## 3 Application of MOFs as Sorbents in Selected Techniques of Preparing Liquid Samples for Analysis
### Matrix Solid-Phase Dispersion (MSPD)
After extraction, analysis was performed by gas chromatography-tandem mass spectrometry (GC-MS/MS). Under optimal conditions, the linearity range of pyrethroids in wheat samples was 10-1000 ng/g; detection limits were in the range of 1.8 to 2.8 ng/g, and accuracy (RSD) was less than 6.3%. MOFs do not have to be used only as the main sorbent; their applications go far beyond that. The other authors used MOF as a support material for the molecularly imprinted polymer synthesis for the tetracyclines in milk powder analysis. Tetracycline was used as a template molecule, and 3-aminophenyl boronic acid as a functional monomer and cross-linking agent (Figure 19). The new materials were then characterized using FT-IR, XRD, N\({}_{2}\) adsorption/desorption measurements, and others. The extraction was followed by ultra-high-performance liquid chromatography with tandem mass spectrometry. Under the optimal conditions, the recoveries were in the range of 84.7-93.9%, with the detection limits of the tetracycline in the range of 0.217-0.318 ng/g [130]. The most common applications of the MSPD technique include the analysis of pesticides in plant samples. This is how the authors of one study [131] used the MOF, synthesized based on lanthanides, to analyze pesticides (atrazine, bifenthrin, bromuconazole, clofentezine, phenbuconazole, flumentrin, procymidone, and pyrimicarb) from bell pepper (Capsicum annum L.). After extraction, gas chromatography coupled to mass spectrometry was used in selected ion monitoring mode. The developed method was linear in the range of 50.0-1000.0 ug/kg for procymidone and 200.0-1000.0 ug/kg for the other pesticides. Correlation coefficients ranged from 0.9930 to 0.9992, and substance recoveries ranged from 52.7 to 135.0%, with CV values between 5.2 and 5.4%. Using MOF as a sorbent, it is possible to obtain excellent results from quantitative analysis [131]. An equally interesting paper comparing the sorption properties of several selected nanomaterials as sorbents was published by [PERSON] et al. [132]. The authors compared the use of graphene oxide, multi-walled carbon nanotubes, and 1,3,5-benzericarboxylate iron MOF as sorbents in  
Figure 19: The synthesis process of MOF-MIP presented by [PERSON] et al. MOF as a support material for the MIP synthesis [130]. the MSPD technique, with the latter showing the best performance in terms of extraction and purification efficiency of samples of fifteen phthalates from various environmental samples, prior to their separation and quantification by ultra-high performance liquid chromatography coupled to triple quadrupole mass spectrometry. The entire methodology was validated for agricultural soil and sand. The method's limits of quantification ranged from 0.14 to 2.7 ug/kg dry weight, with recoveries ranging from 70 to 120% and RSD below 20% [132]. The authors of another study [133] used a Box-Behnken design to optimize the experimental conditions for MSPD microextraction of five saponins in leaves (Figure 20). A simple MOF was used to obtain good linearity of >0.998 in the range of 0.01-100 ug/ml, with recoveries ranging from 87.04 to 103.78% and RSD lower than 5%. Compared with the traditional extraction method, the new MOF-assisted MSPD showed overall better performance, with low consumption of organic reagents [133]. A very interesting paper was presented by [PERSON] et al [134]. The research team tested the feasibility of using MOFs as a sorbent in the MSPD technique to analyze pesticide residues in chicken (Gallus gallus domesticus) egg samples. Two MOFs were tested as adsorbents in MSPD to extract lindane, bifenthrin, and pyrimicarb from lyophilized chicken eggs. A validated methodology was used to evaluate the performance of the new materials. The MOFs showed satisfactory results compared to conventional materials. More importantly, the MOFs allowed for the use of less sorptive material than conventional sorbents. After extraction, GC-MS was performed in the monitoring mode for selected ions.