Voltammetric determination of 2,4-dichlorophenoxyacetic acid using poly L-methionine-AuNPs /PGE

2,4-dichlorophenoxyacetic acid (2,4-D) and its derivatives are from phenoxy or phenoxyacetic acid herbicide family which belong to one of the largest herbicides group. 2,4-D is a white crystalline solid with chemical formula C8H6Cl2O3. These type of herbicides family are popular among the farmers because of their low cost, effectiveness even in low doses and good water solubility [1]. Ingestion, skin contact and inhalation are three main of human exposure to 2,4-D herbicides [2]. Due to their broad range of application and excessive usage, they have becoming a serious problem as they can cause pollution to the environment. 2,4-D causes an array of adverse effects to the nervous system: disruption of the activity of nervous system chemicals and behavioral changes. The researchers also postulated a possible association between exposure to 2,4-D and cancer in humans. For the given reasons, measuring this compound is very important in environmental samples. Some reported methods for measuring this herbicide include gas chromatography [3] and high performance liquid chromatography [4]. In this project, an electrochemical method is used to measure this herbicide.To prepare the modified electrode, the pencil graphite electrode (PGE) first are placed in a solution containing carbon nanotubes and chitosan for a specified period, and then it was dried in room temperaure. The pencil electrode is then subjected to a voltammetric cell containing a specified amount of methionine and Au(III) solution and then a composite from poly methionine and gold nanoparticle were placed on the electrode surface using cyclic voltammetry. After electrode preparation and its drying, the oxidation current of 2,4-D was measured at different concentrations in optimum pH 5.0. In order to achieve the best voltammetric response for the sample, electrode components and other effective parameters were optimized and then 2,4-D was determined using differential puls voltametric method. The linear dynamic range was obtained as 10-100 µm.