Here Is A Way To Measure Ammonia Accurately

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Dan_P

Dan_P

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Yes when i shook it up it was yellow. Ill check if the kits expired or something and report back. Whats my result of .13 ppm mean? Ive got that much ammonia?
First look at the graph I posted and find what 0.12 corresponds to on the y axis. The problem with the ammonia test is that it can also react with amino acids, giving a false positive
 
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Fwiw the ali test kit expired june 2019 so that might be the reason for the instant yellow color.
 

Rick Mathew

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In my frequent conversations with @brandon429, ammonia measurement is a frequent topic. It seems that our colorimetric hobby kits are difficult to interpret at the low end of the scale. Many users have trouble deciding whether the test is indicating 0 ppm or 0.25 ppm. In turn, this can lead them to conclude that the nitrogen cycle has stalled in their new aquarium or that their established system had an ammonia spike. Even though we can easily argue that these events are false positives, having an unambiguous ammonia reading would be best.

Some time ago @taricha and I needed to measure low concentrations of ammonia. We ended up optimizing the much maligned API ammonia test kit. We were able with the aid of either a spectrometer or Hanna Checker to measure total ammonia levels below 0.1 ppm and detect the presence of ammonia at ~0.05 ppm. I applied similar adjustments to the Red Sea ammonia test kit and achieved similar results. In addition, I developed standard curves for several popular Hanna Checkers (LR PO4, ULR P, and Alkalinity Checkers) to measure the color intensity of the modified Red Sea test.

The New Red Sea Recipe

I did the development work on 5 mL samples. You will need to double the recipe to make enough solution for a Hanna Checker. For 5 mL of sample, add 0.05 mL (Salifert red scoop) of the powder reagent A (for a 10 mL sample, one level white scoop, 0.15 mL, supplied with the Red Sea should be OK). When it is completely dissolved add two (2) drops reagent C, swirl to completely dissolve, and then add two (2) drops reagent B, one at a time and swirling the solution to dissolve the drop. The “add drop-swirl” seems to minimize yellow color formation. Let the test color develop for one hour. Here is a picture of my standard curve test solutions. Notice how nearly colorless the “zero” sample is all the way to the right. 0.05 ppm is next to it. Cool right?

29252DFC-A1BA-49D5-8E10-34200BFAD22F.jpeg


Hanna Checker Standard Curves

I found three Hanna Checkers to be useful for measuring the color intensity of the modified Red Sea ammonia test.

HI 713, LR PO4 Checker Standard Curve

E04B2F5D-FAE1-45F8-915B-73AF96CF5EEC.png


The curve is not exactly linear, probably because the wavelength of light used in this Checker does not correspond to the peak absorbance of the test color. It is measuring the far edge of the peak. For our purposes, the linearity is sufficient.

Another feature to note are the two data points that touch each other. This is a problem with the test chemistry and limits how small of a concentration can be measured with this method. I estimate that the method can be trusted for a ammonia quantity to just below 0.1 ppm. The good news is that this method can detect total ammonia down to at least 0.05 ppm. This means the solution will color up at 0.05 ppm NH3 but we cannot assign a value. The picture below demonstrates the difference in color between 0 (on the right) and 0.05 ppm.

A6CCA98E-E679-4F52-90A3-02303B8DFE87.jpeg



HI 736, ULR P Checker Standard Curve

0414922F-37EA-4EBB-8AD9-868AAB044457.png


In this curve you can more easily see how the standard curve drops off after 0.1 ppm. Again, we can measure down to 0.1 ppm but we can detect down to at least 0.05 ppm.

HI 755, Alkalinity Checker Standard Curve

29993C87-9264-4CB7-9D42-BF584C35D14F.png


Because of the way this Checker is programmed, it calls solutions with a color intensity of the 0.2 ppm NH3 test solution “zero”. This Checker might be useful in a pinch though.

Here is my standard curve data.

976BD01E-1AB4-41DC-914B-98F72FD7BF6E.png
As usual...Awesome work!! Well done!
 

puffy127

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So just to be clear, if one were to use the Hanna ULR P checker with the Red Sea Recipe, they would need to use 10 ml of tank water, one white RedSea scoop of Reagent A, 4 drops of Reagent C, then 4 drops of Reagent B, correct? If you have to let it sit for an hour, that will timeout between C1 and C2 measurements. How are you measuring C1 with the checker? With a separate cuvette with just tank water?

After getting the results from the Hanna Checker, use the standard curve data to convert to NH3?
 

taricha

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So just to be clear, if one were to use the Hanna ULR P checker with the Red Sea Recipe, they would need to use 10 ml of tank water, one white RedSea scoop of Reagent A, 4 drops of Reagent C, then 4 drops of Reagent B, correct? If you have to let it sit for an hour, that will timeout between C1 and C2 measurements. How are you measuring C1 with the checker? With a separate cuvette with just tank water?

After getting the results from the Hanna Checker, use the standard curve data to convert to NH3?
Correct, you can simply use tank water in a separate cuvette as the C1 blank. If you only have one cuvette you trust, then you can do the one hour reaction in another container and transfer it into the cuvette after you get the C1 blank reading (but unless one of your two cuvettes is stained, that's really not necessary.)
Edit: then yes, compare to the standard curve posted by Dan.
 
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puffy127

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Correct, you can simply use tank water in a separate cuvette as the C1 blank. If you only have one cuvette you trust, then you can do the one hour reaction in another container and transfer it into the cuvette after you get the C1 blank reading (but unless one of your two cuvettes is stained, that's really not necessary.)
Edit: then yes, compare to the standard curve posted by Dan.
Ok, I tried this today and compared manual results using the RedSea kit and the Hanna ULR P checker.

I got between 0 - 0.2 ppm on the manual RedSea kit (TAN). Assuming it is on the high end, 0.2 ppm, and a pH of 8.0 and 79F, which yields 5.8% NH3, that would give 0.0116 ppm NH3.

Using the Hanna with the RedSea reagents yields 79 ppb, which is 0.134 NH3, a factor of 10 off.

Am I doing these calculations correctly?
 

taricha

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Using the Hanna with the RedSea reagents yields 79 ppb, which is 0.134 NH3, a factor of 10 off.
Yeah. We should be clearer. We are measuring total ammonia. We just do the calculations as NH3 ppm for shorthand.
So you calculated 0.134ppm which fits well with what the Color card gave - between 0 and 0.2ppm.
 
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puffy127

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Yeah. We should be clearer. We are calculating total ammonia. We just do the calculations as NH3 ppm for shorthand.
So you calculated 0.134ppm which fits well with what the Color card gave - between 0 and 0.2ppm.

Ok, thank you for the clarification.
 

puffy127

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Now that we can get a more accurate digital ammonia reading, has anyone compared these results to Hanna's FW Ammonia Checker to see how they compare (and to see whether Hanna's FW Ammonia Checker can be used for saltwater)?
 

taricha

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That's a nessler kit and though nessler kits can work in saltwater, the sensitivity is generally lower than the salicylate kits we are using.
See illustration here
Pic comparison
 
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puffy127

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How was the testing done in the development of this method? What were the results compared against?
 
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How was the testing done in the development of this method? What were the results compared against?
Are you referring to the Red Sea or API modification? And what do mean “how was the testing done”?
 

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The RedSea. Not a criticism, just curious - after developing the curves, were there comparisons of samples using the Hanna checker results/calculations with Seneye readings?
 
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The RedSea. Not a criticism, just curious - after developing the curves, were there comparisons of samples using the Hanna checker results/calculations with Seneye readings?
No problem! Just want to make sure I was answering the right question.

The curves were made by measuring the color intensity with a Hanna Checker of test solutions made with known concentrations of total ammonia. These solutions were made from a concentrated standard solution of an ammonium salt purchased from Hach. In this way I knew that a certain Checker value corresponded to a given concentration of ammonia.

By the way, if the Seneye wasn’t so expensive, I would test its readings against known concentrations of total ammonia.
 
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puffy127

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No problem! Just want to make sure I was answering the right question.

The curves were made by measuring the color intensity with a Hanna Checker of test solutions made with known concentrations of total ammonia. These solutions were made from a concentrated standard solution of an ammonium salt purchased from Hach. In this way I knew that a certain Checker value corresponded to a given concentration of ammonia.

By the way, if the Seneye wasn’t so expensive, I would test its readings against known concentrations of total ammonia.
Great, thanks! Again, thank you for all the work on this.
 

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I tested this method with the RedSea kit to see how much therapeutic copper levels affected readings and gave a false positive ammonia level of about 10x (0.05 ppm before copper, 0.5 ppm after). It maxed out the ULR P and had to use the Hanna alk checker. Do you chemistry folks know why that is? Would using the API kit be any different?
 

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@Dan_P @taricha Good stuff!!

Important point that some may not know is that this is a NH4/NH3 (ammonium/ammonia) test and the fractions of each are pH dependent. With high pH having a higher fraction of NH3. *In fact it's a good idea if a stocked tank is producing truly detectable NH4/NH3 to lower the pH to 7.8 with HCl/hydrochloric acid/muriatic acid.

*must know what you're doing as can truly make things so much worse
 
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