Effect of H2/Ar mixtures on the analysis of conducting and insulating materials by radiofrequency glow discharge mass spectrometry

The effect of the addition of hydrogen to a radiofrequency-argon glow discharge coupled to a time of flight mass spectrometer has been studied. Pressure and forward power conditions in the discharge were kept constant. The hydrogen concentrations added to the argon plasma gas were 0.5%, 1% and 10% v/v and two types of homogeneous samples were investigated: a conducting material (nickel-base) and two glasses. A decrease of the dc-bias voltage with increasing H-2 concentration was observed at every forward power assayed. For the nickel material, the analytical signals turned out to be higher in 10% H-2/Ar and 1% H-2/Ar discharges than in pure Ar, while for 0.5% H-2/Ar the increases were just obtained at the lowest power assayed. Concerning the glass samples, signal increases were obtained at the powers assayed for most analytical signals using 0.5% H-2/Ar instead of pure Ar.