Physical Adsorption chromatography

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A variety of procedures were utilized to analyze this reaction mixture and to characterize a,10-diaminopolystyrene. Thin layer chromatographic analysis using toluene as eluent exhibited three spots with Rf values of 0.85, 0.09, and 0.05 which corresponded to polystyrene, poly(styryl)amine and a,w-diaminopolystyrene (see Figure 1). Pure samples of each of these products were obtained by silica gel column Chromatography of the crude reaction mixture initially using toluene as eluent [for polystyrene and poly(styryl)amine] followed by a methanol/toluene mixture (5/100 v/v) for the diamine. Size-exclusion chromatography could not be used to characterize the diamine since no peak was observed for this material, apparently because of the complication of physical adsorption to the column packing material. Therefore, the dibenzoyl derivative (eq. 5) was prepared and used for most of the analytical characterizations. 

At industrial scale, various chromatographic techniques are available adsorption chromatography, which uses physical binding effects which are dependent on pH or salt concentration affinity chromatography, where a specific binding between a molecule and the matrix is achieved and partition chromatography, where product and impurities move through the bed at different rates. 

It is the latter property (i.e., the ability for modification) that makes silica particularly useful as a separation medium in chromatography. Although physical adsorption has been used occasionally to modify silica surfaces for chromatographic purposes, its usefulness is limited because of the nature of modern HPLC. The use of high pressure creates shear forces at the station-... 

In gas-liquid chromatography, the stationary phase is a liquid that is immobilized on a solid. Retention of sample constituents involves equilibria between a gaseous and a liquid phase. In ga.s-solid chromatography, the stationary phase is a solid surface that retains analytes by physical adsorption. Here separation involves adsorption equilibria. 

Gas-solid chromatography has limited application because active or polar compounds are retained more or less permanently on the packings. In addition, severe tailing is often observed owing to the nonlinear character of the physical adsorption process. 

More recently, Hayashi et al. [50] found that toluene can be retained by adsorption on C oPd, a polymer-like material, at room temperature and at low toluene concentrations. Toluene seems to absorb through its ir-electrons on partially positive Pd atoms of C5oPd . Theoretical studies have suggested that TT-electrons of and toluene overlap through the d-electron orbitals of a Pd atom (thus, not only physical adsorption takes place). This may open a route to fuUerene-based materials as adsorbents for harmful volatile organic compounds (VOCs). Other recent studies on organic vapor adsorption on re connected with either applications in chromatography [51], or as a reference for comparison with carbon nanotubes [52]. 

Neutral organic compounds that cannot exist as cations may be retained by physical adsorption but can be washed off the cation exchange colunm by a brief rinse with an organic solvent. The amine cation can then be eluted from the column with a 1 M solution of trimethylamine in methanol. The trimethylamine converts the amine cation to the free amine which is no longer retained by the cation exchanger. Because of its volatility, trimethylamine is easily removed from the eluate. After acidification, the sample amines can be separated by cation chromatography. 

Inverse gas chromatography (IGC) is a rapid and reliable method used to evaluate the acid-base character of activated carbon surfaces. This method employs physical adsorption of appropriate molecnlar probes in a chromatographic (dynamic) experiment [288]. The amounts of solutes injected are very small, and it is assumed that the adsorption is described by Henry s law. From the retention volume the free energy of adsorption, AG°, is calcnlated as follows ... 

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