Chromatography Forum

Hello everyone,

I'm new in this forum, I found it by a quick search on google.

I hope someone will be able to help me to solve the problem I encounter.
First, sorry for possible mistakes in formulation as english is not my native language.

Then, my problem occur during sequences of analysis of sample of a few semivolatil compounds (PCB, Phtalate, Pest.,...) extract in hexane on agilent GCMS (5977A).

The problem is a change of sensibility/response of the MS on every compound during the sequence, this happen after the injection of some kind of sample (especially the extract of Reference sample NIST2585 indoor dust). Even if the compound is not include on the sample.

For example with the sequence of injections of standards solutions of PCB 52 in hexane with injection of 2 reference extracts in hexane (without PCB) every 5 standards, here is the kind of response we get :



If someone have some more precise idea of where the problem can from, i'll be really happy to discuss.
Don't hesitate if you want more detail on method


Thanks a lot

Thomas

There is something in the extract of the NIST dust that is changing your inlet conditions and increasing the amount of analytes reaching the detector. What type of inlet / liner are you using and is this a splitless injection with a pressure pulse?
Have you done any cleanup on the extracts?

Hello thanks for your help.
Indeed, we use a splitless injection of 2 µL with pressure pulse. The liner is an universal low PSI drop with wool.
We don't cleanup our extract as we try to limit step of sample preparation to avoid contamination espetially by phtalate (DBP, DEHA,...).

If you try a 1uL injection does it help?
The 2uL of hexane could be a little too much volume.