Voltammetric determination of arginine using the catalytic nickel reduction

Arginine is an amino acid that plays a significent role in cell division, healing of wounds, removing ammonia from the body, improving immunity to illness, and hormone secretion. Arginine is used by the body to generate nitric oxide, a substance that relaxes blood vessels. For this reason, it has been used to treat cardiovascular disorders such as heart failure, intermittent claudication, impotence, female sexual dysfunction, and interstitial cystitis. Arginine belongs to traditionally “non-electroactive” amino acids, although direct determination of amino acids by voltammetric techniques performed with metallic electrodes such as Cu and Au is possible. We demonstrate here that arginine can be amenable to electrochemical detection by letting it to act as a catalyst in Ni(II) reduction reaction, in a slightly alkaline solution (0.02 M borax, pH 8.5) using mercury electrode. Under these conditions, the catalytic reduction of Ni(II) at a HMDE occurs according to the general mechanism and results in a voltammetric peak at about -0.85 V vs.Ag|AgCl, KCl (3.4 M).The peak current depends on pH, nature of the buffer. The DPV signal is proportional to arginine concentration within the concentration range from 0.1 to 10 M. The repeatability, precision and accuracy of the method were checked. The effect of other aminoacids (glycine, lysine, ornithine, cystine) and the surfactans which can be components of arginine pharmaceutical dosage forms on the peak current was also studied. According to the linear current-concentration relation, the developed DPV method was used for quantitative determination of arginine in tablets. The results were in a fair agreement with HPLC method.