| MS Description
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Methanol, isopropanol, and acetonitrile of … Methanol, isopropanol, and acetonitrile of LC-MS grade were purchased from Wako. Ammonium acetate, formic acid, methyl tert-butyl ether (MTBE), and water were also purchased from Wako. 1,2-Didecanoyl-sn-glycero-3-phosphocholine used for the internal standard was purchased from Sigma-Aldrich.
<LC Method>
The LC system consisted of a Waters Acquity UPLC system. Lipids were separated on the mostly same condition as described in Method 3 except for using ammonium acetate instead of ammonium formate. The LC system consisted of a Waters Acquity UPLC system. Lipids were separated on an Acquity UPLC HSS T3 C18 column (50 x 1.0 mm; 1.8 µm) (Waters, Milford, MA, USA). The column was maintained at 55°C at a flow-rate of 0.15 mL/min. The mobile phases consisted of (A) 200:800:10:1 (v/v/v/v) acetonitrile:water:1 M ammonium acetate:formic acid and (B) 100:900:10:1 (v/v/v/v) acetonitrile:isopropanol:1 M ammonium acetate:formic acid. A sample volume of 1 µL was used for the injection. The separation was conducted under the following gradient: 0 min 35% (B); 3 min 70% (B); 7 min 85% (B); 10 min 90% (B); 12 min 90% (B); 12.5 min 35% (B); and 15 min 35% (B). Sample temperature was maintained at 10°C.
<MS Method>
Mass spectrometric detection of lipids was performed on a quadrupole/time-of-flight mass spectrometer Xevo G2 QTOF MS (Waters, Milford, MA, USA). MS2 analyses were performed at the sensitivity mode. Data dependent MS/MS acquisition (DDA) was used for MS2. The conditions for recording were as follows: source capillary, 3.0 (positive ion mode) and 2.5 kV (negative ion mode); sampling cone, 20 (positive) and 40 (negative); extraction cone, 4.0; source temperature, 120°C; desolvation temperature, 450°C; cone gas flow, 50 L/h; desolvation gas flow, 600 L/h; scan ranges, m/z 100-1600; MS1 scan time, 200 ms (centroid); MS2 scan time, 100 ms (centroid); collision energy, 20-50 eV (ramp mode). The other DDA parameters were event number, 6; scan repeat, 3; peak selection mode to trigger MS/MS, intensity-based detection; deisotope peak detection, yes; ionization mode, ESI; and correction by lock mass function, yes. and correction by lock mass function, yes.
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