Direct analysis of gaseous mercury in ambient air by gas to particle conversion-gas exchange ICPMS

For the first time, direct analysis of gaseous mercury (Hg) at a concentration level of a few ng m(-3) in ambient air using the gas to particle conversion-gas exchange technique, coupled with inductively coupled plasma mass spectrometry (ICPMS) has been achieved. Gaseous Hg was converted tomercury oxide (HgO) and agglomerated with ammonium nitrate (NH4NO3) particles by a gas to particle conversion device (GPD). The agglomerates were consequently introduced and measured by ICPMS through a gas exchange device (GED). The time-resolved signals from gaseous Hg in ambient air could be obtained by GPD-GED-ICPMS with a 10 ms dwell time for ICPMS, which demonstrated the real-timemonitoring of gaseous Hg with high temporal resolution. No sample pretreatment procedures such as pre-concentration or separation of gaseous Hg from air, were needed before the introduction of gaseous Hg into GPD-GED-ICPMS. Longer dwell times of the ICPMS, such as 100 ms, 500 ms and 1000 ms revealed more stable time-resolved signals. A limit of detection (LOD) for gaseous Hg from the calibration curve was estimated to be ca. 0.12 ng m(-3) when a longer dwell time of 1000 ms was selected. Since the LOD observed was sufficiently low compared to the background concentration level of ca. 2 ng m (3) in Japan, the GPD-GED-ICPMS technique is expected to be used for highly sensitive, direct and real-time monitoring of gaseous Hg in ambient air as well as for working and living environments.