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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?
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
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.
HI 736, ULR P Checker Standard Curve
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
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.
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?
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
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.
HI 736, ULR P Checker Standard Curve
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
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.