Chromatography Integration and Troubleshooting

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Chromatography Integration and Trouble-shooting

• Presented by Marlene Moore mmoore_at_advancedsys.c
  om
• October 2007

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Agenda

• Problems
• Tools
• Solutions

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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
rounded
negative
reduced
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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?