# Recent Advances in Sample Preparation for Cosmetics and Personal Care Products Analysis
## 2 Sample Preparation Strategies for Cosmetics Analysis
### Ultrasound-Assisted Extraction (UAE)  
The fundament of UAE is based on the cavitation phenomena [76]: the creation of small bubbles in the solvent due to the passage of ultrasound waves allowing for a greater penetration of the solvent within the material, thus increasing the surface area. From a GAC point of view, UAE is greener than classical LLE or SLE [77]. The inclusion of ultrasound energy assisting solvent extraction allows the use of less solvents, reducing the extraction time, costs, and improving the extraction yield.  
UAE has been applied to cosmetics to extract UV filters, preservatives, synthetic musks, amino acids, or natural pigments [31; 32; 33; 34; 35; 36; 37; 38] from a broad range of matrices including leave-on and rinse-off cosmetics, as well as specific products such as tattoos. The most used solvents for UAE have been water [31; 33], MeOH [34; 38], EtOH [37], or the combination of different organic solvents [32] or water before LC analysis, whereas hexane and ethyl acetate have been the preferred ones before GC analysis [35; 39]. For amino acids analysis, an in situ derivatization was implemented, employing 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) [36]. In all cases, quantitative recoveries, and low values for relative standard deviation (RSD) and LODs were obtained.  
Additionally, UAE has been successfully proposed for the multianalyte determination of 70 compounds including fragrances, plasticizers and preservatives in baby wipes, masks as well as in extreme cosmetics and borderline products [39]. The possible transfer of plasticizers from the plastic applicators to the cosmetics matrices, and thereby to the consumers, were evaluated, employing a modified version of the classical UAE, called supported-UAE (Sup-UAE). In this approach, a small amount of cosmetic sample (0.05 g) was applied with its corresponding applicator on a small piece (3 \(\times\) 2.4 cm\({}^{2}\)) of filter paper sheet. Sup-UAE performance was compared with \(\upmu\)-MSPD and classical UAE, obtaining similar results in terms of recovery and precision, demonstrating its suitability, and giving additional information about plasticizers' migration from cosmetics applicators [39].  
The use of UAE combined with cloud-point extraction (CPE) is a simple, low-cost, and sustainable option. It reduces solvent consumption and extraction time, providing high analyte enrichment factors. UAE-CPE has been applied for the extraction of free formaldehyde from hair products [40]. Determination was performed by UV-Vis, obtaining a LOD lower than 0.4 \(\upmu\)g L\({}^{-1}\). The use of ultrasonic-assisted closed in-syringe extraction and derivatization (UCSED) was performed for the determination of two labile resin acids [41]. The procedure included in situ derivatization with 2-(2-(anthracen-10-yl)-1H-naphtho[2,3-d]imidazol-1-yl)ethyl-p-toluenesulfonate (ANITS) and the analysis of HPLC-DAD, and online MS/MS to ensure the confirmation of the target analytes presence in a broad range of cosmetics matrices. In general, UAE performance in terms of accuracy, precision and LODs was similar to that LLE or SLE (see Table 1). However, after UAE, no further clean-up steps before analysis were necessary, reducing the extraction time, whereas after LLE or SLE, a clean-up step, mainly by SPE, is usually implemented [22; 23; 29].