Atmospheric pressure photoionisation

Fast atom bombardment (FAB) Plasma desorption (PD) Liquid secondary-ion mass spectrometry (LSIMS) Thermospray (TSP)/plasmaspray (PSP) Electrohydrodynamic ionisation (EHI) Multiphoton ionisation (MPI) Atmospheric pressure chemical ionisation (APCI) Electrospray ionisation (ESI) Ion spray (ISP) Matrix-assisted laser desorption/ionisation (MALDI) Atmospheric pressure photoionisation (APPI) Triple quadrupole (QQQ) Four sector (EBEB) Hybrid (EBQQ) Hybrid (EB-ToF, Q-ToF) Tandem ToF-ToF Photomultiplier... 

ESI operating in the negative ion (NI) mode has been the interface most widely used for the analysis of anionic perfluorinated surfactants. In addition, ESI has also been optimised for the determination of neutral compounds such as the sulphonamides PFOSA, Et-PFOSA and t-Bu-PFOS. The use of atmospheric pressure photoionisation (APPI) has been explored in few works [78-80]. Takino et al. [78] found as the main advantage of this technology, the absence of matrix effects, but the limits of detection were considerably higher than those obtained by LC-ESI-MS/MS. 

Undoubtedly, mass spectrometric detection has a substantial role to play in condensed-phase chromatographic analyses of toxic impurities. As in GC/MS, it can be highly sensitive, although this is probably more analyte-specific than in GC/MS. Selectivity can be gained by SIM on single quadrupoles or, if necessary, SRM on MS/MS instruments. What must be considered is the appropriate ionisation mode to be used in LC/MS. Most modern instruments use atmospheric pressure ionisation sources, including electrospray ionisation (ESI), atmospheric pressure chemical ionisation (APCI) and more recently atmospheric pressure photoionisation (APPI). 

Jean-Denis, J. B., Pezet, R., Xabacchi, R. (2006). Rapid analysis of stilbenes and derivatives from downy mildew-infected grapevine leaves by Liquid Chromatography-Atmospheric Pressure Photoionisation Mass Spectrometry. J. Chromatogr. A, 1112, 263-268. 

These additives are essentially high boiling point liquids and so the most appropriate technique to use is liquid chromatography (LC-MS). A range of synthetic plasticisers such as phthalates, adipates, mellitates and sebacates can be detected using the atmospheric pressure chemical ionisation (APCl) mode. Process oils are hydrocarbon mineral oils and require either the atmospheric pressure photoionisation (APPl) head (which can ionise nonpolar species) or, where the oil contains sufficient aromatic character, the use of in-line UV or fluorescence detectors. A fluorescence detector is particularly sensitive in the detection of polyaromatic hydrocarbon (PAH) compounds in such oils. 

Gomez-Ariza, J.L., Garcia-Barrera, T. and Lorenzo, F. (2006) Anthocyanins profile as fingerprint of wines using atmospheric pressure photoionisation coupled to quadrupole time-of-flight mass spectrometry, Anal. Chim. Acta, 570(1), 101-108. 

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