Hydride generation-point discharge microplasma-optical emission spectrometry for the determination of trace As, Bi, Sb and Sn

A miniaturized optical emission spectrometer (OES) with point discharge (PD) helium-hydrogen microplasma as an excitation source and hydride generation (HG) for sample introduction was constructed for the determination of trace As, Bi, Sb and Sn. Hydrogen generated from the HG process usually consumes part of the excitation capability of a microplasma, but here it was used to effectively minimize the background spectral emission of the microplasma, thus enabling more spectral emission lines with less background spectral interferences for analysis of more elements. In addition, separation of analyte-containing hydride from the sample solvent and matrix prior to excitation in the microplasma was achieved with better sensitivity, selectivity and stability. The compact PD was constructed using two tapered tungsten electrodes powered by alternating current (ac) high voltage, and emission spectra were recorded with a hand-held charge coupled device (CCD) spectrometer. Limits of detection (LODs) of 7, 1, 5 and 2 mu g L-1 and relative standard deviation (RSD) of less than 5% were obtained for As, Bi, Sb and Sn, using 234.984 nm, 306.770 nm, 259.805 nm and 317.504 nm as the analytical lines, respectively. The potential application of this miniaturized instrumentation was also demonstrated by successfully analyzing several Certified Reference Materials (CRMs) with satisfactory results.