Resource API Nitrate (NO3) Test Kit Accuracy & Reference Images

[ScaperHaynes]

Hi all,

I was recently inspired by @Naturescapes_Rocco and his testing of Salifert test kit accuracy [Linked here]. Since I have access to very high end lab equipment at work, I figured I'd give this a try with my API test kit for Nitrates.

My two main goals were: #1 Test accuracy of the test kit against known solutions #2 Create a more realistic reference for determining color.

My serial dilution breakdown was as follows, "H20" refers to lab grade RODI water.
Stock Solution: 1600ppm (500ml H2O + 1.30g KNO3) --> This gave me a reasonably large amount of KNO3 to measure with high grade lab equipment
Dilution 1: (5ml 1600ppm + 45ml H20) = 160ppm
Dilution 2: (25ml 160ppm + 25ml H20) = 80ppm
Dilution 3: (25ml 80ppm + 25ml H20) = 40 ppm
Dilution 4: (25ml 40ppm + 25ml H20) = 20 ppm
Dilution 5: (25ml 20ppm + 25ml H20) = 10pm
Control: (H20 Only) = 0 ppm

Dilutions were created using a high accuracy adjustable micropipette that could hold 10ml max.

Accuracy Results
Generally found that this particular test kit was accurate. It is VERY important to remember with the API Nitrate (NO3) Test kit that you have to shake Reagent #2 for 30 seconds prior to use in addition to shaking the vial for 1.5 minutes after adding reagents #1 and #2. I did not read the instructions the first month I was using this test kit and thoroughly confused myself regarding my dosing.

Color Photo References
I found that it was considerably easier to determine my tank's actual concentration when I compared it to vials of known concentrations versus the color chart. Sadly, it's a bit too much work to make a round of reference solutions every time I test, so I opted to see if images of real solutions would be better than the color chart.

Using an image of the vials as reference seems to be a step up from just the color chart alone, but not quite as good as having reference solutions on hand. I figured I'd provide these images in a variety of forms for others to try out.

 

[Naturescapes_Rocco]

Great work! I genuinely believe 90%+ of API Nitrate users don't know how serious important the shaking steps are. Hopefully we can link back to this thread to explain why shaking is required.

 

[hamfist]

Nice work. I'd like to add that it is also vital to read the test with the tube around 1cm from the backing card to see the true colour. Also very beneficial to use decent diffuse natural sunlight.

SOmeone else's communication with API received this .......... "

Thank you for inquiring at API. The color is best interpreted when it is not touching the surface but holding away. "​

IME, so many people struggle with this test by holding the tube right up to the white card, and this displays a shade of orange usually much darker than the true colour. I find this particularly important with this test.

 

[BenB]

This is awesome.
I hope you have plans to test other kits.
We have data on the Hannah NO3 kits. PO4 would be awesome.
I use Salifert PO4 and struggle to read it. I don't like looking through the top of the vial. There are always different shadows and light diffractions.

 

[Sulla]

I shake that thang like it's my money maker!

Thanks so much for the reference photos. Super helpful

 

[Aquajack]

Thanks so much. great to hear its at least at a level of accuracy we can use as a starting indicator.
I always shake reagent #2 for around 40 seconds and give it a good bump on a hard surface a few times too then around 90 seconds shaking the vial like crazy. People look at me like I'm silly when I'm doing it lol.

 

[ScaperHaynes]

Glad to see this was useful for others to some degree!

This is awesome.
I hope you have plans to test other kits.
We have data on the Hannah NO3 kits. PO4 would be awesome.
I use Salifert PO4 and struggle to read it. I don't like looking through the top of the vial. There are always different shadows and light diffractions.

@BenB - PO4 is on my list to try as well, I’ve got the Sera kit and can’t decide what color it is to save my life. The challenge I’m running into with this test is that I don’t have 5 glass vials the same shape and size as the Sera vials to do a side by side comparison. Will have to figure out a way around that.

Nice work. I'd like to add that it is also vital to read the test with the tube around 1cm from the backing card to see the true colour. Also very beneficial to use decent diffuse natural sunlight.

SOmeone else's communication with API received this .......... "

Thank you for inquiring at API. The color is best interpreted when it is not touching the surface but holding away. "​

IME, so many people struggle with this test by holding the tube right up to the white card, and this displays a shade of orange usually much darker than the true colour. I find this particularly important with this test.

@hamfist I think what people also don’t realize is how much our perception of color is affected by neighboring colors. I always cover up the portion of the chart I’m not using… though I can’t say that’s a game changer in distinguishing colors.

 

[BenB]

Glad to see this was useful for others to some degree!

It was more than just a degree.
I believe some of us are testers and some of us just go with EI, put some in, and monitor their plants. Both are successful, but everyone seems to test even if just randomly at some point. So, this helps us all.

PO4 is on my list to try as well, I’ve got the Sera kit and can’t decide what color it is to save my life. The challenge I’m running into with this test is that I don’t have 5 glass vials the same shape and size as the Sera vials to do a side by side comparison. Will have to figure out a way around that.

Sera or Salifert? A lot of people here have Salifert and could probably send you a spare vial or two. It's just frustrating the amount of postage for a little plastic tube.

 

[ScaperHaynes]

Sera or Salifert? A lot of people here have Salifert and could probably send you a spare vial or two. It's just frustrating the amount of postage for a little plastic tube.

I do actually have Sera, but I just ordered a Salifert as well. We’ll see if I can work around the vial issue, but I’ll reach out if not.

 

[VJM]

Wow, thank you so much for this! I struggle with this kit and I think you nailed a couple factors that might be causing me to get varying readings. Super helpful !