Elimination of the interference from non-specific adsorption on molecularly imprinted sensors in capacitive and piezoelectric microgravimetry dual-mode via a differential strategy demonstrated by 2,4-dichlorophenoxyacetic acid determination

Molecularly imprinting polymer (MIP) based capacitance and piezoelectric microgravimetry at a quartz crystal microbalance (QCM) sensors are enables to determine electrochemically active and inactive analytes. But the non-specific adsorption behavior of the MIP membrane is adverse to the selectivity of the MIP sensors. Herein, the interference from the non-specific adsorption on the MIP membranes in capacitance and QCM sensors was suppressed by a differential strategy, using 2,4-dichlorophenoxyacetic acid (2,4-D) as the model analyte. The MIP membrane for 2,4-D was constructed by the electropolymerization of o-phenylenediamine and resorcinol onto the surface of the gold electrode of a QCM resonator. The influence of the bypass effect from the pinhole defects in the MIP membrane on the response of the capacitance sensor was investigated by an impedance analysis method. The adsorption kinetics and isotherms were determined in the QCM mode. Under optimized conditions, the responses in capacitance and QCM modes are in linear correlation with 2,4-D concentrations in the range between 0.02–5 μM and 0.3–10 μM, with a detection limit of 4.6 and 91 nM, respectively. The interference level in the differential MIP mode is about 5 ∼ 10 % of the normal MIP mode, improving greatly the anti-interference ability of the MIP-based sensors.