Impregnation by Dipping

TLC plates Silica gel 60 (Merck) impregnated by dipping once in a 10% solution of polyethylene glycol 1000 in methanol. 

TLC plates cellulose (Merck) that have been impregnated by dipping in a solution of liquid paraffin — petroleum ether (5+95) (40-60 °C) for 4 s and then dried in the air for 5 min, before application of the samples. 

Paper Whatman No. 1 or 3 sheet (17x19 cm) impregnated by dipping in a 10% acetone solution of tributyrin, and drying in air. 

System Reversed phase, Whatman no. 1 or no. 3 paper chromatography, impregnated by dipping in 10% solution of tributyrin in acetone and drying in air. Sample A 5 yl of 1 to 5% solution in ethanol or chloroform. 

Use anal tech silica gel GF plates (20 X 20 cm) impregnated by dipping into ammoniacal silver nitrate solution for atrazine and 2,4-D. Prepare the dip solution by mixing 216 ml of fresh silver nitrate stock solution (17 g of AgNOi dissolved in 25 ml of deionized water, made up to 1 L with acetone), 20 ml of deionized water, and 6 ml of 6 M ammonium hydroxide. Dip for several seconds. 

Reversed phase (RP) TLC was originally carried out on silica gel or kieselguhr layers impregnated by dipping or development with a solution of paraffin, squalane, silicone oil, octanol, or oleyl alcohol. Analtech sells reversed phase plates with a hydrocarbon liquid phase physically adsorbed onto silica gel. Plates with the nonpolar liquid phase adsorbed to the layer surface require the use of aqueous and polar organic mobile phases saturated with the stationary liquid, and they cannot tolerate the use of nonpolar organic solvents. 

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