Simultaneous sampling and analysis for vapor mercury in ambient air using needle trap coupled with gas chromatography–mass spectrometry

A needle trap (NT) technique for simultaneous sampling and analysis of vapor and particle mercury in ambient air using gold wire filled in a syringe needle has been developed. This NT technique relies on gold amalgamation rather than adsorption/absorption to traditional solid-phase microextraction. Hg trapped by Au-amalgamation NT is thermally desorbed in a hot injection port of a gas chromatograph; desorbed Hg is then determined by the coupled mass spectrometer. This simultaneous sampling and analysis technique were optimized, tested, and used for the collection and accurate determination of elemental Hg in ambient air. Linear calibration curves were obtained for Hg sampling by NT when mass spectrometry (MS) was used for detection; they spanned over 4 orders of magnitude. MS offered excellent sensitivity and selectivity. Selected ion monitor (SIM) mode was used for the linear calibration curves. The selected quantitation ion was m/z 202, since m/z 202 was the strongest isotope of mercury mass spectrum. The method was verified with HgCl2 spiked solution samples. An excellent agreement was found between the results obtained for the Hg-saturated air samples and HgCl2 spiked solution samples. The use of the Au-amalgamation gas-sampling needle trap method, for the measurement of Hg in air and Hg2+ water samples, is described herein.