ABSTRACT A compact kHz rotating field plasma operated with helium as working gas at ambient atmosphere has been evaluated as a spectrochemical radiation source directly coupled with solid-phase microextraction (SPME) and subsequent thermal desorption (TD), and the suitability of the system for the determination of volatile metallic species has been studied by optical emission spectrometry (OES). Stable doughnut-shaped rotating field plasma with a central channel could be maintained within a wide range of operating conditions. Low power levels of 50-250 W and low He flow rates of 50-1500 mL min-1 were used. A TD unit, consisting of a heated, glass-lined splitless-type GC injector, was connected directly with the dual-flow injector of the plasma approach to minimize the length of transfer line. This arrangement provides fast desorption and high sample introduction efficiency. The system can be combined with a miniaturized spectrometer with CCD detection, whereby avoiding space-angle limitations. The TD-plasma-OES system was used for the recording of time-resolved emission spectra for various analyte vapors at different working conditions. Both direct liquid immersion and headspace modes of SPME sampling can be employed for separation of compounds of interest. The compact combination of SPME, thermal desorption, low cost helium miniplasma source and the miniature OES instrument led to a powerful and sensitive miniaturized system for trace metals analysis. For the selected measurement conditions, the detection limits for As, Se, Cr and Hg were at the low ppb level. The linearity ranges are up to 1000 ng mL-1 and the precision is on the order of 3-7%.
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