[bryanh]

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.

[Alberto_Kravina]

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

[Yggdrasil]

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

[bryanh]

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

[sdekivit]

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

[bryanh]

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.

[kevins]

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.

[Yggdrasil]

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.