Three-points approach to three-parameters diffusivity of mobile phase in polymer film

In this work, a three-points approach for estimating three-parameters diffusivity of mobile phase via desorption process from polymer film is proposed. In comparison with fitting curve by optimization technique, the new approach gives a substitutive method for estimation of parameters in three-parameters diffusivity. Troublesome tasks, such as guessing start point and dealing with irregular function encountered frequently in optimization approach can be avoided by using present approach. In this new approach, based on three key points on desorption curve, diffusivity parameters can be calculated from a database set-up in anticipation. A three-parameters diffusivity, belonging to a Fujita–Doolittle type diffusivity, is used for illustration. Numerical results reveal that accuracy of present approach is high, if diffusivity of mobile phase meets the diffusivity type prescribed completely. For demonstration in applicability, a computer-produced, random-error desorption curve as a simulated experimental desorption curve is also analyzed, and the results show that diffusivity recovered by present approach is satisfactory.