The interaction of Methylthymol Blue(MTB)-Zinc! compound and Alizarin Red S(ARS)-Aluminum" compound with Bovine serum albumin (BSA) was investigated by UV-Vis spectrophotometric method in acidic buffer solution. MTB-Zn!-BSA was a blue color compound, which possesses maximum absorption at 613 nm with 172 nm, 174 nm and 18 nm of red shift compared to the MTB, MTB-BSA and MTB-Zn! complexes respectively. Dual wavelength substantial amount ratio method, balance dialysis substantial amount ratio method and unity wavelength substantial amount ratio method were compared. The following results were obtained: the apparent molar absorptivity of MTB-Zn! with BSA was ε=2.20×104 L·mol-1·cm-1. Conditional proportion were defined, nMTB∶nZn!∶nBSA=2∶2∶1; condition combination constant, K=2.07×1010. Combination proportion were defined, nARS∶nAl"∶ nBSA=6∶4∶1. Condition equilibrium constant of reaction of ARS-Al" with BSA was K=8.80×108. The apparent mo- lar absorptivity of ε=2.65×104 L·mol-·1cm-1. It is suggested that combination between BSA and MTB-Zn" is due to coordination force. That combination between BSA and ARS-Al" is due to the coordination bond and electro- static force.
