An on-line determination of chlorine dioxide using chlorophenol red by gas diffusion flow-injection analysis

An on-line determination of chlorine dioxide (ClO₂) in potable water using chlorophenol red (CPR) by gas diffusion flow-injection analysis (FIA) was investigated in the presence of various chlorinated species that can occur under normal water-treatment conditions. A gas diffusion membrane is used to separate the donor (sample) stream from the acceptor (detecting) stream (the donor stream transports the sample stream to the membrane separate device, and the acceptor stream collects all of the penetrated analytes and transports quantitatively to the detector) and makes it possible for this method to eliminate interference from metal ions, as well as other oxychlorinated compounds such as chlorite and chlorate. The system is more selective for chlorine dioxide than chlorine. The linear range of ClO₂ concentration is 0–0.5 mg·mL⁻¹ with a detection limit of 0.02 μg·mL⁻¹ (S/N = 3) and a sampling frequency of 50 h⁻¹. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 157–161, 1999