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9 Questions to Test Your Knowledge of GC Injection

Martin Perkins

30th July 2014


Far too many users of gas chromatography understand far too little about sample introduction.

There are plenty of people around who can give a very complete account of the innermost workings of a complex mass spectrometer, but fail totally when asked to explain what happens when a liquid phase sample is injected into a GC inlet.

Please let me test your knowledge:

  1. What is the difference between split and splitless injection?
  2. What is injector discrimination, what causes it and how can it be avoided?
  3. When might you use on-column injection and why?
  4. Why is it a bad idea to inject a water sample directly into a GC?
  5. Can you explain how analytes are focused in splitless injection?
  6. What causes peak splitting and how can it be cured?
  7. What is a retention gap for and how does it work?
  8. Why is thermal degradation less common when using split (verses to splitless) injection?
  9. Why would you choose to use a PTV injector?

If you can provide a decent answer to most of these questions, then you deserve a pat on the back.

If you can’t, then all I have to say is shame on you and remember the old adage about data processing – rubbish in, rubbish out, applies to GC-MS as well.

Over the quiet summer period, I plan to prepare a series of blog posts that address this subject and answer all of the questions above.