Liquid chromatographs (LC) are widely used in chemical, pharmaceutical, environmental, and food testing fields for separating and analyzing complex samples. As precision analytical equipment, LC systems are prone to various faults due to long-term operation, improper operation, or component wear, which affect test efficiency and result accuracy. This article summarizes the most common faults of liquid chromatographs, provides targeted maintenance and repair methods, and introduces daily upkeep measures, with a total length of about 1000 words, to help operators ensure the stable and reliable operation of the equipment.
The troubleshooting and maintenance of liquid chromatographs should follow the principle of "prevention first, timely handling, and standardized operation". Daily upkeep can effectively reduce the occurrence of faults, while accurate fault diagnosis and proper repair can quickly restore equipment performance, avoiding unnecessary losses.
1. Common Faults and Repair Methods of Liquid Chromatographs
Liquid chromatograph faults are mainly concentrated in the pump system, injection system, chromatographic column, and detector. The specific faults, causes, and repair methods are as follows:
1.1 Pump System Faults
The pump is the core of the LC system, responsible for delivering mobile phase stably. Common faults include unstable flow rate, no flow output, and abnormal noise. The main causes are: blockage of the check valve or pipeline, air bubbles in the mobile phase, worn pump seals, or inaccurate pressure settings. For unstable flow rate, check and clean the check valve, remove air bubbles by purging the pump, and replace worn seals. If there is no flow output, inspect the mobile phase level (ensure it is sufficient), check for pipeline blockage, and clean or replace the blocked parts. Abnormal noise is usually caused by dry friction of the pump or air bubbles, which can be solved by adding lubricating oil or purging air bubbles.
1.2 Injection System Faults
The injection system is responsible for accurately delivering samples into the chromatographic column. Common faults include inaccurate injection volume, sample leakage, and blocked injection needle. Inaccurate injection volume is often due to worn injection needle, loose seal, or incorrect parameter settings; replace the injection needle, tighten the seal, and reset the parameters. Sample leakage is mostly caused by aging or damaged injection port gasket; replace the gasket in time. If the injection needle is blocked, clean it with an appropriate solvent (such as methanol) or replace it with a new one.
1.3 Chromatographic Column Faults
The chromatographic column is the key for sample separation, and common faults include reduced column efficiency, peak tailing, and no peak. Reduced column efficiency is usually caused by column contamination or fixed phase loss; flush the column with a suitable solvent (such as methanol-water mixture) to remove contaminants, or replace the chromatographic column if the damage is severe. Peak tailing may result from improper mobile phase pH, contaminated column, or mismatched sample and column; adjust the mobile phase pH, clean the column, or select a suitable chromatographic column. No peak is often due to column blockage or incorrect mobile phase; flush the column or replace the mobile phase.
1.4 Detector Faults
Common detectors for LC include UV-Vis detector, fluorescence detector, and refractive index detector. Common faults include no signal, unstable baseline, and low sensitivity. For no signal, check the detector power supply, signal connection line, and light source (replace the light source if it is burned out). Unstable baseline may be caused by contaminated mobile phase, detector drift, or environmental interference; replace the mobile phase, calibrate the detector, and keep the equipment away from electromagnetic interference. Low sensitivity is often due to contaminated detector flow cell or worn light source; clean the flow cell or replace the light source.
2. Daily Maintenance and Upkeep Measures
Daily maintenance is crucial to extend the service life of liquid chromatographs and reduce faults. The key maintenance measures are as follows:
First, mobile phase maintenance: Use high-purity solvents and deionized water to prepare the mobile phase, filter it through a 0.22μm filter membrane to remove impurities, and degas it (ultrasonic degassing or online degassing) to avoid air bubbles. Replace the mobile phase regularly to prevent mold growth or solvent deterioration.
Second, pump maintenance: Flush the pump with methanol or acetonitrile after each use to remove residual mobile phase and avoid pipeline blockage. Check the pump seals and check valves regularly, and replace worn parts in time. Keep the pump clean and add lubricating oil to the moving parts regularly.
Third, chromatographic column maintenance: After use, flush the column with a suitable solvent to remove sample residues. Store the column in a suitable solvent (such as methanol for C18 columns) and avoid exposure to high temperature and humidity. Do not use strong acid, strong alkali, or high-concentration organic solvents for a long time to prevent damage to the fixed phase.
Fourth, detector maintenance: Clean the detector flow cell regularly with a suitable solvent to remove contaminants. Check the light source regularly and replace it when its intensity decreases. Keep the detector clean and avoid dust accumulation.
Fifth, overall equipment maintenance: Turn off the power and gas source after use, and clean the instrument surface. Conduct regular calibration of the instrument (flow rate, injection volume, detector sensitivity) to ensure test accuracy. Store the equipment in a clean, dry, and temperature-stable environment (15-30℃), avoiding direct sunlight and electromagnetic interference.
In conclusion, mastering the common faults and repair methods of liquid chromatographs, and adhering to standardized daily maintenance, are essential for ensuring the stable operation of the equipment and the accuracy of test results. Operators should conduct regular inspections and maintenance, and contact professional maintenance personnel in time for complex faults that cannot be solved independently, so as to maximize the service life of the equipment and improve work efficiency.
