Troubleshooting Guide
Contents
1. the purge activation time Check injection technique Check and verify sample concentration Use a different syringe Trim the column Solvent rinse the column Irreversible Comments All peaks may not be equally affected May be caused by system contamination and not the detector Decrease column temperature and check for appearance of a peak shoulder or tail For splitless injection Injection volumes are not linear Sample degradation variances in sample temperature or ph Sample leaks passed the plunger or around the needle Leaks are often not readily visible Remove about half to 1 meter from the front of the column Only bonded and cross linked phases Only affects active compounds Possible Cause Column contamination Column activity Solvent phase polarity mismatch Solvent effect violation for splitless or on column injections Too low of a split ratio Poor column installation Some active compounds always tail Possible Cause Change in carrier gas velocity Change in column temperature Change in column dimension Large change in compound concentration Leak in the injector Blockage in gas line Possible Cause Injection technique Mixed sample solvent Poor column installation Sample degradation in the injector Tailing Peaks Solution Trim the column Solvent rinse the column Irreversible temperature Increase the split ratior Reinstall the column None2. Change sample solvent Install a retention gap Decrease the initial column Comments Trim half to 1 meter from the front of the column Only for bonded and cross linked phases Only affects active compounds More tailing for the eluting peaks or those closest the solvent front 3 to 5 meter retention gap is sufficient Peak tailing decreases with retention gas lines may need cleaning Flow from split vent should be 20ml min or higher More tailing for the early eluting peaks Most common for amines and carboxylic acids Retention Time Shift Solution Check gas velocity Check column temperature Verify column identity Use a different sample concentration Leak check the injector Clean or replace clogged line Comments All peaks will shift in the same direction by approximately the same amount Not all peaks will shift by the same amount Switched column May also affect adjacent peaks Achange in the peak size occurs also Most common for split line Check flow controllers and solenoids Split Peaks Solution Change technique Change to single solvent Reinstall column in the injector Reduce the injector temperature Change to an on column injection Comments Erratic plunger depression or having sample in needle Worse for solvents with large differences in polarity or boiling points Usually a large error in the insertion distance Peak broadening or tailing may occur if the temper
3. Possible Cause Injector contamination Column contamination Detector contamination Contaminated or low quality gases Incorrect detector gas flow rates Leak when using MS ECD or TCD Old detector filament lamp or multiplier Un equilibrated detector Incompletely conditioned column Possible Cause Change in detector response Co elution Change in the purge activation time Change in the injection volume Change in sample concentration Leak in the syringe Column contamination Column activity Troubleshooting Guide GC Excessive Baseline Noise Solution clean the injector Bake out the column Solvent rinse the column clean the detector use better grade gases traps values find and eliminate the leak replace appropriate part allow detector to stabilize fully condition column check for gas leaks and expired gas adjust flow rates to recommended Comments gas lines may need cleaning Limit bake out to 2 hrs Bonded and cross linked phases only noise increases over time and not suddenly usually occurs after changing a gas cylinder consult literature usually at the column fittings or injector use new part may require up to 24 hrs to fully stabilize critical for trace level analyses Change in Peak Size Solution Check gas flows temperatures and settings Check background level or noise Change column temperature or stationary phase Check
4. ature is too low Requires an on column injector
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