Agilent 7890b gas chromatography

Methoxyamine HCl, fatty acid methyl ester (C7–C30, FAMEs) standards, pyridine, and anhydrous sodium sulfate were obtained from Sigma-Aldrich (St. Louis, MO, USA). N-methyl-N(trimethylsilyl)trifluoroacetamide (MSTFA) with 1% (vol/vol) trimethylchlorosilane (TMCS), methanol (Optima LC-MS), acetonitrile (Optima LC-MS), dichloromethane, hexane, chloroform, and acetone were purchased from Thermo-Fisher Scientific (FairLawn, NJ, USA). Ultrapure water was produced by a Milli-Q reference system equipped with a LC-MS Pak filter (Millipore, Billerica, MA, USA). A time-of-flight mass spectrometry (GC-TOF/MS) system (Pegasus HT, Leco Corp., St. Joseph, MO, USA) was equipped with an Agilent 7890B gas chromatography and a Gerstel multipurpose sample MPS2 with dual heads (Gerstel, Muehlheim, Germany). Separation was achieved on a Rxi-5 ms capillary column (30 m × 250 μm i.d., 0.25 μm film thickness, Restek Corporation, Bellefonte, PA, USA). A Beckman Coulter AU5800 automatic biochemical analyzer (Brea, CA, USA) and a uric acid biochemical assay kit [DiaSys Diagnostic Systems (Shanghai) Co., Ltd., Shanghai, China] were used for serum uric acid detection.

In the present study, serum samples from 55 patients were subjected to a metabolomics analysis based on untargeted gas chromatography–time of flight mass spectroscopy (GC-TOF/MS). Overnight fasting venous blood samples were collected the next morning. The whole blood samples were then separated into a serum by centrifugation at 4°C. Then, 50 μl of the sample was mixed with 10 μl of the internal standard, and 175 μl of pre-chilled methanol/chloroform was added. After centrifugation at 14,000 g and 4°C for 20 min, 200 μl of the supernatant was transferred to an autosampler vial and subjected to GC-TOF/MS analysis. The untargeted metabolomics profiling was performed on the XploreMET platform (Metabo-Profile, Shanghai, China) and an untargeted GC-TOF/MS system with Agilent 7890B gas chromatography and a Gerstel multipurpose sample MPS2 (Gerstel, Muehlheim, Germany) were applied. For separation, an Rxi-5 ms capillary column (inner diameter: 30 m × 250 μm, film thickness: 0.25 μm; Restek Corporation, Bellefonte, PA, United States) was used. Helium at a constant flow rate of 1 ml/min was the carrier gas. The injection and transfer interfaces were at a temperature of 270°C, while the temperature for the source was at 220°C. The measurement was performed in the full scan model (m/z 50–500) at electron impact ionization (70 eV).

The GC-TOF/MS analysis was performed using a time-of-flight mass spectrometry (GC-TOF/MS) system (Pegasus HT, Leco Corp., St. Joseph, MO,USA),which consists of an Agilent 7890B gas chromatography and a Gerstel multipurpose sample MPS2 with dual heads (Gerstel, Muehlheim, Germany). As described previously [26 (link)], DB-5MS GC column (30 m × 250 μm i.d., 0.25-μm film thickness; Restek corporation, Bellefonte, PA, USA) was chosen for separation. Helium was used as the carrier gas at a steady flow rate of 1.0 mL/min. The temperature of transfer interface and injection were both 270 °C. The source temperature was set as 220 °C. The measurements were taken using electron impact ionization (70 eV) in the full scan mode (m/z 50–500).