Lead determination in slurries of biological materials by ETAAS using a W-Rh permanent modifier

A tungsten-rhodium coating on the integrated platform of a transversely hea ted graphite atomiser (THGA) was used as a permanent chemical modifier for the determination of lead in biological materials by slurry sampling in ele ctrothermal atomic absorption spectrometry (ETAAS). Slurries were sonicated during 20 s before being delivered to the previously W-Rh treated platform . The number of particles of biological materials introduced into the atomi ser for delivering 20 muL slurry aliquot ranged from 5,100 to 39,000. The p ermanent W-Rh modifier remained stable during approximately 300 analytical measurements when 20 muL of slurries containing up to 1.5% m/v were deliver ed into the atomiser. In addition, the permanent modifier increases the tub e lifetime by approximately 100% when compared to untreated integrated plat forms. Also, there is less decrease of sensitivity during the atomiser life time when compared with the conventional modifiers, resulting in a decrease d need of re-calibration during routine analysis and consequently increasin g the sample throughput. The atomiser lifetime was limited to the THGA wall durability, because the W-Rh treated platform was intact after more than 6 50 analytical firings in a medium containing up to 1.5% m/v slurry of biolo gical material. The detection limit based on integrated absorbance was 20 n g g(-1) Pb for 1.50% m/v slurries. Results from the determination of lead i n slurries of biological materials using the W-Rh permanent modifier were i n agreement with those obtained with digested solutions using Pd + Mg(NO3)( 2).