Alkalinity Standard?

[TellyFish]

I recently bought an Hannah alk checker and the results I am getting are higher than I was expecting. The checker is reading 188ppm while my lamotte test kit is reading around 130ppm.

Given the large disparity, and the fact that I am unsure which figure is most likely to be correct, I was considering purchasing an alk standard such as this: http://www.poolweb.com/Shop-On-Line/Reagents-Other/ALKALINITY-STANDARD-100-PPM-16-OZ-

Any thoughts on something more easily obtainable (and cheaper) that I can test as a standard?

[hedgedrew]

I use lamotte and usually get accurate results. I also use elos and. They vary from bottle to bottle. Newer ones higher. I wonder if reagents go bad. Get new lamotte blue pills.

[TellyFish]

Thanks Drew, the reagents have been replaced relatively recently. To be honest, I am more suspect of the electronic meter.

Would be really great to know if my lamotte kit is accurate by testing it against a standard of some sort.

[TimeConsumer]

Salifert kits come with a reference sample.

[hedgedrew]

You know about this 10 per difference between salt water and fresh kits? Some kits made esp for marine like salifert will read 10 per higher than others. You could be looking at that.

[hedgedrew]

Although 10 per is 140 ish still seems high. I have a alk checker i dont use. Im going to check it vs lamotte. Will let you know.

[TellyFish]

Salifert kits come with a reference sample.

That could work... although I was hoping to find something laying around the house that would have a standard alkalinity. Too much to ask?

[hedgedrew]

Salifert has that ref solution

[bertoni]

Making a reference solution requires a high-precision scale. A pharmacist might have one. This thread gives a recipe:

http://www.reefcentral.com/forums/showthread.php?t=1325571

[Spyderturbo007]

If you lived closer, I would make one for you. I have everything you need in my lab.

[hedgedrew]

Telly. I can confirm that lamotte and elos read 140 ppms ans hanna alk checker reads 159 165. About what i expected

[TellyFish]

If you lived closer, I would make one for you. I have everything you need in my lab.

First, thank you that is very kind to offer. Also, I appreciate anyone who does anything in 'my lab'. Sounds awesome.

Second, do you have any documentation that would describe this process? Is this a task someone could perform in a 'makeshift' lab?

[TellyFish]

Telly. I can confirm that lamotte and elos read 140 ppms ans hanna alk checker reads 159 165. About what i expected

This wasn't what I was expecting to hear. Your saying this result is normal/expected?

[hedgedrew]

Yes. Some of the kits test 10 per higher. I think hanna and salifert probably match. And elos and lamotte match

[hedgedrew]

There are old threads somewhere on rc explaining the difference in the tests.

[TellyFish]

Thanks for the information, i'm searching for the old thread.

Forgive my ignorance, with two completely different readings, how do we know which level is the 'correct' one?

[bertoni]

The titration endpoint for saltwater and fresh water differ, so a kit calibrated for freshwater will read a bit low, by about 10%, I think.

[hedgedrew]

Most time weather you run tour alk at 8 or 8.8 it doesnt matter. Itsvthe stability that matters and keeping it from fluctuating.

[TellyFish]

The titration endpoint for saltwater and fresh water differ, so a kit calibrated for freshwater will read a bit low, by about 10%, I think.

So it sounds like the Lamotte test kit is calibrated for freshwater, while the Hannah Checkers are for salt?

[TellyFish]

Most time weather you run tour alk at 8 or 8.8 it doesnt matter. Itsvthe stability that matters and keeping it from fluctuating.

Understood but I am getting a reading of 8 on one test and 10.5 on the other. I am trying to determine if I should adjust the alk levels at all.

[bertoni]

Either level is fine. I personally would leave the level as is.

[hedgedrew]

Which kits are low and high again? Hanna is high righ .?

[hedgedrew]

I would get new reagents with lamotte and just use that and realize it maybe 10 per low. Or alternatively go out and buy a salfert kit. I know they calibrated for salt and see if it matches hanna.

[Spyderturbo007]

First, thank you that is very kind to offer. Also, I appreciate anyone who does anything in 'my lab'. Sounds awesome.


Thanks. Sometimes it is and sometimes it isn't. :fun4:


Second, do you have any documentation that would describe this process? Is this a task someone could perform in a 'makeshift' lab?

Unfortunately not. The issue would be trying to find an analytical balance with the resolution required to measure such a small amount of chemical. I just had to order one the other day and it ran $3,634.50 and that is with our discount from Mettler.

Anyway, you could always check the phone book for a local lab and ask if they would weigh something for you so you can make a standard for your aquarium. For a few bucks they might make you up a standard. It would only take a few minutes and the Sodium Carbonate is cheap. That's provided it is something they use and already have on hand. You don't want to have to spend the money to buy a kilogram when you only need less than a gram.

[TellyFish]

Which kits are low and high again? Hanna is high righ .?

Correct, the Hannah checker is running 2.5DKH or about 50ppm higher than the Lamotte kit.

[TellyFish]

The issue would be trying to find an analytical balance with the resolution required to measure such a small amount of chemical.

I find this very interesting, thank you for humoring me with this conversation.

Can I assume that purchasing a used analytical scale is a total crap-shoot and that calibrating one is probably very costly?

If I were to contact a local lab, what exactly would I request? Simply ask if they can mix me an alkalinity standard to 100ppm?

[TimeConsumer]

Really, you could just buy a Salifert kit for $15 and use the check solution it comes with. It has enough solution for 2 or 3 tests, enough for you to figure out at what point in the titration color change you reach the true reading. I understand wanting to make something from materials at hand, but once you're at the point of calling labs and buying scales, might as well just shell out the $15 and call it a day.

[Jamey1010]

lol I offered to send him one free but appears to be died set on making one or at least understanding how

Really, you could just buy a Salifert kit for $15 and use the check solution it comes with. It has enough solution for 2 or 3 tests, enough for you to figure out at what point in the titration color change you reach the true reading. I understand wanting to make something from materials at hand, but once you're at the point of calling labs and buying scales, might as well just shell out the $15 and call it a day.

[TellyFish]

Thanks guys, I ordered a salifert kit.

Jamey, that is awesome that you offered to ship me the sample for free. You are the reason this hobby has such an amazing community.

...and yes I would love to understand more about the process involved in creating your own standard. I know very little about chemistry (why did I choose to take physics instead, why?!?!) and I am trying to learn more. I also love to do things myself, often to a fault ;)

[TellyFish]

lol I offered to send him one free but appears to be died set on making one or at least understanding how

Also curious for those in the know... will a bottled alk standard stay accurate for months/years? Or will it start to deviate with evaporation, time, etc...

[bertoni]

It will start to lose accuracy with evaporation. That's about it.

[BrentH]

Ive had the opposite my hanna reading lower the my read sea by about 70 ppm curious to see how this turns I was leaning towards the hanna being more accurate ....

[Spyderturbo007]

I find this very interesting, thank you for humoring me with this conversation.


No problem. :D


Can I assume that purchasing a used analytical scale is a total crap-shoot and that calibrating one is probably very costly?

I've purchased used equipment for my lab before and never had much of an issue. Most laboratories are reputable and I don't see them trying to take advantage of you. The issue is that even when used, analytical balances are still pretty expensive.

Calibration can be done one of two ways. All analytical balances contain a reference weight housed inside the balance along side the load cell. The balance has an internal adjustment that will correct for things like temperature, humidity, load cell wear, etc. Most manufacturers label it as "calibration" but that's not entirely correct.

An actual balance calibration from an ISO 17025 company will run you $112/balance along with a $78 documentation fee. I'm sure the price would be much higher when just calibrating one balance because of travel and fuel surcharges. I get a discount and don't have to pay for travel because I have 19 balances which takes them 2 days to calibrate.

The calibration involves checking the balances Eccentricity, Linearity, Sensitivity and Repeatability. Any adjustments or repairs are then carried out by the technician and are normally done using the service menu of the balance.

Anyway, it would be way too expensive to purchase your own balance, have it calibrated, and then purchase your own chemicals and glassware.



If I were to contact a local lab, what exactly would I request? Simply ask if they can mix me an alkalinity standard to 100ppm?

I would ask for one around 150ppm, but yes, that's all you would need to do. If they can't figure out how to do that, then you probably don't want them making you a standard. :lolspin:

[TellyFish]

Thanks for the info. Ill update this thread in a week or so...

[hedgedrew]

Let us know telly. We continue to get same results. Hanna is 10 per more than lamotte. Lamotte and elos are the same. My hunch is salifer will match closervto hanna but i think yours is reading too high

[TellyFish]

I received the Salifert Alkalinity test as well as a 6.7 DKH standard check solution.

<a href="http://s1184.photobucket.com/user/tellyFish/media/alkKit_zps1ddcf327.jpg.html" target="_blank"><img src="http://i1184.photobucket.com/albums/z332/tellyFish/alkKit_zps1ddcf327.jpg" border="0" alt=" photo alkKit_zps1ddcf327.jpg"/></a>

My numbers are:

Lamotte (6mos old) - 140ppm
Hannah Checker (2 year old) - 180ppm +
Salifert (New) - 155ppm

I now believe my 'correct' value is aprox 8.6DKH.

The new Salifert seems to be consistently 10-15ppm higher than the Lamotte, which is expected.

Hedgerew is also correct in assuming the Hannah checker is reading too high. I just finally ran out of reagent and it is actually pretty old the expiration date was 5/12. I suspect this could be the issue.

I am going to replace the Hannah reagent HI755S and let you know what I get.

<a href="http://s1184.photobucket.com/user/tellyFish/media/checkerTube2_zps6b3788e5.jpg.html" target="_blank"><img src="http://i1184.photobucket.com/albums/z332/tellyFish/checkerTube2_zps6b3788e5.jpg" border="0" alt=" photo checkerTube2_zps6b3788e5.jpg"/></a>

[wayne in norway]

I'd agree the Lamotte and Salifert are behaving as you'd expect. My Hanna checker correlates with my Salifert, but I don't have the batch number with me.

[bertoni]

The Hanna should be running about 10% higher than the LaMotte, I think, because the LaMotte likely is calibrated for freshwater use. 50 ppm is a bit high, though.

[TellyFish]

The Hanna should be running about 10% higher than the LaMotte, I think, because the LaMotte likely is calibrated for freshwater use. 50 ppm is a bit high, though.

50ppm is way high IMO. I believe my Hannah checker is either damaged or the reagent is expired.

Agreed, the Lamotte kit is designed for freshwater and thus is off by 10%.

[bertoni]

Well, one of the kits seems to be wrong. :) I probably would get a new set of reagents for the Hanna and work from there.

[TellyFish]

Well, one of the kits seems to be wrong. :) I probably would get a new set of reagents for the Hanna and work from there.

Agreed, in this case the Hannah Checker is wrong.

[hedgedrew]

Good job! In italy now but nice to hear.