Estimating vapor pressure curves by thermogravimetry: a rapid and convenient method for characterization of pharmaceuticals

The purpose of this study was to investigate a rapid method for the evaluation of vaporization characteristics for selected benzoic acid derivatives. The compounds studied in this context were the ortho-, meta- and para-derivatives of hydroxy and amino benzoic acids. Calculations for the order of reaction were first carried out for each of the compounds using methyl paraben as the calibration standard. Those compounds undergoing zero order, non-activated evaporation processes, were analyzed by the Antoine and Langmuir equations, conjointly. The coefficient of vaporization was obtained as 1.2 X 10(5) +/- 0.8 Pa kg(0.5) mol(0.5) s(-1) m(-2) K-0.5. The vapor pressure values were used to determine the Antoine constants using the SPSS 10.0 software. This study attempts to outline a comprehensive thermogravimetric technique for vapor pressure characterization of single-component systems. (C) 2002 Elsevier Science B.V. All rights reserved.