Speciation of Zinc in Low Molecular Weight Proteins of Breast Milk and Infant Formulas by Size Exclusion Chromatography/Flame Atomic Absorption Spectroscopy
Abstract:Size exclusion chromatography (SEC) and flame atomic absorption spectroscopy (FAAS) were used for the separation of metal-containing species in milk whey. After milk ultracentrifugation, the sample was injected into a TSK-Gel G2000 glass column and eluted with 0.2M NH4NO3–NH3, pH 6.7. Low molecular weight proteins were fractionated, and the fractions were characterized by molecular weight. Zinc distributions were obtained by FAAS using a high performance nebulizer. The method was very sensitive (limit of detection = 2.6 × 10−3 μg/mL; limit of quantitation = 8.9 × 10−3 μg/mL) and precise (RSDs ≤ 10%). This method was applied to the determination of Zn in binding compounds in breast milk whey and in commercial cow's milk-based formulas. Distribution patterns were different. The presence of Zn in most fractions in breast milk was most significant, whereas in infant formulas Zn was detected only in fractions of molecular weight <5 kDa and in the highest molecular weight peak.
Document Type: Research Article
Affiliations: 1: University of Santiago de Compostela, Faculty of Chemistry, Department of Analytical Chemistry, Nutrition and Bromatology, 15782, Santiago de Compostela, Avenida de las Ciencias, Spain. 2: Hospital Clínico Universitario, Laboratory of Metabolic Disorders, Santiago de Compostela, Avda, Spain. 3: University of Santiago de Compostela, Faculty of Medicine, Department of Pediatrics, Avenida de las Ciencias, Spain.
Publication date: May 1, 2001
- The Journal of AOAC INTERNATIONAL publishes refereed papers and reviews in the fields of chemical, biological and toxicological analytical chemistry for the purpose of showcasing the most precise, accurate and sensitive methods for analysis of foods, food additives, supplements and contaminants, cosmetics, drugs, toxins, hazardous substances, pesticides, feeds, fertilizers and the environment available at that point in time. The scope of the Journal includes unpublished original research describing new analytical methods, techniques and applications; improved approaches to sampling, both in the field and the laboratory; better methods of preparing samples for analysis; collaborative studies substantiating the performance of a given method; statistical techniques for evaluating data. The Journal will also publish other articles of general interest to its audience, e.g., technical communications; cautionary notes; comments on techniques, apparatus, and reagents.
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