The Use of the Group Contribution Approach for the Assessment of the Possibility of Separation and Preconcentration of Organic Compounds in Liquid-Liquid Extraction Systems

Mikhail Zayats, The Laboratory of Dynamics of Pesticides, RUE “Institute of Plant Protection”, a/c Priluki, Minsk distr., Republic of Belarus
Aliaksandr Zaidzel, Analytical Chemistry Department, Belarusian State University, Faculty Of Chemistry, Minsk, Republic Of Belarus
Sergey Leschev, Analytical Chemistry Department, Belarusian State University, Faculty Of Chemistry, Minsk, Republic Of Belarus
Vitaliy Kondrev, Analytical Chemistry Department, Belarusian State University, Faculty Of Chemistry, Minsk, Republic Of Belarus

The group contribution approach is an extremely simple and convenient method of calculating partition coefficients of organic compounds, whose molecules do not contain appreciable intramolecular interactions. Most organic compounds do not fall into this category. Thus accounting for intramolecular interactions and introducing corrections in the procedure of calculating partition coefficients becomes very important. Solving such a problem will make it possible to extend the limits of this method’s applicability.

In this work we represent a method of systematization and quantitative estimation of the influence of intramolecular interactions on extraction. It is based on calculating the difference between the logarithm of experimental partition coefficient and the logarithm of partition coefficient estimated using the group contribution approach (ΔlgP). We also examined the influence of the nature, quantity and arrangement of functional groups in the molecules of organic compounds, as well as nature of extraction phases on the magnitude of ΔlgP. The database of ΔlgP values was used to make excellent predictions of the feasibility of separation and preconcentration of a wide range of organic analytes.