Wet sample digestion for quantification of vanadium(V) in serum by electrothermal atomic absorption spectrometry

Three types of pressure digestion systems used prior to the determination o f the ultratrace element vanadium by electrothermal atomic absorption spect rometry were evaluated: The high-pressure ashing (HPA) system, the DAB III pressure digestion system and the pressurized microwave digestion (PMD) sys tem. Complete sample digestion and no loss of graphite tube sensitivity as well as reliable vanadium values could only be achieved with HPA digests of freeze-dried serum. The mean recovery rate was 98% and no loss of tube sen sitivity could be observed. Using non-lyophilized serum the mean recovery r ate was 70%. The DAB III digestion system, vicarious for closed pressure di gestion in steel bombs with an allowable temperature up to about 200 degree s C, cannot be recommended to mineralize human biological material for vana dium determinations, because the remaining not completely decomposed organi c compounds extracted together with the vanadium-cupferron complex caused a marked carbon-builtup and formation of carbides in the graphite tube were found to change the shape of the absorption signals distinctly, and to decl ine the tube sensitivity strongly (about 25%) so that reliable results cann ot be achieved. The recovery rate was too low in general (about 50%). in ad dition, a subsequent treatment of the DAB ill digests with perchloric acid was unsuccessful. The PMD system proved to be not suited, because the sampl es became highly contaminated by vanadium possibly from the titan seal. (C) 1999 Elsevier Science B.V. All rights reserved.