Possible Hanna Magnesium Checker solution?

[REEFCRAFT]

Update. Nevermind. This testing kit is useless and no one should use it for testing their mag, ever.

 

[jrill]

If that's the solution then Hanna has some serious problems in production or engineering.

 

[Dan_P]

I saw this posted today on the lizard boy social media app by SaltwaterAquarium.com. Perhaps a few of us could try this and show your results.

What reference standard was used to be able declare spot on results?

 

[taricha]

What reference standard was used to be able declare spot on results?

It's an interesting issue. Every kit is known as being "high" or "low" or "spot on", but I've never seen anyone use a standard except what a salt mix ought to be when mixed to a measured target salinity,

 

[JimWelsh]

I've never seen anyone use a standard

Yeah, but you've never seen me work in my lab, either.

CaCl2*2H2O and MgCl2*6H2O reagent grade salts made up to slightly over 1.0 M in 18 Megohm water, then analyzed by an Anton-Paar DMA5000 densitometer, cautiously diluting until the density reaches the value at 20C specified by the CRC Handbook for each compound. Both solutions are then validated using a Mohr titration to verify chloride content, as well as standardization with an EDTA primary standard solution. These solutions are mixed with 18 Megohm water to create, for example, a 10 mM Ca + 50 mM Mg aqueous solution, which is then also validated for total chloride content with a Mohr titration and total metal content with the EDTA primary standard.

Is that a sufficient standard for a hobbyist application? I apologize for the lack of NIST traceability in advance.

 

[taricha]

So, Jim would you agree with the hobby conventional wisdom that Red Sea Mg reads a little high, but salifert Mg is right on?

(btw I'd say this photo you posted a while back is a pretty persuasive demonstration of your precision and repeatability in a lab-like setting)

 

[JimWelsh]

I cannot comment on the Red Sea Mg test, as I have never used it (yes, you read that correctly). The Salifert test is pretty good, and my favorite commercial manual titration, but IME the results can be affected by the calcium level somewhat. The lower your calcium, the lower your Mg reading will be, all other things being equal, and vice-versa. That said, the effect is relatively small. I'd have to go over old spreadsheets to remember the specifics.

 

[Dan_P]

It's an interesting issue. Every kit is known as being "high" or "low" or "spot on", but I've never seen anyone use a standard except what a salt mix ought to be when mixed to a measured target salinity,

Even more interesting, no one notices that except for Hanna, no hobby test kit including ICP provides accuracy or precision information.

 

[Randy Holmes-Farley Verified Community Expert]

Even more interesting, no one notices that except for Hanna, no hobby test kit including ICP provides accuracy or precision information.

That's what makes chemistry so much fun. It's like being in Vegas! lol

 

[Dan_P]

That's what makes chemistry so much fun. It's like being in Vegas! lol

Analytical chemistry roulette…just got an idea for a product.

 

[sublime275]

It's an interesting issue. Every kit is known as being "high" or "low" or "spot on", but I've never seen anyone use a standard except what a salt mix ought to be when mixed to a measured target salinity,

I’ve tested it using the Fauna Marin reference solution. It gave results 150-250ppm higher than what listed on the bottle. My Salifert and Aquaforest Mg test kits matched the reference solution within about 25ppm.