A comparison of water-sodium dodecyl sulfate phase transfer linear solvation energy relationships and databases

Four linear solvation energy relationship (LSER) studies of solute partitioning in aqueous sodium dodecyl sulfate micellar solutions are compared. Two of the LSERs are based on compilations of literature data obtained from a variety of measurement techniques and under differing experimental conditions. A third study used micellar electrokinetic capillary chromatography (MEKC) to obtain partition coefficients, whereas our approach is based solely on a head space gas chromatographic (HSGC) method. Despite significant differences in the sizes of the solute sets, the four LSERs yield essentially equivalent chemical conclusions regarding the fundamental interactions controlling the partition process. In comparison to MEKC, HSGC does not require the presence of salt or buffers, although it can be done with such additives, including cosurfactants. Additionally, the HSGC method, unlike the MLC method, does not involve assumptions concerning the behavior of any stationary phase. There are few restrictions on the HSGC method since one can use it to study species which are present in very low concentrations and which do not have chromophores. Finally, based on Kamlet's recommendation that three to four solutes are needed to properly define each LSER coefficient, we suggest a set of about 20 preferred solutes to use for future LSER studies of micellar systems.