J w db 5ms ultra inert

50 mg of liver sample was added to 150 μl of physiological saline for homogenate. Then 500 μl methanol were added, followed by 1 min of vortex mixing and 10 min of standing at -20 ℃ for protein precipitation. After centrifugation at 12000 g for 10 min at 4 ℃, 300 μl of the supernatant was transferred to an autosampler vial and blown to dryness with nitrogen. The residue was dissolved in 80 μl of methoxyamine (15 mg/ml) and the methoximation reaction was carried out for 90 min of shaking at 30 ℃, then 50 μl of BSTFA containing 1% TMCS was added for another 1 h of thimethylsilylation at 70℃. At last, a 1 μl of aliquot of the solution was injected into an Agilent 6890 GC system coupled with 5975B mass spectrometer (Agilent technologies, USA) for analysis.
Chromatographic separation was carried out on a capillary column (Agilent J&W DB-5ms Ultra Inert, 30 m * 0.25 mm * 0.25 μm) using programmed temperature showed in Table 1. Parameters in mass spectrometer were as follows: scan range, m/z 30–550; temperature of injection, interface and source, 280 ℃, 260 ℃ and 230 ℃.

The GC–MS column was Agilent J&W DB-5ms Ultra Inert (30 m × 0.25 mm × 0.25 μm). GC parameters: high-purity helium (purity: 99.9996%) was the carrier gas, the injection port temperature was 260°C with splitless injection and 1.0 µL injection volume, and the flow rate was 1.0 ml/min. The initial temperature was 80°C and lasted for 2 min. The temperature was raised to 180°C at a rate of 10°C/min, then to 240°C at 5°C/min, and finally to 290°C at 25°C/min and kept for 9 min. MS parameters: ion source temperature was 230°C, quadrupole temperature was 150°C, and mass spectrometer interface temperature was 280°C. Solvent delay was 5 min, ionization mode was EI, electron impact ionization voltage was 70 eV, and scan range (m/z) was 30–550. The parallel injection sequence method was used.