Selenium speciation in human milk with special respect to quality control

Area of Science:

• Biochemistry
• Analytical Chemistry
• Human Nutrition

Background:

• Human milk is a vital source of nutrients, including essential trace elements like selenium.
• Understanding the chemical forms (species) of selenium in human milk is crucial for assessing its bioavailability and biological activity.
• Previous research has indicated the presence of organoselenium compounds, but detailed speciation remains challenging.

Purpose of the Study:

• To identify and quantify specific selenium (Se) organo compounds in pooled human milk.
• To confirm the stability of these Se species during analytical procedures.
• To provide accurate measurements of Se-ligand associations in human milk.

Main Methods:

• Separation of Se organo compounds using centrifugation and size-exclusion chromatography (SEC).
• Quantification of Se by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS).
• Identification of organic ligands using capillary zone electrophoresis (CZE) and isotachophoresis-capillary zone electrophoresis (ITP-CZE).

Main Results:

• Native Se species were confirmed in human milk, with no transformations during analysis.
• Quantification of organic ligands revealed concentrations for GSH/GSeH, cystamine/Se-cystamine, cystine/Se-cystine, and methionine/Se-methionine.
• Specific Se values associated with each ligand were determined, including GSeH (2.5 mg/L), Se-cystamine (3.1 mg/L), Se-cystine (5.2 mg/L), and Se-methionine (1 mg/L).

Conclusions:

• The study successfully identified and quantified key selenium organo compounds in human milk.
• The analytical methods employed ensured the integrity of the native Se species.
• These findings contribute to a better understanding of selenium metabolism and nutritional importance in human milk.