A novel thermogravimetric method for estimating the saturated vapor pressure of low-volatility compounds.
Thermogravimetric analysis is used to measure accelerated vaporization rates at elevated temperatures and reduced pressures for several compounds. Multiple linear regression is used to generate empirical coefficients of an equation that relates these parameters. The vaporization rates of the compounds at standard ambient temperature and pressure (SATP) are estimated by extrapolation to 10(5) Pa (1 atm) and 298 K. The estimated vaporization rates are then correlated with literature values of saturated vapor pressure (Psat). The results of twenty four compounds with vapor pressures that span 10 orders of magnitude indicate that p25 degrees C (sat) is directly proportional to the rate of vaporization at SATP. The average error of an estimate of p25 degrees C (sat) based on this relationship is less than a factor of 2.1.
Tesconi
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Department of Pharmaceutical Science, College of Pharmacy, University of Arizona, Tucson 85721, USA.
Yalkowsky
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D000399:Air Pressure; D016014:Linear Models; D008970:Molecular Weight; D013223:Statistics as Topic; D013696:Temperature; D013818:Thermogravimetry / Q000379:methods*; D014835:Volatilization