The Selectivity of Polymers Imprinted with Amines

Abstract

One of the main reasons for making molecularly imprinted polymers (MIPs) has been that MIPs interact selectively with a specific target compound. This claim is investigated here with the example of a widely used type of noncovalent MIP, the MIP for the beta blocker propranolol. Adsorption isotherms of this MIP and of a nonimprinted control polymer (NIP), respectively, have been measured with a series of compounds in the porogen solvent acetonitrile. The results, visualized as “selectivity ladders”, show that the MIP binds propranolol and many other amines better than the NIP does, but the selectivity of the MIP is actually inferior to that of the NIP. The selectivity of either polymer for propranolol is modest against many amines, but is remarkable with respect to other compounds. The contribution of imprinting towards selectivity can be better appreciated when three MIPs, made with different amine templates, are compared among themselves. Each MIP is seen to bind its own template slightly better than the other two MIPs do. In media different from the porogen, the selectivity patterns may change substantially. Propranolol seems to have properties that make it stand high on the selectivity scale in different solvents, albeit for different reasons.

Relationship between Commonly Used Adsorption Isotherm Equations Impedes Isotherm Selection

“…It is worth noting, however, that if the binding reaction is not of the type A + B = AB as assumed in the langmuirian models, but for example of the type A + B = C + D (like in ion exchange), then the adsorption isotherm equation is different from the Langmuir equation even if there exists only one type of site on/in the adsorbent. Under certain quite practical conditions one may obtain for such adsorption sites an isotherm equation which is of the Freundlich type [27].…”

New Methods to Study the Behavior of Molecularly Imprinted Polymers in Aprotic Solvents

“…Despite these achievements, understanding of imprinting has been found very recently to be far from satisfactory [37]. This view has been supported also by our recent paper [38] which has shown that the effect of imprinting on selectivity can be different from typical expectations.…”

A Molecularly Imprinted Polymer-based Dye Displacement Assay for the Rapid Visual Detection of Amphetamine in Urine

“…Mordant orange and phenol red provide no specific interaction to the MIP, though this can be attributed to their lack of amine functionality. This speculation is strengthened by the research conducted by Dorko et al, who characterized the interactions between different amine architectures and a MIP [ 42 ]. Many factors (including structure and size) affect the binding of a similar molecule to the MIP; however, most importantly, different factors affect the binding of a compound in different ways.…”