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Analysis of Common Malfunctions in Liquid Chromatography: A Comprehensive Guide from Repair to Daily Maintenance
Date: 2025-07-15Read: 5
In the precision instruments of the laboratory, liquid chromatography is like a rigorous "analyst", shouldering the important mission of compound separation and detection. However, this' precision expert 'may also experience malfunctions due to various factors, affecting experimental efficiency and data accuracy. This article will systematically review common faults in liquid chromatography, provide practical repair solutions, and summarize daily maintenance points to help you keep the instrument in the best condition at all times.
Abnormal pressure: liquid chromatography "blood pressure" alarm
Pressure is the core indicator of liquid chromatography operation, just like the blood pressure in the human body, whether it is too high or too low, it indicates potential problems.
High voltage alarms are often associated with flow path blockages. When the system pressure suddenly surges, it can be checked step by step according to the flow path sequence: first disconnect the inlet of the chromatographic column. If the pressure drops, it indicates that the blockage point is in the chromatographic column or subsequent pipeline; If the pressure is still high, check the check valve, injector, and pump head. During maintenance, for slightly blocked pipelines, a 5% nitric acid solution can be used to flush them; The one-way valve is contaminated and needs to be disassembled for ultrasonic cleaning. If the valve core is worn, it needs to be replaced.
Low pressure alarms are often caused by leaks or solvent depletion. First, observe if there are any liquid droplets at the joint. Loose joints need to be tightened again, and worn sealing rings need to be replaced in a timely manner; If the liquid level in the solvent bottle is too low, bubbles should be expelled after replenishing the solvent to prevent air from entering the pump chamber and forming an air lock.
Baseline anomaly: the 'invisible killer' of data accuracy
The stability of the baseline directly affects the detection results, and common baseline issues include drift, noise, and ghosting.
Baseline drift may be caused by fluctuations in column temperature, changes in flow matching ratio, or detector contamination. Ensure that the temperature of the column temperature chamber is stable within ± 0.1 ℃; When mixing mobile phases, an online mixing method is used to reduce manual mixing errors; If the detector flow pool is contaminated, a methanol water mixture can be used for reverse flushing, and stubborn pollutants can be soaked in dilute nitric acid solution.
Baseline noise is usually related to excessive pump pulses, insufficient detector light energy, or bubbles in the pipeline. Check if the damper of the pump is malfunctioning and replace it if necessary; Regularly monitor the usage duration of detector lights and replace them in advance when approaching their lifespan; Bubbles in the system need to be removed through sufficient degassing (such as vacuum degassing, ultrasonic degassing) and purge exhaust operations.
Ghost peaks are often caused by sample contamination, mobile phase impurities, or residual samples in the injector. Clean containers should be used for sample processing, and chromatographic grade reagents should be used for the mobile phase, which should be filtered through a 0.22 μ m membrane; Rinse the injection needle with mobile phase before injection, and clean the injection valve after the experiment.
Retention time drift: the 'unstable factor' of separation effect
The repeatability of retention time is the key to liquid chromatography analysis, and the drift problem is mainly related to changes in the pH value of the mobile phase, aging of the chromatographic column, or unstable flow rate.
Fluctuations in the pH value of the mobile phase can significantly affect the retention behavior of ionic compounds. Buffer solutions should be used to control the pH value, and the concentration of buffer salts should not be too low (usually not less than 5mmol/L); After long-term use, the stationary phase of the chromatographic column is lost. The column efficiency can be determined by testing the retention time of the standard sample. If the column efficiency decreases significantly, a new column needs to be replaced; If the flow rate is unstable, it is necessary to check the sealing ring and one-way valve of the pump, replace worn parts in a timely manner, and ensure smooth ventilation of the solvent bottle to avoid negative pressure affecting the flow rate.
Daily maintenance: the 'key password' to extend the lifespan of instruments
Prevention is better than repair, and scientific daily maintenance can significantly reduce the occurrence of malfunctions. After the daily experiment, rinse the system with pure solvent (methanol for the reverse phase column and n-hexane for the normal phase column) to avoid blocking the pipeline with buffer salt crystallization; Check the sealing of each joint weekly, clean the detector window and sample tray; Replace the rotor seal ring of the sampler every month, calibrate the column temperature box and detector wavelength; Maintain the pump quarterly, including replacing sealing rings, cleaning check valves, and inspecting pressure sensors.
In addition, it is crucial to keep records of instrument usage, including detailed records of each maintenance time, replaced parts, and troubleshooting situation, in order to trace the root cause of problems. At the same time, regular performance validation of the instrument is conducted, such as testing pressure fluctuations, baseline noise, and retention time repeatability, to ensure that the instrument is in a qualified state.
The efficient operation of liquid chromatography relies not only on accurate diagnosis and timely handling of faults, but also on standardized daily operation and maintenance.Mastering these troubleshooting and maintenance skills can enable you to handle various problems calmly in experiments, ensuring that precision instruments always provide reliable data support for scientific research.
