DETERMINATION OF THE SUNSCREEN 2-ETHYLHEXYL-P-DIMETHYLAMINOBENZOATE IN COSMETICS BY REVERSED-PHASE HPTLC WITH ULTRAVIOLET-ABSORPTION DENSITOMETRY ON PREADSORBENT PLATES

A quantitative high-performance thin-layer chromatographic (HPTLC) met hod has been developed for the determination of the sunscreen ingredie nt 2-ethylhexyl-p-dimethylaminobenzoate (EHDAB) in cosmetics. Chromato graphy is performed on preadsorbent chemically bonded C-18 reversed-ph ase silica gel plates with fluorescent indicator; quantitation is by s canning densitometry of fluorescence-quenched zones of samples and sta ndards. Three sunscreen cosmetics were analyzed to test the proposed m ethod and assess the relationship between EHDAB content and the SPF nu mber stated on the labels. The accuracy of the method was validated by performing recovery studies with fortified blank samples containing s imilar ingredients but no EHDAB. Precision was tested by analyzing rep licate samples. It was found that the amount of EHDAB in the tested pr oducts ranged from 2.07-3.99%. The relative standard deviation for det ermination of EHDAB varied from 2.49-6.96%, with an average of 4.56% ( n = 4). Average recoveries from fortified samples were 99.6 and 104% f rom lotion and tanning oil, respectively.