Polarographic Investigations of Reactions in Aqueous Solutions Containing Copper and Cysteine (Cystine). Amperometric Titration of Traces of Cysteine and Cystine with Cupric Copper as Reagent

Abstract

From a polarographic study of the reaction between cupric copper and cysteine in ammoniacal medium in the presence of sulfite, it was inferred that this reaction could be made the basis of a rapid amperometric titration of traces of cysteine and cystine, using the rotating platinum electrode as the indicator electrode. Procedures are given for the rapid and accurate determination of traces of cysteine and cystine at concentrations between 4 × 10−4 and 10−5 M. Cadmium, zinc, and iodide do not interfere. Cobalt interferes. An accurate and rapid determination of traces of cysteine and cystine is of great significance in the investigation of biological materials like normal and pathological blood sera. The new method is more specific and precise than methods that have been previously used. © 1951, American Chemical Society. All rights reserved.