Evaluation of the comparability of spectra generated using a tuning point protocol on twelve electrospray ionisation tandem-in-space mass spectrometers.

Product ion spectra produced by collision-induced dissociation (CID) in tandem mass spectrometry can yield important structural information on organic compounds which can aid in their identification. However, differences in experimental conditions may have a strong effect on the degree of product ion formation and therefore on the features observed in product ion spectra. For this reason, a common approach for library building is the acquisition of several spectra, typically between 5 and 10, each at a different collision energy level. In this study, the use of an alternative approach was investigated, where a tuning point protocol was applied to tune the instruments in an attempt to standardise CID conditions prior to data acquisition. With this approach, the acquisition of a single mass spectrum was sufficient. The stability of the tuning point was investigated and the choice of a commercially available search package to assess spectral comparability was discussed. Finally, the product ion spectra of 33 compounds were acquired on twelve tandem-in-space instruments, including nine triple quadrupoles, one hybrid triple quadrupole linear ion trap and two quadrupole time-of-flight mass spectrometers, resulting in 2178 spectral comparisons being carried out. The results from the spectral comparisons suggest that the use of a tuning point enables the standardisation of the experimental conditions that affect the degree of product ion formation. Indeed, 84.5% of the comparisons demonstrated a good degree of spectral agreement with match scores greater than 700, which we believe is the minimum score for a tentative library match.