Acid In Real Samples Research Articles

Manganese Oxide-Doped Graphitic Carbon Nitride-Based 2D Material as Nanozyme for the Colorimetric Sensing of Ascorbic Acid

Ascorbic acid is a key player in the human body, pharmaceutical industry, and food industry. It is involved in many physiological processes, and its deficiency or excess amount is linked to many pathological conditions, which makes it essential to monitor its concentration. In the current work, graphitic carbon nitride (g-C3N4) and manganese oxide-doped graphitic carbon nitride (g-C3N4@MnO2) were synthesized through the pyrolysis process. Various characterization techniques, including spectroscopic, diffraction, thermal, and imaging methods, were employed to analyse the material's structural, compositional, and morphological properties. The surface chemical state of the material through X-ray photoelectron spectroscopy confirmed that manganese was present in its tetravalent state, anchoring with nitrogen in the two-dimensional g-C3N4. The synthesized g-C3N4@MnO2 demonstrated intrinsic peroxidase-like activity visualized through the naked eye by the transformation of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxiTMB and confirmed through a UV-Vis spectrophotometer. The detection of ascorbic acid was performed through the peroxidase inhibitory action of the analyte through a chromogenic substrate, which reduced the oxiTMB to a colorless form. Under the optimized conditions, the sensor system was able to detect the analyte in the linear range of 1 to 80µM with a 0.16μM LOD, 0.53µM LOQ, and an R2 value of 0.9982. The sensor system, along with its sensitivity and linearity, was very selective in the presence of various potential interfering species. The sensor was successfully employed for the sensing of ascorbic acid in real samples with excellent reproducibility. The proposed sensor can be used in diagnosis, pharmaceutical applications, and the food industry.

Aggregation-disaggregation regulated fluorescence resonance energy transfer of perovskite nanocrystals for the detection of ascorbic acid

Fluorescence resonance energy transfer (FRET) from fluorescent nanoparticles to small molecules is an attractive approach for bioanalysis. It remains challenging to reversibly regulate the FRET, let alone use reversible FRET to detect ions or molecules. Here we demonstrate an aggregation/disaggregation strategy for reversible regulation of FRET based on metal–ligand coordination chemistry and redox reactions. An amino-functionalized red fluorescent (∼668 nm) perovskite nanocrystals (PNCs) was prepared as the energy donor. Fe3+ can coordinate with the amino groups on PNCs, resulting in the aggregation of PNCs and enhanced absorption from 600 to 700 nm on the surface of PNCs. Aggregation can reduce the distance between PNCs and Fe3+–amino complexes, as well as restrict rotational and translational diffusion of PNCs or Fe3+–amino complexes, consequently enhancing the FRET between PNCs and Fe3+–amino complexes. Interestingly, reductive ascorbic acid can reduce Fe3+ to Fe2+ in the complexes, leading to a weakening of absorption at 668 nm and dispersion of PNCs, resulting in the disappearance of the FRET process involved in PNCs. Based on the FRET switch, we have realized consecutive quantitative analysis of Fe3+ and ascorbic acid in real samples. We expect that reversible FRET process can be regulated by aggregation-disaggregation instructed by coordination and redox reactions, and that the regulation strategy could significantly expand the application scope of PNCs in fluorescence detection.

Comprehensive determination of fatty acids in real samples without derivatization by DMU-SPME-GC methods

The comprehensive determination of fatty acids without derivatization, including short-chain fatty acids (SCFAs), medium-chain fatty acids (MCFAs) and long-chain fatty acids (LCFAs), is a big challenge but powerful for lipidomics in biology, food, and environment. Herein, the dual mode unity solid-phase microextraction (DMU-SPME) combined with gas chromatography-flame ionization detector (GC-FID) or mass spectrometry (MS) was proposed as a powerful method for the determination of comprehensive free fatty acids in real samples. Under the optimized DMU-SPME conditions, the proposed method has good linearity (R2 ≥ 0.994) and low limits of determination (0.01–0.14 mg/L). In the stability analysis, the intra-day relative standard deviation was 1.39–12.43 %, and the inter-day relative standard deviation was 2.84–10.79 %. The recoveries of selected 10 fatty acids in real samples ranged from 90.18 % to 110.75 %, indicating that the method has good accuracy. Fatty acids ranging from C2 to C22 were detected in real samples by the untargeted determination method of DMU-SPME combined with gas chromatography-mass spectrometry (GC–MS). The DMU-SPME method proposed in this study can be used for lipid metabolism analysis and free fatty acid determination in the fields of biology, food, and environment.

Thermally versatile maleimide-based polymeric thin film for detection and separation of picric acid from polluted areas

2,4,6-Trinitrophenol, commonly known as picric acid, is a powerful explosive that has been used historically in military ammunition. Picric acid is extremely toxic and sensitive to friction and heat; thus, it is prone to accidental detonation at high temperatures. It is critical to detect and separate picric acid from the impacted areas. In the present study, we designed and developed a fluorescent copolymer (P1) for temperature-dependent picric acid detection. The solvatochromic and aggregation-induced emission (AIE) properties of P1 were utilized to detect picric acid at a high temperature of 40 °C (high alert level) by turn-off emission. Additionally, a polymeric thin film (F1) was fabricated by immobilizing P1 onto the surface of quartz slide. Notably, F1 retained its emissive properties across a range of temperatures (both relatively low and high alert levels), facilitated by its AIE characteristics. The portable film, F1, displayed a nanomolar sensitivity toward picric acid, making it suitable for on-site detection in aqueous media (neutral pH). Furthermore, F1 demonstrated efficient separation of picric acid from nitroaromatic explosive mixtures with a separation efficiency of 70 % over four cycles. Importantly, F1 exhibited practical utility in detecting and separating picric acid in real samples, highlighting its potential for environmental monitoring applications.

A new green approach to L-histidine and β-alanine analysis in dietary supplements using rapid and simple contactless conductivity detection integrated with high-resolution glass-microchip electrophoresis.

The analysis of dietary supplements is far less regulated than pharmaceuticals, leading to potential quality issues. Considering their positive effect, many athletes consume supplements containing L-histidine and β-alanine. A new microfluidic method for the determination of L-histidine and β-alanine in dietary supplement formulations has been developed. For the first time, capacitively coupled contactless conductivity detection was employed for the microchip electrophoresis of amino acids in real samples. A linear relationship between detector response and concentration was observed in the range of 10-100µmol L-1 for L-histidine (R2 = 0.9968) and β-alanine (R2 = 0.9954), while achieved limits of detection (3 × S/N ratio) were 4.2µmol L-1 and 5.2µmol L-1, respectively. The accuracy of the method was confirmed using recovery experiments as well as CE-UV-VIS and HPLC-UV-VIS techniques. The developed method allows unambiguous identification of amino acids in native form without chemical derivatization and with the possibility of simultaneous analysis of amino acids with metal cations.

Regulating water decontamination and food safety by a reusable, nano-sized MOF@cotton@chitosan composite through nanomolar detection of the drug nitroxinil and organoarsenic feed additive p-arsanilic acid

MOF@cotton@chitosan composite for nanomolar fluorescence sensing of nitroxinil drug and p-arsanilic acid in real samples is presented.

"Turn-on" fluorescent sensor for oleanolic acid based on o-phenyl-bridged bis-tetraphenylimidazole.

Fluorescent sensors had been extensively applied on sensing various biomolecules effectively, but no fluorescent sensor for oleanolic acid was presented up to now. In this work, the first fluorescent sensor for oleanolic acid was designed and synthesized based on o-phenyl-bridged bis-tetraphenylimidazole (PTPI). PTPI was prepared by bridging two tetraphenylimidazole units and o-phenylenediamine via Schiff-base condensation in yield of 86%. PTPI showed high sensing selectivity for oleanolic acid among 26 biomolecules and ions. The blue fluorescence at 482nm was enhanced by 4.5 times after sensing oleanolic acid in aqueous media. The fluorescence sensing ability of PTPI for oleanolic acid maintained stable in pH=5-9. The detecting limitation was as low as 0.032μM. The detecting mechanism was clarified as 1:1 binding stoichiometry by fluorescence Job's plot, mass spectrometry, 1H nuclear magnetic resonance and fourier transform infrared spectroscopy. The detecting ability of PTPI for oleanolic acid was successfully used for paper test and real samples of grapes and Kuding tea with recoveries in the range of 96.0%-106.0%, indicating the good application potential for on-site detecting oleanolic acid in real samples of fruits and food.

The development, validation, and optimization of a SWAdSV method for the simultaneous determination of epinephrine and uric acid in real samples using a poly(L-cysteine) modified SPCE sensor

This work demonstrates the development, optimization, and method validation of a square-wave adsorption stripping voltammetry (SWAdSV) method for the simultaneous determination of epinephrine (EP) and uric acid (UA) using a poly(L-cysteine) (pLC) film modified screen-printed carbon electrode (pLC-SPCE). The pLC film was deposited by the electropolymerization of L-cysteine (LC). The successful deposition of pLC was confirmed by time-of-flight secondary ion mass spectrometry. A comparison was made between a bare SPCE and a pLC-SPCE for the analysis of EP and UA. In order to improve the electroanalytical performance of the pLC-SPCE sensor, the parameters of the square-wave (SW) technique, such as amplitude, frequency, and potential step, as well as the pH of the 0.1 M PBS solution, the concentration of the LC, the number of cycles for electropolymerization, the deposition potential, and the deposition time, were optimized. Subsequently, the SWAdSV method was validated for the limit of detection (LOD), the limit of quantification (LOQ), the linear concentration range, accuracy, and precision. The method had a very low LOD and LOQ, i.e. 10.0 µg/L and 19.8 µg/L for both analytes, respectively. Two linear concentration ranges were obtained, i.e. from 49.0 µg/L to 326.1 µg/L and from 326.1 µg/L to 887.1 µg/L, for both analytes. The average recoveries and the relative standard deviations for both analytes were in a range from 94.4% to 108.4% (n = 6) and from 2.6% to 11.7% (n = 6), respectively, at the four EP and UA concentration levels tested. In addition, the effect of possible interferents, such as glucose, L-ascorbic acid, K+, Cl–, Ca2+, SO42–, Mg2+, NH4+, C2O42–, and urea on the SW signal of EP and UA, were investigated. However, none of these compounds significantly affected the performance of the electroanalytical method. Finally, the applicability of the pLC-SPCE sensor was successfully demonstrated for the analysis of a pharmaceutical sample (an EP auto–injector) and human urine, proving accurate and precise analysis using the developed sensor.

Electrochemical modification of a carbon paste electrode with poly (1,5‐diaminonaphthalene) and copper‐cobalt nanostructures for the determination of thioctic acid in real samples

AbstractThis study used square‐wave voltammetry and cyclic voltammetry to investigate the electrochemical oxidation of Thioctic Acid (TA) on a Carbon Paste Electrode (CPE) modified with copper‐cobalt nanostructures and poly (1,5‐Diaminonaphthalene). The voltammetric sensor was sensitive to the oxidation of TA. In addition, we optimized the effects of multiple cycles of deposition of Cu‐Co nanostructures, and electro‐polymerization of monomer 1,5‐DAN, scan rate, and pH. The sensor showed good identification capabilities for TA. The linear responses obtained ranged from 0.6 μM to 150 μM with a detection limit of 0.48 μM for the modified CPE. The adsorption process controlled the oxidation of TA. We used the proposed sensor and method to determine TA in real samples.

Selective determination of ellagic acid in aqueous solution using blue-green emissive copper nanoclusters

Development of beneficial sensors to analyze ellagic acid concentrations is of great importance for food safety and human health. Herein, a facile and fast fluorescent probe was carried out for the excellently selective and sensitive measurement of ellagic acid in real samples through histidine protected copper nanoclusters (histidine@Cu NCs) as a nanosensor. This as-developed histidine@Cu NCs were performed through UV–vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and fluorescence lifetime analysis. The TEM image revealed that this nanomaterial had spherical features with the average diameter of 2.5 ± 0.05 nm. The blue-green fluorescence of this Cu NCs was found under the UV light. Meanwhile, the maximum excitation and emission wavelength were located at 387 nm and 488 nm. After addition of ellagic acid, the fluorescence of histidine@Cu NCs was slowly weakened with excellent linear range of 0.5–300 μM and detection limit of 0.077 μM. The fluorescence weakening mechanism of this nanosensor were attributed to the inner filter effect (IFE) and static quenching. Finally, this as-established analysis platform was successfully employed to measure ellagic acid in real samples.

A color-change fluorescence sensor for oleanolic acid based on chiral camphanic decorated bis-cyanostilbene.

Although various fluorescent sensors for biomolecules had been extensively reported, the effective fluorescent sensor was seldom reported for detecting oleanolic acid up to now. This work reports the first color-change fluorescence sensor for oleanolic acid based on a bridging bis-cyanostilbene derivative with chiral camphanic groups (C-BCS). C-BCS possessed the chartreuse fluorescence in aqueous media, which transferred to strong blue fluorescence in the presence of oleanolic acid. This sensing ability of C-BCS for oleanolic acid exhibited the high selectivity among all kinds of biomolecules and ions. The good linearity between the fluorescence intensity and concentration of oleanolic acid was acquired in the range of 0.2 × 10-6 to 8.0 × 10-6M with the detecting limitation of 0.0582μM. The 1:1 binding process was clarified as oleanolic acid located in the opening cavity composed of two bridging cyanostilbene units and two chiral camphanic groups based on multiple hydrogen bonds and hydrophobic interaction. The detecting ability of C-BCS was applied on sensing oleanolic acid in thin-layer chromatography analysis, imprinting experiment, tap water, and tea samples, suggesting the effective on-site sensing abilities of C-BCS for oleanolic acid in real samples and daily life.

Light-enhanced transparent hydrogel for uric acid and glucose detection by four different analytical platforms

The lack of solid-phase media limits the portability of colorimetric sensing platforms. In this study, a series of transparent polyvinyl alcohol (PVA) hydrogels encapsulated antimony tin oxide nanoparticles (ATO NPs) and 3,3′,5,5′-tetramethylbenzidine (TMB) were developed as the solid-phase sensing media for glucose and uric acid. Under the conditions of H2O2 and UV light, the hydrogel presented a multicatalytic ability (photo Fenton-like and peroxidase-like activities), which accelerated the oxidation of TMB, turning the hydrogel from colorless to blue and finally enhancing the detection signal. The plasticity of the hydrogel allowed it to be designed into various shapes (membrane, microsphere etc.) to adapt multiple detection platforms (a liquid/solid-phase UV spectrophotometer, a NanoPhotometer, and smartphone spectroscopy). The hydrogel sensing media exhibited excellent tunability and enhanced the photocatalytic ability. The proposed material was successfully applied to detect glucose and uric acids in real samples by four detection platforms to evaluate its practicability.

Voltammetric folic acid sensor based on nickel ferrite nanoparticles modified-screen printed graphite electrode

In this study, an electrochemical sensor for the quantification of folic acid with voltam­metric detection in physiological conditions was constructed. For this purpose, nickel ferrite (NiFe2O4) nanoparticles were used to modify the surface of a screen-printed graphite electrode (NiFe2O4/SPGE) and applied in the determination of folic acid. The modified electrode displays a strong electrochemical response to folic acid. Folic acid was determined electrochemically using the differential pulse voltammetry (DPV) technique with a detection limit of 0.09±0.001 µM in 0.2–147.0 µM linear range in phosphate buffer solution (PBS) at pH 7.0 with this NiFe2O4/SPGE sensor, which has the best electron transfer rate. Also, the sensitivity of the modified electrode was obtained as 0.1139 µA µM-1. The NiFe2O4/SPGE sensor was successfully applied for the determination of folic acid in real samples.

Voltammetric sensor for determination of kojic acid in real samples using carbon paste electrode modified by [Fe(HL)2Cl2] nano-complex and ionic liquid

A new mononuclear Fe(II) complex with the formula [Fe(HL)2Cl2] (1) (HL= N-(2-hydroxy-1-naphthylidene)-2-methyl aniline) was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), UV–Vis and elemental analysis. The spectroscopy analyses revealed the two Schiff base ligands via oxygen and nitrogen atoms and two chloride atoms create an octahedral geometry. The nano-size of [Fe(HL)2Cl2] complex (2) was synthesized by the sonochemical process. Characterization of nano-complex (2) was carried out via X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-Vis, FT-IR spectroscopy. The nano-complex (2) average size synthesized via the sonochemical method was approximately 52 nm. In this work, a simple sensor based on a carbon paste electrode modified with [Fe(HL)2Cl2] nano-complex and the ionic liquid - IL (1-Butyl-3-methylimidazolium hexafluorophosphate) was developed ([Fe(HL)2Cl2] nano-complex-IL/CPE) for convenient and fast electrochemical detection of kojic acid. The modified electrode considerably improves voltammetric sensitivity toward kojic acid compared to the bare electrode. Experimental conditions influencing the analytical performance of the modified electrode were optimized. Under optimal conditions, the oxidation peak current was proportional to kojic acid concentration in the range from 0.3 to 237.0 μM with a detection limit of 0.09±0.001 μM. The [Fe(HL)2Cl2] nano-complex-IL/CPE sensor was successfully applied for the highly sensitive determination of kojic acid in real samples with satisfactory results.

Enzymes Encapsulated within Alginate Hydrogels: Bioelectrocatalysis and Electrochemiluminescence Applications.

A simple procedure to incorporate enzymes (horseradish peroxidase, HRP, and lactate oxidase, LOx) within alginate hydrogels is reported with electrochemiluminescence (ECL) used to detect the enzymatic reactions with the corresponding substrates. First, HRP and LOx were successfully immobilized into CaCO3 microspheres, followed by the electrostatic layer-by-layer deposition of a nanoshell onto the microspheres, and finally by their dispersion into alginate solution. The as-prepared dispersion was drop cast onto the glassy carbon electrodes and cross-linked by the external and internal gelation methods using Ca2+ cations. The enzymes encapsulated within the alginate hydrogels were characterized using cyclic voltammetry and kinetic studies performed using ECL. The results showed that the enzymatic activity was significantly maintained as a result of the immobilization, with values of the apparent Michaelis-Menten constants estimated as 7.71 ± 0.62 and 8.41 ± 0.43 μM, for HRP and LOx, respectively. The proposed biosensors showed good stability and repeatability with an estimated limit of detection of 5.38 ± 0.05 and 0.50 ± 0.03 μM for hydrogen peroxide and lactic acid, respectively. The as-prepared enzymes encapsulated within the alginate hydrogels showed good stability up to 28 days from their preparation. The sensitivity and selectivity of the enzymes encapsulated within the alginate hydrogels were tested in real matrices (HRP, hydrogen peroxide, in contact lens solution; LOx, lactic acid in artificial sweat) showing the sensitivity of the ECL detection methods for the detection of hydrogen peroxide and lactic acid in real samples.

Sensitive detection of citric acid in real samples based on Nafion/ZnO–CuO nanocomposites modified glassy carbon electrode by electrochemical approach

In this approach, the citric acid (CA) in fruit juices was measured in enzyme-free buffer medium using a GCE (glassy carbon electrode) modified with ZnO/CuO nanocomposites (ZnO/CuO NCs) by DPV (differential pulse voltammetry) and CV (cyclic voltammetry) electrochemical methods respectively. The prepared ZnO/CuO NCs are characterized in detail with XRD (X-ray Diffraction), XPS (X-ray photoelectron spectroscopy), FTIR (Fourier-transform infrared spectroscopy), UV–vis. (Ultraviolet visible spectroscopy), FESEM (Field emission scanning electron microscopy) and EDS (Energy dispersive X-ray spectroscopy) analyses. Both DPV and CV, these techniques were applied with ZnO/CuO NCs/Nafion/GCE to analyze CA in the commercial and natural fruit juices. The current data obtained from electrochemical analysis of CA was plotted against the corresponding concentration of CA and found to distribute on the straight-line in the concentration range of 0.15–1.05 mM of CA, which labeled as a linear dynamic range (LDR) for CA detection. The sensor analytical parameters were calculated by considering the active surface area of GCE (0.0316 cm2) of fabricated electrode over the slope of LDR in both cases (CV and DPV). It was found as 0.4358 μAμM−1cm−2 for DPV and 0.4357 μAμM−1cm−2 for CV respectively. Similarly, the lower limits of detection (DL) applying signal/noise (S/N) ratio 3 are also identical as 21.78 ± 1.09 μM for both electrochemical approaches. The sensor parameters (reproducibility, long-time stability in analyzing and response time) were obtained with good and satisfactory results. Besides this, the proposed sensor was performed trustfully in an analysis of the fruit samples. In this consequence, this electrochemical method with binary mixed metal oxide as sensing substrate to develop a portable sensor might be efficient in the sensor technology.

Simultaneous Determination of Dopamine and Uric Acid in Real Samples Using a Voltammetric Nanosensor Based on Co-MOF, Graphene Oxide, and 1-Methyl-3-butylimidazolium Bromide.

A chemically modified carbon paste electrode, based on a CoMOF-graphene oxide (GO) and an ionic liquid of 1-methyl-3-butylimidazolium bromide (CoMOF-GO/1-M,3-BB/CPE), was fabricated for the simultaneous determination of dopamine (DA) and uric acid (UA). The prepared CoMOF/GO nanocomposite was characterized by field emission-scanning electron microscopy (FE-SEM), the X-ray diffraction (XRD) method, a N2 adsorption-desorption isotherm, and an energy dispersive spectrometer (EDS). The electrochemical sensor clearly illustrated catalytic activity towards the redox reaction of dopamine (DA), which can be authenticated by comparing the increased oxidation peak current with the bare carbon paste electrode. The CoMOF-GO/1-M,3-BB/CPE exhibits a wide linear response for DA in the concentration range of 0.1 to 300.0 µM, with a detection limit of 0.04 µM. The oxidation peaks' potential for DA and uric acid (UA) were separated well in the mixture containing the two compounds. This study demonstrated a simple and effective method for detecting DA and UA in real samples.

Liquid-phase microextraction of ascorbic acid in food and pharmaceutical samples using ferrofluid-based on cobalt ferrite (CoFe2O4) nanoparticles

Quantitation of ascorbic acid is extremely desired in the food, cosmetic, and pharmaceutical samples. In this study, liquid-phase microextraction using ferrofluid (LPME-FF) based on the cobalt ferrite nanoparticles (CoFe2O4) coupled with a green, precise, accurate, and robust spectrofluorometric approach was used for extraction and determination of ascorbic acid. The procedure is based on the reaction between ascorbic acid (AA) and methylene blue (MB) as an inexpensive and readily available fluorescence quenching reagent. The native fluorescence intensity of MB was quenched using ascorbic acid. The CoFe2O4 magnetic nanoparticles were synthesized and confirmed by Fourier transform infrared (FT-IR) spectroscopy, vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDXS). Three parameters of pH, ferrofluid volume, and ultrasonic time were selected as influential factors on the process and optimized by central composite design (CCD). Under optimal conditions, linear range, detection limit, and the relative standard deviation were obtained 0.26–5.70 μM, 0.074 μM and, 2.0 %, respectively. Finally, the proposed method was successfully employed for the quantification of ascorbic acid in real samples of lemon juice, orange juice, and vitamin C tablets.

A novel in-situ strategy for enantiomeric discrimination and selective identification of multicomponent carboxylic acids in foods

Chiral carboxylic acids are ubiquitous in nature and are of pivotal importance in practical applications in the field of food science and pharmaceuticals. Simultaneous enantiomeric analysis of carboxylic acids mixtures is a significant research goal. Herein, we demonstrate a new strategy involving the use of the highly selective chiral derivatizing agent (R)-2-amino-1,1,1-trifluoropropane ((R)-TFPA) for the enantiomeric discrimination and selective identification of carboxylic acids in mixtures, even structurally similar drugs. The key success of this sensing approach lies in the distinguishable 19F NMR signals of diastereoisomers formed via derivatization of the substrates by (R)-TFPA. The utility of this approach was demonstrated by simultaneously differentiating 20 chiral carboxylic acids in a complicated mixture with accurate determination of the enantiomeric excess (ee). Most importantly, our approach can be applied to food analysis, where the diverse carboxylic acids in real samples without separation were unambiguously identified, such as vinegar, yogurt, and grape.

A sensitive and simple electrochemical technique for detecting ascorbic acid content in pharmaceutical and biological compounds

In the current study, a glassy carbon electrode (GCE) modified with graphene-CoS2 nanocomposite was investigated for electrochemical sensing of ascorbic acid. The electrochemical performance of the modified electrode was examined using differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and chronoamperometry (CHA) techniques. The electrochemical behavior of ascorbic acid at the graphene-CoS2/GCE displayed a higher oxidation current and lower oxidation potential than bare GCE. Under the optimal experimental conditions, the sensor presented a good linear response between the current and the ascorbic acid concentration range of 0.15–245.0 μM, with a low detection limit of 0.05 μM. Finally, the graphene-CoS2 nanocomposite-modified GCE was applied for the determination of ascorbic acid in real samples and displayed excellent recoveries.