Screening, characterization, and determination of suspected additives bimatoprost and latanoprost in cosmetics using NMR and LC-MS methods

Recently, many new types of cosmetic illegal additives have been screened in the market. Most of the new additives were new drugs or analogues with very similar structures to other prohibited additives, which were difficult to be identified by liquid chromatography-mass spectrometry (LC-MS) only. Therefore, a new strategy is proposed, which is chromatographic separation combined with nuclear magnetic resonance spectroscopy (NMR) structural identification. The suspected samples were screened by ultra-high-performance liquid chromatography tandem high-resolution mass spectrometry (UPLC-Q-TOF-MS), followed by purification and extraction through silica-gel column chromatography and preparative high-performance liquid chromatography (HPLC). Finally, the extracts were identified unambiguously by NMR as bimatoprost and latanoprost, which were identified to be new cosmetic illegal additives in eyelash serums in China. Meanwhile, bimatoprost and latanoprost were quantified by high-performance liquid chromatography tandem triple quadrupole mass spectrum (HPLC-QQQ-MS/MS). The quantitative method demonstrated good linearity in the range of approximately 0.25-50 ng/mL (R-2 > 0.9992), with limit of detection (LOD) and limit of quantification (LOQ) values of 0.01 and 0.03 mg/kg, respectively. The accuracy, precision, and reproducibility were confirmed to be acceptable.

Automated summary

Recently, new types of illegal cosmetic additives have emerged in the market. These additives are often new drugs or analogues with similar structures to prohibited additives, making them difficult to identify solely by LC-MS. To address this, a new strategy combining chromatographic separation with NMR structural identification is proposed. Suspected samples were screened using UPLC-Q-TOF-MS, followed by purification and extraction through silica-gel column chromatography and preparative HPLC. The extracts were then identified using NMR as bimatoprost and latanoprost, which were found to be new illegal additives in eyelash serums in China. Furthermore, bimatoprost and latanoprost were quantified using HPLC-QQQ-MS/MS, demonstrating good linearity, accuracy, precision, and reproducibility.