UV photochemical vapor generation–nitrogen microwave induced plasma optical emission spectrometric determination of nickel

Abstract

Photochemical vapor generation (PVG) was utilized for gaseous sample introduction into a nitrogen microwave induced plasma optical emission spectrometer (MIP-OES). The MIP-OES system can provide low-cost analysis due to the use of nitrogen, but the relatively low temperature of the nitrogen microwave plasma makes it susceptible to sample matrix effects. PVG could convert an analyte into a volatile species and effectively separate it from the sample matrix to realize gaseous sample introduction with high transport efficiency. The proposed PVG-MIP-OES was successfully applied for the determination of trace amounts of nickel. Volatile Ni(CO)₄ could be generated when a standard or sample in formic acid solution was exposed to UV irradiation in a photochemical reactor, and it could be subsequently transported to the nitrogen MIP-OES for excitation and detection. Under optimized experimental conditions, a limit of detection (LOD) of 0.3 μg L⁻¹ was obtained with a relative standard deviation (RSD) of 4.8% (100 μg L⁻¹, n = 11), with an 83-fold sensitivity enhancement compared to solution pneumatic nebulization for sample introduction. The method validation was demonstrated by successful analysis of nickel-containing water Certified Reference Material (CRM) and multi-walled carbon nanotubes.