How to make alkalinity standards?

[Miami Reef]

I use Red Sea Alkalinity Pro titration. I tested my parameters the same time I collected my ICP sample and the ICP stated that my tank was 10.38dkh while my notes state that it was 9.6dkh.

Phosphate (Hannah ULR PPB) states 0.04ppm while the ICP states 0.08ppm.

I don’t think these values are in the stated accuracy. I know there are phosphate standard for the Hannah kit, but I’m curious about making/buying an alk standard. Thanks!

 

[shakacuz]

ICP are more “lab grade” from my understanding. our hobby level test kits are not as accurate so it seems.

abc reagents seem like a very recent, cheap, alternative to the other standards sold and used. maybe give it a shot?

 

[Randy Holmes-Farley]

It's easy to make or buy an alk standard for a normal alkalinity titration.

But the Hanna method may need the sample to be a seawater solution, and that is much harder to DIY.

 

[Randy Holmes-Farley]

ICP are more “lab grade” from my understanding. our hobby level test kits are not as accurate so it seems.

Maybe the ICP company is just using hobby kits. lol

It cannot come from ICP itself. It's a different test of some sort.

 

[Miami Reef]

It's easy to make or buy an alk standard for a normal alkalinity titration.

But the Hanna method may need the sample to be a seawater solution, and that is much harder to DIY.

Do you have an article for a recipe? I’d love to make a standard! I consider myself a very good titrator. And the Red Sea alk claims an accuracy of 0.14dkh (0.05meq/l)

 

[Randy Holmes-Farley]

We discuss DIY alk standards here:

DIY alkalinity standard

For folks who may want to evaluate the accuracy of their alkalinity test kits, here are two suggested ways to do it. One is DIY and one is a mostly commercial standard with one DIY step. Method 1 Standard solutions could be made with sodium bicarbonate, but it can be hard to be sure it hasn't...

www.reef2reef.com

If you want to use sodium hydroxide instead of sodium carbonate, you use less sodium hydroxide, so use 0.755 times the amount of sodium carbonate in that recipe.

 

[Miami Reef]

We discuss DIY alk standards here:

DIY alkalinity standard

For folks who may want to evaluate the accuracy of their alkalinity test kits, here are two suggested ways to do it. One is DIY and one is a mostly commercial standard with one DIY step. Method 1 Standard solutions could be made with sodium bicarbonate, but it can be hard to be sure it hasn't...

www.reef2reef.com

If you want to use sodium hydroxide instead of sodium carbonate, you use less sodium hydroxide, so use 0.755 times the amount of sodium carbonate in that recipe.

Thanks so much. I’ll keep you guys posted in this thread (I’m leaving out of town for 5 days so it will be done when I’m back home).

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing!

 

[PatW]

Heck, you could make up a stock solution of ALK using the stuff Bulk Reef Supply sells. Then use the calculator to make a standard ALK solution to your target level add the amount of stock to a gallon of RODI or water made to 35 ppt using NaCl. Even if you use crude methods like cup measures, the standard should be within about 5% accurate. And that is accurate enough for reefing. It does not really matter that much if you off some. As long as you know that you are at 7.6-8.4 that is good enough on an absolute level. What you want to track is relative change.

Of course, if you get a decent scale, you can easily make a calibration solution that would be accurate within 1% and that exceeds the accuracy of any hobby test.

 

[Randy Holmes-Farley]

Heck, you could make up a stock solution of ALK using the stuff Bulk Reef Supply sells. Then use the calculator to make a standard ALK solution to your target level add the amount of stock to a gallon of RODI or water made to 35 ppt using NaCl. Even if you use crude methods like cup measures, the standard should be within about 5% accurate. And that is accurate enough for reefing. It does not really matter that much if you off some. As long as you know that you are at 7.6-8.4 that is good enough on an absolute level. What you want to track is relative change.

Of course, if you get a decent scale, you can easily make a calibration solution that would be accurate within 1% and that exceeds the accuracy of any hobby test.

Two issues are:

1. how much moisture is in the additive, Hence the drying step in the procedure I posted

2. I would not assume the Hanna will read alk correctly in 35 ppt NaCl plus bicarbonate. The issue relates to the pKa of bicarbonate and carbonic acid in the solutions of interest.

 

[Miami Reef]

I’ve been waiting ALL week to accomplish this.

First, I work in a gold jewelry store, and I am the “expert” in calibrating all the scales and ensuring everything is accurate.

To make the standard I took a 2L bottle of coke. I rinsed with tap many many times until I was sure it was clean.

Then I took freshly made 0 TDS RO/DI and rinsed to come bottle a few times to ensure it is properly “zerod”

Then, I calibrated my 0.1 accuracy scale. I measured by using the specific density of water 1mL water = 1g.

I weight 1,000 grams of water.

Then, I got my freshly baked (1 hour at 400F) sodium carbonate and weighed 10 grams and added to the 1,000g water solution.

Once mixed, I took 15.1g of that solution and made a total of 1,000g (filling the remaining with RO/DI water).

This gave me a final 1,000g solution of 8dkh.

I used my Red Sea test kit and this is 8dkh.

It’s the first ever slight change to the color. I thought it needed to be completely green. That means that my Alkalinity was lower than what I tested it out to be.

This is the color I usually wait until (only took one drop more so it is 8.25dkh if you wait until that color)

What I infer from this is that the Red Sea Alkalinity Pro test it is highly accurate.

I also inferred that in this specific case, the ATI ICP was not accurate.

Thoughts? @Randy Holmes-Farley

 

[Randy Holmes-Farley]

I’ve been waiting ALL week to accomplish this.

First, I work in a gold jewelry store, and I am the “expert” in calibrating all the scales and ensuring everything is accurate.

To make the standard I took a 2L bottle of coke. I rinsed with tap many many times until I was sure it was clean.

Then I took freshly made 0 TDS RO/DI and rinsed to come bottle a few times to ensure it is properly “zerod”

Then, I calibrated my 0.1 accuracy scale. I measured by using the specific density of water 1mL water = 1g.

I weight 1,000 grams of water.

Then, I got my freshly baked (1 hour at 400F) sodium carbonate and weighed 10 grams and added to the 1,000g water solution.

Once mixed, I took 15.1g of that solution and made a total of 1,000g (filling the remaining with RO/DI water).

This gave me a final 1,000g solution of 8dkh.

I used my Red Sea test kit and this is 8dkh.

It’s the first ever slight change to the color. I thought it needed to be completely green. That means that my Alkalinity was lower than what I tested it out to be.

This is the color I usually wait until (only took one drop more so it is 8.25dkh if you wait until that color)

What I infer from this is that the Red Sea Alkalinity Pro test it is highly accurate.

I also inferred that in this specific case, the ATI ICP was not accurate.

Thoughts? @Randy Holmes-Farley

That seems like a reasonable conclusion, but I’m not sure if alk changes in a sealed up icp sample for some reason.

 

[rtparty]

AFAIK, ATI uses a titration alkalinity test. I highly doubt it's any better than what we can do at home.

It's an added "benefit" they test alkalinity but I don't use to make adjustments on my tank. I let my own testing determine all that because I want to see trends and am not super concerned with accuracy. I need reliable and repeatable. If my alkalinity is actually 7 instead of 8, I don't worry about that. I just want to stay around my 7 and I'm good.