A novel analytical system with a capacitively coupled plasma microtorch and a gold filament microcollector for the determination of total Hg in water by cold vapour atomic emission spectrometry

Abstract

A novel, miniaturized analytical system of high sensitivity and precision based on atomic emission in a capacitively coupled plasma microtorch (13.56 MHz, 20 W, 200 mL min⁻¹ Ar) equipped with a gold filament microcollector and a microspectrometer was investigated for total Hg determination in water. The method is based on cold vapour generation using SnCl₂ and preconcentration on the microcollector followed by thermal desorption for 5 s and emission measurement at 253.652 nm. The microcollector consists of a gold filament of 80 μm diameter, 24 cm length and 43 turns encapsulated in a quartz capillary of 2.5 mm i.d., 4 mm o.d. supplied at 1.5 A. Due to very low thermal inertia, the fast, direct heating of the filament provides a high flow rate of Hg vapour toward plasma and hence sensitivity of the analytical system in the sub-ng L⁻¹ Hg range. The optimal working conditions and figures of merit of the system are presented for Hg determination in drinking and river water, leachate of polyethylene terephthalate bottles and food packaging of biodegradable materials. At concentrations in the range of 0.06–57.4 ng L⁻¹ the precision was 0.9–7.0%. The detection limit in solution was 0.02 ng L⁻¹, while the absolute value was 0.5 pg. Validation of the system was carried out by analyzing a certified groundwater (ERM-CA615) that gave a recovery of 101 ± 2% for the certified concentration of 37.0 ± 0.4 ng L⁻¹. The novel system can be prototyped as a substitute for existing systems based on atomic fluorescence or absorption.