Measuring and validation for isothermal solubility data of solid 2-(3,4-Dimethoxyphenyl)-5,6,7,8-tetramethoxychromen-4-one (nobiletin) in supercritical carbon dioxide

Abstract

Isothermal solubility of 2-(3,4-Dimethoxyphenyl)-5,6,7,8-tetramethoxychromen-4-one (nobiletin) in supercritical carbon dioxide at temperatures of (313, 323 and 333) K and pressures from (18 to 31) MPa was measured using an analytic-recirculation methodology, with direct determination of the molar composition of the carbon dioxide-rich phase by using high performance liquid chromatography. Results indicated that the range of the measured solubility of nobiletin was from 107 . 10(-6) mol . mol(-1) at T = 333 K and 18.35 MPa to 182 . 10(-6) mol . mol(-1) at T = 333 K and 31.40 MPa, with a temperature crossover around 18 MPa. The validation of the experimental solubility data was carried out by using three approaches, namely, estimation of combined expanded uncertainty for each solubility data point from experimental parameters values (<= 77 . 10(-6) mol . mol(-1)); thermodynamic consistency, verified utilizing a test adapted from tools based on Gibbs-Duhem equation and solubility modelling results; and, self-consistency, proved by correlating the solubility data with a semi-empirical model as a function of temperature, pressure and pure CO2 density.