Efficient Electrochemical Sensor Research Articles

Directionally Exfoliated Ni/Co Hydroxide-Organic Framework Nanosheets for Enhanced Wearable Glucose Sensing.

We report two-dimensional (2D) Ni/Co-based metal hydroxide-organic framework nanosheets (Ni/Co-MHOF NSs) for the construction of an efficient electrochemical nonenzymatic glucose sensor. The nanosheet architecture maximizes the exposure of coordinatively unsaturated metal sites, which enables a largely improved electrocatalytic performance toward the glucose oxidation reaction. The as-designed nonenzymatic sensor exhibits a high sensitivity of 235.71 μA·mM-1·cm-2 and a wide linear range of 1-3000 μM. The sensor presents excellent selectivity against several potential interferences and a short response time of 3.0 s. Of interest, a high-performance flexible sensor is developed by depositing the Ni/Co-MHOF NSs on screen-printed electrodes, which reveal decent bending stability. The designed glucose sensor patch can attach to the human body and realize noninvasive glucose monitoring in human sweat. This work may shed light on the application of novel MHOFs in the field of wearable electrochemical sensing.

Ciprofloxacin Electrochemical Sensor Using Copper-Iron Mixed Metal Oxides Nanoparticles/Reduced Graphene Oxide Composite.

The harmful effects of antibiotic proliferation on the environment and its persistent nature are urgent global problems. Ciprofloxacin (CIP) is a fluoroquinolone-class antibiotic agent used widely to treat pathogen-related diseases in humans and animals. Its excretion into surface water causes antibiotic resistance in microbes, resulting in difficult-to-treat or untreatable infectious diseases. This study developed a simple and efficient electrochemical sensor to detect CIP. Hydrothermal chemistry was utilized to synthesize an electrophotocatalytic composite of copper-iron mixed metal oxides (CIMMO) on reduced graphene oxide (rGO) (CIMMO/rGO). The composite was employed in an electrochemical sensor and exhibited outstanding performance in detecting CIP. The sensor was operated in differential pulse voltammetry (DPV) mode under light source illumination. The sensor yielded a linear response in the concentration range of 0.75 × 10-9-1.0 × 10-7 mol L-1 CIP and showed a limit of detection (LOD) of 4.74 × 10-10 mol L-1. The excellent sensing performance of the composite is attributable to the synergic effects between CIMMO nanoparticles and rGO, which facilitate photoinduced electron-hole separation and assist in the indirect electrochemical reactions/interactions with CIP.

Development of an efficient electrochemical sensor based on CuAl-LDH using an electrostatic repulsion approach for the selective determination of dopamine in the presence of uric acid and ascorbic acid species

This study provides a unique electrochemical sensor that exhibits both excellent sensitivity and selectivity, while also being environmentally friendly. The CuAl-LDH/GCE sensor, proposed as the recommended sensor, was synthesized using a straightforward one-step co-precipitation procedure. It was first used to measure dopamine levels using differential pulse voltammetry. At the ideal pH level of 8, dopamine has a positive charge, but ascorbic acid and uric acid have a negative charge. LDH, on the other hand, carries a negative charge and exhibits high electrostatic attraction towards dopamine, but is electrostatically repelled by negatively charged ascorbic acid and uric acid. Hence, CuAl-LDH/GCE has the potential to specifically ascertain the existence of dopamine in the presence of these particular species. The examination of the composition and morphology of CuAl-LDH was conducted using various analytical techniques, including scanner electron microscopy (FESEM), transmission electron microscope (TEM), element mapping (MAP), Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDX), Brunauer Emmett Teller (BET), X-ray photoelectron diffraction (XRD), and Raman techniques. Under ideal circumstances, the calibration graph of dopamine was generated using differential pulse voltammetry. A linear range of 4.194–1151.54 μM was achieved for dopamine, with a limit of detection of 0.33 μM. The findings of the study indicate that the sensor created for dopamine determination has exceptional stability, repeatability, and reproducibility. The sensor that was presented was effectively used for the measurement of dopamine in both pharmaceutical ampoules and human plasma samples.

An R-type hexagonal ferrite nanoparticles-based electrochemical sensor for Levofloxacin detection in pharmaceutical and clinical specimens

The usage of Levofloxacin (LEV) has increased in recent years for the treatment of bacterial infections in both human and veterinary fields. In this context, there has been a significant demand for the development of a highly sensitive and cost-effective approach to LEV quantification. In this study, R-type hexagonal ferrite nanoparticles (SrSn2Fe4O11-NPs) were prepared by an auto-ignition methodology and various analytical techniques were used for the materiaĺs characterization, including X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Brunauer Emmett and Teller (BET) analysis, dynamic light scattering (DLS), and vibrating sample magnetometer (VSM) analysis. The characterization confirmed that the prepared material has a crystalline structure single-phase with a crystalline size of 35.02 nm. The R-type hexagonal ferrite nanoparticles were immobilized on a glassy carbon electrode (GCE) by a simple drop-casting approach to developing an efficient electrochemical sensor (SrSn2Fe4O11-NPs/GCE) for sensitive and selective LEV detection through an extended concentration range (0.06 × 10−6 to 170 × 10−6 M) and a low detection limit of (41.5nM). The developed sensor was applied successfully to quantitatively determine LEV in clinical samples and pharmaceutical preparations with excellent recoveries from 95.2 to 102.5 %.

Date Leaves-Derived Submicron/Nano Carbon-Modified Glassy Carbon Electrode for Highly Sensitive and Simultaneous Detection of 1-Naphthol and 2-Naphthol

This study introduces a novel approach for synthesizing biomass derived carbon from date leaves waste, employing a straightforward combination of pyrolysis and ball milling processes. This process yields active carbon in submicron and nanometer sizes, characterized by detailed surface, structural, and compositional analyses, confirming suitability of the materials for electrochemical applications. Utilizing this synthesized carbon, we have developed a modified glassy carbon electrode (DLSNC/GCE) for the highly-sensitive and simultaneous detection of phenolic contaminants, specifically 1-naphthol (1-NP) and 2-naphthol (2-NP), which are crucial for environmental monitoring. The study describes two innovative fabrication methods for electrochemical sensors. The first method controls the direct oxidation of 1-NP and 2-NP, while the second method exploits redox peaks associated with quinone formation from dihydroxy naphthalene, revealing superior analytical performance for the simultaneous detection of the analytes. The electrochemical sensor demonstrated exceptional sensitivity and selectivity towards 1-NP and 2-NP. This revolution emphasizes the potential of using date leaves-derived carbon materials in constructing low-cost, efficient electrochemical sensors for environmental monitoring and electrochemical applications.

Streamlined synthesis of superstructure Ni-benzimidazole MOFs: Glucose electrochemical analysis

The design and synthesis of efficient electrochemical sensors are crucial transformation technologies in electrochemistry. We successfully synthesize a three-dimensional Ni-metal–organic framework (MOF) nanostructured material with a superior architecture using benzimidazole and nickel nitrate as precursors at room temperature which is being applied in glucose electrochemical sensors. The reaction mechanism of M-6 during glucose detection is thoroughly studied using various characterization techniques, such as in situ Raman spectroscopy, in situ ultraviolet–visible spectrophotometry, synchrotron radiography, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The research findings demonstrate that the M-6 material exhibits high sensitivity for glucose detection, with a sensitivity of 2199.88 mA M−1 cm−2. This study provides an important reference for designing more efficient electrochemical reaction systems and optimizing material performance. Furthermore, the superstructural design offers new ideas and possibilities for the development and application of similar materials.

Electrochemical sensor based on PEDOT/CNTs-graphene oxide for simultaneous determination of hazardous hydroquinone, catechol, and nitrite in real water samples

Hydroquinone (HQ), catechol (CC) and nitrite (NT) are considered aquatic environmental pollutants. They are highly toxic, harm humans’ health, and damage the environment. Thus, in the present work we introduce a simple and efficient electrochemical sensor for determination of HQ, CC, and NT simultaneously in wastewater sample. The sensor is fabricated by modifying the surface of a glassy carbon electrode (GCE) by two successive thin films from poly(3,4-ethylenedioxythiophene) (PEDOT) and a mixture of carbon nanotubes-graphene oxide (CNT-GRO). Under optimized conditions the HQ, CC, and NT are successfully detected simultaneously in wastewater sample with changing their concentrations in the ranges (0.04 → 100 µM), (0.01 → 100 µM) and (0.05 → 120 µM), the detection limits are 8.5 nM, 3.8 nM and 6.1 nM, respectively. Good potential peak separations: 117 mV and 585 mV are obtained between the HQ-CC, and CC-NT. The sensor has an excellent catalytic capability toward the oxidation of HQ, CC, and NT due to good synergism between its composite components: PEDOT, GRO and CNTs. The features of the sensor are large active surface area, good electrical conductivity, perfect storage stability, good reproducibility, anti-interference capability and accepted recovery rate for HQ, CC, and NT determination in wastewater sample.

An electrochemical voltammetric response of Hg2+ and Pb2+ ions using polyaniline-benzothiazole composite modified GCE electrode: Synthesis, characterization and quantum chemical calculation

An efficient electrochemical sensor based on polyaniline-benzothiazole [(3,5-bis (benzo[d]thiazol-2-yl)-[1,1–biphenyl]-4-ol)] (PAni-BEN) composite was designed and synthesized in this study, and it was employed as an electrochemical sensor to detect Hg2+ and Pb2+ ions with good selectivity and sensitivity. Fourier transform-infrared spectroscopy, UV–Vis spectroscopy, scanning electron microscopy, and energy dispersive X-ray analysis spectroscopy were employed to examine the morphology and structure of the produced composite. The electrochemical characteristics of the electrode modifiers were evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Also, they were employed to perform both individual and simultaneous sensing studies of various metal ions using the differential pulse voltammetry technique (DPV) in a different supporting electrolyte (acetate buffer (pH 5), phosphate buffer (pH 7), and 0.1 M HCl) mediums. The PAni-BEN composite modified GCE sensor shows remarkable selectivity and sensitivity towards Hg2+ and Pb2+ ions over the other heavy metal ions in 1 to 24.84 µM, respectively. The limits of detection (S/N = 3) were 1 nM and 4.6 nM for Hg2+ and Pb2+ ions. Density Functional Theory (DFT) was used in the present study to accomplish the adsorption mechanism of the suggested sensors. The DFT calculation demonstrated that the PAni-BEN composite was formed with a lower band gap energy than BEN and DD PAni. These findings showed that the suggested sensor (PAni-BEN), which may used to detect Hg2+ and Pb2+ ions, had the lowest detection limit in the acetate buffer medium compared to the proposed electrolyte medium.

A new thiacalix[4]arene-based metal-organic framework as an efficient electrochemical sensor for trace detection of Cd2+ and Pb2+

Heavy metal ions (HMIs) can lead to serious harm to human health and ecological environment. Thus, developing an efficient detection method for HMIs is extremely necessary. Herein, a new thiacalix[4]arene-based metal–organic framework (MOF) [Co2(L1)(TPA)2]·DMA·3CH3OH·H2O (Co-LTPA) (L1 = thiacalix[4]arene-based ligand and H2TPA = terephthalic acid) was successfully synthesized. The electrochemical detection platform (Co-LTPA/GCE) was acquired, and Co-LTPA/GCE featured ultrasensitive detection of HMIs with greatly low limits of detection (LODs) of 0.119 nM for Cd2+ and 0.279 nM for Pb2+ as well as wide linear ranges of 0.08–5.8 μM for Cd2+ and 0.01–6.0 μM for Pb2+. More importantly, the Co-LTPA/GCE sensor was employed to detect foods (milk, honey and orange juice) and water samples (tap water, lake water and drinking water) with satisfactory recoveries, proving the sensor reliability in practical applications. This work provided an example that the functional electrochemical Co-LTPA/GCE sensor was employed for Cd2+ and Pb2+ detection.

Highly efficient electrochemical detection of H2O2 utilizing an innovative copper porphyrinic nanosheet decorated bismuth metal-organic framework modified electrode.

The ability to detect hydrogen peroxide is important due to the presence in biological systems. Researchers are highly interested in developing efficient electrochemical hydrogen peroxide sensors. Metal-organic frameworks (MOFs) with their composites, an emerging class of porous materials, are ideal candidates for heterogeneous catalysts because of their versatile functionalities. Using a facile solvothermal reaction, we fabricated a 2D Cu-TCPP nanosheet uniformly grown on a 3D Bi-MOF. The process takes advantage of the large surface area and pore volume of the Bi-MOF while maintaining the crystallinity of Bi-BTC when Cu-TCPP is added to the surface. The sensor was fabricated by depositing the Bi-BTC-Cu-TCPP nanocomposites on a glassy carbon electrode to conduct electrochemical measurements such as cyclic voltammetry and electrochemical impedance spectroscopy. Finally, differential pulse voltammetry was utilized to investigate the effect of hydrogen peroxide on the electrochemical activity of Bi-BTC-Cu-TCPP deposited on a glassy carbon electrode. This electrode showed high electrochemical performance activity for the reduction of hydrogen peroxide. The sensor showed a linear response to H2O2 in the 10-120 μM concentration range, with a detection limit of 0.20 μM. The sensor was also stable and selective for H2O2 in the presence of other interfering species. This work demonstrates the potential of nanocomposite-based electrochemical sensors for sensitive and selective detection of H2O2. Besides, the modified electrode has many advantages, including remarkable catalytic activity, long-term stability, good reproducibility, and a good signal response during H2O2 reduction.

Cu5Zn8@SiO2/NC derived from Cu/ZIF-8 as an efficient electrochemical sensor for environmental pollutant detection in water bodies

Sensitive detection of toxic substances in drinking water is always a difficult problem in electrochemical applications.

An efficient electrochemical sensor based on the Ce-MOF/g-C3N5 composite for the detection of nitrofurazone.

The Ce-MOF/g-C3N5 composite was first constructed using a simple reflux method in an oil bath. Herein, we report that the electrochemical sensor fabricated based on this composite exhibits high performance in the detection of nitrofurazone. Interestingly, this sensor exhibits an extra-wide linear range of detection composed of two line segments (7-100 μM and 100-2913 μM), as well as a low detection limit (LOD) of 6.15 μM (S/N = 3) under optimal experimental conditions. Additionally, the sensor demonstrates exceptional selectivity, reproducibility and stability. More importantly, the proposed electrochemical sensor can effectively monitor nitrofurazone in real samples such as urea and tap water, and obtain ideal recoveries. The sensor has such excellent performance because of the synergistic effect of the two components in the Ce-MOF/g-C3N5 composite. Compared with Ce-MOF, the introduction of g-C3N5 effectively not only enhances the conductivity of Ce-MOF/g-C3N5 but also exposes more active sites, which is conducive to increasing the electrocatalytic activity to reduce nitrofurazone. This research contributes new scientific research ideas for fabricating ideal electrochemical sensors based on g-C3N5 and MOFs.

A novel Ga2O3-doped ZnO decorated SWCNT nanocomposite based amperometric sensor for efficient detection of dopamine in real samples

Our current research focuses on developing an efficient electrochemical Dopamine sensor for diagnosing neurological disorders related to abnormal Dopamine levels. We utilized a Ga2O3-doped ZnO decorated SWCNT (Ga2O3·ZnO@SWCNT) nanocomposite to modify a glassy carbon electrode. The structure and morphology of the Ga2O3·ZnO@SWCNT nanocomposite was examined utilizing a variety of approaches to ensure of their appropriateness as the sensing nanomaterial. The sensor effectively detects Dopamine within a wide range (1.0–2056 μM) in neutral phosphate buffer solution, exhibiting high sensitivity (0.2536 μAμM−1cm−2) and a practical detection limit (0.052 μM). It accurately quantifies Dopamine in human blood serum and commercial dopamine injection samples, displaying excellent reproducibility, repeatability, and stability. This proposed Dopamine sensor proves to be a reliable tool for Dopamine determination.

Synergistically Enhanced Electrochemical Sensing of Bisphenol A in Real Water Samples at Carbon Nanotubes/β‐Cyclodextrin/Gold Nanoparticles Composite

AbstractMonitoring of bisphenol A (BPHA) is required as its release with byproducts into the aquatic environment every year, causes pollution and toxicity which affects the human health. An efficient electrochemical sensor is therefore needed to determine BPHA in water from natural resources. To construct the sensor, a thin layer of carbon nanotubes (CNTs) is applied to the surface of glassy carbon (GC) then β‐CD and Aunano are sequentially electrodeposited. The performance of the sensor is optimized and shows excellent catalytic effect in wide concentration range 7 nM to 700 μM with low detection limit of 5.02 nM compared to other cited modified electrodes. Each of the sensor constituents share in the enhancement of its performance; Aunano has intrinsic surface electroactivity, β‐CD “host” allows for BPHA “guest” surface accumulation, and CNTs with large conductive surface area realize homogeneous distribution of the other two components. The advantages of the BPHA electrochemical sensor are simple to prepare, timesaving, and shows good sensitivity, stability, selectivity in presence of interfering ions and compounds, it is suitable for use with portable simple equipment for in situ measurements. Furthermore, the application of the sensor in wastewater samples shows good recovery of BPHA.

Nitrogen doped biomass derived carbon and BiVO4 composite for simultaneous detection of furazolidone and chloramphenicol

An efficient electrochemical sensor based on nitrogen functionalized biochar (N-BC) and BiVO4 hybrid nanocomposites was prepared, and used for simultaneous detection of furazolidone (FZD) and chloramphenicol (CAP) with highly sensitive and selective in food sample. The N-BC was obtained by acid activation method which using biomass waste (rice halls) as the raw and processed material and urea as the nitrogen source, which was further mixed with BiVO4 to synthesized N-BC/BiVO4 composite. The surface morphology and structured properties were characterized by Scanning electron microscopic (SEM), Nitrogen (N2) adsorption/desorption isotherms, X-ray powder diffraction (XRD) patterns, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry (CV) and electrochemical impedance studies of N-BC/BiVO4 film on GCE showed that electron transfer rate in [Fe (CN)6]3−/4− solution was rapider than bare GCE, N-BC/GCE and BiVO4/GCE. The sensor was successfully used for the detection of FZD and CAP with wide linear ranges of 0.1–1600 μM for FZD and 0.1–3200 μM for CAP, low limit of detection of 0.053 μM for FZD and 0.087 μM for CAP (S/N = 3), respectively. In addition, the proposed sensor has shown good anti-interference ability, reproducibility and stability, and obtained satisfactory results for respective or simultaneous detection of FZD and CAP in milk sample.

Development of an efficient electrochemical sensor based on MoS2 nanosheets and ionic liquid modified carbon paste electrode for determination of ascorbic acid in the presence of vitamin B6

Development of an efficient electrochemical sensor based on MoS2 nanosheets and ionic liquid modified carbon paste electrode for determination of ascorbic acid in the presence of vitamin B6

Ruthenium nanoparticles encrusted with nitrogen & sulphur magnetic quantum dots as an efficient electrochemical sensor for simultaneous determination of itraconazole and terbinafine; a dual regimen for black fungus: Magnetic solid phase micro-extraction for urine and plasma analysis

After COVID-19 pandemic, Mucormycosis (black fungus) spreads as one of its related complications, due to the decrease in immunity system after administration of COVID-19 treatment drugs. A combination therapy of Itraconazole (ITR) and Terbinafine (TEB) was proved to be effective for treatment of black fungus. A novel electrochemical sensor was designed for estimation of ITR & TEB simultaneously by square wave voltammetric (SWV) technique. The sensor was fabricated using N&S-codoped magnetic quantum dots (N,S-MQDs) and ruthenium nanoparticles (Ru NPs). The fabricated sensor was characterized by cyclic voltammetry (CV), scanning electron microscope (SEM), powder X ray diffraction (pXRD), Fourier transform-Infrared (FT-IR), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). Full optimization study for various experimental and instrumental parameters, in addition to method validation following International conference on Harmonization (ICH) guidelines was achieved. A good linearity in the range of 0.5–30 μg mL−1 with limit of detection (LOD) 0.24 and 0.19 μg mL−1 for ITR and TEB, respectively were obtained. The sensor was applied for analysis of ITR and TEB simultaneously in human plasma and urine samples without any interferences by applying dispersive magnetic solid phase micro-extraction (dMSPE) technique, where excellent recovery results exceeding 95 % were achieved.

Nickel-cobaltite-doped carbon xerogel based voltammetric sensor for olanzapine: Electrochemical characterization and applications

A simple, novel, and efficient electrochemical sensor was developed for the quantification of Olanzapine (OLA) in its pure form, pharmaceutical formulations, serum, and urine samples. The sensor was based on the modification of a glassy carbon electrode (GCE) with nickel cobaltite/carbon xerogel nanocomposite (NiCo2O4/CX). FESEM, X-ray diffraction (XRD), and N2 adsorption/desorption isotherms were used to characterize the prepared nanocomposite. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the electrochemical performance of the modified electrode toward electrocatalytic oxidation of OLA. The data obtained showed that the anodic peak of OLA at NiCo2O4/CX/GCE remarkably increased in comparison with bare GCE. The influence of different parameters including nanocomposite amount, accumulation time, scan rate, and pH was studied. Under optimized conditions, the lower limit of detection (LOD) for the DPV oxidation peak current was 4.0 nM, with a linear range of 0.04 µM–212.4 µM. The modified GCE showed good selectivity, excellent repeatability and reproducibility, and high sensitivity. Additionally, NiCo2O4/CX/GCE-based OLA sensor has been successfully utilized for OLA assay in its pharmaceutical formulations, human urine, and serum samples. The developed OLA sensor exhibited good recovery results that agreed with the standard method.

Fabrication and Comprehensive Comparison of the Performance of Chemically Modified GCE and SPCE for the Simultaneous Determination of Uric Acid and Vanillylmandelic Acid

Uric acid (UA) and Vanillylmandelic acid (VMA) are two important biomarkers that can significantly account for certain pathological conditions in our body. A novel and efficient electrochemical sensor has been fabricated for the simultaneous determination of UA and VMA based on screen printed carbon electrodes chemically modified with a nanocomposite of reduced graphene oxide and poly(L-threonine) conducting polymer (rGO- p(Thr)/SPCE). The fabricated sensor has been well characterized and various experimental conditions were optimized to avail maximum performance of the sensor towards the determination of UA and VMA. In addition, the sensor's performance was rationally analysed and compared with the same sensor fabricated on a conventional glassy carbon electrode (rGO- p(Thr)/GCE) to understand how the change in electrode substrate affects the sensor's performance. Studies revealed that although both of the sensors can be successfully applied for the simultaneous determination of UA and VMA over wide linear ranges with lower detection limits, better sensitivity was acquired when rGO- p(Thr)/GCE was used. On the other hand, modification of SPCE provided greater reduction in electrooxidation potential of UA and VMA than GCE. Electroactive surface area changes in GCE and SPCE upon modification showed different trends, whereas study on mechanistic aspects of electrooxidation exhibited similar results. Since SPCE is more of practical relevance considering the ease of miniaturization and applicability in on-site analysis, studies on interference by probable coexisting species and applicability of the sensor in synthetic physiological fluids were also successfully carried out on rGO-p(Thr)/SPCE.

Electrochemical sensor for simultaneous determination of antiviral favipiravir drug, paracetamol and vitamin C based on host–guest inclusion complex of β-CD/CNTs nanocomposite

Favipiravir (FVI) is extensively used as an effective medication against several diverse infectious RNA viruses. It is widely administered as an anti-influenza drug. Combination therapy formed from FVI, paracetamol (PAR) and vitamin C (VC) is needed for treating patients diseased by RNA viruses. Thus, an efficient electrochemical sensor is developed for detecting FVI in human serum samples. The sensor is fabricated by casting a thin layer of carbon nanotubes (CNTs) over a glassy carbon (GC) electrode surface followed by electrodeposition of another layer of β-cyclodextrin (β-CD). Under optimized conditions, the sensor shows excellent catalytic effect for FVI, PAR and VC oxidation in the concentration ranges (0.08 µM → 80 µM), (0.08 µM → 50 µM) and (0.8 µM → 80 µM) with low detection limits of 0.011 μM, 0.042 μM and 0.21 μM, respectively. The combined effect of host–guest interaction ability of β-CD for the drugs, and a large conductive surface area of CNTs improves the sensing performance of the electrode. The sensor exhibits stable response over 4 weeks, good reproducibility, and insignificant interference from common species present in serum samples. The reliability of using the sensor in serum samples shows good recovery of FVI, PAR and VC.