Accurate mass liquid chromatography/mass spectrometry on quadrupole orthogonal acceleration time-of flight mass analyzers using switching between separate sample and reference sprays. 2. Applications using the dual-electrospray ion source

A new electrospray dual sprayer, LockSpray, was developed for accurate mass measurements on a quadrupole orthogonal acceleration time-of-flight mass s pectrometer (oa-Q-ToF). With the dual-sprayer ion source, both sprays are o rthogonal to each other. A mechanism similar to the one employed on the mul tiplexed electrospray source (MUX) allows switching between reference and s ample sprayer, The reference sprayer is optimized for low now rates, wherea s the sample sprayer is a conventional Z-spray type sprayer. Earlier work u sing a modified MUX ion source on an orthogonal acceleration time-of-flight instrument showed promising results. In this paper, examples obtained with the LockSpray, specifically designed for accurate mass measurements on an oa-Q-ToF, are presented. The examples include results obtained for the iden tification of impurities in drug substances such as cimetidine and rosiglit azone, using accurate mass tandem mass spectrometry in both positive and ne gative ion electrospray modes, Good mass accuracies, i.e., within 2 mDa of the theoretical value, were obtained in MS and MS/MS operation.