A novel and selective spectral method for the determination of trace chlorine in water basing on the resonance scattering effect of rhodamine B–I3 association nanoparticles

In Na2HPO4–citric acid buffer solution, Cl2 can oxidize I− to form I2 and then it reacts with excess I− to form I3−. The I3− combines respectively with rhodamine dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG) and rhodamine S (RhS), to form association particles which give stronger resonance scattering (RS) effect at 400 nm. The RS intensity of the RhB, b-RhB, RhG and RhS systems is proportional to chlorine concentrations in the range of 0.008–1.74, 0.019–1.33, 0.021–2.11 and 0.019–2.04 μg/mL Cl2, respectively. The detection limits of the systems were 0.0020, 0.0048, 0.0063 and 0.0017 μg/mL, respectively. In them, the RhB system has good stability and high sensitivity, and has been applied to the analysis of chlorine in drinking water, with satisfactory results which is in agreement with that of the methyl orange (MO) spectrophotometry.