Improved Slurry Sampling Electrothermal Vaporization System Using a Tungsten Coil for Inductively Coupled Plasma Atomic Emission Spectrometry

Abstract

An improved ETV system for the determination of trace elements in diverse samples by slurry sampling ETV–ICP-AES is presented. It consists of a tungsten coil vaporizer, a simple computer controlled power supply with high reproducibility of the output voltage and a fast and efficient data acquisition and processing system for the short transient signals. Coupling the ETV system with the spectrometer and control of additional functions were performed by means of an interface connected to the ETV computer, allowing operation with a high degree of automation. The ablation of tungsten in the vaporization step could be significantly reduced by coating the coil with tungsten carbide and by a decrease in the concentration of traces of oxygen in the Ar–H₂ carrier gas using a high-voltage discharge cell. The tungsten ablation was investigated for aqueous solutions and also for silicon carbide as an example of a refractory matrix. The transport losses of the analyte elements Au, As, Ca, Cr, Cu, Co, Fe, La, Mn, Na, Sb and Sc were determined for several matrices by means of the radiotracer technique. Transport losses were found to be in the range from 7% (La) to 54% (Cu).