Study on the Indirect Electrochemical Detection of Ammonium Ion with In Situ Electrogenerated Hypobromous Acid

Abstract

The mechanism on the electrochemical oxidation of bromide in the presence of ammonium ion was studied by cyclic voltammetry and in-situ UV-Vis spectroscopy. The results indicated that the anodically generated bromine (Br 2 ) would be hydrolyzed to hypobromous acid (HBrO) at the pH range of 5 -7 and was further disproportionate to hypobromite anion (BrO -) when pH was large than 7. Both HBrO and BrO -were confirmed to be participated in the following homogeneous chemical reaction with the ammonium ion co-existed in the electrolytic solution. However, HBrO is electroactive whereas BrO -is electroinactive at carbon electrode. Based upon the reaction of HBrO with ammonium ion, an indirect electrochemical method was proposed for determination of ammonium ion at pH 7 with dual-electrode configuration, where HBrO was produced at a generator electrode and the excess HBrO was subsequently detected at a collector electrode after a reaction with ammonium ion. It was demonstrated that ammonium ion concentrations were proportional to the decreasing of reduction current at the collector electrode either in a batch solution or in a micro flow injection analytical (micro-FIA) system using an interdigitated array (IDA) Pt microelectrode and a carbon film ring-disk electrode (CFRDE), with the detection limit below 3 Μ. This approach shows the advantage of highly selectivity even in presence of a large amount of co-existed cations.

Pulse-Voltammetric Glucose Detection at Gold Junction Electrodes

“…Traditional pulse voltammetric methods can be applied for the modulator or for the sensor electrode, and in the future, new types of customized pulse sequences will be desirable for the junction sensor electrode. The determination of glucose has been selected here to highlight the potential and importance of this experimental tool and further applications will include, for example, determining organohalides, ammonia, buffer capacity, or p K A values in aqueous media. The miniaturization of junction sensors and the optimization of the interelectrode gap will be of considerable practical importance in electroanalysis.…”

Electrochemical monitoring of marine nutrients: From principle to application

“…Although almost no electrochemical oxidation of ammonium occurs at a high positive potential, it can be achieved via indirect measurements. Takahashi et al [99] proposed an indirect electrochemical method for determining ammonia nitrogen concentrations. The detection principle of this method is that bromine (Br 2 ) is generated by the anode, which can be hydrolyzed into hypobromic acid (HBrO) in the phosphoric acid buffer solution at pH 7.…”

Rapid Opto-electrochemical Differentiation of Marine Phytoplankton

“…At this potential, thermodynamically, 23 a wide range of oxidants can be formed concomitantly in seawater at the carbon wire electrode. This includes, for example, the oxidation of chloride to dichlorine, 24 bromide to hypobromous acid, 25 and water to hydrogen peroxide or hydroxide radicals and protons. 26 The reaction of the oxidants with the phytoplankton results in a sharp drop in the chl-a fluorescence signal after a delay in the onset of the applied potential due to the finite time required for the oxidants to diffuse over tens to hundreds of microns in distance and to penetrate the membranes to reach the chlorophyll in the cell.…”