Pectin micro-encapsulation of pretilachlor for smart herbicide delivery through biopolymer guided slow release

Conventional pretilachlor formulation faces quick dissipation, leaching, and reduced efficacy. The present study aimed to synthesize encapsulated pretilachlor using pectin to achieve sustained release by optimising counter-ion solution and herbicide concentration. Pretilachlor was microencapsulated with 6 % pectin via ionotropic gelation using 2 % calcium chloride (CaCl2), barium chloride (BaCl2), zinc sulphate (ZnSO4) and zinc acetate as cross-linking baths. Herbicide concentrations of 0.5, 1.0 and 2.0 mL were evaluated. Morphological and encapsulation properties were characterized through phase contrast microscope, field emission scanning electron microscope (FESEM), Fourier transformed infra-red (FTIR) spectroscopy and EDS. Encapsulation efficiency and release profiles were determined via UV-Vis spectrophotometry and analysed using mathematical kinetic models. The extrusion of 6 % pectin solution into 2 % cross-linking baths produced beads of varying shapes, with BaCl2 yielding the most uniform and stable spherical microspheres. The mean diameter of the beads increased from 1.25 to 1.71 mm as pretilachlor concentration increased from 0.5 to 2.0 mL. Encapsulation efficiency and swelling percentage were highest at 0.5 mL concentration (69.4 % and 66.7 %), followed by 1.0 mL (64.04 % and 61.4 %) and 2.0 mL (59.36 % and 61.8 %), respectively. Structural analyses confirmed uniform encapsulation and stable microsphere formation and the encapsulated formulations exhibited a slow and sustained release pattern governed by first-order diffusion-controlled kinetics, in contrast to the rapid initial burst observed in the commercial formulation. Overall, encapsulating 0.5 mL of pretilachlor in 6 % pectin emerged as the most suitable treatment, offering improved encapsulation efficiency, higher swelling capacity and steady herbicide release for effective application.