As a commonly used analytical instrument in fields such as biology, pharmaceuticals, food, and chemicals, the correct use and daily maintenance of a liquid chromatography directly affect the accuracy of test results and the instrument's service life. To help users operate and maintain the equipment more effectively, we have compiled twelve key points for daily use of liquid chromatography for your reference.
1. If the instrument will not be used for an extended period, it is recommended to remove the chromatographic column and seal it with plugs. Avoid storing columns in pure water; organic solvents are recommended to prevent microbial growth.
2. After each sample analysis, promptly clean the injector with a solvent that dissolves the sample to prevent residue accumulation.
3. Mobile phases must be HPLC grade and should be filtered before use to remove particulate matter and other impurities.
4. After filtration, the mobile phase should be degassed by sonication and allowed to return to room temperature before use.
5. Avoid using pure acetonitrile as the mobile phase, as it may cause the check valve to stick and prevent the pump from drawing liquid properly.
6. After each use of a buffer or salt‑containing mobile phase, flush the column with a 10 % methanol/water solution for 30 minutes to ensure complete removal of ionic residues, then flush with pure methanol for another 30 minutes. Do not flush with pure water, as this may cause the packing to collapse and damage the column. Before next‑day use, equilibrate with the same water‑methanol ratio for 20 minutes.
7. C18 columns should not be used for samples containing proteins, blood, or other biological specimens, as this may reduce column efficiency or cause blockage.
8. If the system becomes blocked and pressure rises too high, check and clean the pre‑column, the in‑line filter in the mixer, the tubing filter, and the check valve in that order. Common cleaning methods include flushing with isopropanol, sonication in isopropanol, or cleaning with 10 % dilute nitric acid.
9. Bubbles in the mobile phase can cause pressure fluctuations and poor result reproducibility. Efforts should be made to avoid bubble formation during operation.
10. When the inlet tube cannot draw liquid normally, manual suction with a syringe may be used. A mobile phase purge step is usually required before starting delivery.
11. Pay attention to the pH range marked on the column. Never inject strongly acidic or strongly basic samples, especially basic samples, as they may damage the stationary phase.
12. When changing the mobile phase, it is recommended to first place the suction filter in a beaker and rinse it while vibrating, before transferring it to the new mobile phase. For replacement of immiscible mobile phases, isopropanol should be used as a transition solvent to ensure a smooth system changeover.
