A simple and rapid screening method for 2,4-dichlorophenoxyacetic acid (2,4-D) determination in environmental and vegetable samples by colorimetry combined with multivariate optimization

A rapid colorimetric screening method was established for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D). Multivariate optimization was employed to maximize absorbance values measured by spectrophotometry. Seven influential factors, pH, hydrochloric acid concentration, sulfanilic acid concentration, sodium nitrite concentration, reaction time, sulfanilic acid volume, and sodium nitrite volume were identified using a Plackett-Burman design for factor screening and optimized through a circumscribed central composite design. Under the optimized conditions, the method demonstrated linearity across the concentration range of 0.027–0.100 mg/L, with a limit of detection of 0.008 mg/L and a limit of quantification of 0.027 mg/L. Precision, expressed as relative standard deviation, ranged from 2.09 % to 4.07 %. Recovery studies confirmed satisfactory accuracy, yielding 93.2–126 % for tap and environmental water samples, and 97.5–102 % for vegetable samples including sweet corn, potatoes, and spring onions. These findings indicate that the developed method is accurate, precise, and reliable for rapid screening of 2,4-D in food and environmental matrices.