摘要：Simple and reliable methods for the qualitative and quantitative analysis of ultraviolet (UV) absorbers in cosmetics by two dimension NMR (2D-NMR) were presented. The procedure consists of the following direct method for the samples containing more than 2% of UV absorbers and of the concentration method for the samples containing less than 2% of UV absorbers. The direct method : One hundred to 300 mg of cosmetics was weighed, placed into a test tube, and added 2 ml of saturated sodium chloride solution and 1 ml of the CDCl3 solution containing 1% of pyrazine and 0.5% of tetramethylsilane. The mixture was shaken for 10 min. and centrifuged at 3000 rpm for 10 min. The CDCl3 solution was transferred into a NMR tube. The concentration method : Five to 50 g of samples was weighed, placed into a 200 ml separating funnel, added 80 ml of saturated sodium chloride solution, and extracted with 30 ml of chloroform for 3 times. The chloroform layer was evaporated to dryness under reduced pressure. The residue was dissolved in 1 ml of the CDCl3 solution for NMR measurements as described in the direct method. The 13C-1H heteronuclear shift correlated NMR spectra (HETCOR) of UV absorbers in the CDCl3 solution were measured for the simultaneous qualitative analysis of UV absorbers by the fingerprint identification, and the relative integral intensity in their 1H-NMR signals was used for the quantitative analysis using pyrazine as an internal standard. The proposed methods were successfully applied to the analysis of UV absorbers in cosmetics.
