Vitamin B12 quantification in human milk – Beyond current limitations using liquid chromatography and inductively coupled plasma – Mass spectrometry

•New method for vitamin B12 quantification in human milk based on cobalt detection.•Method validation demonstrates its reliability at levels as low as 40 pmol/L.•No difference is seenbetween microbiological assay and the newly developed method.•Method can be used to determine vitamin B12 in population observational studies.