Determn. of metals by atomic absorption spectrophotometry - using graphite tube coated with rhenium followed by tungsten

摘要

A hollow tubular body comprises a graphite substrate coated at least partially with a layer (I) of rhenium a few microns thick, followed by a layer (II) of tungsten between several tens and several hundreds of microns thick. Alternatively the substrate may be coated only with Re, several tens to several hundred microns thick. The layers are pref. obtd. by the decompsn. of ReF6 or WF6 in H2 at high temp. and low pressure. The coated tube is pref. used in appts. for atomic absorption spectrophotometry for the determn. of metals forming carbides which are stable at high temp., esp. Cr, Ca, Mo, V, W, Ti, Zr, Hf, Ta, Nb, where a soln. of the metal is carried by a gas into the tube, which is above 2000 degrees C so the metals are atomised. Atomic absorption spectrophotometry can now by rapidly, accurately and economically used for determn. of metals forming stable carbides which previously led to false results. By coating the graphite tube with rhenium followed by tungsten the carburisation of the outer layer of W by the graphite is precluded and accurate determn. of the above metals is possible.