Application of low-cost electrothermal vaporization capacitively coupled plasma microtorch optical emission spectrometry for simultaneous determination of Cd and Pb in environmental samples

Abstract

The study discusses the applicability and analytical capability of a laboratory miniaturized system including a small-sized electrothermal vaporizer with Rh filament and a low power (15W) and low Ar consumption (150mlmin−1) capacitively coupled plasma microtorch interfaced with a low resolution microspectrometer for the simultaneous determination of Cd and Pb in environmental samples by optical emission spectrometry. Ten-microliter samples were dried (100°C, 80s) and vaporized (1500°C, 6s) by filament heating, then sample vapor was introduced into plasma via an Ar stream and 20 successive emission episodes were recorded with 500ms integration time per episode. The operating parameters of the electrothermal vaporization device and plasma were optimized in order to achieve the simultaneous determination of the two elements with best analytical performance. The method was verified by analyzing CRMs of soil, and then applied to real samples digested in aqua regia. The standard addition method was used to compensate for the non-spectral matrix effects on the analytical signal. Under the optimized conditions the limits of detection were 130±35μgkg−1 (13pg) for Cd at 228.802nm and 2100±175μgkg−1 (210pg) for Pb at 368.346nm. Recovery was in the range 98±18% for Cd and 103±11% for Pb for 95% confidence interval, while the relative standard deviation of repeatability was 4–12% (n=3). The investigated instrumentation has analytical potential and prototyping perspective to be used for toxic element determination in environmental samples.