[Photometric determination of Cu2+ ion using octabromo-tetrakis(4-methylpyridyl)porphine].

Octabromo-tetrakis(4-methylpyridyl)porphine (OBTMPyP), an octabromonated compound with 4 pyrole rings of tetrakis(4-methylpyridyl)porphine, selectively forms a complex with Cu2+ ions at pH 2.0. When 3.6×10(-5) mol/L OBTMPyP was added to the reaction mixture, the calibration curve showed good linearity for Cu2+ ions ranging from 0.01-2.2 µg (addition of 1.0 mL). A good coefficient of variation (Cu2+ ions=1.5 µg (addition of 1.0 mL), n=10, 0.8%) was obtained. The molar absorption coefficient (ε) based on Cu2+ ions was 8.5×10(4) L/mol•cm. This value was 6-fold greater than that determined with a clinical chemical analysis kit using the bathocuproine sulfonic acid method, which is a well-known method for spectrophotometric determination of the Cu2+ ion concentration. A deproteination method was successfully applied in the clinical analysis kit for determination of Cu2+ ion concentrations in control serum I, and the values determined using this method and the bathocuproine sulfonic acid method were almost the same.