Investigating a mixture of polar and nonpolar compounds using the

Investigating a Mixture of Polar and Nonpolar Compounds Using the Same Thin-Layer Chromatography Plate glass plate plastic or aluminium backed TLC piate.

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Here we wish to report a simple and efficient method or analyzing a mixtue containing polar and nonpolar compounds by using the same thin-layer chromatography plate. Very often natural-product chemists are faced with the problem of investigating a crude ether or chloroform extract of plant material which contains both polar and nonpolar components, this usually requires several thin layer plates. This problem can be circumvented by spotting and developing the compounds on a 4 x 10-em analyticalplilte (plastie- or aluminum-backed) clipped onto a glass plate of the same size (see figure). The plate is then developed in a normal TLC jar using a polar solvent until the solvent front, carrying the nonpolar components, reaches to 6 or 7 em. At this stage the plate is removed and investigated under the UV light and then cut below the solvent front as shown in the figure. The upper portion of the cut plate is then dried and redeveloped using a nonpolar solvent. By this technique one is able to separate the nonpolar fractions much better since they already have acquired different Rf values from the previous run.

Ratnasamy Somanathan Centro de Graduados e investigaci6n institute Tecno16gi~ode Tijuana Tiiuana. BCfa.. Mbxico

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Journal of Chemical Education