Nitrite does not need to be zero to test Nitrate accurately

[Bamf Comics]

This is not the brand test kit I used but it looks an awful lot like the API, just higher priced. I was checking it out today when I saw a Q&A box that screamed to get a question since someone here is shovelling false info my experiences and their tech response disagrees with

 

[MuddyWaters]

I've never heard that you have to have 0 nitrite to test nitrate. But, then again, my having never heard it doesn't mean a whole lot LOL.

 

[Bamf Comics]

Someone made a fuss about it last week in another message. Never had a problem with AP kits going back to the early 90's, never seen a warning or disclaimer on any of their literature but in internet land it's random internet comment versus random internet comment so I figure lets just ask directly some company that's referenceable. No point in some reader trying to guess which commenter to believe when the manufacturer of a test can answer.

 

[gwand]

Nitrate test kits usually employ the cadmium dye method. The reagents first convert the available nitrate into nitrite. The nitrate then binds to a cadmium based dye. The binding of the dye is proportional to the nitrite concentration. Any nitrites that are around before the reagents are added will also bind the dye. So yes if your kit uses the cadmium dye method, you will get a false positive reading. The nitrate level will be falsely higher. This is how I measured nitrate in my laboratory.

 

[Bamf Comics]

And as stated, apparently this doesn't apply to Fritz and AP test kits. It also sounds stupid. If it was like that with the regular kits, then there would be no need to sell two kits. Just use bottle #2 by itself to test for Nitrite.

 

[MaloK]

Gwand sums it...

But if you do both test, for nitrite and nitrate...

If there is nitrite, Just subtract the nitrite results from the nitrate one and you have something that provide a more accurate estimate of the actual real nitrate concentration.

 

[Uberhoust]

If your nitrites are anywhere near the concentration of the nitrates then you have other issues. It influences the test but doesn't really matter. Put it a different way I personally wouldn't be concerned if the nitrates appeared higher because I would be changing the water anyways if I had elevate nitrites. @gwand thanks for the succinct explanation of the relationship between the two with nitrate tests using cadmium dyes. The one question is there are at least two tests for Nitrate and possibly more. The API test and the Fluval tests appear to use different dyes.

API

Fluval(Hagen), Does anyone know the difference. Having used both I found the API easier to read.

 

[gwand]

I do not know the difference between those two tests. But the API nitrate test kit does not cross react with nitrite. That’s good news.