Agilent GC troubleshooting guide poster

1 = inR = = inPeak widthAll Peaks Some Peaks SymmetricalFrontingOverloadClean Blank Run(no injection)Ghost CauseSolutionCommentsContaminants introduced with sampleSample or solvent cleanupContaminants in sample process or solventInlet contaminationClean the injector, replace liner, gold seal, and septumTry a condensation test; gas lines may also need cleaning. Take steps to prevent sample backflush (reduce injection volume, lower inlet temperature, use larger volume liner)Septum bleedReplace septumUse a high-quality septum appropriate for the inlet temperatureContamination of sample before introduction to the GCCheck sample handling steps for potential contamination sources: sample cleanup, handling, transfer, and storageUsually occurs after changing a gas cylinderSemivolatile contamination (peak widths will be broader than sample peaks with similar retention )Bake-out column.

2 Solvent rinse the column. Check for contamination in the inlet, carrier gas, or carrier gas linesLimit bake-out to 1 to 2 hours. Only for bonded and cross-linked phasesGhost Peaks or Carryover Excessive Baseline NoiseBaseline Instability or DisturbancesFronting PeaksTailing PeaksSplit PeaksRetention Time ShiftChange in Peak SizeLoss of ResolutionPossible CauseSolutionCommentsInjection techniqueChange techniqueUsually related to erratic plunger depression or having sample in the syringe needle. Use an auto injectorMixed sample solventChange sample solvent to a single solventWorse for solvents with large differences in polarity or boiling pointsPoor column installationReinstall the columnUsually a large error in the insertion distanceSample degradation in the injectorReduce the injector temperatureIf the temperature is too low.

3 Peak broadening or tailing may occurChange to an on-column injectionRequires an on-column injectorPoor sample focusingUse a retention gapFor splitless and on-column injectionPossible CauseSolutionCommentsChange in carrier gas velocityCheck the carrier gas velocityAll peaks will shift in the same direction by approximately the same amountChange in column temperatureCheck the column temperatureNot all peaks will shift by the same amountChange in column dimensionVerify column identityMeasure the carrier gas velocity with an unretained compoundLarge change in compound concentrationTry a different sample concentrationMay also affect adjacent peaks.

4 Sample overloading is corrected with an increase in split ratio or sample dilutionLeak in the injectorLeak check the injectorA change in peak size usually also occursBlockage in a gas lineClean or replace the plugged lineMore common for the split line; also check flow controllers and solenoidsSeptum leakReplace septumCheck for needle barbSample solvent incompatibilityChange sample solventUse a retention gapFor splitless injectionPossible CauseSolutionCommentsChange in detector responseCheck gas flows, temperatures, and settingsAll peaks may not be equally affectedCheck background level or noiseMay be caused by system contamination and not the detectorChange in the split ratioCheck split ratioAll peaks may not be equally affectedChange in the purge activation timeCheck the purge activation lineFor splitless injectionChange in injection volumeCheck the injection techniqueInjection volumes are not linearChange in sample concentrationCheck and verify sample concentrationChanges may also be caused by degradation, evaporation.

5 Or variances in sample temperature or pHLeak in the syringeUse a different syringeSample leaks passed the plunger or around the needle; leaks are not often readily visibleColumn contaminationTrim the columnRemove to 1 meter from the front of the columnSolvent rinse the columnOnly for bonded and cross-linked phasesColumn activityIrreversibleOnly affects active compoundsCoelutionChange column temperature or stationary phaseDecrease column temperature and check for the appearance of a peak shoulder or tailChange in injector discriminationMaintain the same injector parametersMost severe for split injectionsSample flashbackUse Agilent Vapor Volume Calculator to adjust injection size, liner volume, inlet temperature.

6 Or solventLess solvent and higher flow rates are most helpfulDecomposition from inlet contaminationClean the injector; replace liner, gold sealOnly use deactivated liners and glass wool in the inletPossible CauseSolutionCommentsDecrease in separationDifferent column temperatureCheck the column temperatureDifferences in other peaks will be visibleDifferent column dimensions or phaseVerify column identity, measure the carrier gas velocityDifferences in other peaks will be visibleCoelution with another peakChange column temperatureDecrease column temperature and check for the appearance of a peak shoulder or tailIncrease in peak widthChange in carrier gas velocityCheck the carrier gas velocityA change in the retention time also occursColumn contaminationTrim the columnRemove to 1 meter from the front of the columnSolvent rinse the columnOnly for bonded and cross-linked phasesChange in the injectorCheck the injector settingsTypical areas.

7 Split ratio, liner, temperature, injection volumeChange in sample concentrationTry a different sample concentrationPeak widths increase at higher concentrationsImproper solvent effect, lack of focusingLower oven temperature, better solvent, sample phase polarity match, use a retention gapFor splitless injectionPossible CauseSolutionCommentsInjector contaminationClean the injector; replace liner, gold sealTry a condensation test; gas lines may also need cleaningColumn contaminationBake out the columnLimit the bake-out to 1 to 2 hoursSolvent rinse the columnOnly for bonded and cross-linked phasesCheck for inlet contaminationDetector contaminationClean the detectorUsually the noise increases over time and not suddenlyContaminated or low-quality gasesUse better grade gases.

8 Also check for expired Gas Clean filtersUsually occurs after changing a gas cylinderColumn inserted too far into the detectorReinstall the columnConsult GC manual for proper insertion distanceIncorrect detector gas flow ratesAdjust the flow rates to the recommended valuesConsult GC manual for proper flow ratesLeak when using an MS, ECD, or TCDC reate leak-free column unions with an UltiMetal Plus Flexible Metal ferrule or a Self Tightening column nutUsually at the column fittings or injectorOld detector filament, lamp, or electron multiplierReplace appropriate partSeptum degradationReplace septumFor high temperature applications, use an appropriate septumPossible CauseSolutionCommentsInjector contaminationClean the injectorTry a condensation test.

9 Gas lines may also need cleaningColumn contaminationBake out the columnLimit a bake-out to 1 to 2 hoursUnequilibrated detectorAllow the detector to stabilizeSome detectors may require up to 24 hours to fully stabilizeIncompletely conditioned columnFully condition the columnMore critical for trace-level analysesChange in carrier gas flow rate during the temperature programOften normalMS, TCD, and ECD respond to changes in carrier gas flow ratePossible CauseSolutionCommentsColumn overloadReduce mass amount of the analyte to the column. Decrease injection volume, dilute sample, increase split ratioMost common cause for fronting peaksImproper column installationReinstall the column in the injectorConsult the GC manual for the proper installation distanceInjection techniqueChange techniqueUsually related to erratic plunger depression or having sample in the syringe needle.

10 Use an autosamplerCompound very soluble in injection solvent Change solvent. Using a retention gap may helpMore critical for trace-level analysesMixed sample solventChange sample solventWorse for solvents with large differences in polarity or boiling pointsPossible CauseSolutionCommentsColumn contaminationTrim the columnRemove meter from the front of the columnSolvent rinse the columnOnly for bonded and cross-linked phasesCheck for inlet contaminationColumn activityIrreversible. Replace the columnOnly affects active compoundsSolvent-phase polarity mismatchChange sample solvent to a single solventMore tailing for the early eluting peaks or those closest to the solvent frontUse a retention gap3 to 5 meter gap is sufficientSolvent effect violation for splitless or on-column injections Decrease the initial column temperaturePeak tailing decreases with retentionToo low of a split ratioIncrease the split ratioFlow from split vent should be 20 mL/min or higherPoor column installationReinstall the columnMore tailing for the early eluting peaksSome active compounds always tailUtilize inert flow path consumable