Practical Steps in GC Troubleshooting

1 Page 1 Practical Steps in GC Troubleshooting Techniques, Tips, and TricksMark SinnottApplication EngineerGC Columns & SuppliesPage 3 Everything was just fine and then this happened! How do I go about Troubleshooting ? Page 4 Everything was just fine and then this happened! Logic = Something changed (slowly or sudden) = Something is differentTrack Events log book-Changed column, liner, septum, syringe, samples, other method, maintenance, cut column, inlet flush, 5 Troubleshooting Starts with Isolating the problem There are 5 basic areas from where the problem arises INJECTOR FLOW COLUMN DETECTOR ELECTRONICS But of course it can always be some COMBINATIONK nowing what can & can tcause the symptom is the key Logical TroubleshootingPage 6 Typical Problems of Optimized Methods becoming the Reason Why. Peak Tailing Flow Path or Activity Bonus Peaks In Sample or Back Flash (Carry Over) Split Peaks Injector Problems, Mixed Solvent No Peaks Wasn t Introduced, Wasn t Detected Response Changes Activity, Injector Discrimination, Detector Problem Peak Fronting Overload or Solubility Mismatch, Injector Problems Shifting Retention Leaks, Column Aging, Contamination or Damage Loss of Resolution Separation Decreasing, Peak Broadening Baseline Disturbances Column Bleed, Contamination, Electronics Noisy or Spiking Baseline Electronics or Contaminated Detector Quantitation Problems Activity, Injector or Detector Problems Page 7 Peak Tailing INJECTOR or COLUMN is Active-Reversible adsorption of active compounds (-OH, -NH, -SH)

2 FLOW problem -dead volume, obstruction, poor installation , or severe column contaminationMiscellaneous -overloading of PLOT columns, co-elution, polarity mismatch between phase, solute or solvent, and some compounds always tail*Tip = Inject a light hydrocarbon, should not tail unless flow path 8 Bonus PeaksColumn: DB-530 m x mm , mJ&W P/N:125-5032 Oven:60 C for 1 min60-300 C at 20 /min300 C for 3 minCarrier Gas:Helium at 36 cm/secInjector:Split 1:100, 250 Csample C7 -C20 Detector:FID, 250 9 Bonus Peaks or Ghost PeaksContamination in INJECTOR, COLUMN or FLOW (carrier gas)-Carry-over from a backflash or previous sample-Bad tank of gas or traps have expired-Septum bleed*TIP = Run a blank should be blank!Bonus Siloxane PeaksPage 10GC Column Bleed IonsPage (min.)24 pA / 260 CDB-624 30M x .53mm , m12 pA / 320 CDB-1 30m x .32mm , .25 mColumn Bleed is Influenced by:Phase typeTemperatureColumn dimensionsPage 13 Split PeaksINJECTOR(poor sample introduction)-Injecting the sample twice (some how?)

3 -Mixed sample solvent (polarity difference)-Sample in syringe needle (manual inject)INJECTOR(activity)-Breakdown (not really a split peak, 2 peaks)-Sample degradation in injectorVOLATILITYHigh boilers dropping out on Cold Spots-Transfer line temps-Unions or fittings not tracking column temp Page 14No PeaksDETECTOR(not on or not operational)INJECTOR(not working)-Plugged syringe/plunger not moving-Wrong injector (or detector)-Huge leak (older systems)-No carrier gas flowNOT the COLUMN column or No columnPage 15 Peak ResponseAll Change in SizeDETECTOR(response problem)-Settings or flows changed-Electronics failing-Split ratio set incorrectly-Wrong purge activation time-Septum purge flow too high -Injector temperature too low* INJECTOR-Leaky syringe*Tip = Ask is it all of them or some of them, if all then injector or detectorPage 16 Peak ResponseSome Change in SizeINJECTOR or COLUMN is active/contaminated-Irreversible adsorption of active compounds (-OH, -NH, -SH)-Decomposition of sample-Temperature Change Discrimination-Evaporation from sample*Tip = If only some change, then ask which ones?

4 If active compounds then activity. If tracks volatility then cold spots or inlet discrimination. Page 17 Peak FrontingShark Fin Shaped or Just SlightCOLUMN(contaminated)-Overload (More pronounced with large solute and phase polarity differences)INJECTOR-Column installation -Compound very soluble in injection solvent (need retention gap)-Mixed sample solventOTHER-Co-elution-BreakdownPage 18 Retention Time in the septum-Change in injection solvent-Large change in sample concentrationFLOW-Change in gas velocityCOLUMN-Contamination-Damaged stationary phase -Loss of stationary phase-Change in 19min8910111400 ng7 ngEffect of Sample Overload on Retention Time and Peak Shape Page 20 Loss of ResolutionResolution is a function of separation and peak widthSeparationPeak WidthPage 21 Loss of Resolution -Separation DecreaseCOLUMN-Different column temperature-Contamination (more phase?)-Matrix components co-eluting-Different column phase?SeparationPeak WidthPage 22 Loss of Resolution -Peak BroadeningFLOW -Change in carrier gas velocity-Make-up gas COLUMN-Contamination-Phase degradationINJECTOR (efficiency)-Settings, Liner, installation , WidthSeparationPage 23 Baseline DisturbancesSudden Changes, Wandering, or DriftingCOLUMN or DETECTOR-Not fully conditioned or stabilized (electronics)-ContaminationFLOW-Changes in carrier and/or detector gas flows-Valves switching, leaksWANDERDRIFTPage 24 Noisy BaselineFLOW-Contaminated gas-Incorrect detector settingsCOLUMN-Bleed if at high temperature-In detector flame (poor installation )MILDSEVEREDETECTOR-Air leak -ECD, TCD-Electronics malfunctionPage 25 Spiking BaselineDETECTOR-Particles entering the detector-Random: poor connection-Regular.

5 Nearby "cycling" equipment (electronics)Page 26 Quantitation ProblemsDETECTOR-Poor stability (electronics) or Baseline disturbances (contamination)-Outside detector's linear range or wrong settingsActivity (adsorption) in INJECTOR or COLUMNINJECTOR-Technique, settings, conditions-Syringe wornOTHER-Co-elution-Matrix effects-Sample evaporation leaky vials-Sample decompositionWhat is NOT caused by a Column???Peaks!! Any reproducible, sharp chromatographed peak!SiloxanesDegradation product peaks: Endrin Aldehyde, Endrin Ketone, DDE, of sample compoundsSplitting of peaksPage 27 Page 28 Troubleshooting Tools Bleed Profile: baseline problemsInject a non-retained peak: peak shape problemsTest mix: all problemsIsolate the components: all problemsCondensation Test: baseline problemsJumper Tube Test: baseline problemsPage 29 Generating a Bleed ProfileTime (min.) *DB-1 30m x .32mm , .25 mTemperature program // 40 C, hold 1 min // 20 /min to 320 C, hold 10 when the column is new (for future reference) when there is a baseline problemPage 30 Non-Retained Peak ShapesGood InstallationImproper installation orInjector LeakPotential problems: Injector or septum leakToo low of a split ratioLiner problem(broken, leaking, misplaced)Column position in injector and detectorUsed to CheckFlowpathPage 31 Test ConditionsInlet: Split(250 C)Detector:FID(320 C)Carrier Gas: cm/sec ( ml/min)Holdup Compound:Methane( )Temperature Program.

6 Isothermal at 110 CTest MixUsed to determine how good the column is or if the problem is related to the chemical properties of the 32 Test Mixture ComponentsCompoundsHydrocarbonsAlcoholsF AME s, PAH sAcidsBasesPurposeEfficiencyRetentionAct ivityRetentionAcidic CharacterBasic CharacterGroup/Presentation TitleAgilent Page 33 Own Test Mixture More specific to your application Selective detectors Concentrations specific to your application Usesame instrument conditions Easiest to simply inject a calibration standard Store for future measure of column performancePage 34 Isolate the ComponentsSimplify the system: -example -Direct injection instead of P&T sample introductionPut in a known good columnMove column to a different GC, inlet or detectorPage 35 Condensation TestUsed* to isolate the cause of:-Erratic baselines-Ghost peaks or carryover*Use when problems are worse after periods of GC non-usePage 36 Condensation TestProcedureLeave GC at 40-50 C for > 8 hoursBlank runRepeat a blank run immediately after the first blank run is completeCompare the two blank runsPage 37 Condensation TestResultsFirst blank run is worse:-Contaminants (from injector, lines, traps or carrier gas) carried into the columnBlank runs the same.

7 Contaminants are not strongly focused on the front of the columnPage 38 Jumper Tube TestPurposeHelps to locate the source of contamination or noiseIsolates GC componentsPage 39 Jumper Tube TestIsolate the DetectorRemove column from the detectorCap detector and turn onBlank runPage 40 Jumper Tube TestIsolation of Detector -ResultsDetector is the problemDetector OKPage 41 Jumper Tube TestIsolate the InjectorConnect the injector and detector-1-2 meters deactivated fused silica tubingTurn on carrier gasBlank runPage 42 Jumper Tube TestIsolate the Injector -ResultsInjector OKInjector, lines or carriergas contaminatedPage 43 Jumper Tube TestIsolate the ColumnReinstall the columnSetup as beforeBlank RunPage 44 Jumper Tube TestIsolate the Column -ResultsProblem returns: It s the columnProblem gone: Previous leak, solid debris, or installation problemPage 45 And Now Let s do SomePage 46 Troubleshooting -Example #1 Page 47A Real Troubleshooting ExampleNo Peaks1020304050141618202224262830 Page 48Is the flame Lit?

8 Put glass piece over FID outlet----Answer in this case, Water condenseslook at output in instrument guage--is the digital value greater than in this case is approximately pico ampsIs there flow through the column?disconnect column from detector and measure flow with bubble solution or meterAnswer in this case was YES THERE IS FLOWA ssess the observationsFlame is lit and we have flow from end of columnHypothesis: Sample not getting on column-syringe plugged?Take syringe out and make injection manually on a dry paper towelAnswer towel stayes dry (Syringe was clogged with septum)Pull plunger out top, add solvent and replace plunger will usually dislodge septum particle (should hear a little pop)If you can t dislodge plug, Replace syringeReassemble the Injector & Re-injectLogical Steps Taken to Find Peaks(most of our problems are leaks and plugs)Page 49 Peaks !!01020304050141618202224262830 Page 50 Troubleshooting -Example #2 Page 51DB-624 COLUMNQC Test MixColumn:DB-624 30m x 53mm , mCarrier: Helium at 40 cm/secmeasured at 35 CInjector: Mega Direct, 260 CDetector: FID, 300 COven: 35 C for min30 /min to 65 for 10 min1.

9 1,2-Dichloropropane2. Octane3. Tetrachloroethylene4. Chlorobenzene5. (min.) 52 Example of Column ContaminationDB-624 QC Test Mix* After 75 Injections of Oily (min.) *Temperature program// 35 C hold min // 30 /min to 65 C, hold 10 minPage 53 Column and Liner ContaminationInlet coil of columnPage 54 Example of Column ContaminationRemoved 1 1/2 m from injector end *Time (min.) *Before Column rinse and bakeTemperature program // 35 C hold min // 30 /min to 65 C, hold 10 minPage 55 Looks Fixed Doesn't it?Page 56 Example of Column (min.)1 1/2 mtrs removed*QC Test mix to Upper Temperature Limit*Before Column rinse and program // 35 C, hold min // 30 /min to 65 C, hold 15 min // 20 /min to 260 , hold 50 minPage 57 Backflush Column1/16" flexible teflon line to regulated pressure sourceBeaker for solvent collectionCapillary columnSpecial connectorand ferruleFlexible teflontubingSpecial adapterCapVialCapillary columnRinse with 10ml each:Methanol, Methylene Chloride, HexanePage 58 Jumper Tube TestUsed to Isolate Source of Contamination.

10 Cap off the detector and establish normal gas flows and Plot the baseline using a temperature program. If Connect 1 meter of deactivated tubing between the injector and detector. Plot the baseline using a temperature program. If Install the Plot the baseline using a temperature 59 Contaminated InletJumper Tube Test**1/2 mtr length of .53 mm deactivated tubingTemperature program // 35 C, hold min // 30 /min to 65 C for 15 (min.)Page 60 Rinsing InjectorCarrier gas lineC6 MeCl2 Injector bodyGC OvenPage 61 Troubleshooting Tips1. Isolate the problem. (Blank Run, Inject Un-retained Compound, Jumper Tube Test)2. Change only one variable at a Compare before/after chromatograms.(Peak shape, response, retention, baseline rise, background, look for trends, etc.)4. Utilize Technical 62 RememberMultiple cause and effectDo not change too many variables at once Complete system = Carrier Gas + Injector + Column + Detector + Data SystemContact Agilent Chemistries and Supplies Technical Support1-800-227-9770 Option 3, Option 3:Option 1 for GC/GCMS Columns and SuppliesOption 2 for LC/LCMS Columns and SuppliesOption 3 for Sample Preparation, Filtration and QuEChERSO ption 4 for Spectroscopy SuppliesAvailable in the USA 8-5 all time