Use of nitric acid in sample pretreatment for determination of trace elements in various biological samples by ETAAS

Trace elements in liquid biological samples may be determined by direct ele ctrothermal atomic absorption spectrometry (ETAAS). In our previous work it was found that samples containing proteins or DNA may leak out of the grap hite tube before the drying step, despite the addition of various modifiers . In order to keep the sample to the graphite tube, samples were diluted be fore analysis 1 + 1 with 32% v/v nitric acid, or 5 mu l of 32% v/v nitric a cid was added to the graphite tube before ETAAS determination. Applying the proposed procedure, the concentrations of lead in eluted fractions after g el chromatographic separation of human cerebellar nucleus dentatus supernat ant and platinum in isolated DNA samples were determined. The use of nitric acid in sample pretreatment prevent sample leakage out of the graphite tub e, provided for even drying and considerably reduced nonspecific absorption in lead determination. The repeatability of measurements was better than /- 6%. The accuracy of the procedure was checked by spiking samples. The re coveries for both elements lay between 93-104%. Nitric acid was found to be a better modifier than TRITON X-100. (C) 2000 Elsevier Science B.V. All ri ghts reserved.