Desorption mechanism summary

This publication arranges the published papers on adsorption of polymers with special regard to experiment and theory. A summary of all investigated systems is given. The experimental methods are outlined and the amounts adsorbed are discussed as a function of the system and experimental parameters (polymer, adsorbent, solvent, molecular, concentration, time, weight and temperature). Calculated and experimental amounts of saturation, the number of contact points per molecule adsorbed, the thickness of the adsorbed layer, the adsorption isotherms, the heats of adsorption, the effects of desorption are compared. Assumptions on the structur of the adsorbed layer and the mechanism of polymer adsorption are made and discussed. 

Data shown in Fig. 6 lead to the following conclusions at temperatures near 0 the desorption rate demonstrates Arrhenius behaviour with the effective activation energy of 50 4 kJ/mol, which is much greater than the value predicted by the simple MP mechanism (25-35 kJ/mol). Also, at temperatures above -40 C, the ice vaporization rate exceeds the desorption rate predicted by the simple MP model. In summary, the mobile precursor mechanism, as formulated by Somorjai and Davy, fails to describe the desorption kinetics of ice at temperatures near its melting point. 

In summary, measurements of surface tension presented in Fig. 2 demonstrate that three distinct mechanisms cause changes in surface tension upon oxidation of ferrocenyl surfactants (i) desorption of surfactant from the surface of an aqueous solution (ii) ionization of a surfactant without significant desorption from the surface of the solution and (iii) change in the phase state of a spontaneously adsorbed monolayer of surfactant, possibly driven by a change in the conformation of the surfactant within the monolayer. 

Various reviews and summary articles have addressed MALDI ionization. Some relevant concepts pre-date the advent of modem MALDI see, for example, Hillenkamp s discussion of LDI in 1983. Significant early MALDI reviews addressed a variety of possible mechanisms. Ehring, Karas, and HUlenkamp elaborated three excitation schemes leading to seven ion types. The key intermediate step for all involved highly excited matrix. Liao and Allison contributed an extensive discussion of protonated and sodiated adduct ions. This work emphasized the central role of ion-molecule reactions in the MALDI desorption plume. The consequent relevance of gas-phase thermodynamics to observed mass spectra has remained a central theme ever since. 

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