GRAPHITE-FURNACE FOR ALTERNATIVE COMBINATION WITH DC ARC OR INDUCTIVELY COUPLED PLASMA - INTRODUCTION AND ANALYSIS OF SOLID SAMPLES

A graphite furnace and d. c. arc combined source with the use of halogenating atmosphere in the furnace is described. The construction makes possible the introduction and analysis of both liquid and solid samples at minimum risk of contamination. Spectrographic detection resulted in background equivalent mass values below 10 ng for 22 from 36 elements applied in solution (Ar + CCl4 atmosphere and NaCl matrix). The intensity-time profiles indicated high rates of distillation of the impurities (including B, Cr, Hf, Mo, Ti, V, W and Zr) from silicon carbide and silicon nitride samples in the first 40 s of heating under chlorination (CCl4 vapour). Two versions of the exit part of the furnace are described for coupling to an ICP source; one of them has been used for the determination of titanium in alumina spectrometric detection). Standardization with solution standards for solid sample analysis was unsuccessful. Based on the analytical curve obtained with variable amounts of solid standards (5-20 mg), a detection limit of 0.32-mu-g/g Ti was found for 20 mg alumina.