How to make DIY calibration solution for nitrates?

[Magik]

Hi,

My RedSea Nitrate tests keep showing 0, even with reagents 5x concentrated, it also always says 0 on bag water I test from fellow reefers. My phosphates are 0.1-0.12ppm (Hanna Ultra Low Phosphorus checker). If the nitrates are indeed 0, I was considering dosing KN03, especially since I am keeping mostly LPS. Before I do anything, I wanted to make sure that my nitrate levels are indeed 0.

Has anyone tried to do calibration solution for nitrate tests? I was thinking for example of buying food grade KNO3 powder, measuring 5g of it, dissolving in 1L water, taking 1ml, dissolving in 1L again. That should give me around 5pp nitrate solution, right? Of course it will not be terribly accurate since I do not have access to lab grade scale, but I thought would make sense to see if my tests are capable of detecting nitrates. I also wondered whether I should use RODI or SW for dissolving KNO3? The rationale for using saltwater would be to make detection conditions similar to my tank water. I am using IO salt and RODI water - the salt should not contain any nitrates, I guess? All advice appreciated. Pity Triton test does not include nitrates for comprehensiveness.

 

[nereefpat]

Your math isn't right on your diy solution, because not all of the KNO3 is nitrate. K = about 39 % of the weight, so in your example, you would only be about 61% of the way to 5ppm nitrate.

Anyway, if I remember correctly, about 1/2 gram KNO3 will raise nitrates 1ppm for every 100 gallons.

 

[Dan_P]

Atomic and molecular weights:

K+ 39.1
NO3- 62 (14 + 3*16)

NO3 mass in the salt makes up 62/(62+39.1) or 61.3 % of the salt.

5 g KNO3 in 1 liter water (nitrate test works in salt or fresh water) would be 3.1 g NO3 or 3100 mg / L, about 3100 ppm.

You could dilute this to get to whatever ppm you wish and avoid the measurement of tiny amounts of salt.

As for testing 0 ppm NO3, the test results should be reported as less than 0.2 or 0.1 ppm. Low, but not zero.

Overall, your idea is sound.

 

[bertoni]

Hanna makes a calibration solution:

http://hannainst.com/10-ppm-and-100...jvOzXMkjmqPSAS6pEMHsiv9Kk7F6ko1nOmxoCFU_w_wcB

It's fairly expensive, though, so getting a scale and some potassium nitrate probably would save some money, and be more than good enough for your purpose.

 

[Rybren]

Fauna Marin also makes a reference solution that is less than $20.

It comes in a 100ml bottle and is a multi-reference solution for the following:

Calcium
Magnesium
Potassium
Salinity
Alk
Strontium
Nitrate
Phosphate

 

[Magik]

Atomic and molecular weights:

K+ 39.1
NO3- 62 (14 + 3*16)

NO3 mass in the salt makes up 62/(62+39.1) or 61.3 % of the salt.

5 g KNO3 in 1 liter water (nitrate test works in salt or fresh water) would be 3.1 g NO3 or 3100 mg / L, about 3100 ppm.

You could dilute this to get to whatever ppm you wish and avoid the measurement of tiny amounts of salt.

As for testing 0 ppm NO3, the test results should be reported as less than 0.2 or 0.1 ppm. Low, but not zero.

Overall, your idea is sound.

Oh, forgot it has to be ppm NO3 not KNO3, thanks!

 

[Magik]

Hanna makes a calibration solution:

http://hannainst.com/10-ppm-and-100...jvOzXMkjmqPSAS6pEMHsiv9Kk7F6ko1nOmxoCFU_w_wcB

It's fairly expensive, though, so getting a scale and some potassium nitrate probably would save some money, and be more than good enough for your purpose.

Good to know, but indeed too pricey. Would be cheaper to buy couple new nitrates tests, that I hope to avoid.

 

[Magik]

Hanna makes a calibration solution:

http://hannainst.com/10-ppm-and-100...jvOzXMkjmqPSAS6pEMHsiv9Kk7F6ko1nOmxoCFU_w_wcB

It's fairly expensive, though, so getting a scale and some potassium nitrate probably would save some money, and be more than good enough for your purpose.

Oh, that is interesting, thank you. But indeed pricey.

 

[Magik]

Fauna Marin also makes a reference solution that is less than $20.

It comes in a 100ml bottle and is a multi-reference solution for the following:

Calcium
Magnesium
Potassium
Salinity
Alk
Strontium
Nitrate
Phosphate

Oh, that multi-reference solution sounds wonderful! Looks like it is not sold in US, where I live, but I will be in Europe this summer, will try to bring some

BTW, salinity solution for calibration is not good to calibrate magnesium, calcium, alkalinity etc?

 

[bertoni]

The average salinity solution probably isn't controlled well enough for the other parameters. Some of them are made out of artificial saltwater, which is a decent start, but salt products are inconsistent enough that I wouldn't trust them for calibration.

If you just want a basic sanity test, a teaspoon of potassium nitrate in a liter of water should at least show up on the kit.

 

[Magik]

The average salinity solution probably isn't controlled well enough for the other parameters. Some of them are made out of artificial saltwater, which is a decent start, but salt products are inconsistent enough that I wouldn't trust them for calibration.

If you just want a basic sanity test, a teaspoon of potassium nitrate in a liter of water should at least show up on the kit.

Thank you very much. This is exactly what I wanted, to check if my test is capable of showing any other color than blue "0 ppm nitrate"

 

[Jwheld]

I would go the KNO3 route, or NaNO3 for making a calibration standard. Then, if your system is close to zero, you'll have the nitrate to dose to maintain proper levels... if that is your desire.

 

[Magik]

I would go the KNO3 route, or NaNO3 for making a calibration standard. Then, if your system is close to zero, you'll have the nitrate to dose to maintain proper levels... if that is your desire.

Yes, I was considering it, would be killing two birds with one stone .

Seems that a lot of people dose "stump remover" which is supposed to be pure KNO3, but for stump removing impurities probably do not matter much?. I was thinking of buying food grade KNO3, making calibration solution and if indeed my nitrates are virtually 0, experiment with dosing a bit.

 

[bertoni]

I'd go with food grade products. The stump remover might be fine, but the extra cost of food grade should be very small over time. Also, food grade products are required to list ingredients, I believe, and stump remover products aren't.