Implementation of low-energy surface-induced dissociation (eV SID) and high-energy collision-induced dissociation (keV CID) in a linear sector-TOF hybrid tandem mass spectrometer

Abstract

In the work reported here, an in-line sector-TOF (time-of-flight) tandem mass spectrometer with a coaxial detector was developed. An advantage of the present design is that the instrument implements both high-energy collision-induced dissociation (keV CID) and low-energy surface-induced dissociation (eV SID) with no hardware manipulations required to switch between the two activation methods. Surface characterization by secondary-ion mass spectrometry is also possible with this design. Gas phase collision-induced dissociation in this sector-TOF requires ion gating of the continuous ion beam and an ion buncher to bring the ions into spatial focus at the focal-point “source” of the offset parabolic field reflectron. The offset parabolic field reflectron provides good resolution over virtually the entire product ion mass range, with no need to step the reflector voltages. For surface-induced dissociation experiments, accomplished with a surface placed after the last reflectron electrode, the electrodes that comprise the CID reflectron are used for deceleration and acceleration of the ion beam before and after it collides with the surface, respectively. The results obtained show successful implementation of keV CID and eV SID in a JEOL HX110A/TOF mass spectrometer. Product ion mass accuracy is better than ±0.4 u for keV CID and ±0.1 u for eV SID. Typical resolutions achieved are 8000–12,000 (for selected ions), 1000 (for keV CID fragments), and 300–400 (for eV SID fragments). This difference in the CID and SID resolution is partially the result of the different total flight times in CID and SID experiments. On the basis of a direct comparison of keV CID and eV SID of protonated leucine enkephalin, SID experiments have a lower detection limit than CID experiments by at least an order of magnitude.