A Novel Methodology for the Quantification of B-Vitamers in Breast Milk

With this report we present development, validation and application of an analytical methodology for the quantification of 18 water soluble vitamers and secreted or biological forms in breast milk. On a relatively low amount of breast milk (200 µL), we applied isotope dilution-based sample preparation based on a combination of enzymatic treatment and protein precipitation using acidic methanol enriched with stable isotope labelled internal standards. Compounds separation was achieved by reversed-phase liquid chromatography and detection performed by tandem mass spectrometry in positive electrospray ionization mode. To perform the quantification of 18 water soluble vitamers, procured pooled breast milk was used to build matrixmatched calibration curves, as labelled internal standards were not available for each vitamer. The analytical approach has been validated according to the EMA guidelines. The overall performance of the method was considered adequate, with 0.3- 28.3% and 0.9-32.6% intra and inter-day precision respectively and averaged accuracy reaching 92.2-107.5%. In addition, performed freeze/thaw stability studies showed the potential degradation of some vitamers. We therefore recommend particular attention in sample collection with rather having dedicated aliquots with small volumes. The feasibility of this analytical approach has been evaluated by quantifying various breast milk samples that were procured from an external supplier. The main forms found in breast milk were thiamine monophosphate for B1, flavin adenine nucleotide for B2, nicotinamide for B3, pyridoxal for B6 and 5-methyl tetrahydrofolic acid for B9. In addition, we newly reported nudifloramide as B3 form present in breast milk. With this analytical approach, it will give more confidence to provide a comprehensive assessment of the presence of water soluble vitamins in breast milk. This will enable the accurate evaluation of the nutritional requirements of infants.