Hanna Phosphorus checker unreliable ?

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Ok so today tests are as follow only thing I changed was inverting the cuvette when mixing the reagent

1st test 28ppb sounds great right ? No
2nd test 91ppb
3rd test 93 ppb

So then I grabbed another vial that was full of rodi wiped down with a micro fibre cloth and retested the 3rd test vial which came out at 76ppb

lost completely here! new fresh vials come tomorrow hopefully this will solve the issues I’m having as my cuvette did come with some scratches straight from the box when new from Hanna
I’m guessing the po4 is is between 91 - 93ppb but the other readings concern me as the variance is so large
As stated my test procedure is the same each time as per instructions each time using a separate syringe for tank water and separate syringe for rinsing the cuvette with rodi
 
Zoanthids

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Ok so today tests are as follow only thing I changed was inverting the cuvette when mixing the reagent

1st test 28ppb sounds great right ? No
2nd test 91ppb
3rd test 93 ppb

So then I grabbed another vial that was full of rodi wiped down with a micro fibre cloth and retested the 3rd test vial which came out at 76ppb

lost completely here! new fresh vials come tomorrow hopefully this will solve the issues I’m having as my cuvette did come with some scratches straight from the box when new from Hanna
I’m guessing the po4 is is between 91 - 93ppb but the other readings concern me as the variance is so large
As stated my test procedure is the same each time as per instructions each time using a separate syringe for tank water and separate syringe for rinsing the cuvette with rodi
Just checking...you are doing each test from scratch? New reagents etc full 5 mins wait etc

A couple of others things I do, I never wash them with tap water always rodi water, store them with rodi water inside and out, I also read that some vials have the 10ml mark in the wrong place, so I weight the water, I don’t go by the line (mine is correct though but I still weigh as it’s easy to misjudge the amount by eye).
 
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Just checking...you are doing each test from scratch? New reagents etc full 5 mins wait etc

A couple of others things I do, I never wash them with tap water always rodi water, store them with rodi water inside and out, I also read that some vials have the 10ml mark in the wrong place, so I weight the water, I don’t go by the line (mine is correct though but I still weigh as it’s easy to misjudge the amount by eye).

Hello bud thanks for your reply yes full test from scratch each time I never wash with tap water always with rodi 0tds and I do store them with rodi water inside the cuvette But I don’t weigh the sample by weight I’m assuming you use standard digital kitchen scales to do so ? Also are you saying you store your cuvette fully submerged in ro water ?

thanks Dan
 
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attiland

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Just checking...you are doing each test from scratch? New reagents etc full 5 mins wait etc

A couple of others things I do, I never wash them with tap water always rodi water, store them with rodi water inside and out, I also read that some vials have the 10ml mark in the wrong place, so I weight the water, I don’t go by the line (mine is correct though but I still weigh as it’s easy to misjudge the amount by eye).
Wow never went this fare with testing. I mean measure the volume by grams is officially cheating. ;) I have a scale to measure with 0.01 accuracy so could technically do it.
I was always wondering about that line though. But the thing is if you make the same mistake constantly that difference becomes irrelevant since we are looking at trends here and the exact fugue is not that important.
on the other hand how do you tell now much rodi is in the vial?
 

attiland

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Hello bud thanks for your reply I never wash with tap water always with rodi 0tds and I do store them with rodi water inside the cuvette But I don’t weigh the sample by weight I’m assuming you use standard digital kitchen scales to do so ? Also are you saying you store your cuvette fully submerged in ro water ?

thanks Dan
That is not a kitchen scale for sure. If it would be that would not be accurate enough.
l use this. https://www.ebay.co.uk/itm/Digital-...-/373138462091?_trksid=p2349624.m46890.l49286
 

anthonygf

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44DF1622-AFA8-4CE1-A12C-D270286ADCB1.jpeg
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Test results 1 &
2, back to back, just to help the OP have confidence that this can be done.

(Note- the pH checker is new to me and I’m not sure I did the test correctly- it looks low? But it was repetitive +-0.1. I’m going to find the new directions that I seem to have lost, 4 drops?)
5 drops reagent for the ph.
 

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Hello bud thanks for your reply yes full test from scratch each time I never wash with tap water always with rodi 0tds and I do store them with rodi water inside the cuvette But I don’t weigh the sample by weight I’m assuming you use standard digital kitchen scales to do so ? Also are you saying you store your cuvette fully submerged in ro water ?

thanks Dan
I'd recommend that you follow the protocol I outlined yesterday. It will largely eliminate most variables and, if your readings are still all over the place, you are left with bad checker, bad reagents, bad battery, or sky high phosphate levels messing with test limits. (The very last can then be eliminated as a possibility by doing a 10:1 dilution.). If you do all this and are still getting bad results, I imagine Hanna will definitely refund your money or give you a new checker/reagents.
 

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Hello bud thanks for your reply yes full test from scratch each time I never wash with tap water always with rodi 0tds and I do store them with rodi water inside the cuvette But I don’t weigh the sample by weight I’m assuming you use standard digital kitchen scales to do so ? Also are you saying you store your cuvette fully submerged in ro water ?

thanks Dan

I use 0.01g scales from Amazon, cheap to buy, seems a bit extreme but after reading someone had an issue with the line being in the wrong place, I tried a syringe but that too wasn't very accurate either as the margins we are talking here are so small, I already had the scale for making a salinity solution so ended up using the scale, works great, trying to get the exact amount in the vial each time by eye isn't easy.

Yes 10ml is 10g.

I had read a few times of people storing their vials with rodi water, but to me that seemed pointless unless you also took care of the glass on the outside too so yes I also store the vial in a little tub of rodi water, the lid is ceramic or similar so is fine in the water.
 
Fritz

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Any tips for getting all of that powdered reagent out of the packet? I often feel like this is the biggest obstacle to reliable results.

easy, just bang the packet a couple of times, cut along the line, then push the two sealed sides together to form a spout, once you have a spout give the two folded sides a good pull to get the power out of the crease, pour into the vial followed by a last tap at the end.
 
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I use 0.01g scales from Amazon, cheap to buy, seems a bit extreme but after reading someone had an issue with the line being in the wrong place, I tried a syringe but that too wasn't very accurate either as the margins we are talking here are so small, I already had the scale for making a salinity solution so ended up using the scale, works great, trying to get the exact amount in the vial each time by eye isn't easy.

Yes 10ml is 10g.

I had read a few times of people storing their vials with rodi water, but to me that seemed pointless unless you also took care of the glass on the outside too so yes I also store the vial in a little tub of rodi water, the lid is ceramic or similar so is fine in the water.
Ok so I went to a head shop and got some 0.00 scales sure the guy didn’t believe I wanted them for my fish tank lol cost me £20 none the less I only had time to do one test last night which came out at 71ppb

returned home from work today and got a reading of 35ppb

ran a 2nd test came out at 70ppb which is dead close to yesterday’s. I’m starting to think I’ve got a defective pack of reagents. I’m going to run a 3rd test shortly and will see what we hit this time :/
 

Reef.

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Ok so I went to a head shop and got some 0.00 scales sure the guy didn’t believe I wanted them for my fish tank lol cost me £20 none the less I only had time to do one test last night which came out at 71ppb

returned home from work today and got a reading of 35ppb

ran a 2nd test came out at 70ppb which is dead close to yesterday’s. I’m starting to think I’ve got a defective pack of reagents. I’m going to run a 3rd test shortly and will see what we hit this time :/
Wow seems you have tried everything...I hate to suggest spending more money but Hanna do a po4 reference fluid tho it’s £22!!!
 
Zoanthids
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Wow seems you have tried everything...I hate to suggest spending more money but Hanna do a po4 reference fluid tho it’s £22!!!
The 3rd test came out at 18ppb so that’s 35,70,18 crazy stuff! I’m thinking I’m going to have to buy the reference fluid although I’ve got a new pack of Reagents and new vials I’ll run two or three tests tomorrow See if I get any consistent results then I’ve covered every variable i possibly can. If all fails reference fluid and hopefully a new checker from Hanna if it is indeed an defective checker considering the amount I’ve spent with them.

thank you for your help and support I’ll report back tomorrow finger crossed on a more positive outcome
 
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I’ve just ran some water from my rodi system and the water is no longer reading zero it’s reading between 1 - 2ppm as my TDS meter only runs in 1ppm increments I think perhaps this could be playing some part in the mad fluctuations from the checker. I’ve ordered all new filters for the rodi as the rodi supplies the water for ato and to clean the vials with I will cease testing until the filters have been changed or I’ll grab some deionised water for the time being till the filter replacements arrive
 
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Didn’t think the Hanna was designed to read non salt water?
No it isn’t but my thinking was if my rodi water is reading 2 TDS perhaps some of the phosphate is being sourced from the water as my ato is often on as I have a fan blowing across the tank to help keep the temp stable as we are in summer now which increases the amount of top off being added. Or I could be way off in my thinking. I got deionised water coming tomorrow so I guess we will see I plan to use my new packet of reagents and vials tomorrow also.

sorry I put ppm I meant TDS long day at work today
 
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