Plasma jet desorption atomization-atomic fluorescence spectrometry and its application to mercury speciation by coupling with thin layer chromatography.

A novel plasma jet desorption atomization (PJDA) source was developed for atomic fluorescence spectrometry (AFS) and coupled on line with thin layer chromatography (TLC) for mercury speciation. An argon dielectric barrier discharge plasma jet, which is generated inside a 300 μm quartz capillary, interacts directly with the sample being analyzed and is found to desorb and atomize surface mercury species rapidly. The effectiveness of this PJDA surface sampling technique was demonstrated by measuring AFS signals of inorganic Hg(2+), methylmercury (MeHg), and phenylmercury (PhHg) deposited directly on TLC plate. The detection limits of the proposed PJDA-AFS method for inorganic Hg(2+), MeHg, and PhHg were 0.51, 0.29, and 0.34 pg, respectively, and repeatability was 4.7%, 2.2%, and 4.3% for 10 pg Hg(2+), MeHg, and PhHg. The proposed PJDA-AFS was also successfully coupled to TLC for mercury speciation. Under optimized conditions, the measurements of mercury dithizonate (Hg-D), methylmercury dithizonate (MeHg-D), and phenylmercury dithizonate (PhHg-D) could be achieved within 3 min with detection limits as low as 8.7 pg. The combination of TLC with PJDA-AFS provides a simple, cost-effective, relatively high-throughput way for mercury speciation.