Resonance light-scattering spectroscopic determination of protein with pyrocatechol violet

Abstract At pH 1.4–2.0 and in the presence of Triton X-100 the resonance light-scattering (RLS) spectrum of pyrocatechol violet (PV) has a maximum peak at 341 nm with two wide bands centering on 399 and 468 nm, respectively. If micro protein coexists in the system, the RLS intensities of PV at 399 and 468 nm are significantly increased by protein due to the binding interaction between protein and PV. Based on this, a new assay for protein is proposed. The calibration graphs for bovine and human serum albumin are linear up to 8.0 and 9.0 mg l −1 with 3 σ detection limits of 5.2 and 6.9×10 −5  mg l −1 , respectively. The method is characterized by high sensitivity, short reaction period, simplicity and good stability of the chemical system. Results for human serum, urine and saliva are in agreement with those obtained by the Bradford method with relative standard deviations of 1.5–2.3% ( n =5).