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Chromatography Integration and Trouble-shooting. Presented by: Marlene Moore [email protected] October 2007. Agenda. Problems Tools Solutions. Problems. Baseline Disturbances Irregular Peak Shapes, Sizes Retention Time Shifts

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Chromatography integration and trouble shooting l.jpg

Chromatography Integration and Trouble-shooting

Presented by: Marlene Moore [email protected]

October 2007


Agenda l.jpg

Agenda

  • Problems

  • Tools

  • Solutions


Problems l.jpg

Problems

  • Baseline Disturbances

  • Irregular Peak Shapes, Sizes

  • Retention Time Shifts

  • Loss of Separation or Resolution

  • Quantitation Difficulties

  • Rapid Column Deterioration

  • Ghost Peaks

  • Broad Solvent Front


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Baseline Disturbances

spiking

noise

wander

drift

offset


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Spiking

  • Particulate Matter Passing Through Detector

  • Loose Connections

    • Cables

    • Circuit boards


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Noise

  • Contaminated Injector/column

  • Physical Defect Detector

  • Defective Detector Board

  • Carrier Gas Leak at Septum or Column

  • FID, NPD, FPD

    • Column in Flame

    • Incorrect Combustion Gases or Flow Rate/leak

  • ECD, TCD

    • Air Leak


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Wander

  • Contaminated Carrier Gas

    • Isothermal Conditions

  • Contaminated Gas Chromatograph

  • Poor Control of Carrier Gas or Detector Gas Flows

  • Poor Thermal Control of Detector


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Drift

  • Septum Bleed

  • Upward

    • GC or column contamination

    • Damaged stationary phase

  • Downward

    • Incomplete conditioning of column

    • Unequilibrated detector


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Offset

  • Contamination:

    • Injector, column, detector

    • Carrier gas - change/install impurity traps

  • Column Inserted Into Flame (FID, NPD, FPD)

  • Malfunctioning or Improperly Set Recording Device


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Peak Shape

Peak Shape tells the story of your chromatography


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Irregular Peak Shapes

tailing

fronting

split

reduced

rounded

negative


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No Peaks

  • Plugged Syringe

  • Broken Column

  • Injecting Sample Into Wrong Injector

  • Column Installed in Wrong Detector

  • Integrator Reading Wrong Signal or Not Connected

  • Detector Not on

  • Temperature

    • Oven not heated

    • Column temperature too low

    • Injection port temperature too low

  • Detector Gases Improperly Set or Not on

  • Very Low or No Carrier Gas Flow


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Reduced Peaks

  • Plugged Syringe

  • Change in Injection Technique

  • Large Leak - Injector

  • Split Ratio Too High

  • Too Short of Purge Activation Time for Splitless Injections

  • Very High Septum Purge Flow

  • Too Low Injector Temperature

  • Column Temperature Too Low

  • Sample Components Absorbed by Column or Inlet Liner


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Reduced Peaks

  • Initial Temperature Column Too High for Splitless or On-column Injections

  • High Background Signal -

    • Contamination

    • Excessive column bleed

    • Check auto zero function and setting

  • Improperly Operated Detectors

  • Impurities Carrier Gas or Detector Gas

  • Detector Compound Mismatch

  • Excessive Attenuated Integrator Signal

  • Sample Concentration or Integrity Problems


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Tailing Peaks

  • Active Injector Liner or Column

  • Contaminated

    • Injector liner

    • Column

  • Dead Volume Caused by Poorly Installed Liner, Column or Union

  • Poorly Cut Column End

  • Polarity Mismatch - Stationary Phase, Solute or Solvent

  • Cold Spot in the Flow Path


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Tailing Peaks

  • Solid Debris in Liner or Column

  • Poor Injection Technique - Too Slow

  • Too Low of a Split Ratio

  • Overloading on a PLOT Column

    • Decrease sample amount

    • Amines and carboxylic acids tail on most columns

    • Need ph modified stationary phase

  • Some Peaks Always Exhibit Tailing


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Rounded or Flat Topped Peaks

  • Overloaded Detector

  • Exceeding Range of Integrator


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Split Peaks

  • Detector Overloaded

  • Poor Injection Technique

  • Poorly Installed Column Into Injector

  • Column Temperature Fluctuations

  • Coelution of Two or More Compounds

  • Mixed Sample Solvent for Splitless or On-column Injections.


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Negative Peaks

  • All Peaks Negative - Polarity Check Connectors

  • TCD - Select Peaks

    • Thermal conductivity of compound greater than carrier gas

  • ECD - After Positive Peak

    • Dirty or old ECD cell


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Retention Time Shifts

  • Different Column Temperature

  • Different Carrier Gas Flow or Linear Velocity

  • Leak in Injector - Septum

  • Contaminated Column

  • Change in Sample Solvent


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Loss of Separation/Resolution

  • Contaminated Column

  • Damaged Stationary Phase

  • Different Column Temperature, Carrier Flow Rate, Column

  • Large Changes in Sample Concentrations

  • Improper Injector Operation


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Quantitation Difficulties

  • Injection Techniques

  • Split Discrimination

  • Different Purge Activation Time for Splitless Injection

  • Baseline Disturbances

  • Improper Integrator Settings

  • Inconsistent Detector Gas Flows or Temperatures

  • Column or Liner Activity


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Rapid Column Deterioration

  • Exposure of Column to Air at Elevated Temperatures

  • Exceeding Upper Temperature Limit of Column

  • Chemical Damage

  • Contamination of Column With High Molecular Weight Materials

  • Column Breakage


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Ghost Peaks

  • Contamination

    • Injector

    • Column

  • Septum Bleed

  • Dirty Syringe

  • Sample Too Large

  • Previous Run Terminated Too Soon

BOO!


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Broad Solvent Front

  • Poorly Installed Column

  • Leak in the Injector

  • Solvent Interacting with Detector

  • Too Low

    • Split Ratio (Flow)

    • Injector Temperature

  • Too Long Purge Activation for Splitless Injections

  • Large Injection Volume

  • Low Column Temperature and High Boiling Solvent

  • High Column Temperature and Low Boiling Solvent


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Tools

  • Flowmeter

  • Syringe (NEW)

  • Methane or Nonretained Compound

  • Septa, Ferrules, Injection Liners (NEW)

  • Leak Detector

  • Column Test Mixture (Reference)

  • Checkout Column

  • Instrument Manuals


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Solutions

Quickest Solution ----

Improve Chromatography ---

Do Manual Integration ---

Get Results out Fast !!

NO!

WRONG ANSWER!!!


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Solutions

  • Preventive Maintenance

    • Clean detector

    • Clean injector

    • Clean and repair parts

    • Clean and tighten connections

    • Follow instrument manual suggestions

  • Allow Time for Optimizing System

    • Integration parameters

    • Programs


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Does anyone have a question?

Question !

Where do you document your trouble shooting?


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