Improving the analytical performance of hydride generation non-dispersive atomic fluorescence spectrometry. Combined effect of additives and optical filters

The effects of tetrahydroborate and acid concentration and the presence Of L-cysteine and thiourea were investigated in the determination of As, Bi an d Sn using continuous flow hydride generation atomic fluorescence spectrome try (HG AFS). The aim was to find conditions allowing the control of those effects exerting negative influence on the analytical performance of the HG AFS apparatus. The effects taken into account were: (i) the radiation scat tering generated by carryover of solution from the gas-liquid separator to the atomizer; GO the introduction of molecular species generated by tetrahy droborate decomposition into the atomizer; and (iii) interference effects a rising from other elements in the sample matrix and from different acids. T he effects (i) and (ii) could be controlled using mild reaction conditions in the HG stage. The effect of FIG conditions on carryover was studied by r adiation scattering experiments without hydride atomization. Compromised HG conditions were found by studying the effects of tetrahydroborate (0.1-20 g l(-1)) and acid (0.01-7 mol l(-1)) concentration, and the addition of L-c ysteine (10 g l(-1)) and thiourea (0.1, mol l(-1)) on the HG AFS signals. T he effect of optical filters was investigated with the aim of improving the signal-to-noise ratio. Optical filters with peak wavelengths of 190 and 22 0 nm provided an improvement of detection limits by factors of approximatel y 4 and 2 for As and Te, respectively. Under optimized conditions the detec tion limits were 6, 5, 3, 2, 2 and 9 ng l(-1) for As, Sb, Bi, Sn, Se and Te , respectively. Good tolerance to various acid compositions and sample matr ices was obtained by using L-cysteine or thiourea as masking agents. Determ ination of arsenic in sediment and copper certified reference materials, an d of bismuth in steel, sediment, soil and ore certified reference material is reported. (9) 2001 Elsevier Science B.V. All rights reserved.