Selenium speciation in human milk with special respect to quality control |
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Authors: | Bernhard Michalke P Schramel |
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Institution: | (1) GSF Research Centre for Environment and Health GmbH, 85758 Neuherberg, Oberschlei\heim, Germany |
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Abstract: | Selenium-(SE) organo compounds of pooled human milk (7th-14th d after delivery) were separated by centrifugation and subsequent
size-exclusion chromatography (SEC) as described in ref. (1). The SEC fractions were used for Se determinations by electrothermal vaporization inductively coupled plasma mass spectrometry
(ETV-ICP-MS) in parallel to identification procedures of the organic ligands by two different capillary zone electrophoresis
(CZE) methods. Further, the combination of isotachophoresis-(ITP) CZE with ETV-ICP-MS was used for final identifications.
Mass balances were carried out at each analytical step for quality assurance. Reinjection experiments were performed to check
the stability of Se-organo compounds during the analytical procedure. These quality-control experiments showed that no species
transformations took place during the analytical procedure, and the Se species were native in human milk. The identification
and quantification of organic ligands were clear and resulted in values of 2 (±0.2) mg/L GSH/GSeH, 2 (±0.22) mg/L cystamine/Se-cystamine,
4 (±0.4) mg/L cystine/ Se-cystine, and 1 (±0.18) mg/L methionine/Se-methionine.
Unfortunately, a differentiation between sulfur (S) and Se analogs was not possible with the applied CE methods.
The Se values per organic ligand were determined as 2.5 (±0.23) mg/L associated with GSH (as GSeH), 3.1 (±0.31) mg/L associated
with cystamine (as Se-cystamine), 5.2 (±0.4) mg/L associated with cystine (as Se-cystine), and 1 (±0.1) mg/L associated with
methionine (as Se-methionine). |
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