Has anyone tested Nitrite using Mastertronic? / Nitrite and Nitrate interaction?

[MikeTheNewbie]

Hi, I haven't tested Nitrite since my tank cycled but someone suggested I should try it out.
Since the Mastertronic has a Nitrate Compensation feature where it tests for both Nitrite and Nitrate to provide a more accurate result I decided to give it a try.
The results were odd to me.
When I activated that feature I got 0.037 ppm Nitrite and 3.46 ppm Nitrate.
When I tested for Nitrate only (as I usually do), my result was 7.42ppm
My Hanna Nitrate HR checker reported 11.1 ppm but that is common, Mastertronic has historically reported lower than Hanna in my case.
Does the relation between nitrite and nitrate make any sense to you?
I don't understand how Nitrite and Nitrate interact when the Hanna checker tests for it but I kind of expected the values to add up somehow.
I hope @Randy Holmes-Farley can chime in and share if that makes sense chemically. Maybe I'm asking too much from hobby grade test kits?

 

[blaxsun]

I think if you combine the nitrite and nitrate results you get something close to just the nitrate test.

 

[MikeTheNewbie]

Yeah, that's what I was thinking too since both NO2 and NO3 have just one nitrogen atom but I really don't know how each of the tests works.

 

[ReefJonas]

Hi, I haven't tested Nitrite since my tank cycled but someone suggested I should try it out.
Since the Mastertronic has a Nitrate Compensation feature where it tests for both Nitrite and Nitrate to provide a more accurate result I decided to give it a try.
The results were odd to me.
When I activated that feature I got 0.037 ppm Nitrite and 3.46 ppm Nitrate.
When I tested for Nitrate only (as I usually do), my result was 7.42ppm
My Hanna Nitrate HR checker reported 11.1 ppm but that is common, Mastertronic has historically reported lower than Hanna in my case.
Does the relation between nitrite and nitrate make any sense to you?
I don't understand how Nitrite and Nitrate interact when the Hanna checker tests for it but I kind of expected the values to add up somehow.
I hope @Randy Holmes-Farley can chime in and share if that makes sense chemically. Maybe I'm asking too much from hobby grade test kits?

Hi. Here is the explanation.
a nitrate test actually test nitrite by first convert a portion of nitrate to nitrite. Therefore if you have some nitrite from start in tank (and you normaly have ) then that test will lead to a false high reading of nitrate. So actually all tests should include a nitrite test and then with a certain factor withdraw that from the nitrate value. Then you will get the 100% correct no3 value. Your example above make sense. The later with comp mode is the true no3 val. For the Hanna test I suspect it’s affected by nitrite quite much as you have quite much nitrite in your water.
Do you have the Red Sea pro test for nitrate ? That seems not be affected by concomitant nitrite so if you wants to make a comparison it’s better use that. We can say that a manual test with Red Sea pro is equal to a test in MT with comp mode on. Both are insensitive to no2. The good thing is also that you get the no2 val which is a very good parameter also in mature tanks.
Jonas

 

[paul01609]

I wouldnt go chasing numbers between each tester as long as the tank looks good and every thing is doing well just use the mastertronic to test the stank is stable.
you will end up driving yourself mad using different testers

 

[MikeTheNewbie]

Hi @ReefJonas thanks for the feedback.
I can understand that subtracting the NO2 will cause a lower NO3 measurement.
What confuses me is the proportion.
0.037 ppm N02 can't be equivalent to 3.96 ppm NO3
I wonder why would subtracting just 0.037ppm of NO2 from a 7.42ppm NO3 sample reduce the result by more than half to 3.46 ppm NO3.
I don't have a good feeling about that Nitrate compensation feature in Mastertronic. I agree with the logic but the math doesn't make sense to me.

 

[ReefJonas]

the proportion has nothing to do with that, NOT 100% of NO3 is converted to NO2, its just a small portion of the NO3 that is specific for the test, that converts to NO2. Different reagent brand has different amount of NO3 that is converted to NO2 before we do the No2 measurement. For Fauna marine the conversion rate is 100, that means that if you have a NO3 value that gives a colour that says 5 mg/l, then that colour is same as if you did a NO2 measurement in a water with 0.05 mg/l NO2. Some other tests have other conversion factors. Salifert for instance have 25, meaning that as an example 5 mg/l NO3 has same color as 0.2 mg/l NO2. So these factors is just how the test is designed.

Then you maybe ask, why just not let 100% of NO3 be reduced to NO2 and then take the measure of NO2?. Then we should get a smaller portion of the true NO2 as a contributor and could ignore that. Reason of that is that then we would have got too strong colors and make the measure ranges very odd. Because NO2 reagent is very sensitive and develop very much colour so already at a NO2 value of maybe 1 mg/l we are at the end of the colour development. So if 100% of NO3 should have been converted to No2 prior to the measurement of NO2, then the max value of NO3 to be able to measure would have been only 1.2 mg/l or something like that, and that we dont want. We want a range between 0.00-20 mg/l. Etc. So thats reason why these tests by purpose dont let 100% of NO3 convert to NO2 before we do the NO2 measurement.
Do you follow me?

All this is no issue, as MT take care of this math. But just remind if you dpo manual test, make sure you did a NO2 compensation manually and know the factor. Not all companies tell you, but Fauna Marine do.

So to finally summarize: COMP mode in MT ALWAYS just give you a more correct NO3 value.

You can try this as a proof ( I know you believe me just like to explain):

1) Take a sample of pure NO3 , and do a NO2 test on that water with FM reagent. You will get absolutely zero colour, meaning that the nitrite measurement is never a false high value. It can only just improve your NO3 measurement. No cross reaction at all. NO2 is one of the most reliable test that exists to honest.
2) Take a solution with both No3 and No2, from tank for instance. Do a manual test with red sea PRO that is designed in that way that the NO2 comp is sort of inbuilt. You will notice that that test resembles MT COMP test very much, but if you do a MT (FM) test with NO comp, you will get higher than the red sea pro kit.

A further example from my own tank today:
I did a Nitrate COMP in MT: 0.34 mg/ l
NO2 from MT was : 0.029 mg/
Red sea PRO manual: 0.25-0.5 mg/l

If I had did a NO3 with NO comp-mode it would have been: 3.24 mg/l. Thus false high due ti my quite high NO2.

So The true value is 0.34 mg/l and thats also what RED sea pro says (0.25-0.5 mg/l).


Jonas

 

[MikeTheNewbie]

Hey Jonas, thank you very much for taking the time to explain. I have some new FM reagents I'll try to follow your example.
Hanna and MT results have always differed, even without compensation. Maybe the Hanna result is much more sensitive. This is an interesting topic.
Thanks for the help.

 

[ReefJonas]

Hey Jonas, thank you very much for taking the time to explain. I have some new FM reagents I'll try to follow your example.
Hanna and MT results have always differed, even without compensation. Maybe the Hanna result is much more sensitive. This is an interesting topic.
Thanks for the help.

Yes because Hanna seems not take in count no2. But I can’t answer for Hanna maybe they have like the Red Sea pro manual a sort of inbuilt compensation..? Anyway. I advice you to use comp mode when using fauna Marin. One exception: if you do a test with a reference fluid of nitrate that ofcourse only contains no3 and nothing of no2, then do not use comp mode.
Here is a pdf how you can test MT if you have reference fluids.
/Jonas

 

[ReefJonas]

And here is

Hey Jonas, thank you very much for taking the time to explain. I have some new FM reagents I'll try to follow your example.
Hanna and MT results have always differed, even without compensation. Maybe the Hanna result is much more sensitive. This is an interesting topic.
Thanks for the help.

here is the comp instructions from FM
(That is inbuilt in MT)