As a precision analytical instrument, the stability and lifespan of gas chromatography directly depend on the quality of daily maintenance. A scientific maintenance system should cover three aspects: key component maintenance, environmental management, and standardized operation. The following is a systematic maintenance plan:
1、 Special maintenance of core modules
1. Fine tuned management of injection system
-Replacement of spacer: After each injection, observe whether there are cracks or carbonization marks on the lower edge of the spacer. It is recommended to replace it immediately every 50 injections or when there is a pungent burnt smell to prevent peak distortion caused by air leakage.
-Cleaning of diversion plate: Disassemble the diversion plate every month, clean the quartz wool and metal sieve plate with acetone ultrasonic cleaning, remove accumulated high boiling residue, and avoid inaccurate diversion ratio.
-Lining maintenance: Regularly inspect the sediment on the inner wall of the glass lining tube. If scaling is found, replace the lining tube with a new one. If necessary, fill it with deactivated glass wool to filter out particulate impurities.
2. Performance guarantee of detector
-FID flame optimization: adjust the ratio of hydrogen/air/nitrogen to the best state (typical value is 30:400:30) after starting up every day, and observe that the flame is blue and there is no explosion sound. Dismantle and collect polar plates weekly, and clean the carbon deposits at the nozzle with methanol.
-TCD hot wire protection: The heating program must be turned off before shutdown, and the bridge current can only be cut off after the furnace temperature drops to room temperature to prevent oxidation damage to the hot wire.
-ECD radioactive source protection: It is strictly prohibited to dismantle the detector without authorization. Every year, professional personnel shall test the sealing of the ⁶ Ni radioactive source and record the fluctuation range of the background current value.
3. Maintenance of chromatographic column efficiency
-Aging regeneration: After installing the new column, heat it up to 20 ℃ below the maximum operating temperature according to the program, and age it for 8 hours with a low flow rate of carrier gas. When the performance of the old column decreases, the separation efficiency can be restored by cutting the front end 10-20cm.
-Pre column screen management: Check the O-ring and screen blockage in front of the column every month, replace the stainless steel filter when pollution is severe, and avoid a sudden drop in column efficiency.
2、 Synchronous maintenance of auxiliary system
1. Purification of pneumatic system
-Replace the carrier gas cylinder immediately when the pressure is below 1MPa to prevent backflow and contamination of the pipeline. Replace the molecular sieve and activated carbon two-stage filters every quarter, and regenerate the color changing silica gel indicator when it turns pink.
-Drain the residual gas after the pressure reducing valve before use to avoid oil contamination from being sucked back into the chromatography column.
2. Calibration of temperature control system
-Perform monthly temperature calibration of the column temperature chamber, and compare the set value with the actual value using a standard thermometer to ensure a deviation of<± 1 ℃. The fan filter removes dust every quarter to ensure heat dissipation efficiency.
3. Circuit system protection
-Keep the circuit board dry and activate the dehumidification function when the humidity exceeds the standard. The data interface cable should avoid frequent bending, as poor contact can increase baseline noise.
3、 Standardized operating procedures
1. Startup preheating system
-After starting up, first blow the system with carrier gas for 15 minutes, and then start each heating zone to achieve thermal equilibrium of the detector. Immediately turn off the hydrogen gas when FID ignition fails, investigate the leak point, and then try again.
2. Sample pre-treatment requirements
-The liquid sample needs to be filtered through a 0.22 μ m filter membrane, and the pressure time of the sample bottle should be kept consistent during headspace injection. Solid sample derivatization reaction requiresAll overTo avoid contamination of the chromatographic column by non-volatile substances.
3. Shutdown protection program
-After the analysis is completed, continue to supply the carrier gas for 30 minutes and turn off the machine when the column temperature drops below 80 ℃. When not in use for a long time, disconnect the power supply and seal the ends of the chromatography column with plugs for storage.
4、 Maintain file establishment
-Develop electronic maintenance logs to record the batch number of consumables replaced, repair items, and instrument abnormalities. Keep the recent blank operating spectrum as a reference for quick diagnosis of system faults.
Through the multi-dimensional maintenance system mentioned above, the occurrence rate of baseline drift, ghost peak interference and other problems can be effectively reduced, and the service life of the instrument can be extended. It is recommended to develop an annual preventive maintenance plan based on the instrument manufacturer's manual to ensure the accuracy and reproducibility of analysis results.