Molecularly Imprinted Copolymers for Targeted Electrochemical Detection of Organic Contaminants in Groundwater

Water pollution from toxic organic contaminants such as methylene blue (MB) and methyl orange (MO) poses considerable environmental and health threats and represents a significant challenge requiring advanced sensing solutions. This study presents MB- and MO-imprinted polymers, referred to as MBIP and MOIP, which show significantly higher sensitivity and selectivity toward simultaneous electrochemical sensing of these dyes in complex dye mixtures and groundwater. A series of methacrylic acid (MAA)/acrylamide (AA) copolymers were synthesized with different ratios of MAA to AA, ranging from 70:30, 80:20, 90:10, to 100:0 (in mol %). MAA provides carboxylic acid groups, which can form noncovalent interactions with MB and MO, whereas AA provides amide groups, which enhance hydrophilicity and binding flexibility. The different ratios of MAA and AA optimize the chemical functionalities of the copolymers to improve their interactions with MB and MO. Screen-printed electrodes are used as substrates onto which copolymers are coated for the construction of disposable sensors. Electrochemical characterizations by electrochemical impedance spectroscopy and differential pulse voltammetry show that MBIP and MOIP containing 70% MAA and 30% AA (MBIP 70% and MOIP 70%) and 100% MAA (MBIP 100% and MOIP 100%) represent the best results. These sensors exhibit excellent sensitivity, with 9.26–9.30 μA/cm2·μM for MB and 4.51–5.00 μA/cm2·μM for MO and low limit of detection values of 171–386 nM for MB and 260–285 nM for MO. Furthermore, these sensors demonstrate excellent selectivity; i.e., they can distinguish target dyes even in the presence of interferents in complex dye mixtures. Finally, the sensors show excellent specificity for the target dyes even in matrixes as difficult as groundwater. This study describes the potential of MBIP and MOIP sensors for real-time monitoring of hazardous dyes that can contribute to efficient water quality management.