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Evaluation of the optimization space for atmospheric pressure photoionization (APPI) in comparison to APCI

Fredenhagen, Andreas and Kuehnoel, Juergen (2014) Evaluation of the optimization space for atmospheric pressure photoionization (APPI) in comparison to APCI. Journal of mass spectrometry, 49 (8). pp. 727-736.


For this study 30 compounds were selected that were not suitable for ESI with a wide variety of functional groups and investigated with APCI and APPI in the positive and negative ion mode. The influence of the mobile phase (eluents containing acetonitrile or methanol) and - for APPI - four different dopants were explored.

APPI was especially useful for compounds, where the M●+ and not the [M + H]+ was formed. The dopants chlorobenzene and anisole promoted the formation of molecular ions M●+ for about half of the compounds, while with the dopants toluene and acetone mostly the [M + H]+ was observed. The formation of M●+ was also positively influenced by the use of mobile phases containing methanol at a linear rate. Best results were generally achieved with the dopant chlorobenzene, establishing that this dopant is suitable for a wide set of compounds. In the negative ion mode APPI offered no advantage towards APCI indicating the superior usefulness of APPI in the positive mode.

For one quarter of the compounds significantly better results were achieved with mobile phases containing methanol for both APPI and APCI than those with acetonitrile, but only in the positive mode. Despite the very diverse set of compound structures, the overlap between APPI and APCI was quite high. With either of the methods – APPI or APCI – about 10 % of the compounds were not detected. Strategies to get results quickly with difficult unknowns will be discussed based on this study.

Item Type: Article
Date Deposited: 13 Oct 2015 13:13
Last Modified: 13 Oct 2015 13:13


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