Isotachophoretic determination of ethylenediaminetetraacetate in salad dressing, mayonnaise, and margarine.

An isotachophoretic method was developed for the determination of EDTA in foods imported by Japan. Skimmed samples of dressings, mayonnaise, or margarine were chromatographed on an anion exchange column, and interfering organic acids were eluted with water and 0.01N HCl. EDTA was eluted with 0.2N HCl and reacted with ferric chloride to form a stable EDTA--Fe complex. Electrophoresis was carried out with dilute HCl containing 0.05% Triton and beta-alanine (pH 3.5) as the leading electrolyte and 0.01M caproic acid as terminating electrolyte. Since uncoupled EDTA showed more than one zone, it was reacted with ferric chloride to form EDTA-Fe complex which showed only a single zone on an isotachopherogram. More than 90% of EDTA spiked at 100 or 1000 ppm level as disodium salt was recovered from the above mentioned three types of food. Detection limit was 10 ppm as disodium EDTA.