From fundamentals to applications: recent developments in atmospheric pressure photoionization mass spectrometry

Abstract

Only five years after the first publication on atmospheric pressure photoionization (APPI), this technique has evolved rapidly as a very useful complement to established ionization techniques for liquid chromatography/mass spectrometry (LC/MS). This is reflected in a rapidly increasing number of publications in this field. On the one hand, thorough studies into the photoionization mechanism have provided deep insights into the roles and influences of the solvent, the dopant and other additives. On the other hand, a large number of new and attractive applications have recently been introduced. New instrumental developments have resulted in combined APPI/ESI (PAESI) and APPI/APCI sources and a microfabricated APPI source. In this review, the most important developments within the field are summarized, focusing in particular on the applications of the technique.

Ionization mechanism of negative ion-direct analysis in real time: A comparative study with negative ion-atmospheric pressure photoionization

“…They have found wide applications in the quantification of pharmaceutically, biologically, and environmentally significant compounds of various origins. Of the three traditional API methods, APPI is the latest developed [8,9] and is anticipated to expand the polarity range of analytes amenable to LC/API-MS to include low-polarity compounds [15,16]. So far, LC/PI-APPI-MS has been demonstrated to be effective in the analysis of hydrophobic lipids [17,18] and compounds containing conjugated aromatic rings [8, 19 -24].…”

Negative ion-atmospheric pressure photoionization: Electron capture, dissociative electron capture, proton transfer, and anion attachment

“…Due to a different ionization process as compared to ESI and APCI, LC/APPI-MS is anticipated to expand the polarity range of analytes amenable to LC/MS to include low polarity compounds [3,4]. Unfortunately, there has been little progress reported thus far [5].Low polarity compounds with positive electron affinities (EA) can be ionized via an electron capture (EC) mechanism. Traditionally, gas chromatography electron capture-negative ion chemical ionization-mass spectrometry (GC/EC-NICI-MS) has been one of the most sensitive and specific analytical methods, and has been widely used in the analysis of natural electrophores and other compounds after electrophoric derivatization [6].…”

“…Due to a different ionization process as compared to ESI and APCI, LC/APPI-MS is anticipated to expand the polarity range of analytes amenable to LC/MS to include low polarity compounds [3,4]. Unfortunately, there has been little progress reported thus far [5].…”

Theory and Practice of UHPLC and UHPLC–MS

“…Reviews of APPI-MS, including recent advances in this field, have been provided by, among others, Marotta et al (2003), Raffaelli and Saba (2003), Tubaro et al (2003), Syage et al (Syage, 2004;Syage et al, 2004Syage et al, , 2008, Hanold et al (2004), Robb and Blades (2005, 2006, Kauppila et al (2005Kauppila et al ( , 2014Kauppila et al ( , 2017, Bos et al (2006), Purcell et al (2006), , and Marchi et al (2009).…”