Hanna Phosphate ULR inconsistent

[coloradoreefer94]

I recently got a Hanna checker (Phosphate ULR) and have since been trying to use it instead of the salifert PO4 useless test kit. I followed all of the instructions, yet my results are not the same. I clean the cuvette out with tank water, wipe with a microfiber cloth after touching, and yet my results using the exact same vials and samples ranged from 0.16 all the way up to 0.23 - to me this is not accurate enough to get a true reading of what my phosphate levels are, considering I used the exact same samples and ran the test twice back to back and got a difference of 0.07

Anyone have a similar experience or any ideas what could be causing this? Maybe the tester is just bad? Also worth noting, the reagents don't seem consistent either. I did one test using the packets that came with the tester and got a reading of 0.4, and then another test immediately after with a batch of reagents I ordered online (pack of 25) and got a reading of 0.16 and 0.23.

 

[Shnetts]

I would defiantly reach out to hanna and get a replacement. Just to make sure tho, did you check the expiration date of the reagents?

 

[exnisstech]

Mine has been very consistent for several years but TBH I can't tell you the last time I ran two test of the same water back to back because I've never felt the need. I probably should once in a while but I'm not the type of person to look for problems unless there a particular reason to. I use a 10ml syringe because I've found the lines on the vials inconsistent. I never rinse in tank water only RO after each use. I test PO4 and NO3 on 5 tanks every Sunday and shaking 10 vials for 2 minutes each sucks ao I use a little magnetic stirrer. I also perform the complete test with a single vial not two.

 

[X-37B]

Mine is very repeatable so it's either the test method or the unit, imo. I can run back to back with different vials and they are close enough to call it good.
Hanna sells standards to determine if the unit is in tolerance.

 

[CHSUB]

I get consistent results. Never actually touch the cuvette and clean with Ro/di after use. However your readings are within the listed error range.

from 0.16 all the way up to 0.23

 

[Uncle99]

How did you mix and for how long?
Mines been great for years.

I’ve never rinsed my curvette before use, it’s cleaned after the last use, and dried.

 

[Randy Holmes-Farley Verified Community Expert]

IMO, that range (0.16 to 0.23 ppm) is not unreasonably large.

Would you do anything different with these two values? I wouldn’t. Both are fine, IMO.