PH-DEFINING EQUILIBRIUM BETWEEN WATER AND SUPERCRITICAL CO2 - INFLUENCE ON SFE OF ORGANICS AND METAL-CHELATES

A direct measurement of the pH of water in contact with supercritical CO2 was made by observing the spectra of a pH indicator with a UV-vis spectrophotometer. The pH was analyzed under pressures of 70-200 atm a nd temperatures of 25-70 degrees C, The measured pH varied from 2.80 t o 2.95, and relative standard deviations of <1.5% were achieved, The e ffects of pH on the efficiency of supercritical fluid extraction of me tals and ionizable organic species in water-containing systems are dis cussed.