Atomic absorption spectrometric analysis of solids with on-line microwave-assisted digestion

Abstract

A procedure was developed for the on-line microwave-assisted digestion of solid samples and their analysis by flame atomic absorption spectrometry. The method involves the transport of a slurry of the sample in a 1 + 1 mixture of concentrated HNO₃ and H₂O₂, which provides quantitative extraction of Cu and Mn in a few minutes. Real samples of sewage sludges dispersed in 20 cm³ of HNO₃ and H₂O₂ can be digested in 4 min and other matrices, such as artichoke and diet samples dispersed in 10 cm³ of HNO₃ and H₂O₂ are digested in only 2 min. A closed flow injection system permits the on-line digestion to be carried out; the use of two interconnected injection valves allows the measurement of standards during the digestion of samples. The method permits the analysis of more than 15 samples per hour and provides accurate results, as demonstrated by the analysis of certified samples of sewage sludges ad tomato leaves.