Measuring bromine with TF-100 kit

[Maestro]

I have read the entire sticky thread on using bromine in my hot tub and I want to make sure I have everything right. In a few of chemgeek's posts he says that the TF-100 kit can be used to accurately test the bromine level using a conversion factor or 2.25 from FC to bromine.

So, as I understand it, I test 10ml of the spa water by adding a tiny scoop of DPD powder (R-0870) and add R-0871 drop by drop until the solution turns clear. I then multiply the number of drops by 1.125 (which is .5 times 2.25), and the result is the total bromine level. Is that correct?

Is there any need to add 5 drops of R-0003 reagent before dropping in the R-0871? (I thought that one of his posts suggested doing that, but I could be wrong.)

 

[JamesW]

Do the test the same as the fc and cc for chlorine and multiply by 1.125. Theoretically, there should not be any measurable combined bromine; however, there is almost always something that registers. Sometimes it's MPS, sometimes it's something else.

 

[chem geek]

Also, monobromamine itself (unlike monochloramine) shows up in the Free Chlorine (FC) part of the test so that's really testing Total Bromine. The R-0003 that normally measures Combined Chlorine (CC) would show up other types of combined bromines, mostly organic ones, and as James notes it's not that common.

 

[JamesW]

I'm not sure why, but, in a bromine tub, adding number r-003 usually turns the solution pink again. Something is reacting. I think that it can be mps, ozone, brominated compounds, or some other oxidizer. I do the test but I'm not sure what to do with the "cc" information since it shouldn't be combined bromine.

 

[chem geek]

The MPS should get measured in the FC part of the test because it reacts with FAS titration drops so if there's any color for FC where you add FAS drops you'll get MPS measured there (it's with the DPD-only test where MPS only shows up as part of CC because it doesn't directly react with DPD dye).