Determination of phenoxyethanol, methyl 4-hydroxybenzoate, and propyl 4-hydroxybenzoate in cosmetics by high-performance liquid chromatography

Objective To establish a method for determining phenoxyethanol, methyl 4-hydroxybenzoate, and propyl 4-hydroxybenzoate in cosmetic products based on high-performance liquid chromatography(HPLC).

Methods The samples were extracted by ultrasonic extraction with methanol and filtered by 0.45 μm PTFE filter membrane. High-performance liquid chromatography was performed on a ZORBAX SB-C₁₈ (150 mm×4.6 mm, 5 μm) column with a mobile phase of methanol, acetonitrile, and 0.02 mol/L ammonium acetate (pH=4.0) for gradient elution, and a diode array detector was used for determination.

Results Phenoxyethanol, methyl 4-hydroxybenzoate, and propyl 4-hydroxybenzoate showed a good linear relationship within the range of 242-20 000, 14.6-4 000, and 6.6-4 000 mg/kg, respectively, with a correlation coefficient of >0.999, a recovery rate of 90.4%-104%, and intra-and inter-day precisions of < 9.2%. The method was used in the proficiency test to determine the content of preservatives in cosmetics, and satisfactory results were obtained.

Conclusion This method is simple, rapid, accurate, and stable and is suitable for the simultaneous determination of phenoxyethanol, methyl 4-hydroxybenzoate, and propyl 4-hydroxybenzoate in cosmetics.