Troubleshooting guide for using capillary columns

1. Peak loss

1. Defective syringe verification 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

5. No carrier gas flow, check the pressure regulator, and check for leaks to verify the column feed rate

6. Column break, if the column break is at the inlet end of the column or the end of the detector, it can be remedied, cut off the broken part of the column, and reinstall

2. Frontier Peak

1. Column overload, reduce injection volume

2. The two compounds co-elute, improve sensitivity and reduce the injection volume, reduce the temperature by 10-20 degrees to separate the peaks

3. The sample is condensed, check the inlet and column temperature, and raise the temperature if necessary

4. Sample decomposition, use inactivated injector liner or lower the injector temperature

3. Trailing peak

1. The sampler bushing or column absorbs the active sample and replaces the bushing. If the problem cannot be solved, remove the inlet end of the column by 1 ~ 2 turns and then reinstall

2. The temperature of the column or sampler is too low, and it will heat up (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. The two compounds co-elute to increase the sensitivity, reduce the injection volume, and reduce the temperature by 10-20 degrees to separate the peaks

4. The column is damaged, replace the column

5. Column contamination, remove 1 ~ 2 circles from the inlet end of the column, and then reinstall

4. Only solvent peak

1. There is something wrong with the syringe, verify with a new syringe

2. Incorrect carrier gas flow rate (too low), check the flow rate and adjust it if necessary

3. The sample is too thin, inject a known sample to get a good result. If the result is good, increase the sensitivity or increase the injection volume.

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 (with soapy water)

7. The sample is absorbed by the column or injector bushing, replace the bushing. If the problem cannot be solved, remove 1 ~ 2 turns from the inlet end of the column and reinstall

5. Broad solvent peak

1. Due to improper installation of the column, dead volume is generated at the inlet, reinstall the column.

2. Poor sampling technology (injecting too slowly), using fast and stable sampling technology.

3. The temperature of the injector is too low. Increase the temperature of the injector.

4. The sample solvent and detection affect each other, and replace the sample solvent.

5. Residual sample solvent in the column, replace the sample solvent

6. Improper cleaning of septum, adjustment or cleaning

7. The split ratio is incorrect (the flow rate of the split exhaust is insufficient), adjust the flow rate

Six, false peak

1. The column adsorbs the sample, then desorbs, and replaces the liner. If the problem cannot be solved, remove 1 to 2 turns from the column inlet and reinstall.

2. The syringe is contaminated. Try it with a new syringe and a clean solvent. If the false peak disappears, flush the syringe several times.

3. The sample volume is too large. To reduce the injection volume, use a capillary chromatography column or a gas chromatography column.

4. Poor sampling technology (injecting too slowly), using fast and stable sampling technology

7. Unresolved peaks appear in columns that worked well in the past

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, reducing the sample injection volume

4. The level of sampling technology is too poor (injection is too slow), using fast and stable sampling technology.

5. The column and bushing are contaminated. Replace the capillary column bushing. If the GC column does not solve the problem, remove 1 to 2 turns from the inlet end of the column and reinstall

8. Irregular or unstable baseline

1. Column loss or pollution, replace the bushing. If the problem cannot be solved, remove 1 to 2 turns from the inlet end of the column and reinstall.

2. The detector or sampler is contaminated, clean the detector and sampler

3. Carrier gas leakage, replace the septum, check column leakage.

4. Carrier gas control is not coordinated. Check whether the pressure of the carrier source is sufficient. Please replace the gas cylinder.

5. Carrier gas is contaminated by impurities or gas path, replace the gas cylinder, and use the carrier gas purification device to clean the metal tube.

6. The carrier gas flow rate is not within the maximum / minimum limits of the instrument (including hydrogen and air for FID). Measure the flow rate and verify it according to the technical specifications of the user manual.

7. If there is something wrong with the detector, refer to the instrument manual for inspection.

8. The septum of the capillary column injector is lost, aging or replace the septum

Nine, the retention time of the same column varies

1. The column temperature is too low or too high, check and adjust the column temperature.

2. The flow rate of the carrier gas is too low or too high. Use the appropriate at the outlet of the column to measure the flow rate through the calibration gas source.

3. The sampler septum or column leaks, if necessary, please check and repair.

4. The column is contaminated or damaged, re-age or replace the column

5. Sample overload, reduce sample injection volume

6. Check the workstation if something is wrong with the workstation

7. Carrier gas control is not coordinated, check the carrier gas source to see if the pressure is sufficient. Please replace the gas cylinder.

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