Investigations of a W-Rh permanent modifier for the determination of Pb in blood by electrothermal atomic, absorption spectrometry

A tungsten-rhodium coating (250 mug W + 200 mug Rh) on the integrated platform of a transversely heated graphite atomizer (THGA) was used as a permanent chemical modifier for the direct determination of lead in whole blood by electrothermal atomic absorption spectrometry (ETAAS). Blood samples were diluted 1 + 9 with a diluent consisting of 0.2% v/v HNO3 and 0.5% v/v TritonX-100, and 12 mul of the diluted sample was deposited on the platform. With use of the W-Rh modifier, tube lifetime was improved by a factor of 2-3 when compared with a conventional NH4H2PO4 modifier. With a standard THGA tube, use of the W-Rh permanent modifier allows simple calibration with aqueous standard solutions for blood Pb measurement. However, matrix-matched calibration is still necessary when an end-capped THGA tube is used. The method detection limit (3sigma) based on integrated absorbance measurements is 1.5 mug dl(-1) (0.092 mumol l(-1)) for the standard THGA and 1.0 mug dl(-1) (0.048 mumol l(-1)) for the end-capped tube. Various blood-based certified reference materials and proficiency testing samples, certified for Pb, were analyzed for validation purposes. All results were well within the range considered acceptable. Analysis of human blood samples for blood Pb measurement provided additional validation data against an established blood Pb ETAAS method that uses phosphate modifier. (C) 2002 Elsevier Science B.V. All rights reserved.