Determination and validation of Henry's constant for ozone in phosphate buffers using different analytical methodologies

Abstract

Different procedures for measuring the concentration of ozone in aqueous buffered solutions have been reviewed for the determination of Henry s constant at different temperatures and pH. Iodometry, indigo trisulfonate and iron (II) chemical methods were compared with the direct UV absorbance measurement of ozone at 258 nm. From these data a new value for the molar extinction coefficient of ozone is proposed as 3840 ± 109 M^(-)1 cm^(-1). After the verification of the ozone analysis methods, the solubility of ozone in phosphate buffer medium was studied with in-situ absorbance direct measurements in a device with high gas-liquid transference rate, minimizing the gas desorption process on sample manipulation. The decomposition of ozone was not detected at the experimental conditions tested and, consequently, the observed solubility of ozone is constant, with the pH ranging from 2 to 7.6. The solubility of ozone was measured between 5 and 35ºC, resulting in a dimensionless solubility ratio of HB0 = 1.797 exp[0.0277·t(ºC)].