Minimization of Transition Metal Interferences with Hydride Generation Techniques

A new hydride generator has been characterized for use with the acid-NaBH(4) hydride generation systems based on the insertion of a capillary tube into the sample introduction channel of a standard Meinhard nebulizer. The acidic sample and the tetrahydroborate solution are mixed at a merge point 1.5 cm from the end of the nebulizer orifice. Nebulization of the reaction solutions into a 0.7 mL tubular "spray chamber" follows a very short mixing time (less than 0.012 s) of the reagents. This approach permits 10 000 μg/mL Ni(2+) or Cr(3+) to be present in the sample solution without producing any interferences. Additionally, in the presence of Fe(3+) added as a "releasing agent", 5000 μg/mL Co(2+) or 160 μg/mL Cu(2+) can also be tolerated without interference. An 80 ± 2% generation efficiency is attained for the test element selenium. A detection limit of 6 μg/L (3σ(b)) is achieved with ICP-AES detection. Precision of replicate measurements at the 12 μg/L level varies from 5 to 12% relative standard deviation.