# Application of Molecularly Imprinted Polymers in the Analysis of Waters and Wastewaters
## 5 Application of MIPs for the Detection of Different Classes of Contaminants
### Dyes  
Synthetic dyes are employed in many industries, such as textile, paper, plastics, leather, paints, etc. Their discharge to the environment has a negative impact, as some of these dyes are highly toxic, carcinogenic, and mutagenic in nature and are capable to bio-accumulate in the food chain, besides being stable and non-degradable. Even a very small amount of dye in water (about 10-20 mg L\({}^{-1}\)) is highly visible, which affects water's transparency and gas solubility and can prevent the penetration of light and oxygen, consequently reducing the photosynthetic activity in aquatic environments. The application of molecularly imprinted polymers seems to be a very promising approach for the analysis of water samples contaminated with different types of dyes. Congo Red (CR) is a disazo dye and metabolizes to the carcinogen benzidine. It also has a sulphonic acid group that enhances its hydrophilicity and has high stability and low biodegradability. Dispersion polymerization was first applied for polystyrene microspheres using CR as the template molecule followed by a single-step swelling polymerization to prepare CR-MIP microspheres in the aqueous phase using methacrylic acid as the functional monomer. The absorption capacity was found to be 27.0 mg g\({}^{-1}\), which is comparable to other reported adsorbents. The MIP-based method is superior in terms of the stability of the reusability of the prepared polymers. Additionally, the average removal rate of CR was found to be 95.63% and 91.73% from river and wastewater, respectively, indicating the high applicability of the prepared polymers [80]. Acid Green 16 (AG16) belongs to the triphenylmethane dyes and is widely used for nylon, wool, cotton, and silk pigmentation. It has three aryl radicals bound to a central carbon atom and was found to have genotoxic and mutagenic effects. Acid Green 16 bulk polymerized imprinted polymer was developed using 1-vinylimidazole as a functional monomer and ethylene glycol dimethacrylate as the cross-linker. The polymer showed excellent rebinding to the template of 83% as indicated by the HPLC measurements with  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Analyte** & **Monomer** & **Modifier** & **Working Electrode** & **Analytical Technique** & **Sample** & **Linear Range** & **LOD** & **Ref. ** \\ \hline Cd(II) & MAA & \begin{tabular}{c} Au nanoparticles \\ Cd(II)-IIPs \\ \end{tabular}  & CPE & CV, DPV, EIS & Tap and river & \(10^{-9}\)–\(10^{-4}\) & \(43\times 10^{-10}\) & [76] \\  & & & & water & mol L\({}^{-1}\) & mol L\({}^{-1}\) & [77] \\ \hline Cr(VI) & CTS & (IIP-S) & Au-plate & CV and EIS & Tap and river & \(1\times 10^{-9}\)–\(1\times 10^{5}\) & \(6.4\times 10^{-10}\) & [77] \\  & & & & water & mol L\({}^{-1}\) & & mol L\({}^{-1}\) & [77] \\ \hline Cr(VI) & 4-VP & (IIP@F-g-C\({}_{3}\)N\({}_{4}\)) & FTO electrode & EIS & Tap, east lake, and river water & 0.01–100 & 0.006 ppb & [53] \\ \hline Cr(III) & MAA & MWCNT-IIP & Pt Electrode & CV, DPV & Industrial wastewater & 1–5 ppm & 0.051 & [78] \\ \hline Cu(II) & \begin{tabular}{c} 5-methyl-2- \\ thiozymethethacrylate \\ \end{tabular}  & \begin{tabular}{c} Graphite \\ oxide-IIPs \\ \end{tabular}  & CPE & \begin{tabular}{c} Multichannel \\ proteinometric \\ measurement \\ system \\ \end{tabular}  & Tap, dam, and river water & \(1\times 10^{-6}\)–\(10\) & \(4\times 10^{-7}\) M & [51] \\ \hline Hg(II) & CMC & GCE/PPV/S-IIP & GCE & SWASV/ EIS & Tap, ground, and wastewater & 20–800 & 0.1 mg L\({}^{-1}\) & [47] \\ \hline Hg(II) & MAA & GCE-RGO-IIP & GCE & SWASV & Tap, aqueduct, river, and wastewater & 0.07–80 & 0.02 mg L\({}^{-1}\) & [46] \\ \hline Mn(II) & \begin{tabular}{c} (MAA), and \\ (NNMBA) \\ \end{tabular}  & MWCNT-IIPs & Pt Electrode & CV, DPV & Real water & 1–5 ppm & 0.0138 uM & [57] \\ \hline Mn(II) & MAA & \ \begin{tabular}{c} Mn(II)- \\ IIP/MWCNT/chit/IL \\ \end{tabular}  & GCE & SWASV & Wastewater & 2–9 uM & 0.015 uM & [79] \\ \hline Ni(II) & \begin{tabular}{c} CTS and \\ acrylic acid \\ \end{tabular}