Determination of Chlorine Dioxide Using Capillary On-Line Concentration Coupled with Flow Injection Analysis

Abstract.

A new method for the determination of chlorine dioxide (ClO₂) using capillary (Teflon filter tube) on-line concentration coupled with a flow injection system is proposed. The method is based on the color reaction of 4-aminoantipyrine (4-AAP) with phenol in the presence of ClO₂. The colored product is proportional to the concentration of ClO₂ and can be efficiently concentrated in the Teflon filter tube, following elution and spectrophotometric detection in a flow-through cell. The sensitivity of the method increases about 100 times after concentration. As a result, one of the most sensitive methods of determining ClO₂ (ppb) is obtained. The linear range after concentration is 5–250 µg · L⁻¹ ClO₂. The detection limit is 0.5 µg · L⁻¹. The interferences from other chlorinated compounds and metal ions were eliminated by utilizing gas-phase separation via porous polytetrafluoroethylene (PTFE) membrane for pretreatment.