EFFECTS OF HYDROGEN MIXED WITH ARGON CARRIER GAS IN ELECTROTHERMAL VAPORIZATION INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY

In inductively coupled plasma-mass spectrometry with sample introduction by tungsten furnace electrothermal vaporization, the effects of adding hydrogen to the argon carrier gas on the signals of background ions (Ar+, ArH+, N+, O+, OH+) and analyte ions (In+, Tl+, Pb+, Ag+, Bi+, Te+) were investigated. These ion signals increased as the flow rate of hydrogen was increased, and the signal enhancement rates were dependent on the ionization potentials of the test species. An optical fibre system was used to obtain information on the electron number density (n(e)) and excitation temperature (T(ex)) at the interface region between the sampling and skimmer cones. The values of n(e) in the interface plasma were of the order of 10(13) cm-3 and those of T(ex) were about 5400 K, though these values may reflect the characteristics of the barrel shock. Hydrogen addition caused a rise in T(ex) and an increase in n(e) at the interface region. This results in an enhanced ionization of the analytes. An increase in the ion species like Ar+ and ArH+ at the interface region may also promote the ionization through collisions or charge transfer.