SLURRY SAMPLING ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY FOR TRACE-ELEMENT ANALYSIS OF HIGH-PURITY TUNGSTEN TRIOXIDE

A slurry sampling ETAAS method for the determination of trace concentr ations of Ca, Co, Cr, Cu, Fe, K, Mg, Na and Ni in tungsten trioxide is presented. A high background absorption appearing with large sample a mounts during atomization at high temperatures was the only matrix int erference observed. It could be significantly reduced by volatilizatio n of the matrix in the pyrolysis step. Calibration curves recorded wit h aqueous standards could be used for calibration in all cases excludi ng the de termination of very low analyte concentrations of Co and Fe which required the use of the standard additions method. The results o btained by this method showed an excellent agreement with those determ ined in digests by ETAAS. The detection limits achievable by the slurr y technique were between 1 (Ca, K, ME, Na) and 210 (Cu) ng/g. They wer e mostly by more than one order of magnitude better than those of the solution techniques.