ALERT: Salifert Calcium test instructions have changed

Myka · #1 02-04-2018, 03:59 AM

Just an FYI for those of us who have done the tests enough times to not read the instructions anymore...

The Salifert Calcium test kits with an expiry 8/2022 now require 10 drops of Ca-2 rather than 8.

However, since both the Ca-1 and the Ca-2 are provided in excess, you shouldn't see much or any difference in the results.

Myka · #2 02-04-2018, 04:35 AM

I found a thread on Reef2Reef discussing the new instructions, and Randy Homes-Farley explains why you won't see much difference:

Quote:

Originally Posted by Randy Holmes-Farley

CA-1 is a dye the binds calcium. It is a different color when bound to calcium and when not. The amount is not critical except to provide enough color. It is a weaker binder of calcium than the reagent in CA-3. Less of it may actually give a sharper endpoint, but may be harder to detect visually.

Ca-2 solution is a hydroxide solution to precipitate magnesium hydroxide and prevent it from being detected. The amount of it is not important as long as there is enough to precipitate the magnesium.

The titrant (CA-3) is a strong calcium binder (e.g., EDTA, but I'm not certain what exactly they use). As it is added, it binds up calcium. Eventually, the only calcium left that is not already bound to the CA-3 reagent is bound to the dye. At that point more added CA-3 strips away the calcium from the dye, and so the color changes as the dye transitions from calcium bound to free dye.

Since Ca-2 precipitates Mg, then maybe 8 drops isn't enough for people with higher Mg levels in their tank??? Maybe that's why the change?

FlamesFan · #3 02-04-2018, 02:39 PM

Thanks!

Frogger · #4 02-04-2018, 10:06 PM

Quote:

Originally Posted by Myka

Just an FYI for those of us who have done the tests enough times to not read the instructions anymore...

The Salifert Calcium test kits with an expiry 8/2022 now require 10 drops of Ca-2 rather than 8.

However, since both the Ca-1 and the Ca-2 are provided in excess, you shouldn't see much or any difference in the results.

Does this mean if we have old salifert test kits that we should be using 10 drops?

Myka · #5 02-05-2018, 12:59 AM

Quote:

Originally Posted by Frogger

Does this mean if we have old salifert test kits that we should be using 10 drops?

Not sure what the official recommendation is, but it sounds like that wouldn't hurt. Try both ways? I tried both ways (with the new kit that says 10 drops), and I got the exact same reading. Mg in my tank is about 1300 ppm.