Multi-response optimization and validation analysis in the detection of acetochlor and butachlor by HPLC based on D-optimal design methodology

Acetochlor and butachlor, widely used herbicides, pose environmental and health risks through water contamination. This study developed a high-performance liquid chromatography (HPLC) method for analyzing these compounds, employing a multi-response approach and D-optimal design. The D-optimal design reduced the number of required experiments from 36 to 14. The response model was analyzed by variance and residual diagnosis, and a multi-response optimization process was implemented to minimize the retention time and maximize the peak area of the two analytes. The optimal conditions were determined: a column temperature of 30 °C, a mobile phase composition of 80:0:20 (CH₃OH:CH₃CN:H₂O) by volume, a flow rate of 0.9 mL min^-1, an injection volume of 25 μL, and a detection wavelength of 215 nm. The method achieved complete separation of acetochlor and butachlor within 10 min. The detection limits were 0.0018 mg L⁻¹ for acetochlor and 0.01 mg L⁻¹ for butachlor, with quantitation limits of 0.009 mg L⁻¹ and 0.06 mg L⁻¹, respectively. The linear ranges extended from 0.009 to 9 mg L⁻¹ for acetochlor and 0.06 to 15 mg L⁻¹ for butachlor, with a correlation coefficient (R²) of 0.9998, indicating excellent linearity. The recoveries ranged from 98.36 % to 103.13 % for acetochlor and 80.30 % to 107.74 % for butachlor, with the relative standard deviations both below 2 % (n = 6). This accurate, rapid, and sensitive method is well-suited for quantitative detection of these herbicides in water. It also serves as an invaluable reference for analyzing structurally similar chloroacetamide herbicides using HPLC.