Herbicides are commonly employed in agriculture to control unwanted plants and improve food production. The increase in population has led to an increase in food demand, thereby necessitating increased production of food crops. Therefore, farmers have used a large amount of pesticides, thus generating the problem of soil and water contamination.1
Because the process of partitioning of organic compounds across biological membranes is complicated, researchers have focused on the development of a simpler model to represent the transport of ions and molecules across hydrophobic barriers. The partition equilibrium across the water|oil and water|lipid membranes, gives an indication of the affinity of the chemical compound for the membrane structure of biological cells.
The herbicide simetryn (SIM) belongs to the triazine family, which are photosynthetic inhibitors. Their physiochemical characteristics include low solubility in water, low photodecomposition rates, and low volatility.2 The mobility of these herbicides in soil depends largely on their chemical properties, such as water solubility, and the ability to adsorb onto soil.
The interface of two immiscible electrolyte solutions (ITIES) has been studied to understand the transport of cations and organic molecules between two liquids of different polarity. The ITIES can mimic the water|lipid membrane of biological cells, because the interface can be electrically polarized through an external source. The interface between two immiscible liquids behaves as an electrode immersed in an electrolyte solution (M|S). Thus, the ITIES can be polarized in the same manner as the M|S interface.3 Therefore, the ITIES can be useful to understand the transfer of SIM in a water|organic solvent system.
The ITIES has been used for the analysis of biological samples usingmicro-ITIES,4 and for the detection of timolol5 and myoglobin.6 Kinetic studies on micropipettes having internal tip diameters ranging from 5 to 38 μm have also been carried out.7 Stripping analysis at micro-interface arrays has been employed for heavy metal detection in environmental samples.8
Dopamine detection at the ITIES using a highly hydrophobic ionophore (dibenzo-18-crown-6) to facilitate the transfer of protonated dopamine across the interface has been reported.9 The ITIES has also been used to investigate the transfer of highly hydrophilic ions.10 In our previous study, the transfer of heavy metal ions facilitated by diazadibenzo crown ethers and the carboxylic polyether “lasalocid A” has been carried out at the water|1,2-dichloroethane interface.11,12
The physicochemical parameters, such as partition equilibrium, are important to explain the hydrophobicity, which determines the chemical compound distribution between the aquatic and organic phases. In fact, acidic conditions are fundamental to the partition distribution of ionizable organic compounds.13
The mechanism of drug transfer across the ITIES has been studied.13 These studies have focused on the effect of pH and potential on the transfer of organic compounds across the ITIES. In fact, the ITIES has been used to explain the transfer process of molecules of environmental interest, such as triazine herbicides.14 Yudi’s group was the first to investigate the transfer of a series of triazine herbicides at the ITIES. This work was focused on analytical applications.15–17 Recent studies have employed partition ionic diagrams (PID) to understand the phenomenon of drug partition and to represent the solubility profiles as a function of pH and interfacial potential.18–22 PID representing the transfer of organic molecules can be developed from parameters obtained by cyclic voltammetry or square wave voltammetry experiments performed at different pH values to determine the transfer potential as a function of pH. The PID could be used as a tool to explain the behavior of some xenobiotics in the environment, especially of those in contact with biological membranes. The aim of this work is to study the electrochemical behavior of the SIM herbicide at the water|1,2-dichloethane interface.