SPARK ABLATION AS SAMPLING DEVICE FOR INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRIC ANALYSIS OF LOW-ALLOYED STEELS

A method for the direct elemental analysis of low-alloyed steels is described. Spark ablation coupled with excitation in a 1.5 kW argon inductively coupled plasma was applied to the direct determination of Mn, Si, P, Al, B, Co, Nb, V, Zr and Sb in low-alloyed steels by mass spectrometry, For aerosol production, a medium-voltage spark at a high repetition rate (500 V, 400 Hz) was used. A cyclone device was designed to control the aerosol particle size; with this system the total amount of material reaching the plasma is low (about 4 mu g min(-1)) and a more uniform particle size distribution is achieved, thereby improving the precision of the measurements and preventing deposition of material in the torch injector and sampling cone, Particles re-collected downstream of the cyclone device were mostly spherical in shape, with a particle diameter of less than 1.0 mu m. When using optimized operating parameters, and a low abundance iron isotope (Fe-58) as an internal standard, relative standard deviations at concentration levels of ten times the detection limit were below 2.5%, Detection limits (3s) for Nb, V, Zr, Mn, Co, Al and Sb ranged from 0.08 to 0.32 mu g g(-1); for Si, B and P, detection limits were 1.5, 2.1 and 2.5 mu g g(-1), respectively. These values are comparable to those obtained for continuous-flow sample aspiration of a 0.05% m/v Fe matrix solution, The technique was applied to the analysis of the Bureau of Analysed Samples certified reference materials SS-456/1 to SS-460/1, carbon steels (residual series).