A bespoke reagent-free amperometric bromide sensor for seawater

Direct Electrochemical Analysis in Seawater: Evaluation of Chloride and Bromide Detection

“…As the insert shows, a first oxidation peak (Peak 1) was recorded at 0.59 V vs. MSE using the Pt electrode and 0.86 V vs. MSE using the GCE. Referring to the previous study [57], Peak 2 is attributed to the oxidation of chloride with the possible formation of hypochlorite/hypochlorous acid (HOCl/OCl − ), and Peak 1 is attributed to bromide oxidation with hypobromous acid (HOBr/OBr − ), which is among the possible products reported by Yu et al [77]. The Peak 2 corresponds to the reduction of the products from the chloride and bromide oxidation.…”

“…(1) However, there is necessarily a lack of accuracy, as it is an estimated value depending on salinity that primarily indicates the overall ion concentration rather than the chemical composition [7,35]. For bromide quantification, there are several techniques available, e.g., kinetic spectrophotometry [38][39][40][41][42][43][44][45], chromatography [46,47], capillary electrophoresis [48][49][50][51][52] and electrochemistry [53][54][55][56], but they have drawbacks from different perspectives, which have been discussed by Chen et al [57]. In brief, kinetic spectrophotometry may not be ideal for natural samples, as the oxidising agent could react with other ions present [38,43] and dilution of the sample is required [38].…”

“…Thus, amperometry is a technique that can avoid the drawbacks of potentiometry mentioned above [61][62][63][64][65], but traditionally has required analytes with a low concentration so that seawater cannot be directly used. Nevertheless, these problems have recently been solved by Guo et al [10] and Chen et al [57], with the first two bespoke regent-free amperometric sensors being proposed for chloride and bromide sensing, respectively, in authentic seawater.…”

“…There were two authentic seawaters used in this study, and the collection of these is described by Chen et al [57]. Ion chromatography analysis was conducted using a Dionex (Thermo Scientific, Sunnyvale, CA, USA) ICS-5000+ SP instrument, utilising a Dionex IonPac AS23-4um analytical column for the separations.…”

“…Next, cyclic voltammetry of ASW using a glassy carbon electrode (GCE) and a Pt electrode was investigated, building on an earlier report [57]. Cyclic voltammograms were first recorded with a scan rate of 100 mVs −1 using either the Pt electrode or the GCE in degassed ASW (see Figure 2a).…”