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Old 09/11/2019, 01:37 AM   #1
jjencek
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Hanna Phosphorus Test Turning Navy Blue - help

I have been using the Hanna Checker Phosphotus ULR for some time now.

My results are pretty consistent between 0 to 5 ppb (0.01533 ppm phosphate).

About two weeks ago it was close to zero.

When I measured it today, the solution turned navy blue as soon as I added the reagent to it. Of course the tester went over the scale.

I have never seen it before - anybody has an explanation?


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Old 09/11/2019, 05:16 AM   #2
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I have additional information ...

I purchased SALIFERT Phosphate test kit to verify the Hanna results. I know SALIFERT is not that accurate in low values, but I see very little color change - indicating 0-0.03 ppm.

That really does not make sense. Hanna checker HI 736 indicates above the limit of the checker. That would be, after conversion, above 0.6132 ppm.


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Old 09/11/2019, 07:55 AM   #3
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And did you try a second test using the Hanna kit after your first failure?
Did it turn dark blue?


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Old 09/11/2019, 08:20 AM   #4
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Quote:
Originally Posted by mcgyvr View Post
And did you try a second test using the Hanna kit after your first failure?
Did it turn dark blue?
Yes, I tried a second test and a third one next day. I even switched test tubes, just in case they were contaminated.

Same result.


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Old 09/11/2019, 02:37 PM   #5
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Hmm, that sounds like bad reagents to me, or maybe the vials are contaminated. I might try cleaning them with a bit of vinegar, but I suspect that the reagents are bad.


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Old 09/11/2019, 02:57 PM   #6
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Quote:
Originally Posted by bertoni View Post
Hmm, that sounds like bad reagents to me, or maybe the vials are contaminated. I might try cleaning them with a bit of vinegar, but I suspect that the reagents are bad.
These are the same batch of reagents I used with "normal" results. I also cleaned the vials (RODI water only). I even used three different vials.


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Old 09/11/2019, 04:03 PM   #7
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Well, you could try testing some freshly-mixed saltwater. Maybe it's the tank, but then the Salifert must be wrong.


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Old 09/11/2019, 05:19 PM   #8
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Well, you could try testing some freshly-mixed saltwater. Maybe it's the tank, but then the Salifert must be wrong.
+1 do this ^

If it turned as blue as you say and the reagents are good you have unbelievably high po4.....I hope it's the reagents


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Old 09/12/2019, 07:10 AM   #9
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So I have been playing with the tester until I ran out of reagents.

Just mixing Red Sea salt in RODI does have some phosphate in it. I measured 0.073584 ppm.

But here is the weird stuff ... I tested the DT again and the blue color is nowhere to be seen. The results are back to normal - about 0.012264 ppm.

So the temporary issue is gone.

I do have one theory that I will verify when I get more reagents. I have two Hanna checkers, one for phosphates and the other one for copper. I mixed up all the vials and don't know which one I used with each tester. MAYBE the copper reagent traces react with the phosphorus reagent.


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Old 09/12/2019, 07:56 AM   #10
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I would suggest @ a minimum to clean all the vials with vinegar & rinse with RO water before drying.


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Old 09/12/2019, 08:03 PM   #11
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I agree with giving the vials a good cleaning. Vinegar is what I'd use.


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