Comparison of the Performance of a Laboratory-built High Resolution Glow Discharge Mass Spectrometry With That of a Quadrupole Inductively Coupled Plasma (Glow Discharge) Mass Spectrometer for Boron and Gadolinium Isotopic Analysis

Abstract

A double focusing glow discharge mass spectrometer (HR GDMS system) was developed from a spark source mass spectrometer to allow isotopic measurements directly on solid samples. The effects on signals of the discharge cell geometry, including anode–cathode distance and aperture diameter of the anode, are discussed. A comparison was made, after optimization of operating parameters, between this system and a quadrupole mass spectrometer with an inductively coupled plasma and a glow discharge as ion sources [quadrupole ICP-(GD)MS system]. The comparison included spectral characteristics, isobaric interferences and stability measurements. HR GDMS was applied to B isotope ratio measurements in Zr samples; these measurements cannot be performed with quadrupole GDMS because of an isobaric interference between¹⁰B⁺ and Ar⁴⁺. The two GDMS systems were also used for Gd isotopic determinations; however, for large samples (greater than 55 mm in diameter), only HR GDMS offers the possibility of isotopic analysis, owing to the design of the quadrupole GDMS sample holder. ICP-MS was employed to obtain isotopic measurements of these two elements on the same samples after dissolution. The accuracy and precision of the results are discussed and compared with those obtained by thermal ionization mass spectrometry (TIMS), used as a reference technique.