The Application of a Metallic Copper Electrode to Potentiometric Detection of Reducing Species in Ion Chromatography

The use of a metallic copper electrode for potentiometric detection of reducing species such as ascorbic acid, hydrazine and hydroxylamine is reported. Detection of these species is based on the increase in electrode potential resulting from reduction of cupric ions to cuprous ions at the electrode surface, with the potential increase occurring because of the higher standard potential of Cu+/Cu0 in comparison to that of Cu2+/Cu0. Ascorbic acid and its oxidation product, dehydroascorbic acid, may be determined using a Vydac 302 IC anion-exchange column with 20 mM sodium tartrate at pH 6.2 as eluent, whereas hydrazine and hydroxylamine may be determined using a Nucleosil 10SA cation-exchange column with 2 mM citrate and 2 mM ethylenediamine at pH 4.5 as eluent. Calibration plots showed a linear relationship between electrode potential and low concentrations of injected species, while at higher concentrations, a logarithmic relationship was followed. Detection limits were in the range 2–10 nmol for the species examined.