Spectroscopic determination of pH

Abstract

A technique of measuring pH at temperature range of 20 - 70 ºC and high pressure conditions of 1 - 200 atmosp-heres has been developed by relating the ratio of absorbance peaks of indicator solutions (basic and acidic) as a function of pH, using ultraviolet-visible spectrophotometer. The pH values of the buffer solutions measured at 20 PoPC and 70 Po PC indicated slight temperature dependence, while the pressure had no effect. The pH of the buff-er solutions increased with temperature with relative standard deviations in the range 0.4 - 0.5 % at 95 % confid-ence interval. The possible causes of the temperature dependence were attributed to changes in pH values as the temperature changed.