A comparison of argon and mixed gas plasmas for inductively coupled plasma-mass spectrometry

Abstract

The effects of adding N 2 to the outer gas flow of an Ar plasma in inductively coupled plasma mass spectrometry (ICP-MS) are illustrated. With 5% N 2 added to the outer gas flow and provided the central (nebulizer) gas flow is increased, modest signal enhancements (up to a factor of 4) are observed. The degree of enhancement depends on the extent to which an element forms a strong metal oxide bond and also, to some extent, on ionization potential. An important feature of N 2 mixed gas plasmas for ICP-MS is that the signals for analyte oxide species (MO +) and certain background species (ArO +, ArOH +, Ar 2 +, ClO +, and ArCl +) are significantly reduced (an order of magnitude) by the addition of N 2 to the outer gas flow. In addition to these observations, some results are also presented for O 2 and air (outer gas) mixed gas plasmas and N 2 (central gas) mixed gas plasmas.