# New Challenges in (Bio)Analytical Sample Treatment Procedures for Clinical Applications
## 3 Sample Preparation Techniques for Diagnostic Purposes
### Fabric Phase Sorptive Extraction (FPSE)
Membranes were cut to have an identical surface area with an internal diameter of 11 cm. They were washed first with acetonitrile as follows: methanol (50:50, \(v/v\)) and then with milliQ water. Subsequently, the conditioned membranes were inserted into the sample (diluted whole blood, plasma, and urine) and were left for 30 min on the rotator. After this time, the analytes extracted were eluted from FSPE membranes using methanol, and the eluant sample was centrifugated. An aliquot from obtained supernatant was directly injected into the HPLC-DAD for the analysis [22]. [PERSON] et al. used eight different FPSE membranes for preliminary experiments to extract antidepressant drugs from conventional biological matrices (plasma and urine) and unconventional biological matrices (human saliva). For the optimization of the extraction process, all the parameters were gradually optimized to obtain the maximum extraction efficiency of the compounds. After the activation of the membranes, the following initial general conditions have been tested: each support was immersed in 500 \(\upmu\)L of standard solution for 30 min under stirring, and then each membrane was immersed in 150 \(\upmu\)L of MeOH for 30 min for analyte back-extraction. Subsequently, the eluant was tested and the following parameters were optimized: extraction time, elution solvents and mixtures, back extraction time, and volume. After the selection of optimal conditions using standard solutions, the optimization was performed on the biological complex matrices mentioned previously [59]. In the same way, [PERSON] et al. have optimized all parameters to obtain the maximum extraction of twelveazole antimicrobial drug residues from human plasma and urine. They have investigated three different FPSE membranes and the different dimensions of these to study the optimum sample volume and the optimum extraction media dimension [36]. [PERSON] et al. have used this simple and powerful technique combined with HPLC-DAD for the simultaneous monitoring of three anti-inflammatory drugs (ciprofloxacin, sulfasalazine, and cortisone) administered in the treatment of inflammatory bowel disease. Figure 2: Comparison between solid-phase extraction (SPE) and fabric phase sorptive extraction (FPSE). They have tested five different FPSE media membranes coated with different sorbents and different extraction parameters to develop an extraction procedure for molecules that are characterized by a wide range of LogP [31]. [PERSON] et al. have combined FPSE-extraction with HPLC-fluorimetric detection to simultaneously quantify Febuxostat and Montelukast in human blood [60]. Recently, FPSE extraction was also used by [PERSON] et al. to extract an anti-viral drug from breast milk [61] and was also applied for in vivo non-invasive exhaled breath aerosol sampling to monitor the exposure to xenobiotics by [PERSON] et al. [62] and other xenobiotics [63; 64]. The amazing benefits of FPSE as a new-generation sample preparation technique were further manifested in a study presented by [PERSON] et al. [65], where FPSE was combined with UPLC-ESI-MS/MS to monitor the presence of residual antiviral drugs, including amantadine, mementante, and rimantadine in human urine. Sol-gel poly(propylene glycol)-poly(ethylene glycol)-poly(propylene glycol)-coated FPSE membranes reached extraction equilibrium in just 20 min, thanks to the rapid mass transfer of the target analytes from the bulk of the sample to the FPSE membrane due to the engineered affinity of the sol-gel sorbent towards the target analytes via different intermolecular interactions and the sponge-like porous structure of the sol-gel sorbent. A matrix-matched calibration curve was developed in the range of 5-100 ng ml\({}^{-1}\) to aid the quantitative analysis of the target analytes in the unknown clinical samples. The FPSE combined with UPLC-ESI-MS/MS method provides LOD values in the range of 0.2-0.8 ng/mL and LOQ value of 5 ng/mL for all target analytes.