## 7 Applications
For 90 s of preconcentration time, enhancement factors of 250, 130, 185, and 36 and detection limits (3 s) of 0.15, 0.41, 1.62, and 0.49 \(\upmu\)g L\({}^{-1}\) were obtained for Cu(II), Ni(II), Pb(II), and Cd(II), respectively. For 30 s of preconcentration time, an enhancement factor of 49 and a detection limit of 0.12 \(\upmu\)g L\({}^{-1}\) were achieved for Zn(II) determination. The method was tested by analyzing certified reference materials and biological samples. [PERSON] et al. in 2018 [37] described a fast, sensitive, and selective procedure for the analysis of aromatase inhibitors including anastrozole, letrozole, and exemestane used in the treatment of metastatic breast cancer by high performance liquid chromatography (HPLC) in human whole blood, plasma, and urine samples based on fabric phase sorptive extraction (FPSE). Validation was performed following the demands of international guidelines on bioanalytical methods validation. The analytical performance was proved on real human biological samples. The developed protocol can be readily applied for clinical and pharmaceutical analyses. Six different FPSE membrane chemistries were primarily evaluated: sol-gel CW 20M, sol-gel PEG-PPG-PEG, sol-gel PCAP-PDMS-PCAP, sol-gel octadecyl (C18), sol-gel polycaprolactone A, and sol-gel sucrose. Three of these membranes performed better for the extraction of the examined analytes: sol-gel CW 20M, sol-gel PEG-PPG-PEG, and sol-gel polycaprolactone using methanol for back extraction. [PERSON] et al. in 2019 [11] combined FPSE with gas chromatography mass spectrometry for the rapid extraction and determination of nineteen organochlorine pesticides in various fruit juices and water samples. The extraction approach was optimized in terms of sorbent chemistry, extraction time, stirring speed, type and volume of back-extraction solvent, and back-extraction time. Optimum conditions yielded limits of detection in a range of 0.007-0.032 ng/mL. The relative recoveries obtained by spiking organochlorine pesticides in water and selected juice samples were in the range of 91.56-99.83%. Sol-gel poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) was proved to be the best sorbent for the extraction and preconcentration of organochlorine pesticides in aqueous and fruit juice samples prior to analysis with gas chromatography mass spectrometry. [PERSON] et al. in 2019 [38] reported on the performance comparison between the exhaustive and equilibrium extraction using classical Avantor C18 solid phase extraction (SPE) sorbent, hydrophilic-lipophilic balance (HLB) SPE sorbent, Sep-Pak C18 SPE sorbent, novel sol-gel Carbowax 20M (sol-gel CW 20M) SPE sorbent, and sol-gel CW 20M coated fabric phase sorptive extraction (FPSE) media for the extraction of three inflammatory bowel disease (IBD) drugs. Both the commercial SPE phases and in-house synthesized sol-gel CW 20M SPE phases were loaded into SPE cartridges and the extractions were carried out under an exhaustive extraction mode, while FPSE was carried out under an equilibrium extraction mode. The method was validated in compliance with international guidelines for the bioanalytical method validation. Novel in-house synthesized and loaded sol-gel CW 20M SPE sorbent cartridges were characterized in terms of their extraction capability, breakthrough volume, retention volume, hold-up volume, number of the theoretical plate, and the retention factor. The performance of FPSE and SPE techniques was evaluated by comparing the breakthrough volume and enrichment factors. The authors found that for the examined analytes, SPE showed the highest enrichment factors; consequently, this method is more suitable for samples with low analytes concentration. [PERSON] in 2019 [39] investigated the use of FPSE for the extraction and preconcentration of ultra-trace level residues of fungicides (19 compounds) and insecticides (3 species) in wine samples. Subsequently, the preconcentrated analytes were determined using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).