Atmospheric pressure chemical ionization mass spectrometry for analysis of lipids

Abstract

Atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) has proven to be a very valuable technique for analysis of lipids from a variety of classes. This instrumental method readily produces useful ions with gentle fragmentation from large neutral molecules such as triacylglycerols and carotenoids, which are often difficult to analyze using other techniques. Molecules that are easily ionized, such as phospholipids, produce molecular ions and diagnostically useful fragment ions that are complementary to those produced by methods such as electrospray ionization MS with collision-induced dissociation. The simplicity and versatility of APCI-MS make it an ideal tool for use in solving hitherto very difficult analytical problems.

Surface analysis of lipids by mass spectrometry: More than just imaging

“…For example, analysis of cells treated with flusilazole resulted in detection of eburicol, suggesting inhibition of the C14-demethylase step. It is important to note that APCI mechanisms are generally more energetic than ESI or MALDI processes which can lead to greater in-source fragmentation of lipids (as evidenced in this study with the observation of de-methylated fragments) [237]. The high desorption temperatures may also result in thermal decomposition prior to ionization.…”

“…Such conditions induce desorption of surface-bound analytes by either direct thermal evaporation or sputtering processes, while ionization of desorbed molecules is typically initiated by mechanisms analogous to those described for APCI [237]. Accordingly, these techniques are best suited for thermally stable, low polarity compounds that are at least semi-volatile.…”

The renaissance of high-energy CID for structural elucidation of complex lipids: MALDI-TOF/RTOF-MS of alkali cationized triacylglycerols

“…ϩ -ions of triacylglycerols are predominantly produced under APCI conditions [8], exhibiting several drawbacks for tandem mass spectrometric analysis: (1) only triacylglycerol species containing at least one (from 1 to 6 or even more) double bonds show abundant [M ϩ H] ϩ -adduct ions of triacylglycerols are generated, which are easily formed upon addition of the ammonium ion from ammonium acetate present in nonaqueous solutions. From this type of precursor ions, only product ions free of the ammonium ion were formed by low-energy CID utilizing a triple quadrupole instrument [11].…”

“…R ecent advances in the analysis of complex triacylglycerol mixtures as well as detailed structural analysis thereof have been achieved by atmospheric pressure chemical ionization (APCI)- [1][2][3][4][5][6][7][8][9][10], electrospray ionization (ESI)- [11][12][13][14][15][16][17][18][19][20], fast atom bombardment (FAB)- [21][22][23][24][25][26], plasma desorption (PD) [27], and vacuum matrix-assisted laser desorption/ionization (vMALDI) mass spectrometry [28 -39] with and without prior chromatographic separation. Various types of mass spectrometric analyzers (single quadrupole, triple quadrupole, ion trap, sector, tandem sector, reflectron time-of-flight, and various hybrid instruments) were utilized for these analytes, enabling various tandem mass spectrometric experiments (tandemin-time, tandem-in-space) at different energy regimes for ion activation from low-energy (tens of eVs) to high-energy (up to 25 keV) collision-induced dissociation (CID) by selecting either [M ϩ H] ϩ -ions as well as [M ϩ NH 4 ] ϩ -or [M ϩ Na] ϩ -adduct ions as precursors ions.…”

Detection of the abundance of diacylglycerol and triacylglycerol molecular species in cells using neutral loss mass spectrometry

“…Much of our present understanding of the role of TAGs comes from measurement of either the total quantity of TAG present in cells, or fatty acids that can be released from TAGs after isolation and saponification rather than knowledge of changes in unique TAG molecular species. In recent years there has been renewed interest in the development of mass spectrometric methods using electrospray ionization and atmospheric pressure chemical ionization to analyze TAGs at the molecular species level [16][17][18][19]. We recently reported a strategy using MS 3 to analyze TAGs from a complex mixture as the NH 4 + adduct ions generated by electrospray ionization [20].…”