Modern Methods Of Plant Analysis / Moderne Methoden Der Pflanzenanalyse (english, German And French Edition)

123 phase and hence have no direct bearing on the retention time of solutes. However in gas-solid chromatography, a considerable quantity of the mobile phase may be adsorbed on the surface of the stationary adsorbent which diminishes the column's effective length and ability to retain solutes. In this respect helium has been found to be preferable to most other gases (GREENE and Roy, 1957) because it is adsorbed to the least extent. 3. Packed columns offer a considerable resistance to flow, which may create a pressure differential between inlet and outlet of sufficient magnitude to cause an unfavorable flow rate through a significant length of the column. A reduced inlet/outlet pressure ratio can be obtained by using light molecular weight gases toward which the column packing shows the greatest permeability. The flow rate of the mobile phase is normally adjusted by altering the column inlet pressure, for which purpose commercial pressure regulators of sufficient accuracy are available. Quantitative measurements of the flow rate can be made by a number of methods, including rotameters, orifice meters, soapfilm flow meters and displacement of water. The former two methods are the most con­ venient but the least accurate; moreover they create a back pressure and are temperature dependent whereas although the moving soap bubble is cumbersome to employ and unusable for continuous readings, it is preferred when the highest accuracy is required. Front Matter....Pages II-XXVII Emission and Atomic Absorption Spectrochemical Methods....Pages 1-25 Mass Spectrometric Methods....Pages 26-50 Plant Spectra: Absorption and Action....Pages 51-72 Gefriertrocknung....Pages 73-96 Vapour Phase Chromatography....Pages 97-158 Ion-Exchange Chromatography....Pages 159-204 Molecular Sieving other than Dialysis....Pages 205-213 Dünnschicht-Chromatographie....Pages 214-229 Paper Chromatography on a Preparative Scale....Pages 230-249 Determination of Size, Shape and Homogeneity of Macromolecules in Solution....Pages 250-324 Optical Rotatory Dispersion. Its Application to Protein Conformation....Pages 325-335 Diffuse Röntgenkleinwinkelstreuung....Pages 336-358 Méthodes Calorimétriques pour l’;Analyse des Végétaux....Pages 359-367 Surface Factors Affecting the Penetration of Compounds into Plants....Pages 368-382 Tissue and Single Cell Cultures of Higher Plants as a Basic Experimental Method....Pages 383-421 Immunological Methods....Pages 422-463 Polarography and Tensammetry....Pages 464-493 Fallout Contamination in Plants....Pages 494-509 Back Matter....Pages 510-536