Comparison of Atmospheric Pressure Chemical Ionization and Field Ionization Mass Spectrometry for the Analysis of Large Saturated Hydrocarbons

Abstract

Direct infusion atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was compared to field ionization mass spectrometry (FI-MS) for the determination of hydrocarbon class distributions in lubricant base oils. When positive ion mode APCI with oxygen as the ion source gas was employed to ionize saturated hydrocarbon model compounds (M) in hexane, only stable [M - H] ions were produced. Ion-molecule reaction studies performed in a linear quadrupole ion trap suggested that fragment ions of ionized hexane can ionize saturated hydrocarbons via hydride abstraction with minimal fragmentation. Hence, APCI-MS shows potential as an alternative of FI-MS in lubricant base oil analysis. Indeed, the APCI-MS method gave similar average molecular weights and hydrocarbon class distributions as FI-MS for three lubricant base oils. However, the reproducibility of APCI-MS method was found to be substantially better than for FI-MS. The paraffinic content determined using the APCI-MS and FI-MS methods for the base oils was similar. The average number of carbons in paraffinic chains followed the same increasing trend from low viscosity to high viscosity base oils for the two methods.

Uncatalyzed, Regioselective Oxidation of Saturated Hydrocarbons in an Ambient Corona Discharge

“…As already noted, the major ions typically produced from saturated hydrocarbons in APCI sources are hydride abstracted cations, [ M −H] + . Rapid, intramolecular 1,2‐hydride shifts should effectively mobilize this charge.…”

“…So resistant is this problem to solution by mass spectrometry that, in spite of modern atmospheric pressure ionization and electrospray methods, including specialized methods like reactions with metal ions, the decades‐old technique of field ionization is still favored by many for the determination of alkane molecular weight distributions . Nevertheless, low‐powered atmospheric pressure plasmas are of increasing interest as ionization sources in commercial mass spectrometers because they generate molecular weight diagnostic [ M −H] + ions . Herein, we demonstrate controlled addition of N and O to hydrocarbons using ion/molecule reactions.…”

Determination of volatile non intentionally added substances coming from a starch-based biopolymer intended for food contact by different gas chromatography-mass spectrometry approaches

“…Even though charge transfer and protonation are considered the prevalent ionization pathways in APGC, in this work potential new ionization processes that appeared to be dependent on the source environment were investigated. Generally, GC-APCI is well known to generate molecular weight diagnostic M + • and [M+H] + ions [35,36]. However, a few studies demonstrated that in ambient corona discharge, the addition of N and O to hydrocarbons via ion/molecule reactions is possible [37].…”

On-chip mass spectrometric analysis in non-polar solvents by liquid beam infrared matrix-assisted laser dispersion/ionization

“…To overcome this limited application range, ESI has been the subject of intensive research [27]. Approaches described in the literature include atmospheric pressure chemical ionization (APCI) [28][29][30][31], atmospheric pressure photoionization (APPI), solvent-assisted electrospray ionization (SAESI) [32][33][34][35], desorption electrospray ionization (DESI) [36][37][38], easy ambient spray ionization (EASI) [39][40][41][42][43], laser ablation electrospray ionization (LAESI) [44], and low-temperature plasma ionization (LTP) [45]. There are practically no literature reports on direct mass spectrometric on-chip analysis of compounds dissolved in water non-miscible, non-polar solvents.…”