Measuring low PO4 levels.

[Bojan]

I use Hanna low range photometer for measuring Phosphate
Accuracy = 0,04 ppm
resolution is 0,01 ppm

or Salifert P04 test kit

With both it is not possible to measure very low concentration


So, I have idea to concentrate sample. Do you know what will happen with phosphates if I will cook water sample, that 90% of PO4 will evaporate so theoretically I will have 10 time higher concentration if PO4 is not destroyed during cooking ?

Salt concentration will also be 10 times higher. Is this problem ?

 

[Randy Holmes-Farley]

If you boil the water, the CO2 wil be driven out, pH will rise, and calcium phosphate and calcium carbonate (and magnesium hydroxide/phosphate) may precipitate when it would otherwise stay in solution.

 

[Bojan]

Thanks Randy.

Do you have any other idea for concentration of the water sample and not precipitate PO4 from the solution ?

 

[Randy Holmes-Farley]

If you acidify it first, you might avoid that problem, but I do not know how well the tests would work in acidic conditions, or whether that step itself might introduce some phosphate.

 

[Bojan]

Randy

Do you know what will happen

if I add 10 reagents in the water sample for hanna P04 photometer ?

or

if i add everything 10 times more than specified in the user manual for Salifert P04 test kit ?

 

[Randy Holmes-Farley]

I don't expect it becomes any more sensitive. The phosphate is likely already reacted in those tests, and extra reagent won't change that.

 

[Bojan]

Thanks

 

[Randy Holmes-Farley]

You're welcome.

Sorry it wasn't more useful.