A coated wire electrode (CWE) for nitrate was constructed by the use of polyvinyl chloride (PVC) or epoxy resin as a polymer membrane. The CWE consists of a copper wire and the polymer matrix incorporating a liquid ion exchanger which coated on the whole surface of the wire. The characteristics of the CWE were dependent on the thickness of the polymer membrane and polymer matrix composition. The appropriate thickness of the membrane was about (0.05 ~ 0.2) mm. The most appropriate mixing ratios of the polymer to ion exchanger in the membrane were 1/1 and 2/1 for the CWE using PVC (PVC-CWE) and CWE using epoxy resin (Epoxy-CWE), respectively. The responses were Nernstian for both CWEs with this thickness in these compositions. The CWEs respond in a few seconds with the stability of within ± 2.0 mV. The reproducibility and durability for the Epoxy-CWE were good and the linear response limit was 2 × 10-5 M nitrate, whereas the durability of the PVC-CWE was poor and the limit was at most 1 × 10-4 M. In addition, the selectivity of the Epoxy-CWE was improved for the anions such as I- or ClO-4 which causes large interference in a usual barrel type of liquid membrane electrode.
ASJC Scopus subject areas