Quantifying low-energy ICP-MS isotope deposition

Abstract

Mass spectrometry (MS) offers an alternative approach to chemical or chromatographic separations to selectively isolate and collect individual isotopes of an element for analytical purposes. During this MS isotopic isolation process, the amount of material deposited on to a target can be conveniently quantified by measuring the ion current or accumulated charge. In this paper we report the first study comparing measurement of isotope deposition amount with separated isotope ion current for isotopes of six different elements (⁸⁸Sr, ¹⁰⁷Ag, ¹³³Cs, ¹⁴⁰Ce, ¹⁷⁵Lu and ²⁰⁵Tl). These isotopes were sequentially deposited on a conductive substrate located in place of the standard electron multiplier in a quadrupole inductively coupled plasma MS. The results indicate good correlation between measured ion current and deposited mass as verified by quantitative analysis. This empirically confirms a means to quantify total mass deposition by ion charge measurements at implantation energies of 5–10 eV.