THE APPLICATION OF A DOUBLE VOLTAGE MODULATION TECHNIQUE TO A GLOW-DISCHARGE SOURCE WITH A SUPPLEMENTARY ELECTRODE

The Ar spectral lines are suppressed in glow discharge source atomic e mission spectroscopy by a double voltage modulation technique with a s upplementary electrode. The voltage is modulated between two levels, t ypically 350 and 700 V. At the lower voltage level mainly the Ar emiss ion occurs where at the higher voltage level both the Ar and the metal atoms sputtered from the sample contribute to the emission. The power supply of the supplementary electrode is switched on when the glow di scharge passes from operation at 700 V to 350 V. The intensity of argo n gase lines is regulated by the current applied to the supplementary electrode at that period. Therefore, there is no need for electronical amplification and lower voltage adjustment of two operation modes. Th is modified DVM technique has been applied to the determination of Si and Cu in Al-samples. The suppression of Ar lines is possible, and the elements can be determined without Ar interferences.