Calcium Test Kit?

[Billybeau1]

Oh you are talking about the calcium kit. Sorry, I got mixed up.

These threads can get confusing sometimes.

The last time I tested Calcium hobby grade test kits, Salifert, LaMotte, Elos and API were all within the ballpark. Only Seachem read about 70 ppm lower than the others.

So is your problem seeing the end point or are your numbers way off ?

 

[Bryan]

It's the end point with the Lamotte CA, just don't get to a point what I can call blue that would be in the ballpark, so yes then the number is way off. It's near impossible to distinguish the endpoint. I need to titrate so the value is about 700-800 Ca before it will turn blue, which is obviously way off and no way near the 440 Ca with my API

p.,s. my API and Lamotte KH are almost dead on the same. Remember the end point for the Lamotte KH is not red but purple. Some kits were missing the color card.

 

[Billybeau1]

No, I meant I substituted the API sodium hydroxide reagent and used a few drops more instead of the Lamotte sodium hydroxide reagent. I think the Lamotte suffers from Mg interference.

I do not think that will work considering they are two different kits. Same principle though. The sodium hydroxide reagent cancels out the mag to give you what is left in general hardness which is calcium.

Since the LaMotte kit is used for both fresh and seawater, when used for seawater they want you to dilute the sample with ro/di (1 to 12.9) and then multiply the end result by 5.16 to get Ca++.

Might you post what the actual syringe on the LaMotte says when the color change occurs in your tank ?