The effect of drift gas on the separation of active pharmaceutical ingredients and impurities by ion mobility-mass spectrometry

The effect of drift gas and binary gas mixtures on the separation of active pharmaceutical ingredients and related compounds has been investigated for the first time using tri-wave ion mobility-mass spectrometry. The drift times for [M+H](+) ions were measured in argon, carbon dioxide, nitrogen, helium and binary mixtures of these gases as a function of pressure and drift gas composition. At the same drift cell pressure the drift times of the protonated ions decreased in order: carbon dioxide > argon > nitrogen > helium. The drift times of compounds in the different drift gases were dependent on the polarizability of the drift gas, the size of the drift gas and the reduced mass of the analyte ion/drift gas pair. Resolution of the active pharmaceutical ingredients Lamotrigine and Rosiglitazone increased with drift cell pressure for argon and nitrogen, but showed no significant increase in carbon dioxide. Enhanced selectivity is demonstrated for the separation of pharmaceutical components using binary drift gas mixtures in tri-wave IM-MS. (C) 2009 Elsevier B.V. All rights reserved.