Inductively coupled plasma source mass spectrometry using continuum flow ion extraction

Abstract

An inorganic mass spectrometry system is described that uses an atmospheric pressure inductively coupled plasma (ICP) as an ion source. Solution samples may be introduced directly by nebulisation and the analysis time is about 1 min. Ions are extracted from the bulk plasma without any intervening boundary layer so that the full advantages of the ICP as a hightemperature dissociation and ionisation medium are realised. A quadrupole mass analyser is used with a pulse counting ion detector followed by a multi-channel scaler data system. General background levels are low and a wide range of elements may be determined with detection limits below 1 ng ml^–1. Spectra are very simple with few molecular analyte ions and only singly and doubly charged species are found. Mass resolution is adequate to avoid peak overlap and isotope ratio determinations may readily be made with precision below 0.5%, with integration times of about 5 min. The operating characteristics and performance of the system are described and illustrated and the future development potential is discussed.