Measuring estriol and estrone simultaneously in liquid cosmetic samples using second-order calibration coupled with excitation–emission matrix fluorescence based on region selection

This paper describes a sensitive excitation–emission matrix fluorescence (EEM) method for simultaneously measuring contents of two estrogens, estriol (E3) and estrone (E1), in liquid cosmetic samples with the aid of a second-order calibration method based on a parallel factor analysis (PARAFAC) algorithm. Before processing the obtained three-way data, a better region of the excitation and emission spectra was purposely selected. Then PARAFAC was recommended to acquire the clean spectra and predict the individual concentrations of the analytes of interest even in the presence of uncalibrated interferences. The standard curves of the two analytes are linear within a linear concentration range of 0–0.736 μg mL−1 of E3 and 0–18.000 μg mL−1 of E1 with correlation coefficients typically greater than 0.99. In the analysis of watermelon frost anti-acne toner sold on the internet web site, the limit of detection (LOD) of E3 is 4.7 ng mL−1 with an accuracy of 102.3–113.7%, and for E1, the LOD is 96.1 ng mL−1 with an accuracy of 92.3–111.0%. In the analysis of pagoda flower relaxing lotion from the commercial market in Changsha, the LOD of E3 is 8.9 ng mL−1 with an accuracy of 95.0–107.1%, and for E1, the LOD is 76.9 ng mL−1 with an accuracy of 98.6–119.3%. Generally, a new avenue has been opened up to determine estrogens quantitatively in cosmetic samples. This methodology will achieve greater development and gradually become a more routine approach in cosmetic quality control due to its advantages of high sensitivity, simple pretreatment procedure and non-destructive nature.