Chromatography Forum

What factors can cause Carry over in GC analysis.

Regards
Stephen

Sloppy handing of samples.

Inadequate maintenance of the injector system.

Trying to inject too large a sample that the dead volume of the injector is unable to contain, causing sample to be deposited in cooler areas of the pneumatics.

Surfaces in the injector system that are not inert and allow the retention of sample that the carrier solvent has left behind.

Using too low an injection temperature.

Using too high an injection temperature.

I am sure the list has not exhausted the possibilities.

best wishes,

Rod

I have on where we are trying to do some large volume injections with a relatively high boilign solvent and it appears that the solvent condenses in the split vent trap (or it may have a different name on this multi-mode inlet, but same function) and appears to generate a carry over issue. (Replacing the trap appears to make the problem go away.)

You can also get carryover from failure to get a syringe properly clean. And if you do not risne ou the solvent wash on the autosampler before refilling it, junk from injections can accumulate and you may see analyte peaks coming from the wash bottle.

Your split line can also contaminate. This will give you also carryover. Make sure you clean this part also regularly.
see: http://blog.restek.com/?p=5454