A method of coupling the Paternò–Büchi reaction with direct infusion ESI-MS/MS for locating the CC bond in glycerophospholipids. Issue 12 (19th February 2016)

• Record Type: Journal Article
• Authors: Stinson, Craig A.; Xia, Yu
• Is Part Of: Analyst. Volume 141:Issue 12(2016)
• Page Start: 3696
• Page End: 3704
• Publication Date: 2016-02-19
• Subjects: Chemistry, Analytic -- Periodicals; 543
• DOI: 10.1039/c6an00015k
• Languages: English
• ISSNs: 0003-2654

Abstract

Abstract : Conducting the Paternò–Büchi reaction in a microflow photo-reactor enables its coupling with ESI-MS/MS and CC location determination for shotgun lipid analysis. Abstract : Tandem mass spectrometry (MS/MS) coupled with soft ionization is established as an essential platform for lipid analysis; however, determining high order structural information, such as the carbon–carbon double bond (CC) location, remains challenging. Recently, our group demonstrated a method for sensitive and confident lipid CC location determination by coupling online the Paternò–Büchi (PB) reaction with nanoelectrospray ionization (nanoESI) and MS/MS. Herein, we aimed to expand the scope of the PB reaction for lipid analysis by enabling the reaction with infusion ESI-MS/MS at much higher flow rates than demonstrated in the nanoESI setup (∼20 nL min −1 ). In the new design, the PB reaction was effected in a fused silica capillary solution transfer line, which also served as a microflow UV reactor, prior to ESI. This setup allowed PB reaction optimization and kinetics studies. Under optimized conditions, a maximum of 50% PB reaction yield could be achieved for a standard glycerophosphocholine (PC) within 6 s of UV exposure over a wide flow rate range (0.1–10 μL min −1 ). A solvent composition of 7 : 3 acetone : H2 O (with 1% acid or base modifier) allowed the highest PB yields and good lipid ionization, while lower yields were obtained with an addition of a variety of organic solvents. Radical induced lipid peroxidation was identified to induce undesirable side reactions, which could be effectively suppressed by eliminating trace oxygen in the solution via N2 purge. Finally, the utility of coupling the PB reaction with infusion ESI-MS/MS was demonstrated by analyzing a yeast polar lipid extract where CC bond locations were revealed for 35 glycerophospholipids (GPs).