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

A method for the direct elemental analysis of low-alloyed steels is de scribed. Spark ablation coupled with excitation in a 1.5 kW argon indu ctively 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 spect rometry, For aerosol production, a medium-voltage spark at a high repe tition 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 mo re uniform particle size distribution is achieved, thereby improving t he precision of the measurements and preventing deposition of material in the torch injector and sampling cone, Particles re-collected downs tream of the cyclone device were mostly spherical in shape, with a par ticle diameter of less than 1.0 mu m. When using optimized operating p arameters, and a low abundance iron isotope (Fe-58) as an internal sta ndard, relative standard deviations at concentration levels of ten tim es 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), respective ly. 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 r eference materials SS-456/1 to SS-460/1, carbon steels (residual serie s).