Single-step Stability Studies

Abstract

By the use of a reciprocal heating machine, kinetic studies under nonisothermal conditions have been made. These single-step concentration-time-temperature studies permit a complete investigation of those parameters important for stability prediction to be made on one sample, in one run, regardless of whether previous screening studies have been made. The hydrolysis of two esters (ethyl acetate and p-nitrophenol acetate) has been followed to demonstrate the suitability of the theory and the method for determining both the energy of activation and the rate constant at any temperature. The potential of a single-step study method such as the one proposed, for investigations where large numbers of temperature sensitivity studies must be made, as for formula stability predictions, will be apparent, but other advantages over classical kinetic methods, such as number of samples and the volume of controlled temperature space required, increase its potential still further. By the use of a reciprocal heating machine, kinetic studies under nonisothermal conditions have been made. These single-step concentration-time-temperature studies permit a complete investigation of those parameters important for stability prediction to be made on one sample, in one run, regardless of whether previous screening studies have been made. The hydrolysis of two esters (ethyl acetate and p-nitrophenol acetate) has been followed to demonstrate the suitability of the theory and the method for determining both the energy of activation and the rate constant at any temperature. The potential of a single-step study method such as the one proposed, for investigations where large numbers of temperature sensitivity studies must be made, as for formula stability predictions, will be apparent, but other advantages over classical kinetic methods, such as number of samples and the volume of controlled temperature space required, increase its potential still further.