Direct solid sampling ETAAS determination of lead in muscle tissue contaminated by gun-shot residues

An increase in analyte content during pre-analytical steps such as sampling or sample preparation is still a serious source of error in trace and ultra-trace elemental analysis. In this study, the determination of Pb in muscle tissue of game containing gun-shot residues was used as an extreme model for such a 'secondary contamination'. For muscle samples free of gun-shot residues it was shown that direct solid sampling electrothermal atomization atomic absorption spectrometry (dSS-ETAAS) allows the determination of Pb without any sample preparation. The total analytical error in dSS-ETAAS mean value estimation could be considerably reduced by increasing the number of microsamples and by taking all microsamples from different sites of the sample. Thereby, repetition of analysis did not considerably increase the analytical time and cost. Results of dSS-ETAAS (y) showed good agreement with a conventional compound method as reference (x) (y = 1.18x(0.96), r = 0.92; t-test: P > 0.05) down to 7 ng g(-1) fresh substance. In non-homogenized muscle samples heavily contaminated with gun-shot residues, dSS-ETAAS made it possible to discern between primary (original Pb content) and secondary contamination (gun-shot residues). Secondary contamination was indicated by an increase of several orders of magnitude in the analyte content of microsamples contaminated by gun-shot residues. Pertaining to the low analytical masses, the ability of dSS-ETAAS to discern between samples with and without gun-shot residues was estimated to be up to four orders of magnitude higher than in conventional compound procedures.