Rationally Designed Molecularly Imprinted Polymers for Trace Electroanalysis of Environmental Micropollutants

Abstract

The undetected discharge of solubilized micropollutants into natural waterways constitutes a major public health concern. Thus, generalizable strategies to detect various micropollutant species coupled with deployable sensing platforms are paramount for indicating the presence of contamination at its earliest onset. Benchmark chromatographic methods paired with mass spectrometry to quantify micropollutants are expensive and difficult to deploy into waterways as passive environmental probes. In contrast, electrochemical sensors are inexpensive and easily miniaturized. We report the electrochemical detection of two compounds, 2,4,6-trinitrotoluene (TNT), a prevalent munition, and 2,4-dichlorophenoxyacetic acid (2,4-D), a common fertilizer, using molecularly imprinted polymers (MIPs). MIPs were rationally designed using DFT-level molecular simulations to determine an ideal functional monomer with maximal affinity for each micropollutant species. NMR titration methods were used to verify the simulation results and optimize the monomer/micropollutant ratio. Following optimization, MIPs were synthesized by anodic electropolymerization onto gold substrates in the presence of the micropollutant, which was subsequently stripped away via solvent washing to reveal micropollutant-specific binding sites. Upon micropollutant association with the MIP when placed in contaminated water, surface sites were blocked, which was tracked electrochemically. Each sensor exhibited a limit of detection in the sub-parts-per-billion regime, demonstrating the amenability of this sensing method for trace analysis. Combining the sensitivity of electroanalysis with the selectivity provided by the MIP recognition element constitutes a powerful platform for the detection of micropollutants in environmental matrices.FIGURE CAPTION:Electroanalytical signal obtained following the adsorption of TNT or 2,4-D molecules to an electropolymerized molecularly imprinted polymer (MIP) recognition element. MIPs may be rationally designed using density functional theory (DFT, inset) to maximize the monomer/toxin binding affinity, enhancing the analytical response and permitting the sub-ppb quantification of these toxins in environmental matrices. Figure 1