Investigation of the quasi-simultaneous arrival (QSA) effect on a CAMECA IMS 7f-GEO.

QSA undercounting could compromise isotope ratio analyses requiring ~1 × 105 counts per second for the major isotope and primary currents <20 pA. The error could be >8‰ for a 1 pA primary current. However, correction can be accurately applied. For instrumental mass fractionation (IMF)-corrected data, the magnitude of the error resulting from not correcting for QSA is dependent on the difference in secondary ion count rate between the unknown and standard analyses. Copyright © 2017 John Wiley & Sons, Ltd.