Inverse gas-chromatographic method for the estimation of the vapour pressure of less volatile compounds

Summary A simple gas-chromatographic technique is described to estimate the vapour pressure of compounds having low volatility. The method is fast, accurate and needs the sample in microquantities only. The methodology involves first to estimate the heat of vaporization by gas-liquid chromatography, which in turn is employed to determine the vapour pressure of the substance using the Clapeyron equation. The vapour pressure data of some aryl and alkyl phosphate esters have been obtained and are compared with the data resulting from the group contribution method.Abbreviations A integration constant - c constant - H heat of vaporization (kJ/mol) - m slope - P° vapour pressure (mmHg) - R gas constant - T temperature (°K) - V_v vapour value - x variable - Z_v vapour compressibility factor - Tr T/Tc - Tc critical temperature (°C)