DETERMINATION OF TRACE AMOUNT OF BISMUTH IN IRON AND STEEL BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY WITH SAMPLE INTRODUCTION BY ELECTROTHERMAL VAPORIZATION

The performance of an inductively coupled plasma-mass spectrometer with an electrothermal vaporizer (ETV-ICP.MS) has been investigated as a function of several parameters associated with ETV operation. Signal profiles of bismuth in some acid solutions were measured using a pyro-coated graphite tube as the ETV device. Signal appearance time of bismuth in nitric acid was later than that in hydrochloric acid and the signal intensity of bismuth in nitric acid was lower than that in hydrochloric acid. The use of nickel as a modifier for bismuth in nitric acid improved the intensity to those of bismuth in hydrochloric acid and in aqua regia. The detection limit at the sub-picogram level which was 50-fold better than that obtained by nebulization with ICP.MS was obtained. This method was applied to the determination of bismuth in iron. The detection limit of 0.01 ppm which was 20-fold better than that obtained by nebulization with ICP.MS was obtained. However the signal intensity of bismuth in iron solution was depressed to the half of those obtained without iron and there was no effect of nickel as a modifier on the improvement of the sensitivity. Bismuth in some certified reference materials of iron which were dissolved in aqua regia was determined, and the results agreed with reference values.