Analysis of foods for arsenic and selenium by acid digestion, hydride evolution atomic absorption spectrophotometry

A method based on acid digestion, hydride evolution atomic absorption spectrophotometry for estimating microgram and submicrogram quantities of As and Se in foods was developed and evaluated. Samples up to 3 g dry weight were digested with HNO3-HCIO4-H2SO4. As and Se in aliquots of the digests were reduced with NaBH4 to volatile hydrides, using laboratory-constructed and commercially available generators. As and Se were estimated by transient signal atomic absorbance measurements as the hydrides were decomposed in an Ar-H2-entrained air flame. Recoveries of inorganic As and Se added at levels of 0.1-1.0 microgram/g to a variety of foods ranged from 70 to 125%. Analyses of several standard reference samples indicated the method is capable of recovering native analytes. Detection limits for the determinative step and the method as a whole were as low as 5 and 25 ng, respectively, for both elements.