NO3 vs N-NO3

PiXieCath

PiXieCath

Premium Member
Hi! I ask myself about the unites regarding to nitrates testing. Is the results are usually given in NO3 or in N-NO3?

I know that we have to multiply N-NO3 by 4.4 for having the real NO3 values but I'm a bit confused now...I've always tested with Salifert NO3 test kit and my results are below 5ppm. Now, I'm currently testing a new kit and if I look at the N-NO3 scale, I've the same results than the Salifert test...but if I look at the NO3 scale, my results are a bit higher than 20ppm. So, the real question is: Do I have below 5ppm or under 20ppm of nitrates?:hmm4:

Mr. Holmes-Farley: Can you explain me quickly why NO3 are higher in concentration that the N-NO3? I've always tough that it was the opposite...
 
Salifert measures Nitrate not NO3-N.
No need to adjust Salifert measurement.

Test kits that measure in NO3-N do need to be multiplied by 4.4 to get the total NO3 value.
 
People at RC almost always quote total nitrate, not nitrate nitrogen. The salifert kit is total nitrate last I saw.

Nitrate nitrogen is simply the weight of nitrogen present, while total nitrate counts the weight of the oxygen atoms as well. :)

This has more:


The Units of Measure of Reefkeeping
http://reefkeeping.com/issues/2005-08/rhf/index.php


from it:


ppm-N (part per million nitrogen)
also ppm nitrate-N, ppm nitrite-N, ppm-ammonia-N

ppm-N is a way to measure nitrogen atoms in solution. It is equal to the ppm concentration of nitrogen atoms, and usually specifies what form they take. It is often used, for example, to describe the concentration of ammonia, nitrite, or nitrate ions in aquaria. It can also be used to describe the amount of nitrogen in dissolved organic matter (DOM), particulate organic matter (POM), or total organic matter (TOM) in seawater. In these cases, the results are reported as nitrate = 12 ppm-N" or 12 ppm nitrate-N, which means that there is 12 ppm of nitrogen in the solution is in the nitrate form.In order to convert ppm-N to ppm, divide the ppm-N value by the fraction of weight of nitrogen in the ion. The table below shows these corrections:

Species...ppm-N...ppm

NH3 (ammonia)...1.00...1.21

NH4+ (ammonium)...1.00...1.29

NO2- (nitrite)...1.00...3.29

NO3- (nitrate)...1.00...4.43
 
RegalAngel said:
Salifert measures Nitrate not NO3-N.
No need to adjust Salifert measurement.

Test kits that measure in NO3-N do need to be multiplied by 4.4 to get the total NO3 value.
Click to expand...

Yeah, I know about it but my real question is why I get 4.4 more ppm than Salifert in a test who claim to mesure the NO3 level?lol
 
Do they mesure N-NO3 and thinking they mesure NO3? The first reactive contain cadmium, the second probably an indicator and the third contain acetic acid (combination of the 2 last reactives remind me something like the Griess reactive)...
 
Randy Holmes-Farley said:
No. The units of measure have nothing to do with the reaction used.

Nitrate kits are notoriously inaccurate, IMO. :)
Click to expand...

Hihi, ok!:D

But is there possible that the scale was inversed? For example: The NO3 were ranged from 0 to 6 ppm and the N-NO3 units from 0 to 1.4? I'm a bit confused!lol
 
It is not likely (IMO) that the Salifert kit mistakenly uses units of nitrate-nitrogen without saying so, if that is the question. Salifert is familiar with the units and understands them, and notes the ranges on their web site:

"Many nitrate test kits are prone to amine interference. This can give results much lower than actual.
The Salifert nitrate test does not suffer from such an amine interference. The very special ingredients allow a very fast and precise measurement.
The range spans from very low to a very high nitrate concentration (approx. 0.05 – 20 mg/L as Nitrate-Nitrogen or 0.2 – 100 mg/L as nitrate ion).
The kit can perform approx. 60 measurements."


That said, there may be a translation issue in your directions that is confusing you somehow into getting the wrong interpretation.

The owner of Salifert (Habib Sekha) pops in here from time to time, so perhaps he'll comment.
 
No, my question isn't about Salifert, it's about the other test kit.;-) Is it normal that the unit in ppm-N were lower than the ppm? (ex, 3ppm for 0.7 ppm-N) Or it's me who don't understand?lol
 
Humm...unfortunely, I can't tell since it's a brand new test who haven't been release yet...but maybe you can pm me to talk about it...
 
Last edited:
Anyway, in order to understand a bit more...if the results are in N-NO3, do I have to multiply or to divide by 4.43 to have the NO3 concentration?
 
PiXieCath said:
Thanks RegalAngel, I've already read you.;-) But what is confusing me is this quote from Randy Holmes Farley:

In order to convert ppm-N to ppm, divide the ppm-N value by the fraction of weight of nitrogen in the ion. The table below shows these corrections:

Species...ppm-N...ppm

NO3- (nitrate)...1.00...4.43
Click to expand...

Ok...I now understand that 1ppm have to be divided by (14(weight of N)/(16*3(weight of O3)+14)...so, 14/62=0.22581...and 1ppm/0.22581=4.43!:spin1:

But my question is still pending...ok, I understand that a test can give a different result that another one, at this point, it's usual...but it look strange to me that the kit I'm currently testing always give fourth time the NO3 concentration that the one I am confident in it(Salifert)... For me, it look like the result is in N-NO3 instead of in NO3 and that the manufacturer haven't made the difference between both...
 
You might be right about the manufacturer not giving the correct units, but you'll have to contact them for instructions. Either of your test kits might just be inaccurate, or both could be.
 
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