Fabrication of novel electrochemical sensor for determination of vitamin C in the presence of vitamin B9 in food and pharmaceutical samples

An electrochemical sensor based on electrodeposited methylene blue on a carbon nanotube decorated hydrogel for the detection of ascorbic acid

In this study, a self-assembled electrochemical sensor was prepared by coating with a carbon nanotube (CNT) decorated hydrogel (HG) combined with electrodeposition of methylene blue (MB), and then used for the detection of ascorbic acid (AA). The three-dimensional network of HG has the advantages of large electroactive surface area, rapid diffusion and electron transfer rate, strong adhesive ability and stabilization of the polymerized MB. The MB provides high electrocatalytic activity and works as an electron transfer mediator to facilitate the oxidation of AA. The successful synthesis of the hydrogel and the preparation of the sensor are confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The layer-by-layer assembly was identified by AFM with the heights of 22.1 nm and 186.8 nm for the hydrogel and MB layers, respectively. Under the optimal conditions, the sensor has a linear range of 0.1 mM to 10 mM and a detection limit of 0.05 mM. What's more, the prepared sensor also exhibits good stability (current retention of 91.22% after 100 cycles for testing 0.25 mM AA), excellent anti-interference ability, good reproducibility (RSD of 4.26% for five independent experiments), excellent operational stability (RSD of 1.66% for 30 consecutive AA additions), fast response time (<4 s) and shows satisfactory results in the detection of AA in vitamin C tablets.

Lemon extract supported green synthesis of bimetallic CuO/Ag nanoporous materials for sensitive detection of vitamin D3

In modern era, deficiency of Vitamin D3 is predominantly due to limited exposure to sunlight and UV radiation resulting from indoor lifestyles. Several studies have revealed that vitamin D deficiency can lead to chronic vascular inflammation, diabetes mellitus, hypertension, congestive left ventricular hypertrophy, and heart failure. This study introduces a green synthesis of novel bimetallic nanoporous composite, CuO/Ag using lemon extract. The synthesized nanoporous material, CuO/Ag@lemon extract was characterized using several analytical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The CuO/Ag@lemon extract nanoparticles were immobilized on glassy carbon electrode (GCE) to prepare modified CuO/Ag@lemon extract-GCE interface. The electrocatalytic and electrochemical properties investigation was carried out on the modified electrode. using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry for detecting of Vitamin D3. The DPV method displayed a linear response range of 0.02-22.5 µM with a detection limit of 2.62 nM, while the amperometric method showed a broader linear range of 0.25-23.25 µM with a detection limit of 2.70 nM with 82% modified electrode stability. The designed electrode exhibited a positive response to the inclusion of Vitamin D3 with electro-oxidation, reaching steady-state within 3.4 s, with 87% reproducibility within a day. The proposed method offers a rapid and sensitive platform for detection of Vitamin D3 with minimal interference from other molecules. The early diagnosis of Vitamin D3 deficiency using modified electrodes allows for early treatment, thereby preventing severe health complications.

A highly sensitive switch-on spectrofluorometric method for determination of ascorbic acid using a selective eco-friendly approach

Ascorbic acid has recently been extensively used due to its role in the management of COVID-19 infections by stimulating the immune system and triggering phagocytosis of the corona virus. The currently used spectrofluorometric methods for determination of ascorbic acid require using derivatizing agents or fluorescent probes and suffer from a number of limitations, including slow reaction rates, low yield, limited sensitivity, long reaction times and high temperatures. In this work, we present a highly sensitive spectrofluorometric method for determination of ascorbic acid by switching-on the fluorescence of salicylate in presence of iron (III) due to a reduction of the cation to iron (II). The addition of ascorbic acid resulted in a corresponding enhancement in the fluorescence intensity of iron (III)-salicylate complex at emission wavelength = 411 nm. The method was found linear in the range of 1-8 µg/mL with a correlation coefficient of 0.9997. The limits of detection and quantitation were 0.035 µg/mL and 0.106 µg/mL, respectively. The developed method was applied for the determination of ascorbic acid in the commercially available dosage form; Ruta C60® tablets. The obtained results were compared with those obtained by a reported liquid chromatographic method at 95% confidence interval, no statistically significant differences were found between the developed and the reported methods. Yet, the developed spectrofluorometric method was found markedly greener than the reference method, based on the analytical Eco-scale and the green analytical procedure index. This work presents a simple, rapid and sensitive method that can possibly be applied for determination of ascorbic acid in pharmaceuticals, biological fluids and food samples.

Cost-effective and earth-friendly chemometrics-assisted spectrophotometric methods for simultaneous determination of Acetaminophen and Ascorbic Acid in pharmaceutical formulation

The development of analytical chemistry is omnipresent in all fields, this leads to considerable consumption of organic solvents and hazardous reagents with an increase in the production of waste to be treated. In this work, we developed simple, fast, cost-effective and above all environmentally friendly methods for the analysis of Acetaminophen (ACT) and Ascorbic acid (ASC) in synthetic mixtures and pharmaceutical formulation, using UV spectroscopy. Four chemometric methods were studied, including PLS-1 with full-spectrum (Full-PLS) and PLS-1 using three variable selection methods, namely subset selection through a genetic algorithm (GA), uninformative variable elimination using iterative predictor weighting (IPW), and variable selection by sub-window permutation analysis (SwPA). The accuracy of the developed methods was evaluated through the root mean square error of prediction (RMSEP), the mean absolute percentage error (MAPE) and the recovery values. All methods showed more accurate prediction results in comparison with full-PLS calibration. Furthermore, the results indicate that the GA-PLS models showed the highest prediction accuracy among all other models with RMSEP and MAPE values of (0.0494 and 0.610) and (0.0163 and 0.321) for the estimation of ACT and ASC, respectively. The proposed methods were successfully applied to the determination of ACT and ASC in their combined dosage form. In addition, the results obtained were statistically compared to those of the conventionally used HPLC method and were found to be in good agreement. The main advantages of the developed methods over HPLC during routine analysis are that they are faster, inexpensive, simple to perform, without the need for major pretreatment of samples. Besides, no organic solvents are used, and thus toxicity and pollution are avoided.

Sensitive spectrofluorometric method for the determination of ascorbic acid in pharmaceutical nutritional supplements using acriflavine as a fluorescence reagent

An easily performed, specific, sensitive, rapid, reliable and inexpensive procedure for the spectrofluorometric quantitation of ascorbic acid was proposed using acriflavine as a fluorescence quenching reagent. The procedure was based on the determined quenching effect of ascorbic acid on the natural fluorescence signal of acriflavine and the reaction between ascorbic acid and acriflavine in Britton-Robinson buffer solution (pH 6) to produce an ion-associated complex. The reduction in acriflavine fluorescence intensity was detected at 505 nm, while excitation occurred at 265 nm. The relationship between quenching fluorescence intensity (∆F) and concentration of ascorbic acid was linear (R²  = 0.9967) within the range 2-10 μg/ml and with a detection limit of 0.08 μg/ml. No significant interference was detected from other materials often found in pharmaceutical nutritional tablets. The obtained results were compared with those from high-performance liquid chromatography and appeared in good agreement, with no important differences in precision or accuracy. The proposed spectrofluorimetric method was used to determine the amount of ascorbic acid in a number of commercial pharmaceutical nutritional supplement tablets with a 95% confidence performance.

Fabrication of a Food Nano-Platform Sensor for Determination of Vanillin in Food Samples

Herein, we describe the fabrication of NiO decorated single wall carbon nanotubes (NiO-SWCNTs) nanocomposites using the precipitation method. The synthesized NiO-SWCNTs nanocomposites were characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Remarkably, NiO-SWCNTs and 1-butylpyridinium hexafluorophosphate modified carbon paste electrode (CPE/NiO-SWCNTs/BPrPF6) were employed for the electrochemical detection of vanillin. The vanillin sensor showed an ultra-high sensitivity of 0.3594 μA/μM and a low detection limit of 0.007 μM. In the final step, the NiO-SWCNTs/BPrPF6 was used as the suitable tool for food analysis.

Low-cost and disposable sensors for the simultaneous determination of coenzyme Q10 and α-lipoic acid using manganese (IV) oxide-modified screen-printed graphene electrodes

In this work, for the first time, manganese (IV) oxide-modified screen-printed graphene electrodes (MnO₂/SPGEs) were developed for the simultaneous electrochemical detection of coenzyme Q10 (CoQ10) and α-lipoic acid (ALA). This sensor exhibits attractive benefits such as simplicity, low production costs, and disposability. Cyclic voltammetry (CV) was used to characterize the electrochemical behavior of the analyte and investigate the capacitance and electroactive surface area of the unmodified and modified electrode surfaces. The electrochemical behavior of CoQ10 and ALA on MnO₂/SPGEs was also discussed. Additionally, square wave anodic stripping voltammetry (SWASV) was used for the quantitative determination of CoQ10 and ALA. Under optimal conditions, the obtained signals are linear in the concentration range from 2.0 to 75.0 μg mL^-1 for CoQ10 and 0.3-25.0 μg mL^-1 for ALA. The low limits of detection (LODs) were found to be 0.56 μg mL^-1 and 0.088 μg mL^-1 for CoQ10 and ALA, respectively. Moreover, we demonstrated the utility and applicability of the MnO₂/SPGE sensor through simultaneous measurements of CoQ10 and ALA in dietary supplements. The sensor provides high accuracy measurements, exhibiting its high potential for practical applications.

Rapid Detection of Ascorbic Acid Based on a Dual-Electrode Sensor System Using a Powder Microelectrode Embedded with Carboxyl Multi-Walled Carbon Nanotubes

In this paper, carboxyl groups were introduced by liquid oxidation methods onto multi-walled carbon nanotubes (MWCNTs) to improve the MWCNTs' electrocatalytic properties. A platinum wire microelectrode (ME) was corroded using aqua regia and subsequently embedded with MWCNTs to achieve more active sites, producing a so-called powder microelectrode (PME). Compared with conventional MEs, the PME has a larger specific surface area and more active sites. When PME was used to detect ascorbic acid (AA), the AA oxidation potential shifted negatively and current peak was visibly increased. The calibration curve obtained for AA was in a range of 5.00 × 10-6~9.50 × 10-4 mol·L-1: Ipa(μA) = 3.259 × 10-2+ 1.801 × 10² C (mol·L-1) under the optimum testing conditions. Moreover, the detection and quantitation limits were confirmed at 4.89 × 10-7 mol·L-1 and 1.63 × 10-7 mol·L-1, respectively. When the fabricated PME was practically applied to detect AA, it was shown a recovery rate of 94~107% with relative standard deviation (RSD) <5%. The proposed strategy thus offers a promising, rapid, selective and low-cost approach to effective analysis of AA.

A multifunctional Ni(ii) coordination polymer: synthesis, crystal structure and applications as a luminescent sensor, electrochemical probe, and photocatalyst

A new Ni(ii) complex containing 2,5-dichloroterephthalate and rigid bis(imidazole) ligands, which manifests multifunctional properties, has been synthesized and characterized.