Post subject: Re: A B C Jade and their ftir / Uv vis spectra
Posted: Thu Mar 22, 2012 10:25 am
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Joined: Mon Apr 16, 2007 12:05 am Posts: 1499
I thought I'd seen something on this topic, and searched through old posts. Funny enough, I found the information in one of MY posts...
This link is a pdf file of a single page that presents FTIR spectra of "A" and "B" jadeite:
It seems the presence of structure between 3200 - 2800 cm-1 identifies the presence of hydrocarbons (and thus indicates "B" jadeite), while the absence of structure in this wavenumber range indicates "A" jadeite.
Last edited by Brian on Thu Mar 22, 2012 10:29 am, edited 1 time in total.
Post subject: Re: A B C Jade and their ftir / Uv vis spectra
Posted: Thu Mar 22, 2012 11:29 am
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Joined: Sun Mar 08, 2009 2:16 pm Posts: 331
Alberto,
You will want to take your readings in Transmittance mode. It is also best if you use a DRIFTS module. We get great results with readings very close to that shown here in the graph, but also make sure to look at the added information that is found in the 3600-5000 cm-1.
Post subject: Re: A B C Jade and their ftir / Uv vis spectra
Posted: Thu Mar 22, 2012 12:19 pm
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Joined: Mon Apr 16, 2007 12:05 am Posts: 1499
Bear Williams- SGL wrote:
You will want to take your readings in Transmittance mode.
Bear, that is pretty interesting. I once convinced our chemists to take an FTIR in reflectance mode of a jade piece we had in our collection, after I assured them it wouldn't scratch their precious window.
I would have thought that if the resin had penetrated into the volume, it should also be present in detectable levels at the surface.
I didn't see an effective way to arrange my chemists' FTIR to collect a transmittance measurement. For a transparent fluid in a calibrated volume, sure... but for an odd-shaped, translucent piece it seems kind of awkward.
Post subject: Re: A B C Jade and their ftir / Uv vis spectra
Posted: Thu Mar 22, 2012 1:16 pm
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Joined: Sun Mar 08, 2009 2:16 pm Posts: 331
You're right Brian. Our readings for jade are actually taken via Reflectance, which is why I use the DRIFTS unit. I should have stated that most jades have to be taken in reflectance anyway, BUT, when you are viewing the spectra, you want to view it as a transmission reading, because viewing it as an absorption shows too much noise... at least this is the case with my Perkin Elmer software... Bear
Post subject: Re: A B C Jade and their ftir / Uv vis spectra
Posted: Thu Mar 22, 2012 4:27 pm
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Joined: Mon Apr 16, 2007 12:05 am Posts: 1499
How funny, getting reflectance-transmission confused with absorbance-transmission.
Below are FTIR spectra of A and B jadeite collected by Bear. Exhibits the same phenomenon seen in the other spectra; nicely done. But you'll need to click on the image to get a popup you can enlarge to read the wavenumber scale.
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