Determination of arsenic and selenium in vegetable and herbage samples by X-ray fluorescence spectrometry using coprecipitation

Abstract

A procedure is described for the determination of both arsenic and selenium in vegetable and herbage samples. Organic material was destroyed by nitric acid in the presence of magnesium and nickel nitrates, prior to the separation of the analytes. The arsenic and selenium were separated from solution by reduction to the elements using tellurium as a carrier and hypophosphorous acid as reductant. The precipitated analytes together with the carrier were collected by filtration and the filter was examined directly in the wavelength-dispersive X-ray fluorescence spectrometer. For a sample mass of 1 g the procedure has a detection limit of 0.1 µg of arsenic and selenium and the calibration is linear up to at least 25 µg of the analytes. The accuracy and precision of the procedure are better than 3% relative at the 4 µg g^–1 level.