Towards the use of ion mobility mass spectrometry derived collision cross section as a screening approach for unambiguous identification of targeted pesticides in food

Mass spectrometry is a vital tool for molecular characterization, and the allied technique of ion mobility is enhancing many areas of (bio)chemical analysis. Strong synergy arises between these two techniques because of their ability to ascertain complementary information about gas-phase ions. Ion mobility separates ions (from small molecules up to megadalton protein complexes) based on their differential mobility through a buffer gas. Ion mobility-mass spectrometry (IM-MS) can thus act as a tool to separate complex mixtures, to resolve ions that may be indistinguishable by mass spectrometry alone, or to determine structural information (for example rotationally averaged cross-sectional area), complementary to more traditional structural approaches. Finally, IM-MS can be used to gain insights into the conformational dynamics of a system, offering a unique means of characterizing flexibility and folding mechanisms. This Review critically describes how IM-MS has been used to enhance various areas of chemical and biophysical analysis.

This review article compares and contrasts various types of ion mobility-mass spectrometers available today and describes their advantages for application to a wide range of analytes. Ion mobility spectrometry (IMS), when coupled with mass spectrometry, offers value-added data not possible from mass spectra alone. Separation of isomers, isobars, and conformers; reduction of chemical noise; and measurement of ion size are possible with the addition of ion mobility cells to mass spectrometers. In addition, structurally similar ions and ions of the same charge state can be separated into families of ions which appear along a unique mass-mobility correlation line. This review describes the four methods of ion mobility separation currently used with mass spectrometry. They are (1) drift-time ion mobility spectrometry (DTIMS), (2) aspiration ion mobility spectrometry (AIMS), (3) differential-mobility spectrometry (DMS) which is also called field-asymmetric waveform ion mobility spectrometry (FAIMS) and (4) traveling-wave ion mobility spectrometry (TWIMS). DTIMS provides the highest IMS resolving power and is the only IMS method which can directly measure collision cross-sections. AIMS is a low resolution mobility separation method but can monitor ions in a continuous manner. DMS and FAIMS offer continuous-ion monitoring capability as well as orthogonal ion mobility separation in which high-separation selectivity can be achieved. TWIMS is a novel method of IMS with a low resolving power but has good sensitivity and is well intergrated into a commercial mass spectrometer. One hundred and sixty references on ion mobility-mass spectrometry (IMMS) are provided. 2008 John Wiley & Sons, Ltd