices.