Phosphate testing sucks, even with Hanna. :(

[kyley]

Hi All,
I used a Hanna "LR" Phosphate meter and had results vary, so I thought I'd get the Hanna Phosphate ULR (ultra low range) and hopefully have more accuracy. I'm shocked at the vastly different measurements I'm getting from repeated tests. Some so different that I can't tell if I need to try to raise phosphates or reduce them! Here are some examples from recent tests of different tanks. I use one vial with saltwater and one vial with the reagent mixed in so that I can run the text more than once. Sometimes I used a second reagent when the results are surprising. Here's what I've found:

30g Waterbox (bought this system and it had been neglected obviously):
1st reagent try showed: 0.29, 0.67, 0.67, 0.68 – a vastly different number the first time! Obviously very high though (and all within the effective range of the HI774).
2nd reagent try showed: 0.55, 0.69, 0.69 – more consistent, but still lower with the first test.

30g IM tank:
1st reagent: 0.07, 0.15, 0.14, 0.16, 0.13
2nd reagent: 0.02, 0.01, 0.00, 0.01 – 2nd reagent was done right after the first. The first test showed high to dangerously high Phosphate (indicating it needs to be lowered badly), but the second showed minimal to 0 Phosphate (indicating it should be raised)! How could it be so far off??

65g tank:
0.04, 0.01, 0.02: Only moderately different, but 0.04 and 0.01 tell me a very different story, and I don’t know what to believe.

120g tank:
0.05, 0.03, 0.04: Relatively consistent here
A week or so later:
1st reagent: 0.02, 0.09, 0.07, 0.09 – 1st test showed low (ideally should raise it), 2nd-4th showed too high (need to bring it down)! Which to believe??
2nd reagent (right after first): 0.04, 0.07, 0.05, 0.05 – relatively consistent this time, but still substantial variation between 1st and 2nd test (and looks like PO4 is right where I want it, while the previous test said I need to reduce it).

Are you all having the same experiences? All of my vials are brand new, scratch free, and are kept very clean (and filled with RODI between uses). The reagents expire in 2022, and the meter is brand new.

I can understand a small variance in testing, but 0.02 and 0.09, 0.07 and 0.15, 0.29 and 0.67 are just a few examples of readings that vary by more than the stated accuracy of +/-0.02 ppm. And those numbers tell very different stories. Thoughts? Thanks,
--Kyle

 

[GoVols]

I use one vial with saltwater and one vial with the reagent mixed in so that I can run the text more than once.

I just use one vial to do the entire ULR test, and line the vial up the same way inside the unit, for calibration and the final reagent test.

Hope that helps.

 

[AJsReef]

Glad I’m not the only one who has difficulty with the Hanna ULR. I actually switched to Red Sea PO4 Pro

 

[Dave Cureton]

I get pretty consistent readings from my HI736. Within the accuracy range anyway. Are the reagents you're using and getting different results from the same box/batch?

 

[ReefGeezer]

I use the ULR. I've found the precision is greatly effected by the condition of the vial. Scratches, etching, and water/reagent deposit biuld-up eventually makes the vials unusable. I use only one vial for the test, line it up the same way, and replace the vials regularly. Since I don't test for phosphate much, I also store the vials with RO/DI water in them to reduce the deposit build-up issues.

Pay attention to how you cut the reagent pouch open and ensure you are getting of the reagent in the vial. I cut the pouch on the dotted lines, create a trough, and tap the pouch to line up all the reagent in the trough. Just pretend you're back in the 80's!

 

[kyley]

I just use one vial to do the entire ULR test, and line the vial up the same way inside the unit, for calibration and the final reagent test.

Glad I’m not the only one who has difficulty with the Hanna ULR. I actually switched to Red Sea PO4 Pro

Are the reagents you're using and getting different results from the same box/batch?

Well, I posted that a week ago. I had previously used different (older) versions of the phosphate meter and didn't realize this one had a built in timer and instructions to shake for a full two minutes before starting that timer. I've only done one test since then, but with repeated runs of the test, I got consistent measurements within .01. So, some of this can be chalked up to user error of not waiting the full amount of time. But still, some of the previous tests I posted above are difficult to explain away with that error. At any rate, I will continue testing and see if I keep getting consistent results. Thanks,
--Kyle

 

[kyley]

I use the ULR. I've found the precision is greatly effected by the condition of the vial. Scratches, etching, and water/reagent deposit biuld-up eventually makes the vials unusable. I use only one vial for the test, line it up the same way, and replace the vials regularly. Since I don't test for phosphate much, I also store the vials with RO/DI water in them to reduce the deposit build-up issues.

Pay attention to how you cut the reagent pouch open and ensure you are getting of the reagent in the vial. I cut the pouch on the dotted lines, create a trough, and tap the pouch to line up all the reagent in the trough. Just pretend you're back in the 80's!

Thanks, all good advice. I am storing them with RODI inside, the vials are all new, and I'm careful about getting all the reagent out, pretty much just as you described. The timer part is something I hadn't been doing. Fingers crossed that I keep getting consistent results going forward. I didn't try with separate reagents yet (just retesting the same vial, but after the full 5 minutes had past - and not much more for the subsequent runs of the test)...
--Kyle

 

[AZMSGT]

Consistency is key to getting accurate results.
1. I clean the vial after every test.
2. I use a paper towel to get out all the moisture after cleaning.
3. Use only 1 vial for the entire test
4. fill vial with tank water to line, cap and wipe outside clean And use a micro fiber towel or lens cleaner.
5. pre cut and prep reagent package.
6. Press button with lid closed.
7. At c1 gently insert vial with the 10ml right above ppm try to keep bubbles to a minimum
8. after C1 is done remove vial add reagent, wipe exterior clean again, shake for two minutes.
9. insert vial clocked as in step 7.
10. Set on flat surface and press and hold button till timer starts.
11. take reading in three minutes

My prepped reagent.

 

[ReefGeezer]

Consistency is key to getting accurate results.
1. I clean the vial after every test.
2. I use a paper towel to get out all the moisture after cleaning.
3. Use only 1 vial for the entire test
4. fill vial with tank water to line, cap and wipe outside clean And use a micro fiber towel or lens cleaner.
5. pre cut and prep reagent package.
6. Press button with lid closed.
7. At c1 gently insert vial with the 10ml right above ppm try to keep bubbles to a minimum
8. after C1 is done remove vial add reagent, wipe exterior clean again, shake for two minutes.
9. insert vial clocked as in step 7.
10. Set on flat surface and press and hold button till timer starts.
11. take reading in three minutes

My prepped reagent.

Nice post. Pretty much my process also. Also I fill the vial until the top of water level is right at the top of the line. I don't think it matters much exactly where your fill line is. I think it does matter that it is the same every time.

 

[AZMSGT]

Nice post. Pretty much my process also. Also I fill the vial until the top of water level is right at the top of the line. I don't think it matters much exactly where your fill line is. I think it does matter that it is the same every time.

The angle of the photo makes it look higher. The water tension causes the edges to look high while the surface is right at the line.

 

[Paul.martin]

After testing I immediately rinse the vials with tap water, then I immerse the vials in vinegar, pour out vinegar, wait a few minutes, then rinse three times with RODI, then dry the vials. If I don’t use vinegar my vials will etch. I am using 713.

 

[Biff0rz]

I'll list my process and I get consistent results (+-.01) but it takes a couple of tools.

1x pipette that accurately measures 10ml
1x scalpel

Clean vial (including the inside, swap with paper towel) with microfiber cloth
Open reagent pack as someone showed above
Get a 10ml sample of water with the pipette and place in vial
Cap tight
Turn on tester w top closed
Holding the cap, insert vial with the 10ml mark facing fwd
When ready, add reagent - I drop most in then tap the back with my finger to get most out. I then tap it on the table again and try to get any out of the creases. Then I use the scalpel to pull out any little bits and get those in the vial.
Cap tight, mix for 2 mins in my cuvette mixer
Wipe down outside of vial w microfiber cloth
Place vial in tester w 10ml mark facing forward
Wait 3m in agony
(go do my Nitrate test)
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