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Gas chromatography-mass spectrometry technology has developed rapidly and is now widely used in various fields, becoming one of the most effective methods for analyzing complex mixtures. During the use of instruments, various types of faults often occur, affecting the proper progress of analysis and testing tasks. Therefore, how to quickly and accurately determine the cause of these faults and resolve them promptly is a problem that instrument operators frequently face and urgently need to address. This post combines practical operation procedures, maintenance experience, and insights to summarize and outline the common fault phenomena, possible causes of these faults, and troubleshooting methods for gas chromatography-mass spectrometry instruments, providing a reference for instrument operators. Technical library: yunrun.com.cn/tech/ 1. Fault phenomenon: When the tuning parameters are changed, the change in the intensity of the tuning peak occurs with a delay. Possible causes of the fault and methods to resolve them: ① The ion source is contaminated; the solution is to clean the ion source using methanol and propanol via ultrasonic cleaning for 15 minutes each ； ②The pre-quadrupole is contaminated; the solution is to ultrasonically clean the pre-quadrupole sequentially with methanol and propanol for 15 minutes each ； ③The ion source component is not installed properly, and the circuit is not connected. The solution is to remove the ion source and reinstall it. 2. Fault symptoms: When tuning the mass spectrometer, excessively high ion energy and repulsion voltage are required. Possible causes of the fault and methods to resolve them: ① Excessively high ion energy is caused by contamination of the ion source, while an excessively high repulsion voltage is due to contamination of the pre-quadrupole and quadrupole. The solution is to ultrasonically clean the ion source, pre-quadrupole, and quadrupole sequentially using methanol and propane for 15 minutes each, as well as to carry out routine maintenance ； ②The mass spectrometer is not tuned to its optimal condition; the solution is to retune it. 3. Fault phenomenon: When the tuning parameters are changed, the instrument does not respond significantly. Possible causes of the fault and methods to resolve them: The ion source is short-circuited or the circuit is not connected properly. The solution is to remove the ion source and use a multimeter to check whether the electrical connections between various components are normal. 4. Fault phenomenon: The shape of the tuned peak is poor, with spikes present. Possible causes of the fault and methods to resolve them: ① The mass spectrometer is not tuned to its optimal state; the solution is to retune the mass spectrometer ； ②The ion source is contaminated; the solution is to ultrasonically clean it sequentially with methanol and propanol for 15 minutes each ； ③The analyzer is defective or damaged; the solution is to check whether there are any defects or damages on its appearance. 5. Fault phenomenon: No reference peak appears during tuning. Possible causes of the fault and methods to resolve them: ① There is no reference sample in the perfluorobutylamine container used as a reference standard; the solution is to add perfluorobutylamine as a reference standard into the reference sample container built into the mass spectrometer ； ②The pipeline of the reference sample is blocked; the solution is to remove the pipeline and clean it using acetone and ultrasonic waves ； ③In the case of air leakage, the solution is to check the height of the air peak at m/z 28; if it is greater than 10% of the height of the helium peak at m/z 4, it indicates an air leak. Propane can be injected at each connection point, and by observing the changes in the intensity of the propane molecular ion peak at m/z 58, the exact location of the leak can be determined. 6. Fault phenomenon: Irregular and rough tuning peaks appear. Possible causes of the fault and methods to resolve them: ① The ion source is contaminated; the solution is to ultrasonically clean the ion source with methanol and propanol for 15 minutes each in sequence ； ②The filament is aged; the solution is to replace it ； ③The mass spectrometer is not tuned to its optimal condition; the solution is to retune it. 7. Fault phenomenon: The peaks at m/z 18, 28, and 32 are greater than 10% of the peak at m/z 4 for helium. Possible causes of this fault and methods to resolve it: ① Air leakage; the solution is to perform a leak detection test and check the connections of the column ； ②The helium is running low, and impurities have accumulated in the gas cylinder; the solution is to replace the carrier gas cylinder and install a degassing device ； ③The newly cleaned ion source has not been dried; the solution is to set the ion source temperature to 250°C to dry it ； ④The column is contaminated; the solution is to age the column. 8. Fault phenomenon: No ions are generated when the filament is in good condition. Possible causes of the fault and solutions: ① The ion source needs to be recalibrated; the solution is to use a calibration tool to recalibrate the ion source ； ②There is severe air leakage; the solution is to detect leaks and tighten all connections. 9. Fault phenomenon: When tuning the mass spectrometer, the high-mass peaks at m/z 502 and 614 do not appear. Possible causes of the fault and methods to resolve it: Short circuit in the pre-quadrupole; the solution is to remove the pre-quadrupole and dry it using helium or nitrogen. 10. Fault phenomenon: The mass scale of the mass spectrometer cannot be calibrated. Possible causes of the fault and methods to resolve them: ① The mass spectrometer is not tuned to its optimal state; the solution is to retune the mass spectrometer ； ②If the ion source temperature is too high or too low, the solution is to set the ion source temperature between 180 and 220℃ ； ③Air leakage: The method for detection is to check the height of the air peak at m/z 28. If this value exceeds 10% of the height of the helium peak at m/z 4, it indicates the presence of air leakage. Propanone should then be applied to each connection point using a syringe; by observing changes in the intensity of the molecular ion peak at m/z 58, the exact location of the leak can be determined ； ④The energy of the emitted electrons is not appropriate; the solution is to set the energy of the emitted electrons to 70 eV. 11. Fault symptom: Low sensitivity. Possible causes of the fault and troubleshooting methods: ① The mass spectrometer is not tuned to its optimal state; the solution is to retune the mass spectrometer ； ②The calibration of the mass scale in the mass spectrometer is inaccurate; the solution is to recalibrate the mass scale of the mass spectrometer ； ③The ion source is contaminated; the solution is to ultrasonically clean it sequentially with methanol and propanol for 15 minutes each ； ④If the ion source temperature is too high or too low, it can cause the sample to decompose or get adsorbed inside the ion source; the solution is to adjust the ion source temperature ； ⑤The depth to which the column extends into the ion source is not appropriate; the solution is to adjust the depth of the column’s insertion into the ion source ； ⑥The split injector and valve are faulty; the solution is to check the injector and valve ； ⑦The column efficiency has decreased; the solution is to replace the column ； ⑧The injector is contaminated; the solution is to ultrasonically clean the liner with methanol or propane for 15 minutes each, or replace the liner. ⑨ The detector voltage is too low; the solution is that the detector voltage should be between 350 and 450 V. ⑩ There is an air leak; the solution is to check the height of the air peak at m/z 28 – if it is greater than 10% of the height of the helium peak at m/z 4, there is an air leak. Use a syringe to apply propane to each connection point, and by observing the changes in the intensity of the propane molecular ion peak at m/z 58, determine the exact location of the leak. 12. Fault phenomenon: No noise in the density gradient chart (it appears as a straight line). Possible causes of the fault and solutions: The detector voltage is too low; the solution is to increase the detector voltage. 13. Fault symptom: Excessive noise. Possible causes of the fault and solutions: ① The ion source is contaminated; the solution is to ultrasonically clean the ion source with methanol and propanol successively for 15 minutes each ； ②The power supply system generates spurious peaks; the solution is to install a power conditioning device. 14. Fault phenomenon: Flat peak appears. Possible causes of the fault and methods to resolve it: ① The sample in the column is overloaded; the solution is to use split injection or dilute the sample ； ②The detector is overloaded; the solution is to reduce the detector voltage. 15. Fault phenomenon: Unstable retention time. Possible causes of the fault and methods to resolve them: ① Degradation of the stationary phase in the capillary column; the solution is to cut off 0.5 m from the end of the capillary column or replace it ； ②The injector is leaking; the solution is to improve its sealing ； ③The carrier gas pipeline is leaking; the solution is to detect the leak and tighten it. 16. Fault symptoms: Low sensitivity to high-boiling-point compounds and poor peak shape. Possible causes of the fault and solutions: ① The ion source temperature is too low, resulting in sample adsorption; the solution is to increase the ion source temperature ； ②The temperature of the gas chromatography interface is too low; the solution is to increase the temperature of this interface to match the final temperature of the heating program ； ③The final temperature of the gas chromatography heating program is too low; the solution is to increase the final temperature of this program. 17. Fault phenomenon: Peak tailing. Possible causes of the fault and methods to resolve it: ① The temperature of the injector is too low; the solution is to increase the temperature of the injector ； ②The temperature of the gas chromatography interface is too low; the solution is to increase the temperature of the gas chromatography interface ； ③The carrier gas flow rate is too low; the solution is to increase it ； ④The linings and columns are contaminated; the remediation method involves ultrasonically cleaning the linings sequentially with methanol and propanol for 15 minutes each, followed by aging the columns. 18. Fault phenomenon: Skewed peaks or distorted peaks appear. Possible causes of the fault and methods to resolve them: ① The scanning speed is too low, resulting in insufficient number of scans for each chromatographic peak. The solution is to increase the scanning speed so that each chromatographic peak is scanned at least 6 times ； ②The chromatographic peak is too narrow; the solution is to change the chromatography conditions ； ③The mass spectrometer is not tuned to its optimal condition; the solution is to retune it ； 19. Fault phenomenon: Incorrect isotope ratio. Possible causes of the fault and methods to resolve them: ① The mass scale of the mass spectrometer is not calibrated accurately; the solution is to recalibrate the mass scale of the mass spectrometer ； ②The proportions of the various mass peaks after tuning the mass spectrometer are incorrect; the solution is to tune the mass spectrometer again ； ③For air leaks, the solution is to check the height of the air peak at m/z 28; if it is greater than 10% of the height of the helium peak at m/z 4, it indicates an air leak. Propylene is injected at each connection point, and by observing the changes in the intensity of the propylene molecular ion peak at m/z 58, the exact location of the leak can be determined. 20. Fault phenomenon: The peak of the separated signal is too weak. Possible causes of the fault and methods to resolve it: ① The temperature and current of the ion source are too high (exceeding the pyrolysis temperature and ionization current); the solution is to adjust the temperature and current of the ion source ； ②The chemical ionization pressure is either too high or too low (for chemical ionization sources); the solution is to adjust the chemical ionization pressure. 21. Fault phenomenon: Loss of isotope peaks in the mass spectrum. Possible causes of the fault and methods to resolve them: ① The mass scale of the mass spectrometer is not calibrated accurately; the solution is to recalibrate the mass scale of the mass spectrometer ； ②The mass spectrometer tuning has not reached an optimal state; the solution is to retune the mass spectrometer ； ③The ion source is contaminated; the solution is to ultrasonically clean it sequentially with methanol and propanol for 15 minutes each ； ④The detector voltage is too low; the solution is to increase the detector voltage ； e. Detector failure; the solution is to check the sensitivity of the detector. 22. Fault phenomenon: Poor reproducibility of the mass spectrum. Possible causes of the fault and methods to resolve them: ① The ion source is contaminated; the solution is to ultrasonically clean the ion source with methanol and propanol for 15 minutes each in sequence ； ②The ion source heater is unstable; the solution is to replace the ion source heater ； ③The filament is damaged; the solution is to replace it ； ④The mass spectrometer tuning has not reached an optimal state; the solution is to retune the mass spectrometer ； ⑤The calibration of the mass scale in the mass spectrometer is inaccurate; the solution is to recalibrate the mass scale of the mass spectrometer ； ⑥In the case of air leakage, the solution is to check the height of the air peak at m/z 28; if it is greater than 10% of the height of the helium peak at m/z 4, it indicates an air leak. Propylene can be injected at each connection point, and by observing the changes in the intensity of the propylene molecular ion peak at m/z 58, the exact location of the leak can be determined. 23. Fault phenomenon: Large interference peaks appear in the total ion current chromatogram. Possible causes of the fault and methods to resolve them: ① Air leakage. The method to detect this is to check the height of the air peak at m/z 28; if it is greater than 10% of the height of the helium peak at m/z 4, there is an air leak. Use a syringe to inject propane at each connection point, and by observing the changes in the intensity of the propane molecular ion peak at m/z 58, the exact location of the leak can be determined ； ②There is an issue with the quality of the carrier gas; the solution is to replace it ； ③The sample is contaminated; the solution is to improve the sample pretreatment method. 24. Fault phenomenon: The total ion current chromatogram gradually increases. Possible causes of the fault and methods to resolve them: ① Loss of the stationary phase in the column (characteristic peaks at m/z 207, 281); the solution is to age the column or replace it ； ②In the case of air leakage, the solution is to check the height of the air peak at m/z 28; if it is greater than 10% of the height of the helium peak at m/z 4, it indicates an air leak. Propylene can be injected at each connection point, and by observing the changes in the intensity of the propylene molecular ion peak at m/z 58, the exact location of the leak can be determined. 25. Fault phenomenon: The total ion current chromatogram declines slowly. Possible causes of the fault and methods to resolve them: ① The purge valve is closed; the solution is to open the purge valve ； ②The purge flow rate is too low; the solution is to increase it. 26. Fault symptom: Chromatographic peaks are too wide. Possible causes of the fault and methods to resolve them: ① The temperature of the injector is too low; the solution is to increase the temperature of the injector ； ②The sample in the column is overloaded; the solution is to use split injection ； ③The temperature increase in gas chromatography is too slow; the solution is to change the temperature programming of the gas chromatograph.