ICP vs home test kit nitrates

[Reefer_Marc]

Good day everyone

I have a quick question regarding my ICP test.
For the last 6 months my nitrates have always been around 8 to 12 ppm. I sent in an ICP test about 3 weeks ago, and got the results back last friday. According to the ICP my nitrates are at 0.1 ppm, i took a nitrate test at home at the same time i filled the bottle for the ICP and my test showed me 12.
i use the red sea test kit and it was consistently in this range for the last 6 months. The test kit is not expired and i used clean glasses.

Which one is better to trust? I read online that ICPs are not as good at testing nitrates, is that correct?

Thank you very much for the help!

 

[ReneReef]

First, test kit expiration dates are only valid while unopened. Just like a bottle of milk.
After opening and with each use reagents degrade.

Secondly, nitrite interferes with nitrate test kits. How much depends on the test kit brand.
A tiny bit of nitrite can have a big influence on your nitrate test. Nitrite is present in many a (mature) reef tank and is not an issue. Do your ICP results show nitrite?

Third, ICP-OES or ICP-MS cannot measure nitrate. The ICP part of the technique blasts all molecules (including nitrate) into their atomic components. OES and MS then detect atoms, in a giant cloud of atoms from all other substances in your water sample.

Not all ICP companies use the same technique for detecting nitrate. It may be colorimetric with a spectrophotometer or Ion Chromatography (IC), IC being the best.

Any of these techniques will most likely be better than your home test. A lab will run regular reference measurements and keep their equipment calibrated. Also nitrate does not degrade or is not consumed that much in transit.

I think that the reports of unreliable nitrate testing by ICP company, is way more likely an issue with our home tests. However, people tend to put more trust in their own abilities, than those of an external party beyond their perceives control.

P.S. If your ICP company is unclear about what techniques they use for what purpose. I would send them an e-mail and ask. If they evade answer, I would never use them again.

 

[Reefer_Marc]

First, test kit expiration dates are only valid while unopened. Just like a bottle of milk.
After opening and with each use reagents degrade.

Secondly, nitrite interferes with nitrate test kits. How much depends on the test kit brand.
A tiny bit of nitrite can have a big influence on your nitrate test. Nitrite is present in many a (mature) reef tank and is not an issue. Do your ICP results show nitrite?

Third, ICP-OES or ICP-MS cannot measure nitrate. The ICP part of the technique blasts all molecules (including nitrate) into their atomic components. OES and MS then detect atoms, in a giant cloud of atoms from all other substances in your water sample.

Not all ICP companies use the same technique for detecting nitrate. It may be colorimetric with a spectrophotometer or Ion Chromatography (IC), IC being the best.

Any of these techniques will most likely be better than your home test. A lab will run regular reference measurements and keep their equipment calibrated. Also nitrate does not degrade or is not consumed that much in transit.

I think that the reports of unreliable nitrate testing by ICP company, is way more likely an issue with our home tests. However, people tend to put more trust in their own abilities, than those of an external party beyond their perceives control.

P.S. If your ICP company is unclear about what techniques they use for what purpose. I would send them an e-mail and ask. If they evade answer, I would never use them again.

Thank you very much for your answer!

According to the ICP, nitrites are 0.
i am using the fauna marin icp total test.
I will get some new reagents and check it again, thank you!
It is a ICP OES test, so it can not measure nitrates?

I will still get some new reagents and check again, if necessary check if my LFS can run a test as well to crosscheck.

 

[ReneReef]

Thank you very much for your answer!

According to the ICP, nitrites are 0.
i am using the fauna marin icp total test.
I will get some new reagents and check it again, thank you!
It is a ICP OES test, so it can not measure nitrates?

I will still get some new reagents and check again, if necessary check if my LFS can run a test as well to crosscheck.

Your welcome.

There is no ICP that can measure nitrate. ICP is a very specific machine/method. As I stated before it can not detect molecules. Nitrate is a molecule.

Vendors always use a different test method for molecules like, nitrate and nitrite. In case of phosphate some vendors calculate phosphate from P (phosphorus atom), assuming that all P in the sample was in phosphate. FM does a calculated and photometric determined phosphate I believe.

 

[CHSUB]

I use FM ICP also and my results at home were the same. Home testing is with both Hanna LR and Salifert. Salifert tested 0 ppm and Hanna LR and FM ICP tested .1ppm.

 

[Lasse]

FM use Ion chromatography for NO3. Its a very good method.

I would trust their measurements and throw away the Red Sea tests.

Sincerely Lasse