Electrochemical behavior and determination of quinolinium and isoquinolinium oximes

Abstract

The electrochemical behavior of 1‐(2‐phenyl‐2‐hydroxyiminoethyl)‐1‐quinolinium chloride (F‐1) and 1‐(2‐phenyl‐2‐hydroxyiminoethyl)‐1‐isoquinolinium chloride (F‐2) was investigated using dc and differential pulse polarography (DPP) and cyclic voltammetry. Well‐defined, diffusion‐controlled, cathodic waves were observed for F‐1 only in strong acidic solution (pH 1.25 HCl) and for F‐2 in the H range 1.25–5.33 (HCl and Britton–Robinson buffer). The overall reduction of the azomethine group to a primary amine, a process that involves the uptake of four electrons, is irreversible. For both oximes a mechanism of reduction has been proposed. The rapid and accurate determination of these quinolinium and isoquinolinium oximes is possible by dc polarography and by DPP. Limits of detection are 5 × 10−7 M for both oximes using DPP.