Method Question

[Nchem]

Hello,

My company remediates contaminated properties through chemical oxidation. We are performing a bench test where we want to see if vinyl chloride volatilizes from our groundwater samples after our oxidizing agents are added. Our original idea was to leave headspace in a batched container and sample the headspace after the reaction has occurred. We are having difficulties finding a commercial lab that can analyze this headspace however. Our backup plan was to rent a Photovac Voyager field GC and run that since I believe that just samples headspace. My question to this forum is whether there is a particular method that might work for this. It would be easier for me to find a commercial lab that could do this if I had a better idea of the method. We would send them the entire sample and then they would extract the headspace and run that for VC. Any help with this would be appreciated. Thanks in advance.

Sandy

[H.Thomas]

Dear Sandy,

I'm not sure, that I understand, what you are trying to do. You put some oxidizer into a water sample and want to measure VC in the headspace?

There are several ways you could do this. If you do your experiments directly in headspace vials (10 - 50 ml), there should be no problem in analyzing them by a static headspace sampler or headspace-SPME .

If your containers are somewhat larger, you have to sample the headspace with some kind of adsorption trap. This could a passive sampler, that you just allow to sit in your container for a while or an active one, that pumps the headspace through the trap.

I'm not sure, if the whole experiment makes sense though. VC is volatile anyhow, so instead of putting oxidizer into the water, you could just strip it by bubbling air through the water.

Hartmut

[AICMM]

Nchem,

Can I make a suggestion? I would ask if you are even making it first. No headspace in the vial of water, do the oxidation and submit the sample to any reputable environmental lab for VC analysis by typical VOA methods. If not made, then not a concern.

If you absolutely, positively want to do headspace above the water, let me know how to contact you and I can put you in touch with a lab that can probably do the analysis. Just remember that VC in the headspace is going to want to start moving through the vial septum almost right away.

If made then the question becomes, does it get into the vadose zone? Much harder to test for. Your idea of a Photovac is appropriate, just make sure you use a PID instead of FID or ECD since this is the detector that will give you best response for VC. Also, don't lock yourself in to a Photovac if there is any (ANY!) physical facility on site since you could also install many other varieties of GC (been there, done that.)

Best regards.