High-resolution triacylglycerol mixture analysis using high-temperature gas chromatography / mass spectrometry with a polarizable stationary phase, negative ion chemical ionization, and mass-resolved chromatography

Abstract

High-temperature gas chromatography/mass spectrometry (HT-GC/MS) has been employed to study the behavior of mixtures of triacylglycerol molecular species on a polarizable stationary phase (immobilized 65% phenyl methyl silicone). The use of negative ion chemical ionization (NICI) at an ion source block temperature of 300 °C overcomes problems with interpretation of electron ionization (EI) mass spectra produced during the HT-GC/MS. The NICI spectra of triacylglycerols produced under these conditions contain abundant [RCO2](-), [RCO2 - 18](-), and [RCO2 - 19](-) ions, believed to be produced by nucleophilic gas-phase ammonolysis, that are used to identify the individual fatty acid moieties associated with peaks in triacylglycerol total ion chromatograms. The polarizable stationary phase produces significantly enhanced resolution of triacylglycerol molecular species compared to hightemperature stable apolar stationary phases, such as immobilized dimethyl polysiloxanes. The resolution of complex natural mixtures of triacylglycerols can be further improved by use of the Biller-Biemann enhancement technique to produce mass-resolved chromatograms. Investigation of the mass-resolved chromatograms provides important information with regard to the factors that affect elution orders of individual triacylglycerol molecular species. The analysis of mixtures of authentic triacylglycerols by HT-GC/MS via NICI provides data that relate to the analytical limits of the technique for the analysis of triacylglycerols that bear both saturated and polyunsaturated fatty acyl moieties.

Rapid Quantification of Low‐Viscosity Acetyl‐Triacylglycerols Using Electrospray Ionization Mass Spectrometry

“…Other methods capable of separating and quantifying intact TAG molecular species have also been developed. For example, high temperature-gas chromatography coupled with mass spectrometry (HT-GC/MS) has long been utilized for this purpose [27]. Recently, this approach has also been used with high sensitivity to quantify the products of in vitro enzyme reactions [28].…”

“…In addition, the high temperatures used in HT-GC are of concern when analyzing thermally unstable compounds. Thus concerns about the recovery and detection of highly polyunsaturated molecular species have been noted [27, 29, 30]. ESI-MS based quantification therefore represents a useful tool with which to understand the production of acetyl-TAG in transgenic plants, as well as to better study the substrate specificity of unusual acetyltransferases such as Ea DAcT.…”

Structural elucidation of co‐eluted triglycerides in the marine diatom model organism Thalassiosira pseudonana by ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry

“…[7] These methods are time-consuming and cannot confirm the acyl position in TAGs. [8,9] Mass spectrometry using a variety of ionization techniques has been applied for the characterization of TAGs, including electron impact, [10] chemical ionization, [11,12] field desorption, [13,14] desorption chemical ionization, [15] fast atom bombardment (FAB), [16,17] thermospray, [18] electrospray ionization (ESI), [19] and atmospheric pressure chemical ionization (APCI). [20] Recently, although structural characterization of regiospecific TAGs by ESI 3 in vegetable oils has been reported, a multilevel MS analysis for completing regiospecific TAGs is still desired.…”

A Comprehensive Study on Triacylglycerols in Tobacco Leaves Using Liquid Chromatography and Atmospheric- Pressure Chemical-Ionization Mass Spectrometry

“…In more recent years, several approaches have been presented to determine the structures and compositions. Gas chromatography (GC) incorporating a high-temperature-tolerable capillary column coupled with a flame ionization detector (FID) or mass spectrometer (MS) has generally been accepted as a useful combination for analysis (8)(9)(10). Moreover, liquid chromatography (LC) using an octadecylsilane (ODS) column coupled with various detectors has become more popular for separating and identifying triacylglycerols.…”