Esteki M, Nouroozi S, Shahsavari Z
Department of Chemistry, University of Zanjan, Zanjan, 45195-313, Iran.
Int J Cosmet Sci. 2016 Feb;38(1):25-34. doi: 10.1111/ics.12241. Epub 2015 Jun 11.
To develop a simple and efficient spectrophotometric technique combined with chemometrics for the simultaneous determination of methyl paraben (MP) and hydroquinone (HQ) in cosmetic products, and specifically, to: (i) evaluate the potential use of successive projections algorithm (SPA) to derivative spectrophotometric data in order to provide sufficient accuracy and model robustness and (ii) determine MP and HQ concentration in cosmetics without tedious pre-treatments such as derivatization or extraction techniques which are time-consuming and require hazardous solvents.
The absorption spectra were measured in the wavelength range of 200-350 nm. Prior to performing chemometric models, the original and first-derivative absorption spectra of binary mixtures were used as calibration matrices. Variable selected by successive projections algorithm was used to obtain multiple linear regression (MLR) models based on a small subset of wavelengths. The number of wavelengths and the starting vector were optimized, and the comparison of the root mean square error of calibration (RMSEC) and cross-validation (RMSECV) was applied to select effective wavelengths with the least collinearity and redundancy. Principal component regression (PCR) and partial least squares (PLS) were also developed for comparison. The concentrations of the calibration matrix ranged from 0.1 to 20 μg mL(-1) for MP, and from 0.1 to 25 μg mL(-1) for HQ. The constructed models were tested on an external validation data set and finally cosmetic samples.
The results indicated that successive projections algorithm-multiple linear regression (SPA-MLR), applied on the first-derivative spectra, achieved the optimal performance for two compounds when compared with the full-spectrum PCR and PLS. The root mean square error of prediction (RMSEP) was 0.083, 0.314 for MP and HQ, respectively. To verify the accuracy of the proposed method, a recovery study on real cosmetic samples was carried out with satisfactory results (84-112%).
The proposed method, which is an environmentally friendly approach, using minimum amount of solvent, is a simple, fast and low-cost analysis method that can provide high accuracy and robust models. The suggested method does not need any complex extraction procedure which is time-consuming and requires hazardous solvents.
开发一种结合化学计量学的简单高效分光光度技术，用于同时测定化妆品中的对羟基苯甲酸甲酯（MP）和对苯二酚（HQ），具体目标如下：（i）评估逐次投影算法（SPA）对导数分光光度数据的潜在应用，以提供足够的准确性和模型稳健性；（ii）无需诸如衍生化或萃取技术等繁琐的预处理来测定化妆品中MP和HQ的浓度，这些预处理既耗时又需要使用危险溶剂。
在200 - 350 nm波长范围内测量吸收光谱。在执行化学计量学模型之前，二元混合物的原始和一阶导数吸收光谱用作校准矩阵。通过逐次投影算法选择的变量用于基于一小部分波长获得多元线性回归（MLR）模型。对波长数量和起始向量进行了优化，并应用校准均方根误差（RMSEC）和交叉验证均方根误差（RMSECV）的比较来选择具有最小共线性和冗余性的有效波长。还开发了主成分回归（PCR）和偏最小二乘法（PLS）进行比较。MP校准矩阵的浓度范围为0.1至20 μg mL⁻¹，HQ为0.1至25 μg mL⁻¹。构建的模型在外部验证数据集以及最终的化妆品样品上进行测试。
结果表明，与全光谱PCR和PLS相比，应用于一阶导数光谱的逐次投影算法 - 多元线性回归（SPA - MLR）对两种化合物实现了最佳性能。MP和HQ的预测均方根误差（RMSEP）分别为0.083和0.314。为验证所提方法的准确性，对实际化妆品样品进行了回收率研究，结果令人满意（84 - 112%）。
所提方法是一种环境友好的方法，使用最少的溶剂，是一种简单、快速且低成本的分析方法，能够提供高精度和稳健的模型。该方法无需任何耗时且需要危险溶剂的复杂萃取程序。
