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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: bryanh on November 03, 2005, 10:59:25 AM

Title: Phosphate analysis
Post by: bryanh on November 03, 2005, 10:59:25 AM

Hi
I need to know a good method for organic phosphate analysis. I intend to use this for the detection of the presence of DNA (direct DNA analysis is not possible due to mitigating circumstances). So i need a method that will detect phosphate in the DNA or will decompose DNA to release the phosphate for analysis. I am thinking of molybdenum blue but i'm having trouble finding a procedure that i am sure will be able to detect phosphate in DNA.

Also a simple method for carbon and/or ribose analysis would be great too.
Thanks.

Title: Re:Phosphate analysis
Post by: Alberto_Kravina on November 03, 2005, 11:26:08 AM

well...the fosfomolibdate test is quite sensitive, other test for fosfate is the MgNH₄PO₄ precipitation, but I can't think of any other test... ???

Title: Re:Phosphate analysis
Post by: Yggdrasil on November 04, 2005, 12:32:51 AM

Is detecting the DNA spectrophotometrically not an option (DNA absorbs UV light at 260nm, 1.0AU ~ 50µg/ml)?

Title: Re:Phosphate analysis
Post by: bryanh on November 04, 2005, 04:57:17 AM

No due to the presence of other chemicals that also absorb at this range UV spec is not a great option.

Title: Re:Phosphate analysis
Post by: sdekivit on November 04, 2005, 04:17:17 PM

you can determine the purity of your DNA by calculating the A(260) / A(280) - ratio

Title: Re:Phosphate analysis
Post by: bryanh on November 06, 2005, 10:24:03 AM

The DNA isn't even in solution, it is (possibly) bound within a large amount of FeS, it requires acid to dissolve the FeS after which no DNA can be detected by UV which is why I am trying to analyse for the constituents of the DNA, phosphate, ribose, etc..  I thought phosphate analysis would be simple, apparently not.

Title: Re:Phosphate analysis
Post by: kevins on November 09, 2005, 11:08:32 AM

Please try to digest the sample with acid and then by molybdenum blue. The detection limit can be down to 3 ppb as P.
For Carbon determination, dry the sample first and then determine the carbon by high temperature combustion under oxygen atm and pass thro the gas to soda tube.

Title: Re:Phosphate analysis
Post by: Yggdrasil on November 10, 2005, 04:06:45 AM

I recall assaying for free phosphates using ammonium molybdate as a reagent, which allows for colorimetric quantitation of your phosphate concentration.  You can try googling for ammonium molybdate and phosphate assay and see what comes up.