Chromatography Forum

Hi guys!

I've got a question. In head space vial of 20 ml what is the best volume of my solution to be examinated that I must put in? 2 or 5 or 10 or 15 ml? What is the different? It's better more volume than less volume, or reverse?

I don't Know if is best to have more liquid solution or more free volume where volatile compound can go after extraction... Can you light up me?

Thanks you!

It is metter af analite's concentration.
If concentration is hight, you may add only 1 ml of solution. Try different volumes, and choose one, that suits you most.

It depends upon the partition coefficient, Henry's Law, and how long you want to heat the vial.

More liquid volume means more equilibration time and more opportunity for the analyte to enter the sealing septum material. Less volume means a quicker equilibration, more reproducibility, but a lower concentration of analyte at equilibration.

If you wanted to measure toluene in water........... more water, less headspace.

If you wanted to measure acetone in water............ less water, more headspace.

The best way is to add the same sample to several vials and then add varying amounts of water or DMF to each vial. Heat them for the same time and check your results.

General rule: Use the smallest possible vial, and the smallest possible sample size.

This is why it is called RESEARCH.

best wishes,

Rod

Maximal volume is 2/3 of the nominal volume.
If vial 20 ml - maximum 15 ml. Less is possible, but not longerThe reason - if you pour liquid "to the neck of the bottle" - punched krushku needle plunged into her, and HS suck fluid into the internal communication.