Hanna Vs. Salifert Nitrate Accuracy

[GottaLottaDogs]

I am having huge discrepancies between my brand new Hanna HR Nitrate test and my Salifert Nitrate test. Both are very consistent...but which one is accurate??

Salifert was testing around 30ppm initially for 3 tests.

Hanna tested 7.8ppm a few days ago at the same time as Salifert. I bought different reagents just in case that was the issue, tested 7.0ppm with the other reagents.

I have been vinegar dosing + PNS Probio dosing for the past 2 weeks. I bought ANOTHER hanna tester in case that was the issue. Today Hanna tested 1.8ppm and Salifert tested 25ppm. So both show a drop of around 5ppm, which is great, but which do I trust?? I bought a Triton ICP test ignorantly thinking I would get Nitrate results from that. Turns out, they don't test for nitrate, so I'm stuck. I don't know what to do from here, since if Salifert is accurate, I'd like to keep vinegar dosing, but if Hanna is accurate, then I should probably stop ASAP. Has anyone else dealt with this?

 

[Niels V]

Salifert is always higher than my Hanna HR

 

[GottaLottaDogs]

Is it that much higher though? 20+ppm difference?

 

[Niels V]

+10 ppm on average. When NO3 is low the difference seems less than when NO3 is elevated.

 

[GottaLottaDogs]

+10 ppm on average. When NO3 is low the difference seems less than when NO3 is elevated.

Which one do you trust?

 

[Niels V]

I rather watch for the trends in stead of fixating on the number itself. If the number goes up I feed less, if the number goes down I feed more. Not after one measurement, more week by week. I do test every couple of day's at the same time of the day. The Hanna I can do a little more consistently do to the powder being pre-measured in stead of the scoop of the Salifert. The latter one is more economical.

 

[Big E]

I am having huge discrepancies between my brand new Hanna HR Nitrate test and my Salifert Nitrate test. Both are very consistent...but which one is accurate??

Salifert was testing around 30ppm initially for 3 tests.

Hanna tested 7.8ppm a few days ago at the same time as Salifert. I bought different reagents just in case that was the issue, tested 7.0ppm with the other reagents.

I have been vinegar dosing + PNS Probio dosing for the past 2 weeks. I bought ANOTHER hanna tester in case that was the issue. Today Hanna tested 1.8ppm and Salifert tested 25ppm. So both show a drop of around 5ppm, which is great, but which do I trust?? I bought a Triton ICP test ignorantly thinking I would get Nitrate results from that. Turns out, they don't test for nitrate, so I'm stuck. I don't know what to do from here, since if Salifert is accurate, I'd like to keep vinegar dosing, but if Hanna is accurate, then I should probably stop ASAP. Has anyone else dealt with this?

Are you sure you're reading the Salifert correctly? Are you reading from the side or top?

Also keep in mind the Hannah is +/- 2.0ppm accuracy so the lower the NO3 level I'd trust it less.

At high levels I read Salifert at 50.0 and the Hannah read 70.0
At low levels I read Hannah at 0 and Salifert at 1.0

Having said all that if you want accurate low numbers I found the Red Sea Pro kit is very good from 4.0 to zero. Accuracy is .125ppm

 

[GottaLottaDogs]

Are you sure you're reading the Salifert correctly? Are you reading from the side or top?

Also keep in mind the Hannah is +/- 2.0ppm accuracy so the lower the NO3 level I'd trust it less.

At high levels I read Salifert at 50.0 and the Hannah read 70.0
At low levels I read Hannah at 0 and Salifert at 1.0

Having said all that if you want accurate low numbers I found the Red Sea Pro kit is very good from 4.0 to zero. Accuracy is .125ppm

Yes I read it from the top always. It is just strange how there is such a large discrepancy between the two tests

 

[PatW]

It sounds as if both tests are reasonably precise. That is they give the same result given the same concentration of nitrate. And that is as much as one can ask of any test. And it does give you relative concentration, that is if the concentration is going up or down and if so by about how much. Also both tests serve as checks on each other given that their results predict each other. That way if one is off, the other serves as a check on it.

The big question is just what in the heck is the concentration? For that you need to make a standard. If you could make, say a 5 ppm concentration of nitrate, you can then use that to test your nitrate tests for accuracy. And if they are off, you can use the amount as a correction on the result you get. To make a standard, you need an accurate scale and some basic knowledge of chemistry.

To make a standard, if I recall correctly, you add up the atomic numbers of say your chemical say NaN03. Na has a weight of 11, N has a weight of 12, and O3 has a weight of 48. So the whole shebang has a weight of 61 of which Nitrate makes up 50 parts or (50/61) times 100 the proportion of nitrate. Say you want to make a 10 ppm solution of nitrate. You take a liter of water which weighs 1000 grams and add .01 grams of nitrate to get 10 ppm. If I have done the math right.

Or you can just say, heck, what I am getting is good enough.