Determination of trace metals in volatile organic solvents using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry

Abstract

A desolvation system has been designed to help facilitate the introduction of volatile organic solvents into inductively coupled plasmas. The system utilizes Peltier coolers to reduce the temperature of an interface placed between a heated spray chamber and the plasma torch. The interface consists of a drilled aluminium block that acts as a heat-sink and through which pass glass cooling tubes. The Peltier coolers are mounted around the block, sandwiched between the block itself and a series of copper cooling plates. The optimum conditions necessary for the determination of trace amounts of metals in diethyl ether are discussed and the results obtained using these conditions compared with those obtained using a conventionally cooled mini-spray chamber. Detection limits, using the system in conjunction with continuous nebulization, were found to be in the low to sub-µg l^–1 range for inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. Flow injection techniques have also been used to reduce the amount of volatile organic solvent entering the plasma. In this instance the volatile solvent (diethyl ether) was carried in a stream of less volatile solvent (2-ethoxyethanol) to the plasma. The effects of varying the sample loop volume have been investigated, and the results compared with those obtained using continuous flow nebulization. The results indicated that, in addition to achieving an enhancement in plasma stability, smaller sample loops (50 µl) facilitate faster flow rates, which result in better shaped transient peaks and reduced memory effects.