PO4 test kits - Hanna VS Salifert

[Myka]

Originally Posted by GoFish

And with the Hanna I don't shake it for 2 minutes, instead for 1 minute until the powder is dissolved and then hold the button for the 3 minute timer. I make sure there's no air bubbles inside the vial and keep the vial facing the same direction (10ml facing forward) for both the calibration and test, then rinse the vial with RO (using a syringe that's only ever used for this purpose) and leave the cap off when put back in the case to let it dry for next time. I found with the standard PO4 Hanna checker I used to have that if I shook the sample for 2 minutes the checker would turn off, not sure if the current versions still have this 2 min/off feature

The ULR checker needs to be mixed for 2 minutes before starting the 3 minute countdown. It needs 5 minutes of development. The checker allows for this. I'd also suggest you do not shake the vial, but tilt it back and forth to mix because microbubbles in the vial will mess up the readings, so will fingerprints or water marks on the outside of the vial. Dried tap water inside the vial from your last rinse will often give you false high readings too.

Here's a very detailed description of how I perform the test:

I use a syringe to fill the vial with a couple mL of tank water, shake vigorously, then empty it and shake as much water out as possible. If there are drops left near the top of the vial I will use a bit of paper towel to get them. Then I add tank water to the 10 mL mark (bottom of the water's curve), cap it. I get the reagent packet ready (so it's quicker) by flicking all the powder down into one corner, then cut off two sides, and squish it open. I clean the outside of the vial with a microfiber cloth. Then I turn on the checker, wait for "C1". Insert the vial with the "10" on the vial lined up with a mark I put on the top of the checker, close lid, set the checker down. Hit the button. Wait for "C2". Add the reagent packet, cap the vial and gently tilt it side to side for 2 mins (I time it). Hold down the button on the checker until it starts the 3 min countdown. When there's about 1 min left, I turn the vial a few times, make sure there are no air bubble on the vial sides, clean the vial with the microfiber cloth again, and insert the vial into the checker, close the lid and wait for the reading (there's about 45 seconds remaining when I insert the vial). Once I get a reading I immediately take the vial to the sink and rinse it repeatedly with water that is as hot as I can stand, using my thumb to seal water inside it and shaking it vigorously. I also rinse the lid. Afterwards I rinse it in RO/DI water, and shake it out vigorously.