The analytical characterisation of sub-minute measurement duty cycles in flow injection analysis mass spectrometry, by their carry-over

Abstract

A high-throughput flow injection analysis mass spectrometry system was developed in-house for the purity estimation of multiple parallel combinatorial chemistry syntheses. A Visual Basic application called RackViewer allows a fast and easy on-screen inspection of these estimates at dispersed laboratory workbenches via the corporate computer network. Due to the increasing numbers of samples to be measured, there is an constant incentive to reduce the measurement duty cycle in order to develop faster throughput rates. Consequently, one threat to the accuracy of these purity estimates is surreptitious inter-sample carry-over. By analogy with the computer screen colour rendering of the purity estimates, carry-over was automatically calculated, then colour depicted within RackViewer. In an earlier report, this carry-over visualisation tool facilitated a stepwise reduction in the measurement duty cycle to 70 s, while maintaining median inter-sample carry-over at levels well below 1%. However, a limiting factor in further optimisation was the physical speed of the autosampler’s sampling head. A recent increase in this speed by the autosampler’s manufacturer allowed a second attempt at achieving well characterised sub-minute measurement duty cycles. Six injection variations involving different syringe and loop wash combinations were examined for their characteristic inter-sample carry-over, using over four hundred samples drawn equally from five diverse combinatorial chemistries. One emerged as the best, with a median inter-sample carry-over of 0.01% and a measurement duty cycle of 44 s.