Study of the catalytic polarographic reduction of Ni(II) in the presence of albumin, immunoglobulins and serum proteins Determination of total proteins in serum

A study on the catalytic reduction of nickel(II) ion in the presence of albumin, immunoglobulins and serum proteins in sodium acetate medium has been carried out using differential-pulse polarography. The catalytic reduction of nickel ion gives two peaks at −0.60 V and −0.78 V versus a saturated calomel reference electrode. The adsorption of proteins on the electrode surface and the formation of Ni(II)-protein complexes, which greatly reduces the high overvoltage for the polarographic reduction of nickel(II), is shown. The peak obtained at −0.60 V is sufficiently well-defined and can be exploited for analytical purposes. The electrochemical variables affecting the polarographic behavior of nickel(II) in the presence of proteins were investigated; the prepeak obtained at −0.60 V using 10−2 M Ni(II) in 1 M sodium acetate, at pH 8.3, permits the quantitative determination of proteins in the following ranges: 3–75 μg/ml of albumin, 6–175 μg/ml of immunoglobulins and 2–5 μg/ml total serum proteins. Application of the proposed method for rapid and direct determination of total proteins in human serum samples is demonstrated; the results agree with those obtained with the established biuret automated method.