Inductively coupled plasma mass spectrometric measurement of gallium in ferromanganese crusts from the Sea of Japan

Abstract

Difficulties emerging in determining gallium by inductively coupled plasma mass spectrometry (ICP-MS) are considered in the paper on an example of the determination of this element in ferromanganese crusts from the Sea of Japan. The main interference for gallium isotopes 69Ga and 71Ga was found, associated with overlaps generated by elements as such Ba, Mn, Ce, and Nd, whose concentrations in ferromanganese crusts can be quite high. The potentials of a quadrupole ICP-MS spectrometer with a collision cell for suppressing spectral noise and a high-resolution ICP-MS spectrometer for the determination of gallium are compared. It is found that in the case of the quadrupole mass spectrometer in the mode both with collision cell and without it, the use of isotope 69Ga is extremely difficult because of overlapping with the doubly-charged ion 138Ba2+. In the case of isotope 71Ga, the arising polyatomic interferences, for example, from 55Mn16O+, are successfully eliminated using a collision cell filled with helium; however, this enhances overlaps with 142Ce2+ and 142Nd2+. High-resolution inductively coupled plasma mass spectrometry enables the determination of gallium by both its isotopes; the above interferences are eliminated.