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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: alrob8a on January 18, 2013, 12:47:30 AM

Title: UV detection of organic-N
Post by: alrob8a on January 18, 2013, 12:47:30 AM

Hi guys,

At work I am doing a whole range of potential N mineralisation experiments on soils, and have been trying to nut out one of the methods.

Extract soil with 0.01M NaHCO3. Run through spectro at 200nm and 260nm.

200nm is a function of nitrate as well as organic N.
260nm is a function of organic N.

The difference gives me nitrates, which is what I'm after.

Easy peasy make standards up with KNO3 for nitrates, but how do I go about understanding the organic-N fraction? I tried making up standards with urea but found no absorption at 260nm.

Any help would be fantastic :)

Alister.

Title: Re: UV detection of organic-N
Post by: Stepan on January 18, 2013, 09:59:55 AM

Not sure if this method would work at all. 99% of all chemicals adsorb at 200 nm and therefore will give you positive interference. About 90% of chemicals also adsorb at 260 nm and therefore will give you an error reading once more.

The method you quoted is part of IC-UV method, where chemicals and ions are first separated by chromatography, and after detected with UV.