Sono-induced cold vapour generation interfaced with capacitively coupled plasma microtorch optical emission spectrometry: analytical characterization and comparison with atomic fluorescence spectrometry

Abstract

Sono-induced cold vapour generation in 0.2 mol L⁻¹ formic acid has been interfaced for the first time with a low power (10 W) and low argon consumption (100 mL min⁻¹) capacitively coupled plasma microtorch for mercury determination by optical emission using a low resolution microspectrometer. The method meets the requirements of green analytical chemistry in terms of the derivatisation method, cost-effective conditions for plasma generation and miniaturized instrumentation. The method is based on sample ultrasonication in a batch reactor, purging of mercury vapour, moisture removal from vapour in a Nafion tubing, Hg preconcentration on a gold filament microcollector, thermal desorption and introduction of mercury vapour into plasma via an Ar stream. Emission episode spectra of Hg were recorded at 253.652 nm. Under the optimized conditions, a detection limit of 5.0 ± 0.3 ng L⁻¹ was found, which was better than the 12 ng L⁻¹ obtained by atomic fluorescence spectrometry after chemical cold vapour generation with SnCl₂. The analytical capability of the new method was demonstrated by analysing the certified reference materials and real samples of fish tissue, soil and sediment mineralized in an acidic mixture. The method is highly sensitive and the matrix effects associated with cold vapour generation were avoided by sample dilution. Mercury was determined using external calibration with recovery and precision in the range of 96.3–104.5% and 0.8–7%, respectively. No systematic error against atomic fluorescence with chemical cold vapour generation using SnCl₂ was observed.