## 4 Conclusions  
The great variety of cosmetic products and the complexity of their composition leads to the need for sensitive and versatile analytical methods suitable for the detection of different target analytes. The continuous evolution of regulated and prohibited substances for cosmetic purposes also necessitates frequent checks and large-scale screening, which can highlight the presence of any substances added illegally to the formulations. For this reason, a rapid and easy-to-use method such as immunoassay can represent a valid alternative to reference benchtop methods such as HPLC-MS. In this work, we therefore developed and compared two analytical methods based on different principles. The first was an ad-hoc optimized HPLC-MS method to identify and quantify eight corticosteroids. The second was a bioanalytical immunoassay based on ELISA technology for the detection of corticosteroids in cosmetic matrices. Compared to previous works [20, 28, 29, 30] (Table 5), the LC-MS sensitivity is similar if not greater, in the order of 0.02-0.2 ng/mL (LOD) for creams and 0.1-0.5 ng/mL (LOD) for serum. Together with the high sensitivity, another advantage of the presented method over the previous ones is the simple sample preparation without any pretreatment like solid-phase extraction [52, 53], surfactant-based ultrasound-assisted dispersive liquid-liquid microextraction [54], or microwave-assisted extraction [55]. The detectability offered by the biospecific assay is comparable to those in the literature [35, 44] and that obtained by HPLC-MS. In this context, the detected concentration ranges for both methods are compatible with the concentrations of corticosteroids that are commonly added to cosmetics illegally. Indeed, to obtain a significant effect on skin aesthetics, the concentration of corticosteroids should comprise between 0.2 and 2% (\(w/v\)) [56]. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Stereid** & \begin{tabular}{l} **LQO** \\ **ing mL-1** \\ \end{tabular}  & **Linearity Range** & **Sample Preparation** & **Technique** & **Ref. ** \\ \hline Montacstonestonestonestone & 12.5 & 0.0125–2 (mg mL-1) & HPLC-DAD & \\ Hydrocertisone acetate & 15.652 & 0.01563-5 (mg mL-1) & The extraction of 1 g of amphiphilic cream by 10 mL of acetonitrile & \\ Fluorcinomide & 9 & 0.009–2.88 (mg mL-1) & was performed in an ultrasonic bath for 10 min at room & [29] \\ Flucinolone acetate & 31.25 & 0.03125-75 (mg mL-1) & temperature. The extract was filtered through a 0.45 nm cellulose & \\ Betamethasone & 21 & 0.0216-72 (mg mL-1) & acetate filter and then injected into the HPLC system. & \\ Betamethasone dipropionate & 10.5 & 0.01505-3.36 (mg mL-1) & Titanium medicine acetonate & 21 & 0.0105–6.72 (mg mL-1) & \\ \hline \hline
17\(\Delta\)=Stradiol & 0.79 & 0.6285–125 (mg mL-1) & A total of 20 mL of cosmetic sample were transferred to a 50 mL & RP-HPLC-UV \\
17\(\Delta\)=Ethinylestradiol & 0.63 & 0.6255–125 (mg mL-1) & polyfenafluoroethylene (PTH) centrifuge tube. A total of 0.6 g of NaCl was added and 1 mol/1. NaOH was was used to adjust the pH \\ Extrone & 0.59 & 0.6255–125 (mg mL-1) & value to 10. After criteria mixing to 30, 80 mL of 1, cGMP(SHT)H\({}_{x}\) & \\
17\(\Delta\)=Hydroxyprogesterone & 0.23 & 0.25-50 (mg mL-1) & 1 homogenized for 10 s. A total of 1 ml of water solution containing & \\ Medwayprogesterone & 0.30 & 0.25-50 (mg mL-1) & 0.3588 g of NH4 PFs was added. A cloudy solution was formed as a & \\ result of the formation of fine droplets of \(\{\rm\zeta,\However, as regards the performance of the method in terms of specificity, precision, recovery, and matrix effect in the quantification of the target analytes, the HPLC-MS technique performs much better. Despite this, the possibility of exploiting a rapid, easy-to-use, low-cost, and high-throughput technique such as immunoassay for large-scale preliminary screening would be useful for the purposes of frequent checks on cosmetic products.