Relationship between Individual and Competitive Adsorption Isotherms on Molecularly Imprinted Polymers

Abstract

Molecularly imprinted polymers (MIP) are a new generation of selective adsorbents. In practical applications of MIPs Keywords molecularly imprinted polymer, adsorption isotherm, competitive adsorption isotherm, propranolol, beta blocker IntroductionMolecularly imprinted polymers (MIP) are a new generation of selective adsorbents. They are the subject of vigorous research which produces hundreds of papers annually. After years of fundamental research the time appears to be ripe now for their practical applications. This is attested by the increasing number of patent applications (62 in MIPs are typically made by polymerization of suitable monomers in the presence of a so-called template compound. After polymerization the template is removed from the polymer. This procedure leaves empty binding sites in the polymer, which are chemical and geometrical imprints of the template molecule. Due to these sites the MIP can rebind from solutions the template or other molecules which are chemically related to the template. The rebinding on a good MIP occurs selectively against compounds which are not very closely related to the template. The target compound of a practical application can be either the template or a closely related compound (e.g. if the template is expensive or toxic or its bleeding would disturb). Eventually a group of closely related compounds to the template may be targeted.For successful practical applications one needs to know if the MIP will show sufficient selectivity. Quantification of selectivity is a difficult problem in chemistry, and particularly in analytical chemistry [20][21][22][23][24][25]. In the case of MIPs one may rely on a large body of experience in relation to chromatographic adsorbents. The selectivity of liquid chromatographic stationary phases is easily characterized (in a given eluent) if the adsorption isotherms of all adsorbed solutes are linear. In this case selectivity between two adsorbable compounds can be given by the ratio of the respective isotherm slopes, i.e., by the ratio of the respective,

Relationship between Commonly Used Adsorption Isotherm Equations Impedes Isotherm Selection

“…These results mean, that the bi-Langmuir model can indeed quite closely approach the Freundlich isotherm. In the literature one can find many papers where isotherms have been measured with 5-10 % standard deviation [24,25]. With such precision it appears impossible to decide if isotherm data which can be fitted reasonably with the Freundlich equation are indeed Freundlich type or rather bi-Langmuir type.…”

In-Capillary Photodeposition of Glyphosate-Containing Polyacrylamide Nanometer-Thick Films

“…Hydrogels, as well as air-dried PAA and PAA-GLP, were examined using SEM–EDX (Figures E,F and S2 in the Supporting Information) and Raman spectroscopy (Figure A,B). The SEM microphotographs show clear polymer structures characterized by porosity incurred by the ACN porogen in UV-FRP. − Moreover, despite similar PAA and PAA-GLP nanofilm thickness, GLP slightly impacted polymer roughness and porosity. Presumably, these features may facilitate GLP encapsulation.…”

The Selectivity of Polymers Imprinted with Amines

“…It is possible to do equilibrium adsorption measurements also in mixtures. In some, but not all cases, the selectivity in mixtures may be estimated from separate measurements with the individual compounds [ 33 ].…”