Separation of Different Ion Structures in Atmospheric Pressure Photoionization-Ion Mobility Spectrometry-Mass Spectrometry (APPI-IMS-MS)

• Published in: Journal of the American Society for Mass Spectrometry 2010-09, Vol.21 (9), p.1565-1572
• Main Authors: Laakia, Jaakko, Adamov, Alexey, Jussila, Matti, Pedersen, Christian S., Sysoev, Alexey A., Kotiaho, Tapio
• Format: Article
• Language: English
• Subjects: Adducts; Analytical Chemistry; Atmospheric Pressure; Bioinformatics; Biotechnology; Cations; Cations - chemistry; Chemistry; Chemistry and Materials Science; Desorption; Drift; Drift tubes; Hexanes - chemistry; Ionic mobility; Ions; Mass spectra; Mass spectrometry; Naphthol; Naphthols - chemistry; Organic Chemistry; Oxygen - chemistry; Photochemistry - methods; Photoionization; Proteomics; Pyridines - chemistry; Radicals; Scientific imaging; Solvents; Solvents - chemistry; Spectrometry, Mass, Electrospray Ionization - methods; Spectroscopy; Tandem Mass Spectrometry - methods; Toluene; Toluene - chemistry
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/j.jasms.2010.04.018

This study demonstrates how positive ion atmospheric pressure photoionization-ion mobility spectrometry-mass spectrometry (APPI-IMS-MS) can be used to produce different ionic forms of an analyte and how these can be separated. When hexane:toluene (9:1) is used as a solvent, 2,6-di- tert-butylpyridine (2,6-D tBPyr) and 2,6-di- tert-4-methylpyridine (2,6-D tB-4-MPyr) efficiently produce radical cations [M] +· and protonated [M + H] + molecules, whereas, when the sample solvent is hexane, protonated molecules are mainly formed. Interestingly, radical cations drift slower in the drift tube than the protonated molecules. It was observed that an oxygen adduct ion, [M + O 2] +·, which was clearly seen in the mass spectra for hexane:toluene (9:1) solutions, shares the same mobility with radical cations, [M] +·. Therefore, the observed mobility order is most likely explained by oxygen adduct formation, i.e., the radical cation forming a heavier adduct. For pyridine and 2- tert-butylpyridine, only protonated molecules could be efficiently formed in the conditions used. For 1- and 2-naphthol it was observed that in hexane the protonated molecule typically had a higher intensity than the radical cation, whereas in hexane:toluene (9:1) the radical cation [M] +· typically had a higher intensity than the protonated molecule [M + H] +. Interestingly, the latter drifts slower than the radical cation [M] +·, which is the opposite of the drift pattern seen for 2,6-D tBPyr and 2,6-D tB-4-MPyr. Positive ion atmospheric pressure photoionization ion mobility spectrum of 2,6-di- tert-butylpyridine measured with IMS-Faraday plate detector.