Selectivity and sensitivity enhanced green energy waste based indirect-μ-solid phase extraction of carbaryl supported by DFT and molecular docking studies

This work reports on a simple, selective, sensitive, rapid and robust spectrophotometric indirect-μ-solid phase extraction (ID-μ-SPE) of carbaryl with 4,4′-bis(4-aminophenoxy) benzophenone. These methods were performed in a 5 mL disposable syringe with green energy waste as a solid phase extractor in phosphate buffer medium (pH 8.5). The alkaline hydrolysis of carbaryl resulted 1-naphthol, which interacts with the diazotized 4,4′-bis(4-aminophenoxy) benzophenone to produce red colored product (λ_max:450 nm) or interacts with 4,4′-bis(4-aminophenoxy) benzophenone in the presence of an oxidizing agent, Se (IV) to give purple colored product (λ_max:545 nm). The obtained colored products were stable for 45 and 63 h respectively. The resulted colored products obey Beer's law in the range of 0.3–12.0 μg mL⁻¹ and 0.3–9.0 μg mL⁻¹ for both methods with detection limits ranging from 0.020–0.022 μg mL⁻¹. Additionally, the density functional theory calculations and molecular docking studies were performed to explore the stability profiles, intermolecular interactions and related electronic transitions for colored products to complement the experimental results. The developed methods are reliable and reproducible to detect carbaryl residues in its formulations, waters and food grains.