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| GC Troubleshooting |
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| We can help you. |
Click on the respective observation (chromatogram) to display the possible causes
and their remedies. |
no peaks
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missing peaks
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too small peaks
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increasing retention
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decreasing retention
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declining baseline
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rising baseline
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bleeding
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plateaus
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interfering peaks
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spikes, ghost peaks
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strong noise, waves
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peaks on hill
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fronting, tailing
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broad peaks
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cut tops
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negative peaks
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double peaks
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poor resolution
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baseline shift
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1. Observation: no peaks
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Possible causes |
Suggested remedy |
| 1. error in the detector power supply / electronics. |
1. check detector/electronic power supply and cables. |
2. no FID flame.
|
2. check FID; reignite it. |
| 3. syringe defective / clogged. |
3. use a different syringe or clean it. |
| 4. temperature too low for the analytes, oven heating faulty. |
4. check temperature program, oven temperature. |
| 5. detector / software / computer hardware failure. |
5. check integrator, cables; restart computer. |
| 6. no gas flow. |
6. check gas tubes, valves, seals; test gas flow; shorten front of GC column, change injection septum. |
| 7. column connection leaks. |
7. use new ferrules. |
| 8. broken GC column. |
8. if breakage is at the beginning or at the end, remove the short piece; breakage in the middle can be mended with a glass connector; for multiple breakages: replace column. |
2. Observation: Missing or overlapping peaks, poor separation efficiency
|
Possible causes |
Suggested remedy |
| 1. syringe defective / clogged. |
1. use a different syringe or clean it. |
| 2. sample too diluted. |
2. increase injection volume; concentrate sample. |
| 3. sample concentration too high. |
3. decrease injection volume; dilute sample. |
| 4. column connection leaks, column not properly installed |
4. check column installation; search for leaks; replace ferrules. |
| 5. perforated injection septum. |
5. replace septum. |
| 6. injector temperature too low. |
6. check temperature program; increase injector temperature. |
| 7. sample decomposes in the injector. |
7. check temperature program; reduce injector temperature; replace liner; check capillary ends. |
| 8. column oven too hot. |
8. check temperature program, oven temperature (external thermometer); decrease temperature. |
| 9. incorrect flow rate. |
9. measure flow, control and adjust it if necessary. |
| 10. column absorbs or decomposes analytes. |
10. check capillary ends; check intact deactivation using the test mixture; for poor results shorten both column ends by about 10 cm; or replace column; if column test does not show any defects: a) use a column with thicker film
b) use phase with better deactivation
c) use column with special selectivity
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3. Observation: Peaks too small, poor quantification, concentrations not reproducible
|
Possible causes |
Suggested remedy |
| 1. dirty syringe. |
1. use a different syringe or clean it. |
| 2. concentration of sample too low. |
2. increase injection volume; concentrate sample. |
| 3. split too high. |
3. reduce split. |
| 4. sensitivity of detector too low. |
4. inject standard in order to test detector sensitivity. |
| 5. column connection leaks, column not properly installed. |
5. check column installation; search for leaks; replace ferrules. |
| 6. injector temperature too low. |
6. check temperature program, increase injector temperature. |
| 7. dirty ECD. |
7. clean ECD. |
| 8. FID, TCD gas flow too low. |
8. correct flow according to manufacturers’ instructions. |
| 9. sample decomposes. |
9. check capillary ends; check intact deactivation using the test mixture; for poor results shorten both column ends by about 10 cm; or replace column; if column test does not show any defects: a) use a column with thicker film
b) use phase with better deactivation
c) use column with special selectivity. |
4. Observation: Increased or differing retention times / low gas flow
|
Possible causes |
Suggested remedy |
| 1. speed of gas too low. |
1. increase flow. |
| 2. column connection leaks, column not properly installed. |
2. check column installation; search for leaks; replace ferrules. |
| 3. oven temperature too low or unstable. |
3. check temperature program, oven temperature (external thermometer); if the analytes are stable, increase temperature. |
| 4. strong decrease of gas pressure. |
4. replace septum; for an instrument with pressure / temperature control, flow pressure must be higher than 15 psi above the demand at max. temperature of the program. |
| 5. tubes / capillaries / column constricted or blocked. |
5. compare flow at column entrance and outlet with preset flow; check and / or clean gas tubes; in case of pressure build-up cut and remove one turn
(20 cm) from the column or replace column. |
5. Observation: Decreased or differing retention times
|
Possible causes |
Suggested remedy |
| 1. speed of gas too high. |
1. compare flow at column entrance and outlet with preset flow; check gas tubes and pressure gauge; control parameter settings; or replace column. |
| 2. oven temperature too high. |
2. check temperature program, oven temperature (external thermometer); decrease temperature. |
| 3. column length too short. |
3. replace column. |
| 4. film thickness in column too low. |
4. replace column. |
6. Observation: Constantly declining baseline
|
Possible causes |
Suggested remedy |
| 1. gas flow changes with temperature gradient. |
1. check gas content in gas cylinder; pressure must be a few bar above the required pressure at max. temperature; otherwise exchange gas cylinder. |
2. contaminated gas/ poor gas quality
(at constant inlet pressure). |
2. check gas supply. |
| 3. column not properly installed. |
3. check column installation (FID). |
7. Observation: Constantly rising baseline
|
Possible causes |
Suggested remedy |
| 1. leak at column entrance or injection septum. |
1. check column installation; search for leaks; replace ferrules. |
| 2. injector contaminated. |
2. make a run at lower injector temperature; if the baseline improves, replace liner, use low bleed or high temperature septa. |
| 3. column contaminated. |
3. cut two turns from column entrance; rinse column with solvent (only chemically bonded phases); otherwise replace column or use guard column. |
| 4. detector contaminated. |
4. clean detector. |
| 5. increase of temperature too fast. |
5. decrease temperature gradient and end temperature. |
| 6. poor gas quality. |
6. use gas grades recommended for GC; for longer supply lines from gas source to GC use gas purification cartridges directly connected to the GC. |
8. Observation: Increasing baseline, at high temperature bleeding or noise
|
Possible causes |
Suggested remedy |
| 1. decomposition of the stationary phase. |
1. check for leaks; matrix check for compatibility with the column. |
| 2. column contaminated. |
2. cut two turns from column entrance; rinse column with solvent (only chemically bonded phases); otherwise replace column or use guard column. |
| 3. increase of temperature too fast / end temperature too high. |
3. decrease temperature gradient and end temperature. |
| 4. column not properly conditioned. |
4. condition column according to manufacturers’ instructions (while column is not connected to the detector). |
| 5. detector contaminated. |
5. clean detector according to manufacturers’ instructions. |
| 6. poor gas quality. |
6. use gas grades recommended for GC; for longer supply lines from gas source to GC use gas purification cartridges directly connected to the GC. |
9. Observation: Plateaus at certain temperatures
|
Possible causes |
Suggested remedy |
| 1. steps in temperature program too drastic. |
1. avoid very short and strong heating periods. |
10. Observation: Regular interfering peaks
|
Possible causes |
Suggested remedy |
| 1. poor gas quality. |
1. use gas grades recommended for GC; for longer supply lines from gas source to GC use gas purification cartridges directly connected to the GC. |
| 2. FID: dust or contaminants in the detector. |
2. clean detector; if particles are visible in the column or column ends are not cut precisely (frayed edges), cut two turns from the column entrance. |
| 3. electronic defect, damaged cable or detector. |
3. replace cable, contact your GC manufacturer. |
| 4. bleeding of silicon septa. |
4. replace injection septum, use low bleed or high temperature septa. |
11. Observation: Irregular interfering peaks, spikes, ghost peaks
|
Possible causes |
Suggested remedy |
| 1. contamination from vials / septa or sample preparation. |
1. control SPE and / or autosampler vials; use low bleed or high temperature septa. |
| 2. derivatization not quantitative. |
2. check derivatization protocol; use more reactive derivatization reagents. |
| 3. dirty syringe. |
3. use a different syringe or clean it. |
| 4. sample decomposes. |
4. check temperature program, oven temperature (external thermometer); if analytes are not temperature-stable, reduce injector temperature; replace liner. |
| 5. column absorbs or decomposes analytes. |
5. check capillary ends; check intact deactivation using the test mixture; for poor results shorten both column ends by about 10 cm; or replace column; if column test does not show any defects:
a) use a column with thicker film
b) use phase with better deactivation
c) use column with special selectivity.
|
| 6. sample volume too high, double injection. |
6. reduce sample volume or add a blank run after a high volume injection. |
| 7. poor gas quality. |
7. use gas grades recommended for GC; for longer supply lines from gas source to GC use gas purification cartridges directly connected to the GC. |
12. Observation: Strong noise, waves
|
Possible causes |
Suggested remedy |
| 1. leak at column entrance or injection septum. |
1. check column installation; search for leaks; replace ferrules. |
| 2. bleeding of septum / injector contaminated. |
2. make a run with lower injector temperature; if the baseline improves, replace liner, use low bleed or high temperature septa. |
| 3. septum particles in column entrance. |
3. cut 1 turn from column entrance; replace injection septum. |
| 4. column contaminated. |
4. cut two turns from column entrance; rinse column with solvent (only chemically bonded phases); otherwise replace column or use guard column. |
| 5. column not properly conditioned. |
5. condition column according to manufacturers’ instructions (while column is not connected to the detector).
|
| 6. hardware defect. |
6. check temperature program, oven temperature (external thermometer); contact your GC manufacturer. |
| 7. detector contaminated (electronics). |
7. clean detector according to manufacturers’ instructions; check electronics. |
| 8. increase of temperature too fast. |
8. decrease temperature gradient and end temperature. |
| 9. poor gas quality. |
9. use gas grades recommended for GC; for longer supply lines from gas source to GC use gas purification cartridges directly connected to the GC. |
13. Observation: Small peaks on fronting or tailing of bigger peaks
|
Possible causes |
Suggested remedy |
| 1. column not properly installed. |
1. check capillary ends; check tight and correct fit in injector and detector. |
| 2. temperature of injection too low. |
2. check injector temperature; if analytes are stable, increase temperature. |
| 3. solvent not compatible with GC phase. |
3. change solvent. |
| 4. splitter defect. |
4. measure flow and adjust splitter. |
| 5. poorly deactivated column, film thickness too low. |
5. check capillary ends; check intact deactivation using the test mixture; for poor results shorten both column ends by about 10 cm; or replace column. |
14. Observation: Fronting (strong broadening in the ascending part)
Fronting |
Possible causes |
Suggested remedy |
| 1. column overload. |
1. decrease injection volume; dilute sample. |
| 2. sample vaporizes too slowly, not evenly or condenses. |
2. increase injector temperature (consider max. temperature limits of the column). |
| 3. analytes coelute. |
3. change temperature program or use column with different selectivity. |
| 4. sample decomposes. |
4. check temperature program, oven temperature (external thermometer); if analytes are not temperature-stable, reduce injector temperature; replace liner. |
| 5. column absorbs or decomposes analytes. |
5. check capillary ends; check intact deactivation using the test mixture; for poor results shorten both column ends by about 10 cm; or replace column; if column test does not show any defects: a) use a column with thicker film
b) use phase with better deactivation
c) use column with special selectivity.
|
15. Observation: Tailing (strong broadening in the descending part)
Tailing |
Possible causes |
Suggested remedy |
| 1. sample vaporizes too slowly, not evenly or condenses. |
1. increase injector temperature (consider max. temperature limits of the column). |
| 2. high-boiling analytes. |
2. derivatize polar, basic or high-boiling compounds. |
|
3. system leaks.
|
3. check column installation; search for leaks; replace ferrules. |
| 4. analytes coelute. |
4. change temperature program or use column with different selectivity. |
| 5. sample decomposes. |
5. check temperature program, oven temperature (external thermometer); if analytes are not temperature-stable, reduce injector temperature; replace liner by a deactivated one.
|
| 6. column absorbs or decomposes analytes. |
6. check capillary ends; check intact deactivation using the test mixture; for poor results shorten both column ends by about 10 cm; or replace column; if column test does not show any defects: a) use a column with thicker film
b) use phase with better deactivation
c) use column with special selectivity. |
| 7. split rate too low. |
7. increase split rate. |
| 8. analytes always tending to tail. |
8. no chance for symmetric peaks. |
| 9. column overload. |
9. decrease injection volume; dilute sample. |
16. Observation: Broad peaks
|
Possible causes |
Suggested remedy |
| 1. poor focussing. |
1. decrease start temperature of the program. |
| 2. flow too high or too low. |
2. measure flow, control and adjust it if necessary. |
|
3. split rate too low.
|
3. increase split rate. |
| 4. column overloaded. |
4. decrease injection volume, dilute sample or increase split flow. |
17. Observation: Cut tops of peaks, broad peaks
|
Possible causes |
Suggested remedy |
| 1. detector overloaded. |
1. decrease injection volume; dilute sample; increase the split flow. |
| 2. column overloaded. |
2. decrease injection volume; increase split flow. |
|
3. zero point is outside the display.
|
3. change scale. |
18. Observation: Negative peaks, negative signals
|
Possible causes |
Suggested remedy |
| 1. polarity of integrator is inverted. |
1. invert polarity at the instrument. |
| 2. column overload. |
2. decrease injection volume; dilute sample / increase split rate. |
| 3. pressure fluctuations. |
3. check gas tubes, valves, seals; test gas flow; change injection septum; contact hardware manufacturer. |
| 4. detector contaminated. |
4. clean detector as specified by the manufacturer. |
| 5. electronic artefacts. |
5. check detector, A/D converter. |
19. Observation: Double peaks, doubled peak tops
|
Possible causes |
Suggested remedy |
| 1. solvent and column not compatible. |
1. change solvent or use guard column. |
| 2. solvent mixtures with large differences in boiling point and polarity. |
2. use just one solvent. |
|
3. sample decomposes.
|
3. check temperature program, oven temperature (external thermometer); if analytes are not temperature-stable, reduce injector temperature; replace liner by a deactivated one. |
| 4. analytes coelute. |
4. modify temperature program or use longer column; possibly change column polarity. |
| 5. detector overload. |
5. inject less; control make-up flow.
|
20. Observation: Short lifetime, poor resolution, lack of separation efficiency
|
Possible causes |
Suggested remedy |
| 1. impurities on the column. |
1. cut two turns from column entrance; rinse column with solvent (only chemically bonded phases); otherwise replace column or use guard column. |
| 2. contamination from vials / septa or sample preparation. |
2. check SPE and / or autosampler vials; use low bleed or high temperature septa. |
|
3. polymerization on the column.
|
3. use guard column (at least 10 m). |
| 4. separation efficiency decreases for repeated injections, improves after reconditioning. |
4. use guard column; reduce injection volume; modify temperature program; for repeated injections increase end temperature (if possible) and use longer temperature program. |
| 5. temperature too high / temperature increase too fast. |
5. decrease oven temperature and / or temperature gradient (should not be higher than 25 °C/min).
|
| 6. cooling too fast. |
6. do not open oven door at high temperatures. |
| 7. temperature too low / condensation. |
7. increase injector temperature and/or start temperature. |
| 8. poor deactivation. |
8. check capillary ends; check intact deactivation using the test mixture; for poor results shorten both column ends by about 10 cm; or replace column; if column test does not show any defects:
a) use a column with thicker film
b) use phase with better deactivation
c) use column with special selectivity. |
| 9. oxygen / air in the system. |
9. use oxygen absorber or gas grade with less oxygen. |
| 10. water content too high. |
10. reduce water content. |
| 11. head-space analysis: permanent air injections. |
11. displace oxygen from vials with an inert gas. |
21. Observation: Baseline increases or decreases before or after a peak
|
Possible causes |
Suggested remedy |
| 1. injection volume too high. |
1. decrease injection volume; dilute sample; clean injection system. |
| 2. column bleeding due to poor conditioning. |
2. condition column according to manufacturers’ instructions (while column is not connected to the detector). |
|
3. pressure fluctuations.
|
3. check gas tubes, valves, seals; test gas flow; change injection septum; contact hardware manufacturer. |
| 4. injector temperature too low. |
4. check injector temperature; if the analytes are stable, increase temperature. |
| 5. injection septum perforated. |
5. replace septum.
|
| 6. wrong TCD gas flow. |
6. adjust flow according to manufacturers’ instructions. |
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