Simultaneous Analytical Method for Various Paraben and Alcohol Preservatives in Supposedly Natural and Organic Cosmetics by Off-line SPE–UHPLC–DAD and LC–MS/MS

Preservatives can be used in natural and organic cosmetics to prevent quality deterioration during distribution and use, but the ingredients permitted are limited in the Republic of Korea. A method of simultaneous analysis was developed to monitor natural and organic cosmetics distributed online for the presence of 15 illegally used preservatives. Considering the complexities of the cosmetic matrices, an optimized sample preparation method is essential. Therefore, we developed the optimal purification method by comparing three preparation methods: QuEChERS, high-speed centrifugation, and solid-phase extraction (SPE). The SPE method, which exhibited the most favorable results in matrix reduction, was employed. To establish the SPE-ultra-high-performance liquid chromatography-diode array detection method, factors such as the mobile phase and column were optimized. The optimal separation of the 15 preservatives was observed under the following conditions: mobile phase A comprising 0.1% phosphoric acid in water with 0.5 mM sodium hexanesulfonate and a C₈ column (1.7 μm, 2.1 × 150 mm) as the stationary phase. The linear correlation coefficients were > 0.9998, and the limits of detection and quantitation ranged from 0.05 to 0.67 and 0.15 to 2.02 μg mL⁻¹, respectively. Using the established analytical method, illegally used preservatives were detected in products claimed to be natural and organic cosmetics sold on the market, and these findings were subsequently verified using liquid chromatography-tandem mass spectrometry. Six out of 47 samples contained phenoxyethanol and parabens. Therefore, this method will help manage the addition of illegal preservatives to natural and organic cosmetics.