ISOFIT - A program for fitting sorption isotherms to experimental data
Isotherm expressions are important for describing the partitioning of contaminants in environmental systems. ISOFIT (Isotherm Fitting Tool) is a software program that fits isotherm parameters to experimental data via the minimization of a weighted sum of squared error (WSSE) objective function. ISOFIT supports a number of isotherms, including several dual-mode isotherms that combine Freundlich, Langmuir, and Polanyi expressions with a linear partitioning term. To minimize the WSSE objective function, ISOFIT utilizes a hybrid optimization procedure that combines particle swarm optimization with Levenberg-Marquardt nonlinear regression. An initial swarm optimization step identifies promising solutions while circumventing local minima and the follow-on regression step provides local refinement and facilitates the calculation of numerous regression statistics. To demonstrate ISOFIT and evaluate its performance, the program was applied to a readily available sorption dataset and benchmarked against results generated using the MS Excel solver package. (c) 2007 Elsevier Ltd. All rights reserved.
sorption isotherm particle swarm optimization nonlinear regression parameter estimation