Separation of different ion structures in atmospheric pressure photoionization-ion mobility spectrometry-mass spectrometry (APPI-IMS-MS)

Abstract

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-DtBPyr) and 2,6-di-tert-4-methylpyridine (2,6-DtB-4-MPyr) efficiently produce radical cations [M] ϩ· and protonated [M ϩ H] ϩ 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 ϩ O 2 ] ϩ· , which was clearly seen in the mass spectra for hexane:toluene (9:1) solutions, shares the same mobility with radical cations, [M] ϩ· . 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] ϩ· typically had a higher intensity than the protonated molecule [M ϩ H] ϩ . Interestingly, the latter drifts slower than the radical cation [M] ϩ· , which is the opposite of the drift pattern seen for 2,6-DtBPyr and 2,6-DtB-4-MPyr. (J Am Soc Mass Spectrom 2010, 21, 1565-1572) © 2010 American Society for Mass Spectrometry I n ion mobility spectrometry (IMS) ions move through an applied electric field in a drift gas flow [1]. Interactions between analyte ions and the drift gas result in a specific drift time for that ion, which is often converted to the reduced mobility (Formula 1) [1,2]. Several general reviews of IMS exist [1,[3][4][5][6][7][8] and the theory behind drift tube ion mobility spectrometry has been presented in detail elsewhere [2,9].where l d ϭ length of the drift region, t d ϭ drift time of ion, V ϭ voltage drop over the drift region, T ϭ temperature, and P ϭ pressure.The most common IMS devices are stand-alone instruments, which are commonly used to screen the environment for significant chemicals such as warfare agents, explosives, and illegal drugs [1, 10 -12]. These devices are often tuned to detect certain chemicals; when more specific information is required, IMS is often combined with other instruments, for example with gas chromatography (GC-IMS) [4,13]. Ion mobility spectrometry-mass spectrometry (IMS-MS) is also becoming more and more popular in various application fields, especially in bioanalysis [5]. Several different types of ion mobility spectrometers have been combined with mass spectrometers, e.g., drift tube IMS-MS [1,5,14], field asymmetric ion mobility spectrometry (FAIMS-MS) [5,[15][16][17], and also an aspiration IMS method has been combined with MS [18]. In bioanalysis, a common application of IMS-MS is structural studies ...

Review on Ion Mobility Spectrometry. Part 1: current instrumentation

“…Other ionization methods are Atmospheric Pressure Photo Ionization (APPI) 66 based on ultraviolet light (UV) 67 . APPI will ionize those molecules with an ionization potential lower than the energy of photons emitted.…”

Detection of gas traces using semiconductor sensors, ion mobility spectrometry, and mass spectrometry

“…The fundamental behavior of acetate monomers and dimers was studied 48 for a better understanding of the influence of dimer formation in ion mobility spectrometry. An analysis of literature [49][50][51][52][53][54][55][56][57][58][59] and studies in MEPhI [46][47][48][60][61][62][63][64] allowed determining how, why, and when the complex or complementary applications of devices based on SGS and IMS-MS are possible in medical study. A very compact MEPhI printed circuit board drift tube is presented in Figure 3.…”

“…37,38 Sample preparation is allowed for by Tedlar bags, [39][40][41] needle traps, 16,42 SPME, 18,43 sample loops 43 and different adsorbents. This article focuses on SGS 44,45 SGS and ion mobility spectrometry-mass spectrometry systems 2,5,46,47 (IMS-MS) for detailed comparison between this equipment. Main usage principles of both IMS-MS and SGS methods in the complex analysis are illustrated below.…”

Rapid Identification of Triphenylmethane Dyes by Ion Mobility Time-of-Flight Mass Spectrometry

“…Drift tube conditions were similar to those described previously. [42][43][44] The electric field strength across the drift region was 298 V cm -1 . Pure nitrogen (99.96%) was used as a drift gas, supplied by a NitroGen N300DR gas generator (Peak Scientific Instruments, US) and introduced into the drift region at 0.5-2 L min -1 flow rate.…”