Evaluation of Alternative Plasma Gases for Radio-Frequency Glow Discharge Mass Spectrometry (rf GD-MS)

Abstract

Interferences are a major consideration in all forms of plasma mass spectrometry. Investigations into the use of He, Ne, N2, and Kr in radio-frequence glow discharge mass spectrometry (rf GD-MS) have been undertaken to study their potential as alternative plasma gases. All gases exhibited expected behavior with respect to pressure and power. Background species are discussed for each gas, along with the effect of each gas on analyte intensities in Standard Reference Material (SRM) copper 500. A helium plasma yields the highest intensities for analytes (Cr, Fe, Ni, Co, Zn, As, Se, Ag, Au, Pb, and Bi) of all gases investigated. Kr was not a practical alternative gas since analyte intensities were extremely low, severe memory effects were present, and the UHP Kr is very expensive. Relative sensitivity factors are presented for each of the gases for the same copper SRM 500. Argon has the highest sputter rate, with Ne and He being similar and N2 being the lowest. Isotope abundances are given for Se, Fe, Br, and Cl in a He plasma.