High-sensitivity detection of selenium and arsenic by laser-excited atomic fluorescence spectrometry using electrothermal atomization

Abstract

High-sensitivity detection of the trace elements selenium and arsenic is reported. The method applied is laser-excited atomic fluorescence spectrometry using electrothermal atomization within a graphite furnace atomizer. For the production of tunable laser radiation in the vacuum ultraviolet (VUV) spectral region a laser system was developed that consists of two laboratory-built dye lasers pumped by a Nd:YAG laser. The laser radiations are subsequently frequency doubled and sum frequency mixed by non-linear optical KDP or BBO crystals, respectively. The system works with a repetition rate of 20 Hz and provides output energies of up to 100 µJ in the VUV at a pulse duration of 5 ns. The investigations focused on the detection of selenium and arsenic in aqueous solutions and in samples of human whole blood. From measurements on aqueous standards, detection limits of 1.5 ng l^–1 for selenium and 5.4 ng l^–1 for arsenic were obtained, with corresponding absolute detected masses of only 15 or 54 fg, respectively. The linear dynamic ranges spanned six orders of magnitude and good precision was achieved. In the case of human whole blood samples, the recovery was found to be within the range 96–104%. The determination of the selenium content yielded medians of 119.5 ± 17.3 µg l^–1 for 200 frozen blood samples taken in 1988 and 109.1 ± 15.6 µg l^–1 for 103 fresh blood samples.