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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: _Espard_ on April 29, 2015, 05:53:19 AM

Title: Solid sample between KBr discs for FT-IR
Post by: _Espard_ on April 29, 2015, 05:53:19 AM

This may sound a bit absurd, but I currently don't have the capability to make a KBr pellet to analyze my solid sample... is it possible to put a small amount of solid between KBr discs and run the analysis that way?

I'm guessing there has to be some reason why this isn't an acceptable method, a bit of insight would be great.

Title: Re: Solid sample between KBr discs for FT-IR
Post by: Arkcon on April 29, 2015, 07:23:41 AM

The only issue I see right away is does your FT-IR have a KBr disk sample holder?  Are your discs in good shape -- if you haven't used them for a whiler, or ever, are they clean and clear?

Title: Re: Solid sample between KBr discs for FT-IR
Post by: _Espard_ on April 29, 2015, 07:25:48 AM

Yes, the FT-IR instrument has the capability to hold KBr salt disks. The disks themselves are in moderate to good condition, and decently clear. They haven't had much use, so they're not awful.

Title: Re: Solid sample between KBr discs for FT-IR
Post by: pgk on April 29, 2015, 07:33:18 AM

If it is a thin and transparent film, e.g. polyethylene or polypropylene film, Yes.
Otherwise, you can suspend (or dissolve) your solid in liquid paraffin (parafin oil, Nujol) but the peaks of paraffin might cover the peaks of interest of your compound. So, take a blank spectrum and compare spectra, by dissolving your solid in another solvent, e.g. dichloromethane.