Liquid chromatography-mass spectrometry with ionspray and electrospray interfaces in pharmaceutical and biomedical research

Electrospray and ionspray techniques use samples that exist as ions or ion-molecule complexes in solution. After the dispersion of the solution into an electrically charged aerosol, the sample ions may escape from the solution into the gas phase in a region that is at atmospheric pressure. The sample ions are transported into the mass analyser which is operated under a high vacuum. Liquid chromatographs can be coupled to electrospray and ionspray interfaces. Flow injection or continuous infusion of a sample solution (both without the use of a separating column) may be preferred over on-line liquid chromatography-mass spectrometry in certain applications. Electrospray or ionspray is applicable to polar or ionic samples. Weakly polar and apolar samples are not ionized under electrospray or ionspray conditions. Applications of the techniques are in the fields of drug metabolism, natural product analysis and the determination of high molecular weights through the observation of multiply charged ions.