Use of an ion guide collision cell to improve the analytical performance of an inductively coupled plasma time-of-flight mass spectrometer

Abstract

An axial-acceleration inductively coupled plasma time-of-flight mass spectrometer has been equipped with an octopole ion guide/collision cell. Ion-energy experiments prove that instrument duty cycle improves by up to 100% over values determined for conventional ion optics. Both sensitivity and noise were found to decrease with the ion guide in place. Consequently, limits of detection for most elements were found to be comparable to those calculated for conventional ion optics. The exceptions are low-mass ions that enjoy only a relatively small gain in duty cycle and thus exhibited significantly degraded detection capability. Collisional cooling caused the spectral resolving power to improve by up to 80% compared to the conventional optics. Ion chemistry within the collision cell permitted the determination under robust plasma conditions of potassium, calcium, and iron, elements that usually suffer from isobaric overlaps. Improved resolving power helped reduce the adverse effects of hydrocarbon background ions generated by reactions within the ion guide.