CHARACTERIZATION AND OPTIMIZATION OF A RADIOFREQUENCY GLOW-DISCHARGE ION-SOURCE FOR A HIGH-RESOLUTION MASS-SPECTROMETER

A radiofrequency (rf) powered glow discharge ion source has been desig ned and coupled to a double-focusing mass spectrometer. An electrical interface has been developed to provide an effective rf power transfer , thereby ensuring rf shielding and grounding, and to couple the ion s ource to the accelerating potential. The device permits the direct ana lysis of almost any solid sample type (conducting, semiconducting and non-conducting). In order to establish optimum conditions for the trac e analysis of solids, mass spectrometric studies of the dependence of ion signal intensities in an rf glow discharge on operating parameters (applied rf power and discharge gas pressure) were carried our. The e nergy distribution of the ion species was measured by the accelerating voltage scan. It was shown that the singly charged atomic ions of the sample have about a 10 eV higher average energy than the discharge an d residual gas ions. An effective energy separation of the analyte ion s from the discharge and residual gas ions was achieved by setting the position and width of the energy window of the double-focusing mass s pectrometer. The optimization of the operating parameters of a glow di scharge ion source and correct adjustment of the ion transfer optics o f a mass analyser permit an improvement in the analytical characterist ics of the elaborated device.