Accurate NO3 Test with Hanna ULR P Checker

(I got this concept - and the first data - from Dan_P. )
Short version:
Take Red Sea NO3 test, develop it, run it through the Hanna ULR P checker.
Calculate your NO3 as follows
(ppm NO3) = 0.00765 x (Hanna reading) + 0.117

Now for the details. First, take the tank water and precisely dilute it down to 1/10 of original with some trusted total zero NO3 source - I've use distilled water mostly. From now on this 1/10 dilution is the "sample."
I use the Red Sea NO3/NO2 kit that calls for 5ml sample. Double the sample and all reactants so I have 10ml, 10 drops A, 2 scoops B etc. During the 9 min developing time, I use another 10ml (diluted) sample water as the blank "C1" in Hanna checker. Then empty it, and pour in the developed pink red sea test into the Hanna cuvette as "C2". I time it so that Hanna checker runs "C2" right at the 9 min development time of the Red sea test - start the 3 min countdown at 6:00 into development time - easy.
Do all the normal obsessing about bubbles and smudges that we love about Hanna checkers.
Put the readout from Hanna into that formula above. This gives the sample NO3 concentration in ppm. The Hanna checker is very sensitive and will only read NO3 concentrations between ~0.1 and ~1.5 ppm. This is why the first step is to get a 1/10 dilution so a normal reef tank running anywhere between 1ppm and 15ppm will get a reading.

Data details
Below are the data sets that were generated from known mixed NO3 solutions. Blue is the first data from Dan_P using a different Red Sea NO3 kit (Nitrate pro reef) he scaled down to give 10 mL of sample. (Dan's directions at bottom of post)

Red, Orange and Green are my sample series from different stocks I mixed. As you can see there's as much variation between my different data runs as there was between mine and Dan's data. I take that to mean it's probably not crazy to lump it all together.
So here it is - X and Y flipped now.

That trend line is y = 0.007653*x + 0.1169 which is where the formula came from. Note that getting the NO3 prediction from the Hanna reading (trend line) and then comparing that to the actual known concentration would give you an error in every case of 0.1ppm or less.
average error between the line and a known concentration point= 0.048ppm and 5.3% of value (for larger values).
At the extremes - 0.1ppm, you run a 50/50 risk of hanna reading "0" and at 1.6ppm, a 50/50 risk of the meter maxing a flashing "200"
Will this trend hold as tightly for other people as it did for Dan and myself? Give it a try let us know what you think! If you have access to accurate methods for mixing known concentration solutions you can help improve the fit line or find a breakdown in the method.

Dan's instructions for the Red Sea Nitrate Pro kit.

 

Very nice work!! I may have to try this.

 

Me too! Very interesting and thank you for sharing. I'll have to give it a try too!

 

Very nice.

My son had been using a couple of my Hanna checkers as fixed wavelength spectrophotometers for some activated carbon studies using methylene blue and molasses as challenge agents. He had to go through the same process you did - including determining which checker had the best absorption response.

Thanks for shared.

 

Yep! Hanna lists the wavelengths for each checker.
The Hannah ULR P is a 525nm green light and quite sensitive. The red sea pink absorbs green really strongly. Gives pretty good detection.
I imagine the 525nm would also be absorbed decently by test kits that turn blue.

 

Lemme throw this out there. Two problems with what I did that are reasons this maybe shouldn't work.
1. diluting to 1/10 with distilled water and Red Sea says it wasn't designed for freshwater.
from Red Sea FAQ

I take "slightly brighter" to mean more pink ought to be produced?

2. Dan's instructions here

The solid particulates that you can see after the addition of "reagent B" and shake 1 min step are supposed to interfere with color formation - giving an artificially low result.
there's definitely still particulates at that step, and if you look closely you can see bubbles. I didn't have a filter in yet, so I did all this without.

Not sure why I haven't seen the expected errors from these shortcuts.

 

Diluting with rodi is described in the Nitrate Pro directions. If you need a high range test, they advise to dilute 1ml sample water with 15ml rodi.

 

That is for a different test. The test used in this case is different

 

OP quoted Red Sea "Can I use the Nitrate Pro and Phosphate Pro tests kits on R/O water?"
I was pointing out Red Seas own directions for the Nitrate Pro kit indicated you can dilute saltwater. Maybe it does not work well on pure RODI, but I guess dilute saltwater is ok per the directions.

 

Ok, this discussion made me realize I may be adding a totally unnecessary amount of reagents.
The Marine nitrate/nitrite test kit calls for 5ml sample, five drops of A, one scoop B one scoop C - tests up to over 20ppm (color card goes to 50ppm). The nitrate Pro kit calls for 16 ml sample, 5 drops A, 1 scoop B, 1 Scoop C - tests up to 4ppm.
So I doubled everything (sample and reagents) in my marine no3/no2 kit to get 10ml, and Dan_P scaled everything down to get 10ml proportional to the 16ml recipe from the nitrate pro kit.
And we got essentially the same trend line with me using like 3x the reagent concentration.
Am I thinking this through right - that I really only need reagents in proportion to the NO3, not the mL of sample?

 

Can this be done whit salifert?
Would love to know!
Thanks

 

What color does it turn? If it's red/pink then absolutely, a similar method - probably different formula - would work.
If it's another color, then although it may work, a different wavelength LED would be better.

For instance, later I'd like to look into using the 610nm Orange LED of my Low Range Silica tester to quantify the blue in Seachem Iodine test.
That won't be relevant to nearly as many people though.

 

Meaning that lower reagent concentration may have lower reaction rate - longer time?
The Nitrate Pro test - which uses the lower concentration - I think the directions allow a little more time in a step or two.

 

So would there be any reason you couldn't use the Nitrate Pro as directed (16ml or 1:15 dilution) and pull 10ml of the sample to read at 9min? I'm sure each would need it's own graph...

 

Speculation until data backs it up, but it probably won't even need its own graph.
I mean, the data so far has lined up pretty tight even though I was using about 3x the reagent concentration that Dan did. In the first post, his data in blue and mine from the other 3 lines don't look different enough to me to justify a different fit line.

(to be more precise, the variation within my data with the same method and test kit looks as big as the variation between our different methods and test kits - hence the different methods and test kits are likely not the source of the variation.)

 

Yes it turns pink.
Can anyone test what formula would be to sur please?
To bad im not a chemist...