# Supramolecular Materials as Solid-Phase Microextraction Coatings in Environmental Analysis
## 3 Metal-Organic Frameworks
### MOFs as SPME Coatings for Environmental Applications
#### 3.3.3 Extraction of Organophosphorus and Organochlorine Pesticides  
Organophosphorus (OPP) and organochlorine (OCP) pesticides are widely employed in agriculture for pest control. Being toxic and persistent compounds, they can exert a harmful impact on both ecosystems and human health, thus requiring strict monitoring to guarantee compliance with the current regulation [64]. To face this challenge, selective, sensitive, and reliable SPME methods based on MOF coatings have been proposed [65; 66; 67]. Electrospinning was applied by [PERSON] and coworkers to deposit a polyacrylamide/nickel-based MOF (PAN/Ni-MOF) nanocomposite coating on an SS wire for the extraction of diazinon and chloropyrifos from environmental water samples [65]. The obtained hydrophobic coating exploited the capability of the nitrile backbone of PAN to promote hydrogen bonding and \(\pi\)-\(\pi\) interactions with the OPPs. Corona discharge-ion mobility spectrometry (CD-IMS) was applied for the detection of diazinon and chloropyrifos, obtaining LOQs of 0.5 and 1 \(\mu\)g/L, respectively. Finally, the reliability of the developed method was assessed by analyzing river water (no pesticide detected), agricultural wastewater (\(\Sigma\)pesticides 24.6 \(\mu\)g/L), and groundwater samples near rice fields (\(\Sigma\)pesticides 20.0 \(\mu\)g/L). [PERSON] et al. developed a flexible/self-supported ZIF-67 film for thin-film microextraction of OPPs from agricultural wastewater and underground water [66]. Firstly, electrospinning followed by calcination was used to obtain cobalt oxide fibers; in a second step, functionalization with the MOF was carried out by hydrothermal reaction. The developed film was used for the extraction of ethion using secondary electrospray ionization-ion mobility spectrometry (SESI-IMS) as a detection technique, requiring only 2 min of detection time per sample. In addition, the thermal desorption of the film was in accordance with the principles of analytical green chemistry. Under optimized conditions, a LOQ of 500 ng/L was obtained, allowing for the detection of ethion in one agricultural wastewater sample (1.1 \(\mu\)g/L). A novel MOF coating was developed by [PERSON] et al. using a two-stage deposition process: a NU-1000 MOF was synthesized by solvothermal reaction and deposited onto SS wires using a silicone sealant [67]. The major features of the framework were the very high surface area (BET 1966 m\({}^{2}\)/g) and the presence of mesoporous channels able to increase mass transfer inside the coating. The material was tested for the extraction of six model OCPs at ultra-trace levels from water samples. Although the enrichment factors (EFs) were  
Figure 4: Schematic representation of the in situ heteroepitaxial growth of copper-2,5-diaminoterephthalate crystals on copper wires, followed by dip-coating: (**A**) immersion of copper wire in the conversion solution; (**B**) immersion of the treated copper wire in the saturated ligand solution; (**C**) coating annealing; (**D**) dip-coating using polymide solution. Reprinted with permission from [63]. higher than those obtained by using either commercial 65 \(\upmu\)m PDMS/DVB or 85 \(\upmu\)m PA fibers were achieved, selectivity issues were observed. In fact, when PAH extraction was carried out, a high adsorption capability was observed, with EFs in the 9800-11,000 range, due to the \(\pi\)-\(\pi\) and CH-\(\pi\) interactions between the polyaromatic compounds and the coating. Under optimized conditions, LOQs in the range of 37-190 ng/L were obtained; thus, the DI-SPME-GC-MS method was suitable for ultra-trace analysis of OCPs in river and pond water, detecting only hexachlorobenzene at a concentration of 1.86 \(\pm\) 0.08 ng/L and 2.08 \(\pm\) 0.13 ng/L, respectively. [PERSON] et al. developed a lotus-like Ni@NiO-embedded porous carbon (Ni@NiO/PC) SPME coating for the extraction of chlorobenzenes from aqueous samples [68].