A method for the determination of N-nitrosoalkanolamines in cosmetics

A method für the determination of N-nitrosoalkanolamines in cosmetics and toiletries is described. The ingredients used in their manufacture N-nitroso-bis-(2-hydroxyethyl)amine (N-nitrosodiethanolamine, NDELA) and N-nitroso-bis-(2-hydroxy-propyl)amine (NBHPA) are almost exclusively the contaminants. The method has therefore been modified for their determination. N-Nitroso-(2-hydroxy-ethyl)-(2-hydroxypropyl)amine is used as the internal standard. After dilution with water, the cosmetic is adsorbed onto a kieselguhr column and extracted with n-butanol. The extract is brought to dryness, re-dissolved in chloroform/acetone (5 + 1) and transferred to a silica gel column. The column is washed and eluted with acetone. The eluate is dried and the residue is treated with N-methyl-N-trimethylsilyl-heptafluorobutyramide. Trimethylsilyl (TMS)derivatives of N-nitrosoalkanolamines are determined by gas-chromatography with a thermal energy analyzer (TEA). Recovery of the internal standard is 95% and the determination limit is 5 micrograms/kg, Repeated analyses of a foam bath, spiked with 30 micrograms/kg NDELA, gave an average content of 32 micrograms/kg NDELA (variation coefficient 8.8%; n = 10). In order to avoid artefact formation during the clean-up process, kieselguhr containing 50% sodium ascorbate has to be used when cosmetics containing free dialkanolamines are analyzed.