Gas Chromatography Troubleshooting Guide |
No Peaks:
| Possible Cause: | Solution: |
|---|---|
| Plugged syringe | Clean the syringe or inject sample with a new syringe. |
| No carrier gas | Immediately lower the column oven temperature to 35°C. Verify the carrier gas flow rate. Check for leaks at column connection and septum. Pressure at gas source should exceed pressure needed at head of column by at least 15 psi at maximum temperature. |
| Detector not on or gases improperly set | Check detector and gas settings. If using FID, make sure that the flame is lit. |
| Sample injected into the wrong injector | Reinject sample into the proper injector. |
| Column installed into the wrong detector | Reinstall the column into the proper detector. |
| Column broken | If broken at the inlet or the detector end, make clean cut and reinstall column. Repair mid column break by using a connector. Replace column. |
| Injection port temperature too low | Verify temperature is adequate to vaporize sample. |
| Oven not heated or column temperature too low | Verify temperature. |
Noise:
| Possible Cause: | Solution: |
|---|---|
| Contaminated injector | Clean the injector |
| Detector contaminated | Clean detector |
| Column is installed into the flame of the FID | Verify proper installation length and reinstall column. |
| Air leak, applicable to an ECD or TCD | Repair leak. |
| Incorrect combustion gases or flow rates | Check and reset gases to their proper values |
| Carrier gas leak at septum or column connection | Check for leaks. Replace septum or tighten connections if necessary |
Rounded or Flat Topped Peaks:
| Possible Cause: | Solution: |
|---|---|
| Detector overloaded | Decrease sample size |
| Exceeding the range of the integrator | Reset the attenuation levels |
Baseline Drift:
| Possible Cause: | Solution: |
|---|---|
| GC or column contamination | Clean the injector. Use guard column to prolong column life. |
| Incomplete conditioning of column | Condition the column until a stable baseline is achieved. |
| Unequilibrated detector | Allow the detector sufficient time to equilibrate. |
| Septum bleed | Use higher temperature septum or analyze sample at lower injector temperature. |
Peaks Reduced in Size:
| Possible Cause: | Solution: |
|---|---|
| Partially plugged syringe | Clean the syringe or use a new syringe. |
| Split ratio too high | Lower the split ratio. |
| Too short of a purge activation time for splitless injection | Increase the purge activation time. |
| Very high septum purge flow | Decrease the septum purge flow. |
| Injection port temperature too low | Increase the injector temperature. Make sure temperature is appropriate for high molecular weight or low volatility compounds. |
| Initial temperature of the column is too high for splitless or on-column injections | Decrease the initial column temperature or use a higher boiling solvent. |
| Impurities in the detector gas | Use impurity traps or replace the gas. |
| Sample components absorbed by column or inlet liner | Replace with new deactivated liner or replace glass wool/packing. |
Split Peaks:
| Possible Cause: | Solution: |
|---|---|
| Detector overloaded | Decrease sample size. |
| Poor injection technique | Change injection technique or inject using an autosampler. |
| Poorly installed column in the injector | Recut the column and reinstall into the injector. |
| Column temperature fluctuations | Check the oven temperature. |
| Co elution of two or more compounds | Contamination or change in the sample. Changes in the operational parameters. |
| Mixed sample solvent for splitless injection | Use a single solvent for sample injections. |
Ghost and Extra Peaks:
| Possible Cause: | Solution: |
|---|---|
| Previous run terminated too soon | Use a higher temperature to elute all of the sample components. Let analysis run longer before |
| Dirty syringe | Inject pure solvent, using a new syringe. If peaks are absent, clean syringes more thoroughly. |
| Sample too large | Sample may be back flushing into areas of the injector. Reduce sample size. |
| Septum bleed | Use higher temperature septum or analyze sample at lower injector temperature. Condition septum before use. |
| Impurities from solvent | Use higher quality solvent. Contaminants in reagent can be concentrated during sample process. Analyze solvent blank at each step of the workup to isolate source. |
| Carry over from syringe rinse | Use same solvent in syringe rinse and sample analysis. |
Tailing Peaks:
| Possible Cause: | Solution: |
|---|---|
| Column or injection port temperature too low | Hydrocarbons will tail if the temperature is too low. Increase temperature. |
| Sample components absorbed by inlet liner or column | Replace with new deactivated liner or replace glass wool/packing. If sample is chemically active, may need a column with a different or specialized stationary phase. |
| Co elution of two or more compounds | Reduce column temperature by 20°C and look for partial separation. Change temperature program. |
Broad Solvent Front:
| Possible Cause: | Solution: |
|---|---|
| Column installed poorly | Reinstall column. |
| Leak in the injector | Find and repair leak. |
| Incorrect split flow | Use a higher split flow/ratio. |
| Injection port temperature too low | Use a higher injection port temperature. |
| Large injection volume | Decrease the injection volume. |
| Incorrect split flow | Use a higher split flow/ratio. |
| Injection port temperature too loLow column temperature or high boiling solvent | Increase column temperature or change solvent. |
| Solvent interacting with detector | Change solvent. |