Hanna Phosphrus Checker

[fishkeeprian]

Hello,

Does anyone else get really inaccurate results, even if you follow the instructions to the letter?

[hkgar]

How do you know they are inaccurate results?

[bertoni]

Some people have reported problems with this device. All testing equipment is subject to failure.

[fishkeeprian]

How do you know they are inaccurate results?

3 tests done one after the other 47ppb, 0 and 11.

[hkgar]

Thought I would post a pictures of 2 vials. I am cleaning them in vinegar and noticed this color difference that your can't see just by looking at the vial. I am sure the one with the yellow tint could effect readings. But I suppose that the computer is supposed to compensate for the differences.

https://photos.app.goo.gl/saVJ8ger9dB9vQqPA

[outssider]

I have noticed that vinegar doesn't work as good as straight muriatic acid...yellowing is going to through the readings way off

[Uncle99]

Hello,

Does anyone else get really inaccurate results, even if you follow the instructions to the letter?

Yup!
Stopped using it.
Like the CA tester, wide swings in ppm.

Replaced both with Salifert.

Now the ALK checker......excellent checker, fast too....

[bertoni]

3 tests done one after the other 47ppb, 0 and 11.
Well, I would hope for much better. You might contact the maker, and see whether the reagents are the issue.

[rayjay]

Mine is the Ultra low checker and I had inconsistent results until I started warming up the sample a bit. On checking the samples I eventually determined that the powder had not all dissolved, even though it appeared to be so. Checking under high light situation with a high powered glass used for nearly blind readers, I could see microscopic particles and postulated that those particles were affecting the reader. I couldn't improve the situation with more aggressive agitation so I started placing the some sample water in a container and let sit in a warm water bath to bring the temperature up to about 90° or so. Doing that has given me consistent repeatable results now as the warmer sample now dissolves that remaining powder.

[clevername]

id doubt its the reader thats not working. They sell the replacement glass test tubes. Id be going that route.

I personally cant imagine switching to another type of testing process. Hanna is so easy, so stable, so accurate.

[reefgeezer]

I was getting varying test results until I discovered that the clarity of the test vials is important. I now clean mine with RO/Di water and dry them inside and out with optical grade cloths. I replace them if the look hazed or scratched or when results start to vary. BRS sells the vials for cheap.

Fingerprints and other smudges that might get on the vials during the testing process also effect the results. I handle the vials with a cloth while testing.

You would think that the testing process would account for variances produced by the vial, but it doesn't... at least not completely.

[hkgar]

Sometimes it goes from c1 to c2 in just a couple seconds, other time it takes 30 seconds or more. Any ideas why?

[bertoni]

From the directions, it seems that the meter is testing the absorption of the saltwater itself before running the rest of the test. I am not sure why the time should vary, but maybe the meter takes a variable amount of time before settling. You could try asking Hanna.

[outssider]

Sometimes it goes from c1 to c2 in just a couple seconds, other time it takes 30 seconds or more. Any ideas why?

this happens all the time with me too....also happens with the alk meter...I don't know why but it seems just as accurate either way

[fishkeeprian]

Sometimes it goes from c1 to c2 in just a couple seconds, other time it takes 30 seconds or more. Any ideas why?

I've experienced this aswell.

[zachfishman]

Anything affecting A) the clarity of the vials will affect the result. At work we use kimwipes to clean the exterior of each vial before every single use and during handling (use the wipe to grab the vial and not bare hands).

We also use the same cuvette as C1 and C2 (take the C1 reading, add reagent, then start timer, mix for 2:30 of the 3:00 countdown, and then place vial back into the reader). We don't shake the vials but invert them back and forth allowing the bubble to do the mixing. Shaking the vials produces lots of microbubbles which tend to stick to the vial walls and (probably) introduce error by blocking/scattering the light.

I have no idea why the checker sometimes takes ages to get the first reading while other times it goes faster. My guess is that it is taking the average of several readings but keeps going or starts over if the variability is too great.

[hkgar]

The instructions seem to clearly indicate to start the 3:00 time after shaking (disolving) the reagent after the 2 minutes.

Remove the cuvette, open it and add the content of one packet of HI 736-25reagent. Replace the cap and shake gently for 2 minutes until the powder is completely dissolved. Replace the cuvette into the meter.

•Press and hold the button until the timer is displayed on the LCD.•The instrument directly displays the concentration of phosphorus in ppb. The meter automatically turns off after 2 minutes

[bertoni]

I have no idea why the checker sometimes takes ages to get the first reading while other times it goes faster. My guess is that it is taking the average of several readings but keeps going or starts over if the variability is too great.
That sounds like a better guess than mine. I suspect that the issue is getting a stable reading, in any case, but it'd be nice to know.

[Soryu]

Occasionally I find that user error is my biggest issue. Dirty equipment, incorrect sample sizes, ect. Generally speaking the only test I have real issues correlating to other test methods is the Hanna Calcium tester but that's because of the sample size. I've switched to a syringe instead of the 100µL pipette for that test.