Can someone tell me how to calibrate my kit?

[Carissa]

I want to test my nitrate kit to see if it is in fact accurate. What's an easy way to go about doing this with kno3? I guess I just need to know how much to mix in with how much water.


Also a question. According to what I looked up on my Hagen test kits, the first two bottles of solution that I add to the nitrate test are identlcal to the two bottles used for nitrite testing. Does this sound right? It seems like every time I test nitrite and nitrate, they end up looking the same exact color. I don't know if this is coincidence or not. But you're only supposed to let nitrites sit for 2 minutes but nitrates are supposed to sit for 5. Is it normal for both of them to always come out the same if you let them sit long enough? How do these things work?

 

[nwfishinfool]

Carissa

Since I have no idea how to link to an old thread I copied this. I recently used this to validate my test kits as well.

It was a Tom Barr Re-Post of a Thread by LeftC



How to Make NO3 and PO4 Reference Solutions

Here's a way to make 10, 20, 30 and 40 ppm NO3 reference solutions:

Add 1.631 g of KNO3 to 1 L DI/RO water. This makes a 1000 ppm NO3 solution. (It's really a 1000.29 ppm solution.)

Add 2 mL of the 1000 ppm solution to 18 mL of DI/RO water. This makes 20 mL of a 100 ppm NO3 solution.

Add 15 mL of the 100 ppm solution to 15 mL of DI/RO water. This makes 30 mL of a 50 ppm NO3 solution.

To make a 10 ppm NO3 solution:
Add 2 mL of the 50 ppm solution to 8 mL of DI/RO water. This makes 10 mL of a 10 ppm NO3 solution.

To make a 20 ppm NO3 solution:
Add 4 mL of the 50 ppm solution to 6 mL of DI/RO water. This makes 10 mL of a 20 ppm NO3 solution.

To make a 30 ppm NO3 solution:
Add 6 mL of the 50 ppm solution to 4 mL of DI/RO water. This makes 10 mL of a 30 ppm NO3 solution.

To make a 40 ppm NO3 solution:
Add 8 mL of the 50 ppm solution to 2 mL of DI/RO water. This makes 10 mL of a 40 ppm NO3 solution.




Here's a way to make 1.0, 2.0, 3.0, 4.0 and 5.0 ppm PO4 reference solutions:

Add 1.433 g of KH2PO4 to 1 L DI/RO water. This makes a 1000 ppm PO4 solution. (It's really a 1000.09 ppm solution.)

Add 1 mL of the 1000 ppm solution to 9 mL of DI/RO water. This makes 10 mL of a 100 ppm PO4 solution.

Add 2 mL of the 100 ppm solution to 18 mL of DI/RO water. This makes 20 mL of a 10 ppm PO4 solution.

To make a 1.0 ppm PO4 solution:
Add 1 mL of the 10 ppm solution to 9 mL of DI/RO water. This makes 10 mL of a 1.0 ppm PO4 solution.

To make a 2.0 ppm PO4 solution:
Add 2 mL of the 10 ppm solution to 8 mL of DI/RO water. This makes 10 mL of a 2.0 ppm PO4 solution.

To make a 3.0 ppm PO4 solution:
Add 3 mL of the 10 ppm solution to 7 mL of DI/RO water. This makes 10 mL of a 3.0 ppm PO4 solution.

To make a 4.0 ppm PO4 solution:
Add 4 mL of the 10 ppm solution to 6 mL of DI/RO water. This makes 10 mL of a 4.0 ppm PO4 solution.

To make a 5.0 ppm PO4 solution:
Add 5 mL of the 10 ppm solution to 5 mL of DI/RO water. This makes 10 mL of a 5.0 ppm PO4 solution.

Left C

 

[Carissa]

That's great, but I don't have a sensitive enough scale to weigh 1.6 grams. I wonder if there's any way to do it using volume measurements.

 

[Carissa]

I just found the answer. According to Rex Grigg's website, 3 tsp of kno3 are equivalent to 16.8 grams. Using that math, 0.7 grams would be 1/8 tsp. which is probably the smallest amount I can measure with any degree of accuracy. Looking at my test kit, I think I want a 20ppm solution to use for calibrating. 0.7 is .429% of 1.631. So I need to use 429 ml of water in my solution. I don't have any distilled water but my tap water is devoid of pretty much anything, as long as there are no nitrates I'm guessing I'm ok. Then I can follow the rest of the instructions to make a 20ppm solution. If any of this sounds wrong let me know! I'm going to go try it now.

 

[Carissa]

Ok, it looks like my test kit is showing lower than what it is. If I go by the "saltwater" color scale on the chart, it actually works out pretty good, so that's what I'll do from now on. Or, I have to let it sit longer than the kit says to develop color.

 

[Tom Barr]

If youlack a sensitive scale, then you have a lot of error in the reference standard, basically it's not a ref standard

To play this game, you need a decent scale.
They do not cost much.

Regards,
tom Barr

 

[Carissa]

Yeah I was thinking that there is not much of a margin of error here. I decided instead to go with 1/4 tsp instead of 1/8 tsp because I could measure that more accurately, and then double the amount of water I added to it since I do have the measuring device for measuring 1ml at a time. Anyway I guess for now I know that the kit is in the general range of correct, but the fact is that it's nearly impossible to distinguish between the different colors once you get up to 20ppm or higher anyway. How much margin of error do I have when it comes to dosing? At what point will my fish suffer if I add too much nitrate? If there's a wide margin of error, I'll just keep enough in there so that I'm always registering some nitrate and not worry about my test kit.

 

[tcomfort]

...I'll just keep enough in there... and not worry about my test kit.

You just summed up EI in 13 words.

 

[Carissa]

Well I was doing ei, but evidently I needed more nitrate than the non-co2 dosage was telling me, because nitrates were around 0 when I tested it. I guess I had too much plant mass or something.