Molecularly imprinted nanoparticles grafted to porous silica as chiral selectors in liquid chromatography.

•Imprinted nanoparticles are presented as efficient chiral selectors.•Nanoparticles were covalently immobilised on porous silica supports.•Both precipitation polymerisation and solid-phase synthesis were explored.•The developed stationary phase successfully resolved the racemate of citalopram.•S-citalopram and its major metabolites were separated and quantified in urine.