Hanna ULR phosphate reading high the first time

[DVal]

Does anybody else have their Hanna ULR phosphate checker read high the first time? Everytime I check, I'll get something like .09 or .07, then I'll run the test a few more times and it'll be .01-.03. I always run it 3 or 4 times and average. Anybody else experience this?

 

[lapin]

You could order the standards just to double check to be sure the checker is working

 

[hds4216]

Mine doesn't do that.

 

[Spieg]

Nope, it's always pretty consistent for me.

 

[Dan_P]

Does anybody else have their Hanna ULR phosphate checker read high the first time? Everytime I check, I'll get something like .09 or .07, then I'll run the test a few more times and it'll be .01-.03. I always run it 3 or 4 times and average. Anybody else experience this?

Here is a way to check your Checker. You will need two vials.

Fill one vial with RODI. Then with the other vial, run the test like you normally do. Do not empty the test solution after the measurement. You are going to remeasure it.

Turn on the the Checker and insert the vial with RODI for the C1 step. Then for the C2 step, insert the above test solution and press the button but do not hold it in for the 3 minute countdown. Repeat this measurement until you get bored. Do this repeat measurement at least 3 times, 5,7,...times better. The solution color should be stable for at least ten minutes.

The numbers will not be the same but show variation within the 95% confidence interval of the device if it is working correctly. If you see a trend in the numbers like high, low, high, low, then maybe something is up.

Post your numbers if wish to discuss this further.

 

[DVal]

You could order the standards just to double check to be sure the checker is working

I believe I will do that. Im wondering if im not allowing the microbubbles to settle out before I run the first test. Its just odd that the first test with the same vial/solution is aleast double the subsequent tests are. The additional tests (all with the same solution) all are pretty consistent.

 

[DVal]

Here is a way to check your Checker. You will need two vials.

Fill one vial with RODI. Then with the other vial, run the test like you normally do. Do not empty the test solution after the measurement. You are going to remeasure it.

Turn on the the Checker and insert the vial with RODI for the C1 step. Then for the C2 step, insert the above test solution and press the button but do not hold it in for the 3 minute countdown. Repeat this measurement until you get bored. Do this repeat measurement at least 3 times, 5,7,...times better. The solution color should be stable for at least ten minutes.

The numbers will not be the same but show variation within the 95% confidence interval of the device if it is working correctly. If you see a trend in the numbers like high, low, high, low, then maybe something is up.

Post your numbers if wish to discuss this further.

I'll check that out. Thanks for the input

 

[Steve Erekson]

Do you clean your vials with anything between uses? I've found tiny amounts of vinegar causes the reading to be high.

 

[DVal]

Do you clean your vials with anything between uses? I've found tiny amounts of vinegar causes the reading to be high.

I just rinse them out after each use with regular water.

 

[schuby]

Can you list out all the steps, with any wait-time, you perform when testing phosphate with Hanna checker? Also, what model number is your checker?

 

[DVal]

Can you list out all the steps, with any wait-time, you perform when testing phosphate with Hanna checker? Also, what model number is your checker?

Sure thing. Its the HI774 ULR checker. I fill both vials with the 10ml of tank water and one I add the reagent. Shake for 2 minutes until reagent is dissolved. I then add C1 (normal tank water) then I add C2 and hold the button to start the 3min count. Once that is read, i dont empty the vials but run them through the test again. Its right away, so I'd imagine the reagent is still good at that point. The first reading is consistently higher (under .1 though). The second test will drop down to .01-.03 typically. What is funny is that any subsequent tests with those same vials will be consistent with the lower reading. Ill run through the test 3 or 4 times and then average the readings.

Do you think that the testing vial is no longer good after that first test and that's why I'm getting lower readings OR could it be because I have microbubbles or undissolved reagent causing the higher initial reading? I do look it over to make sure it is dissolved and there are no bubbles clinging to the glass though.

 

[schuby]

Here's some extra things I do. Maybe they'll help.

• When mixing for phosphate test, shake vigorously for 2 minutes
  • Not high speed but forceful
• Before putting a vial in checker
  • Tilt and roll vial so that "big bubble" knocks off any stubborn bubbles stuck to sides
  • Tap it several times against my knuckle to dislodge bubbles still stuck to sides
  • Clean fingerprints off using dry McDonald's napkin, using a different section each time
    • Squeeze napkin on two-sides of vial with one hand, turn vial in circles with other hand while moving napkin top-to-bottom then bottom-to-top
• When done testing
  • Rinse vials and caps 3-times using tap-water (fill completely with water then dump)
  • Rinse 1-time using RO/DI
  • Let dry upside-down on paper-towel for at least a day

 

[Rubberfrog]

Here's some extra things I do. Maybe they'll help.

• When mixing for phosphate test, shake vigorously for 2 minutes
  • Not high speed but forceful
• Before putting a vial in checker
  • Tilt and roll vial so that "big bubble" knocks off any stubborn bubbles stuck to sides
  • Tap it several times against my knuckle to dislodge bubbles still stuck to sides
  • Clean fingerprints off using dry McDonald's napkin, using a different section each time
    • Squeeze napkin on two-sides of vial with one hand, turn vial in circles with other hand while moving napkin top-to-bottom then bottom-to-top
• When done testing
  • Rinse vials and caps 3-times using tap-water (fill completely with water then dump)
  • Rinse 1-time using RO/DI
  • Let dry upside-down on paper-towel for at least a day

Would it be ok to use a taco bell napkin?

 

[DVal]

I tested again last night. The first reading i got was .06 then .01,.01,.00.
I rinsed and ran the same exact process again EXCEPT I waited 1 minute after mixing it to test. This time I got .05, then .02, .02, .01.

Its funny because both sequences are pretty consistent. Im starting to think the most accurate may be the first reading of each sequence (.06/.05) and the mix is degrading that fast. What are you guys thoughts? Could just be my checker. I did order some standard to test it out.

 

[Randy Holmes-Farley Verified Community Expert]

I believe I will do that. Im wondering if im not allowing the microbubbles to settle out before I run the first test. Its just odd that the first test with the same vial/solution is aleast double the subsequent tests are. The additional tests (all with the same solution) all are pretty consistent.

FWIW, the Hanna "standards" will not do nothing except verify the electronics. They do nothing to verify the reagents, cuvettes, or method procedures.

 

[DVal]

FWIW, the Hanna "standards" will not do nothing except verify the electronics. They do nothing to verify the reagents, cuvettes, or method procedures.

Oh yeah, I basically just want to see if I'm getting consistent readings with a known measure.

 

[LeftyReefer]

Sure thing. Its the HI774 ULR checker. I fill both vials with the 10ml of tank water and one I add the reagent. Shake for 2 minutes until reagent is dissolved. I then add C1 (normal tank water) then I add C2 and hold the button to start the 3min count. Once that is read, i dont empty the vials but run them through the test again. Its right away, so I'd imagine the reagent is still good at that point. The first reading is consistently higher (under .1 though). The second test will drop down to .01-.03 typically. What is funny is that any subsequent tests with those same vials will be consistent with the lower reading. Ill run through the test 3 or 4 times and then average the readings.

Do you think that the testing vial is no longer good after that first test and that's why I'm getting lower readings OR could it be because I have microbubbles or undissolved reagent causing the higher initial reading? I do look it over to make sure it is dissolved and there are no bubbles clinging to the glass though.

I think part of the issue may be the simple fact that you aren't following the manufacturer's directions.
You aren't supposed to be using two different vials for the test. Any difference in clarity between the two vials is going to skew the results. Not to mention Hanna vials are known to have different fill to lines. I know mine do....

you should be running this test with a single vial, and you should be indexing it when inserting it into the checker, so that the checker is looking at the same spot in the same vial for both parts of the test.

I bet if you actually run the test as intended, back to back to back, the results would be more consistent.

 

[DVal]

I think part of the issue may be the simple fact that you aren't following the manufacturer's directions.
You aren't supposed to be using two different vials for the test. Any difference in clarity between the two vials is going to skew the results. Not to mention Hanna vials are known to have different fill to lines. I know mine do....

you should be running this test with a single vial, and you should be indexing it when inserting it into the checker, so that the checker is looking at the same spot in the same vial for both parts of the test.

I bet if you actually run the test as intended, back to back to back, the results would be more consistent.

You're probably right. Didnt think it would've made that big of a difference.

 

[schuby]

Here's a basic question. From the time you dump the reagent in the vial, does 5 full minutes pass before the checker performs its reading?

 

[DVal]

Here's a basic question. From the time you dump the reagent in the vial, does 5 full minutes pass before the checker performs its reading?

Yes. It gets dumped in...2 min shaking to mix..then 3 min countdown.