High-effective ionization during ferrous analyses using a He glow-discharge ion source was investigated. The respective relationships between the ionization potential (
Ip) of each element and various ionic strengths were studied in detail for He glow discharge and Ar glow discharge. The energies of the helium metastable atom (He
m) is 1910 kJ/mol (19.80 eV) and 2022 kJ/mol (20.96 eV). It is presumed that He
m contributes to creation of doubly-charged and singly-charged ions. Results show that numerous doubly-charged ions are generated by He glow discharge. If this ratio is greater than that of an internal standard element Fe, the RSF-value becomes greater than 1 (the ionic strength ratio decreases). Furthermore, with elements having
Ip2 of more than approximately 18 eV,
e.g., Ni, As, P, and C, the relative ionic strength of doubly-charged ion with respect to the singly-charged ion is only several percent at the highest. Consequently, the RSF-values approach unity (1). High-effective ionization by glow discharge is dependent upon the type of discharge gas, the matrix (internal standard element) and analyzing element, the presence of spectral interference, RSF-value, and other factors.
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