Precise determination of minor alloyed elements in steel by glow discharge optical emission spectrometry with pulsed-voltage modulation technique

A pulsed-voltage was applied to a glow discharge lamp for a modulation detection technique in d.c. glow discharge optical emission spectrometry. Emission signals from the glow discharge plasma were modulated by a cyclic variation in the discharge voltage so that only the desired signals would be detected without any noise with a lock-in amplifier. Molybdenum and vanadium determinations in a steel sample having contents of several 0.001 mass% was performed to estimate the analytical precision. The relative standard deviations of the intensities of the Mo I 379.65 nm and the V II 310.10 nm were 0.2-0.6% in the modulation method, whereas they were 2.6-3.6% in a conventional detection method. Compared with the result by the conventional detection method, the modulation method yielded a better precision in the analytical values. This technique contributes to the precise determination of minor elements alloyed in steels.