Abstract

Procedures for determining the toxic metals arsenic, cadmium and lead in different types of food colourants using slurried samples are developed. Suspensions were prepared by weighing 0.025–0.15 g of colourant and adding 10 ml of a solution containing 0.1% m/v Triton X-100, 50% v/v concentrated hydrogen peroxide, 1% v/v concentrated nitric acid, one drop of silicon antifoam and the corresponding matrix modifier (0.3% m/v nickel for arsenic and 1% m/v ammonium dihydrogen phosphate for cadmium and lead). The slurried samples were introduced directly into the furnace, and, for calibration, aqueous standards for arsenic and cadmium and the standard additions method for lead were used. The characteristic masses were 11, 0.6 and 10 pg for arsenic, cadmium and lead, respectively, and the corresponding detection limits were 33, 0.8 and 11 pg. The reliability of the procedure was checked by comparing the results obtained with others based on microwave-oven sample digestion and by analysing a certified reference material.