Twodimensional Separations on Paper

Where separations were not achieved in a single development, it was often possible to achieve the desired result using a second solvent system of different composition and development in a second dimension at 90° to the original direction of chromatography. Two-dimensional paper chromato-graphy was first described by Consden, Gordon and Martin for the separation of 20 amino acids, but was subsequently widely employed. An additional possibility was the use of paper chromatography in one direction with paper electrophoresis (both high and low voltage) in the second. Indeed, there are numerous examples in the literature of either chromatogra-phy followed by electrophoresis or electrophoresis followed by chromatography. A typical example of the type of result that could be obtained using two-dimensional paper chromatography is shown in Figure 3, whilst Figure 4 shows the combination of electrophoresis followed by chromatography in the second dimension for amino acids in fruit juice.

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Figure 3 A two-dimensional separation of a mixture of black and brown ink using butan-1-ol-ethanol-2mol L~1 aqueous ammonia (6:2:2) for the first development and butan-1-ol-acetic acid-water (6:1.5: 2.5) for the second dimension, on Whatman no. 1 paper. Key: 0, origin; 1, dark blue material remaining at or near the origin; 2, yellow pigment; 3, pink pigment; 4, diffuse brown pigment; 5, pink pigment; 6, yellow pigment; 7, scarlet pigment; 8, pink pigment; 9 and 10, faint spots of orange and yellow pigments respectively.

Figure 3 A two-dimensional separation of a mixture of black and brown ink using butan-1-ol-ethanol-2mol L~1 aqueous ammonia (6:2:2) for the first development and butan-1-ol-acetic acid-water (6:1.5: 2.5) for the second dimension, on Whatman no. 1 paper. Key: 0, origin; 1, dark blue material remaining at or near the origin; 2, yellow pigment; 3, pink pigment; 4, diffuse brown pigment; 5, pink pigment; 6, yellow pigment; 7, scarlet pigment; 8, pink pigment; 9 and 10, faint spots of orange and yellow pigments respectively.

sequently, apparatus became available that eliminated the need for cutting the paper to form a wick, and one such is shown in Figure 5B.

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