The development of the ion trap as a detector for Liquid Chromatography

Since its commercial introduction as a detector for LC in 1995 the ion trap has arguably been more significant than any other mass analyser in making mass spectrometry accessible to a broad range of chromatographers. The ion trap itself has undergone more technical innovations in its short lifetime than any other detector for LC.

HPLC coupled to the atmospheric pressure ionisation (API) source, with its production of ions external to the mass analyser made this a very robust, sensitive and easy to use LC/MS interface. Before the introduction of the ion trap, detectors based upon the quadrupole were the most widely used for LC/MS. Whilst the triple stage quadrupole (TSQ) was, and still is, the workhorse for quantitative analysis they suffered from a lack of sensitivity for qualitative work which required full scan information. The API techniques generated molecular weight information but tandem MS experiments were needed to obtain structural information. The introduction of the ion trap suddenly made it possible for anyone, even with very little experience, to obtain MS/MS spectra from low level chromatographic components. The sorts of experiments which had previously been the domain of the “expert” mass spectrometrist were now available to all. The ion trap also had the unique feature of being able to generate multiple stages of MS/MS known as MSn. This opened up new areas of structural work that could be undertaken with LC /MS analysis.