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PEP Overview

A property Estimation Program (PEP), utilizing MCI-property, TSA-property and property correlations and UNIFAC-derived activity coefficients, has been developed for the Apple Macintosh microcomputer to provide the user with several approaches to estimate S, Kow, Pv, H, Koc, and BCF depending on the information available.

Structural information required for the MCi and UNIFAC calculation routines can be entered using either Simplified Molecular Identification and Line Entry System (SMILES) notation or connection tables generated with commercially available two-dimensional drawing programs. The TSA module accepts 3-D atomic coordinates entered manually or directly reads coordinate files generated by molecular modeling software. The program’s built-in intelligence helps the user choose the most appropriate QSPR or QPPR based on the structure of the chemical of interest. In addiction, the statistical information associated with each QSPR or QPPR in PEP can be displayed to help the user determine the model’s validity. For the regression-based property estimation models, assessments of accuracy based on the 95% confidence interval and estimated precision of the experimental values are also provided along with the estimated property value.

PEP also provides a batch mode that provides users with a method for the convenient, unattended calculation of MCIs, TSA and UNIFAC activity coefficients and the subsequent estimation of physical properties for large numbers of compounds.

A chemical property database, containing experimental values of S, Kow, H, Pv, Koc, and BCF complied from a variety of literature sources and computerized databases was used for developing the MCI-property, TSA-Property and property-property relationships used in PEP. This database, which currently contains over 800 chemicals, is linked directly to PEP.

The property estimation modules in PEP are also linked directly to the Level 1 and 2 Fugacity Models. The combination of the various property estimation methods, chemical property database, and simple environmental fate models provides users with a methodology for predicting the environmental distribution of an organic chemical in a multi-phase system requiring only the structure of the chemical of interest as input.

PEP was designed to be intuitive and user friendly. The easiest way to become familiar with the PEP is to try clicking on the buttons and pull down menus found on each card. Any comments or suggestions regarding improving the operation of PEP would be greatly appreciated by the authors.