Repurpose Hannah copper checker?

[Red2143]

Here's what I came up with. I'm making two assumptions.
1) that Lot-to-Lot variation isn't too bad.
2) that the HR Cu checker is the same as the LR Cu checker, just reads 5x darker solutions to go up to 5ppm instead of 1000ppb=1ppm.
(I'll be able to check assumption 1, but not the assumption about the two checkers, somebody else will have to test that.)



The curve calculation is [ppm NO3] = 7.00 [Cu checker] - 0.3

Method (same as standard API, scaled up to 8mL volume):
8.0mL sample water in hanna cuvette
16 drops reagent 1
cap on, invert cuvette 10x
(follow API directions about aggressively shaking reagent bottle 2)
16 drop reagent 2
cap on, shake cuvette hard for 1:00 minute
wait 5:00 minutes (6:00 min total from start of the shake)

make the yellow blank (can be done before or during the 5:00 minute wait)
add 8.5mL sample water to another hanna cuvette
16 drops of reagent 1
cap on invert 10x
(no reagent 2)

Use the yellow blank as C1 in the Cu checker, and the reacted sample as C2.
the yellow blank is how you get zero NO3 to read as zero on the checker, and probably lower a little of the lot-to-lot variation.

Thank you for doing this, very interesting. Is it possible to half the recipe to save on reagent? If so, would the formula still apply and then you multiply by 2?

 

[taricha]

Here's what I came up with. I'm making two assumptions.
1) that Lot-to-Lot variation isn't too bad.

This assumption isn't looking great.
I think @Dan_P ran into this before with API NO3 that maybe each new kit needs its own calibration curve. He had worked a version that reduced down the concentration of reagants. I was hoping that running them full strength, then everything would just be in large excess and the color formation would be pretty similar from lot to lot and one bottle to the next.
But maybe NO3 tests are more finicky than that and even in reagent excess, the ratios etc end up mattering. Thoughts @Dan_P ?
My old API NO3 kits look pretty different from each other in color production (like one is twice another). I'm going to check what a new out of the box kit looks like, but at the moment - not optimistic.

 

[Randy Holmes-Farley]

This assumption isn't looking great.
I think @Dan_P ran into this before with API NO3 that maybe each new kit needs its own calibration curve. He had worked a version that reduced down the concentration of reagants. I was hoping that running them full strength, then everything would just be in large excess and the color formation would be pretty similar from lot to lot and one bottle to the next.
But maybe NO3 tests are more finicky than that and even in reagent excess, the ratios etc end up mattering. Thoughts @Dan_P ?
My old API NO3 kits look pretty different from each other in color production (like one is twice another). I'm going to check what a new out of the box kit looks like, but at the moment - not optimistic.

Do you know if its the background that rose, or the nitrate peak height minus background?

 

[taricha]

My old API NO3 kits look pretty different from each other in color production (like one is twice another). I'm going to check what a new out of the box kit looks like, but at the moment - not optimistic.

Do you know if its the background that rose, or the nitrate peak height minus background?

Yeah, the size of the NO3 response (measured at 575nm with Cu checker) is just not similar from one kit to the next.

(kit C not going through zero,zero might mean I goofed one of the points, but regardless this is enough data to tell me that the kit variation is large enough that a calibration curve done with one Lot won't be useful to predict another lot.)

Left is my kit C at 4,8 and 12ppm NO3. Right is kit D on the same 4, 8, and 12 ppm samples.
Both kits were brand new and shaken mercilessly (more than instructions) to ensure uniformity within the bottles. And my kit A (not pictured) looks like the yellow background of kit D, but with twice the Red NO3 response rate. There's simply way too much reagent variation in the bottles to make this sort of thing work for API NO3.
No point in attempting anything more precise than eyeballing against a color card here.

(this is not the case with API ammonia or NO2, which are very repeatable - but NO3 seems trickier.)

 

[Dan_P]

This assumption isn't looking great.
I think @Dan_P ran into this before with API NO3 that maybe each new kit needs its own calibration curve. He had worked a version that reduced down the concentration of reagants. I was hoping that running them full strength, then everything would just be in large excess and the color formation would be pretty similar from lot to lot and one bottle to the next.
But maybe NO3 tests are more finicky than that and even in reagent excess, the ratios etc end up mattering. Thoughts @Dan_P ?
My old API NO3 kits look pretty different from each other in color production (like one is twice another). I'm going to check what a new out of the box kit looks like, but at the moment - not optimistic.

Those dogs at API do not have rigid quality control on reagent strength lot to lot. This only shows up under the modified test conditions using less reagent/less intense color and the use of a photometer like the Checker. This means that I buy 4 kits of the same lot and tweak the ratio of reagents for that particular lot. The upside is I get about a million tests of comparable accuracy as Hanna HR

By the way, the API NO3 test and the Hanna HR Marine nitrate test seem to be low metal/reductant formulations. This means they can be variable or touchy about contamination. I have devoted vials for only the Hanna HR and API nitrate tests. This seems to have eliminated those annoying low test results (variability).

 

[Red2143]

Those dogs at API do not have rigid quality control on reagent strength lot to lot. This only shows up under the modified test conditions using less reagent/less intense color and the use of a photometer like the Checker. This means that I buy 4 kits of the same lot and tweak the ratio of reagents for that particular lot. The upside is I get about a million tests of comparable accuracy as Hanna HR

By the way, the API NO3 test and the Hanna HR Marine nitrate test seem to be low metal/reductant formulations. This means they can be variable or touchy about contamination. I have devoted vials for only the Hanna HR and API nitrate tests. This seems to have eliminated those annoying low test results (variability).

How does one go about tweaking the ratio? If possible it would be very helpful for a list of steps or recipe to follow

 

[Dan_P]

How does one go about tweaking the ratio? If possible it would be very helpful for a list of steps or recipe to follow

Sure. Let me look up my latest adjustments and lot numbers.

 

[Dan_P]

How does one go about tweaking the ratio? If possible it would be very helpful for a list of steps or recipe to follow

Have you consider Red Sea? It is a bit more expensive but the lot to lot consistency might be better (I have not used enough to confirm this)

 

[Red2143]

Have you consider Red Sea? It is a bit more expensive but the lot to lot consistency might be better (I have not used enough to confirm this)

I'll have to look into that since earlier it was established the Hanna nitrate reagent wouldn't work either

 

[Dan_P]

I'll have to look into that since earlier it was established the Hanna nitrate reagent wouldn't work either

OK.

Some background on adjusting the color intensity of the API nitrate test. First of all, the quick, color intense hobby kits use much more reagent reagent than necessary. For example, the latest lot that I am using only needs 4 drops of reagent A (the yellow solution) and 6 drops of reagent B ((the clear reducing agent) for a 10 mL test sample compared to the recommended 8 drops each for a 5 mL sample. This particular ratio gives a color intensity similar to the Hanna Marine HR reagent and works well with that Checker.

The adjustment of color intensity is most strongly affected by reagent A. B produces a somewhat weaker effect but is it is important not reduce this reagent too much relative to A as the test can fail at high nitrate concentrations because of the depleted reducing agent in B.

A starting ratio for you might be 4:6 with 1 minute shaking and 10 minutes of color development time. I can go into more detail if you wish.

 

[Red2143]

OK.

Some background on adjusting the color intensity of the API nitrate test. First of all, the quick, color intense hobby kits use much more reagent reagent than necessary. For example, the latest lot that I am using only needs 4 drops of reagent A (the yellow solution) and 6 drops of reagent B ((the clear reducing agent) for a 10 mL test sample compared to the recommended 8 drops each for a 5 mL sample. This particular ratio gives a color intensity similar to the Hanna Marine HR reagent and works well with that Checker.

The adjustment of color intensity is most strongly affected by reagent A. B produces a somewhat weaker effect but is it is important not reduce this reagent too much relative to A as the test can fail at high nitrate concentrations because of the depleted reducing agent in B.

A starting ratio for you might be 4:6 with 1 minute shaking and 10 minutes of color development time. I can go into more detail if you wish.

Is the goal a particular color saturation and then you have to run a calibration curve with each new bottle?

 

[Dan_P]

Is the goal a particular color saturation and then you have to run a calibration curve with each new bottle?

Yes. The goal is get the color saturation to work with your Checker and calibrate each new lot. When you run your tests, use several Checkers to measure the color intensity, just in case one is better.

 

[Red2143]

Yes. The goal is get the color saturation to work with your Checker and calibrate each new lot. When you run your tests, use several Checkers to measure the color intensity, just in case one is better.

Thank you. It's turning out to be a bit more complicated than a simple swap of reagents. How would I make different level calibrations solutions?

 

[Dan_P]

Thank you. It's turning out to be a bit more complicated than a simple swap of reagents. How would I make different level calibrations solutions?

Are you asking about the procedure for making dilutions, e.g., 0.5, 1, 1.5 ppm nitrate?

 

[Red2143]

Are you asking about the procedure for making dilutions, e.g., 0.5, 1, 1.5 ppm nitrate?

Yes but maybe higher too

 

[taricha]

Red Sea NO3 in a hanna HR Cu checker is already a done thing.
@Rick Mathew did it and generated this calibration curve....

In fact, it looks like Rick may already have done this years ago.
This is regression data for measuring Red Sea NO3 with a hanna HR copper checker.

Rick's approximate regression is about [NO3 ppm] = 6.0 x [Cu checker ppm].

@Red2143 you may give that a try.

 

[Red2143]

Red Sea NO3 in a hanna HR Cu checker is already a done thing.
@Rick Mathew did it and generated this calibration curve....

Thank you

 

[Dan_P]

Yes but maybe higher too

No problem.

Very briefly, you will need to make a nitrate standard which means a supply of pretty good sodium or potassium nitrate, a balance to weigh it and a reasonably accurate way to measure liquid volumes. The stock solution is then diluted to each of the concentrations that you want want to measure. I stress “reasonably accurate” because we just need a good estimate for happy fish and coral.

 

[Red2143]

No problem.

Very briefly, you will need to make a nitrate standard which means a supply of pretty good sodium or potassium nitrate, a balance to weigh it and a reasonably accurate way to measure liquid volumes. The stock solution is then diluted to each of the concentrations that you want want to measure. I stress “reasonably accurate” because we just need a good estimate for happy fish and coral.

If I have some potassium nitrate powder what is the math to create a 10ppm solution or similar?

 

[Dan_P]

If I have some potassium nitrate powder what is the math to create a 10ppm solution or similar?

The nitrate mass in potassium nitrate contributes 62/101 to the total mass. When you weigh out 1 g of potassium nitrate, there is about 0.61 g NO3. To make a 10 ppm solution, you would weigh out 101/62 x 10 mg of potassium nitrate.

In reality, you would make a 1000 ppm solution, to avoid weighing tiny amounts of material, and dilute a small portion to 10 ppm. For example, if you need 100 mL of 10 ppm nitrate, dilute 1 mL of 1000 ppm to 100 mL.

Since the test is designed for salt water, use freshly prepared saltwater for your dilute solutions. The 1000 ppm stock solution can be prepared in RODI or distilled water.

This was a rather brief summary. Happy to fill in with more details.