Determination of impurities in organometallic compounds dissolved in diethyl ether by flow injection inductively coupled plasma mass spectrometry

Abstract

A novel method of introducing organometallic samples dissolved in volatile organic solvents into an inductively coupled plasma mass spectrometer is described and characterized. Small volumes of organic solvent are injected into a carrier stream of dilute nitric acid (2%) using a flow injection valve. The uptake rates employed are typical of those used for aqueous samples (1–4 cm³ min^–1) and the volume of sample used is such that the plasma remains stable throughout the study. The optimum operating conditions for this process, determined using the variable step size simplex procedure, are discussed in detail. The detection limits obtained are in the ng cm^–3 range. The results obtained with the above technique are compared with those obtained using a modified sample introduction system incorporating a membrane dryer tube for desolvation. This modification improves the sensitivity to facilitate detection limits at the sub-ng cm^–3 level. Finally the determination of metallic impurities present at levels of the order of 1 ng cm^–3 in two organometallics, trimethylgallium and methyllithium, both stabilized in diethyl ether, is reported.