Gas chromatography instruments, as the core equipment in the field of component analysis, are widely used in industries such as chemical engineering, environmental protection, food, and medicine. The stability of its operation directly determines the accuracy of the detection data, and fault self inspection and standardized maintenance are the key to ensuring the efficient operation of the equipment. This article combines practical application experience to sort out the self checking logic, core maintenance methods, and prevention points of common faults in gas chromatographs, providing practical reference for laboratory technicians.
Fault self inspection should follow the principle of "from simple to complex, from outside to inside", prioritize troubleshooting easy to operate and low-risk links, and then delve into core component testing. Startup failure is the most basic and common problem, manifested as no response or startup failure of the instrument after connecting the power supply. At this point, the power supply system should be checked first: confirm that the power cord plug is in good contact, whether the socket voltage meets the rated requirements of the instrument (usually 220V ± 10%), and whether the fuse is blown. If the power supply is normal but still cannot be turned on, check the power module of the instrument again and observe whether the power indicator light is on. If there is no display, it may be that the power module is burnt out. After cutting off the power, contact a professional to replace it.
The failure of the carrier gas system directly affects the separation efficiency and is a key step in self inspection. Common issues include abnormal carrier gas pressure, leakage, and unstable flow rate. When the pressure is abnormal, first check the pressure of the gas cylinder. If the pressure of the gas cylinder is too low (less than 0.5MPa), it should be replaced in a timely manner; If the pressure of the gas cylinder is normal and there is no change in the gauge after adjusting the pressure reducing valve, it may be due to a malfunction of the pressure reducing valve or blockage of the gas path. When detecting leaks, the soap film method can be used: apply soapy water to the gas path joint. If bubbles appear, it is judged as a leak point. Focus on checking the loose parts such as the injection port nut, chromatographic column interface, detector joint, etc. Replace the aging sealing gasket or re tighten it to solve the problem. Unstable flow is often caused by solenoid valve failure or blockage of air path impurities. Flow fluctuations can be observed through a flow meter. If the fluctuation exceeds 5%, the air path filter needs to be disassembled and cleaned, and the solenoid valve needs to be replaced if necessary.
The main manifestations of sample injection system failures are no peak, abnormal peak shape, or retention time drift after injection. When there is no peak, first check if the injection needle is blocked: suck the injection needle into the solvent and push it out, observe if it is smooth, and if it is blocked, use a dedicated needle opener to clear it. If the injection needle is normal, check if the temperature at the injection port has reached the set value (usually above 50 ℃ above the boiling point of the sample) and if the vaporization chamber is contaminated. Injection port contamination is the main cause of abnormal peak shape, manifested as peak tailing and splitting. At this time, it is necessary to remove the injection port liner, observe for oil stains or residual samples, soak in acetone for ultrasonic cleaning, dry and install, and replace the injection port gasket (it is recommended to replace it every 50 injections). Retention time drift is often caused by chromatographic column problems. It is necessary to check whether the chromatographic column is installed properly and whether the temperature of the column temperature box is stable. If the chromatographic column ages, it needs to be aged (run at a temperature 20 ℃ higher than the operating temperature but 2-4 hours lower than the tolerance temperature).
Detector failure is the key factor affecting detection sensitivity, and different types of detector failures exhibit different symptoms. Taking the hydrogen flame ionization detector (FID) used as an example. If FID does not respond, first check whether the flow ratio of hydrogen, air, and tail gas is normal (usually 1:10:1), and whether ignition is successful. If ignition fails, the detector temperature can be raised to above 150 ℃ to eliminate water vapor interference and reignite; If the ignition still cannot be started, check if the ignition coil is open circuited and measure the resistance value with a multimeter. If it is infinite, the coil needs to be replaced. When the sensitivity of the detector decreases, first clean the collection electrode: clean it with methanol ultrasonic cleaning and air dry it, then check if the detector nozzle is blocked, unclog it with a fine steel wire, and reinstall it. Usually, the sensitivity can be restored.
The malfunction of the data processing system is manifested as no peak, abnormal peak area, or inability to save data. Firstly, check the connection line between the chromatography workstation and the instrument, confirm that the USB or serial port connection is normal, and restart the workstation software; If there is still no data, check if the detector output signal is normal, measure the signal value with an oscilloscope, and troubleshoot the detector. When the peak area is abnormal, first calibrate the injection volume to ensure that the injection needle accuracy meets the requirements, and then check whether the integration parameter settings are reasonable. Adjusting parameters such as slope sensitivity and peak width can improve the integration effect. The inability to save data is mostly due to workstation software failure or insufficient computer hard disk space. It is necessary to clean up hard disk space, reinstall software or update versions.
Fault repair should be based on standardized operation, with the core principles of "power-off operation, precise positioning, and professional replacement". When repairing circuit components such as power modules and ignition coils, the main power supply must be cut off first to avoid electric shock accidents; When replacing components such as chromatography columns and liners, gloves should be worn to prevent contamination, and installation should be strictly carried out according to the instructions in the instrument manual to ensure good sealing. For precision components such as detectors and solenoid valves, it is recommended that they be repaired by the manufacturer's engineer to avoid secondary damage caused by self disassembly.
Prevention is better than repair, and daily maintenance can significantly reduce the occurrence rate of failures. Establish an equipment maintenance ledger to record each usage time, sample type, fault situation, and repair content; Regularly replace vulnerable parts such as injection port gaskets, liners, chromatography column sieve plates, etc; Perform weekly leak detection on the gas system, clean the detector and injection system monthly, and calibrate the column temperature chamber and injection port quarterly. In addition, keeping the laboratory environment clean, controlling temperature (20-25 ℃) and humidity (40% -60%), avoiding dust and corrosive gas interference, can effectively extend the service life of the instrument.
The self inspection and maintenance of gas chromatography instruments require a combination of theoretical knowledge and practical experience, accurate identification of the fault point through systematic troubleshooting, and the use of standardized methods for maintenance. Meanwhile, establishing a comprehensive daily maintenance system can reduce the occurrence of faults from the source. Technicians need to be familiar with the structure and working principle of the instrument, accumulate experience in fault handling, ensure that the instrument is always in good operating condition, and provide reliable guarantees for accurate detection.