A colorimetric method for the determination of copper in serum that uses bicinchoninic acid was optimised and validated. The reaction is linear,at least up to 300 µg/dL of copper; the lower limit of detection was 8 µg/dL. The average recovery was 99,7 percent. Bilirrubin, iron, calcium, magnesium and zinc do not interfere. Within-run precision (CV) was 2,6, 1,8 and 1,2 percent; and day to day precision was 4,8, 3,0 and 1,5 percent for samples with low, normal and high values of serum copper, respectively. The method highly correlates with the determination of copper with the dibenzyldithiocarbamate method. The copper/caeruloplasmin ratio in patients with Wilson's disease and normal people was also compared. In patients with Wilson's disease a ratio 2,0 was observed, while in heterozygotes and people that don't suffer this iliness this ratio was near 1,0. This ratio could be used as an index of the copper not bound to caeruloplasmin.

copper serum; caeruloplasmin; Wilson's disease; bicinchoninic acid