TIME-RESOLVED STUDIES OF THE EFFECTS OF WATER-VAPOR IN GLOW-DISCHARGEMASS-SPECTROMETRY

The role of water vapor as an impurity in glow discharge mass spectrom etry is examined by means of pulsed injection of water into an argon d ischarge. The effect of water vapor on both analyte and intrinsic gas species is determined. Water dissociates in the discharge to produce r eactants that can influence analytical results. The extent of this eff ect is dependent on the reactivity of the cathode sample with water an d its dissociation products. Metal oxides are observed during and shor tly after the pulsed water injection. Three different cathode material s (titanium, iron, and copper) are studied, with a range of metal oxid e bond strengths. Titanium, which has strong gettering action in the g low discharge plasma, exhibits the shortest perturbation time after ad dition of water vapor. The experiments show the need to remove trace w ater from glow discharges for best analytical results.