# Recent Advances in Sample Preparation for Cosmetics and Personal Care Products Analysis
## 2 Sample Preparation Strategies for Cosmetics Analysis
### Microextraction Techniques for Cosmetic Analysis
#### 2.7.2 Sorbent-Based Microextraction Techniques  
Although LPME approaches are simple and do not require expensive apparatus, they usually require several steps, and their automation is more complex than that required by sorbent-based microextraction techniques. In addition, the sorbent material can usually be reused, and the procedure implies minimum solvent consumption or even completely eliminating the organic solvents in the whole experimental procedure. Besides, a wider variety of sorbent-based microextraction techniques have been developed in recent years in comparison to LPME, likely due to the versatility of different sorbent materials that can be (i) packed in a small device; (ii) dispersed along the sample matrix, or (iii) coated on a solid support [143]. The most employed sorbent-based microextraction technique for cosmetics analysis has been solid-phase microextraction (SPME); however, in recent years, the application to cosmetics of recently developed sorbent-based microextraction techniques such as fabric phase sorptive extraction (FPSE) or stir bar sorptive dispersive microextraction (SBSDME) is increasing with promising results. The most relevant methodologies are included in Table 2 and are commented on below. Solid-Phase Microextraction (SPME)  
SPME was introduced in 1989 by [PERSON] et al. [144]. Nowadays, it is a well-established green solvent-free extraction technique with a large number of applicationsin different fields such as food, forensic, biomedical and the environment [145]. One of the main advantages of SPME is that extraction and analytes' pre-concentration are performed in a single step. In addition, SPME allows the possibility to directly sample the vapour phase in equilibrium with the matrix (headspace (HS) mode), or the matrix extract or solution (direct immersion (DI) mode). Nowadays, a high number of commercially available SPME fibres exist, such as polydimethylsiloxane (PDMS), polyacrylate (PA), polydimethylsiloxane/divinylbenzene (PDMS/DVB), carboxen (CAR) or polydimethylsiloxane/divinylbenzene/carboxen (PDMS/DVB/CAR), among others. The fibre coating selection depends on the target analytes' properties. Two of the most employed ones for cosmetics analysis were PDMS/DVB and PDMS/DVB/CAR, used to extract fragrance allergens or preservatives [123; 124; 125], showing good performance in terms of accuracy, precision and low LODs. However, in recent years, trends in SPME for cosmetics are moving towards the development of novel sorbent coatings since commercially available fibre coatings are limited and restrict the wide application of this microextraction technique, especially for multitarget analysis. In this sense, the aluminium hydroxide grafted fused silica SPME fibre was successfully prepared by means of a grafting process for the first time to determine the n-nitrosamine NDELA in cosmetics. The homemade fibre showed good thermal stability, up to 500 \({}^{\circ}\)C, as well as a satisfactory repeatability with RSD values lower than 6% [129]. A poly(ethylene glycol) diacrylate (PEG-DA) fibre was proposed to determine parabens in cosmetics products [130]. The PEG-DA polymer coating was covalently attached to the fibre by introducing a surface modification with 3-(trichlorosil)propyl methacrylate (TPM). This approach leads to an increase in the surface area, improving the extraction efficiency and showing good repeatability (fibre-to-fibre), although obtained LODs were higher than those provided by commercial fibres [124; 127]. The use of single-layer graphitic carbon nitride-modified graphene composite (C\({}_{3}\)N\({}_{4}\)@G), as well as \(\beta\)-cyclodextrintrin/graphene oxide-modified fibres were employed for the extraction of PAHs and fragrances, respectively [131; 132]. In most cases, GC analysis was carried out after SPME [123; 124; 125; 127; 128; 129; 131; 132], directly performing analytes' desorption in the instrument injector--although LC analysis has also been employed [130].