desorption electrospray ionisation (DESI)

An ionisation technique that takes place outside of the mass spectrometer, at ambient temperature and pressure. A fine spray of charged droplets, formed by pneumatically assisted electrospray ionisation at high potential, typically 2-5 kV, is directed towards the sample on a surface. Ions produced from the sample are drawn into the mass spectrometer via a vacuum interface. Most surfaces and analytes are amenable and no sample preparation or pre-separation is required. Analytes may be analysed in situ, such as explosives on luggage, drugs in urine and metabolites in tissue.