Cortecs uhplc c 18 column

The LC-MS analysis of tea samples was based on the previous methods (9 (link)). The column was CORTECS UHPLC C18 Column (2.1 mm × 100 mm, 1.6 μm), Waters, USA. The mobile phase consisted of 0.1% aqueous formic acid (A) and 0.1% acetonitrile (B); the gradient elution was as follows: 0–2 min, 7% B; 2–3 min, 7–12% B; 3–8 min, 12–18% B; 8–12 min, 18–60% B; 12–13 min, 60–100% B; and 13–14 min, 100% B. Samples (2 μl) were eluted at 0.3 ml/min and the column oven was kept at 36°C. Mass spectrometry conditions were as follows: electrospray ion source (ESI), negative ion detection mode acquisition, and scanning range of m/z 100–1,700. ESI source parameters were as follows: dry gas (N₂) flow rate of 5 ml/min, dry gas temperature of 300°C, atomization gas pressure of 35 psig, capillary voltage of 3,500 V, nozzle voltage of 1,000 V, capillary outlet voltage of 400 V, and collision energy of 20 eV. The data processing software was the Agilent Profinder software (B.08.00, Agilent, USA) and Mass Profiler Professional (MPP) software (version 14.9, Agilent); processing included noise filtering, molecular feature extraction (MFE), peak alignment, and normalization.