Elimination of the carbon build-up effect in the ETAAS analysis of low diluted serum samples using an in situ wet digestion with tetramethylammonium hydroxide. Application to aluminium determination

A simple and effective procedure to minimise the accumulation of carbonaceo us residues inside the graphite tube during the electrothermal atomic absor ption spectrometric (ETAAS) determination of aluminium in human serum is de scribed. The procedure involves the addition of tetramethylammonium hydroxi de (TMAH) to the injected samples to effect an in situ wet digestion of the serum proteins. Results obtained showed that the addition of 5 mu l of 1 m ol l(-1) TMAH to each 15 mu l sample injection allows the repeated analysis of over 200 serum samples (diluted 1 + 1 with a diluting solution containi ng 1 g l(-1) K2Cr2O7, 0.5% v/v Triton X-100 and 0.2% v/v HNO3) with no evid ence of a carbon build-up effect. Compared with the same ETAAS procedure wi thout the addition of TMAH, a good improvement in repeatability, long-term precision and accuracy was achieved.