Rapid and highly sensitive determination of trace proteins using dibromomethyl carboxyazo-Pb(II) complex as a spectroscopic reagent.

Background: The concentration of protein in body fluids is an important measure in disease diagnosis and in analytical biochemistry. Searching for a sensitive and rapid method for proteins is an ongoing subject of investigation. We describe the reaction of dibromomethyl carboxyazo-Pb(II) with proteins found in urine.

Methods: In a buffer containing of HCl and KCl at pH 1.80, dibromomethyl carboxyazo-Pb(II) complex combined with proteins to form a colored compound. The reaction was completed in 2 min and remained stable for 80 min. Under optimum conditions, the product of reaction between protein and dibromomethyl carboxyazo-Pb(II) absorbed at 530 nm and was linear in the range of 0-50 microg/ml of BSA. Moreover, the maximum binding number was defined to express the binding ability of dibromomethyl carboxyazo-Pb(II) to protein under a given set of conditions.

Results: The method was applied to the determination of urine proteins. The recovery of protein from human urine was 97.6-103% and the precision was <4.8%. Results compared favorably to the Biuret and Bradford protein methods on 50 urine samples.

Conclusions: This method had high sensitivity and specificity and may be applicable to clinical analysis.