Chromatography Forum

Hello everybody and thanks for the reading, it's my first time in this forum,

I'm developing a new method for the analysis of pvc material (for sinthetic leather exactly), where by heaspace-GC-MS I must quantify the amount of dimethylformamide and toluene.
Anyone has idea which are the best condition for determinated these solvents by headspace?

Thanks

Hello.
Toluene should be easy but DMFa isn't. If possible HS temperature should be higher than it's boiling temperature (153 °C).

I agree. Static headspace will probably work for toluene but I fear you will struggle with DMF. An alternative is static-headspace solid-phase microextraction. I analyze a lot of polymeric packaging materials and plasticized pvc is in that group. I use SPME almost exclusively. I use some twister/thermal desorption just for fun. SPME is easily my workhorse sampling method. I'm confident you'll be able to get the DMF using SPME.

What concentrations do you expect in your pvc samples and how heavily are they plasticized (Shore A hardness)?

Thank you! Maybe I'll use the SPME, at the moment I don't know this technique, but reading about it doesn't seem so difficult. The hardness of my PVC at the moment I don't remember, next days I'll look... My pvc is a quite elastic material, If by headspace I heat it near the softening point (180-200°C) could the pvc release all the dmf?

If by headspace I heat it near the softening point (180-200°C) could the pvc release all the dmf?

Some DMFa can be dissolved in the matrix however recovery can be checked via standard addition method.

To get all of the DMF out, you have to use a technique called thermal extraction. Headspace analysis generally relies on a partitioning between the condensed phase and the gaseous phase. Standard addition is the way to do quantitation in a matrix like plasticized pvc. You need to make sure when you make your additions that you get to a situation where your added analyte gets to an equilibrium situation between the condensed phase and the gaseous phase. DMF is a great solvent for plasticized PVC so it's really soluble. Dissolution of added DMF to pvc shouldn't take too long.

I am way out of my element in this forum... I'm not used to everybody being smarter than me... It's disconcerting... I feel like everything just goes way over my head.