Sensitive amperometric detection of omeprazole and pantoperazole at electrodeposited nickel oxide nanoparticles modified glassy carbon electrode

An amplified electrochemical sensor employing one-step synthesized nickel-copper-zinc ferrite/carboxymethyl cellulose/graphene oxide nanosheets composite for sensitive analysis of omeprazole

In this work, a signal amplification strategy was designed by the fabrication of a highly sensitive and selective electrochemical sensor based on nickel-copper-zinc ferrite (Ni0.4Cu0.2Zn0.4Fe2O4)/carboxymethyl cellulose (CMC)/graphene oxide nanosheets (GONs) composite modified glassy carbon electrode (GCE) for determination of omeprazole (OMP). The one-step synthesized Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy and X-ray diffraction techniques. Then, the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE was applied to study the electrochemical behavior of the OMP. Electrochemical data show that the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE exhibits superior electrocatalytic performance on the oxidation of OMP compared with bare GCE, GONs/GCE, CMC/GONs/GCE and MFe2O4/GCE (M = Cu, Ni and Zn including single, double and triple of metals) which can be attributed to the synergistic effects of the nanocomposite components, outstanding electrical properties of Ni0.4Cu0.2Zn0.4Fe2O4 and high conductivity of CMC/GONs as well as the further electron transport action of the nanocomposite. Under optimal conditions, the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE offers a high performance toward the electrodetermination of OMP with the wide linear-range responses (0.24-5 and 5-75 μM), lower detection limit (0.22 ± 0.05 μM), high sensitivity (1.1543 μA μM-1 cm-2), long-term signal stability and reproducibility (RSD = 2.54%). It should be noted that the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE sensor could also be used for determination of OMP in drug and biological samples, indicating its feasibility for real analysis.

Electrochemical sensor based on 3D-printed substrate by masked stereolithography (MSLA): a new, cheap, robust and sustainable approach for simple production of analytical platforms

The development of miniaturized, sustainable and eco-friendly analytical sensors with low production cost is a current trend worldwide. Within this idea, this work presents  the innovative use of masked stereolithography (MSLA) 3D-printed substrates for the easy fabrication of pencil-drawn electrochemical sensors (MSLA-3D-PDE). The use of a non-toxic material such as pencil (electrodes) together with a biodegradable 3D printing resin (substrate) allowed the production of devices that are quite cheap (ca. US$ 0.11 per sensor) and with low environmental impact. Compared to paper, which is the most used substrate for manufacturing pencil-drawn electrodes, the MSLA-3D-printed substrate has the advantages of not absorbing water (hydrophobicity) or becoming crinkled and weakened when in contact with solutions. These features provide more reproducible, reliable, stable, and long-lasting sensors. The MSLA-3D-PDE, in conjunction with the custom cell developed, showed excellent robustness and electrochemical performance similar to that observed of the glassy carbon electrode, without the need of any activation procedure. The analytical applicability of this platform was explored through the quantification of omeprazole in pharmaceuticals. A limit of detection (LOD) of 0.72 µmol L^-1 was achieved, with a linear range of 10 to 200 µmol L^-1. Analysis of real samples provided results that were highly concordant with those obtained by UV-Vis spectrophotometry (relative error ≤ 1.50%). In addition, the greenness of this approach was evaluated and confirmed by a quantitative methodology (Eco-Scale index). Thus, the MSLA-3D-PDE appears as a new and sustainable tool with great potential of use in analytical electrochemistry.

Metal-free Sulfur-doped graphitic carbon nitride-modified GCE-based electrocatalyst for the enhanced electrochemical determination of Omeprazole in Drug formulations and Biological Samples

This study presents a novel sulfur-doped graphitic carbon nitride (S@g-C₃ N₄ ) with a wider potential range as electrocatalyst for electrochemical sensor application. The S@g-C₃ N₄ nanosheets were successfully prepared with a ball milling method by mixing appropriate molar concentration required precursors. The as-synthesized heteroatom-doped graphitic carbon nitride is characterized by spectroscopic techniques including PL, DRS-UV, FT-IR, and Brunauer-Emmett-Teller equation. The morphological features were studied by FE-SEM and HR-TEM analysis. Chit-S@g-C₃ N₄ -modified glassy carbon electrode (GCE) was employed for the electrochemical detection of omeprazole (OMZ) use in drug formulations. We have noted an oxidation peak current response at a potential of +0.8 V versus Ag/AgCl in PBS medium (0.1 M, pH 7.0). Differential pulse voltammetry amperometry experimental method can be used to measure the concentration of OMZ for quantitative studies in known samples. Under the optimized experimental condition, the calibration plot was constructed by plotting the peak currents versus OMZ in the linear ranges from 6.0 × 10^-7 to 26 × 10^-5  M. The linear regression equation is estimated to be I_p (μA) = 0.9518 (C/μM) + 0.3340 with a good correlation coefficient of 0.9996. The lower determination limit was found to be 20 nM and the current sensitivity was calculated (31.722 μA μM^-1  cm^-2 ). The developed sensor was utilized successfully to determine the OMZ concentration in drug formulations and biological fluids. These results revealed that the Chit-S@g-C₃ N₄ -modified GCE showed excellent electroanalytical performance for the detection of OMZ at a low LOD, wider linear range, high sensitivity, good reproducibility, long-term storage stability, and selectivity with an acceptable relative standard deviation value.

An electrochemical sensor based on an Eriochrome Black T polymer and deep eutectic solvent for the simultaneous determination of omeprazole and lansoprazole

Here we report the fabrication of an electrochemical sensor for the simultaneous determination of the concentrations of omeprazole (OMZ) and lansoprazole (LAN) in biological fluids and pharmaceuticals in Britton-Robinson buffer solution (pH 6.0). The sensor was prepared by bulk modifying a carbon paste electrode with deep eutectic solvent (DES), followed by carrying out electropolymerization of Eriochrome Black T (EBT) at this electrode. The presence of DES increased the extent of the polymerization of EBT on the surface of the electrode, and this increase led to better OMZ and LAN electron transfer kinetics at the electrode surface. The modified electrode was evaluated and characterized by performing cyclic voltammetry, electrochemical impedance spectroscopy, scanning electronic microscopy, and Fourier-transform infrared spectroscopy. The best responses were obtained in drug-free Britton-Robinson buffer solution (pH 6.0) after 600 s of stirring at the open circuit potential. Linear relationships were obtained between the anodic peak currents and the concentrations of OMZ and LAN in the ranges of 0.010-0.276 and 0.010-0.300 μM, with detection limits of 0.006 and 0.009 μM, respectively. Satisfactory results were also obtained for the analysis of OMZ and LAN in real samples. The excellent sensitivity and easy regeneration and modification of this electrode with DES followed by the polymerization of EBT make this electrode relatively highly applicable for flow methods.

Nanostructured materials in electroanalysis of pharmaceuticals

Basic strategies and recent developments for the enhancement of the sensory performance of nanostructures in the electroanalysis of pharmaceuticals are reviewed. A discussion of the properties of nanostructures and their application as modified electrodes for drug assays is presented. The electrocatalytic effect of nanostructured materials and their application in determining low levels of drugs in pharmaceutical forms and biofluids are discussed.

Potentiometric determination of pantoprazole using an ion-selective sensor based on polypyrrole doped films

The present work reports for the first time the use of polypyrrole (PPy) doped film for development of a potentiometric disposable sensor for determination of pantoprazole (PTZ), a drug used for ulcer treatment. Selective potentiometric response has been found by using a membrane of PPy doped with PTZ anions prepared under galvanostatic conditions at graphite pencil electrode (GPEM/PPy-PTZ) surface. Potentiometric response has been influenced for conditions adopted in polymerization and measurement step. After optimization of experimental (e.g. pH and time of conditioning) and instrumental parameters (e.g. current density and electrical charge) a linear analytical curve from 1.0 × 10(-5) to 1.1 × 10(-2) mol L(-1) with a slope of calibration of the 57.6 mV dec(-1) and limit of detection (LOD) of 6.9 × 10(-6) mol L(-1) was obtained. The determination of the PTZ content in pharmaceutical samples using the proposed methodology and official method recommended by Brazilian Pharmacopeia are in agreement at the 95% confidence level and within an acceptable range of error.

Electrocatalytic activity of nickel oxide nanoparticles as mediatorless system for NADH and ethanol sensing at physiological pH solution

The glassy carbon (GC) electrode modified by nickel oxide nanoparticles (NiOxNPs) is proposed as a novel electrocatalytic system for the oxidation of NADH without using any electron transfer mediator. Here, chronoamperometry was used not only as a simple method for the deposition of NiOxNPs onto the GC electrode but also as an efficient tool in the controlling of nanoparticles size and efficient electrocatalytic activity. The surface morphology and electrochemical properties of the NiOxNPs/GC electrode was investigated using scanning electron microscopy and cyclic voltammetry techniques, respectively. The NPs are deposited uniformly across the GC surface and the size of NiOxNPs varies from 20 to less than 100 nm. The NiOxNPs/GC electrode shows excellent electrocatalytic activity toward oxidation of NADH at reduced overvoltage. The detection limit and sensitivity of the modified electrode toward NADH were estimated to be 106 nM (S/N=3) and 0.052 μAμM(-1), respectively at a concentration range up to 1mM. Due to the biocompatibility of NiOxNPs toward biomolecules, this modified electrode can be used as an efficient transducer in the design of an ethanol biosensor based on the coupled alcohol dehydrogenase enzyme(ADH). Hydrodynamic amperometric detection of ethanol on the ADH-Nafion/NiOxNPs/GC modified electrode gives linear responses over the concentration range of 0.2-6mM with a detection limit of 6.4 μM and sensitivity of 36 nA mM(-1). Applicability of the proposed biosensor for ethanol detection in real samples, easy and simple preparation, being mediator free, high sensitivity and biocompatibility are the major advantages of the proposed biosensor.