How to maintain and care for liquid chromatograph

    Reservoir: Cleanliness is the key to maintaining the normal use of the mobile phase reservoir. Use HPLC-grade solvents and reagents as much as possible. Mobile phases containing buffer salts and non-HPLC-grade mobile phases must be filtered through a 0.5μm filter to remove particulate matter. When changing mobile phases, cross contamination should be prevented. Old mobile phases and reagent bottles that have been used for a long time should be discarded regularly to prevent the growth of microorganisms and changes in components. The inner wall of the reservoir should be cleaned regularly, and the accessories inside should be replaced frequently.

　　Pump: The seal of the pump is the most easily worn part. Damage to the seal can cause many system failures. Some people recommend replacing the seal every three months. But this cannot be generalized. It depends on the material quality of the seal, the pressure used, maintenance, and the buffer. The following measures can extend the life of the seal:

　　1. Clean the buffer liquid in the pump every day to prevent salt deposition. The pump should be immersed in a solution without buffer or in an organic solvent.

　　2. Use HPLC grade reagents;

　　3 Use sintered stainless steel sinkers. Be careful to prevent excessive pressure from damaging the plunger rod or burning the motor due to pump blockage.

　　Injector: After shutdown, use solvent to rinse out the residual samples and buffer salts in the injector to prevent inorganic salt deposition and sample particles from causing wear or blockage of the valve rotor surface. It is strictly forbidden to use a sharp needle like that of a gas chromatograph for injection.

　　Chromatographic columns: There are several measures to prevent column performance degradation:

　　1. The chemical corrosion of the solvent cannot be too strong;

　　2. Prevent particles from settling at the column head;

　　3. A pressure limiter should be installed on the pump to prevent excessive pressure and large impact;

　　4 When the mobile phase pH is > 7, use a large particle size of the same filler as a pre-column;

    5. Add a sintered stainless steel filter to the column head and a guard column if necessary;

　　Detector : Keep the detector clean and flush it together with the chromatographic column after each use. It is recommended to use strong solvent to reverse flush the detection pool from time to time (disassemble the column). Use degassed mobile phase to prevent air bubbles from getting stuck in the pool. The detector lamp has a certain life span, so do not turn on the lamp when not in use.

　　Operation limit: Each pump has an upper pressure limit. When the system reaches the preset value, the pump will automatically stop, which can protect the column and other hardware. The upper pressure limit is set below 20MPa, and the pump gasket and injection valve are durable, but setting the upper pressure limit too low will extend the analysis time. It is advisable to set the upper pressure limit at 15-20MPa according to the test. The pressure of a new column is relatively low, and the pressure rises as the use time increases, so the set upper pressure limit should also change. In gradient elution, the pressure change caused by the change of mobile phase should be considered to avoid stopping the pump midway due to too low upper pressure limit. Systems with microcomputers also need to set the lower pressure limit, generally 0.5-1MPa, and the pump will stop automatically when the mobile phase in the reservoir is drained or leaks seriously. Sometimes the lower pressure limit is set to 0, which will also stop the pump automatically.