A microdigestion procedure directly performed in the autosampler cups for the determination of trace elements in biological samples by GF AAS

Abstract

A microdigestion procedure for the determination of Cd and Cu in biological samples by graphite furnace atomic absorption spectrometry (GF AAS) is described. Masses up to 5 mg are directly weighed in the autosampler cup and 100 µL of the digestion solution (1:1 v/v HNO3-H2SO4 or concentrated HNO3) are added. The cups are closed and the digestion is performed, at 60 oC overnight in a specially designed digestion block. After cooling, 900 µL of ultrapure water is added, the solution is homogenized and the cups are transferred to the autosampler tray. Since the digestion is performed in a sealed environment and the whole procedure uses only one flask, the risks of contamination and losses are minimized. Calibration was performed with external calibration curves, in the same medium as the reagents blank. The analysis of nine different standard reference materials permitted the assessment to the accuracy of the procedure. Considering a 5 mg sample mass, the limits of quantification in the original samples calculated from ten successive measurements of the blank solution (k=10) were 0.07 and 1.7 and 0.02 and 0.3 µg g-1 for Cd and Cu respectively, using the HNO3-H2SO4 mixture or concentrated HNO3 for the digestion. The procedure was used for the determination of Cu in human liver biopsy samples.