Spectrophotometric determination of ozone in ozonized air currents with chemical gas–liquid transfer using a microreactor Original Research Article

The spectrophotometric determination of ozone by measurement of its corresponding iodine–starch complex at 580 nm was realized using a flow injection system with chemical gas–liquid transfer microreactor. The flow injection system with a gas–liquid transfer microreactor (Vigreux type microcolumn, 500 μl) was designed to use a reagent solution (1% (m/v) potassium iodide, 0.1 mol l−1 boric acid, and 1% (m/v) starch) for ozonization at low residence time. Ozonizated air currents were constantly passed through a sampling loop at various flow rates, and then injected by countercurrent in the microreactor to ozonizate the reagent solution. The volume of the ozonizated air sampling loop was 32 ml, and 500 μl for the reagent solution. The best results were: ozone chemical/physical transference of 95%, an output rate of 120 samples per hour, a detection limit of (3 s)=0.4 mg O3 l−1, a work range from 0.4 to 10.6 mg O3 l−1, and a relative standard deviation of 1.7 (n=5, 1.2 mg O3 l−1). Ozone production rate (mg O3 h−1) was determined from a homemade ozonizator (3 kV, air as feed gas), and ozone off-gas from ozonization of agrochemical factory wastewater. Using this procedure, several problems of gas phase ozone determination were surpassed: low output rate, excessive handling, and high consumption of the reagent solution. Additionally, direct ozone sampling by flow injection system was made possible.