Improvement in the single and simultaneous generation of As, Bi, Sb and Se hydrides using a vapor generation accessory (VGA) coupled to axially viewed inductively coupled plasma optical emission spectrometry (ICP OES)

Abstract

Continuous flow (CF) hydride generation (HG) using a vapor generation accessory (VGA) coupled to a simultaneous axially viewed inductively coupled plasma optical emission spectrometer (ICP OES) for the ultrasensitive measurement of As, Bi, Sb and Se was investigated. Hydrides were generated in a gas–liquid phase separation system by mixing acidified aqueous sample, additional HCl and reductant (NaBH₄) solutions on-line. Instrumental (emission line wavelength, RF power, and flow rates of the sample and waste solutions, along with the sample read delay and wash times) and chemical (concentrations of NaBH₄ and HCl in the sample (S) and additional acid (A) solutions) variables affecting the effectiveness of HG were examined to achieve the optimum conditions for single- and multi-element analysis. The limitations of the HG reaction due to potential interference effects between the hydride-forming elements were identified. Satisfactorily, As and Sb hydrides could be generated in a wide range of HCl concentrations either in the S solution or the A solution, i.e. 1–6 (S) or 5–10 (A) mol L⁻¹ HCl. For Bi and Se, HG depended strongly on the acidity and the optimum HCl concentrations for both elements were completely opposite. HG for Bi was the best at the lowest acidity (1 (S) and 5 (A) mol L⁻¹ HCl), whereas the maximum Se responses were acquired using the highest HCl concentrations (6 (S) and 10 (A) mol L⁻¹ HCl). Compromised conditions for the simultaneous measurement of As + Bi + Sb or As + Sb + Se, without any adverse interactions between the elements, were successfully established with an analysis time of ∼2 min per sample. Under these conditions, the detectability of all the elements was improved greatly (2 orders of magnitude versus ICP OES). Linear concentration ranges (0–20 ng g⁻¹), detection limits from 0.027–0.099 ng g⁻¹ and a precision better than 2% (as RSD) were achieved.