OPTIMIZATION OF A NOVEL ETV SYSTEM FOR SOLID SAMPLE INTRODUCTION INTO AN ICP AND ITS APPLICATION TO THE DETERMINATION OF TRACE IMPURITIES IN SIC

The application of a novel electrothermal vaporization unit (ETV) for sample introduction into an inductively coupled plasma (ICP) is described. The system can be used for vaporizing both liquid and solid samples into an ICP or other excitation device. Exchangeable graphite cups can be used for rapid analysis of solid samples without any sample pretreatment. Free programmable, PC controlled heating cycles make it possible to use individual temperature programs to vaporize either organic or inorganic materials. By use of a computer operating parameters of the system, like ETV-temperature program, ETV-carrier gas flow rates, rf-power and observation height have been optimized with regard to the requirements of solid sampling. The system was first developed for steel analysis but was also used for investigation of environmental samples. An additional application of the system is the determination of impurities in ceramic materials like silicon carbide. Investigation indicated that PdCl2 is a useful modifier for destruction of silicon carbide and simultaneous vaporization of the refractory impurities like aluminium, iron, vanadium and titanium. SiC samples from different manufacturers have been analysed. Concentration values of the elements investigated range from 8-950 mu g g(-1). On the assumption that the sample amount is about 5 mg, detection limits of the elements range from 0.3-4.4 mu g g(-1). Relative standard deviations of 2-14% have been found.