Vortex-assisted dispersive liquid–liquid microextraction using thymol based natural deep eutectic solvent for trace analysis of sulfonamides in water samples: Assessment of the greenness profile using AGREE metric, GAPI and analytical eco-scale

Applying the concepts of green analytical chemistry (GAC) across the whole method development is gaining more interest with the aim of using eco-friendly solvents and minimizing waste generation. Therefore, replacing the conventional methods with benign alternatives has been the aim of many researchers and practitioners worldwide. Natural deep eutectic solvents (NDESs) can be considered as a green alternative to the toxic organic solvents. In this work, a thymol based NDES was utilized for the first time in the extraction and trace analysis of four different sulfonamides (Sulfapyridine, sulfamethazine, sulfamethoxazole and Sulfaphenazole) in different water samples using dispersive liquid–liquid microextraction (DLLME). Two different groups of hydrophobic NDESs were prepared and tested as microextraction solvents, using the natural monoterpenoids (menthol and thymol) in combination with different acids and an alcohol. The results revealed that thymol/acetic acid DES had the best extraction recovery. Dispersion of the extracting solvents was achieved via vortex mixing. All DLLME parameters were optimized. The optimized method showed low detection limits (0.78 – 3.42 ng mL−1). A good linearity (5–5000 ng mL−1) with excellent determination coefficients (r2 ≥ 0.9991) was obtained. Accuracy and precision showed good results with % recovery in the range of 81.3–105.2 % and %RSD ranging from 1.3 to 7.9. The proposed method was successfully applied for the trace analysis of the target analytes in different water samples. Finally, the greenness profile was assessed by Analytical Eco-scale, Green Analytical Procedure Index (GAPI) and AGREE metric and comparison showed the superiority of the proposed method over other published methods. In conclusion, the reported method can be considered as a valid eco-friendly alternative for the classical and conventional hydrophobic DES-based DLLME methods for the routine analysis of sulfonamides in different water samples.