Resonance scattering effect of rhodamine dye association nanoparticles and its application to respective determination of trace ClO2 and Cl2.

A new resonance scattering method, based on resonance scattering (RS) effect, for the respective determination of ClO2 and Cl2 in water samples was developed. In HCl-NaAc buffer solutions with the pH value of 1.42, chlorine dioxide, or chlorine, oxidizes I- to form 12, which then reacts with the excess I- to form I3-. The resulting 13- would combine, respectively, with four rhodamine(Rh) dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG), and rhodamine S (RhS), to form association particles which exhibit a stronger resonance scattering (RS) effect at 420 nm. For four systems of RhB, bRhB, RhG, and RhS, chlorine dioxide was, respectively, determined in the concentration range of 0.0056 to approximately 0.787 mg/L, 0.0034 to approximately 0.396 mg/L, 0.0057 to approximately 0.795 mg/L, and 0.0052 to approximately 0.313 mg/L, with the detection limits of 0.0011 mg/L, 0.006 mg/L, 0.0054 mg/ L, and 0.0023 mg/L ClO2, respectively. At the same experimental conditions as those for the determination of ClO2, chlorine was, respectively, determined in the concentration range of 0.013 to approximately 0.784 mg/L, 0.0136 to approximately 0.522 mg/ L, 0.014 to approximately 0.81 mg/L, and 0.014 to approximately 0.42 mg/L, with the detection limits of 0.0016 mg/L, 0.0104 mg/L, 0.0079 mg/L, and 0.0037 mg/L Cl2, respectively. The total RS value originally from ClO2 and Cl2 was recorded in the buffer solution, while the RS value from ClO2 was obtained by using dimethyl sulfoxide to mask chlorine. Thus the RS value of chlorine was calculated by deducting the RS value of chlorine dioxide from the total RS value. The RhB RS method was chosen for the determination of ClO2 and Cl2 in drinking water, with advantages of high sensitivity, good selectivity, simplicity, rapidity, and convenience.