Hanna low range nitrate accuracy, nitrite interference

[Dan_P]

Is this really true?

For the salifert - see this

https://en.oceamo.com/post/tröpfchentests-nitrat-nitrit

Sincerely Lasse

Oceamo did not perform the correct experiment. Their experiment likely does not provide the correct conversion factor and likely exaggerates the nitrite effect, but we need to know the reducing agent in the Salifert test to know for sure.

If the Salifert reducing agent does not reduce nitrite and does a poor job reducing nitrate, the conversion factor could be high.

Let’s try to find their reducing agent.

 

[Lasse]

Oceamo did not perform the correct experiment. Their experiment likely does not provide the correct conversion factor and likely exaggerates the nitrite effect, but we need to know the reducing agent in the Salifert test to know for sure.

If the Salifert reducing agent does not reduce nitrite and does a poor job reducing nitrate, the conversion factor could be high.

Let’s try to find their reducing agent.

What do you say about this @Christoph IMO - Oceamo´s test is done in the right way

Sincerely Lasse

 

[Lasse]

Oceamos test show the conversion factor for nitrite interference in a real tests for this brand that they use. And that is this interference conversions factor that is interesting for me as an aquarist. I want to know how much - let us say - 0.05 in nitrite affect my readings of nitrate. In this case - it will clearly give a nitrate reading thats around 2 mg to high. The 0.1 mg/L NO2 give a false reading of 5 mg/L NO3. As they say in their text .

Why nitrate tests react to nitrite (only for chemistry freaks)?: Nitrate is difficult to measure "directly", so the test sets make a detour: The nitrate is (partially) converted to nitrite (reduced). The nitrite then forms a diazonium salt in an acidic environment, which undergoes an azo coupling with a suitable coupling partner. This creates an azo dye that causes the pink color. Existing nitrite can thus react immediately to the azo dye and simulates a higher nitrate value.

The conversion of nitrate is time depended - therefore is the conversion factor for nitrite interference depended on how much nitrate that is converted into nitrite after the recommended waiting time. If it is around 1 % - the nitrite interference conversion factor will be around 100 and if it is around 2 % - the nitrite interference conversion factor is around 50

What type of conversion factor you use - I do not know but it is clearly not the nitrite interference conversion factor To know the theoretical nitrate to nitrite conversion factor for the method is of low interest for us aquarists - we want to know the nitrite interference conversion factor for the method. We need a test like Oceamos but with Hanna low nitrate checker in use instead for the brand they use in their video.

Sincerely Lasse

 

[Christoph]

Hello everyone!

We are measuring nitrite and nitrate using our ion chromatography (with conductivity and UV/VIS detection). This way the analytes are measured independent from each other - so there is no interference of nitrite in our nitrate measurements.

Best regards,
Christoph

 

[Lasse]

@Christoph Dan_p critical statement is about the test you have done at your homepage of a well known brand of droplet nitrate test He says that it is not proper done in order to show that this test have a nitrite interference conversion factor around 30 - 50.

Sincerely Lasse

 

[Dan_P]

Oceamos test show the conversion factor for nitrite interference in a real tests for this brand that they use. And that is this interference conversions factor that is interesting for me as an aquarist. I want to know how much - let us say - 0.05 in nitrite affect my readings of nitrate. In this case - it will clearly give a nitrate reading thats around 2 mg to high. The 0.1 mg/L NO2 give a false reading of 5 mg/L NO3. As they say in their text .


The conversion of nitrate is time depended - therefore is the conversion factor for nitrite interference depended on how much nitrate that is converted into nitrite after the recommended waiting time. If it is around 1 % - the nitrite interference conversion factor will be around 100 and if it is around 2 % - the nitrite interference conversion factor is around 50

What type of conversion factor you use - I do not know but it is clearly not the nitrite interference conversion factor To know the theoretical nitrate to nitrite conversion factor for the method is of low interest for us aquarists - we want to know the nitrite interference conversion factor for the method. We need a test like Oceamos but with Hanna low nitrate checker in use instead for the brand they use in their video.

Sincerely Lasse

Unfortunately, Oceamos’s experiment was incorrectly designed because of the bad assumption that test color intensity with nitrite alone informs us about test color intensity of nitrite + nitrate. You cannot know the conversion factor until the proper experiment is done. The 100:1 conversion factor might be close but it is also likely to be inaccurate.

 

[Lasse]

You read the test colour intensity and compare with the chart. Of cause their reading is right and they also did experiments with both nitrite and nitrate in the test vial - the same result - my bold

We used standard solutions for nitrate and nitrite as well as a commercially available, frequently used nitrate test kit. Different samples were prepared, containing only nitrite (0.05, 0.1, 1 mg/l) or only nitrate (2, 5, 10 mg/l), as well as a mixed sample with nitrite and nitrate.

Compare the colour for nitrate only (blue) and the combined NO2/NO3 (red)

If you should argue - please control what you are talking about before you just dismiss other persons work

The 100:1 conversion factor might be close but it is also likely to be inaccurate.

Not even here you show any accuracy in you argumentation - they are talking about a conversion factor up to 50 (as I stated before) - not 100:1

Tropic Marin Pro test have a nitrite interference conversion factor around 100. - please see their conversion table below. There is some companies that are honest with their methods - and some that are not.

Sincerely Lasse

 

[Dan_P]

You read the test colour intensity and compare with the chart. Of cause their reading is right and they also did experiments with both nitrite and nitrate in the test vial - the same result - my bold

Compare the colour for nitrate only (blue) and the combined NO2/NO3 (red)

If you should argue - please control what you are talking about before you just dismiss other persons work


Not even here you show any accuracy in you argumentation - they are talking about a conversion factor up to 50 (as I stated before) - not 100:1

Tropic Marin Pro test have a nitrite interference conversion factor around 100. - please see their conversion table below. There is some companies that are honest with their methods - and some that are not.

Sincerely Lasse

Hi Lasse,

I had to laugh when you posted the nitrate correction table. This is exactly the data I measured for Red Sea and Hanna Marine nitrate kits, only I plotted the data as graphs instead of putting the numbers in a table. Oh well, right?

There is a potential issue with the table you posted. The differences between the numbers are too perfect, in both dimensions of the table. When numbers are this consistent, I become suspicious that they were calculated rather than measured. Therefore, we are right back to the start: we really cannot be sure about the conversion factor for this test kit. I don’t use this kit so it is unlikely that I will be posting nitrite correction values for it. Sorry.

Dan

 

[Lasse]

I have done some own experiments with nitrite standards, Hanna ULR marine nitrite and Checker low nitrate Checker.

I´ll admit that I was very sceptical to the graphs @Dan_P show in this thread. The nitrite interference was too low compared with other Hobby tests - IMO. However - you should never be too sure before you test. I have done one preliminary test just on nitrites interference with no nitrate involved. I mix a new bach of saltwater - using 38 g of Red Sea Pro salt. The resulting salinity was around 34 PSU. I test this for nitrite and nitrate. Results was 0 in nitrite and 0.25 as nitrate

Now I prepare a saltwater with 0.1 ppm nitrite

Result 29 ppb NO2-N -> 3,29*29/1000 = 0,095 ppm

Nitrate test on the same water - 0.40 ppm

Take away the original 0.25 ppm -> 0,15 ppm. I must admit that this is much inline with Dan_P:s result. A deviation of 0.15 ppm - I can accept with a hobby test:D


I also did a test with my own water from my own tank that show (diluted 10 times with my prepared new saltwater with known 0.25 ppm Nitrate) My result was 0 in nitrite and 1.22 nitrate - take away the initial 0.25 ->0.97 ppm nitrate * 10 =9,7 ppm Nitrate.

I did a try to spike this water with nitrite but did not get a good result. My nitrite standard is 1 mg/L - therefore I probably got a salinity interference too. I will redo this another day - I will mix 100 ml of my nitrite standard wit 3.8 g Red Sea Pro salt or use nitrate standard

As it looks now - I have to admit that I was wrong and Dan_P probably was closer to the truth than me.

For the moment it looks like that it is possible to ignore nitrite interference for the Hanna low nitrite checker at nitrite concentration below 0.1 ppm. But I will check with known nitrate + nitrite concentrations first. I will do more tests in the future

Sincerely Lasse

 

[taricha]

I´ll admit that I was very sceptical to the graphs @Dan_P show in this thread. The nitrite interference was too low compared with other Hobby tests - IMO. However - you should never be too sure before you test.

You could totally be forgiven for expecting different results. The Hanna NO3 kit generates a really unusually large amount of color from NO3 compared to other kits. This means that the conversion of NO3->NO2 is quite efficient, and the interfering color from a given NO2 is much smaller than in most of the kits out there.
This also makes it possible to do some more interesting stuff...
BTW, I used @Dan_P NO2 / NO3 interference data to do a comparison of Total ammonia - N consumed vs NO2-N + NO3-N produced in a test with some biospira that I fed ammonia to.
The NO2-N was around 0.11ppm and was still able to make measurements of final NO3-N (with correction) and NO2-N that added up very closely to the ammonia-N consumed (once I accounted for NO3 that comes in a bottle of biospira).

 

[KGV]

Wonderful thread! Did anyone do a similar analysis of nitrite interference on NO3 readings for the Hanna High Range NO3 checker HI-782?

 

[Nano sapiens]

Wonderful thread! Did anyone do a similar analysis of nitrite interference on NO3 readings for the Hanna High Range NO3 checker HI-782?

Bumping this as I am interested as well.

 

[taricha]

Here are the results for nitrite interference for Hanna Marine Nitrate and Red Sea Nitrate Pro.

Nitrite interference is smaller for Hanna than Red Sea. You will note that all slopes are much less than 100.

Wonderful thread! Did anyone do a similar analysis of nitrite interference on NO3 readings for the Hanna High Range NO3 checker HI-782?

Because I had need for this info, I took a look at it.

As with the LR checker, Hanna seems to do a good job with nitrite, even in their high range NO3 test (though not as good as their low range.)
At incidental NO2 values (0.1 - 0.2 ppm NO2) that it seems can be found in some established systems, the increase in the measured value of NO3 is not larger than the hanna stated error of +-2ppm or+-5%. So a tenth or two ppm NO2 is not telling any big lies about your NO3 on this test.
At low NO3, it looks like the interference is roughly +5ppm NO3 per 1ppm NO2, or maybe a bit less. At the top of the NO3 checker range, it may be more like +10ppm NO3 per 1ppm NO2.
(don't get too focused on the exact calculated slopes, the hanna error bars are big and create uncertainty in the slopes. In reality, I think the effect at very low NO3 will be smaller than at moderate NO3, even if my slope calculations don't show it.)

@Dan_P does this look plausible to you?

 

[KGV]

Thanks @taricha, that fits my observations comparing the Hanna LR and HR checker on samples just below 5ppm. There were very similar.

 

[Dan_P]

Because I had need for this info, I took a look at it.

As with the LR checker, Hanna seems to do a good job with nitrite, even in their high range NO3 test (though not as good as their low range.)
At incidental NO2 values (0.1 - 0.2 ppm NO2) that it seems can be found in some established systems, the increase in the measured value of NO3 is not larger than the hanna stated error of +-2ppm or+-5%. So a tenth or two ppm NO2 is not telling any big lies about your NO3 on this test.
At low NO3, it looks like the interference is roughly +5ppm NO3 per 1ppm NO2, or maybe a bit less. At the top of the NO3 checker range, it may be more like +10ppm NO3 per 1ppm NO2.
(don't get too focused on the exact calculated slopes, the hanna error bars are big and create uncertainty in the slopes. In reality, I think the effect at very low NO3 will be smaller than at moderate NO3, even if my slope calculations don't show it.)

@Dan_P does this look plausible to you?

Plausible!

Good to know. Thanks. I have been too busy/lazy to perform this study. I do need to do it on the modified API NO3 test, which might be a smidge better (need a study for this too!) than the Hanna HR nitrate chemistry.

 

[taricha]

I do need to do it on the modified API NO3 test, which might be a smidge better (need a study for this too!) than the Hanna HR nitrate chemistry.

If data like this graph is correct (2ppm ammonia increasing API NO3 reading by 100ppm), then API will be much worse in NO2 interference. I wonder if maybe it's missing the chemical destruction of initial NO2 that Red Sea / Hanna probably have?

 

[Dan_P]

If data like this graph is correct (2ppm ammonia increasing API NO3 reading by 100ppm), then API will be much worse in NO2 interference. I wonder if maybe it's missing the chemical destruction of initial NO2 that Red Sea / Hanna probably have?

I believe that you are summing up the situation correctly. I expect the API NO3 chemistry to be sensitive to NO2. Fun fact: reagent 1, the yellow solution, in the nitrate kit can be used to detect nitrite by itself. I haven’t generated a calibration curve though.

Powered zinc (firework grade) can be purchased by the pound. I am thinking of buying some to “upgrade“ some nitrate test kits. It will require filtration but if I can boost sensitivity, I might learn to like filtration.

 

[Randy Holmes-Farley]

Powered zinc (firework grade) can be purchased by the pound. I am thinking of buying some to “upgrade“ some nitrate test kits. It will require filtration but if I can boost sensitivity, I might learn to like filtration.

And if it all goes sideways, at least there will be a nice light show. lol

 

[Dan_P]

And if it all goes sideways, at least there will be a nice light show. lol

It’s almost like you knew what I used to do in my dim dark past :-)

 

[taricha]

Powered zinc (firework grade) can be purchased by the pound. I am thinking of buying some to “upgrade“ some nitrate test kits. It will require filtration but if I can boost sensitivity, I might learn to like filtration.

Wonder if big zinc column would get you where you are trying to go.