## 7 Applications
Under the optimized conditions, which included polyester fabric that was used as the substrate for sol-gel PDMDPS coating, FPSE provided enrichment factors of 10 times with detection limits ranging from 6.01 to 60.7 ng L\({}^{-1}\). Ultra-high-performance liquid chromatography and tandem mass spectrometry detection were used for the determination of target analytes in sewage samples from wastewater treatment plants with different purification processes of Gran Canaria Island (Spain). No expensive commercial supplies or instrument were needed. Thus, FPSE was proved to be a cost-effective alternative to other expensive extraction and microextraction methods for the target analytes. [PERSON] et al. in 2015 [12] developed and validated a novel analytical method for the quantification of endocrine-disruptor alkyl phenols, namely: 4-tert-butylphenol, 4-sect-butylphenol, 4-tert-amylphenol, and 4-cumylphenol, in aqueous and soil samples. Analysis was subsequently performed by high-performance liquid chromatography with ultraviolet detection. Various parameters influencing the fabric phase sorptive extraction performance, such as extraction time, eluting solvent, elution time, and pH of the sample matrix, were optimized. Sol-gel PTHF coated FPSE media on cellulose substrate was proved to show the best extraction efficiency with methanol as the extraction solvent, yielding recovery rates of 74.0, 75.6, 78.0, and 78.3 for 4-tert-butylphenol, 4-tert-amylphenol, and 4-cumylphenol, respectively. Optimum conditions offer high preconcentration and enrichment factors and significantly reduced sample preparation time. The limits of detection ranged from 0.161 to 0.192 ng/mL, and the method was successfully applied for the recovery of alkyl phenols from spiked ground water, river water, and treated water obtained from a sewage treatment plant, and a soil and sludge sample. The method reduces the use of organic solvents substantially, meeting the criteria of the green analytical chemistry principle. [PERSON] et al. in 2015 [16] investigated the use of FPSE for the determination of four nonsteroidal anti-inflammatory drugs (ibuprofen, naproxen, ketoprofen and diclofenac) in environmental water samples prior to their determination by gas chromatography mass spectrometry. Various factors affecting FPSE, namely: sorbent chemistry, matrix pH, and ionic strength, were investigated using a mixed level factorial design (31 \(\times\) 22), while other important parameters, e.g., sample volume, extraction kinetics, desorption time, and volume, were also optimized. Three different FPSE sorbent chemistries, sol-gel PDMDPS, sol-gel PTHF, and sol-gel PEG, were investigated. Sol-gel PEG coatings on the cellulose substrate with ethyl acetate as the eluent proved to provide optimal operational conditions, leading to the limits of detection (S/N = 3) in the range of 0.8-5 ng L\({}^{-1}\). The enrichment factors ranged from 162 to 418, while absolute extraction efficiencies varied from 27% to 70%. Satisfactory relative recoveries within the range 82-116% demonstrated that the proposed method can be readily applied to routine environmental pollution monitoring. Actually, the proposed method was successfully applied to the analysis of examined analytes in two influent and effluent samples from a wastewater treatment plant and two river water samples in Spain. Compared to other sorptive microextraction techniques, FPSE showed many benefits such as simplicity in device fabrication, low cost, high enrichment factors and faster extraction equilibrium. [PERSON] et al. in 2015 [17] applied FPSE to develop a simple, sensitive, reliable, and fast analytical methods for the simultaneous determination of residual highly polar amphenicol antibiotics (amphenicols) in raw milk, followed by high-performance liquid chromatography-diode array analysis. A highly polar polymer coated FPSE membrane using short-chain poly (ethylene glycol) (sol-gel PEG) was used.