Synthesis of resorcinol-functionalized multi-walled carbon nanotubes as a nanoadsorbent for the solid-phase extraction and determination of diclofenac in human plasma and aqueous samples

In this research, cyanuric chloride and resorcinol were incorporated for the aromatic hydroxyl functionalization of the surface of multi-walled carbon nanotubes (AHF-MWCNTs) in three steps through the chemical modification. The synthesized material was employed as an efficient adsorbent for the extraction of diclofenac diethylammonium (DDA) from aqueous and biological samples. The characterization of the synthesized nanoadsorbent was investigated by SEM, TGA, and FT-IR. The impact of various parameters, such as pH (2−11), initial concentration (5–100 mg L−1) of the solution, and contact time (5–30 min) on DDA adsorption was evaluated utilizing the batch method. After the extraction step, the HPLC-DAD (diode array detector) was applied to measure the concentration of DDA. The adsorption isotherm study of DDA illustrated that Langmuir isotherm fitted better the experimental data with a maximum monolayer adsorption capacity of 10.21 mg g−1. Besides, the adsorption kinetics were also studied, and the best fitting was attained by pseudo-second-order kinetic model (R2 = 0.9988). In the optimized extraction conditions, linear dynamic range and limit of detection were respectively 0.5–25 μg L−1 and 0.1 μg L−1. The recovery of 0.5 mg L−1 of DDA spiked in plasma sample was 92%. In addition, the release of DDA was obtained to be 88% in the simulated intestinal fluid (pH = 7.4) at 37 °C within 24 h. In conclusion, the proposed technique can be suggested for the successful extraction and determination of drugs from aqueous and biological samples.