GC-MS/MS Determination of 12 UV Absorbers in Sunscreening Cosmetics

A portion (5.0 g) of the sunscreening cosmetic sample was mixed thoroughly with 1 mL of saturated NaCl solution and extracted twice with CH₂Cl₂ (5 mL for each extraction) to transfer 12 UV absorbers (UVA) into the organic solvent by swirling for 60 s, extracting ultrasonically for 30 min and centrifuging for 5 min with high speed. The supernatants from the 2 extractions were combined and evaporated to near dryness by N₂-blowing. The residue was dissolved and made its total volume to 1.0 mL with CH₂Cl₂. An aliquot of 1 μL of the CH₂Cl₂ solution was introduced to the chromatographic column of DB-5MS for separation of the 12 UVA under the mode of programed temperature elevation in the temperature interval from 80℃ to 300℃. A clear-cut separation of the 12 UVA was fulfilled within 30 min and their determination was carried out by MS/MS under the modes of EI-ionization source and selected reaction monitoring. Linearity ranges for the 12 UVAs were found same between 0.01-1.0 mg·L^-1. Values of their detection limits (3S/N) found were in the range of 1.0 to 3.0 μg·kg^-1. Test for recovery and precision was performed by addition of mixed standard solution of the 12 UVA to a blank sunscreening cosmetic sample, giving results of recovery in the range from 93.0% to 100%, and results of RSDs (n=6) in the range from 1.2% to 4.1%.