ABSTRACT
Atmospheric pressure photoionization (APPI) has recently been introduced as a new ionization method for LC-MS (1-3). The photoionization detector (PID) has long been used as a detection method for gas chromatography (GC) (4-7), but it has also been applied to LC (8-10). Photoionization at atmospheric pressure has been described in connection with ion mobility spectrometry and mass spectrometry (11-13), but before the work of Bruins et al. (1), it had not been used with LCMS. Two distinct APPI apparatuses have been described by Bruins et al. (1) and Syage et al. (2); both share the same operational principles.
