Optimization of separation in TLC by use of desirability functions and mixture designs according to the 'PRISMA' method

A computer program has been developed for optimization of mobile phase comp osition in thin-layer chromatography (TLC). The desirability function techn ique combined with the 'PRISMA' model was used to enhance the quality of TL C separations, The statistical models for prediction of retardation and ban d-broadening at different mobile phase compositions obtained by the PRISMA method were examined for cyanobacterial hepatotoxins on normal-phase TLC pl ates and for phenolic compounds on reversed-phase (RP) layers. The study sh owed that the relationship between mobile phase composition and retardation of the test mixtures can be expressed with high accuracy by use of quadrat ic regression models. The retardation was described by k(c) = 1/(R-F-1) and the band-broadening in terms of the band width at the half-height of the p eak (w(h)). The models obtained were used to predict the resolution (R-s) f or different solvent combinations. The desirability function converted the calculated R-s value into the desirability value (D) and the overall optimu m was then defined by the overall desirability, The optimum mobile phase mi xtures for the separation were obtained as a contour plot inside the horizo ntal plane of the PRISMA model and good separation was achieved by use of t he optimized solvent combination. Depending on the objective for which the optimum separation is being investigated, the program enables either optimi zation of critical pairs or determination of the overall optimum in which t he intention is reasonable separation of as many compounds as possible.