Science Buddies: "Ask an Expert"

Hello. (: I'm doing a project that involves measuring the levels of nitrate and nitrite dissolved in water, and I was hoping that one of you experts might be able to give me some advice on how to measure this accurately. There are a few things that you might want to know about this project:

1 - I'm not sure about the accuracy of conventional aquarium water nitrate/nitrite testing kits. I'm open to using those if I must, but I really don't know anything about them.
2 - I'll be measuring relatively high levels of nitrates (think 3000 ppm) and normal levels of nitrites (0-10 ppm, most likely).
3 - Ideally I'd be using a spectrophotometer, but the literature on this seems really complicated - lots of terms I don't understand and lots of scholarly journal articles I don't have access to. I'm really looking for a method that would require reagents that I can actually acquire easily and would be relatively simple. I'm not sure yet if this exists.

Thanks in advance for any help that you can provide. c: This would be a great help for my project.

The environmental N test kits that are designed to detect lots of different Nitrogen chemicals that typically fall into a standard range of 0.5 to 10 ppm and a low range of 0.05 to 1.0 ppm.

Some acquarium test kits are accurate for nitrate (NO3) in the 5 to 160 ppm range for NO3 produced by biolgical filters that convert amonnonia and nitrite to nitrate and may not be appropriate for your testing.

Other acquarium test kits are specific for nitrite (NO2) in the 0.05 to 10 ppm range.

For samples that are off scale high, you would have to dilute the samples with distilled water.

For this kind of testing, you will have to have extremely good lab proceedures to prevent carry over and cross contamination.

Thank you very much. (: I didn't realize that I could move the test results into an acceptable range by diluting them.

Would you happen to know about how accurate these test kits are, and would you have any recommendations?

If you're lucky the test kit will list in its specifications how accurate it is (though there's a serious question about how much I'd trust a mass-market product).

However, you don't need to be lucky, you can find out for yourself. The best approach would be to develop a procedure to calibrate your test kit on a known concentration of nitrate/nitrite, using a procedure similar to the one described here: http://www.plantedtank.net/forums/ferti ... mists.html

Adding such a step to your experimental procedure will improve its perceived quality considerably, I would think.