Salifert Test Kit and Hanna Checker Results for Alkalinity

[David S]

Greetings All,

Despite my aversion to the Phosphate Checker by Hanna as alluded to in a previous thread, I couldn't resist purchasing their Alkalinity Checker as it was on sale for a very reasonable price.
And unlike the Phosphate Checker which has received mixed reviews, the Alkalinity Checker has received predominately positive feedback.
So I've been using it for nearly two weeks now for a total of 5 tests.
At the time of these tests, I also tested with my Salifert test kit, which I've used for some time - as a means of comparison (I also have a Red Sea kit which I've used, but since it's hard to determine the end point, I don't rely on it).
The results have been interesting, in that in all 5 tests the results for the Hanna Checker has exceeded the Salifert result by 0.4 DKH.
So there is a definite consistent relationship between the two tests, which I see as a good thing.
Which one is actually more accurate remains to be seen.
For now, however, I'm leaning to the Salifert as being closer to accuracy.
The reason being is that I was running low on my Salifert kit and ordered a new one. When it arrived, I compared the results from the new one with the old one. They were identical.
My current parameters are Salifert 7.4 and Hanna 7.8 DKH. Samples of this water have already been packaged and will go out to ATI for analysis.
Hopefully I'll get results by early next week.
Right now I'm encouraged by the "consistency" between the two tests and am assuming (for now) that my true Alkalinity is within that range.
I'll have more to say after I see the results

David

 

[Randy Holmes-Farley]

One thing that can impact the answer you get from an alkalinity titration is the color you elect for the endpoint.

Have you checked to see what the color is with the salifert kit when you go another 0.4 dKH, and whether it too might match?

 

[jsker]

The thing I like about the Hanna's is the fact that there is not the color charts involved. I have tested and keep another alk test kit to check the Hanna if I test is drastically off. There is a slight difference and that could be just up to the testers end point and color determination I terms the color tests are in the eyes of the beholder

I my experience if have found the Alk tests and the phosphate tests to have the most variances between test kits and tests

 

[pecan2phat]

Agreed with Randy!
Is it purplish pink or pink with a tinge of orange, still scratching my head over that, Lol.

 

[David S]

One thing that can impact the answer you get from an alkalinity titration is the color you elect for the endpoint.

Have you checked to see what the color is with the salifert kit when you go another 0.4 dKH, and whether it too might match?

You bring up an interesting point.
According to the instruction on the old or new kits you add dropwise until the color changes from blue/ green to orange/red or pink whichever color shows up first.
It has been my experience that there is a point where the color is still predominately blue green but there is a hint of pink. usually one more drop causes the solution to turn pink , albeit a faint pink and that's what I've been using as my endpoint.
But in response to your query, I just did a test and realized that while I was going with the first sign of a predominant pinkish color, there was still signs of blue/green in the solution. In point of fact, it took two additional drops to have the solution go totally pink, with no evidence of blue/green (adding additional drops made the coloration a bit more intense, but it does not change to orange/red).

So I then tested and the results were Salifert 8.3 Hanna 8.1
Obviously those extra few drops made quite a significant difference.

Thanks Randy

 

[David S]

I had a bit of a mishap yesterday.
I had filled my test vials and left them on the table. Several hours later I was preparing to seal the bag when I noticed water seeping from the bag. It turned out one of the Aquarium test vials was not closed enough and the water seeped out.
I thought I twisted the vial shut, but apparently it wasn't tight enough. I would suggest that anyone using the ATI test make sure the cap for the vial is twisted very tightly.
Anyway, I had to retest my parameters and my ALK results based on the Salifert Test was 7.3 (down for 7.4 from the original test). I did not retest with the Hanna Checker, but based on the "old" way I was interpreting the Salifert test it is probable that the Hanna result would have been approximately 7.7 (down from 7.8)

 

[David S]

OK, I received the results from ATI this morning.
Not what I would have expected.
They show a DKH of 6.84. This is well below what either the Salifert test kit and Hanna Checker indicated.
Quite frankly, I give more credence to the Salifert/Hanna results as they are very close and have been consistent.
You can check my other thread "why I stopped using Instant Ocean" for comments on the overall testing.

 

[JimWelsh]

I just did a test and realized that while I was going with the first sign of a predominant pinkish color, there was still signs of blue/green in the solution. In point of fact, it took two additional drops to have the solution go totally pink, with no evidence of blue/green

FWIW, those two additional drops were overshooting the endpoint. I describe the correct endpoint as having a sort of "lavender" hue:

 

[David S]

Oh Boy
That was about what I was using for my original endpoint.
But at Randy's suggestion I started using the point where it goes totally pink.
When I use that as my result it matches up closely to the Hanna Checker.
I have sent a message to Salifert on Facebook so we'll see what they say.

 

[Jason mack]

Interesting thread !!

 

[guido5526]

I have done the same test between red sea, salifert and hanna, just picked up hanna alk checker this last weekend and compared to the other two, hanna reading 7.6, and had red sea actually come in the same reading, I have also sent a test off to triton and wanting to see which is closer, I did notice that the hanna checker has a .3dkh variance. which most of the time ive had the other two come in reading within that variance. im wanting to do the triton method almost to a T and wanted a accurate tester as I could not always trust the red sea alone. I had the first batch of titrate go bad within the first year. had to battle with red sea to get new and the end color doesn't even come close to the card.

 

[Randy Holmes-Farley]

Oh Boy
That was about what I was using for my original endpoint.
But at Randy's suggestion I started using the point where it goes totally pink.
When I use that as my result it matches up closely to the Hanna Checker.
I have sent a message to Salifert on Facebook so we'll see what they say.

lol

In my defense, I don't know the colors with this kit as i haven't used it for more than a decade.

I just asked "Have you checked to see what the color is with the salifert kit when you go another 0.4 dKH, and whether it too might match?"

 

[David S]

FWIW, those two additional drops were overshooting the endpoint. I describe the correct endpoint as having a sort of "lavender" hue:

Just to clarify, I had been using the end point that you suggest; which basically shows the first hint of a pinkish color, I would get a 0.4 discrepancy, on a consistent basis, between the Salifert test and the Hanna Checker, the Hanna Checker being higher.
But then when I test to the point where it looks totally pink (as the 1st result on the right) the results are within 0.1 of each other.
I'm therefore hoping that is the correct way. Otherwise there is a problem with the Hanna Checker (or the reagent).
Hopefully Salifert will be able to give us some guidance.

BTW it would be nice if these test kits had a definitive end point, that is not open to interpretation.
FWIW there are a few that have a definite endpoint, that I might mention:
One is Salifert's Potassium test kit. It's a slightly extended test, but the end result is an unmistakable "baby blue" color. As far as accuracy goes, my test indicated 430 mg/l and ATI was 441 mg/l.
Another one which you definitely need patience with is the Red Sea Test Kit for Magnesium, however your patience is rewarded if you add drops slowly and once it turns blue you wait a few seconds and wait to see if it changes to a violet color. Then you know you've reached your endpoint. (If you miss it you can add drops forever.)
However, in comparison with my last 2 ICP tests the Red Sea was 100+ mg lower than the ICP results.
The trick with both tests is not to overshoot your target.

 

[JimWelsh]

Anecdotally, the Hanna Checker does seem to give high readings when compared to other methods for a large number of people, it seems, based on various forum posts both on Reef2Reef and also other forums. My take (for what that's worth) on the Hanna Checker is that it seems to have reasonable precision, but poor accuracy.

 

[David S]

lol

In my defense, I don't know the colors with this kit as i haven't used it for more than a decade.

I just asked "Have you checked to see what the color is with the salifert kit when you go another 0.4 dKH, and whether it too might match?"

Yes and it was a good question.
I would go with the first hint of pink - the instructions say "...adding dropwise until the color changes from blue/green to orange/red or pink color (whichever comes first).
First off, I have never noticed a change to orange/red. It's always pink.
Secondly, it doesn't indicate whether it's just a hint of the color or it should be a complete change.
Originally, I went with the first hint of the color and I would always be below Hanna by ~0.4. If I continue adding drops until the color completely changed they were within ~0.1

 

[David S]

I have done the same test between red sea, salifert and hanna, just picked up hanna alk checker this last weekend and compared to the other two, hanna reading 7.6, and had red sea actually come in the same reading, I have also sent a test off to triton and wanting to see which is closer, I did notice that the hanna checker has a .3dkh variance. which most of the time ive had the other two come in reading within that variance. im wanting to do the triton method almost to a T and wanted a accurate tester as I could not always trust the red sea alone. I had the first batch of titrate go bad within the first year. had to battle with red sea to get new and the end color doesn't even come close to the card.

Really LOL
I have the Red Sea Alkalinity kit, as well.
You will note, however, I didn't include it.
For good reason. This test is the antithesis of the test kits that give definitive, if not accurate results.
For those who haven't used this kit it shows a bold orange color for an endpoint on a laminated card.
You do the test by taking your sample water and adding an orange colored reagent drop by drop.
Initially the water in the vial will turn blue. You keep on adding the reagent and eventually the blue is replaced by a faint but noticeable orange color. However, the color is not indicative of what is on the card . So you keep adding drops and although the intensity of the color increases somewhat, it never seems to match the intensity displayed on the card, resulting in a bit of subjective guesswork.

 

[David S]

Really LOL
I have the Red Sea Alkalinity kit, as well.
You will note, however, I didn't include it.
For good reason. This test is the antithesis of the test kits that give definitive, if not accurate results.
For those who haven't used this kit it shows a bold orange color for an endpoint on a laminated card.
You do the test by taking your sample water and adding an orange colored reagent drop by drop.
Initially the water in the vial will turn blue. You keep on adding the reagent and eventually the blue is replaced by a faint but noticeable orange color. However, the color is not indicative of what is on the card . So you keep adding drops and although the intensity of the color increases somewhat, it never seems to match the intensity displayed on the card, resulting in a bit of subjective guesswork.

I have done the same test between red sea, salifert and hanna, just picked up hanna alk checker this last weekend and compared to the other two, hanna reading 7.6, and had red sea actually come in the same reading, I have also sent a test off to triton and wanting to see which is closer, I did notice that the hanna checker has a .3dkh variance. which most of the time ive had the other two come in reading within that variance. im wanting to do the triton method almost to a T and wanted a accurate tester as I could not always trust the red sea alone. I had the first batch of titrate go bad within the first year. had to battle with red sea to get new and the end color doesn't even come close to the card.

BTW Triton does not test for Alkalinity

 

[Big E]

FWIW, those two additional drops were overshooting the endpoint. I describe the correct endpoint as having a sort of "lavender" hue:

I use this same endpoint, but then I go to the pink and use the number that falls in between. This to me is the median. It's where the numbers would line up when I compared Saliferts readout to a LaMotte kit.

I did it this way also because the difference between the changing color point and all pink would be only one droplet.

Been doing it this way for about 5 years.

If I went to the pink the Salifert would always read .5 higher consistently.

In the end I don't think it matters much if you give yourself a low cushion. I'm more concerned with consistency than overall accuracy.

 

[guido5526]

BTW Triton does not test for Alkalinity

ha, whoops guess I didn't read through the list of parameters tested well enough. must have thought that they tested it since they talk about keeping alk between 7.8 and 8 in the triton guide. good to know. either way im waiting for BRS to get the base elements back in stock so I can begin dosing it.

 

[Hanna Instruments]

Anecdotally, the Hanna Checker does seem to give high readings when compared to other methods for a large number of people, it seems, based on various forum posts both on Reef2Reef and also other forums. My take (for what that's worth) on the Hanna Checker is that it seems to have reasonable precision, but poor accuracy.

Just to clarify, I had been using the end point that you suggest; which basically shows the first hint of a pinkish color, I would get a 0.4 discrepancy, on a consistent basis, between the Salifert test and the Hanna Checker, the Hanna Checker being higher.
But then when I test to the point where it looks totally pink (as the 1st result on the right) the results are within 0.1 of each other.
I'm therefore hoping that is the correct way. Otherwise there is a problem with the Hanna Checker (or the reagent).
Hopefully Salifert will be able to give us some guidance.

BTW it would be nice if these test kits had a definitive end point, that is not open to interpretation.
FWIW there are a few that have a definite endpoint, that I might mention:
One is Salifert's Potassium test kit. It's a slightly extended test, but the end result is an unmistakable "baby blue" color. As far as accuracy goes, my test indicated 430 mg/l and ATI was 441 mg/l.
Another one which you definitely need patience with is the Red Sea Test Kit for Magnesium, however your patience is rewarded if you add drops slowly and once it turns blue you wait a few seconds and wait to see if it changes to a violet color. Then you know you've reached your endpoint. (If you miss it you can add drops forever.)
However, in comparison with my last 2 ICP tests the Red Sea was 100+ mg lower than the ICP results.
The trick with both tests is not to overshoot your target.

Hello,

Thank you for using our products!

On the HI772 dKH Alkalinity Checker the accuracy statement = Accuracy @ 25°C/77°F ±0.3 dKH ±5% of reading

So if your Checker reads 10.0 dKH the measure of uncertainty would be ±0.5 dKH or a range from 9.5-10.5 dKH.

If 5% of the total reading is great than 0.3 dkH then the use the 5% as your accuracy. If 5% of your total reading is equal to or less than 0.3 dKH then use 0.3 dKH as your accuracy statement.

We tested our HI772 dKH Checkers in the lab against a popular brand of test kits used by most reef hobbyist with our Automatic Potentiometric Titrator - HI901C.

Test results were as followed:

Saltwater was obtained from an established reef aquarium.

Reef Chemical Test Kit: 7.2 dKH
HI772 dKH Checker: 6.28 dKH
HI901C Automatic Titrator: 6.05 dKH

Automatic Titrators are widely considered one of the most accurate and precise ways for alkalinity determination.

We also tested varies batches of our reagent lots. There was minimal variability (~6 ppm) between the two Checker reagent lots (#6551 and #6712). This variability is within the accuracy statement of the Checker (+/- 5 ppm +/- 5% of reading).

A big advantage for using a Hanna Checker is there little subjectivity in the process of analysis. We have a very simplified alkalinity test, there are no color changes to determine or drops to count. This leads to a higher rate of repeatable success and precision . The colorimetric method is a well-established method used by various producers of alkalinity testing equipment. Although it is not a standard method like SM 2320B it still has yielded successful results for hundreds of thousands of reef keeping hobbyists across the globe. We do sell sulfuric acid and high grade pH electrodes/meters so and if a hobbyists chooses they can always titrate with sulfuric acid down to a 4.5 endpoint (which is the EPA method).

http://hannainst.com/0-01-m-sulfuric-acid-1l-hi70458.html

http://hannainst.com/hi12302-halo-ph-electrode-with-bluetoothr-smart-technology.html

Titrate 50mL of water with the 0.01M H2SO4 to pH 4.5 with a calibrated meter. Then, take the mL of titrant used x 1.121= dKH alkalinity. If you have a 7.5 dKH tank, that should be about 8-10mL, meaning the one bottle of $16.00 sulfuric acid will last you for about 100 tests. Alternatively, you could do the titration to pH 4.2, a popular seawater variant.