OPTIMIZATION OF SECONDARY CATHODE THICKNESS FOR DIRECT-CURRENT GLOW-DISCHARGE MASS-SPECTROMETRIC ANALYSIS OF GLASS

Direct current glow discharge mass spectrometry can be used for the an alysis of solid non-conducting samples by application of the secondary cathode technique. In the work reported, the thickness of this second ary cathode, a conducting diaphragm placed in front of the sample, was evaluated. Variation of the secondary cathode thickness results in a variation of the electrode configuration and of the discharge voltage required for stable atomization of the non-conductor, Both parameters were evaluated separately using conducting samples. Thickness and volt age were found to have an opposite effect on the sample signal intensi ty obtained and on the crater shape created. Generally, it could be co ncluded that, for the determination of elements at low concentrations in glass plates, a thin secondary cathode is preferable, but that the use of a thick secondary cathode results in a flatter crater profile, which is important for depth profiling.