Determination of the major zinc fractions in human serum by ultrafiltration

In this paper we report a method for measuring ultrafiltrable zinc in human serum by electrothermal atomic absorption spectrophtometry. We show also that ultrafiltration permits to determine alpha-2 macroglobulin bound zinc and losely bound zinc if a strong zinc ligand (EDTA) is added to serum before ultrafiltration. This last fraction, after deduction of ultrafiltrable zinc, represents roughly all albumin bound zinc. In 20 controls we found that ultrafiltrable zinc amounted 0.311 μmol/L (S.D.=0.117 μmol/L), alpha-2 macroglobulin bound zinc 3.08 μmol/L (S.D.=0.221 μmol/L), and albumin bound zinc 12.11 μmol/L (S.D.=1.95 μmol/L). Our method needs only a small volume of serum, it is simple and rapid but also very accurate and reliable. The losely bound fraction is very dynamic and, representing the physiologically active part of serum zinc, it could be a good marker of zinc deficiency.