A new torch for analysis of samples having exceptionally high total dissolved solids by axially-viewed inductively coupled plasma optical emission spectrometry

Abstract

A primary advantage of the axially-viewed ICP is the excellent sensitivity compared with a radially-viewed ICP. However, there has been a limitation in the ability of the axially-viewed plasma to analyse samples of exceptionally high total dissolved solid (TDS) content because of salt deposition in the injector tube of the torch. This limitation has often meant that many high TDS samples have to be diluted or subjected to other treatment prior to measurement. This paper discusses a new torch that can handle samples such as a 25% NaCl solution, whilst providing excellent detection limits. Analytical performance of this new high TDS torch is characterised and compared with that of a conventional axially-viewed torch. It provides performance similar to that of a standard axially-viewed torch, plus the capability of continuous operation with high TDS solutions without any blockage occurring in the sample introduction system. Internal standardisation further improves long-term stability by a factor of 4. Recoveries in 25% NaCl solution and in brine solution were in the range 100 ± 10%.