Spectrophotometric Determination of Protein Using Arsenazo M

In a pH 2.5 buffer solution containing 0.050% OP, protein forms a blue complex with arsenazo M. Its maximum absorption peak is 605 nm with molar absorptivity of 4.5×10 5 L·mol -1 ·cm -1 . Beer's law is obeyed in a range from 3.3 mg/L to 254 mg/L. The proposed method has been applied to the determination of protein in serum and peanut samples.