Elemental mass spectrometry using a moderate power microwave-induced plasma as an ion source

Abstract

A moderate power microwave-induced argon plasma operated at atmospheric pressure is evaluated as an ion source for mass spectrometry. Data are presented which illustrate a non-homogeneous distribution of the analyte ions throughout the plasma requiring sampling from a position where molecular oxide and hydroxide formation is favoured. Effects of sampling depth, plasma power and argon flow-rate on the ion signals are discussed. Major background ions present in the argon microwave induced plasma (Ar MIP) are similar to those encountered in the argon inductively coupled plasma (Ar ICP). Detection limits using this laboratory-built instrument, range from 7 to 70 ng ml^–1 depending on the ionisation potential. The effects of concomitant elements are much more severe with the Ar MIP than with the Ar ICP using the same instrument.