Rapid Identification of Long-Chain Polyunsaturated Fatty Acids in a Marine Extract by HPLC-MS Using Data-Dependent Acquisition

Abstract

The collision-induced dissociation (CID) of a range of deprotonated fatty acid standards was studied using linear ion trap mass spectrometry. Neutral losses of 78, 98, and 136 Da were consistently observed for fatty acids with five or more double bonds. Comparison of the MS/MS spectra of docosahexaenoic acid (DHA) and universally (13)C-labeled DHA allowed the molecular formulas for these neutral losses to be determined as C(6)H(6), C(5)H(6)O(2), and C(8)H(8)O(2). Knowledge of fatty acid fragmentation processes was then applied to identify fatty acids from a sea anemone, Aiptasia pulchella, and dinoflagellate symbiont, Symbiodinium sp. extract. Using HPLC-MS, fatty acids were separated and analyzed by tandem mass spectrometry in data-dependent acquisition mode. Neutral loss chromatograms for 78, 98, and 136 Da allowed the identification of long-chain fatty acids with five or more double bonds. On the basis of precursor ion m/z ratios, chain length and degree of unsaturation for these fatty acids were determined. The application of this technique to an Aiptasia sp.-Symbiodinium sp. lipid extract enabled the identification of the unusual, long-chain fatty acids 24:6, 26:6, 26:7, 28:7, and 28:8 during a single 40 min HPLC-MS analysis.

Identification and Quantitation of Fatty Acid Double Bond Positional Isomers: A Shotgun Lipidomics Approach Using Charge-Switch Derivatization

“…Electrospray ionization (ESI) MS coupled with liquid chromatography (LC) has dramatically improved the analysis of FAs in comparison to traditional electron ionization GC-MS. 14–19 Typically, the LC/MS approaches target the carboxylate anions ionized in the negative-ion mode which limit not only the analytical sensitivity but also the unambiguous structural identification of FAs. This is largely due to the diminutive amounts of informative fragments generated particularly from polyunsaturated FA anions which readily lose CO 2 .…”

“…Recently, charge-remote fragmentation in mass spectrometry has facilitated the identification of FA double bond locations using high-energy collisional induced dissociation (CID) 20–22 and more recently using low-energy CID 19,23–25 of precursor ions ionized either in the negative-ion mode ( i.e. , as carboxylate anions 14,19 ) or in the positive-ion mode ( e.g. , as metal adduct ions 23,24 ).…”

Occurrence of Hexacosapolyenoic Acids 26:7(n‐3), 26:6(n‐3), 26:6(n‐6) and 26:5(n‐3) in Deep‐Sea Brittle Stars from Near the Kuril Islands

“…Very small amounts of 26:7(n-3) were detected in microalgae of the classes Cryptophyceae, Prymnesiophyceae and Dinophyceae [20] and in the lipids of the sea anemone-Symbiodinium association [10]. This acid was found and chemically characterized in roughscale sole flesh lipids, where its concentration was 0.69 % [3].…”

“…[7]. Only limited data are available pertaining to the presence of FA with 26 carbon atoms in marine animals [8][9][10][11][12][13]. In a comparative investigation of lipids in symbiotic and nonsymbiotic brittle stars, McKenzie et al [11] found a series of PUFA with 24 and 26 carbon atoms.…”

Electrospray Quadrupole Travelling Wave Ion Mobility Time-of-Flight Mass Spectrometry for the Detection of Plasma Metabolome Changes Caused by Xanthohumol in Obese Zucker (fa/fa) Rats

“…However, if metabolite identification is the goal of the analysis, the mass information needs to be complemented with structural data that can be obtained by performing collision-induced dissociation (CID). The most common acquisition mode in untargeted metabolomic experiments is the acquisition of full scan data and product ion data using data-dependent acquisition (DDA) modes [14,15]. DDA acquisitions are technically realized in hybrid tandem mass spectrometry instruments by combining multiple mass analyzer, such as the Q-ToF-type instruments, quadrupole orbitraps (Q Exactive), and combinations of linear trap quadrupole (LTQ) instruments with high resolution mass analyzer, e.g.…”