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VAEIOUS DIFFERENTIAL MIGRATIOM METHODS 



Comparison o f Migration Methods 



A number of separatory methods may now be classified as differ- 

 ential migration methods of analysisI^,6sIV,105lV, lliIV, 12„ These 

 methods are applicable to -mrious kinds of substances which, with 

 respect to their physical state, are usually gases or solutes. Most 

 of the methods serve primarily for the resolution of mixtures, A 

 few, as time=of-f light mass spectrometry and gas chromatography, are 

 very effective for the detection of the constituents of mixtures. 

 Some, as electromagnetic mass spectrometry, serve for the separation 

 of mixtures and for the detection of the components « 



The principal differential migration methods of analysis are 

 compared in Table V,II„ The principal driving forces, the substances 

 that may be examined, and the most effective uses, such as separation 

 or detection, are included in this table. 



Some of the methods have been improved by the use of gradients 

 that increase the sharpness of the zones. Solution or elution gradi- 

 ents are widely employed in chromatography. Density gradients have 

 served as stabilizing systems in eleotrochromatography and in centri- 

 fugation. Likewise, pH gradients have proved extremely useful for 

 increasing the sharpness of the zones in eleotrochromatography^ s Sl j , 



TOOLS FOR PROGRESS 



Analysis and Progress 



The remarkable scientific progress that has been made since 

 Priestley's observations on gases, on respiration, and on photosynthesis 



