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Modern Methods of Plant Analysis / Moderne Methoden der Pflanzenanalyse

Nombre de pages: 736

Progress of Great Britain by M.P.F.[!] Porter

About Great Britain, the British Empire and U.S.A. 4eme année d'anglais, lycées et collèges. Par Mme Camerlynck-Guernier et G.-H. Camerlynck,...

Auteure: Gabrielle Jeanne Camerlynck-Guernier , Gustave Henri Camerlynck

Nombre de pages: 292

Modern Methods of Plant Analysis / Moderne Methoden der Pflanzenanalyse

Auteure: K. Biemann , N. K. Boardman , B. Breyer , S. P. Burg , W. L. Butler , D. J. David , P. S. Davis , A. E. Dimond , A. C. Hildebrandt , F. A. Hommes , O. Kratky , H. F. Linskens , H. Moor , K. H. Norris , I. J. O'Donnell , J. V. Possingham , H. Prat , D. H. M. van Slogteren , E. Stahl , J. A. van der Veken , J. P. H. van der Want , E. F. Woods

Nombre de pages: 536

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...