Sensitivity Loss in GC: Causes and Remedies

Fig 1: All 3 peaks show reduced peaks

Some times during GC analysis, some or all of your peaks are showing decreased response consistently. What could be responsible and how do you remedy the situation?

  1. Leaks in the Inlet: A tiny leak in the GC inlet can lead to sensitivity loss. The more volatile components are usually more affected. Check and fix any leak around the injector and the inlet; especially at the septum and around the column connection to the inlet.
  • Inlet discrimination: Two possible scenarios can lead to inlet discrimination. One is if the Inlet temperature is too low; and secondly if the syringe dwells too long in a hot inlet. Both scenarios will lead to later eluting and less volatile compounds having low responses. Ensure the inlet temperature is hot enough for flash vaporization and that your autosampler is setup for fast injection. Where necessary, you may use on-column injection.
  • Too High Initial Column Temperature: If the initial column temperature of your method is too high, especially for splitless injections, this may prevent proper refocusing of the sample. The more volatile components are affected more.  You can remedy this situation by lowering the initial column temperature to lower than the boiling point of the solvent or you can use a less volatile solvent.
  • Inlet Contamination: A contaminated inlet can lead to loss of sensitivity as well as the appearance of strange and spurious peaks. Clean the inlet, replace the liner and the inlet seals. Ensure that your GC is properly and regularly serviced.
  • Column Contamination: Column contamination is also a major cause of sensitivity loss, especially when dealing with samples which contain components that are not very volatile. You can remedy this by baking the column or you can solvent rinse the column. You can also cut off up to 1m from the front of the column, which is where low volatile components typically settle. 1m off a 30m column will not have a significant effect on resolution. Finally, if all these do not work, replace the column.
  • Sample Issues: If the sample concentration is too low or the sample has degraded during storage or handling, sensitivity loss can occur. Prepare a fresh sample ensuring the proper concentration is prepared and the proper handling procedures are followed

Reference: GC Technical Tip (phenomenex.com)

Posted by Muyiwa Adebola


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