Capillary supercritical fluid chromatography-atmospheric pressure chemical ionization mass spectrometry of triacylglycerols in berry oils

A capillary supercritical fluid chromatograph (SFC), combined with a triple-quadrupole mass spectrometer (MS) via a liquid chromatography-atmospheric pressure chemical ionization (LC-APCI) interface, was utilized in the analysis of berry oil triacylglycerols. No modification of the commercially available interface was required. Vapor of different solvents, such as methanol, isopropanol, water, or ammonium hydroxide in methanol, was introduced in the sheath gas flow in the APCI source to achieve adequate ionization of triacylglycerols. The separation of triacylglycerols according to acyl carbon number and degree of unsaturation was accomplished on a 20 m × 50 μm i.d. SB-Cyanopropyl-25 column. The resolution of triacylglycerols in the reconstructed ion chromatogram and the sensitivity of the SFC-(APCI)MS system was comparable to or slightly better than that obtained with a flame ionization detector. No baseline drifting was observed during the SFC density programming. Triacylglycerols formed diagnostic [M + H]⁺ and [M - RCOO]⁺ ions with all tested reactant ion solvents except with ammonium hydroxide in methanol, which formed abundant [M + 18]⁺ ions instead of [M + H]⁺ ions. The abundance of the [M + H]⁺ ion increased with increasing degree of unsaturation of a triacylglycerol, whereas the abundance of the [M - RCOO]⁺ ion depended on the regiospecific distribution of the fatty acid moiety between the sn-1/3 positions and the sn-2 position and on the number of double bonds.