Rapid and Automated Analytical Methods for Redox Species Based on Potentiometric Flow Injection Analysis Using Potential Buffers

Hiroki Ohura,Toshihiko Imato

doi:10.1155/2011/516165

Abstract

Two analytical methods, which prove the utility of a potentiometric flow injection technique for determining various redox species, based on the use of some redox potential buffers, are reviewed. The first is a potentiometric flow injection method in which a redox couple such as Fe(III)-Fe(II), Fe(CN)6 3−-Fe(CN)(CN)6 4−, and bromide-bromine and a redox electrode or a combined platinum-bromide ion selective electrode are used. The analytical principle and advantages of the method are discussed, and several examples of its application are reported. Another example is a highly sensitive potentiometric flow injection method, in which a large transient potential change due to bromine or chlorine as an intermediate, generated during the reaction of the oxidative species with an Fe(III)-Fe(II) potential buffer containing bromide or chloride, is utilized. The analytical principle and details of the proposed method are described, and examples of several applications are described. The determination of trace amounts of hydrazine, based on the detection of a transient change in potential caused by the reaction with a Ce(IV)-Ce(III) potential buffer, is also described.

Highlights

Titrimetric analysis, the characteristics of which include a high precision and the measurement of an absolute quantity, is in widespread use in the chemical industry and the pharmaceutical industry [1, 2], and a wide variety of applications have been developed
During our research on the use of potentiometric flow injection analysis (FIA) for the determination of redox species using a potential buffer, as described above, we discovered an interesting phenomena in which a large transient potential change in the redox electrode with a mountainshape appeared, when a bromate solution was added to an Fe(III)-Fe(II) potential buffer containing bromide [16]
The method is subject to the nature of the redox species under consideration in an analyte sample

Summary

Introduction

Titrimetric analysis, the characteristics of which include a high precision and the measurement of an absolute quantity, is in widespread use in the chemical industry and the pharmaceutical industry [1, 2], and a wide variety of applications have been developed. Karlberg and Thelander [15] reported the determination of Fe(II) and ascorbic acid by monitoring the composition of Ce(IV)-Ce(III) formed by a reaction with a stream of a cerium(IV) reagent with redox detection These potentiometric detection methods can be performed with only the use of an oxidant without a reductant as the stream of reagent solution in a flow system. We describe a highly sensitive potentiometric FIA method based on the detection of a large transient potential change in the redox electrode, which appears a short period after an analyte is mixed with the potential buffer. A high sensitivity to such oxidative species was achieved by the potentiometric detection of a large transient potential change due to the generation of intermediate bromine or chlorine during the reaction of the analyte with bromide or chloride in the potential buffer. The analytical methodology and mechanism for the potential change of the two proposed methods indicate that, in both cases, an equilibrium potential reached after a simple redox reaction and a transient potential generated during a complexed redox reaction could be measured

Experimental

Findings

Conclusion