Thread Content
Precautions for use and maintenance of gas chromatography and common problems, troubleshooting, troubleshooting, fault diagnosis methods and repairs 1. No peaks ⑴ Amplifier power is disconnected ⑵ Ion line is broken ⑶ No carrier gas flows ⑷ Bad contact of recorder ⑸ Recorder failure ⑹ Injection temperature is too low and the sample is not vaporized ⑺ Micro syringe is clogged ⑻ Silicone rubber leakage of injector ⑼ Chromatographic column connection is loosened ⑽ No fire (FID) ⑾FID centralized voltage is not connected or has poor contact ⑿Current (TCD) is not set ⑴ Check the amplifier and fuse ⑵ Check the ion line ⑶ Check the carrier gas flow path to see if it is blocked ⑷ Check the recorder connection ⑸ Read the instrument manual ⑹ Increase the injector temperature ⑺ Replace the syringe ⑻ Replace the silicone rubber ⑼ Tighten the chromatography column ⑽ Ignition ⑾ Connect the collecting voltage and exclude the collecting voltage Poor pressure connection phenomenon ⑿ First set the power supply 2. The sensitivity decreases due to normal residence time ⑴ The attenuation is too high ⑵ Insufficient injection volume ⑶ Loss during the sample injection process ⑷ The syringe is leaking or blocked ⑸ The carrier gas leakage, especially the injector leakage ⑹ Improper selection of hydrogen and air flow rate (FID) ⑺ The detector does not have high voltage ⑴ Reduce attenuation and increase high resistance ⑵ Increase the injection volume ⑶ Ensure that all samples enter the system as much as possible during the injection process ⑷ Replace the syringe ⑸ Leak detection ⑹ Adjust hydrogen and air flow ⑺ Check or install high voltage 3. Peak tailing ⑴ Injection temperature is too low ⑵ Injection tube contamination (sample or silicone rubber residue) ⑶ The furnace temperature of the chromatography column is too low ⑷ The injection technique is too low ⑸ The chromatography column is improperly selected (the sample reacts with the column support or fixative) ⑴Re-adjust the injector temperature ⑵Clean the injector tube with solvent ⑶Increase the chromatography column temperature ⑷Improve the injection technology to achieve fast needle insertion and fast needle withdrawal ⑸Re-select the appropriate chromatographic column 4. Tongue peak ⑴The column exceeds the negative charge, the sample amount is too large ⑵ The sample agglutinated in the system ⑴ Reduce the sample amount ⑵ Increase the column temperature first, and then select the appropriate injector, chromatographic column, and detector temperature 5. No peaks are separated ⑴ The column temperature is too high ⑵ The column is too short ⑶ Fixed Liquid loss ⑷ Improper selection of stationary solution or support ⑸ Carrier gas flow rate is too high ⑹ Injection technique is too poor ⑴ Reduce column temperature ⑵ Choose a longer column ⑶ Replace the chromatographic column or aging column ⑷ Select appropriate chromatographic column ⑸ Reduce load Air flow rate ⑹ Improve sampling technology 6. Round peak ⑴ Exceed the linear range of the detector ⑵ Recorder damping is too large ⑴ Reduce sample volume ⑵ Re-adjust recorder damping 7. Flat peak ⑴ Amplifier input saturated ionization detection ⑵ Changes in the zero point position of the recorder transmission device ⑴ Reduce the sample amount and reduce the sensitivity of the amplifier ⑵ Check the zero point position of the recorder, or compare it with other records 8. Zigzag baseline ⑴ Fatigue of the steady flow valve diaphragm ⑵ Changes in the output pressure of the carrier gas bottle pressure reducing valve ⑴ Replace the diaphragm or repair the valve ⑵ Adjust the pressure of the carrier gas bottle pressure reducing valve to another position 9. One-way change in the baseline without injecting sample (FID) ⑴ The detector temperature is too high Low ⑵ The column temperature stops or is out of control ⑴ Increase the detector temperature to more than 100℃, clean the detector or raise the detector temperature to 200℃ to drive away the water vapor ⑵ Repair the temperature control system and heating wire platinum resistor 10. The recording pen jitters when the peak reaches the fixed position. ⑴ The slide wire resistor of the recorder is contaminated. ⑴ Clean the slide wire resistor. 11. Baseline mutation. ⑴ Poor contact of the power plug. ⑵ External electric field interference. ⑶ Improper selection of hydrogen air flow rate (FID). ⑴ The power plug socket is installed securely ⑵ Eliminate external electric field interference that can affect the normal operation of the instrument ⑶ Re-adjust the air and hydrogen flow, especially the air flow 12. The baseline suddenly shifts Ground 13. Retention time increases sensitivity ⑴ The carrier gas flow rate is too slow ⑵ The carrier gas flow rate changes after the injection ⑶ The injector silicone rubber leaks ⑴ Increase the carrier gas flow rate. If there is obstruction in the carrier gas flow rate, try to eliminate it ⑵ Change the injection silicone rubber ⑶ Change the injection silicone rubber 14. Reverse peak ⑴ The sample enters another column ⑵ The positive and negative switch positions are placed in the wrong position ⑴ Sample The product enters the appropriate chromatography column ⑵ Change the positive and negative switch to the correct position 15. Irregular baseline fluctuations during constant temperature operation ⑴ The instrument is not placed in a good position ⑵ The instrument contact is not good ⑶ The column fixative is lost ⑷ The carrier gas leaks ⑸ The detector is contaminated ⑹ The carrier gas flow rate is improperly selected ⑺ The hydrogen air is improperly selected ⑻ The amplifier itself is unstable ⑼ The recorder is not good ⑴ Place the instrument in a place without strong vibration and strong air convection, and place the instrument horizontally. It is best to place the instrument on a cement platform or a table padded with rubber. ⑵ The instrument and recorder should be well grounded. ⑶ Improper selection of fixative, the column should be fully aged, and the column temperature cannot be raised to the limit of the use of the fixative (especially for high-sensitivity detectors). ⑷ Leak detection ⑸ Clean the detector ⑹ Adjust the carrier gas flow to ensure that the carrier gas flow is properly adjusted and ensure that the total pressure of the carrier gas bottle is between 50kg/cm2 - 150 kg/cm2 ⑺Adjust the hydrogen and air flow ⑻Check the amplifier and open the circuit to repair the amplifier ⑼Disconnect the recorder signal line and use a metal wire to short-circuit the signal line. If the recorder is not good, repair the recorder according to the recorder instructions 16. Extra peaks ⑴High component peak of the previous sample ⑵When the column temperature rises, condensation Moisture or other impurities in the chromatography column cause peaks in the chromatography column. ⑶ Air peak ⑷ Sample decomposition ⑸ Sample contamination ⑹ Sample reaction with fixative, carrier or adsorbent ⑺ Glass wool contamination at the head of the chromatographic column or syringe contamination ⑻ Injection silicone rubber contamination or lower than molecular components slip out ⑴ Wait until all the previous samples have slipped out Inject the sample ⑵ Install or prepare or regenerate the purifier, select appropriate operating conditions ⑶ Exclude the air in the syringe ⑷ Reduce the temperature of the injector (do not use easy catalytic and easy-to-separate stationary fluid or carrier) ⑸ Ensure that the sample is clean and free of impurities mixed with other components ⑹ Use other chromatography columns to avoid interference between the sample and the stationary phase Reactions ⑺ Replace the column head with glass wool or clean the syringe ⑻ Bake the silicone rubber at 200°C for 16 hours before use 17. The peak occurs when the recording pen suddenly returns below the baseline and extinguishes the fire (FID) ⑴ The sample volume is too large ⑵ or the air flow is too low ⑶ The carrier gas flow rate is too high ⑷ The flame nozzle is contaminated (or blocked) ⑸ Use up the hydrogen gas ⑴ Reduce the sample volume ⑵ Readjust the hydrogen gas and air flow rate ⑶ Select the appropriate carrier gas flow rate ⑷ Clean the flame nozzle (or pass the flame nozzle) ⑸ Ensure there is enough hydrogen in the hydrogen source. 18. The step peak does not return to zero (peak flat head) and the recording pen will move left and right manually. ⑴ The gain and damping adjustment of the recorder are not appropriate. ⑵ The instrument is not properly grounded. ⑶ There is extremely low AC signal feedback to the recorder. ⑴ Correct the recorder gain anti-damping (until the manual recording pen moves left and right and it still returns to the original position) ⑵ The instrument and recorder need to be well grounded ⑶ Connect a 0.25uf/250v capacitor from the positive or negative input terminal to the ground terminal as needed. The positive or negative connection method is determined according to the test 19. The baseline does not return to zero ⑴ The zero point adjustment position of the recorder is abnormal ⑵ Due to excessive loss of column (FID) ⑶Detector contamination ⑷Recorder ⑴Use metal wire to short-circuit the recorder signal input and calibrate it to zero ⑵Use chromatographic peaks with less loss ⑶Clean the detector ⑷Repair the recorder according to the recorder instructions 20. There are burr peaks at irregular distances ⑴Dust particles or foreign substances burn irregularly in the flame (FID) ⑵ Insulator leakage or high-resistance connection switch is damp and leaking ⑶ Amplifier failure ⑴ Ensure that no glass wool molecules and particles enter the detector. The molecular sieve filter must be activated before use and cooled with N2 air flow or vacuum pump. ⑵ Clean insulators or high-resistance switches, etc. Dry after cleaning, and do not touch this part with your hands. ⑶ Repair the amplifier 21. There are certain short burr peaks at equal intervals. ⑴ Water condenses in the hydrogen pipeline. ⑵ Air leakage. ⑶ Blockage in the flow path. ⑷ Flame jump. ⑴ Eliminate the water well from the pipeline. Replace or activate the desiccant in the hydrogen filter. ⑵ Leak detection ⑶ Impurities are eliminated in the flow path. If there are impurities in the chromatographic column, the column temperature can be appropriately increased ⑷ Adjust the appropriate flow rate of hydrogen and air 22. Large baseline noise ⑴ Chromatographic column contamination or too large column loss ⑵ Carrier gas contamination ⑶ Carrier gas flow rate is too high ⑷ Carrier gas leakage ⑸ Poor grounding ⑹ High resistance pollution ⑺ Recorder slide wire pollution ⑻ Bad recorder ⑼ Injector pollution ⑽ Hydrogen flow rate too high or too low ⑾ Air flow rate too high or too low ⑿ Air or hydrogen pollution ⒀ Water condensation in FID ⒁ Poor contact of detector cable ⒂ Detector insulation transformer (ionization detector) ⒃Contamination of the detector electrode or nozzle and bottom ⒄TCD operating current setting is too large ⑴Replace the chromatographic column ⑵Replace or regenerate the carrier gas filter ⑶Re-adjust the carrier gas flow rate ⑷Leak detection ⑸Ensure the instrument is well grounded ⑹Find the contaminated high resistance and clean it ⑺Wipe clean Contaminants on the wire resistor ⑻ Short-circuit the signal input end of the recorder. If there is still noise at the signal input end of the recorder, repair the recorder ⑼ Clean the injection tube in the injector and remove the silicone rubber residue ⑽ Readjust the hydrogen flow rate ⑾ Readjust the air flow rate ⑿ Replace the air, hydrogen filter ⒀ Increase F ID temperature, eliminate moisture ⒁Replace or repair the cable ⒂Clean the detector insulator ⒃Clean the detector ⒄Reduce the operating current setting value to an appropriate value 23, periodic baseline fluctuations ⑴Poor detector temperature control ⑵Poor column furnace temperature control ⑶Carrier gas flow Poor flow adjustment ⑷ The pressure of the carrier gas bottle is too low ⑸ Improper adjustment of air and hydrogen ⑴ Check the platinum resistance, adjust the temperature control sensitivity, and improve the control accuracy ⑵ Check the platinum resistance, the temperature control should improve the control accuracy ⑶ Readjust the carrier gas flow rate ⑷ Replace the carrier gas bottle ⑸ Readjust Air, hydrogen flow 24. One-way baseline drift ⑴ The detector temperature increases or decreases by a large degree ⑵ The zero point drift of the amplifier ⑶ The column temperature increases or decreases by a large degree ⑷ The carrier gas is gradually used up ⑴ Stable detector temperature. If the temperature changes after starting up, it is normal. Common phenomena ⑵ Check the amplifier ⑶ Stabilize the column temperature. If the temperature changes after starting up, it is a normal phenomenon ⑷ Replace the carrier gas bottle 25. The baseline changes after the program temperature rise ⑴ When the temperature rises, the column loss increases ⑵ The column loss is not corrected ⑶ The column is contaminated ⑷ Two The amount of fixative solution for each column is different. ⑴ Select an appropriate chromatographic column or aged column. ⑵ Correct the column loss. ⑶ Replace the column. ⑷ The coating weight of the fixative solution for the two columns should be equal. 26. Irregular baseline changes when the temperature rises. ⑴ Excessive column loss. ⑵ Not choosing the right one. ⑶ Column contamination ⑷ Ghost peaks appear when the silicone rubber heats up ⑴ Select an appropriate chromatographic column, and the column temperature should be lower than the maximum temperature of the fixative ⑵ Choose appropriate operating conditions ⑶ Replace the chromatographic column ⑷ Bake the silicone rubber at 200°C for 16 hours before use