Comparison of Methods and Kits for Colorimetric Determination of Residual Chlorine in Water

Abstract The use of 3,3',5,5'-tetramethylbenzidine (TMB) for residual chlorine determination in water offers 2 possibilities, one at pH 1-2 and absorbance measurement at 450 nm and another at pH 3.8-5.8 and measurement at 650 nm. The reaction of chlorine with TMB reaches its maximum sensitivity at pH 1-2. The detection limit is 2 ng/mL. A calibrated scale for colorimetric determination of residual chlorine in water with 3,3',5,5'-tetramethylbenzidine (TMB), prepared with tropaeolin O (C.I. 14270), is described. This scale is stable for several months and can be useful in replacing the conventional and much less stable scale prepared from standard solutions of oxochlorate (I). Kits for deter…