Electrochemical Detection of Ornidazole By Means of an Electrode Modified with Copper-Iron Nanoparticles and Carbon Black
Authors: Glennon Luke Daniel , Breslin Carmel B 
Published: August 2024

Antibiotics have become fundamental tools in our fight against disease but their accumulation in the aquatic environment due to discharges from manufacturing plants, hospitals and farms, and to misuse by the public has seen them emerge as water pollutants. Their presence constitutes a serious environmental and health risk due to their toxicity and due to the risk of antimicrobial resistance (AMR), which may render antibiotics ineffective when employed to fight infection. Assessing the impact of antibiotic pollution on water quality, drinking water, recreational/bathing water, and the impact on life is critical for our health and wellbeing.
Ornidazole is a member of the nitroimidazole antibiotic family that is heavily employed in the treatment of both human and animal infections [1]. This widespread use has led to the accumulation of the antibiotic in aquatic environments, posing a serious health risk due to its toxicity and the risk of AMR [2]. For this reason, novel and environmentally friendly methods of rapidly and accurately detecting its presence in the environment are vital to mitigate its pollution and harmful effects.
In this study two materials are combined to enhance the conductivity and ability of a glassy carbon electrode sensor to detect ornidazole. Carbon black, a material composed of 95% carbon with a structure similar to graphite [3] is functionalized using a novel green method with tannic acid. This is then combined with a layered double hydroxide (LDH) to act as a source of metal nanoparticles. LDH’s are a combination of transition metals with the general formula [M1-x
2+M3+
x(OH)2]x+(An-)x/n.mH2O where M is two different metals and A is the intercalated anion between the stacked layers of M2+/M3+
ions to produce a 2D layered nanosheet structure [4]. These LDHs are synthesized hydrothermally, which involves combining sources of the desired metals into a sealed autoclave and heating to produce a high vapour pressure environment.
Functionalized carbon black was dispersed and drop-casted onto the surface of the electrode. After drying, it was decorated by means of drop-casting with a dispersion of the LDH containing the desired elements. The LDH is then easily reduced by means of cyclic voltammetry to embed the nanoparticles of the desired elements into the carbon black, producing a stable modified electrode. LDH’s containing a variety of elements were investigated for their ability to detect ornidazole. The optimum element combination was concluded to be copper-iron nanoparticles. The procedure for the synthesis and modification of the electrode can be seen in Figure 1.
The carbon black-copper iron (CuFe) modified sensor shows excellent sensitivity compared to bare glassy carbon and is capable of detecting ornidazole concentrations from 0.2 μM to 600 μM, displaying excellent stability over multiple uses. Studies were performed to characterize the carbon black-CuFe material using SEM, XRD, XPS, FTIR, and EDX. Investigations were carried out into the behaviour of the sensor at varying pH values and to determine the reaction kinetics of detection. To study the selectivity of the sensor interferants were introduced to the antibiotic solution and experiments were performed in real water samples gathered from various locations.
[1] Q. Wang, C. Wang, Q. Wang, & Z. Wang, Journal of Agricultural and Food Chemistry., 2019, 67(41), 11527-11535
[2] W. El, N. Tajat, A. Idelahcen, M. Tamimi, S. Qourzal, A. Assabbane, & I. Bakas, Microchemical Journal, 2023, 195, 109397
[3] J. M. Martín-Martínez, Adhesion Science and Engineering : Surfaces, Chemistry and Applications, 2002, Chapter 13, 573-675
[4] A., Karmakar, K., Kannimuthu, S., Sam Sankar, K., Sangeetha, R., Madhu, & S., Kundu. Journal of Materials Chemistry A. 2020

Figure 1