An environmentally friendly (“green”) reversed-phase liquid chromatography method for UV filters determination in cosmetics

A green procedure based on reversed-phase liquid chromatography with gradient elution using environmentally friendly solvents, has been developed to determine 18 UV filters, which are most used in Europe nowadays as sunscreen in cosmetics. Samples were weighed and dissolved in ethanol. Two aliquots were taken from the initial sample solution to prepare two solutions, so analytes could be determined chromatographically in two groups (the most fat-soluble and the easily water-soluble ones) using a different gradient elution program for each group. The mobile phases were based on mixtures of ethanol and 1% acetic acid or 1% sodium acetate buffer pH 4.75. The same C18 stationary phase column was employed in both cases. The chromatographic variables such as mobile phase composition, pH, flow rate and temperature were studied and selected in order to achieve total separation of all the peaks involved. The proposed method has been validated by the analysis of 27 commercial sunscreen samples (with different cosmetic forms: cream, lipstick, makeup, sun water, lotion, milk) and two synthetic samples. The method allows any mixture of the 18 UV filters studied to be separated with a good resolution and determined without interference from cosmetic matrices, moreover it does not require the use of highly toxic organic solvents.