Alkalinity Standard?

[Johnson556]

For alk I have been using my Hanna checker for almost two years. I am not as concerned with where the number is as I am the consistency of that number appearing. I have been having my hanna checker read 7.5/7.6 dKH for months now and exactly where I want it.

I just opened up a new reagent. I did one last test with the old reagent then another test immediately following with the new reagent. There was a .5 dKH difference (7.1 dKH). Concerned over the number I tested with a Salifert kit and got a reading of 8.5 (tested 3 times). Now if my Alk was actually 7.1 dKH I would fine with that as my system is a lower nutrient system (No3 2-4PPM / Po4 0.01-0.02). However, 8.5 or above could lead to some problems.

My question is, is there a standard solution out there that is set at a specific dKH I could use to verify each reagent I open. I would love to have a liter of some solution that is 100% certain to be 8dKH.

Is there anything like this available or is it possible to make your own?

 

[Dr. Reef]

https://hannainst.com/hi755-11-marine-alkalinity-checkerr-hc-calibration-set.html

 

[Johnson556]

https://hannainst.com/hi755-11-marine-alkalinity-checkerr-hc-calibration-set.html

Thanks but that just to check the checker. By standard solution I mean a solution I actually go through the testing process with where I know the dKH of the water beforehand.

More so to verify my reagent than the actual checker.

 

[Dr. Reef]

how are you going to test that?
There is not going to be a solution premixed in saltwater for you to test. It wont be shelf stable.
There are 1000 ppm or 500 ppm solutions out there but when you mix it with saltwater it will alter the alk and if you put it in rodi water it wont be accurate in marine hanna checker.

Only way you can be certain about your reagent being good is to test the same reagent on someone else fish tank. Let your fellow hobbyist use his checker to run a test on his water. get a result. then use your reagent to test his water using his checker.
If your reagent is good then both results should be very very close. (remember checker has a 5ppm+-)

 

[Johnson556]

I didnt even consider the saltwater aspect of things when it comes to the standard.

I was just assuming that if I have a solution that is known to be 8dKH, I fill the two viles, put the reagent in one and test like I would with tank water to understand where my reagent is off.

 

[Dr. Reef]

true, it wont be as simple as putting solution in vial and test. Atleast i am not aware of such lets see what others have to say.
But like i said earlier.
If you have 2 checkers and 2 reagents and sample of same water you can test your reagent.
Fellow hobbyist can help run a test using his checker and reagent on his water. Say he get 8 dkh. then using his checker and his vials and his water run your reagent and get a result. If its within 7.95-8.05 dkh range your reagent is good.

 

[JimWelsh]

There is not going to be a solution premixed in saltwater for you to test. It wont be shelf stable.

Surely you jest. I have to link a Google-cached copy of the site because of the current government shutdown, but stable alkalinity standards certainly exist: https://webcache.googleusercontent....+&cd=3&hl=en&ct=clnk&gl=us&client=firefox-b-1

 

[Dr. Reef]

good to know but can one purchase such a solution?
I wasnt aware of a solution that would be premixed in saltwater to be compatible to test in a marine checker.

 

[JimWelsh]

Yes, Dickson's CRM is available for sale (at least when we have a functioning government, that is), but is crazy expensive, having 6 significant figures of accuracy, and all that.

There is the "Tropic Marin Multi-Standard", which is much less expensive than the Dickson CRM, but it still pretty pricey when you consider how small the bottle is.

I've often wondered what sort of demand there would be for a product like this, considering that I'm all tooled up to create such standards with great accuracy, as a result of my work on the original Alkalinity Monitor ("AMI" as Neptune calls it), and also the Trident project.

 

[atp0726]

My Salifert is always 1 DKH higher than my Hanna. Took a sample to LFS and they checkedit using Red Sea and it came out .4 above Hanna. For now I am going with Hanna, I have heard others complain Salifert is high. I prefer the Hanna any day over the others, maybe get a 3rd test kit with decent reputation like Red Sea to see how close it is to the Hanna.

I have also noticed the Hanna starts to read higher as you get low on reagent.

 

[jbrady429]

There is Two Little Fishies’ AccuraSea product.

 

[JimWelsh]

There is Two Little Fishies’ AccuraSea product.

I almost listed that product too, but they don't state any specific numbers for anything other than salinity.

 

[Johnson556]

There is Two Little Fishies’ AccuraSea product.

Bingo, only if they stated the dKH...

I know they say "nsw parameters at 35ppt" but I dont see anything that gives me a precise dKH, just 7-11dKH

 

[jbrady429]

I almost listed that product too, but they don't state any specific numbers for anything other than salinity.

I received the following information from them via email a year ago:

“AccuraSea Seawater reference solution is made from natural seawater, and verified to be at a salinity of s = 35.

The values for calcium, magnesium, and alkalinity in natural seawater are commonly reported at the standard s=35, so we can be sure that the values in our product match the standard levels found in natural seawater.

calcium 412 mg/l

magnesium 1290 mg/l

alkalinity 2.5 meq/l”

 

[JimWelsh]

I received the following information from them via email a year ago:

“AccuraSea Seawater reference solution is made from natural seawater, and verified to be at a salinity of s = 35.

The values for calcium, magnesium, and alkalinity in natural seawater are commonly reported at the standard s=35, so we can be sure that the values in our product match the standard levels found in natural seawater.

calcium 412 mg/l

magnesium 1290 mg/l

alkalinity 2.5 meq/l”

Yeah, but NSW @ 20C and S=35 has 419.2 mg/L of Ca and 1315.6 mg/L of Mg, and 2.37 meq/L of Alkalinity, per "An Introduction to the Chemistry of the Sea", Pilson, Second Edition.

The Ca and Mg numbers they cite appear to be the mg/kg values, rather than the mg/L values @ 20C (well, sort of -- Pilson says 411.5 and 1284, respectively). I find that people citing "standard values found in natural seawater" frequently fail to adjust for the difference between mg/kg and mg/L.

If the Accurasea cited number for alk were to be increased proportionally to adjust for the 1.024763 specific gravity @20C, then it would become more like 2.56 vs. Pilson's 2.37. Dickson's very careful work produces values that are very consistently in agreement with Pilson's 2.37 meq/L.

This deference to the "standard levels found in natural seawater" without empirically testing means that the alkalinity value of this "standard" might be anywhere from 6.6 to 7.2 dKH!

EDITED: I transposed digits in the Dickson alk value in the earlier post. I edited to fix that.

 

[jbrady429]

Yeah, but NSW @ 20C and S=35 has 419.2 mg/L of Ca and 1315.6 mg/L of Mg, and 2.37 meq/L of Alkalinity, per "An Introduction to the Chemistry of the Sea", Pilson, Second Edition.

The Ca and Mg numbers they cite appear to be the mg/kg values, rather than the mg/L values @ 20C (well, sort of -- Pilson says 411.5 and 1284, respectively). I find that people citing "standard values found in natural seawater" frequently fail to adjust for the difference between mg/kg and mg/L.

If the Accurasea cited number for alk were to be increased proportionally to adjust for the 1.024763 specific gravity @20C, then it would become more like 2.56 vs. Pilson's 2.37. On the other hand, if we were to look to Dickson's very careful work, his salinity-adjusted values are very consistently more like 2.79 meq/L.

This deference to the "standard levels found in natural seawater" without empirically testing means that the alkalinity value of this "standard" might be anywhere from 6.6 to 7.8 dKH!

All very good points. In addition, whatever the alkalinity (and other values) happen to be in a given bottle, they won’t change in time (if the bottle is stored properly). 500ml will last a long time if used as a reference for hobbyist tests on occasion.

 

[Larry L]

I've often wondered what sort of demand there would be for a product like this, considering that I'm all tooled up to create such standards with great accuracy, as a result of my work on the original Alkalinity Monitor ("AMI" as Neptune calls it), and also the Trident project.

DO IT! :-)

 

[jbrady429]

All very good points. In addition, whatever the alkalinity (and other values) happen to be in a given bottle, they won’t change in time (if the bottle is stored properly). 500ml will last a long time if used as a reference for hobbyist tests on occasion.

I forgot to point out that this approach would make AccuraSea work as a "relative" standard rather than an absolute reference (it could be used to see if your test is giving different results than it used to, but not to check its absolute accuracy). I realize that this is slightly off of the original point of the thread--sorry for the slight tangent.

 

[Sherman]

Many brand has Ref solution. I am using DSR Ref solution to calibrate all my test kit

 

[JimWelsh]

I forgot to point out that this approach would make AccuraSea work as a "relative" standard rather than an absolute reference (it could be used to see if your test is giving different results than it used to, but not to check its absolute accuracy). I realize that this is slightly off of the original point of the thread--sorry for the slight tangent.

Along these lines, *any* seawater solution would be able to serve this purpose provided that it was sufficiently preserved & correctly stored.