Zinc in plasma and serum: influence of contamination due to the collection tubes.

The contamination caused by rubber stoppers of collection tubes preceding the determination of zinc in plasma and serum was investigated. The use of evacuated blood collection tubes (EBC-tubes), normally used for the collection of serum samples, could give rise to an average artificial increase of normal serum zinc concentrations of about 250%. Heparin containing EBC-tubes, used for the collection of plasma, and plain EBC-tubes of an experimental production appeared to be suitable for correct zinc determinations. There was no difference between the serum and plasma zinc levels of fifty volunteers.