Use of controlled atmospheres to minimize matrix effects in the spectrographic analysis of tool steels

Abstract

Sample excitation conditions which produce a black burn have been compared with normal excitation and have been found to result in an appreciable reduction in matrix effects in the analysis of tool steels. These black burns are the result of the deposition of graphite from the counter-electrode upon the sample surface and were obtained with high-voltage spark excitation by introducing nitrogen or argon into the analytical gap. Black burns were also obtained in ambient air by employing a slightly oscillatory low-voltage condensed-arc discharge with the sample as anode. A less pronounced reduction in matrix effects was observed with violent-burn conditions. Violent burns were obtained by introducing oxygen into the analytical gap and employing a potent spark discharge.