IMPROVED SLURRY SAMPLING ELECTROTHERMAL VAPORIZATION SYSTEM USING A TUNGSTEN COIL FOR INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

An improved ETV system for the determination of trace elements in dive rse samples by slurry sampling ETV-ICP-AES is presented. It consists o f a tungsten coil vaporizer, a simple computer controlled power supply with high reproducibility of the output voltage and a fast and effici ent data acquisition and processing system for the short transient sig nals. Coupling the ETV system with the spectrometer and control of add itional 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 significa ntly reduced by coating the coil with tungsten carbide and by a decrea se in the concentration of traces of oxygen in the Ar-H-2 carrier gas using a high-voltage discharge cell. The tungsten ablation was investi gated 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 loss es were found to be in the range from 7% (La) to 54% (Cu).