Nitrate drop checker? - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 12-07-2007, 10:55 AM Thread Starter
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Nitrate drop checker?

We know you can make a checker for CO2 but is there any possible way to make one to keep an eye on nitrates?

I know it wouldn't be 100% accurate for the most part but I still think it could help.

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post #2 of 6 (permalink) Old 12-07-2007, 12:46 PM
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Make one of these.
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post #3 of 6 (permalink) Old 12-07-2007, 02:56 PM
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Quote:
Originally Posted by swylie View Post
And that doesn't include the interface, computer, and software required for that particular probe.

Other ISE's can be used with a good pH/mV meter - but that one can't.

Also, ISE's are not really great for long-term (continuous) exposure in a tank. Generally they work best as a dip-test with storage in a special solution when not being used.

Kevin

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post #4 of 6 (permalink) Old 12-07-2007, 03:20 PM
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The most serious problem limiting use of ion-selective electrodes is interference from other, undesired, ions. No ion-selective electrodes are completely ion-specific; all are sensitive to other ions having similar physical properties, to an extent which depends on the degree of similarity. Most of these interferences are weak enough to be ignored, but in some cases the electrode may actually be much more sensitive to the interfering ion than to the desired ion, requiring that the interfering ion be present only in relatively very low concentrations, or entirely absent. In practice, the relative sensitivities of each type of ion-specific electrode to various interfering ions is generally known and should be checked for each case; however the precise degree of interference depends on many factors, preventing precise correction of readings. Instead, the calculation of relative degree of interference from the concentration of interfering ions can only be used as a guide to determine whether the approximate extent of the interference will allow reliable measurements, or whether the experiment will need to be redesigned so as to reduce the effect of interfering ions.NO3, NH4, Ca and other ion selective probes have serious issues with interference ions, that's why these are used for labs, not environmental monitoring................when you have high levels of other similar charged(say NH4+ and K+) or stronger ions present.

Generally, you take a sample, add other chemicals to remove/prevent this interference, then take the reading. The chemicals required to be added tend to rather nasty, so you are not going to add them to your tank. The calibration for the probe must also be done each time you use it. If you just leave it in the tank, the accuracy will float all over the place.
Here's a bit on it.

http://www.chemistry.nmsu.edu/Instru..._Electrod.html

You also need a 1 or 10 ppm and 100, and 1000 ppm calibration solution set to calibrate the probe.

Having said all this, they are great for measuring lots of samples all at once.......so say you have 100 x 25 mls NO3 samples...........something aquarist rarely ever do...........but research very often does.
They ain't cheap either, so many research folks make their own.

One thing aquarist can do is freeze their water samples, and when they have 100 or so taken over some time frame(say daily for the last 3.5 months,), they can thaw and measure them and then plot the data with the known amounts of added KNO3 stock solution to their tank.

Few aquarists will EVER do this.

They just want something they can glance at and that's cheap that does not require a test kit method.

There are quite a few trade offs, I think it's far far cheaper and easier to simply automate your water changes. Dosing is very simple and accurate that way.

Then you do not worry about all this.

Regards,
Tom Barr




Regards,
Tom Barr
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post #5 of 6 (permalink) Old 12-07-2007, 03:38 PM
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Tom, did you mean to say that some researchers make their own ISEs? I didn't know this was realistically possible. My answer to the OP was sorta snarky in that sense.

Also, I had a thought regarding interfering ions. If you had two ISEs for two chemical species, each subject to interference from the other, wouldn't it be possible to use the reading from one to correct the reading from the other? Assuming that the interfering signal was somewhat smaller than the intended signal. That's tangential to this discussion though for reasons that you've elaborated. ISEs aren't really useful to the hobby.

I suppose it would be possible to automate the colorimetric nitrate method, but that would require a serious amount of DIY work. And then you'd want a spec, and then you're into $$$ territory.
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post #6 of 6 (permalink) Old 12-07-2007, 05:38 PM
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Quote:
Originally Posted by plantbrain View Post
The most serious problem limiting use of ion-selective electrodes is interference from other, undesired, ions. (lots of other stuff deleted)
From the Vernier site regarding the nitrate electrode:

"Interfering Ions: ClO4-, I-, ClO3-, CN-, BF4- " (perchlorate, iodide, chlorate, cyanide, and boron tetrafluoride)

I don't think we aquarists have much to worry about as far as nitrate interfering ions . . .

Back to the question of the OP:

The drop checker works by the gaseous CO2 crossing into the test solution. Since nitrate is an ion, not a gas, it will not move through the air. However, a semi-permeable membrane between the aquarium and a test solution could be used. Unfortunately, the nitrate ion doesn't undergo simple reactions which result in a reversible color or color change.


Swylie: The only people making ISE's are those who are trying to design new/better ISE's - it's not a good DIY project.

Kevin

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72g bowfront planted, CO2, 4x - T5HO, Eheim 2213 and 2217, 2 angels, pristella tetras, blue tetras, betta, albino bristlenose pleco, albino cories. Sword, vals, hygros, ludwigias, java moss and fern, anubias

2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.
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