N-Allylthiourea as a Rationally Selected Functional Monomer for Molecularly Imprinted Recognition and Trace Determination of Sulfanilamide

Abstract

Sulfanilamide, the archetypal sulfonamide antibiotic, remains a compound of considerable interest in analytical chemistry owing to its well-defined structure and pharmacological relevance. In this study, a molecularly imprinted polymer (MIP) incorporating N-allylthiourea as a functional monomer was rationally designed and synthesized for the selective recognition and extraction of sulfanilamide from complex pharmaceutical matrices. The polymer was prepared by bulk polymerization and characterized using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Adsorption behavior was evaluated by UV–Vis spectrophotometry, and the binding data were fitted to the Langmuir and Scatchard isotherm models. The resulting MIP exhibited outstanding binding performance, with a maximum adsorption capacity (Qmax) of 22,642.4 µmol g⁻¹ and a low dissociation constant (Kd = 0.04–0.07 µmol mL⁻¹), reflecting a strong and specific affinity toward sulfanilamide. The polymer further displayed high selectivity over the corresponding non-imprinted polymer (NIP), excellent sensitivity (limit of detection, LOD = 7.6 × 10⁻⁵ ppm), and high recovery (98.85%) in real pharmaceutical samples. These findings establish the developed MIP as a robust, selective, and cost-effective platform for the ultra-trace determination of sulfanilamide in complex sample matrices.