High field asymmetric waveform ion mobility spectrometry–mass spectrometry: an investigation of leucine enkephalin ions produced by electrospray ionization

Abstract

High field asymmetric waveform ion mobility spectrometry (FAIMS) provides atmospheric pressure, room temperature, low-resolution separation of gas-phase ions. The FAIMS analyzer acts as an ion filter that can continuously transmit one type of ion, independent of m/z. The combination of FAIMS with electrospray ionization and mass spectrometry (ESI-FAIMS-MS) is a powerful technique and is used in this study to investigate the cluster ions of leucine enkephalin (YGGFL). Separation by FAIMS of leucine enkephalin ions having the same m/z ( m/z 556.5), [M + H] + and [2M + 2H] 2+, was observed. In addition, four complex ions of leucine enkephalin, [2M + H] +, [4M + 2H] 2+, [6M + 3H] 3+, and [8M + 4H] 4+, all having m/z 1112, were shown to be separated in FAIMS. Fragmentation of ions as the result of harsh conditions within the mass spectrometer interface (FAIMS-MS) was shown to provide similar information to that obtained from MS/MS experiments in conventional ESI-MS.