Total zinc quantification by inductively coupled plasma-mass spectrometry and its speciation by size exclusion chromatography–inductively coupled plasma-mass spectrometry in human milk and commercial formulas: Importance in infant nutrition

•Zinc content showed a significant decreasing from colostrum to mature breast milk.•Zn content in commercial formulas was over the minimum recommended level.•Zinc is associated mainly to immunoglobulins (IgA, IgG in human milk) and citrate.•Development of zinc-fortified formulas with different speciation is recommended.