View Full Version : Measuring low PO4 levels.

01/25/2006, 07:56 AM
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
01/25/2006, 07:59 AM
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.

01/25/2006, 08:02 AM
Thanks Randy.

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

Randy Holmes-Farley
01/25/2006, 08:04 AM
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.

01/25/2006, 08:15 AM

Do you know what will happen

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


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

Randy Holmes-Farley
01/25/2006, 08:32 AM
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.

01/25/2006, 10:53 AM

Randy Holmes-Farley
01/25/2006, 11:05 AM
You're welcome.

Sorry it wasn't more useful. :)