Multivariate study in chemical vapor generation for simultaneous determination of arsenic, antimony, bismuth, germanium, tin, selenium, tellurium and mercury by inductively coupled plasma optical emission spectrometry

Abstract

Chemical vapor generation (CVG) of arsenic, antimony, bismuth, germanium, tin, selenium, tellurium and mercury was investigated in a multivariate way. Similarities and differences between the elements were highlighted by principal component analysis and the combined effect of operating conditions on the analytical signals by CVG-ICP-OES studied according to empirical modeling and experimental design methods. In order to better understand the observed trends, variations of plasma excitation conditions while changing reductant concentration, sample acidity and carrier gas flow rate were investigated by using Pb II 220.353 nm to Pb I 217.000 nm line intensity ratio as diagnostic parameter. Changes in the vapor generation efficiencies were also evaluated by CVG-ETAAS measurements. In this way, it was possible to distinguish the effects on the vapor generation efficiency from those on the ICP source. Moreover, the results made it possible to select the operating conditions suitable for simultaneous multi-elemental determination. By using 2% NaBH₄, 0.8 M HCl and Ar flow rate of 0.25 L min⁻¹, optimal plasma robustness and excellent analytical performances were obtained for all the analytes, despite the different chemical conditions required for the vapor generation. Particularly, it was found that Sn and Ge can be reasonably determined together with the other elements, with satisfactory analytical performances, although with a notable decrease in sensitivity with respect to their optimum. Detection limits for simultaneous determination of As, Sb, Bi, Ge, Sn, Se, Te and Hg were 0.13, 0.14, 0.13, 0.61, 1.62, 0.19, 1.32 and 0.21 μg L⁻¹, respectively. Finally, high time-correlation among the analytical and background signals was highlighted, thereby efficiently compensating for signal fluctuations by internal standardization and improving both repeatability and background stability.