CONSIDERATIONS ABOUT THE ADSORPTION OF ORGANIC-MOLECULES FROM THE GAS-PHASE TO SURFACES - IMPLICATIONS FOR INVERSE GAS-CHROMATOGRAPHY AND THE PREDICTION OF ADSORPTION COEFFICIENTS
Ku. Goss, CONSIDERATIONS ABOUT THE ADSORPTION OF ORGANIC-MOLECULES FROM THE GAS-PHASE TO SURFACES - IMPLICATIONS FOR INVERSE GAS-CHROMATOGRAPHY AND THE PREDICTION OF ADSORPTION COEFFICIENTS, Journal of colloid and interface science, 190(1), 1997, pp. 241-249
Whether surfaces are characterized from experimental gasphase adsorpti
on coefficients of probe molecules with known properties (as is done i
n inverse gas chromatography (IGC)) or whether adsorption coefficients
are to be predicted from known properties of the adsorbate and the ad
sorbent (as is desirable in environmental chemistry) in both cases a c
orrect quantitative description of the van der Waals and acid-base int
eractions of organic molecules at surfaces is necessary, The model use
d to date in IGC for the van der Waals interactions tacitly assumes th
at the interactions of a dilute gas with a surface can be treated like
the interactions between two condensed phases, This only works if the
contact area of the adsorbed molecule is treated as an adjusted param
eter which makes up for the occurring discrepancies, In this paper an
improved equation for the van der Waals interactions will be suggested
which works without adjusted parameters, For describing acid-base int
eractions of dilute gases at surfaces Gutmann's donor and acceptor num
bers have found wide use in the IGC literature, However? these paramet
ers are related to the heats of the acid-base interactions rather than
the free energies, Thus this approach has the disadvantage of putting
the acid-base characterization of surfaces in IGC on a different basi
s than the van der Waals characterization, and it also does not allow
the prediction of gas-phase adsorption coefficients, Here, a different
approach will be discussed that was originally introduced by van Oss
and coworkers for the acid-base interactions between condensed phases
(1). This approach uses acceptor and donor parameters that are free en
ergy related, Validation with experimental data from the literature sh
ows a good performance of the equations introduced in this paper for I
GC purposes as well as for the prediction of gas-phase adsorption coef
ficients. (C) 1997 Academic Press.