Smartphone Colorimetric Determination of Carbofuran on a Molecularly Imprinted Polymer by an Azo Coupling Reaction

This work reports the development of an optical sensor using a novel adsorbent to determine carbofuran in fruit samples. Magnetic zeolitic imidazolate framework (magnetic ZIF-8) nanoparticles were synthesized and for improving selectivity and sensitivity, its surface was coated with molecularly imprinted polymers (MIP) through precipitation polymerization. This was done in the presence of carbofuran as a template on the magnetic ZIF-8 nanoparticles' surface. The new adsorbent was characterized by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The pH, adsorbent mass, and adsorption time on carbofuran adsorption on the surface of the adsorbent were optimized. To determine carbofuran, its color changes to orange by the azo-coupling reaction of adsorbed carbofuran on the polymer surface was investigated. The resulting color change was characterized using a colorimetric-based smartphone using the RGB profile. Under the optimum conditions, this discrete sensor showed low interferences and good sensitivity with a 40-s response time. Calibration with pixel (R + G + B) sloped fruit samples showed an exponentially increasing calibration curve in the linear range from 4 to 10 ppm. The developed sensor was used for determination of pesticides in fruit samples.