# Application of Molecularly Imprinted Polymers in the Analysis of Waters and Wastewaters
## 5 Application of MIPs for the Detection of Different Classes of Contaminants
### Pesticides
#### 5.3.2. Herbicides  
2,4-dichlorophenol (2,4-DCP) is a common chlorophenol used in the production of herbicides [94]. 2,4-DCP-MIP is an electrochemical sensor used for the detection of 2,4-DCP, utilizing the functional monomer (MAA) and a mixture of chitosan (Ch) and nafion to immobilize the MIP and improve conductivity. The mass transfer to the electrode surface was likely blocked by this assembly, resulting in an LOD of 1.6 \(\times\) 10\({}^{3}\) nM. Carbon fiber paper can be used as the working electrode to detect 2,4-DCP using a poly(3,4-ethylenedioxythiophene) (PEDOT)-based MIP [95]. Using PEDOT as a conductive polymer, the result showed a limit of detection of 0.07 nM. In a different approach [92], GCE modified with o-PD was electropolymerized with multifunctional nanomaterials, zinc oxide nanoparticles (ZnO NPs), and graphene platelets to create the MIP. This MIP was evaluated in real wastewater samples, and exhibited higher sensitivity than other approaches used for the detection of 4-CP, with a limit of detection of 40 nM and a linear range of 2.0 \(\times\) 10\({}^{2}\)-1.7 \(\times\) 10\({}^{5}\) nM. Bensulfuron-methyl (BSM) was detected using imprinted magnetic microspheres sorbent [89], prepared by trimethylopropane trimethacrylate (TRIM) as a cross linker and MAA as a functional monomer to coat SiO\({}_{2}\) beads to get high stability. HPLC was used for detection with a linear range of 0.04\(-\)0.8 nM and a limit of detection of 6.4\(-\)9.5 nM, while the adsorption capacity was 37.32 mg g\({}^{-1}\). The polymer has high reproducibility when reused up to six times. A new method for the preparation of MIP-coated hollow fibers, using toluene, methacrylic acid (MAA), 2,2\({}^{\prime}\)-azobissobutyronitrile (AIBN), and ethylene glycol dimethacrylate (EGDMA) as solvent, functional monomer, initiator, and cross-linker, respectively, was applied for solid phase micro extraction of herbicides of propazine (PPZ) in aqueous media [100]. This method requires an incubation time of 1 h, and an adsorption capacity of 5.5 \(\upmu\)g per molecularly imprinted polymer-coated hollow fiber (MIP-HFs). The MIP-HFs can detect propazine (PPZ) with a linear range of 0.1-25 \(\upmu\)g L\({}^{-1}\) and a limit of detection of 0.03-0.1 \(\upmu\)g L\({}^{-1}\) when using HPLC-DAD detection. Yet, the recovery is not that high and further optimization is required to improve efficiency. Another method for PPZ determination was developed with supported liquid membrane molecularly imprinted beads based on biphasic solvent  
Figure 7: Schematic preparation method of DMMIP-Ag-N@ZnO/CHAC/GCE for the detection of cypermethrin [108]. (Reproduced under permission from Elsevier, doi:10.1016/j.bios.2018.12.002). toluene and acetonitrile, Di VinylBenzene (DVB) as crosslinker, AIBN as initiator, and MAA as functional monomer [101]. The optimized elution time was found to be half an hour with the elution solvent methanol, with high reproducibility on reuse up to reach to 30 times with HPLC-DAD with a limit of detection 0.022-0.030 \(\upmu\) L\({}^{-1}\). This method uses minimum solvent and can be called eco-friendly with good recognition abilities. Based on the above presented examples, unlike traditional methods, MIPs are promising sorbents for the detection of pesticide residues with various applications in the separation of analytes in a complex matrix coupled with chemical sensors and have been used directly and indirectly with chromatographic techniques. Different types of real samples, including fruits, vegetables, and biological materials, that are very difficult to analyze and have high matrix effects, especially on fats and proteins, which often interfere in the traditional detection approaches for pesticide. MIPs are proven to be excellent sorbents for the detection of pesticides in real samples. Bulk polymerization using methacrylic acid (MAA) was widely applied as a functional monomer.