J. Planar Chromatogr. 21, 315-323 (2008). The role of the mobile phase in controlling selectivity for adsorption chromatography - with either thin-layer plates or columns - is reviewed and expanded. The use of different solvent mixtures of varying selectivity in normal-phase chromatography is now on a firm theoretical and practical basis. The choice of a more polar component (B-solvent) of a binary solvent mixture (A/B) largely determines relative retention and resolution. Maximum differences in selectivity are achieved by the use of two mobile phases where the B-solvent is either very polar (requiring a lower % B for desirable values of k) or relatively nonpolar (requiring a higher % B).

J. Planar Chromatogr. 3, 425-528 (1990). It is proposed the RM values of substances analyzed on silica with tertiary mobile phases may be predicted from one-parameter regression equations. Experimental RM values for a group of isomers investigated have been compared with theoretical values calculated both on the basis of the author’s own studies (RMy = f(RMx)), and from Oscik’s theory. Substances chromatographed: o-, m- and p-isomers of aminophenol, ethylphenol, cresol, nitroaniline, nitrophenol, toluidine, chloroaniline, chlorophenol, nitrotoluene, chlorotoluene.

J. Planar Chromatogr. 6, 66-69 (1993). Use of a computer-assisted method to select the optimum mobile phase composition for the HPTLC separation of an unknown mixture of a pesticide intermediate. The method is based on spot order identification, by comparison of the UV spectra of spots, followed by single-factor optimization. Excellent agreement was obtained between predicted data and experimental results.

Chinese J. Chem. 14, 354-358 (1996). Presentation of a computer-assisted method for optimization of mobile phase composition and development distance in gradient two-step development HPTLC. The method is based on a system which can predict the final Rf values for gradient two-step development from values measured using five preliminary runs. The statistical scanning method is then used for optimization, using Rf difference as the selection criterion. The method was evaluated using a mixture of eight components and showed excellent agreement between predicted and experimental results.

J. Planar Chromatogr. 13, 337-347 (2000). HPTLC on cyano phases with five binary and ten ternary mobile phases containing methanol, acetonitrile, and water. A retention model was formulated at each composition using the solvation-parameter model. A mixture-design approach was then used to model the individual system constants as a continuous function of mobile phase composition, producing system surfaces from which retention surfaces could be calculated for method development. Regression analysis for the full data set indicated that the mixture-design models can be used to estimate solute migration properties with accuracy similar to that of the original solvation-parameter models.

J. Planar Chromatogr. 25, 504-508 (2012). Physical properties of polar and non-polar solvents under electric current pulse were studied. In addition, solvents were classified according to their behavior in a pulsating electric field with applications in planar dielectrochromatography.

J. Planar Chromatogr. 3, 515-520 (1990). One- and two-dimensional OPLC of 16 coumarins on silica with chloroform in the first and 30% ethyl acetate in the second direction. Visualization under UV 254 and 366 nm. Quantification by densitometry (absorbance at 310 nm). Preassays on TLC; discussion of the transfer of the separation from TLC to 2D TLC and further to 2D OPLC. The PRISMA system was used to optimize the chromatographic conditions.

Part II. Multi-stage development. J. Chromatogr. 635, 283-289 (1993). Presentation of a theoretical model of gradient multiple development as a basis for the optimization of separation by planar multi-step development and AMD and a computer program for the calculation of final Rf values for multi-stage development in the gradient mode for known retention vs. eluent composition relationship. Discussion of the influence of various parameter on the final Rf values. Comparison of the predicted and experimental Rf values.