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  • 1 National Institute of Chemistry Hajdrihova 19 SI-1000 Ljubljana Slovenia
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A wide spread of measurements is typical in quantitative TLC. Improved reproducibility and speed can be achieved by automatic and controlled sample application, chromatographic development, and data acquisition and processing. Secondary chromatography is the main reason for poor precision in TLC. With RSD up to 10% this is by far the largest source of uncertainty. During the drying process mobile phase evaporates from the upper surface of the plate, and molecules of separated components inside the layer move up or down. Our experimental results show the strong dependence of the intensity of reflected diffuse light on the position of the spots inside the layer. Experimental results gave us an idea how to construct a device for drying and derivatization of TLC plates and a device which reduces uncontrolled propagation and non-homogeneous vertical in-depth distribution of spots during drying and derivatization was constructed. In addition the device designed is safer to use than a hair dryer. A laminar flow of air or inert gas constantly removes solvent vapor from the upper layer of the adsorbent and accelerates drying. Temperature is controlled and varies in a predetermined manner at predetermined intervals. Temperature gradient, which cannot be avoided in flow systems is controlled and is oriented in the direction of chromatographic development. The construction of the device results in identical drying conditions for substances with the same RF . Diffusion of the analyte is controlled and standardized and inhomogeneous in-depth distribution of compounds inside the adsorbent is minimized. Heating grade, heating intervals, pulses, switching, and other conditions are preset or programmable. The TLC dryer constructed reduces uncontrolled propagation and non-homogeneous vertical in-depth distribution of spots during drying and derivatization, which results in significantly improved reproducibility and precision. This is very important because in quantitative TLC most measurements are performed in reflectance mode.

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