Hanna Phosphorus checker unreliable ?
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PeterC99
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When was the last time you changed the battery?
Those numbers are all fairly high.
Is this the ULR Phosphorus HI736? It works really well, in my experience, in lower phosphorus/phosphate ranges. I see the BRS page says the range is up to 200 ppb, but really this checker is for those keeping P closer to natural seawater parameters.
What numbers are you shooting for?
Apollo7235
Well-Known Member
Can you please post a photo of the checker you’re using?
I think Hanna makes freshwater versions of these checkers, so I’m not sure if you can use them for marine tests.
All of my checkers say ‘marine’ on them aside from my copper checker.
I think Hanna makes freshwater versions of these checkers, so I’m not sure if you can use them for marine tests.
All of my checkers say ‘marine’ on them aside from my copper checker.
schuby
Valuable Member
The bubbles being talked about are in the vial. I tap and roll mine to get all the micro-bubbles off the sides of the vial: each time (twice) before putting the vial in checker. I also wipe the outside of the vial with microfiber or a lint-free towel each time (twice), after getting rid of bubbles and before putting in checker.
BostonReefer300
Valuable Member
Sorry for your troubles. Here is the method I posted last week helping another member test the precision of his Hanna checker:
- Prepare two vials. One just with tank water for your "blank". Use other for the "sample" (tank water and the reagent).
- Mix the latter thoroughly for a couple minutes, wipe it down thoroughly with a microfiber cloth or a tissue damp with RODI water then dry it, make sure there aren't air bubbles inside (if so, gently swirl), then let it sit for 3 minutes.
- Now do multiple tests. Power up the tester. Put the blank vial (also cleaned carefully) in when it says C1. Make sure the tester lid is closed tightly. Press the button to zero the tester.
- When it says C2, remove the blank and replace with the sample. Press the button once. Don't hold it which will set the timer for 3 minutes---the sample has already sat for three minutes. This will give you a reading.
- Cycle the power on the tester and repeat the blank zeroing and sample measurement again.
- Then do it a third time.
- You should have very similar if not exactly the same results from all three tests. If you're doing the three tests in quick succession, the longer time the sample vial has sat between measurements shouldn't matter much (as long as you shook the vial for 2 minutes and then let sit for 3 minutes at the beginning).
- The above method isn't meant to replace the standard testing protocol. Instead, it's meant to gauge the precision of the checker as it eliminates most of the variability that could be attributed to user error.
[BTW, in my experience, you don't need to align the test vial the same way in the checker every time. Also, once you clean the vials, try to only touch them by the cap to avoid smudges on the glass.]
Regardless of the precision (consistency) issues you're having, those readings on an HI736 are quite high. For instance, a 100 ppm reading on that checker would correspond to 0.307 ppm PO4 which most would consider an above optimal level. The upper range for HI736 is 200 ppm Phosphorus. If human error is ruled out, my guess is that your PO4 levels are sky high and that you're running into problems with either upper detection limit of the device or the reaction capacity of the test reagent (or both). There could also be lots of particulates screwing up the readings. You could also have a bad battery, bad unit, or bad reagents. (Regarding the last, you definitely were sent the right reagents for the HI736 right?)
- Prepare two vials. One just with tank water for your "blank". Use other for the "sample" (tank water and the reagent).
- Mix the latter thoroughly for a couple minutes, wipe it down thoroughly with a microfiber cloth or a tissue damp with RODI water then dry it, make sure there aren't air bubbles inside (if so, gently swirl), then let it sit for 3 minutes.
- Now do multiple tests. Power up the tester. Put the blank vial (also cleaned carefully) in when it says C1. Make sure the tester lid is closed tightly. Press the button to zero the tester.
- When it says C2, remove the blank and replace with the sample. Press the button once. Don't hold it which will set the timer for 3 minutes---the sample has already sat for three minutes. This will give you a reading.
- Cycle the power on the tester and repeat the blank zeroing and sample measurement again.
- Then do it a third time.
- You should have very similar if not exactly the same results from all three tests. If you're doing the three tests in quick succession, the longer time the sample vial has sat between measurements shouldn't matter much (as long as you shook the vial for 2 minutes and then let sit for 3 minutes at the beginning).
- The above method isn't meant to replace the standard testing protocol. Instead, it's meant to gauge the precision of the checker as it eliminates most of the variability that could be attributed to user error.
[BTW, in my experience, you don't need to align the test vial the same way in the checker every time. Also, once you clean the vials, try to only touch them by the cap to avoid smudges on the glass.]
Regardless of the precision (consistency) issues you're having, those readings on an HI736 are quite high. For instance, a 100 ppm reading on that checker would correspond to 0.307 ppm PO4 which most would consider an above optimal level. The upper range for HI736 is 200 ppm Phosphorus. If human error is ruled out, my guess is that your PO4 levels are sky high and that you're running into problems with either upper detection limit of the device or the reaction capacity of the test reagent (or both). There could also be lots of particulates screwing up the readings. You could also have a bad battery, bad unit, or bad reagents. (Regarding the last, you definitely were sent the right reagents for the HI736 right?)
schuby
Valuable Member
I take a small cup of sample water from DT, let it sit for a few minutes, rinse syringe several times with sample water, and then fill vial using syringe. After testing, I always rinse vial 3 times with tap and then once with RO/DI.
When you say you follow the procedure to a tee, could you list out all the steps, from taking the checker out of the box to putting it back in? You may be perfect or you may be doing something different than some of us.
When you say you follow the procedure to a tee, could you list out all the steps, from taking the checker out of the box to putting it back in? You may be perfect or you may be doing something different than some of us.
Apollo7235
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Have you ever run two tests of the aquarium water, one right after the other?...sorry, yes you have
Also, if you have another Hanna vial, you can fill with RODI or aquarium water and use it as a blank. Then you can measure the same test sample over and over again to determine if the Checker is drifting.
OP
OP
DE FISH
Valuable Member
I’ll give that a go tonight
Got new vials coming tomorrow will try this alsoHave you ever run two tests of the aquarium water, one right after the other?...sorry, yes you have
Also, if you have another Hanna vial, you can fill with RODI or aquarium water and use it as a blank. Then you can measure the same test sample over and over again to determine if the Checker is drifting.
I wouldn't be afraid to use them in this case.
152ppb
121ppb
59ppb
89ppb
89ppb
60ppb
The lowest value is a little under 0.2 ppm. The standard deviation is huge, sure, but that doesn't mean your values aren't really high. And if you throw out the highest 152 reading (I would), the average is still about 84 ppb (0.26 ppm). And you got that reading twice, in the 89 ppb results.
Do you have a fish store that could test your water for phosphate? If P is that high, it would show up well on a Salifert kit.
On the other hand, if you aren't having problems then it's okay if you don't want to mess with it.
Good luck.
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