Emission Spectrometric Determination of Manganese and Chromium in Steels with a Dual Cathode Glow Discharge Lamp

Analytical applications of a dual-cathode hollow cathode discharge lamp are investigated and discussed. The lamp consists of three electrodes (anode, intermediate electrode, and cathode). Two individual power supply devices are employed with a pulsed discharge mode to separate the sputtering process occurring in the lamp from the excitation step in the hollow cathode plasma. Discharge voltages are supplied between the anode and the intermediate electrode to generate the plasma in the intermediate electrode. The cathode sputtering is controlled by bias voltages between the intermediate electrode and the cathode (sample). Emission intensities from the sputtered materials strongly depend upon the variation in the bias voltage, while those from the plasma gas hardly change. This effect can lead to selective detection of the emission lines of the sample from the overall emission signals with a modulation technique. Determination of manganese and chromium in steels is attempted by use of the dual-cathode discharge lamp with the sputter modulation method.