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Study Notes: Achieving Good Separations with GC

What can we say to make you a better chromatographer? You should remember that GC is an art as well as a science. We have covered some of the science in this section but the art must come from practice, experience and something called common sense.

The keys to good separations are as follows.

  • Follow all manufacturer’s instructions, SOPs and work document instructions.
  • Know the chemistry of the components in the samples, the carrier gas and the stationary phase.
  • Obtain a good application from a manufacturer and work with that and modify it to suit.
  • Pay great attention to detail:
    • No leaks in the system
    • Carrier gas is an appropriate gas of adequate purity
    • No poisons in the gas system (replace ‘spent’ filters and traps on the supply lines)
    • Use very high quality reagents and gases
    • Keep an eye on temperatures (injector, column and detector)
    • Follow the manufacturer’s and application instructions
    • Perform routine maintenance as required
    • Do not cut corners and do not be in a rush.
  • Check flow rates and determine that the correct gas is connected before commencing the run.
  • Look after that column and treat columns as fragile.
  • Keep your eye on flow rates and pressures during the run.
  • NEVER run out of carrier gas.
  • NEVER run out of hydrogen and air for the FID.
  • Choose the correct detector and detector parameters.
  • Adjust the ‘gain’ on the chart recorder so that the peaks are not too small nor run off the top of the trace.
  • Adjust the baseline so that the bottom of the chromatogram trace sits correctly on the chart.
  • Use a reliable chart recorder.
  • Be exacting with injection volumes - use the same technique to inject every time.
  • If using an autosampler be scrupulous in making up the sample vials.
  • Wash out the injection syringe every time.
  • Be careful when moving gas cylinders - they are heavy and potentially dangerous.
  • Be kind to your GCs and have them serviced regularly.
  • Have a clean and tidy work area.
  • Clean dust from the outside of the GC and all components.
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