Diagnostic investigations of aerosols with varying water content in inductively coupled plasma mass spectrometry

Abstract

Measurements of axial and radial ion intensity distributions and also of ion energy characteristics by a simple bias potential technique, giving a representation of the kinetic energy distributions, have been applied to study the influence of water vapour on the behaviour of aerosols in inductively coupled plasma mass spectrometry. The full range of moisture content has been covered: from dry aerosols generated by solid evaporation to wet aerosols formed by the addition of an increasing amount of water vapour as well as vice versa from pneumatically generated wet aerosols to dry aerosols by applying dehumidification techniques. As an alternative to humidification of a dry aerosol, hydrogen addition was considered. Comparison of results was performed on the basis of identical values for power and nebulizer flow rate, while sampling distance and bias potential were always individually optimized. A strong dependence on the content of water or hydrogen was observed offering a promising opportunity to influence the analytical performance while providing the basis for a consistent interpretation of the results. Exploitation of the method in analysis requires that sampling distance and bias potential be taken into account in optimization procedures in addition to nebulizer flow rate and power, to which optimization procedures have been restricted in most applications so far.