AQUEOUS OZONE DETECTOR USING IN2O3 THIN-FILM SEMICONDUCTOR GAS SENSOR

A detector for continuous determination of a trace amount of aqueous o zone, utilizing an ozone-extraction process from liquid (water) into t he gas phase and an In2O3 thin-film semiconductor ozone gas sensor, ha s been developed. It has many advantages, including high sensitivity t o aqueous ozone and high aqueous ozone selectivity in the presence of various kinds of interfering compounds in water. It is able to detect 0.5 ppb of aqueous ozone with a sufficient response. The response to 1 ppm of free chlorine in water is smaller than that to 10 ppb of aqueo us ozone. It is revealed that the high sensitivity and the high select ivity are attributed in considerable part to the higher extraction rat e of ozone from water into the gas phase than those of other compounds in water. This detector is somewhat affected by a change in water tem perature. The water-temperature correction has been studied. A precise determination of aqueous ozone has been performed in the water-temper ature range 0-40 degrees C with an improved detector equipped with the correction process.