# New Challenges in (Bio)Analytical Sample Treatment Procedures for Clinical Applications
## 1 Introduction  
The analysis of biological samples requires an adequate sample preparation procedure that has an inevitable role in the analytical process. In fact, the sample preparation step may influence the accuracy of results and consumes most of the time needed for the overall analytical workflow.  
The traditional methods applied in many fields, including bioanalysis, such as solid-phase extraction (SPE) and liquid-liquid extraction (LLE), have shown some limitationsdue to their use of toxic organic solvents and long processing times; therefore, new methods based on microextraction techniques have been developed to achieve a high recovery of target analytes from simple to complex sample matrices and to comply with the concepts of Green Chemistry (GC) and Green Analytical Chemistry (GAC) [1].  
Biological samples include whole blood, plasma, serum, urine, feces, saliva, bile, hair, sweat, breast milk, cerebrospinal fluid (CSF)), and tissues, and bio analytes (DNA, defined proteins, drugs, and specific metabolites or unknown molecules).  
The stability of these samples is important. They are often rich in endogenous components, such as carbohydrates, proteins, lipids, and salts, which can interfere with the target analytes due to matrix effects. Moreover, analytes are often present at very low concentrations, and for this reason, the target analytes need to be preconcentrated prior to analysis. This often enhances the levels of interfering molecules (e.g., drugs, salts and metabolites, nucleic acids, proteins, and peptides) [2].  
After collection from patients and appropriate storage, the sample clean-up and preparation step become crucial to avoid damage also caused by endogenous degrading properties (enzymes activities, cell death, etc.) and to perform an accurate and selective bioanalysis to obtain a real and correct \"picture\" of the studied system [3].  
These sample preparation techniques include liquid phase microextraction (LPME) with its different modifications such as single-drop microextraction (SDME), dispersive liquid-liquid microextraction (DLLME), hollow fiber liquid-phase microextraction (HF-LPME) and solidified floating organic drop microextraction (SFO-DME). In LPME, the extraction phase is based on the action of different solvents (e.g., DESs, ILs, and ferrofluids) that, with their features and properties, play an important role for the entire process (in terms of recovery, enrichment factor, selectivity).  
Other techniques include solid phase microextraction (SPME), microextraction by packed sorbent (MEPS), and fabric phase sorptive extraction (FPSE) [4; 5]. These techniques manifest a rapid development in different fields, such as biological, environmental, food sciences, natural products, forensic medicine, and toxicology [1].  
The clinical applications of (bio)analytical sample treatment procedures are very extensive in different fields, ranging from the search for biomarkers useful in the diagnosis of many diseases to those necessary for personalized therapeutic drug monitoring (TDM).  
In this review, the attention is focused primarily on the clinical applications of these procedures, highlighting the major advantages and results that have been made in laboratory and clinical practices.