Mercury speciation by capillary gas chromatography with radiofrequency hollow cathode glow discharge atomic emission detection

Abstract

Hollow cathode (HC) glow discharge (GD) atomic emission spectrometry (AES) with a radiofrequency (rf) source was investigated as a detector in gas chromatography (GC) for elemental speciation of methylmercury, ethylmercury and inorganic mercury following a Grignard derivatisation reaction (butylmagnesium chloride). The HC design and the transfer line between the source and the GC column are described; in addition, the parameters governing the discharge (pressure, He flow rate, rf power) on the emission of the analytes were optimised. The analytical performance characteristics of this hyphenated technique were evaluated and compared with those of other more common plasmas used as atomic detectors in GC. The absolute detection limits were found to be 0.2, 0.2 and 0.3 pg for methylmercury, ethylmercury and inorganic mercury, respectively, with the variability being lower than 8% RSD at the 10 pg level. Finally, the accuracy of the proposed methodology was successfully tested by analysing two certified reference materials from the National Research Council of Canada (DORM-2 and DOLT-2).