ABSTRACT In this study, a cheap, novel, ecofriendly and effective nanosorbent was synthesised with natural materials such as sand beach and eggshell for diazinon determination in natural water. The synthesised nanosorbent was successfully characterised using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), field emission scanning- electron microscopy (SEM), vibrating sample magnetometer (VSM) and Brunauer–Emmett–Teller (BET) methods. Effective parameters were optimised for the extraction of diazinon and determination was done by UV-Vis spectroscopy at 248 nm. The method was linear in the range of 50–400 µg L−1 and the limit of detection was 6.9 µg L−1. Adsorption kinetic and isotherm studies were performed. Also, for measurement of diazinon in water samples of Gilan province, sampling was performed from important points such as river water, Anzali lagoon, well water, agricultural streams, and tap water. The results shows good spiked recovery (97.6–103.4%) in all samples. The accuracy of the method was also confirmed by the student’s t -test with HPLC analysis of real samples.