Flow through potentiometric sensors based on molecularly imprinted polymers for selective monitoring of mepiquat residue, a quaternary ammonium herbicide

Abstract

A biomimetic potentiometric sensor for specific recognition of mepiquat (MQ), a herbicide and plant growth regulator, is designed. It belongs to the group of quaternary ammonium pesticides which are commonly known as quats. The sensor is produced via preparation of MQ imprinted polymer particles using methacrylic acid (MAA) and acrylamide (AA) as functional monomers. Subsequently, the leached molecularly imprinted polymer (MIP) particles were dispersed in 2-nitrophenyloctyl ether (o-NPOE) and embedded in polyvinyl chloride matrix, the design can be easily used in flow injection system. Under static modes of operation, the sensors revealed a near Nernstian response over a wide MQ⁺ concentration range 5.0 × 10⁻⁷ to 1.0 × 10⁻³ and 3.0 × 10⁻⁶ to 1.0 × 10⁻³ mol L⁻¹ with detection limit of 0.03 and 0.15 μg mL⁻¹, respectively. In the hydrodynamic mode of operation, good reproducibility (RSD of ±0.7%), fast response, high sensitivity with a Nernstian response 42.1 (r² = 0.999) and 38.4 (r² = 0.996) mV decade⁻¹, linear range 1.0 × 10⁻⁵ to 1.0 × 10⁻² and 5.0 × 10⁻⁵ to 1.0 × 10⁻² mol L⁻¹, detection limit 8 × 10⁻⁶ and 3 × 10⁻⁵ mol L⁻¹, high sampling rate (∼30 to 36 sample h⁻¹) and stable baseline was observed in the presence of 5 × 10⁻² mol L⁻¹ phosphate buffer (pH 6) as a carrier for MQ membrane based sensors. Applications of the sensors for the determination of MQ⁺ in spiked ground water and food samples are also reported.