Use of a flow injection hydride generation technique in non-dispersive atomic fluorescence spectrometry

Abstract

The feasibility of using a flow injection (FI) hydride generation technique in conjunction with atomic fluorescence spectrometry (AFS) was investigated. Parameters were established for the determination of Sb, As, Bi, Hg, Se and Te. Among the parameters that were found to have a more pronounced influence on performance were the concentration of NaBH₄, the carrier gas flow, the observation height and the temperature of the atomizer cell. Compared with the manual sampling system (or batch system), the relative detection limits of the FI combination were better by factors of 2.5–10. By using FI, the sample volume was reduced to 500 mm³, hence, the absolute detection limits were even better with improvements of between 10- and 50-fold depending on the element. The absolute detection limit for Se using the FI technique was 0.035 ng, while with the batch system it was 0.8 ng. Similarly, Hg detection limits with the FI technique and the batch system were found to be 0.015 and 0.4 ng, respectively. The best improvement in the absolute detection limits was found for Te, which with the FI technique was 0.02 ng while with the batch system it was 1.0 ng. The linear ranges were typically 2–3 orders of magnitude of analyte concentrations, which is much wider than that of atomic absorption spectrometry. Sampling frequency was typically 120 injections per hour, and since a double-channel AFS instrument was used in this work, pairs of elements such as As, Sb and Bi, Hg were measured simultaneously, which equates to 240 measurements per hour. The technique was applied to the determination of hydride forming elements in geological reference materials.