Use of Database of Plots of Pesticide Retention (R
F
) Against Mobile-Phase Compositions for Fractionation of a Mixture of Pesticides by Micropreparative Thin-Layer Chromatography |
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Authors: | T Tuzimski E Soczewiński |
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Institution: | (1) Department of Inorganic and Analytical Chemistry, Medical University, Staszica 6, 20–081 Lublin, Poland |
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Abstract: | Relationships between R
F
values and mobile-phase composition have been determined for urea herbicides and fungicides in normal-phase systems (NP) of the type silica-nonpolar or weakly polar diluent (heptane, toluene, diisopropyl ether) – polar modifier (ethyl acetate, tetrahydrofuran, dioxane, ethyl-methyl ketone and 2-propanol). These relationships constitute a retention database which has enabled to choose optimum systems for preliminary fractionation of a multicomponent mixture of pesticides by zonal micropreparative TLC. The mixture was applied from the edge of the layer in the frontal + elution mode which increased the separation efficiency because or displacement effects. The separated simpler fractions were applied to a silica plate and rechromatographed. The plate was videoscanned, furnishing a real picture of the plate showing preliminary separation of the simpler pesticide fractions. Complete separation of the fractions was carried out by two-dimensional thin-layer chromatography on plates with chemically bonded-cyanopropyl silica stationary phase using non-aqueous eluent in the first direction and aqueous reversed-phase eluent in the second direction. |
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Keywords: | Thin-layer chromatography Retention-mobile phase composition relationships Frontal + elution zonal chromatography 2D-TLC Pesticides |
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