Differences in nitrite sensitiveness in different nitrate measurement methods

[JonasRoman]

I know there is an existing old thread about this, but couldn't find now. Feel free to move my post to that, or we start a new one. Admin decide:-)

We all know that nitrate tests are based on converting nitrate completely or partially into nitrite, and then measuring the nitrite. This means that if you already have a significant amount of nitrite in the tank, this nitrite can produce a falsely high nitrate reading with your test method. How much it affects the result depends on how much the test method converts nitrate to nitrite before reading. This is an intentional design feature, as those who convert all nitrate into nitrite are almost not at all sensitive to nitrite levels, but results in a lower "roof". The higher the nitrite level is in the tank and the lower the nitrate level is, the more this influences the interpretation of the nitrate reading. I have created a table with the data I have personally derived along with information I found on the manufacturer's websites, including some own lab tests. etc. (The old thread I couldn't find now says approx the same but I have added a few more brands) See the PDF.

/Jonas Roman

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the info. :)

 

[JonasRoman]

Thanks for the info. :)

You are welcome:-). we can add other brands to the list:-)

 

[Dan_P]

I know there is an existing old thread about this, but couldn't find now. Feel free to move my post to that, or we start a new one. Admin decide:-)

We all know that nitrate tests are based on converting nitrate completely or partially into nitrite, and then measuring the nitrite. This means that if you already have a significant amount of nitrite in the tank, this nitrite can produce a falsely high nitrate reading with your test method. How much it affects the result depends on how much the test method converts nitrate to nitrite before reading. This is an intentional design feature, as those who convert all nitrate into nitrite are almost not at all sensitive to nitrite levels, but results in a lower "roof". The higher the nitrite level is in the tank and the lower the nitrate level is, the more this influences the interpretation of the nitrate reading. I have created a table with the data I have personally derived along with information I found on the manufacturer's websites, including some own lab tests. etc. (The old thread I couldn't find now says approx the same but I have added a few more brands) See the PDF.

/Jonas Roman

Did you run the nitrate tests with nitrite contamination to validate the estimate?

 

[JonasRoman]

Did you run the nitrate tests with nitrite contamination to validate the estimate?

Both Yes and no. Interesting question-:)
In what way does that effect the reduction ratio if nitrite already exists to some extent?

My method (besides those data that was available from manufacture etc) was that I took Ref fluid of nitrate and did the normal nitrate test and then measured nitrit. So for Hanna HR I had a ref fluid of 1.7 mg/l nitrate. (Odd numbers but I made my own base on Hach solutions and ultra pure marine water from ATI based). That solution reacted 7 min and I did a nitrit test in Hanna Checker (marine master ). It gave approx 0.1 mg/ nitrit. The numbers are approx as I now write from my memory. The weight factor is around 1.3 so its reasonable close to 10 % converting rate I suppose.

For Hanna Checker HR I actually did like you suggest a in vivo test aswell as the situation gave that, where we had a water with 1 ppm nitrit and 5 ppm nitrate. Hanna Checker gave 15 ppm nitrate in that situation and one of the 100% converting method gave 5.2 ppm in that sample ( little too low but within accuracy) So that was around same as I got in first test.

I started to test Hanna HR and also the MTE with a ref fluid of 10 ppm nitrate (only nitrate thus a pure Ref fluid based on marine water) where both gave 10 ppm ish (9.8 ppm and 10.2 ppm) so I know they where accurate.

Also I have recently sent Hanna a mail where I ask them for data of converting rate to validate. If they say something else I will redo otherwise just confirm.

Jonas

 

[gbroadbridge]

I know there is an existing old thread about this, but couldn't find now. Feel free to move my post to that, or we start a new one. Admin decide:-)

We all know that nitrate tests are based on converting nitrate completely or partially into nitrite, and then measuring the nitrite. This means that if you already have a significant amount of nitrite in the tank, this nitrite can produce a falsely high nitrate reading with your test method. How much it affects the result depends on how much the test method converts nitrate to nitrite before reading. This is an intentional design feature, as those who convert all nitrate into nitrite are almost not at all sensitive to nitrite levels, but results in a lower "roof". The higher the nitrite level is in the tank and the lower the nitrate level is, the more this influences the interpretation of the nitrate reading. I have created a table with the data I have personally derived along with information I found on the manufacturer's websites, including some own lab tests. etc. (The old thread I couldn't find now says approx the same but I have added a few more brands) See the PDF.

/Jonas Roman

That's very interesting - thanks.

 

[Dan_P]

Both Yes and no. Interesting question-:)
In what way does that effect the reduction ratio if nitrite already exists to some extent?

My method (besides those data that was available from manufacture etc) was that I took Ref fluid of nitrate and did the normal nitrate test and then measured nitrit. So for Hanna HR I had a ref fluid of 1.7 mg/l nitrate. (Odd numbers but I made my own base on Hach solutions and ultra pure marine water from ATI based). That solution reacted 7 min and I did a nitrit test in Hanna Checker (marine master ). It gave approx 0.1 mg/ nitrit. The numbers are approx as I now write from my memory. The weight factor is around 1.3 so its reasonable close to 10 % converting rate I suppose.

For Hanna Checker HR I actually did like you suggest a in vivo test aswell as the situation gave that, where we had a water with 1 ppm nitrit and 5 ppm nitrate. Hanna Checker gave 15 ppm nitrate in that situation and one of the 100% converting method gave 5.2 ppm in that sample ( little too low but within accuracy) So that was around same as I got in first test.

I started to test Hanna HR and also the MTE with a ref fluid of 10 ppm nitrate (only nitrate thus a pure Ref fluid based on marine water) where both gave 10 ppm ish (9.8 ppm and 10.2 ppm) so I know they where accurate.

Also I have recently sent Hanna a mail where I ask them for data of converting rate to validate. If they say something else I will redo otherwise just confirm.

Jonas

Nice work. Here is what I found some years back.

The reduction step when nitrate is reduced to nitrite also converts nitrite to ammonia. The amount of nitrite reduced depends on how much nitrate is in solution and the amount of nitrate reduced is affected by nitrite present. Because of this interaction there is no simple way to obtain an accurate estimate of nitrate. For hobby purposes, where accurate nitrate readings are necessary, the approach you are taking is good enough.

For accurate nitrate measurements in the presence of nitrite, nitrite is first destroyed with sulfamic acid.

 

[JonasRoman]

Nice work. Here is what I found some years back.

The reduction step when nitrate is reduced to nitrite also converts nitrite to ammonia. The amount of nitrite reduced depends on how much nitrate is in solution and the amount of nitrate reduced is affected by nitrite present. Because of this interaction there is no simple way to obtain an accurate estimate of nitrate. For hobby purposes, where accurate nitrate readings are necessary, the approach you are taking is good enough.

For accurate nitrate measurements in the presence of nitrite, nitrite is first destroyed with sulfamic acid.

Thanks, what an excellent addition of useful information. Appreciate
Jonas

 

[Christoph]

Nice data, thanks for posting it!
We did test the S*lif*rt Testkit in this regard several years ago:



All the best,
Christoph

 

[JonasRoman]

Nice data, thanks for posting it!
We did test the S*lif*rt Testkit in this regard several years ago:



All the best,
Christoph

Impressive and nice work:-)

 

[JonasRoman]

Nice data, thanks for posting it!
We did test the S*lif*rt Testkit in this regard several years ago:



All the best,
Christoph

You got even higher false nitrate than I got, multiply nitrit with *40 (I got *20). I guess this is reasonable the same, as I guess it may vary depending on other conditions. Nice work really:-)