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 heated graphite atomiser (THGA) was used as a permanent chemical modifier for the determination of lead in biological materials by slurry sampling in electrothermal 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 atomiser for delivering 20 microL slurry aliquot ranged from 5,100 to 39,000. The permanent W-Rh modifier remained stable during approximately 300 analytical measurements when 20 microL of slurries containing up to 1.5% m/v were delivered into the atomiser. In addition, the permanent modifier increases the tube lifetime by approximately 100% when compared to untreated integrated platforms. Also, there is less decrease of sensitivity during the atomiser lifetime when compared with the conventional modifiers, resulting in a decreased need of re-calibration during routine analysis and consequently increasing the sample throughput. The atomiser lifetime was limited to the THGA wall durability, because the W-Rh treated platform was intact after more than 650 analytical firings in a medium containing up to 1.5% m/v slurry of biological material. The detection limit based on integrated absorbance was 20 ng g(-1) Pb for 1.50% m/v slurries. Results from the determination of lead in slurries of biological materials using the W-Rh permanent modifier were in agreement with those obtained with digested solutions using Pd + Mg(NO3)2.