# New Challenges in (Bio)Analytical Sample Treatment Procedures for Clinical Applications
## 3 Sample Preparation Techniques for Diagnostic Purposes
### Fabric Phase Sorptive Extraction (FPSE)  
Fabric phase sorptive extraction (FPSE) is an innovative technique developed by [PERSON] and [PERSON] [56] that offers a substantial simplification of the selective extraction of the target analytes from biological samples. Nowadays, thanks to the new analytical methods based on FPSE, it is possible to determine low concentrations of analytes with no/minimal sample pretreatment. In addition, the several steps operations in the treatment of complex biological matrices (for example, whole blood, urine, saliva, etc. ), such as protein precipitation, sonication, elution of extract in an organic solvent, solvent evaporation and sample reconstitution, elution of extract, and more, are often the cause of most of the errors during the analytical process and can be eliminated from the sample preparation workflow when FPSE is used [57]. Briefly, when the FPSE membrane is immersed into the aqueous sample, the analyte(s) permeates through the sol-gel sorbent, such as an SPE disk, and establishes intermolecular interactions, such as an SPE disk. However, at the same time, the analyte(s) continue to accumulate on the FPSE membrane based on the partition coefficient between the sol-gel sorbent and the sample matrix. Therefore, this novel technique combines both the exhaustive extraction principle and the equilibrium-driven extraction principle by design [58]. [PERSON] et al. used three FPSE media membranes, in particular, sol-gel poly (dimethyldiphenylsiloxane) (sol-gel PDMDPS), sol-gel poly (tetrahydrofuran) (sol-gel PTHE), and sol-gel poly (ethylene glycol) (sol-gel PEG) to determinate benzodiazepines from human blood serum. The authors demonstrated the simplicity of this extraction in \begin{table}
\begin{tabular}{c c c c} \hline
**Target Analytics** & **Matrix** & **Extraction Technique** & **Analytical Characteristics** & **Ref.** \\ \hline Dopamine (DA), & & & \\ Norepinephrine (NE), & & & \\ Metanephrrine (MN), & & & \\ Normetanephrine (NMN), & & & \\ L-3,4,+ & & & MN: LOD 1 ng/mL \\ dihydroxyphenylalanine & & & NMN: LOD 1 ng/mL \\ (L-DOPA), Epinephrine & & & L-DOPA: LOD 20 ng/mL \\ (E), Epinephrine-d6 (E-d6), & & & E: LOD 1 ng/mL \\ Metanephrine-d3 & & & E-d6: LOD 1 ng/mL \\ Normetanephrine-d3 & & & MN-d3: LOD 1 ng/mL \\ (NMN-d3), Serotonin & & & NMN-d3: LOD 1 ng/mL \\ (5-HT), Testosterone (T), & & & 5-HT: LOD 1 ng/mL \\ Epitestosterone (EpiT), & & & T: LOD 1 ng/mL \\ Dihydrotestosterone & & & EPI: LOD 1 ng/mL \\ (DHT), & & & DHT: LOD 1 ng/mL \\
17-hydroxy progesterone & & & 17-OHP: LOD 1 ng/mL \\ (17-OHP); & & & A: LOD 1 ng/mL \\ Androstenedione (A), & & & P4: LOD 1 ng/mL \\ Progesterone (P4), & & & EpiT-d3: LOD 1 ng/mL \\ Epitestosterone-d3 & & & \\ (EpiT-d3) & & & \\ Norepinephrine(NE) & Artificial urine & Rotating-disk sorptive extraction technique (RDSE) & NE: LOD 11.3 ug L\({}^{-1}\), LLOQ 34.0 ug L\({}^{-1}\) \\ Epinephrine (EPI), & & & EPI: LOQ 0.167 ng/mL, LOD 0.0800 ng/mL \\ Norepinephrine (NE), & & & NE: LOQ 0.650 ng/mL, LOD 0.300 ng/mL \\ Dopamine (DA), & & & DA: LOQ 1.53 ng/mL, LOD 0.530 ng/mL \\ Metanephrine (MN), & & & MN: LOQ 0.440 ng/mL, LOD 0.176 ng/mL \\ Normetanephrine (NMN), & & & NMN: LOQ 1.10 ng/mL, LOD 0.440 ng/mL \\
3-methoxyramine & & & 3-MT: LOQ 0.880 ng/mL, \\ (3-MT) & & & LOD 0.176 ng/mL \\ \hline \end{tabular}
\end{table} 
Table 2: Cont. terms of the number of operations in comparison with other innovative techniques, such as SPE [57]. Figure 2 compares the steps involved in SPE and FPSE. As shown above, [PERSON] et al. integrate the FPSE with HPLC-DAD for separation and quantification of anastomogle, letrozole, and exemestane from whole blood, plasma, and urine. The first step was the creation of a sol-gel sorbent coated membrane as follows: the selection of appropriate substrate and its pre-treatment, the design of the most appropriate sol solution to obtain maximum selectivity, the coat the pre-treated fabric substrate with sol-gel sorbent, and the condition and clean the FPSE membrane.