Lead determination by HG-MIP OES with nitrogen plasma after a variable optimization study

Abstract

A hydride generation nitrogen microwave induced plasma optical emission spectrometry (HG-MIP OES) system was developed for lead determination. Plumbane chemical generation was performed using 0.045 mol L⁻¹ K₃Fe(CN)₆ as the additive in acidic medium and 2.0% w/v NaBH₄ in 1% w/v NaOH as the reductant. The additivated sample and the reductant were pumped towards a cyclonic chamber where hydride generation and separation from the solution occurred. Operating conditions such as the additive and reductant concentration, sample, reductant and nitrogen flow-rate, the cyclonic chamber stabilization time and the viewing position in the torch were optimized. A meticulous study of the variation of the nitrogen plasma response as a function of the hydrochloric acid concentration was carried out. The analytical performance of the method was studied and its applicability evaluated in a Trace Element in Water Certified Reference Material and a Soil Reference Material. The method performance in terms of limits of detection and quantification (0.54 μg L⁻¹ and 1.8 μg L⁻¹ Pb, respectively) was found comparable to other atomic spectrometry techniques. This is to our knowledge the first research on the analytical performance of lead determination by PbH₄ generation and determination by MIP OES.