Rapid measurement of trace periodate concentration with bromide ion-catalyzed periodate for oxidation colorization of DPD

In the study, the Br--DPD method for the determination of IO4- concentration was established. The method facilitated the DPD indicator reaction by adding Br- and DPD at pH 5.5 (50 mM phosphate buffer) to complete the measurement of the IO4- concentration. DPD+ could be detected by UV-visible spectrophotometer at 510 nm and 551 nm. The experimental results showed a strong linear relationship between the absorbance of DPD+ and the concentrations of IO4-. The slopes of the calibration standard curves for absorption wavelengths at 510 nm and 551 nm are 1.92 x 10(4) M-1 cm(-1) (R-2 > 0.999) and 2.06 x 10(4) M-1 cm(-1) (R-2 > 0.999). The stoichiometric coefficient of the Br--DPD method for IO4- and DPD was 1:2, and pH in the range 3.0-7.0 had no significant different on the calibration curve of the Br--DPD method. The absorbance in experimental water remained stable within 600 s. The Br--DPD method accurately measured trace concentration of IO4- in ultrapure water at the range of 0.05 mu M-10 mu M. In addition, metal ions (Fe3+, Cu2+ and Co2+) and common anions (SO42-, NO3- and Cl-) showed little interference on the Br--DPD method. The results suggested that the Br--DPD method is a precise and versatile approach for measuring IO4- concentration.