Test Kit Problems (Salifert vs. Hanna Checker)

[Rickyrooz]

I purchased a new set of Salifert test kits from Drs. Foster and Smith last week to test against my Hanna Checker's because I felt there were off based on the color of my corals. This morning the Salifert alkalinity tested at 8.3 (expiration date 9/2018) and the Salifert calcium tested at 405 (expiration date 12/2018). The Hanna Checker for alkalinity tested at 7.62 (expiration date 8/2014) and the calcium registered at 489 (expiration date 11/2014). Which test kit should I believe is giving me the correct results?

 

[The Flying Turkey]

Take a water sample to your LFS and have them test it. Then compare those results to your own. See which two sets of test results agree.

 

[Rickyrooz]

Take a water sample to your LFS and have them test it. Then compare those results to your own. See which two sets of test results agree.

They only have API test kits, they are not as precise as the Hanna or Salifert. I believe the calcium is to the nearest 20 ppm and the alkalinity is to the nearest 1 dKH.

 

[cryptics]

I don't like the Hanna Calcium but love the alk. It is a little off though but it is consistent. So the key is to find out what it is off by. The sailfert is perfect for this since they give you a vial of test water with it. I use the test water in the Hanna and get the results. I then take the Hanna results and figure out what I need to multiply it by to get the dkh that the test vial is. My Hanna needs to be multiplied by .061 instead of the .056 they tell you to. Now it is in perfect sync with the sailfert.

Use sailfert for calcium

 

[saltyhog]

My Hanna alk checker is consistently 0.4-0.5 lower than Salifert. Using the control that comes with the Salifert the Hanna is actually closer to correct. With the Salifert I would have to end the titration at the first hint of color change not the end color on the instructions. That's what a control is good for, to tell you how to read the titration color change. Now I just use the Hanna cause it's a little faster and easier. Use Salifert for Ca, Mg, NO3. They are very repeatable.

 

[Rickyrooz]

The Salifert solution is 6.5 dKH and with the color change (from green to pink, orange, or red) it read 6.7 dKH. Much closer than the Hanna Checker to the reference solution.

 

[evolved]

I would tend to believe the Salifert tests first, for both Alk and Ca. The Hanna Calcium is notoriously sensitive to a precise measurement of added RODI.

The Salifert solution is 6.5 dKH and with the color change (from green to pink, orange, or red) it read 6.7 dKH. Much closer than the Hanna Checker to the reference solution.

So if you use the reference solution in the Hanna checker, what do you get?
If you preform the Salifert test using the reference solution, what do you get?

The first will tell you how accurate the Hanna is, the second will tell you how accurate you are with the Salifert kit. :)

 

[jservedio]

My Hanna Alk checker tends to read a little low - but it reads exactly the same way every single time. I simply "calibrate" it with every new bottle of reagent against the salifert reference solution to determine exactly how low it is reading. Once I know what the error "constant" is, it works extremely well. From test to test, it is never off by more than 1 or 2ppm.

Since I am not a chemist, I trust the Hanna to be far more consistent than myself doing titrations. And since I do my testing at night, I have no natural light to use which makes titration all that much harder.