A fast and simple method for the extraction and Flame Atomic Absorption Spectroscopy (FAAS) quantification of ZnO in different cosmetic matrices, including lipsticks, water-in-oil foundations, and oil-in-water creams, was developed and validated, according to the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) and the United States Pharmacopeial Convention guidelines. The sample preparation consisted of an ultrasound-assisted ethanolic extraction of ZnO followed by digestion with 1 M nitric acid (HNO₃). Samples were analyzed by Flame Atomic Absorption Spectroscopy (FAAS). Specificity, linearity, the limit of detection (LOD), the limit of quantification (LOQ), sensitivity, precision, and accuracy parameters were studied. The robustness of the method was evaluated with a five-variable Youden–Steiner model. The method was specific for ZnO, and the extraction procedure did not affect the stability of the signal compared to the background. The method was linear in the range 0.2–1.0 mg/L with LOD/LOQ values equal to 0.0156 (mg·L⁻¹)/0.0473 (mg·L⁻¹), 0.0098 (mg·L⁻¹)/0.0297 (mg·L⁻¹), 0.0113 (mg·L⁻¹)/0.0341 (mg·L⁻¹), and 0.0131 (mg·L⁻¹)/0.0397 (mg·L⁻¹), respectively, for raw material, lipstick, liquid foundation, and emulsion matrices. Regarding precision, the %RSD values were below 3.0% for repeatability and intermediate precision. Global reproducibility RSD was below 8.0% for all matrices. The percentage of recovery was not statistically different from 100% in all cases. The final concentration was found to be a critical variable for all matrices except for the raw material. The variables associated with the extraction step (ethanol volume, bath temperature, and extraction time) were critical in the extraction of liquid foundations and cream emulsions. The method reduces the number and concentration of mineral acids spent on the digestion of ZnO, and its application is extendable to raw materials. This development is an adequate tool for routine analysis and cosmetic quality control of chemically different products that contain ZnO as ultraviolet radiation (UV) filter, to guarantee regulatory compliance and ensure the safety and efficacy of products delivered to consumers.

中文翻译：

---

火焰原子吸收光谱法分析化妆品基质中氧化锌的方法的开发和验证

开发并验证了一种快速、简单的方法，用于提取和火焰原子吸收光谱 (FAAS) 量化不同化妆品基质中的 ZnO，包括口红、油包水粉底和水包油面霜。国际人用药物技术要求协调委员会 (ICH) 和美国药典公约指南。样品前处理包括超声波辅助乙醇提取 ZnO，然后用 1 M 硝酸 (HNO ₃）。通过火焰原子吸收光谱法 (FAAS) 分析样品。研究了特异性、线性、检测限 (LOD)、定量限 (LOQ)、灵敏度、精密度和准确度参数。该方法的稳健性通过五变量 Youden-Steiner 模型进行评估。该方法对 ZnO 具有特异性，与背景相比，提取过程不会影响信号的稳定性。该方法在 0.2–1.0 mg/L 范围内呈线性，LOD/LOQ 值等于 0.0156 (mg·L ^-1 )/0.0473 (mg·L ^-1 )、0.0098 (mg·L ^-1 )/0.0297 (mg ·L ^-1）、0.0113（mg·L ^-1）/0.0341（mg·L ^-1）和0.0131（mg·L ^-1）/0.0397（mg·L⁻¹)，分别用于原料、口红、粉底液和乳液基质。关于精密度，重复性和中间精密度的 %RSD 值低于 3.0%。所有基质的全局重现性 RSD 均低于 8.0%。在所有情况下，恢复百分比与 100% 没有统计学差异。发现最终浓度是除原材料以外的所有基质的关键变量。与提取步骤相关的变量（乙醇体积、浴温和提取时间）对于粉底液和乳霜乳液的提取至关重要。该方法减少了用于消化氧化锌的无机酸的数量和浓度，其应用可扩展到原料。