A Nafion Film Cover to Enhance the Analytical Performance of the CuO/Cu Electrochemical Sensor for Determination of Chemical Oxygen Demand

Abstract

We modified and evaluated the performance of a CuO/Cu electrochemical electrode for chemical oxygen demand (COD) determination by covering it with a Nafion (Nf) film. The resulting modified CuONf/Cu electrode sensor was used for the electrochemical determination of COD in river, slaughterhouse and estuarine water samples in order to evaluate its performance for this particular task. It was compared with the CuO/Cu sensor with no Nafion. The main electrochemical characteristics of interest, resistance, sensitivity, accuracy and reproducibility, were assessed by means of Linear Sweep Voltammetry using glucose as a standard. Results of these essays indicate that the procedure used produced smooth and firmly attached Nf films covering the whole copper surface. This sensor was shown to be resistant to interferences and effective in electro-oxidation of a wide range of organic compounds and therefore very useful for COD determination. Using the newly developed CuONf/Cu electrode an analytical linear range of 50 to 1000 mg·L−1 COD, with a detection limit of 2.11 mg·L−1 (n = 6) COD was achieved. The comparison shows that the CuONf/Cu sensor is more appropriate for COD determination than its counterpart with no Nafion.

A New Redox Mediator (Cupric‐Neocuproine Complex)‐ Modified Pencil Graphite Electrode for the Electrocatalytic Oxidation of H2O2: A Flow Injection Amperometric Sensor

“…Although the oxidation/reduction peaks increased with the increase of studied Nf concentration, peak potentials shifted to more positive direction. This shift to more positive potentials can be attributed to the increased amount of Nf on the electrode surface accompanying an increase in Nf concentration, which acts as an inert blocking layer hindering electron and mass transfer due to its highly insulating property . However, an immersion solution of 0.75 % Nf and an adsorption time of 10 min were chosen as optimum parameters for the modification of the CUPRAC reagent on Nf/PGE surface, because, as discussed later, the modified electrodes prepared under these conditions gave the best response to the flow injection (FI) amperometric detection of H 2 O 2 .…”

“…This shift to more positive potentials can be attributed to the increased amount of Nf on the electrode surface accompanying an increase in Nf concentration, which acts as an inert blocking layer hindering electron and mass transfer due to its highly insulating property. [48,57,58] However, an immersion solution of 0.75 % Nf and an adsorption time of 10 min were chosen as optimum parameters for the modification of the CUPRAC reagent on Nf/PGE surface, because, as discussed later, the modified electrodes prepared under these conditions gave the best response to the flow injection (FI) amperometric detection of H 2 O 2 . In the [Cu(Nc) 2 ] 2 + /Nf/PGE prepared by using 0.75 % Nf, oxidation/reduction peaks with mid-point potential (E 1/2 = (E a + E c )/2) of 440 mV vs. Ag/ AgCl/KCl (sat) were observed due to [Cu(Nc…”

Nano-Cu Modified Cu and Nano-Cu Modified Graphite Electrodes for Chemical Oxygen Demand Sensors

“…Copper electrode in alkaline media electrocatalytically oxidizes organic compounds mediated by surface of metal oxides. 22 Figure 3 shows a cyclic voltammetry of 0.075 M NaOH in a potential range of -1.0 to +0.8 V for nano-Cu/Cu prepared by cyclic voltammetry. A typical peak response was also observed at nano-Cu/C electrode (data not shown).…”

“…Cu was selected as the based electrode as it powerfully oxidizes carbohydrates and amino acids, known as a culprit for COD. 22 On the other hand, graphite is cheap, simple, and a well-known carbon electrode. 23 The characteristic of the electrochemical sensors was assessed using standard reagents of glycine and glucose to evaluate COD value.…”

A Self-Supported CuO/Cu Nanowire Electrode as Highly Efficient Sensor for COD Measurement

“…In order to fulfill the direct detection of COD, many materials have been tested as electrocatalysts, including CoO [6], Cu [7,8,9,10,11], Ni-Cu [12], TiO 2 [13,14], PbO 2 [15], nano-Pt [16], CuO/AgO [17], Cu-Co [18], nickel nanoparticle/nafion-graphene oxide (GO) [19], boron doped diamond(BDD) [20,21], Ti/Sb–SnO 2 /PbO 2 [22], and carbon fiber felt/CeO 2 -β-PbO 2 [23]. Among them, Cu-base materials have been recognized as promising electrocatalysts for determination of COD in water samples due to their strong ability to electro-oxidize organic compounds [24] and have drawn increasing attention in the past [7,8,9,10,11,12]. For example, Silva et al used a Cu rod electrode as the sensor and found that it exhibited a wide COD linear range (53.0–2801.4 mg/L) but a high detection limit (20.3 mg/L) despite having a good ability to produce active species CuO(OH) [7].…”