A new flow-injection chromatography method exploiting linear-gradient elution for fast quantitative screening of parabens in cosmetics

Abstract

This work describes a new flow injection chromatography (FIC) method based on linear-gradient elution for the determination of four parabens (methyl paraben (MP), ethyl paraben (EP), propyl paraben (PP) and butyl paraben (BP)) in cosmetics. Two-solvent linear gradients were generated by synchronous modulation of the flow rates of 2 MilliGAT computer-controlled pumps. Complex elution profiles could be created by combining isocratic with linear-gradient elution in a single run. Separation of the parabens was performed on a 5 mm monolithic C18 column with UV detection at 254 nm. It is demonstrated that the linear-gradient elution FIC approach offers distinct advantages over existing low-pressure isocratic and step-gradient elution protocols. Different operational parameters (the generation and linearity of the solvent gradient, the composition of the two solvents, the solvent gradient profile and steepness, and the flow rate of the mobile phase) were studied and discussed. The method was fully validated (in terms of linearity, limits of detection and quantification, accuracy and robustness) and proved to be fit-for-purpose, fast, reliable and robust. Its comparison with high performance liquid chromatography (HPLC) for the analysis of cosmetic products suggests that there was no statistical difference between the two methods.