Frontiers in elemental analysis by mass spectrometry

The development of iodine based impinger solutions for the efficient capture of Hg0 using direct injection nebulization-inductively coupled plasma mass spectrometry analysis

Inductively coupled plasma mass spectrometry (ICP/MS) with direct injection nebulization (DIN) was used to evaluate novel impinger solution compositions capable of capturing elemental mercury (Hg0) in EPA Method 5 type sampling. An iodine based impinger solution proved to be very efficient for Hg0 capture and was amenable to direct analysis by DIN-ICP/MS. Hg0 capture efficiency using aqueous iodine (I3-) was comparable to Hg0 capture using acidified potassium permanganate impinger solutions which were analyzed by cold vapor atomic absorption spectrometry (CVAAS), with greater than 98% capture of Hg0 in the first oxidizing impinger. Using DIN-ICP/MS, it was demonstrated for the first time that iodine can be generated just prior to impinger sampling for efficiently oxidizing Hg0 and retaining it in solution as HgI4(2-). Due to the increased interest in Hg speciation from combustion sources and the potential for using DIN-ICP/MS for multiple metals analyses, an impinger sampling train for gaseous Hg speciation and multiple metals analyses using DIN-ICP/MS analyses is presented. The unique feature of such a sampling train is that each impinger solution in the series is amenable to direct analysis by DIN-ICP/MS. A bituminous coal was combusted in a bench scale coal system, and gaseous Hg species (oxidized and elemental) were determined using the proposed impinger train. The DIN-ICP/MS instrumental detection limit was 0.003 ppb, and MDLs ranged from 0.007 to 0.116 microg/L (ppb) in a variety of impinger solutions used for Hg capture.

Elemental speciation by liquid chromatography-inductively coupled plasma mass spectrometry with direct injection nebulization

A new version of the direct injection nebulizer (DIN) is used to interface liquid chromatographic (LC) separations with element-selective detection using inductively coupled plasma mass spectrometry (ICP-MS). The DIN injects all of the sample into the ICP and has a dead volume of less than 1 microliter. Charged species of arsenic and tin are separated as ion pairs on a micro-scale (1 mm i.d.), packed, reversed-phase column. Detection limits are 0.2-0.6 pg for arsenic and 8-10 pg for tin. For methanol + water eluents, the signal is highest at 25% methanol and stays within 25% of this maximum as the methanol fraction is varied from 20 to 80%. Compared with LC-ICP-MS with conventional nebulizers, the absolute detection limits and chromatographic resolution are substantially superior, and the dependence of analyte signal on solvent composition is somewhat less severe with the DIN.