Solid Phase Microextraction as Sample Introduction Technique for Radio Frequency Glow Discharge Mass Spectrometry

Abstract

Solid phase microextraction (SPME) was used for sampling and sample introduction directly to a mass spectrometer with an rf glow discharge ion source (rf GDMS). Aqueous solutions of tetraethyllead (TEL) were analyzed at 200 ppt concentration level. TEL was extracted by the SPME fibre from the headspace of vigorously stirred samples. The analytes were then flash desorbed from the fibre in a dedicated injector connected directly to the rf glow discharge ion source of a mass spectrometer. Flash desorption resulted in narrow peaks, with very good signal to noise ratios. The spectra obtained could be used for both quantification and compound identification based on the molecular fragment ions produced. TEL and tetramethyltin were also introduced together to the rf GDMS system. Both compounds produced very good spectra that could be used for quantification.

In general, organometallic compounds are substantially more toxic to humans than the inorganic compounds from which they are derived. Therefore, to assess the issue of toxicity, both the inorganic and organometallic forms of the element need to be determined and quantified, thus driving chemical speciation into the area of trace elemental analysis.