Evaluation of a microwave desolvation system in inductively coupled plasma mass spectrometry with low acid concentration solutions

Abstract

The behaviour of a desolvation system based on microwave heating (termed a microwave desolvation system, MWDS) with low acid concentration solutions was evaluated in inductively coupled plasma mass spectrometry. Studies included water, sulfuric acid, perchloric acid, nitric acid and hydrochloric acid. The best performance of the MWDS was obtained at low liquid uptake rate and low acid concentrations. The analytical behaviour of the MWDS depends on the nature and composition of the solution used. In comparison with water, acid solutions provide up to four times higher ion intensities for the elements tested. In comparison with nitric and hydrochloric acid, sulfuric and perchloric acid provide higher ion intensities but also higher CeO⁺/Ce⁺ ratios whereas Ba²⁺/Ba⁺ ratios are lower. The limits of detection (LODs) are of the same order of magnitude for all acid solutions used, unless the specific isotope/solvent combinations suffer from spectral interference. In comparison with the conventional sample introduction (CS) without desolvation system the MWDS provides between 2 and 14 times higher ion intensities for the isotopes tested. For nitric and hydrochloric acid solutions the MWDS gives rise to lower CeO⁺/Ce⁺ratios and higher Ba²⁺/Ba⁺ ratios. For sulfuric and perchloric acid these tendencies are the opposite. For the isotopes that are not subject to interference, the LODs obtained with the MWDS are up to a factor of 10 lower than those obtained with CS.