Hanna Phosphorus Test Turning Navy Blue - help

jjencek · 09/11/2019, 01:37 AM

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?

jjencek · 09/11/2019, 05:16 AM

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.

mcgyvr · 09/11/2019, 07:55 AM

And did you try a second test using the Hanna kit after your first failure?
Did it turn dark blue?

jjencek · 09/11/2019, 08:20 AM

Quote:

Originally Posted by mcgyvr

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.

bertoni · 09/11/2019, 02:37 PM

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.

jjencek · 09/11/2019, 02:57 PM

Quote:

Originally Posted by bertoni

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.

bertoni · 09/11/2019, 04:03 PM

Well, you could try testing some freshly-mixed saltwater. Maybe it's the tank, but then the Salifert must be wrong.

outssider · 09/11/2019, 05:19 PM

Quote:

Originally Posted by bertoni

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

jjencek · 09/12/2019, 07:10 AM

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.

Vinny Kreyling · 09/12/2019, 07:56 AM

I would suggest @ a minimum to clean all the vials with vinegar & rinse with RO water before drying.

bertoni · 09/12/2019, 08:03 PM

I agree with giving the vials a good cleaning. Vinegar is what I'd use.

09/11/2019, 01:37 AM	#1
jjencek Registered Member Join Date: Dec 2016 Location: Prague, Czech Republic Posts: 366	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?

09/11/2019, 07:55 AM	#3
mcgyvr Registered Member Join Date: Sep 2003 Location: North Carolina Posts: 20,050	And did you try a second test using the Hanna kit after your first failure? Did it turn dark blue? __________________ Who me?

09/11/2019, 02:37 PM	#5
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	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. __________________ Jonathan Bertoni

09/11/2019, 04:03 PM	#7
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	Well, you could try testing some freshly-mixed saltwater. Maybe it's the tank, but then the Salifert must be wrong. __________________ Jonathan Bertoni

09/12/2019, 07:56 AM	#10
Vinny Kreyling Registered Member Join Date: Nov 2002 Location: Miller Place, NY Posts: 7,206	I would suggest @ a minimum to clean all the vials with vinegar & rinse with RO water before drying. __________________ 250 gallon mixed reef, 2 Reefbreeder's Photon V 2, Deepwater BLDC 12, DAS EX-3 Skimmer, MTC mini cal, 2-3/4" Sea Swirls, Aquacontroller & 6 Tunze pumps.

09/11/2019, 05:16 AM	#2
jjencek Registered Member Join Date: Dec 2016 Location: Prague, Czech Republic Posts: 366	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.

09/12/2019, 07:10 AM	#9
jjencek Registered Member Join Date: Dec 2016 Location: Prague, Czech Republic Posts: 366	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.

09/12/2019, 08:03 PM	#11
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	I agree with giving the vials a good cleaning. Vinegar is what I'd use. __________________ Jonathan Bertoni