A molecularly imprinted polymer for microdisc solid-phase extraction of parabens from human milk samples

Abstract

A new molecularly imprinted sol–gel polymer (MIP) was developed for microdisc solid phase extraction of parabens from human milk samples, followed by liquid chromatography analysis with a photometric detector (MISPE/LC-UV). The molecularly imprinted ormosil was synthesized by the sol–gel method using benzylparaben as a template. After template removal, selective cavities (benzylparaben) were revealed for parabens' extraction. The process of molecular recognition was based on the intermolecular interactions (hydrogen bonds) between the parabens and functional groups present in the MIP selective cavities. Fourier Transform-Infrared Spectroscopy (FTIR) spectra of the MIP and non-imprinted polymer (NIP) displayed feature bands of the 3-aminopropyltrimethoxysilane (APTMS) bonds. The use of Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) attested to the presence of covalent Si–O–Si–R bonds in the structure of MIPs and NIPs. The effects of the microdisc SPE variables (pH of the sample, washing step, nature and volume of the elution solvent) on MISPE performance were evaluated. The linear range of the MISPE/LC-UV method ranges from the LOQ values (10–20 ng mL⁻¹) to 150 ng mL⁻¹, with a correlation coefficient higher than 0.992. The interday precision of the MISPE/LC-UV method presented a coefficient of variation lower than 13%; the accuracy ranged from 86 to 117%. According to the evaluated analytical validation parameters, the MISPE/LC-UV method is suitable for the analysis of parabens in human milk samples. Analysis of the milk samples from lactating women demonstrated the effectiveness of the proposed method.