Aerosol deposition direct sample insertion for ultra-trace elemental analysis by inductively coupled plasma mass spectrometry

Abstract

Direct deposition of a liquid sample as an aerosol into an inductively heated graphite direct sample insertion probe is described as a means of preconcentration and high efficiency sample introduction for ICP-MS. A two minute deposition at 0.25 ml min^–1 resulted in 3s detection limits ranging from 0.06 to 1.8 pg ml^–1(0.03–0.9 pg) for the eight elements studied. These limits represent an element specific improvement averaging two orders of magnitude over the nebulizer/spray chamber-based sample introduction detection limits on the same instrument. The effect of varying several parameters related to the ICP and the deposition process was investigated. The performance of the system with samples in an ethanol matrix was also demonstrated. The deposition and insertion procedure was automated, providing RSDs of approximately 5% at the 1 ng ml^–1 level. Analytical accuracy was assessed by replicate measurements of a Riverine Water Reference Material for Trace Metals (SLRS-2, National Research Council of Canada). Good agreement between calculated and certified values was obtained.