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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: bigshot82 on June 27, 2008, 12:30:09 PM

Title: reacion with acid
Post by: bigshot82 on June 27, 2008, 12:30:09 PM

can you mix trimethyl phosphate and phosphoric acid? I need the acid to be present as the chemical shift reference.

Title: Re: reacion with acid
Post by: bigshot82 on June 29, 2008, 06:02:29 PM

77 views and 0 replies?? seriously?!! >:(

Title: Re: reacion with acid
Post by: azmanam on June 29, 2008, 11:56:08 PM

If you're talking of a chemical shift reference as in NMR analysis, try a sealed tube with the acid inside the NMR tube with your phosphate sample.  That way the NMR will still observe the acid, but the acid will not be in contact with the phosphate

Title: Re: reacion with acid
Post by: macman104 on June 30, 2008, 01:24:50 AM

Yea, you can try putting your reference sample in a capillary tube and seal the tube.  Then put that in your NMR tube.  The only issue may be that sometimes the high spinning can cause the tube to either:  not spin evenly, or if it bangs around, it could break. 

Otherwise, you can get a special coaxial NMR tube like these (http://www.wilmad-labglass.com/group/2094).  They're very handy.  We have our compounds in water (we observe the effects of the magnetic compounds on the water peak), and then we put D2O in the inner tube so we can lock the signal on the D2O solvent.

Title: Re: reacion with acid
Post by: AWK on June 30, 2008, 06:17:34 AM

85 % H3PO4 is usually used as an exterrnal reference standard