Applications and Comparison to Other Techniques

Inverse gas chromatography parameters can also be applied in the field of cafaly-sis. In fhis way, as example, parent NaX and CaA zeolites, as well as transition metal (Co +, Mn +, Fe )-exchanged zeolites, were evaluated for the catalytic oxidation of n-hexane. It was observed [51, 52], that although there was linear correlation between the acidity and the adsorption enthalpy of the n-hexane, there was no relationship between the acidity and the activity for n-hexane oxidation. However, if a reactivity parameter (such as Tso, temperature at which 50 % of conversion is attained) is plotted versus the adsorption heat, a so-called Volcano plot is obtained (Fig. 16.12), an optimum value of (-AH ) being observed, higher and lower values yielding to worst catalytic performance. 

IGC was also use to elucidate the nature of the interaction of both reactives and products with the surface of heterogeneous catalysts in order to obtain information for understanding the mechanism of the reaction. Xie et al. [31] proposed a mechanism for the partial oxidation of propylene to acrylic acid based on the adsorption parameters of reactive and products on styrene divinylbenzene copolymer (SDB) and Pd supported on SDB. Likewise, Dfaz et al. [53] studied the performance of Fe-ZSM-5 catalysts for benzylation of benzene with benzyl chloride in terms of their chemical and adsorption properties. 

Finally, a mention to the reverse-flow (RF) GC technique, which is a variation of IGC where the probe molecule is injected at a middle point of the column containing the adsorbent as stationary phase, and the direction of carrier gas flow is reversed from time to time. This creates extra chromatographic peaks on the continuous signal. This technique allows to measured different physicochemical quantities, including rate constant of surface and gaseous reactions, and experimental isotherms [54, 55]. 

Kiselev, Adsorbents in gas chromatography, in Advances in Chromatography, ed. by J.C. Giddings, R.A. KeUer (Marcel Dekker, New York, 1967) 

Voelkel, Inverse gas-chromatography—characterization of polymers, fibers, modified silicas, and surfactants. Grit. Rev. Anal. Chem. 22, 411-439 (1991). doi 10.1080/ 10408349108051641 

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The upgrade of a frequency-domain fluorescence lifetime imaging microscope (FLIM) to a prismless objective-based total internal reflection-FLIM (TIR-FLIM) system is described. By off-axis coupling of the intensity-modulated laser from a fiber and using a high numerical aperture oil objective, TIR-FLIM can be readily achieved. The usefulness of the technique is demonstrated by a fluorescence resonance energy transfer study of Annexin A4 relocation and two-dimensional crystal formation near the plasma membrane of cultured mammalian cells. Possible future applications and comparison to other techniques are discussed. 

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