A DIY Alkalinity Reference for Hanna?

[creas]

I'm hoping someone can help me find a DIY recipe for an Alk reference that I can test with my Hanna meter. I thought I remembered seeing one but I can't find it. I had been using Salifert Alk test for years and decided to try the Hanna. The current Salifert test (and the last one) gave me results from 8.0-8.6 DKH depending on when I tested but the first 2 Hanna tests were both 7.39 and were taken on 2 separate days. I'd like to verify the Hanna before I start making adjustments. Any advice?

 

[Tennsquire]

I'm hoping someone can help me find a DIY recipe for an Alk reference that I can test with my Hanna meter. I thought I remembered seeing one but I can't find it. I had been using Salifert Alk test for years and decided to try the Hanna. The current Salifert test (and the last one) gave me results from 8.0-8.6 DKH depending on when I tested but the first 2 Hanna tests were both 7.39 and were taken on 2 separate days. I'd like to verify the Hanna before I start making adjustments. Any advice?

My Salifert Alk test kits came with a reference solution. I've used that to check my Hannah Checker, and it was pretty close.

 

[JimWelsh]

How accurate do you want this DIY alkalinity standard to be?

 

[creas]

My Salifert Alk test kits came with a reference solution. I've used that to check my Hannah Checker, and it was pretty close.

I'll have to check and see if my kit had one, I don't recall.

 

[creas]

How accurate do you want this DIY alkalinity standard to be?

I think the more accurate the better, at list within +/- of the test.

 

[JimWelsh]

I think the more accurate the better, at list within +/- of the test.

Of course more accuracy is better. I was asking you to quantify this.

If you want an accurate DIY alkalinity standard, then you will need accurate tools. Do you have (or are you willing to get) a volumetric flask, say 1000 mL, and a milligram scale?

 

[creas]

I do have a millagram scale and would be willing to buy said flask if it's possible to achieve a consistent and accurate standard. I also work for a company that manufactures industrial cleaners and have or have access to more chemicals than average, if that matters. I will eventually do a Triton test and compare my numbers but was looking for something that I can use at the house.

 

[Randy Holmes-Farley Verified Community Expert]

Since the Hanna is not an alkalinity titration, I think any standard needs to be a seawater mimic and not a normal alkalinity standard.

 

[JimWelsh]

Since the Hanna is not an alkalinity titration, I think any standard needs to be a seawater mimic and not a normal alkalinity standard.

Then that complicates things, but perhaps not as much as you might think. I guess we need to add a pH meter calibrated with 4.0 and 7.0 pH standards and a little HCl to the list of items we need to have on hand.

 

[JimWelsh]

I do have a millagram scale and would be willing to buy said flask if it's possible to achieve a consistent and accurate standard. I also work for a company that manufactures industrial cleaners and have or have access to more chemicals than average, if that matters. I will eventually do a Triton test and compare my numbers but was looking for something that I can use at the house.

Triton doesn't measure alkalinity.

 

[creas]

Then that complicates things, but perhaps not as much as you might think. I guess we need to add a pH meter calibrated with 4.0 and 7.0 pH standards and a little HCl to the list of items we need to have on hand.

I have the pH meter and solutions to calibrate and HCl (31.5%) but am I overly complicating this? What would you do in this situation? Assuming the reagent is good should I trust that the Hanna checker is the more accurate of the two tests?

 

[JimWelsh]

What would you do in this situation? Assuming the reagent is good should I trust that the Hanna checker is the more accurate of the two tests?

Well, now that's a different question. I would assume the Salifert is the more accurate of the two, by far.

If you still want to discuss a DIY alkalinity standard, I'm still game to go down that path as well.

 

[creas]

Well, now that's a different question. I would assume the Salifert is the more accurate of the two, by far.

If you still want to discuss a DIY alkalinity standard, I'm still game to go down that path as well.

So, tell me what this involves? I may be willing to go this route just for the learning experience.

 

[Randy Holmes-Farley Verified Community Expert]

I suspect, but do not know for sure, that the method works something like this:

A rapid and accurate spectroscopic method for alkalinity measurements in sea water samples
http://www.sciencedirect.com/science/article/pii/S0043135498001687
https://www.researchgate.net/public..._alkalinity_measurements_in_sea_water_samples

"The authors propose a new spectrophotometric method for the determination of sea water alkalinity. The method consists to neutralize all the basic species taken into account in the alkalinity expression by a weak acid (formic acid) mixed with a pH sensitive dye, the Bromo-Phenol Blue, which has a dissociation constant close to those of formic acid. The neutralization reaction leads to a final mixture having an absorbance at 590 nm which is a function of the original alkalinity of the sample. "


I do not know how low they take the pH, or how sensitive it is to the pKa of bicarbonate. To be most accurate, one would make a seawater mimic solution, at least with NSW levels of sodium, chloride, sulfate, magnesium, and calcium. Those are the ones that mostly impact the pKa of bicarbonate and carbonate, and so should present a good control for how much the pH should drop with a fixed amount of acid added. Table 1 in the article shows the seawater mimic solution they used. I don't think the potassium is important. It is too low in concentration and too like sodium to make a difference.

 

[JimWelsh]

Edited too long post nobody was going to read anyway.

 

[Bruce Burnett]

Hanna makes a standard http://www.bulkreefsupply.com/hi755...rds-for-hi755-hanna-checker-marine-water.html

 

[JimWelsh]

That is an absorbance standard for the colorimeter. It isn't an alkalinity standard. It verifies that the Hanna hardware works correctly (to within 10%). It won't help identify issues with your reagent, nor will it allow you to compare the Hanna to another method, such as Salifert.

 

[Bruce Burnett]

That is an absorbance standard for the colorimeter. It isn't an alkalinity standard. It verifies that the Hanna hardware works correctly (to within 10%). It won't help identify issues with your reagent, nor will it allow you to compare the Hanna to another method, such as Salifert.

Thank you, I made the assumption he was looking to verify his Hanna, did not consider that he was looking to check his reagents. I have always had a Red Sea alkalinity test kit to compare results if my Hanna seemed off. I am definitely not a chemist not even close. I only test my tank alkalinity about once a month now, as long as everything is looking good and growing.