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One of the routine maintenance methods of HPLC: abnormal pressure
Changes in operating pressure are often signs of failure. Find the observed phenomenon from the table below and refer to the corresponding solution in the list on the right.
A. No pressure display, no mobile phase flow
Cause solution
1. Power problem 1. Turn on the power and turn on
2. The fuse is burnt out 2. Replace the fuse
3. The controller is set incorrectly or fails to be set 3. a. Take appropriate settings b. Repair or replace the controller
4. The plunger rod is broken 4. Replace the plunger rod
5. There is air in the pump head 5. Degas the solvent and start the pump to extract air
6. Insufficient mobile phase 6, a, supplement mobile phase b, replace inlet filter head
7. The check valve is damaged. 7. Replace the check valve.
8. Leakage 8. Tighten or replace the finger-tight joint
B. The mobile phase flows normally, but there is no pressure display
Cause solution
1. The instrument is damaged 1. Replace the instrument
2. The pressure sensor is damaged 2. Replace the pressure sensor
C, the pressure continues to be high
Cause solution
1. The flow rate setting is too high 1. Adjust the flow rate setting
2. The sieve plate in front of the column is blocked. 2. a. Backwash the chromatographic column b, replace the sieve plate c, and replace the chromatographic column if allowed
3. Improper use of mobile phase or crystallization of buffer salts. 3. a. Use appropriate mobile phase b. Flush the column.
4. Improper choice of chromatographic column 4. Choose appropriate chromatographic column
5. The injection valve is damaged 5. Clean or replace the injection valve
6. The column temperature is too low 6. Increase the temperature
7. The controller is abnormal 7. Repair or replace the controller
8. The protection column is blocked 8. Cleaning or replacing the protection column
9. The online filter is blocked 9. Clean or replace the online filter
D, the pressure continues to be low
Cause solution
1. The flow rate is set too low 1. Adjust the flow rate
2. System leakage 2. Determine the location of leakage and repair
3. Improper chromatographic column selection 3. Choose the appropriate chromatographic column
4. The column temperature is too high 4. Reduce the temperature
5. The controller is abnormal 5. Repair or replace the controller
E. The pressure is rising
Cause solution
1. See list C 1. See list C
F. The pressure drop is zero
Cause solution
1. See list A, B 1. See list A, B
G. The pressure keeps decreasing, but it does not return to zero
Cause solution
1. See list D 1. See list D
H. Pressure fluctuation
Cause solution
1. There is gas in the pump 1, a, solvent degassing
b. Remove gas from the pump
2. The check valve is damaged 2. Replace the check valve
3. Damaged pump seal 3. Replace the pump seal
4. Insufficient degassing 4. a. Solvent degassing
b. Change the degassing method (using online degassing method, etc.)
5. System leakage 5. Determine the location of leakage and repair
6. Gradient elution 6. Pressure fluctuations due to changes in mobile phase viscosity
HPLC routine maintenance method 2: liquid leakage
The leakage problem can usually be solved by tightening or replacing the pipe joint. But it is worth noting that excessive tightening can cause leakage of metal joints and wear of plastic joints. If the problem of liquid leakage cannot be solved by tightening the connector slightly, the connector must be removed and inspected for damage (eg, damaged ferrules, impurities on the sealing surface); damaged connectors should be replaced.
A. Liquid leakage at the joint
Cause solution
1. Loose joints 1. Tighten
2. The connector is worn 2. Replace
3. The connector is overtightened 3. a. Loosen it and tighten it again
b. Replace
4. The connector is contaminated 4. a. Remove and clean
b. Replace
5. Parts do not match 5. Use accessories of the same brand
B. Pump leakage
Cause solution
1. The check valve is loose 1. a. Tighten the check valve (no over tightening is necessary)
b. Replace the check valve
2. Loose joints 2. Tighten the joints (do not overtighten)
3. The mixer seal is damaged 3. a. Replace the mixer seal
b. Replace the mixer
4. The pump seal is damaged 4. Repair or replace the pump seal
5. The pressure sensor is damaged 5. Repair or replace the pressure sensor
6. The pulse damper is damaged. 6. Replace the pulse damper.
7. The proportional valve is damaged. 7. a. Check the diaphragm and replace it immediately if there is leakage
b. Check the finger-tight joints and replace immediately if damaged
8. Damage of vent valve 8. a. Tighten vent valve
b. Replace the vent valve
C. Leakage of injection valve
Cause solution
1. Damaged rotor seal 1. Reinstall or replace the injection valve
2. The metering ring is blocked 2. The metering ring is replaced
3. The inlet seal is loose 3. Adjust
4. The size of the injection needle is not suitable 4. Use the appropriate injection needle
5. Siphon is generated in the waste liquid pipe 5. Keep the waste liquid pipe above the liquid level of the waste liquid
6. The waste liquid pipe is blocked. 6. Replace or dredge the waste liquid pipe.
D. Chromatographic column leakage
Cause solution
1. Loose end joint 1. Tighten the joint
2. There is filler in the ferrule 2. Remove, clean the ferrule and reinstall
3. The thickness of the sieve plate is not suitable 3. Use a suitable sieve plate (refer to the table below)
Sieve plate selection guide
Material particle size sieve aperture
3-4u 0.5u
5-20u 2u
E. Detector leakage
Cause solution
1. Damage to the flow cell gasket 1. a. Avoid excessive background pressure (pressure drop)
b. Replace the gasket
2. Broken flow cell window 2. Replace the window
3. Leakage of the hand tight joint 3. Tighten or replace
4. The waste liquid pipe is blocked 4. Replace the waste liquid pipe
5. The flow cell is blocked 5. Reinstall or replace
HPLC routine maintenance method three: various problems of spectrum
Many problems of the liquid chromatography system can be reflected in the spectrum. Some of these problems can be solved by changing the device parameters; other problems must be solved by modifying the operating procedures. The correct choice of column and mobile phase is the key to a good chromatogram.
A, peak tailing
Cause solution
1. The sieve plate is blocked 1. a. Backflushing the chromatographic column
b. Replace the imported sieve plate
c. Replace the chromatographic column
2. Collapsed chromatographic column 2. Packed chromatographic column
3. Interference peak 3, a, use a longer column
b. Change the mobile phase or replace the chromatographic column
4. Misselected PH of mobile phase 4. Adjust PH value. For basic compounds, low pH is more conducive to obtaining symmetrical peaks
5. The reaction between the sample and the melting point on the surface of the filler. Figure 5. a. Add ion pair reagent or alkaline volatile modification
Related downloads
HPLC daily maintenance methods.doc
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