Infrared heating of commercially available spray chambers to improve the analytical performance of inductively coupled plasma optical emission spectrometry

摘要

In an attempt to improve the figures of merit of inductively coupled plasma optical emission spectrometry (ICPOES), a ceramic beaded infrared (IR) rope heater and a ceramic IR block heater were compared for heating each of a Scott double-pass spray chamber and a baffled cyclonic spray chamber up to 200 degrees C. A SeaSpray nebulizer was used in all cases. Following multivariate optimization, under compromise conditions for the determination of 29 elements, robustness, as assessed by the Mg ii (280.270 nm)/Mg i (285.213 nm) emission intensity ratio, increased from 8.6 at room temperature to 12.0-12.6 for the four IR-heated systems. Furthermore, the detection limit improved by, on average, 2-3 fold with the rope heater and 5-10 fold with the block heater. In fact, for a given spray chamber, the improvement in detection limit was similar or less than the improvement in sensitivity with the IR rope heater, whereas the improvement in detection limit was significantly higher than that in sensitivity with the IR block heater, demonstrating the superior performance of IR heating over the combination of convective and IR heating provided by the IR rope heater. The best performance was achieved with a double-pass spray chamber and two IR block heaters, with detection limits improving, on average, by an order of magnitude compared to without heating, with a similar precision (on average, 1.3% relative standard deviation with IR blocks versus 1.5% without heating). In any case, under the resulting very robust conditions, all the IR-heated systems enabled the accurate analysis of a certified reference material of waste water by external calibration, without internal standardization or matrix-matching.