Modification of carbon paste electrode with Fe(III)-clinoptilolite nano-particles for simultaneous voltammetric determination of acetaminophen and ascorbic acid

Toward an Improved Electrocatalytic Determination of Immunomodulator COVID Medication Baricitinib Using Multiwalled Carbon Nanotube Nickel Hybrid

The study presents a first electrochemical method for the determination of the immunomodulator drug Baricitinib (BARI), crucial in managing COVID-19 patients requiring oxygen support. A unique electrode was developed by modifying graphite carbon nickel nanoparticles (NiNPs) with functionalized multiwalled carbon nanotubes (f.MWCNTs), resulting in nanohybrids tailored for highly sensitive BARI detection. Comparative analysis revealed the superior electrocatalytic performance of the nanohybrid-modified electrode over unmodified counterparts and other modifications, attributed to synergistic interactions between f.MWCNTs and nickel nanoparticles. Under optimized conditions, the sensors exhibited linear detection within a concentration range from 4.00 × 10-8 to 5.56 × 10-5 M, with a remarkably low detection limit of 9.65 × 10-9 M. Notably, the modified electrode displayed minimal interference from common substances and demonstrated high precision in detecting BARI in plasma and medicinal formulations, underscoring its clinical relevance and potential impact on COVID-19 treatment strategies.

N,Si co-doped GQDs: Facile green preparation and application in visual identifying dihydroxybenzene isomers and selective quantification of catechol, hydroquinone and antioxidants

A green economical procedure for preparing N,Si co-doped graphene quantum dots (N,Si-GQDs) using waste toners and ethylene diamine was reported, which not only minimizes waste and promotes recycling but also offers an alternative method for producing N,Si-GQDs. At a pH of 8.5, hydroquinone and catechol underwent oxidation in the presence of air, resulting in the formation of diquinones, specifically p-phenyldiquinone and o-phenyldiquinone. Resorcinol, on the other hand, was converted into monoquinone. The interaction between diquinones and N,Si-GQDs caused a linear fluorescence quenching effect when catechol and hydroquinone were present. However, this effect was minimal in the case of resorcinol. Furthermore, the antioxidants glutathione (GSH) and ascorbic acid (AA) were observed to disrupt the redox equilibrium of catechol and o-phenyldiquinone, leading to the activation of fluorescence. Conversely, hydroquinone and p-phenyldiquinone, due to the highly stable and symmetrical structure of p-phenyldiquinone, did not exhibit this fluorescence activation. Based on the described "Off-On" sensor system, it was possible to visually identify dihydroxybenzene isomers and selectively quantify catechol and hydroquinone in environmental samples, as well as GSH and AA in human serum. The method detection limits were 0.93, 1.35, 2.34, and 1.37 μM for catechol, hydroquinone, GSH, and AA, respectively. In conclusion, the presented procedure offers several advantages, including environmental friendliness, cost-effectiveness, and a means of recycling waste toners. It also demonstrates the successful synthesis of N,Si-GQDs, as well as the potential for their application in the "Off-On" sensor system for the detection and quantification of various analytes.

Electrochemical sensing platform based on Zeolite/Graphite/Dimethylglyoxime nanocomposite for highly selective and ultrasensitive determination of nickel

In this work, the fabrication and analytical application of a novel, unique, mercury-free, and user-friendly voltammetric sensor of Ni(II) based on glassy carbon electrode (GCE) modified with zeolite(MOR)/graphite(G)/dimethylglyoxime(DMG) composite (MOR/G/DMG-GCE) and the voltammetric procedure for highly selective, ultra-trace determination of nickel ions were reported for the first time. Deposition of a thin layer of the chemically active MOR/G/DMG nanocomposite enables the selective and effective accumulation of Ni(II) ions in the form of the DMG-Ni(II) complex. In 0.1 mol L^-1 ammonia buffer (pH 9.0), the MOR/G/DMG-GCE exhibited linear response in the Ni(II) ions concentration range of 0.86 - 19.61 µg L^-1 and 0.57 - 15.75 µg L^-1, for the accumulation time of 30 s and 60 s, respectively. For 60 s of accumulation time, the limit of detection (S/N = 3) was 0.18 µg L^-1 (3.04 nM), and sensitivity of 0.202 µA L µg^-1 was achieved. The developed protocol was validated by the analysis of wastewater certified reference materials. Its practical usefulness was confirmed by the determination of nickel released from metallic jewelry submerged in artificial sweat and stainless steel pot during water boiling. The obtained results were verified by electrothermal atomic absorption spectroscopy as a reference method.

Clinoptilolite based zeolite-geopolymer hybrid foams: Potential application as low-cost sorbents for heavy metals

Clinoptilolite based zeolite-geopolymer foams (abbreviated as CFs) were prepared from natural clinoptilolite and calcined clinoptilolite, using H₂O₂ solution as pore former through a straightforward process. Natural clinoptilolite and CFs are characterized by analytical techniques including optical microscope, XRF, FTIR, XRD, BET, MIP and SEM. The obtained CFs possesses micropores of zeolite and meso/macropores of geopolymer matrix. The porosities range from 66.7 to 69.5%. Clinoptilolite (partially dissolved) and impurity minerals (montmorillonite, illite and albite) contribute to the formation of geopolymer. CFs shows a good static sorption performance for toxic heavy metals at pH = 5 and sorption time of 24 h. Results show that the adsorption amount of CFs for Cr³⁺, Pb²⁺, Ni²⁺, Cu²⁺ and Cd²⁺ in the 50 mg/L working solutions are 6.21 mg/g, 6.11-6.13 mg/g, 5.92-6.07 mg/g, 5.53-5.93 mg/g and 5.44-5.79 mg/g, respectively. In addition, CFs could reach a high removal rate (Cr removal rate >80% and Cd > 60%) for different heavy metals after three cycles. The elimination order of toxic metals is Cr³⁺ > Pb²⁺ > Ni²⁺ > Cu²⁺ > Cd²⁺. The sequence is in accordance with Hard-Soft-Acid-Base principle, it is also related to the speciation and the ionic radii of the hydrated metal ions. This research provides a feasible approach for preparation of promising foams sorbent based on natural zeolite for wastewater management.

Dual recognition strategy for selective fluorescent detection of dopamine and antioxidants based on graphite carbon nitride in human blood serum

In this work, a strong blue-emitting fluorescent biosensor based on graphite carbon nitride nanoparticles (GCNNs) (E_x = 340 nm and E_m = 435 nm) was synthesized by a facile one-step hydrothermal method. With the aid of hydrogen peroxide and horseradish peroxidase, pyrocatechol structure of dopamine (DA) was oxidized to o-quinone structure of polydopamine (PDA) by hydroxyl radical. PDA was able to rapidly and significantly quench fluorescence of GCNNs. In the meanwhile, oxidative self-polymerization from DA to PDA would be blocked by antioxidants, such as glutathione (GSH) and ascorbic acid (AA). Thus, the fluorescence of GCNNs@DA sensor would be recovered owing to the decrease of o-quinone. Based on above-mentioned dual recognition strategy of "turn-off" and "turn off-on", a fast, simple and ultrasensitive method was developed to measure DA and antioxidants. Under the optimal experimental conditions, the detection limits of DA, GSH and AA were 0.064 μmol L^-1, 0.11 μmol L^-1 and 0.16 μmol L^-1 with relative standard deviations of 1.7%, 9.3% and 8.0%, respectively. As one of metal-free quantum dots, our GCNNs-based sensors were also successfully applied to the determination of DA as well as GSH and AA in human serum. The recoveries for the spiked samples were in the range of 93.8%-109% and 95.0%-110% of DA and antioxidants, which shows great promise to clinicalapplication.

Decentralized vitamin C & D dual biosensor chip: Toward personalized immune system support

Combating the ongoing COVID-19 pandemic has put the spotlight on nutritional support of the immune system through consumption of vitamins C and D. Accordingly, there are urgent demands for an effective on-the-spot multi-vitamin self-testing platform that monitors the levels of these immune-supporting micronutrients for guiding precision nutrition recommendations. Herein, we present a compact bioelectronic dual sensor chip aimed at frequent on-the-spot simultaneous monitoring of the salivary vitamin C and D dynamics. The new bioelectronic chip combines a new electrocatalytic vitamin C amperometric assay along with competitive vitamin D immunoassay on neighboring electrodes, to perform selective and cross-talk free detection of both vitamins in a 10-μL saliva sample within 25 min. The distinct vitamin C or D temporal profiles obtained for different individuals after vitamin supplementation indicate the potential of the new bioelectronic chip strategy for enhancing personalized nutrition towards guiding dietary interventions to meet individual nutrition needs and promote immune system health.

The photocatalytic rate of ZnO supported onto natural zeolite nanoparticles in the photodegradation of an aromatic amine

Aniline and its derivate are critical environmental pollutants, and thus, the introduction of an eco-friendly catalyst for removing them is an important research future. The ZnO supported on the ball-mill prepared clinoptilolite nanoparticles (CNPs) was prepared via an ion-exchange process followed by the calcination process. The amount of loaded ZnO in the ZnO-CNP (CZ) samples varied as 0.54, 0.63, 0.72, and 0.86 meq/g as the Zn(II) concentration in the ion-exchange solution varied from 0.1 to 0.5 M. The ZnO-CNP catalyst was briefly characterized by XRD, FTIR, and DRS techniques. The pHpzc value for the various ZnO-CNPs was about 7.1 that had no change with the ZnO loading. By applying the Scherrer equation on the XRD results, a nano-dimension of about 50 nm was obtained for the catalyst. Bandgap energy of the ZnO-CNP samples was estimated by applying the Kubelka-Munk equation on the DRS reflectance spectra. The value for the CZ2 catalyst was about 3.64 eV. The supported ZnO-CNP sample was then used in the photodegradation of 2,4-dichloroaniline (DCA). Raw zeolite showed a relatively low photocatalytic activity. The degradation efficiency was followed by recording the absorbance of the DCA solution by UV-Vis spectrophotometer. The effects of the essential critical operating factors on the degradation efficiency were kinetically studied by applying the Hinshelwood equation to the results. The ZnO-CNP catalyst with 2 w% ZnO showed the best photocatalytic rate in the optimal conditions of 0.75 g/L, C_DCA: 15 ppm, and the initial pH: 5.8. Finally, HPLC analysis of the blank and the photodegraded DCA solutions at 180 and 300 min confirmed 74 and 87% of DCA molecules were degraded during these times. The results confirm that supported ZnO onto clinoptilolite caused enhanced photocatalytic activity because the zeolite internal electrical field prevents the e^-/h⁺ recombination.

Selective Voltammetric Detection of Ascorbic Acid from Rosa Canina on a Modified Graphene Oxide Paste Electrode by a Manganese(II) Complex

Voltammetric techniques have been considered as an important analytical tool applied to the determination of trace concentrations of many biological molecules including ascorbic acid. In this paper, ascorbic acid was detected by square wave voltammetry, using graphene oxide paste as a working electrode, modified by a film of a manganese(II) complex compound. Various factors, such as the effect of pH, affecting the response characteristics of the modified electrode were investigated. The relationship between the peak height and ascorbic acid concentration within the modified working electrode was investigated, using the calibration graph. The equation of the calibration graph was found to be: I = 0.0550γac + 0.155 with R2 = 0.9998, where I is the SWV current and γac is the mass concentration of ascorbic acid. The LOD and LOQ of the proposed method were determined to be 1.288 μg/L and 3.903 μg/L, respectively. Several compounds, such as riboflavin, biotin, and ions, such as Fe and Cu, were tested and it seemed that they did not interfere with the analytic signal. The proposed procedure was successfully applied in the determination of ascorbic acid in Rosa canina hips.

Cathode materials for aqueous zinc-ion batteries: A mini review

Although lithium-ion batteries (LIBs) have many advantages, they cannot satisfy the demands of numerous large energy storage industries owing to their high cost, low security, and low resource richness. Aqueous zinc-ion batteries (ZIBs) with low cost, high safety, and high synergistic efficiency have attracted an increasing amount of attention and are considered a promising choice to replace LIBs. However, the existing cathode materials for ZIBs have many shortcomings, such as poor electron and zinc ion conductivity and complex energy storage mechanisms. Thus, it is crucial to identify a cathode material with a stable structure, substantial limit, and suitability for ZIBs. In this review, several typical cathode materials for ZIBs employed in recent years and their detailed energy storage mechanisms are summarized, and various methods to enhance the electrochemical properties of ZIBs are briefly introduced. Finally, the existing problems and expected development directions of ZIBs are discussed.

Effect of nano-SiO2 packing on postharvest quality and antioxidant capacity of loquat fruit under ambient temperature storage

Effect of nano-SiO₂ packing on postharvest quality and antioxidant capacity of two different loquat cultivars (white-flesh 'Qingzhong' and red-flesh 'Dawuxing') were determined. Results showed that nano-SiO₂ packing significantly inhibited internal browning, retarded the decline of total soluble solids, titratable acidity, ascorbic acid content and extractable juice in both cultivars. Decay index of nano-SiO₂ packing in 'Dawuxing' and 'Qingzhong' was 53.25% and 42.84% lower than control after the day 12, respectively. Meanwhile, nano-SiO₂ packing enhanced the contents of individual phenolic compounds and soluble sugar compounds, induced higher superoxide dismutase and catalase activities, which contributed to improving 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radical scavenging capacity. Furthermore, the contents of total soluble solids, ascorbic acid and soluble sugar were higher in 'Qingzhong' than those in 'Dawuxing', which dedicated to better quality. These results indicated that nano-SiO₂ packing was a promising approach in inhibiting decay, maintaining quality and expanding shelf life of loquats.

Electrochemical determination of paracetamol in a pharmaceutical dose by adsorptive voltammetry with a carbon paste/La2O3 microcomposite

This paper presents a new application for microcomposites based on carbon paste (CP) and La2O3 (LaOX). This simple and versatile microcomposite (LaOX/CPE) was applied toward the determination of paracetamol (PCM) through proton oxidation by square wave adsorptive voltammetry (SWAdV). The anodic peak current for PCM increased by nearly 70.0% compared with an unmodified CP, and the detection limit was 0.020 μmol L-1. The relative standard deviations (RSDs) were 1.0% (n = 7). The accuracy of the new method was evaluated with tap water spiked with known quantities of PCM, while ascorbic acid, caffeine, and acetylsalicylic acid were used for interference studies. Finally, the usefulness of the microcomposite was shown to have acceptable results when applied to detect and quantify PCM in various forms of a pharmaceutical dose, such as solid tablets, fruit-flavored powders for colds and syrups for children.

Developments and applications of nanomaterial-based carbon paste electrodes

This review summarizes the progress that has been made in the past ten years in the field of electrochemical sensing using nanomaterial-based carbon paste electrodes. Following an introduction into the field, a first large section covers sensors for biological species and pharmaceutical compounds (with subsections on sensors for antioxidants, catecholamines and amino acids). The next section covers sensors for environmental pollutants (with subsections on sensors for pesticides and heavy metal ions). Several tables are presented that give an overview on the wealth of methods (differential pulse voltammetry, square wave voltammetry, amperometry, etc.) and different nanomaterials available. A concluding section summarizes the status, addresses future challenges, and gives an outlook on potential trends.

This review summarizes the progress that has been made in the past ten years in the field of electrochemical sensing using nanomaterial-based carbon paste electrodes.

Flow-Injection Chemiluminescence Method for Sensitive Determination of Ascorbic Acid in Fruit Juices and Pharmaceutical Samples Using a Luminol-Cetyltrimethylammonium Chloride Reversed Micelle System

A highly sensitive flow-injection (FI) method was developed for the determination of ascorbic acid using chemiluminescence (CL) based detection. This method involved the following processes: (1) reduction of tetrachloroaurate(III) in hydrochloric acid with ascorbic acid; (2) on-line extraction of the residual Au(III) with rhodamine B from the aqueous hydrochloric acid solution into toluene, followed by the separation of the Au(III)-containing organic phase from the aqueous phase through a microporous Teflon membrane in the flow system; and (3) the measurement of CL produced in a flow cell upon mixing of the extract stream of Au(III) in toluene with luminol in the reversed micellar medium of cetyltrimethylammonium chloride-water in 1-hexanol-cyclohexane, which was injected into a CL reagent stream. In this procedure, a reduction in the CL intensity occurred due to the addition of ascorbic acid to the Au(III) solution. The CL signal of Au(III) decreased with increasing concentration of ascorbic acid in the aqueous sample solution. The proposed procedure allowed the indirect quantitative determination of ascorbic acid in the range of 1.0 × 10^-12 to 1.0 × 10^-7 M with a correlation coefficient of 0.987 and relative standard deviation of 2.1% (n = 6) at 1.0 × 10^-9 M. The proposed FI-CL methodology was successfully applied for quantitative determination of ascorbic acid in fruit juices and pharmaceutical samples.

Simultaneous determination of acetaminophen, pramipexole and carbamazepine by ZSM-5 nanozeolite and TiO2 nanoparticles modified carbon paste electrode

In this present paper, a simple voltammetric method has been reported for the simultaneous determination of acetaminophen (AC), pramipexole (PRX) and carbamazepine (CBZ) using ZSM-5 nanozeolite-TiO₂ nanoparticles composite modified carbon paste electrode (ZSM-5/TiO₂/CPE). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and N₂ adsorption-desorption isotherm were used to characterize the structure of synthesized ZSM-5 nanozeolite. Also, cyclic voltammetry (CV), choronoamperometry and differential pulse voltammetry (DPV) were used to investigate the performance of the modified electrode. The oxidation peak currents of AC, PRX and CBZ at the surface of ZSM-5/TiO₂/CPE were increased dramatically against CPE and their overpotentials decreased. Also, DPV method was used for the simultaneous determination of three drugs in ternary mixture. The effects of modifier amount, pH and scan rate were investigated on the electrochemical response of AC, PRX and CBZ oxidation. The diffusion coefficient, D, and the catalytic rate constant, k_cat, were estimated for the oxidation of AC, PRX and CBZ at the surface of modified electrode. Under the optimized experimental conditions, AC, PRX and CBZ give linear response over the range of 2.5-110, 0.6-105 and 6.0-97 μM, respectively. The detection limits were found to be 0.58, 0.38 and 1.04 μM (S/N = 3) for AC, PRX and CBZ, respectively. The fabricated electrode showed good stability, reproducibility and repeatability as well as high recovery. The practical application of the modified electrode was demonstrated by measuring the concentration of spiked AC, PRX and CBZ in human plasma as real sample. The proposed method is simple, rapid and inexpensive and can be utilized as a valuable analytical tool in quality control of the pharmaceutical industry.

Applications of zeolites in biotechnology and medicine – a review

Zeolites are microporous natural or synthetic tectosilicates, promising for organism detoxification, improvement of the nutrition status and immunity, separation of various biomolecules and cells, detection of biomarkers of various diseases, controlled drug and gene delivery, radical scavenging, haemostasis, tissue engineering and biomaterial coating.

Synergistic effect of p-n heterojunction, supporting and zeolite nanoparticles in enhanced photocatalytic activity of NiO and SnO2

Increased photocatalytic activity of NiO and SnO₂ was achieved by coupling and supporting of them onto clinoptilolite nanoparticles (NC) via calcination of Ni(II)-Sn(IV) - exchanged NC in photocatalytic degradation of metronidazole (MZ) aqueous solution. XRD, XRF, FTIR, SEM, X-ray mapping, DRS, TEM, BET Cyclic voltammetry and electrochemical impedance spectroscopy techniques (EIS) were used for characterization of samples. Red shift occurred in bang gap energies of the coupled semiconductors with respect to monocomponent one. This p-n hetero-junction forms a depletion layer in the semiconductors interface with negative and positive charges, causing considerable enhancement in the photocatalytic activity. The calcined catalyst at 600°C for 4h showed the best photocatalytic activity and charge transfer efficiency (in EIS results). The mole ratio of SnO₂/NiO affects the degradation activity of the catalysts and the best activity were was obtained for the NiO_1.1-SnO_2(6.7)/NC (NS₅-NC) catalyst at pH 3, 1.2gL^-1 of the catalyst and 2mgL^-1 of MZ. SnO₂ played electron sink role and the photogenerated electrons migrate from more negative C_b-NiO (E=-3.0V) to C_b-SnO₂ (E=-0.3V vs SHE). Initial pH of MZ solution was changed from 6.20 to 4.73 during 180min that confirms formation of Oxalic acid and Maleic acid.

Electroanalytical Performance of a Carbon Paste Electrode Modified by Coffee Husks for the Quantification of Acetaminophen in Quality Control of Commercialized Pharmaceutical Tablets

Electrochemical determination of acetaminophen (APAP) was successfully performed using a carbon paste electrode (CPE) modified with coffee husks (CH-CPE). Scanning electron microscopy (SEM) and SEM-energy dispersive X-ray spectroscopy (SEM-EDX) were, respectively, used for the morphological and elemental characterization of coffee husks prior to their utilization. The electrochemical oxidation of APAP was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV). SWV technique appeared to be more sensitive since the oxidation current of APAP was twofold higher with the CH-CPE sensor than with the bare CPE, in relation to the increase in the organophilic character of the electrode surface. Furthermore, on CH-CPE, the current response of APAP varied linearly with its concentration in the range of 6.6 μM to 0.5 mM, leading to a detection limit of 0.66 μM (S/N=3). Finally, the proposed CH-CPE sensor was successfully used to determine the amount of APAP in commercialized tablets (Doliprane® 500 and Doliprane 1000), with a recovery rate ranging from 98% to 103%. This novel sensor opens the way for the development of low-cost and reliable devices for the electroanalysis of pharmaceutical formulations in developing countries.

Design and characterization of chitosan/zeolite composite films--Effect of zeolite type and zeolite dose on the film properties

Chitosan films can be used as wound dressings for the treatment of chronic wounds and severe burns. The antimicrobial properties of these films may be enhanced by the addition of silver. Despite the antimicrobial activity of silver, several studies have reported the cytotoxicity as a factor limiting its biomedical applications. This problem may, however, be circumvented by the provision of sustained release of silver. Silver zeolites can be used as drug delivery platforms to extend the release of silver. The objective of this study was to evaluate the addition of clinoptilolite and A-type zeolites in chitosan films. Sodium zeolites were initially subjected to ion-exchange in a batch reactor. Films were prepared by casting technique using a 2% w/w chitosan solution and two zeolite doses (0.1 or 0.2% w/w). Films were characterized by thermal analysis, color analysis, scanning electron microscopy, X-ray diffraction, and water vapor permeation. The results showed that films present potential for application as dressing. The water vapor permeability is one of the main properties in wound dressings, the best results were obtained for A-type zeolite/chitosan films, which presented a brief reduction of this property in relation to zeolite-free chitosan film. On the other hand, the films containing clinoptilolite showed lower water vapor permeation, which may be also explained by the best distribution of the particles into the polymer which also promoted greater thermal resistance.