Didn't do it myself but it want on a Seal AA3 Auto-Analsyer measuring NH3, NO2, DIN, PO4. Triplicate samples from each tank 3 times a week. NO3 range was 0.5 to 5 uM approx
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Few problems with my little slice of nature!
- Thread starter EA James
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PARAGUAY
Member
I gave up testing for nitrate with the API the process is a bit laboured and easy to error and the coloration too similar for wide margins. I think it's useful for the basic testing ammonia and nitrite
Hi all,
cheers Darrel
That seems fair enough.
Perfect, but also sort of the point. The <"auto-analyser is using colorimetry and cadmium reduction">. It is designed for use in a water testing lab., with a high throughput of samples, and automates a lot of what the lab. scientist would do.
I won't do all the calculations, but a quick bit of approximation (somebody could check?), has the RMM of NO3 is 62, so a molar solution is 62g of NO3 made up to one litre, and one micromol. is 62 * 10^-6, and your top NO3 level was about 0.3 mg/L (ppm).
cheers Darrel
Hi @dw1305
Are you saying that ICP-OES cannot accommodate the range of freshwater conditions? Test labs don't appear to mention this - are they hiding something? I'd be interested to know more.
JPC
Hi @PARAGUAY
I use the JBL Nitrate Test Kit. I make up my own reference solutions and I think this test kit is pretty good. Its low-level resolution is excellent. Today, I was using it and it registers the difference between 3 ppm and 5 ppm.
JPC
Hi all,
Freshwater is much more variable and a lot less salty.
ICP works best where you have a constant run of samples, it uses argon (Ar) as the carrier gas, and you have a constant flow through of Ar even when the machine isn't running sampes, which gets expensive pretty quickly.
I don't know how much a commercial lab. would charge to run a freshwater sample, but I'm going to assume it is three figures.
cheers Darrel
You can use it for any solution, the only reason is that sea water is both a very salty solution and pretty standard across the globe. This means that you have a known datum value for Na+, Ca++ etc. and just have to look for differences from that datum.
Freshwater is much more variable and a lot less salty.
ICP works best where you have a constant run of samples, it uses argon (Ar) as the carrier gas, and you have a constant flow through of Ar even when the machine isn't running sampes, which gets expensive pretty quickly.
I don't know how much a commercial lab. would charge to run a freshwater sample, but I'm going to assume it is three figures.
cheers Darrel
Hi Darrel,
Does NO3 test kit mesure NO3- only or NO3- + NO2- ? When reduction of NO3- to NO2- is done, its seems that we are back to NO2- test. Is the second reagent of NO3 test kit able to "mesure" NO3- only ?
Hi all
That is partially why I don't particularly like NO3 testing, it has a lot of steps where things can go wrong.
Cheers Darrel
Yes, it is usually a two phase process, you measure the nitrite (NO2-), and then you reduce the NO3- to NO2- and take the first value from the second one to give you the nitrate reading.
That is partially why I don't particularly like NO3 testing, it has a lot of steps where things can go wrong.
Cheers Darrel
MichaelJ
Member
Darrel, even if you are excruciatingly careful following the directions, these tests can often be way off and/or very hard to interpret.
Case in point; this is an NO3 test I did awhile ago using the API Nitrate test kit in one of my tanks (a low TDS soft water tank using 100% remineralized RODI water, and very clean and healthy):
What is the reading? lets say its 40 ppm - as I believe the reading was trying to tell me... depending on the light I was using I could sway myself into saying closer to 80ppm .... In any event, there is just no way this tank got 40-80 ppm of NO3 - a far more realistic number at that time would have been somewhere around 10ppm which would have been fairly consistent with my dosing and some inevitable buildup at the time.
Cheers,
Michael
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John q
Member
MichaelJ
Member
Sure. Some test kits I believe in, some I do not - I can only speak to the API kits which I have used occasionally over the past few years:
API NO3: Mostly bunk! Wildly off and/or extremely hard to gauge.
API PO4: Mostly bunk! Wildly off and/or extremely hard to gauge.
API NH3+NH4: I suppose this might give you a reasonable guideline if you factor in temperature and pH and correctly derive the amount of toxic free ammonia (NH3).
API pH kit seems reasonably accurate for all practical (low-tech) purposes. Probably wont be precise enough for dialing in CO2.
API GH: For the 2-7 GH range I've been working in using 0.5 resolution (2 drops per GH) its fairly accurate and consistent with my CaSO4/MgSO4 remineralization dosing.
API KH: Helpful but tricky 🙂 - Clive explains this 🙂
Cheers,
Michael
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