366 



RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



the Strip does not touch the walls except at the upper end. The tube is 

 then stoppered with a cork for development of the ehromatogram. 



Various procedures have been described for carrying out paper chroma- 

 tography so as to permit isolation of larger quantities than by ordinary 

 methods (17 to 20). Other modifications include the use of impregnated 

 filter paper, which gives a " reversed-phase " ehromatogram in which the 

 less polar solvent is the stationary phase (8, 21). A gradient-elution 

 analysis has also been reported in which a continuously changing solvent 

 is employed (22). 



Filter Paper. There are numerous commercial filter papers that are 

 satisfactory for chromatographic separations. The best paper for any 

 given experimental requirements and conditions would have to be deter- 

 mined by trial. The results of Rockland et al. (23), who rated 13 differ- 

 ent papers as to suitabihty for the separation of amino acid mixtures, may 

 be used as a guide in the initial selection. Table 8-1 presents a hsting of 

 the papers tested in approximate decreasing order of suitability. In 

 addition, Kowkabany and Cassidy (24) have reported satisfactory results 

 with the following: Whatman 3, Schleicher and Schuell 595, Whatman 4 

 Schleicher and Schuell 589 black, Whatman 2, and Schleicher and Schuell 

 589 white. 



Table 8-1. Filter-paper Characteristics (in Approximate Decreasing 



Order of Suitability) 



Type 



Texture 



Schleicher 

 Schleicher 

 Schleicher 

 Schleicher 

 Whatman 

 Schleicher 

 Schleicher 

 Munktells 

 Schleicher 

 Eaton and 

 Munktells 

 Eaton and 

 Eaton and 



and Schuell 589 



and Schuell 507 



and Schuell 589 red 



and Schuell 602 E and D. 

 1 



and Schuell 602. 

 and Schuell 576. 

 



and Schuell 598 YD. 



Dikeman 7 



IF 



Dikeman 248 



Dikeman 613 



Medium rough 

 Smooth 

 Medium rough 

 Medium rough 

 Medium rough 

 Medium rough 

 Smooth 

 Rough 



Medium rough 

 Medium rough 

 Very rough 

 Very rough 

 Very rough 



Uniformity'^ 



A 

 A 

 A 

 A 

 B 

 A 

 A 

 B 

 A 

 C 

 B 

 B 

 A 



Solvent 

 speed* 



260 

 240 

 180 

 270 

 190 

 280 

 280 



60 

 100 

 120 



80 

 240 

 180 



" Based on percentage of transmittance as determined photoelectrically. Mean 

 deviation from mean values: A, less than 1 per cent; 5, 1 to 2 per cent; C, more than 

 2 per cent. 



* Minutes required at 26°C for water-saturated phenol to ascend 120 mm on trape- 

 zoidal filter-paper strips. 



[From Louis B. Rockland, Jeremiah L. Blatt, and Max S. Dunn, Small Scale Filter 

 Paper Chromatography, Anal. Chem., 23: 1142-1146 (1951).] 



