Monitoring of N-nitrosodiethanolamine in cosmetic products by ion-pair complex liquid chromatography and identification with negative ion electrospray ionization mass spectrometry

A high-performance liquid chromatographic (HPLC) method was developed for the determination of N-nitrosodiethanolamine (NDELA), which is a non-volatile N-nitrosoamine. In this method, sodium 1-octanesulfonate has been used as an ion complexation agent for NDELA. The resulting complex was analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) using a Eurospher-100 C18 column (250 × 4.6 mm, 5 μm), water/acetonitrile (95/5, v/v) and UV detection at 234 nm. The detector response was linear in the range 0.03–10.00 μg mL−1 and the limit of detection was 0.01 μg mL−1. The complexation of the NDELA and sodium 1-octanesulfonate was confirmed by negative ion electrospray ionization mass spectrometry at m/z 327 [M–Na]− and also MS/MS measurements of the resulting fragments. For real sample analyses, NDELA was measured in cosmetic products after clean up by solid-phase extraction (SPE) with C18 cartridge for water-soluble samples and liquid–liquid extraction (LLE) by methylene chloride for less water-soluble samples. The average values for NDELA recovery by SPE and LLE were 86.9 and 51.8% and relative standard deviations (RSDs%) were 0.9 and 5.6%, respectively. The presented method is easy to use, robust and can be implemented on any reversed-phase HPLC system with UV detection.