ELECTROTHERMAL VAPORIZATION-ICP-MS FOR THE DETERMINATION OF METALS INMICRO-AMOUNTS OF HIGH-PURITY NONMETALS (P, AS, SB, S, SE, TE, I)

A thermal trace-matrix separation procedure has been developed for the determination of ultra-traces of metals in solid non-metals (P, As, S b, S, Se, Te and I). These matrices are dissolved in high-purity hydro gen peroxide to form the corresponding acids. By applying a suitable t emperature profile, coating the graphite tube with WC and using hydrog en as a gaseous modifier more than 90% of the matrix can be removed. A nalyte recoveries are 90 to 105% with a standard deviation of 5 to 10% . Since the separation principle is not specific, nun-metallic analyte s show poor recoveries of 10 to 40% (20-100% RSD), Elements forming pe rsistent carbides, such as refractory metals, require either HF or fre on as rut additional modifier: Separation of the matrix leads to highe r-sensitivities, fewer spectral and non-spectral interferences and to better precision. The graphite tube is only little contaminated and it s lifetime is drastically increased, The improvements result in limits of detection in the lower pg/g-range in the solid non-metals. Further more, this method can be employed for amounts of sample around 1 mg at absolute detection limits below 1 pg. Best performance of the couplin g of ETV to ICP-MS is only obtained in the single-ion monitoring mode which means only semi-sequential multielement capabilities.