Hanna extra deionized rodi for Ca test

[GulfReefer]

Hi

last night i checked my Ca with Hanna multiparameter tester i used Hanna extra deionized rodi so that i get accurate tesults. I got 360ppm after the test i decided to make second test using Salifert profi test amd i was surprised to get 440ppm !!? What the,,,, ell could we ever get a proper range with hanna ? I mean there is just no way to get a clear accurate result for Ca with hanna !? From now on i will not waste time with hanna Ca test . Anyone have same issue ? Anythoughts?!

 

[PigDaddyF15E]

I have both. I think most on here will say that the titration kits (when done according to direction) are "more" accurate. Or perhaps it's better to say most people are more likely to discard a Hanna CA number than a Salifert titration number.

Can't remember getting results that far apart...but there are a few reasons why it's possible

1. The error margin on the test kits themselves. IIRC the Hanna is about 5%. which means that 360 could be around 340 to as high as 380...ish

2. I've heard that the included device that you pull the saltwater sample (My apologies to the chemists) with can be inaccurate so it might be pulling more or less than the amount required for the test. If you have one...perhaps a syringe of some sort that you can accurately measure the saltwater sample size might help get a more accurate reading.

EDIT: 3. It's a stretch...but the 5% accuracy number is based off of 77F water...so I would think the margin would grow as you get further from 77F. It's probably not "significant" since most of us are within a couple of degrees of 77F...but "technically" it's a factor.