Simultaneous enantioselective quantification of fluoxetine and norfluoxetine in human milk by direct sample injection using 2-dimensional liquid chromatography–tandem mass spectrometry

• Use of restricted access media column for depletion of milk proteins.
• A greener sample preparation approach for drugs in human milk.
• Achiral-chiral columns coupling for an enantioselective quantitative assay.
• Quantification of the enantiomers of FLX and its metabolites in human milk.

A two-dimensional liquid chromatography system coupled to triple quadrupole tandem mass spectrometer (2D LC–MS/MS) was employed for the simultaneously quantification of fluoxetine (FLX) and norfluoxetine (NFLX) enantiomers in human milk by direct injection of samples. A restricted access media of bovine serum albumin octadecyl column (RAM-BSA C18) was used in the first dimension for the milk proteins depletion, while an antibiotic-based chiral column was used in the second dimension. The results herein described show good selectivity, extraction efficiency, accuracy, and precision with limits of quantification in the order of 7.5 ng mL−1for the FLX enantiomers and 10.0 ng mL−1 for NFLX enantiomers. Furthermore, it represents a practical tool in terms of sustainability for the sample preparation of such a difficult matrix.