The liquid chromatograph offers stable performance and high detection sensitivity, widely used in research, environmental protection, pharmaceuticals, food, chemicals, and other fields. Below is the standard operating procedure and core usage points.
Operation: Prepare mobile phase and pure methanol; filter through a 0.45 μm / 0.22 μm membrane; degas by sonication for 20 minutes.
Key points: Mobile phase must be filtered and degassed (to prevent column clogging, pump damage, baseline instability). Prepare aqueous buffer solutions fresh to prevent bacterial growth and deterioration.
Operation: Turn on the pump power; set pressure upper limit to 40 MPa (400 bar). First flush the pump with pure methanol at 1 mL/min for 10‑20 minutes, then switch to the mobile phase. Turn on the detector, set wavelength, and zero the baseline.
Key points: If the previous method used a buffer, always flush the flow path with methanol before starting the experiment (to prevent salt precipitation and pump damage). Do not arbitrarily raise the pressure limit.
Operation: Start the workstation, confirm communication, wait for baseline fluctuation < ±0.1 mV and low noise before injection.
Key points: Do not inject if the baseline is unstable (system not equilibrated, air bubbles, or contamination), otherwise retention time drift and inaccurate results may occur.
Operation: Draw sample with a microsyringe (3‑5 times the loop volume). Turn the injection valve to the “LOAD” position, inject the sample, then turn to the “INJECT” position to start data acquisition.
Key points: Inject quickly to prevent sample diffusion; wash the needle with solvent (methanol/isopropanol) at least 5 times before and after injection to prevent cross‑contamination.
Operation: Set quantitative parameters (external standard method – peak area – single‑point/multi‑point calibration). Prepare a component table (name, retention time, concentration). Select standard files to generate the curve, ensuring R² > 0.99 (ideally > 0.999).
Key points: Standard concentrations must be accurate and cover the expected sample concentration range. Periodically verify the curve; recalibrate if deviation occurs.
Operation: After injection, wait for all peaks to elute. Sequential injections can be performed.
Key points: Monitor pressure – a sudden increase may indicate a clogged column; a sudden drop or fluctuation may indicate a leak or air bubbles. Pause and troubleshoot if an anomaly occurs.
Operation: Enter the reprocessing module, open the data file, and click “Recalculate” to generate the report.
Operation:
Turn off the detector.
Flush the system according to the mobile phase type:
Aqueous / buffer mobile phase: First flush with 10% methanol/water for 30 minutes, then with pure methanol for 20 minutes.
Pure organic mobile phase: Flush directly with methanol; Stop the pump and turn off the power; Wash the injection valve.
Key points: Never leave buffer in the system overnight; this extends column and pump life.
