J. Planar Chromatogr. 17, 186-191 (2004). TLC of sixteen new herbicides (7 2-(chlorophenoxy)acyl derivatives like e.g.methyl 2,4-dichlorophenoxyacetate, methyl 2-(2,4,5-trichlorophenoxy)propionate and 9 N-aryltrichloroacetamides like e.g. N-(4-chlorophenyl)trichloroacetamide, n-trichloroacetanilide, trichoroacetanilide) on RP-18 with aqueous buffer - methanol mixtures in saturated sandwich chambers. A Reprostar 3 video camera and Videostore software were used for visualization and evaluation of chromatograms.

J. Chromatogr. A 1558, 77-84 (2018). Investigation of the influence of concentration of ion-pairing additive, as well as concentration and type of organic modifier of the mobile phase on migration of peptides in a pressurized planar electrochromatography (PPEC) system with octadecyl silica-based adsorbent. Comparison of the results with those obtained by similar HPTLC and PPEC systems. Discussion of the influence of particular variables on retention, electrophoretic mobility of solutes and electroosmotic flow of the mobile phase, of the co-influence of these factors on the final selectivity of peptide separation, and of the difficulty of independent optimization of these factors due to their impact simultaneously on the retention, the electrophoretic mobility, and the electroosmotic flow. The pH of the mobile phase was the main variable for optimization of the PPEC system. Extensive tailing of peptide zones in the PPEC was observed in comparison to similar HPTLC systems.

Chinese Anal. Chem. (Fenxi Huaxue) 19, 1085-1088 (1991). Investigation of a method for rapid selection of the optimal solvent combination in TLC, by using a plot of Rf values against solvent polarity. Some examples.

Chromatographia 36, 330-336 (1993). Presentation of equations for the final Rf values for mobile phase gradient multiple development. Computer simulations of gradient development for both modes of TLC for the preliminary optimization of gradient programs.

J. Planar Chromatogr. 10, 411-415 (1997). Description of a simple method developed for optimization of multicomponent mobile phases. The method is based on seven isocratic experiments with binary, ternary, and quaternary mobile phases. hRf values were used as simple optimization criteria. Quaternary mobile phases usually contained weakly polar solvents as the so-called 'strength moderator'. The influences on the chromatographic separation of mobile phase strength and of the kind of moderator were demonstrated.

Chromatographia 61 (5-6), 307-309 (2005). Similarities and differences between the retention characteristics of octadecyl silica gel wettable with water used in TLC and RP-18 used in HPLC have been elucidated by use of the linear relationships between log k and RM. The stationary phases compared were investigated with the same mobile phases - binary mixtures of methanol and water, acetonitrile and water, and tetrahydrofuran and water. For these adsorbents of the same type but differing in specific surface area the correlation line was shifted by log (alpha system I / alpha system II). High values of the correlation coefficients obtained over the whole range of mobile phase organic modifier concentration examined indicated that the TLC systems could be used to predict HPLC conditions for flavonoid separation.

II. Ruggedness Testing. J. Planar Chromatogr. 6, 259-268 (1993). Discussion of different approaches to test the ruggedness of TLC methods, including Tests of the effects both of variations in the different environmental conditions (laboratories, analysts, and instruments) and of differences in experimental procedures (sample preparation, sample application, chromatographic separation, and spot visualization and detection).

JAOAC Int. 84, 1265-1276 (2001). Within the process of the International Conference on Harmonization (ICH), 2 guidelines were released containing a standardized terminology, a verified model of requirements for the validation of analytical procedures, and some guidance in the practical aspects of conducting validation studies in pharmaceutical analysis. For planar chromatographic procedures, which may be used at different levels either in qualitative identity testing, assays, semiquantitative limit tests, or quantitative determination of impurities, it was tried to transfer these formal requirements into practical approaches for validation. Topics like prevalidation considerations and validation (identification, testing for impurities with the limit test, testing for impurities by using quantitative procedures, robustness, quality assurance in routine work) were discussed.