Spectrophotometric determination of ozone in ozonized air currents with chemical gas-liquid transfer using a microreactor

The spectrophotometric determination of ozone by measurement of its corresp onding iodine-starch complex at 580 nm was realized using a flow injection system with chemical gas-liquid transfer microreactor. The flow injection s ystem with a gas-liquid transfer microreactor (Vigreux type microcolumn, 50 0 mu l) 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 resid ence time. Ozonizated air currents were constantly passed through a samplin g loop at various flow rates, and then injected by countercurrent in the mi croreactor to ozonizate the reagent solution. The volume of the ozonizated air sampling loop was 32 mi, and 500 mu l for the reagent solution. The bes t results were: ozone chemical/physical transference of 95%, an output rate of 120 samples per hour, a detection limit of (3 s)=0.4mg O-3 l(-1), a wor k range from 0.4 to 10.6 mg O(3)l(-1), and a relative standard deviation of 1.7 (n=5, 1.2 mg O-3 l(-1)). Ozone production rate (mg O-3 h(-1)) was dete rmined from a homemade ozonizator (3 kV, air as feed gas), and ozone off-ga s from ozonization of agrochemical factory wastewater. Using this procedure , several problems of gas phase ozone determination were surpassed: low out put rate, excessive handling, and high consumption of the reagent solution. Additionally, direct ozone sampling by flow injection system was made poss ible. (C) 1999 Elsevier Science B.V. All rights reserved.