Variability in Hanna ULR phosphate checker

[BleepBloopMunchMunch]

I’ve been using this to test my phosphate for about a month now, it came with two cuvettes but I noticed that sometimes in between measurements with one curettes or even more so when I tried to test twice in a row I get differently results outside of the margin of error. Today’s results were 0.13 and 0.09, last week I had an even bigger range of 0.15 and 0.06. The curettes aren’t super scratched or anything, I bought the kit new maybe a month ago or so and follow the protocol pretty precisely. I guess I’m just not sure which test to believe or if I should just be buying new cuvettes and trying again

 

[Srt4eric]

I’ve been using this to test my phosphate for about a month now, it came with two cuvettes but I noticed that sometimes in between measurements with one curettes or even more so when I tried to test twice in a row I get differently results outside of the margin of error. Today’s results were 0.13 and 0.09, last week I had an even bigger range of 0.15 and 0.06. The curettes aren’t super scratched or anything, I bought the kit new maybe a month ago or so and follow the protocol pretty precisely. I guess I’m just not sure which test to believe or if I should just be buying new cuvettes and trying again

I know fingerprints on the glass can make a pretty big impact on this one.

 

[MonkeyReefer]

Do you use a 10ml syringe or just fill it to the mark on the bottles? I’ve been using a 10ml syringe and my numbers have been consistent when I had to retest a few times using different bottles.

 

[BleepBloopMunchMunch]

I only have a 5 ml syringe, so I just use that twice to fill it to the line, but notes on the difference, I will try and see how that affects my readings

 

[Rostato]

I have the testing standards you could check the accuracy with. Maybe meet at AC one day.

Also, make sure your batteries are fully charged. They are a bit inaccurate when the battery starts to get low.

 

[BleepBloopMunchMunch]

I have the testing standards you could check the accuracy with. Maybe meet at AC one day.

Also, make sure your batteries are fully charged. They are a bit inaccurate when the battery starts to get low.

this would be very helpful, if you happen to go up that way let me know, I don't like too far away from them. Also noted on the battery, I am just using the one it came with so I will replace that

 

[Rostato]

this would be very helpful, if you happen to go up that way let me know, I don't like too far away from them. Also noted on the battery, I am just using the one it came with so I will replace that

I may head there tomorrow or Sunday. Not sure yet. But I need a refill of my RN Oyster Feast

 

[Coral reefer]

Are you testing the same sample multiple times? The timing matters. The longer it sits the lower the reading gets I think

 

[The_Lazy_Reefer]

When I’m in a mood to really care about my po4 I usually do 3 tests back to back and indeed all 3 are usually different so you are not alone. If a test comes back weird I do 3 in a row and average them to get a ballpark. I have had a few way out of the ballpark tests but I usually account user error for those as when I focus on the next 2 tests more the range is back within normal.

 

[BleepBloopMunchMunch]

Are you testing the same sample multiple times? The timing matters. The longer it sits the lower the reading gets I think

I am testing the same sample multiple times, the water does sit at last 5-10 minutes between samples, I will try it again with two fresh samples.

When I’m in a mood to really care about my po4 I usually do 3 tests back to back and indeed all 3 are usually different so you are not alone. If a test comes back weird I do 3 in a row and average them to get a ballpark. I have had a few way out of the ballpark tests but I usually account user error for those as when I focus on the next 2 tests more the range is back within normal.

I have been averaging the couple tests I do, but I will try doing three in a row all with fresh samples and see what comes up

 

[max_nano]

I’ve seen people suggest always putting the vial in the same way. An easy way is to line the 10ml up with the hinge.

 

[JVU]

For accuracy and reproducibility:

1) The cuvette needs to be completely clean of fingerprints, dried saltwater, anything. I use a small dry microfiber cloth square like comes with sunglasses to wipe it down after I add water (with the outside already completely dry first) and before zeroing. I just leave it in the kit box for use.
2) Use the same cuvette for the zeroing and the sample (even though they give you 2).
3) Don’t touch the sides of the cuvette at all in between zeroing, shaking, and putting back in the reader.
4) Use a syringe to measure out the 10 mL. Adding to the line on the cuvette makes it harder to keep the sides perfectly clean, and also isn’t accurate (10 mL is slightly above the line).
5) Make sure there are NO tiny bubbles on the sides of the cuvette for the zeroing or the reading. This is the most important step.
6) Put the cuvette in the same way every time. I use writing on the front as the marker.
7) For all 3 button presses and the final reading make sure the reader is in sitting the same area with the same background lighting, in case any outside light gets in (ie don’t turn on a bright light at the end when it is doing the final reading; after the results are displayed is fine of course).

This all may sound a bit nuts but it’s what I do now out of habit and doesn’t seem like an inconvenience once you get to used to it.

 

[borker]

For accuracy and reproducibility:

1) The cuvette needs to be completely clean of fingerprints, dried saltwater, anything. I use a small dry microfiber cloth square like comes with sunglasses to wipe it down after I add water (with the outside already completely dry first) and before zeroing. I just leave it in the kit box for use.
2) Use the same cuvette for the zeroing and the sample (even though they give you 2).
3) Don’t touch the sides of the cuvette at all in between zeroing, shaking, and putting back in the reader.
4) Use a syringe to measure out the 10 mL. Adding to the line on the cuvette makes it harder to keep the sides perfectly clean, and also isn’t accurate (10 mL is slightly above the line).
5) Make sure there are NO tiny bubbles on the sides of the cuvette for the zeroing or the reading. This is the most important step.
6) Put the cuvette in the same way every time. I use writing on the front as the marker.
7) For all 3 button presses and the final reading make sure the reader is in sitting the same area with the same background lighting, in case any outside light gets in (ie don’t turn on a bright light at the end when it is doing the final reading; after the results are displayed is fine of course).

This all may sound a bit nuts but it’s what I do now out of habit and doesn’t seem like an inconvenience once you get to used to it.

Where do you put the plunger exactly on the included 10ml syringe?

Also - for the alk checker same question with the 1ml plunger?

I find these syringes tricky since as you mentioned the line on the actual test is misleading.

Is there a YouTube video with someone doing this the ‘proper’ way? They always miss the syringe parts in the videos I’ve seen.


Sent from my iPhone using Tapatalk

 

[MonkeyReefer]

Supposed to read this way in the photo

 

[borker]

Supposed to read this way in the photo View attachment 22806

For both the small and large syringe? The small one doesn’t have a point.


Sent from my iPhone using Tapatalk

 

[MonkeyReefer]

yep point or no point same way

 

[JVU]

I agree the correct way is what’s shown in the pic @MonkeyReefer gave, you go by where the bottommost edge of the rubber plunger meets the side of the syringe. The pointy tip or lack thereof on the plunger is irrelevant- just a function of conforming to the shape of the bottom on the syringe. If the bottom is flat like most 1 mL syringes then it’s flat, if the bottom is pointy it’s pointy.