Effect of tarnish on copper release

The rate of copper loss from bright and tarnished collars from Copper T Model TCu 380A IUDs has been investigated in amino acid solutions of pH 5.5 and 7.4 and in serum. In all three media, the tarnished collars quickly became bright and lost copper at the same rate as the initially bright collars. The single exception was when a high ratio of copper surface to serum was used. Under those conditions the tarnished collars initially became bright but after two days a black precipitate appeared on both the initially bright and tarnished collars and weight loss ceased. When a higher ratio of serum to copper surface was used, the pattern was one of continuing loss although at a lower rate than in the amino acid solutions. It is concluded that tarnish does not compromise the oxidation and dissolution of copper even in serum. Serum is considered a surrogate for uterine fluid.