Utilization of Alizarin Red Sulphonate (ARS) as Chromogenic Reagent for Determination of 2, 4-Dichlorophenoxyacetic acid pesticide (2,4-D) Residues

Spectrophotometric method has been developed and validated for the determination of 2,4-D residues in water and tomato. The proposed method is based on the derivatization of 2,4-D pesticide with Alizarin Red Sulphonate (ARS) as chromogenic reagent. In slightly acidic medium pH 6, a dark Purple – colored product exhibiting maximum absorption peak (λmax) at 563 nm was formed. The variables that affected the reaction such as pH, temperature, reaction time and the amount of ARS reagent and buffer were carefully studied and optimized. Under the optimum conditions, Beer's law is obeyed in the range 3- 40 μg/mL of 2,4-D at maximum wavelength of 563 nm. The linear regression equation of the calibration curve is A= 0.0795 + 0.0212 c (μg/mL), with a linear regression correlation coefficient of 0.9995. The molar absorptivity was 6.35X103 L/mol cm .The limits of detection (LOD) , limit of quantification (LOQ) and Sandell sensitivity were 0.8911 μg/ mL , 2.7003 μg/mL and 0.0348 ug/cm2 respectively. The recovery in the range of 97.33 - 102.89 % was obtained. The proposed method has been successfully applied to the determination of 2,4-D pesticide residues in tomato and water samples with good accuracy and precision.