Field Asymmetric Waveform Ion Mobility Research Articles

Separation of leucine and isoleucine by electrospray ionization–high field asymmetric waveform ion mobility spectrometry–mass spectrometry

An electrospray ionization (ESI) source was used to generate gas-phase molecular anions of the amino acids leucine and isoleucine ((M–H) −; m/z −130), which were separated by high- field asymmetric waveform ion mobility spectrometry (FAIMS) and detected by quadrupole mass spectrometry (MS). This combination of ESI-FAIMS-MS enabled selective determination of either amino acid in mixtures that contained at least a 625-fold excess of the other. Comparisons with conventional ESI-MS showed a 50-fold improvement in the signal to background ratio for a 1 μM solution of leucine.

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

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.