I am trying to use ITEX GC MS to quantify benzaldehyde and 3 methyl butanal from plant matrices. I am struggling with the calibration curves for the 2 compounds, we are not able to get a linear trend. Concentrations of calibration curve are 20-200 ppb for benzaldehyde and 1000 - 5000 ppb for 3methylbutanal. Are there any trick with ITEX we need to know to get sth reproducible and relevant ? many thanks for your help!
In your post you do not mention any sample preparation aside from doing the matrix isolation by headspace sampling. Aldehydes are in general reactive, especially at high temperature. In general for GC and GCMS analysis of aldehydes, they are derivatized to form more stable compounds. There are a wide variety of derivatizing agents, so selecting one or more that is apporpriate for your analytes, sampling technique and sample composition should be feasible, and should help resolve at least some of your issues.
This is by no means an answer but I am just looking at the concentrations you are using and comparing to the linear ranges shown in this ITEX document from PAL. They seem to be much lower concentrations than in your standard solutions. Could you try diluting your samples? https://www.palsystem.com/fileadmin/public/docs/Downloads/Brochures/ITEX_Brochure_Low_Res.pdf
I realise that the analytes are not the same but it would be a simple troubleshooting test. I also agree with the previous answer, the extractions conditions for the headspace sampling are important too.
John Canham @Colin Ray thank you for your answer, well actually samples have to be prepared in acetone/water solution, as the standards are. I will keep in mind your advice and try to dilute my standards, it seems that indeed that might be a bit too high
@juliette Caron Do you evaporate your aceton/water dry before ITEX. Or do you apply it directly to the standard solution?
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