Frequently Asked Questions in Gas Chromatography Analysis Testing

First, the possible reasons for peak loss at the calibration and the troubleshooting methods that should be used 1. The syringe is faulty and verified with a new syringe. 2. The detector is not connected, or the detector does not work. Check the set value 3. The injection temperature is too low, check the temperature, and adjust as needed. 4. The oven temperature is too low, check the temperature, and adjust as needed. No-load airflow, check the pressure regulator, check the leak, verify the column feed rate 6. Column breakage, if the column break is at the column inlet end or the detector end, it can be remedied, cut off the column break, reinstall

Second, the leading edge peak 1. Column overload, reduce the injection volume 2. The two compounds co-elute, improve the sensitivity and reduce the injection volume, reduce the temperature by 10 to 20 degrees, so that the peaks are separated 3. The sample is condensed, check the injection Mouth and column temperature, if necessary, can be heated up 4. Sample decomposition, using a deactivated injector liner or lowering the injector temperature

3. Trailing peaks 1. The sampler bushing or column adsorbs the active sample: replace the bushing. If the problem cannot be solved, remove the inlet end of the column for 1~2 turns and re-install. 2. The column or the injector temperature is too low: raise the temperature (do not exceed the maximum temperature of the column). The temperature of the injector should be 25 degrees higher than the highest boiling point of the sample. 3. Co-elution of two compounds: increase the sensitivity, reduce the injection volume, and reduce the temperature by 10 to 20 degrees to separate the peaks. 4. Column damage: replace the column 5. Column contamination: Remove 1~2 turns from the inlet end of the column, and then re-install the capillary analysis to solve common problems.

Fourth, only the solvent peak 1. Syringe has a problem: use a new syringe to verify. 2. Incorrect carrier gas flow rate (too low): Check the flow rate and adjust if necessary. 3. The sample is too dilute: Inject a known sample to give good results. If the result is good, increase the sensitivity or increase the amount of injection. 4. The oven temperature is too high: check the temperature and adjust as needed. 5. The column cannot resolve the component from the solvent peak: replace the column with a thicker coating or a different polarity. 6. Carrier gas leak: check the leak ( Use soapy water) 7. The sample is absorbed by the column or the injector bushing: replace the bushing. If the problem cannot be solved, remove 1~2 turns from the inlet end of the column and reinstall it.

V. Wide solvent peak 1. Due to improper column installation, dead volume is generated at the inlet: reinstall the column. 2. Poor injection technology (injection is too slow): Adopt fast and steady injection technology. 3. The injector temperature is too low: increase the injector temperature. 4. Sample solvent and detection interact: replace the sample solvent. 5. Residual sample solvent in the column: Replace the sample solvent 6. Improper cleaning of the septum: adjustment or cleaning 7. Incorrect shunt ratio (incomplete shunt exhaust flow rate): Adjust the flow rate

6. False peaks 1. The column adsorbs the sample, then desorbs: replace the liner. If the problem cannot be solved, remove 1~2 turns from the column inlet end and reinstall. 2. Syringe contamination: Try it with a new syringe and a clean solvent. If the false peak disappears, rinse the syringe several times. 3. The sample size is too large: reduce the injection volume. 4. Poor injection technology (injection is too slow: using fast and smooth injection technology

7. Columns with good work in the past have unresolved peaks 1. The column temperature is wrong: check and adjust the temperature 2. Incorrect carrier gas flow rate: Check and adjust the flow rate. 3. The sample injection volume is too large: reduce the sample injection volume 4. The injection technology level is too bad (injection is too slow): Adopt rapid and steady injection technology. 5. Column and bushing contamination: Replace the bushing. If the problem cannot be solved, remove 1~2 turns from the inlet end of the column and reinstall it.

8. The baseline is irregular or unstable 1. Column loss or pollution: Replace the bushing. If the problem cannot be solved, remove 1~2 turns from the inlet end of the column and reinstall it. 2. Detector or injector contamination: cleaning detector and injector 3. Carrier gas leakage: Replace the septum and check for column leakage. 4. The carrier gas control is uncoordinated: check whether the source pressure is sufficient. If the pressure is ≤ 500 psi, please replace the cylinder. 5. The carrier gas has impurities or gas path pollution: replace the gas cylinder and clean the metal tube with a carrier gas purification device. 6. The carrier gas flow rate is not within the maximum/minimum limits of the instrument (including hydrogen and air for FID): The flow rate is measured and verified according to the technical specifications of the manual. 7. The detector is out of order: check the instrument manual. 8. Injector septum drain: age or replace the septum.