LC-MS Identification of Phthalates of Neopentyl/Propylene Glycol and Quaternary Ammonium Cations in Nail Conditioners

Nail cosmetics, such as nail polish or nail conditioners, are considered as safe; however, their use may be accompanied with risks, e.g., related to contact of allergens with the periungual skin or to the transfer of a small amount of cosmetic to other areas of the skin. Therefore, the identification of potentially dangerous ingredients of nail cosmetics is of importance. In this work non-volatile organic compounds present in nail conditioners were analyzed by high-pressure liquid chromatography-mass spectrometry. Unexpectedly, in two samples the esters of phthalic acid with neopentyl glycol and mixed esters of phthalic acid with neopentyl glycol/propylene glycol were detected. Their structures were deduced on the basis of characteristic fragmentation pathways. It is reasonable to suppose that these compounds were formed by the reaction between the ingredients of the analyzed samples. The second group of the detected non-volatile organic compounds were quaternary ammonium salts, which are quite common in cosmetic products. These compounds were most probably transferred to the conditioners from the material from the inside of barrels in which the nail conditioners were stored. Although the presence of detected non-volatile organic compounds in nail conditioners is not particularly dangerous to human health, it is worth knowing that they can occur in the analyzed type of cosmetic products.