Correlation of retention parameters of pesticides in normal and RP systems and their utilization for the separation of a mixture of ten urea herbicides and fungicides by two-dimensional TLC on cyanopropyl-bonded polar stationary phase and two-adsorbent-layer multi-K plate

Ten urea herbicides and fungicides have been separated by use of two-dimensional thin-layer chromatography. The largest differences are obtained by combination of normal-phase (NP) system and reversed-phase (RP) system on cyanopropyl-bonded polar adsorbents and on two adsorbent layer containing a narrow zone of octadecyl silica and adjacent a wide zone of silica (or vice versa). The greatest spread of points was obtained for combination of nonaqueous NP phases with ethyl acetate on silica and RP phases comprising a polar solvent (methanol) in water on octadecyl silica adsorbent wettable with water (RP-18W). A good spread of points was also obtained for pairs of normal-phase systems with heptane-ethyl acetate mobile phases and reversed-phase systems with water-dioxane mobile phases, both on thin layers of cyanopropyl-bonded polar adsorbents. The correlations of R-F values in NP/RP systems were utilized in practical separation of a mixture of ten urea pesticides using 2D-TLC on these adsorbents. The plates were scanned and videoscanned showing the real pictures of TLC chromatograms.