Feasibility study of low pressure inductively coupled plasma mass spectrometry for qualitative and quantitative speciation

Abstract

Low-pressure ICPs (LP–ICPs) formed with helium have been utilized as ion sources for MS. In the first part of the paper a description is given of a plasma operated at 90 W forward power, used to ionize organotin and organolead compounds introduced by GC, with detection limits of 11, 2 and 14 pg obtained for tetraethyltin (TEtSn), tetrabutyltin (TBuSn) and tetraethyllead (TEtPb), respectively. The same plasma operated at 45 W forward power yielded fragment ions of TEtSn and TBuSn. In the second part, a customized mass spectrometer for use with an LP–ICP is described. The optimum power for the generation of fragment ions of perfluorotributylamine (PFTBA) was found to lie between 5 and 8 W. Two optima for skimming distance were observed, at 6 and 8 mm downstream of the sampler orifice. Mean ion kinetic energies for fragment ions of PFTBA at 69,219 and 502 m/z were 1.2, 1.7, and 2.1 eV, respectively, at 6 W forward power, but increased when the power was increased to 8 W. Molecular and other fragment ions were observed for chloro-, iodo- and dibromobenzenes introduced using GC.