Pesticide detection in water is highly noted due to its effect on the whole ecosystem, which needs a preconcentration step, especially in trace levels. In this research, nut shells including almond, pistachio, walnut, hazelnut, and neem tree seed (with and without chemical modification) were pyrolyzed to prepare biochars as potential sorbents for pesticide detection in water. The extraction ability of prepared biochars was compared using a thin-film microextraction (TFME) setup with polyamide (PA) as the substrate. The role of biomass origin on the extraction efficiency was studied through the characterization process. During optimization, both weight percent of biochars in composite and effective parameters on the TFME setup were studied to achieve the outmost efficiency in extraction of eleven target pesticides. The proposed thin films had a precision range of 6-24% with an enrichment factor (EF) of 7-89. In method validation, a limit of detection (LOD) and a limit of quantitation (LOQ) range of (0.003-0.5) and (0.01-1.6) mu g L-1 was attained, respectively. Having a recovery level of 81-121%, the evaluated method was used for the extraction of 33 water samples. The results showed that four groundwater samples are contaminated and the concentration level of 4,4 ‘-DDE and p,p ‘-DDD exceeded the limited dose in water.
