Hsiao Wen-Yao, Jiang Shiuh-Jen, Feng Chia-Hsien, Wang Shih-Wei, Chen Yen-Ling
Department of Fragrance and Cosmetic Science, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan.
Department of Chemistry, College of Science, National Sun Yat-Sen University, Kaohsiung, Taiwan.
J Chromatogr A. 2015 Feb 27;1383:175-81. doi: 10.1016/j.chroma.2015.01.039. Epub 2015 Jan 21.
The on-line preconcentration technique of analyte focusing by micelle collapse-micellar electrokinetic chromatography (AFMC-MEKC) was combined with direct injection without extraction to determine ultraviolet absorbents in sunscreen products. The stacking mechanism is based on the transport, release, and accumulation of analytes bound to micelle carriers that are collapsed into the micelle dilution zone. The following optimized conditions were determined: the running buffer was 10mM Tris buffer (pH 9.5) containing 60mM SDS, 7mM γ-CD and 20% ethanol; the SDS concentration was required to be slightly above the critical micelle concentration (cmc) value (7.4mM) in the sample matrix, which allowed the micelle dilution zone to form when voltage was applied; and finally, the sample was prepared in 100mM Tris buffer (pH 9.0) containing 7.5mM SDS and 20% (v/v) ethanol to provide sufficient resolution and to improve the sensitivity. Samples were injected at 0.5psi for 40s, and the separation voltage was set at 15kV for first 15min and then increased to 23kV to decrease the analysis time. The detection sensitivity for ultraviolet absorbents was enhanced by approximately 41-fold using AFMC-MEKC compared to conventional MEKC. The limit of detection (S/N=3) was 98nM for benzophenone-2 and benzophenone-4. The correlation of the regression curve was greater than 0.995. The relative error and relative standard deviation were lower than 9.94% with high precision and accuracy. The recoveries of nine ultraviolet absorbents in a homemade emulsion were between 95.08% and 104.57%. After optimization and validation, this AFMC-MEKC method combined with direct injection is considered to be established and successfully applicable to commercial sunscreen products.
将胶束塌陷-胶束电动色谱法（AFMC-MEKC）的在线分析物聚焦预富集技术与无需萃取的直接进样相结合，用于测定防晒产品中的紫外线吸收剂。堆积机制基于与胶束载体结合的分析物的传输、释放和积累，这些胶束载体塌陷到胶束稀释区。确定了以下优化条件：运行缓冲液为含有60mM SDS、7mM γ-环糊精和20%乙醇的10mM Tris缓冲液（pH 9.5）；SDS浓度需略高于样品基质中的临界胶束浓度（cmc）值（7.4mM），施加电压时可形成胶束稀释区；最后，样品在含有7.5mM SDS和20%（v/v）乙醇的100mM Tris缓冲液（pH 9.0）中制备，以提供足够的分离度并提高灵敏度。样品以0.5psi进样40s，分离电压在最初15min设定为15kV，然后升至23kV以缩短分析时间。与传统MEKC相比，使用AFMC-MEKC时紫外线吸收剂的检测灵敏度提高了约41倍。二苯甲酮-2和二苯甲酮-4的检测限（S/N = 3）为98nM。回归曲线的相关性大于0.995。相对误差和相对标准偏差低于9.94%，具有高精度和准确性。自制乳液中九种紫外线吸收剂的回收率在95.08%至(104.57%)之间。经过优化和验证，这种结合直接进样的AFMC-MEKC方法被认为已确立，并成功应用于商业防晒产品。
