a207769s

Hello. I have been reading things on the internet and have decided to post here to ask for help. I have a 24' above ground pool and all summer the chlorine has read zero on test strips and it reads just about ideal on to OTO test. I read about high chlorine bleaching the strips but it does not read high on the OTO test. I am a chemist and I took a sample of pool water to work and used a test kit that out waste water treatment department uses to test for chlorine and it also read zero. not sure if it read TC or FC. It too was a strip type test. you measure a sample of water add powder and five drops of reagent shake it and drop in a strip and wait 30 seconds. The pH is generally good on the strip and drop test. To make sure I tested it on a pH probe at work that I calibrated with fresh standards and the pH read 7.45. The strip I tested today was as follows: TH: ~200ppm FC: 0 pH: ~7.2 TA: 240 ppm CYA: 0 (strip turned yellow, should be orange- unless this turns yellow when the strip burns) The pool has been schocked and we use an inline chlorinator with tri chlor tabs. The water has been clear all summer. THis is just driving me nuts. I read about the FAS-DPD tests are they worth it? I have looked everywhere and can't find it but I'll ask anyway. Is there a titration that can be done using laboratory chemicals to test for chlorine? I do titrations all day at work but I have never seen one to test chlorine. Anyone know the chemicals in the FAS-DPD kits? Any help would be great. THanks in advance. EDIT: found some titrations for FC and TC using volt potentials. not impossible just a pain.