Spark ablation as sampling device for inductively coupled plasma mass spectrometric analysis of low-alloyed steels

Abstract

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 µg 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 µm. When using optimized operating parameters, and a low abundance iron isotope (⁵⁸Fe) 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 µg g^–1; for Si, B and P, detection limits were 1.5, 2.1 and 2.5 µg 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).