RO water and PO4

[Denadai]

Hi Guys,

A friend of mine bought a DR/890 Portable Colorimeter

http://www.advancedaquarist.com/2005/6/review_album/Colorimeter.jpg/variant/medium

I tested my RO + DI water and my Po4 = 0.12 ppm ( time to change the membrane )

After that, I mix tropic marin salt with my Ro water and Tested again the PO4

Now, the PO4 = 0.07 ppm, less than only the RO water

So, when we mix the salt with Ro water , had precipitation of PO4 ????

Regards

[Randy Holmes-Farley]

Maybe the meter is not accurate?

Did you measure the TDS of the RO/DI water? If it is 0 ppm TDS, I do not believe it will have significant phosphate in it. :)

[Denadai]

<a href=showthread.php?s=&postid=12227071#post12227071 target=_blank>Originally posted</a> by Randy Holmes-Farley
Maybe the meter is not accurate?

Did you measure the TDS of the RO/DI water? If it is 0 ppm TDS, I do not believe it will have significant phosphate in it. :)

I didn´t measure with TDS

I don´t believe that this meter is not accurate

The manufacturer necessarily conducted a calibration, I have a document saying that

[Randy Holmes-Farley]

It may be accurate, but if it is, the DI must be at least partly depleted.

Many salt mixes have some calcium carbonate sediment in them, and that sediment may bind some phosphate from the water. That is a well known phenomenon.

[Icefire]

Aren't all colorimeter +-0.04ppm accuracy?

I saw many thread about that.

[Denadai]

<a href=showthread.php?s=&postid=12230969#post12230969 target=_blank>Originally posted</a> by Icefire
Aren't all colorimeter +-0.04ppm accuracy?

I saw many thread about that.

This is not a hana colorimeter :lol:

The price of this guy, is U$ 3.700,00...here in Brazil

For example, the colorimeter can get 0.01 ppm of NO3

regards

[Boomer]

For example, the colorimeter can get 0.01 ppm of NO3

Not in seawater, unless you have a NSW std, they will be off ;)

[Icefire]

<a href=showthread.php?s=&postid=12231977#post12231977 target=_blank>Originally posted</a> by Denadai
This is not a hana colorimeter :lol:

The price of this guy, is U$ 3.700,00...here in Brazil

For example, the colorimeter can get 0.01 ppm of NO3

regards

Well it's maybe not a cheap Hana but your Hach DR 890 is no better:

http://www.hach.com/hc/view.parameter.range.reagent.info/4847000/PREVIOUS_BREADCRUMB_ID=HC_SEARCH_PRODUCT4847000/SESSIONID|BWpBM01UYzRNREF5TWpjMUptZDFaWE4wVkVwTFVBPT1CRU14TQ==|

The best Estimated Detection Limit is 0.05ppm and 0.07 ppm for most Phosphate (PO4 3-)

So that 3700$ tester is less precise than an ELOS PO4 test which goes to 0.01ppm ;)