Polarographic determination of phenylalanine,tyrosine, methionine,glutamic acid and histidine with a dropping copper amalgam electrode

The anions of the phenylalanine, tyrosine, methionine and glutamic acid give an anodic wave when a dropping copper amalgam electrode is oxidized in their presence, approximately at the same half-wave potential of that of the glycine anion (?0.28 V vs. SCE). The height of these waves depends on pH and amino acid concentration and can be utilized for the polarographic determination of these substances using the same procedure as that described previously for the determination of glycine. The polarographic behaviour of histidine is somewhat different because the zwitterion of this amino acid reacts with the Cu²⁺ and the anion forms a more stable complex. The polarographic determination of histidine can be also carried out with the same procedure.