This study explored the hydrolysis of cotton cellulose using a deep eutectic mixture made from choline chloride/oxalic acid. For the first time, the resulting nanocellulose with cellulose Iβ structure was utilized as an adsorbent for extracting pyrrole and pyridine via in-situ dispersive solid-phase extraction, followed by high-performance liquid chromatography-ultraviolet detection analysis. Acidic deep eutectic solvents offer a greener route for cellulose hydrolysis. This contrasts with conventional methods using sulfuric acid, which pose greater environmental concerns. The chemical functionality, microstructural characteristics, and crystalline structure of the nanocellulose were elucidated through the application of Fourier-transform infrared, field emission scanning electronic microscopy, and x-ray powder diffraction. The method had a suitable linear range (2–30 μg/L), high coefficients of determination (R2 = 0.9991 and 0.9992), and low detection limits (0.69 and 0.63 μg/L) for pyrrole and pyridine, respectively. The efficacy of the extraction method was assessed by determining analytes in wastewater and river water samples. Achieving a recovery exceeding 93.5% and relative standard deviations below 5.8% demonstrated the satisfactory precision and accuracy of the suggested method. The AGREE software assessment yielded a greenness score of 0.69 for the extraction procedure. This result indicates that the method exhibits a reasonable level of alignment with principles of environmental protection and human safety.
