New 2D-LC–MS Method Detects Multiclass Prohibited Substances in Cosmetics

A new two-dimensional liquid chromatography-mass spectrometry (2D-LC–MS) method has been developed for detecting multiclass prohibited substances in cosmetics, according to a recent study. The method combines hydrophilic interaction LC (HILIC) and reversed-phase LC (RPLC) techniques and uses an online diluting modulation to achieve an excellent column-head focusing effect and reduce sensitivity loss.

The first dimension HILIC separates the polar and hydrophilic compounds. The compounds near the dead time are transferred to the second dimension RPLC for further separation. The diluting modulation solved the problem of mobile phase incompatibility, and it did not restrict the flow rate of the second-dimension analysis.

The researchers demonstrated the 2D-LC–MS system by determining 126 prohibited substances in cosmetic products, including hormones, local anesthetics, anti-infectives, adrenergic agents, antihistamines, pesticides, and other chemicals. All correlation coefficients of the compounds were above 0.9950, with the limit of detection (LOD) ranging from 0.000259 ng/mL to 16.6 ng/mL, and the limit of quantification (LOQ) ranging from 0.000864 ng/mL to 55.3 ng/mL. The intra-day and inter-day precision RSD% was within 6% and 14%, respectively.

Compared with conventional one-dimensional LC (1D-LC) methods, the 2D-LC–MS method expanded the analytical coverage of cosmetics-prohibited substances with reduced matrix effects for most compounds and improved sensitivity for polar analytes. The method is a powerful tool for screening multiclass prohibited substances in cosmetics, ensuring the quality and safety of cosmetics used in everyday life.

Reference

(1) Zhang, L.; Shen, L.; Zhong, Q.; Zhou, T. Diluting modulation-based two dimensional-liquid chromatography coupled with mass spectrometry for simultaneously determining multiclass prohibited substances in cosmetics. J. Chromatogr. A. 2023, 1695, 463954. DOI: 10.1016/j.chroma.2023.463954