Testing CH levels in a pool with copper

[dbyang]

Just tried to test CH in my new pool filled with city water (Copper .668 ppm) with the tft100 test kit, and the pink solution precipitates into slightly purple particles, with the solution becoming almost clear, but will never turn blue. Is this amount of copper causing this test to fail?


Split from this thread Testing CH levels in a pool with copper

 

[chem geek]

Yes, it sounds like the metals are interfering. As noted here in the Taylor instructions:

Metal ions may cause interference; to prevent, add titrant containing EDTA to sample before buffer and indicator, then test as normal making sure to count drops of titrant added initially in total required to reach endpoint. If interference still occurs, dilute sample with DI water as necessary and retest.

So try adding 5 drops of R-0012 at the start of the test before the R-0010 calcium buffer and R-0011L indicator dye, but be sure and count these 5 drops in your total count.