Chromatography Forum

I have not worked with headspace vials before so I am not sure how to determine if the crimper has made a good seal or not. How can I determine if the crimper made a good seal on an autosampler vial? I don't have anyone at my lab that has used headspace before so I can't ask anyone here.

The vials are 22ml from Perkin Elmer with butyl rubber stoppers and a aluminum crimp cap. We are using an electric crimper

Thank you.

Christy

Hello

Just try to turn the lid. If it stays (or moves with resistance) the seal is good

Regards

Tomasz Kubowicz

Do not be tempted to crimp harder than you need to - when the septa warm up in the headspacer oven they can buckle and begin to leak.

As a check that the crimper is adjusted properly put a bit of something very volatile into a vial, crimp on the cap and then immerse the whole vial in hot water. A stream of bubbles means a leak ( a few bubbles are air escaping from between the crimp and the vial rim).

Peter

Thanks for the reply Peter. Your suggestion gives me a way to see how to set the crimper for us and see if it is doing a good job or not.

I will give it a try.

Christy

As an addition to Peter's practical test nice illustration by MicroSolv Technology Corporation:

I found that image also when doing a search, but it really didn't help me as the crimper I am using is leaving dents on top of the crimp caps when done and I'm not sure if that is good or not. Here is what my a/s vials look like after being crimped:


I am able to set the electronic crimper so it crimps less or more. Can you tell by looking at the picture if I am having a bad crimp or not?

Luckily I'm still in development with this method, so I am making sure all is OK with this process. The person working on this before me, found she had to double crimp each cap where she would crimp it once, turn the vial 180 degrees and crimp it again. I am concerned with doing that as if the crimper is not working right on the first crimp, then we should find out why.

Thank you.

Christy

For me - bad crimps.
That doesn't necessarily mean bad tightness.

Hi Christy

Those look bad to me. Those radial dents on the caps are something that I have never seen before. The cap walls are buckled (back right vial but it might be a reflection of something else)which is usually a sign of too tight crimping, but the tops are flat (except for the radial dents) which suggests OK crimping. It might be a trick of the wide angle lens, but it also looks as if the two on the right are not crimped evenly all round.

The crimp head might need cleaning and lightly lubricating, I suspect the the jaws are not moving evenly.

Peter

I think it was my technique. The service tech from PE came out to look at my instrument and I asked him. He showed me what I was doing wrong. Now I know, what is it? - Knowledge is power. Thanks for everyone's help. It is nice to have this forum to get help from.

Christy

Yep I spent a week ago Friday adjusting my crimper to perfection. Optimal reproducible crimping can be a significant variable in headspace especially with vial pressurizing systems.

I think it was my technique. The service tech from PE came out to look at my instrument and I asked him. He showed me what I was doing wrong. Now I know, what is it? - Knowledge is power. Thanks for everyone's help. It is nice to have this forum to get help from.

Christy

"Knowledge is power. Thanks for everyone's help. It is nice to have this forum to get help from."

So how about spreading the love and telling us what the PE tech told you - then we all learn something.

Peter

I will share.

He told me to firmly press the autosampler vial up into the crimper and hold it firmly against the bottom of the crimper. He crimped it once then turned it about 180 degrees and crimped it again. After this crimping the alunimum top didn't move at all on the vial and the crimp cap was smooth and unbroken.

I was just putting the vial into the crimper and crimping it. I wasn't holding the vial tightly against the crimper as I did it.

I use an electric crimper from Perkin Elmer: http://www.perkinelmer.com/Catalog/Fami ... 20Crimpers

Christy

Thanks Christy - it's all in the details !. I have never bothered with the 180 rotation and second crimp but it can't do any harm.

Peter