Indirect Voltammetric Method for the Determination of Amino Acids Via Charge Transfer Complex Formation Reaction

Abstract

An easy and sensitive indirect voltammetric method has been proposed for the determination of trace amounts of amino acids, such as proline, glycine, arginine, phenylalanine, glutamic acid, and cysteine, in the range of 50–330 ngmL^-1 in aqueous solution. It is based on the reaction of chloranil as a π-acceptor with the intended amino acids acting as n-donors, forming an n–π charge transfer complex at pH 9. The reduction peak of (pH 9 – chloranil) solution appears at 0.030 V against the Ag/AgCl. reference electrode. When an aqueous solution of amino acids is added, the peak of solution (pH 9 – chloranil) decreases quantitatively and shifts slightly to 0.024 V. The concentration of amino acids is determined as the current difference decreases. The molar absorptivity ranges between 4.73 ×10³ l/mol.cm and 1.82 ×10⁴ l/mol.cm. The accuracy, i.e. average recovery ranges from 98.64% to 101.19%, and the precision, i.e. relative standard deviation (RSD) is between 0.5% and 9.6%. The limit of detection (LOD) ranges from 1.09×10^-7 µg/ml to 3.53×10^-7 µg/mL.