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Re: Nitrate test kits
> Date: Sat, 9 Aug 1997 22:42:13 -0700 (PDT)
> From: Andy Dilbert <ixtapa at geocities_com>
> Subject: Nitrate test kit brand
> Hello all,
> I am trying decide which nitrate test kit to buy, but I don't understand
> what factors are important. Also, I don't know which brand is of higher
> quality. This is what I know of each:
> SeaChem: Measures down to 2 mg/L. Performs 75 tests. Tests Nitrite, too.
> Red Sea: Performs approx 70 tests. $7.99
> Kordon: Range of 0-30 ppm. Scale reads 10, 20, 30. ?Performs 10 tests? $7.99
> Tetra: Range of 0-100 ppm. Scale reads 0, 12.5, 25, 50, 100. Performs 40
> tests. $8.99
When comparing the ranges of different tests, keep in mind that some may
be reporting nitrate as NO3, while others report it as the equivalent
concentration of N. That creates a factor of 4.4 difference between tests
on identical samples. I think the Tetra kit reports the concentration as
NO3. _If_ the Kordon kit reports it as N, then the Kordon's maximum value
at 30 ppm would be 132 ppm on the scale used by the Tetra.
Nitrate can go very high in poorly maintained and/or heavily fed tanks,
and readings above 100 mg/l as nitrate would be possible. For planted
tanks we should have much lower values, and a kit with a maximum value of
22 ppm as NO3 (or 5 ppm as N) would be useful. Kits with even lower
maximums would produce useful results.
> I think that the SeaChem sounds like a pretty good deal, considering it
> tests both nitrate and nitrite. Red Sea does the most tests for the buck.
> I left out LaMotte because it alone would bust my budget! ;) Does anyone
> know which brand is the best?
> Thank you very much for any replies!
> - -Andy
I once read into the standard wet chemical methods used to analyse
nitrate. Nitrate is actually a tough analysis, so it doesn't surprise me
that the test kits sometimes give flaky results. The most common method
for analysing nitrate actually analyses nitrate+nitrite. That's because
the technique reduces nitrate in the sample to nitrite in order to analyse
it, so both the nitrate and any nitrite that was originally in the sample
are "caught" by the analysis. The lab method used cadmium metal (danger!
danger!) as the reductant. Some of the kits use metal particles in a
shake-and-wait step (Tetra, and at least one other - it may have been
Kordon), and the color scales in the nitrate tests look awfully similar to
the color scales in nitrite tests.
The point to all that is that I don't think SeaChem is unique in analysing
nitrate and nitrite. Several of the others - possibly all of them - may
analyse both nitrate and nitrite, but report the sum as nitrate in order
to avoid the confusion.
I have Tetra and Aquarium Pharmaceuticals Nitrate kits. The Tetra kit
consistently reports higher values than the AP. I've also used another
kit (Kordon?) and it seemed to confirm the Tetra results, so I suspect the
Tetra kit gives better results than the AP. The Kordon(?) produced its
results in shades of brown, and despite the nice "color cube" comparator,
it was tough to read.
The best reputation belongs to Hach. I talked to them recently and priced
their nitrate kits. I don't remember now what the price was, but it
struck me at the time as reasonably priced, at least when compared to
their iron and hardness kits. Unfortunately, Hach ships via UPS. I
talked to them just after the start of the UPS strike and they claimed to
already be backlogged by 2 weeks. I'm not sure how they got backlogged by
two weeks in just two days, but that's what they claimed.