Determination of trace chromium (VI) in waste water by crystal violet-alizarin red spectrophotometry with potassium bromate catalytic oxidiation

Trace chromium(Ⅵ) could catalyze the oxidation reaction of crystal violet-alizarin red by potassium bromate in H2SO4 medium.A new determination method of trace chromium(Ⅵ) by double-wavelength double-indicator catalytic kinetic spectrophotometry was established through studying the absorbance change of catalytic reaction system and non-catalytic reaction system at 627 nm and 423 nm.Linear range of this method was 0.04-0.16 μg/mL for chromium,and detection limit was 11.41 ng/mL.The proposed method has been applied to the determination of chromium(Ⅵ) in electroplating effluent.The results were in coincidence with those obtained by atomic absorption spectrometry with recoveries of 98 %-102 %.