ELEMENTAL MASS-SPECTROMETRY USING A HELIUM MICROWAVE PLASMA TORCH AS AN ION-SOURCE

An investigation was performed to evaluate the coupling of a 150 W atm ospheric pressure helium microwave plasma torch (MPT) with mass spectr ometric detection. The interface of an existing inductively coupled pl asma mass spectrometer was modified to sample the helium plasma. Optim ization studies illustrate the dependence of analytical signals on var ious instrumental parameters, including sampling depth, gas and sample solution flow rates, and ion optic settings. With the use of a pneuma tic nebulization-desolvation sample introduction system, detection lim its for seven non-metallic elements range from 12 ng/ml to 1.0 mug/ml, comparable to those determined with an Ar ICP and the same mass spect rometer. Interference effects of concomitant cations and isotope ratio s for Cl and Br are also presented.