Amperometric Measurements Research Articles

LIG-Based High-Sensitivity Multiplexed Sensing System for Simultaneous Monitoring of Metabolites and Electrolytes.

With improvements in medical environments and the widespread use of smartphones, interest in wearable biosensors for continuous body monitoring is growing. We developed a wearable multiplexed bio-sensing system that non-invasively monitors body fluids and integrates with a smartphone application. The system includes sensors, readout circuits, and a microcontroller unit (MCU) for signal processing and wireless communication. Potentiometric and amperometric measurement methods were used, with calibration capabilities added to ensure accurate readings of analyte concentrations and temperature. Laser-induced graphene (LIG)-based sensors for glucose, lactate, Na+, K+, and temperature were developed for fast, cost-effective production. The LIG electrode's 3D porous structure provided an active surface area 16 times larger than its apparent area, resulting in enhanced sensor performance. The glucose and lactate sensors exhibited high sensitivity (168.15 and 872.08 μAmM-1cm-2, respectively) and low detection limits (0.191 and 0.167 μM, respectively). The Na+ and K+ sensors demonstrated sensitivities of 65.26 and 62.19 mVdec-1, respectively, in a concentration range of 0.01-100 mM. Temperature sensors showed an average rate of resistance change per °C of 0.25%/°C, within a temperature range of 20-40 °C, providing accurate body temperature monitoring.

Scalable enzymatic lactate sensor for continuous monitoring in interstitial fluid

Abstract Elevated lactate levels have been shown to be an indicator of poor outcome in cardiovascular patients [1]. Moreover, continuous monitoring of lactate may be more clinically valuable than the absolute value of lactate for risk stratification [2]. A promising approach involves the implementation of a lactate monitoring system inspired by advanced continuous glucose monitoring [3] to provide real-time measurements of lactate in interstitial fluid (ISF) based on miniaturized lactate sensors with submillimeter dimensions. The proposed amperometric lactate sensor employs Pt electrodes (WE = 0.785 mm²) on which the enzyme lactate oxidase is immobilized to selectively detect lactate. The sensing mechanism, shown in Fig. 1a, is based on the conversion of lactate to hydrogen peroxide, which then undergoes oxidation at the electrode surface, generating a current proportional to the concentration of lactate. Amperometric measurements are performed with an applied potential of 0.5 V, a sample volume of 2 µL and a flow rate of 1 µL/min, respecting real-life conditions. The response of the sensor towards lactate is shown in Fig. 1c, demonstrating excellent reversibility, long-term stability over 8 hours and negligible cross sensitivity to glucose (G), ascorbic acid (AA) and uric acid (UA). In addition, the sensor linear range can be extended by 10x by incorporating an outer Nafion layer, acting as a diffusion-limiter. As shown in Fig. 1d, by adjusting the thickness of Nafion layer, the linear range increases up to 20 mM lactate, as per ICU specifications. The physiological challenges associated with ISF extraction prompted us to develop a minimally invasive, submillimeter-sized sensor for direct placement inside the body. To address the most critical step of miniaturization, we have successfully fabricated a three-electrode platform on a Si ribbon measuring 300x1500 µm² and a thickness of 100 µm (Fig. 2a). The sensor is also drastically scaled down, with smallest design having a total sensing area of 200x500 µm² (WE = 0.026 mm², Fig. 2b). Its response to lactate is displayed in Fig. 2c, confirming a reliable functionality. Fig. 2d presents the calibration curves obtained from sensors with different sizes, indicating that the reduction in size does not affect the sensitivity. The developed lactate sensor demonstrates excellent performance: high sensitivity, excellent reversibility, and high stability. In addition, the linear range of the sensor is tunable by integrating an outer Nafion membrane. Finally, we demonstrate the successful fabrication and characterization of submillimeter-sized sensors, opening up their potential for minimally invasive in-vivo measurements.Working principle and characterizationCharacterization miniaturized sensors

3D printed oxygen gas sensor with a Pt-nanoparticles decorated N-doped carbon catalyst and an amine-polymer composited ionic liquid gel electrolyte

A 3D-printed electrochemical oxygen gas sensor was developed using a Pt nanoparticle-decorated N-doped carbon (PtNC) catalyst and an ionic liquid gel electrolyte incorporated with polyethyleneimine. At first, N-doped carbon particles were synthesized hydrothermally, followed by the decoration of a tiny amount of Pt nanoparticles using a microwave reactor. The working electrode was printed with a composite of high-impact polystyrene (HIPs), graphite powder (Gr), and a PtNC catalyst (HIPs/Gr/PtNC), then counter and reference electrodes were separately printed without the PtNC catalyst. The sensing materials were characterized using various analytical methods, including SEM, XPS, Raman, ICP-AES, CV, and EIS. Prior to detecting oxygen gas, the 3D sensor surface was pretreated with potential cycling in an acidic solution. Additionally, a composite gel electrolyte was prepared by incorporating polyethyleneimine into an ionic liquid, which was then coated onto the sensor surface to enhance sensitivity and ensure long-term stability. The analytical parameters using the final sensor were optimized in terms of Pt contents, 3D-printing polymer type, and ionic liquid gel concentration. The amperometric measurements demonstrated a wide dynamic range from 0.1 % to 100 % with the detection limit of 0.13 ± 0.05 % at a 90 % response time of 3.6 ± 0.4 s. To validate the reliability of the proposed sensor, the measurement of O2 content was performed for room air and standard oxygen gas, revealing reliable and stable results for six months.

Schottky Interface Enabled Electrospun Rhodium Oxide Doped Gold for Both pH Sensing and Glucose Measurements in Neutral Buffer and Human Serum.

This study has focused on adjusting sensing environment from basic to neutral pH and improve sensing performance by doping electrodeposited gold (Au) with metal oxide for nonenzymatic glucose measurements in forming a Schottky interface for superior glucose sensing with detailed analysis for the sensing mechanism. The prepared sensor also holds the ability to measure pH with the identical electrospun metal oxide-electrodeposited Au, which composed a dual sensor (glucose and pH sensor) through applying chronoamperometry and open circuit potential methods. The rhodium oxide nanocoral structure was fabricated with an electrospinning precursor solution, followed by a calcination process, and it was mixed with electrodeposited nanocoral gold to form the Schottky interface by constructing a p-n type heterogeneous junction for improved sensitivity in glucose detection. The prepared materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrometry (XPS), etc. The prepared materials were used for both pH responsive testing and amperometric glucose measurements. The rhodium oxide nanocoral doped gold demonstrated a sensitivity of 3.52 μA mM-1 cm-2 and limit of detection of 20 μM with linear range up to 3 mM glucose concentration compared to solely electrodeposited gold for a sensitivity of 0.46 μA mM-1 cm-2 and a limit of detection of 450 μM. The Mott-Schottky method was used for the analysis of an electron transfer process from noble metal to metal oxide to electrolyte in demonstrating the improved sensitivity at neutral pH for glucose measurements due to the Schottky barrier adjustment mechanism at an applied flat band potential of 0.3 V. This work opens a new venue in illustrating the metal oxide/metal materials in the glucose neutral response mechanism. In the end, human serum samples were tested against current commercial glucose meter to certify the accuracy of the proposed sensor.

Electroanalysis of bromate at riboflavin impregnated Ketjen black porous electrode via an autocatalytic cycle with finite length diffusion

The emergence of elevated concentrations of bromate, classified as a 2B type carcinogen, in drinking water following the treatment of water supplies with ozonation and other oxidation methods has underscored the importance of developing methods for reliable and rapid screening of drinking water. In this work, we report the use of electro activated riboflavin (RF) impregnated Ketjen black (KB) modified screen-printed electrode (elRF@KB-SPE) for the determination of bromate. The sensing surfaces were subjected to morphological and structural characterization using scanning electron microscopy and Raman spectroscopy. These analyses confirmed the successful modification of the electrode with an extended elRF@KB porous coating. Based on cyclic voltammetry (CV) and electrochemical impedance spectroscopy measurements, the response of elRF@KB-SPE towards bromate can be described through a dual mechanism involving i) an autocatalytic chemical/electrochemical process that predominantly occurs in the finite length pores of KB, and ii) an RF-mediated electrocatalytic process. Notably, the data demonstrated that the advanced electrocatalytic properties of the otherwise electrocatalytically inactive absorbed RF molecules are endowed after a simple electro activation process (three CV scans). Amperometric measurements at −0.05 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of bromates over the concentration range 0.50−18.0 μM, achieving a limit of detection (3σ/slope) of 0.04 μM. The interference effect of various electroactive species was investigated demonstrating that elRF@KB-SPE is highly selective to bromate. The analytical utility of the method was evaluated in spiked tap water samples. Recoveries were 91.2 − 106.4 %.

Size-controlled synthesis of cobalt phosphide (Co2P) nanoparticles and their application in non-enzymatic glucose sensors via a carbon fiber/Co2P composite

In this study, we synthesized Co2P nanoparticles using a solid-state phosphorization method and evaluated the electrocatalytic response to glucose oxidation reaction (GORs). The influence of synthesis conditions on the particle size, morphology of Co2P species and formation of byproducts is discussed. A lower molar ratio of the phosphorus precursor leads to a decrease in the generation of byproducts. In addition, the calcination temperature and time greatly influence the purity level of the Co2P species and its particle size. Thus, we obtained three pure Co2P nanoparticles with different sizes and morphologies. Significant differences in their electrocatalytic activity against the GOR are observed depending on the size of the particles, being the smaller ones the most efficient. Based on Tafel analysis, a higher catalytic activity was observed for the carbon fibre (CF)/Co2P composite compared to Co2P, which presented a greater onset potential and low response in current density. Tafel slopes close to 120 mV/dec were obtained for both materials, indicating that the mechanism is independent of the type of Co2P-based material used. Finally, the performance of the GCE/CF/Co2P sensor was demonstrated by amperometric measurements, with a sensitivity of 409 µAmM-1cm-2, a linear range between 39.4 µM and 150 µM, and a detection limit of 0.97 µM, analytical characteristics better than those obtained for other cobalt phosphide-based sensors reported in the literature. In addition, the GCE/CF/Co2P sensor shows excellent selectivity and demonstrated to be competitive compared to other Co-based non-enzymatic glucose sensors.

A single-microbe living bioelectronic sensor for intracellular amperometric analysis

Subcellularly amperometric analysis in situ is crucial for understanding intracellular redox biochemistry and subcellular heterogeneity. Unfortunately, the ultra-small size and complex microenvironment inside the cell pose a great challenge to achieve this goal. To address the challenge, a minimized living microbial sensor has been fabricated in this work for amperometric analysis. Here, by fabricating the dimidiate microelectrode as the working electrode, while fitting a living electroactive bacterium (EAB) as the transducer, outward extracellular electron transfer (EET) of the sensory EAB is correlated with the concentration of lactic acid, which is electrochemically recorded and thus displays an electrical signal output for detection. In specific, the S. oneidensis modified dimidiate microelectrode (S.O.@GNE-NPE) acts as an integrated electroanalytical device to generate the electrical signal in situ. The established microcircuit provides unprecedented precision and sensitivity, contributing to subcellular amperometric measurement. The microbial sensor shows a linear response in the concentration range of 0–60 mM, with a limit of detection (LOD) at 0.3 mM. The microsensor also demonstrates good selectivity against interferences. Additionally, intracellular analysis of lactic acid provides direct evidence of enhanced lactic metabolism in cancer cells as a result of “Warburg Effect”. This work shows an example of nano-, bio- and electric technologies that have been integrated on the EAB-modified dimidiate microelectrode, and achieves intracellular biosensing application through such integration. It may give a new strategy on the combination of micro/nanotechnologies with sensory EAB for the necessary development of bioelectronic devices.

Reduced graphene oxide-modified electrodes via fused deposition modeling 3D printing for hydrogen peroxide sensor

Abstract 3D printed electrochemical electrode processes have garnered significant interest due to their promising applications. However, broader implementation remains constrained due to challenges in material selection, complex fabrication processes, and reproducibility issues. Fused Deposition Modeling (FDM) 3D Printing presents a simplified alternative, enabling swift and cost-effective production of electrochemical sensors. This paper introduces a novel manufacturing approach that uses a dual-printer setup for printing sensor electrodes and subsequent surface modification with reduced graphene oxide (rGO) casting. The electrode surfaces, both before and after rGO drop casting, are comprehensively characterized, including physical morphology, chemical composition, and electrochemical performance. As a result, the electrode, after surface modification with rGO, exhibits a sensitivity increase exceeding fortyfold compared to the pristine printed surface, as demonstrated through hydrogen peroxide (H2O2) amperometric measurements. This outcome opens up new avenues and prospects for the manufacturing of 3D printed electrochemical sensors.

A multiplexed sensing system with multimodal readout electronics and thread-based electrochemical sensors for high throughput screening

High throughput screening (HTS) based on microwell (or bioreactor) arrays is a well-established approach for rapid screening and identification of lead molecules or target analytes for drug discovery and other applications in biotechnology. However, it has been challenging to scale up these platforms due to the lack of integrated sensors to monitor the microenvironment of each microwell in the array needed. In this work, we present a practical solution for a miniaturized multiplexed sensing system with integrated circuitry capable of performing continuous electrochemical potentiometric and amperometric measurements. The platform uses lightweight multiplexed electrochemical sensors implemented on thin textile threads, all of which share a single operational amplifier (op-amp) and a switch network for both voltage and current measurements. The resulting platform forgoes the need for large-area sensors or bulky multichannel potentiostat with a simple readout circuitry capable of multimodal measurements. The design and validation of the multiplexed sensing system have been reported in the context of measuring pH and oxygen (O2), which are crucial biomarkers for any HTS application. The thread-based pH and O2 sensors possess sensitivities of ∼65.87 mV/pH for the pH sensor (n = 3) and 0.6621 nA/mg L-1 for the O2 sensor (n = 3). This architecture is modular such that it can be easily extended to monitoring multiple biomarkers employing thread-based sensors and sharing the same readout circuitry, making it a practical and versatile tool for biotechnology research.

P-EcStat: A Versatile Design of Photoelectrochemical and Electrochemical Sensing System with Smartphone Interface via Bluetooth Low Energy

Electrochemical and photoelectrochemical sensors are a rapidly developing field in analytical chemistry. However, commercial systems often lack versatility and affordability, hindering wider adoption. Additionally, the absence of integrated excitation light sources limits their application in photoelectrochemical sensing. Here, we present a highly precise, versatile, affordable measurement system for both electrochemical and photoelectrochemical sensing applications. The system incorporates a three-electrode potentiostat with a synchronized excitation light source. This design enables the system to perform conventional electrochemical measurements like cyclic voltammetry, chronoamperometry, and photoelectrochemical amperometric measurements with controlled light excitation. The developed measurement system operates within a voltage range suitable for a measurable current range of 1 nA to 18 mA, with a high precision of 99%. The excitation source is a monochromatic LED system offering seven distinct wavelengths with digitally controlled intensity via a digital-to-analog converter. Furthermore, an Android-based user interface allows wireless system control via Bluetooth Low Energy. The report also details the construction of a photoelectrochemical experiment using copper (II) oxide nanorods synthesized by the hydrothermal process as the photoactive material employed to test the experiment on a potassium ferricyanide/potassium ferrocyanide solution. This user-friendly system allows broader exploration of electrochemical and photoelectrochemical sensing applications.

Enhanced detection of glucose with carbon quantum dot-modified copper oxide: Computational insight and machine learning modeling of electrochemical sensing

Poor conductivity and surface passivation pose critical challenges in metal oxide structures during their application for non-enzymatic oxidation. To address this, we systematically employed in-situ deposition of carbon-quantum dots (C-dots) over copper oxide (CuO), enhancing its electrocatalytic properties for direct non-enzymatic glucose oxidation in alkaline media. The process involved the systematic deposition of varying wt.% of C-dots onto the CuO nanostructure. The electrode’s sensing capability was assessed through CV, DPV, and amperometric measurements, evaluating its suitability in high (0.1 to 0.85 mM) and low glucose concentration levels (15 to 225 nM) with a representative LOD of 1.4 nM (17142.86 µA mM−1 cm−2). Additionally, the CuO-Cdot-16.6 protective coating allowed for long-term working capability, with chronoamperometric measurement confirming a 99 % current retention ability compared to pristine CuO’s 39 % retention during 3500 s of continuous measurement. DFT calculations further confirmed the efficacy of CuO substrate as a scaffold for glucose adsorption. The stable CuO-glucose complex formed due to energetically favorable conditions further strengthens its potential as a sensor. Successful recoveries of spiked glucose serum samples validated the sensor’s practical usage in complex matrices. Moreover, Machine learning was also adopted to validate the accuracy of glucose detection, where artificial neural network (ANN) model emerged as a suitable model to interpret the DPV derived data relationships, adding in sensor working capability and promising its future application in precision/intelligent healthcare.

A novel strategy towards the fabrication of highly stable and sensitive non-enzymatic glucose sensor based on Ni3N thin films using high power impulse magnetron sputtering

Glucose level surveillance in mankind is considered the greatest need of recent times to achieve healthy lifestyle goals due to its health-related concern for humans. To fulfill the need, Nickel-based compounds emerge with excellent bio-mimic properties. However, due to the poor electrical properties of oxides and hydroxides of Ni, developing a supporting base that can enhance electron transportation is mandatory. The present work is dedicated to non-enzymatic glucose detection by electrochemical means on the Ni3N thin film on an Indium-doped Tin Oxide (ITO) substrate as a working electrode in an alkaline medium. The Ni3N films use HiPIMS as a deposition technique due to its high ionization rate of sputtered species and dense plasma which helps the Ni ions to react with nitrogen in the formation of a perfect Ni3N phase, and it is a green process that can contribute to sustainable manufacturing. Ni3N thin film deposited at a 60 % N2 flow ratio shows the largest crystallinity and catalytic properties, which helps this modified electrode to have significant potential for glucose detection. The Ni3N modified electrode acquires a lower linear range of 0.001–1.25 mM with sensitivity and Limit of Detection (LOD) of 337.46 µAmM–1cm−2, and 0.78 µM, respectively, and a higher linear range of 1.25–7.3161 mM with a sensitivity of 158.58 µAmM–1cm−2. The amperometric measurements reveal the fast response of the electrode towards glucose detection at 2.46 secs. The key measures of the electrode according to the corresponding measurements are satisfactory selectivity, reproducibility, repeatability, and operational stability. The modified electrode shows a significant response for real samples such as commercially available honey, apple juice, and biological fluids.

Disposable amperometric biotool for peanut detection in processed foods by targeting a chloroplast DNA marker

This work reports the development and application of a disposable amperometric sensor built on magnetic microcarriers coupled to an Express PCR strategy to amplify a specific DNA fragment of the chloroplast trnH-psbA. The procedure involves the selective capture of a 68-mer synthetic target DNA (or unmodified PCR products) through sandwich hybridization with RNA capture probe-modified streptavidin MBs and RNA signaling probes, labeled using antibodies specific to the heteroduplexes and secondary antibodies tagged with horseradish peroxidase. Amperometric measurements were performed on screen-printed electrodes using the H2O2/hydroquinone system. Achieving a LOD of 3 pM for the synthetic target, it was possible to detect 2.5 pg of peanut DNA and around 10 mg kg−1 of peanut in binary mixtures (defatted peanut flours prepared in spelt wheat). However, the detectability decreased between 10 and 1000 times in processed samples depending on the treatment. The Express PCR-bioplatform was applied to the detection of peanut traces in foodstuff.

Vapor phase polymerization of PEDOT on ITO/glass surfaces for nonenzymatic detection of dopamine

This study demonstrates the deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) as an electrically conductive polymer on the ITO-coated glass surfaces for the production of a non-enzymatic electrochemical sensor to detect dopamine. For this purpose, thin films of PEDOT were synthesized using vapor phase polymerization (VPP) from the corresponding monomer 3,4-ethylenedioxythiophene, in which iron(III)chloride was used as the oxidant. Films were deposited at different substrate temperatures, where the temperature dependence of doping and conjugation levels were studied using FTIR and XPS analyses. The highest doping and conjugation levels, as well as the highest film thickness (380 nm) was observed for the film deposited at 40 °C, which represented the highest conductivity of 111 S/cm. Significant differences were observed between the electrochemical responses of ITO/glass and PEDOT/ITO electrodes. Amperometric measurements indicated a limit of detection value of 2.02 µM for dopamine using as-synthesized PEDOT/ITO electrode.

ZnO sintering aid effect on proton conductivity of BaCe0.6Zr0.3Y0.1O3-δ electrolyte for hydrogen sensors

Proton-conducting solid-state electrolytes, including perovskite-type materials, hold promise for hydrogen sensor development. These sensors leverage the proton conductivity of such materials to detect hydrogen gas presence. However, achieving both high density for gas tightness and good protonic conductivity in these refractory materials can be challenging.In this study, we propose the preparation of dense pellets of BaCe0.6Zr0.3Y0.1O3-δ using ZnO as a sintering aid (BCZY-Zn). These pellets were extensively characterized using X-ray diffraction and electrochemical impedance spectroscopy and compared with pellets sintered without sintering aid (BCZY). Subsequently, BCZY-Zn electrolyte was utilized to fabricate amperometric sensors for hydrogen monitoring. Finally, amperometric measurements were conducted at 500 °C while maintaining a voltage of 150 mV between electrodes. The sensors' performance was evaluated for hydrogen partial pressures ranging from 12 to 100 Pa within an argon atmosphere. Additionally, response and recovery times were calculated.

Gel polymer electrolyte-based dual screen-printed electrodes for the headspace quantification of 4-ethylphenol and ethanethiol simultaneously in wines

The identification and correction of negative factors, such as 4-ethylphenol and ethanethiol, is important to comply with food safety regulations and avoid economic losses to wineries. A simple amperometric measurement procedure that facilitates the simultaneous quantification of both compounds in the gas phase has been developed using fullerene and cobalt (II) phthalocyanine-modified dual screen-printed electrodes coated with a room temperature ionic liquid-based gel polymer electrolyte. The replacement of the typical aqueous supporting electrolyte by low-volatility ones improves both operational and storage lifetime. Under the optimum conditions of the experimental variables, Britton Robinson buffer pH 5 and applied potentials of + 0.86 V and + 0.40 V for each working electrode (vs. Ag ref. electrode), reproducibility values of 7.6% (n = 3) for 4-ethylphenol and 6.6% (n = 3) for ethanethiol were obtained, as well as capability of detection values of 23.8 μg/L and decision limits of 1.3 μg/L and 9.2 μg/L (α = β = 0.05), respectively. These dual electrochemical devices have successfully been applied to the headspace detection of both compounds in white and red wines, showing their potential to be routinely used for rapid analysis control in wineries.Graphical

Facile chemiresistive biosensor functionalized with PANI/GOx and novel green synthesized silver nanoparticles for glucose sensing

This article presents a Glossy Photo-Paper (GPP) based Screen-Printed Chemiresistive Interdigitate Electrode (SPCIDE) for enzymatic glucose sensing. A facile inexpensive screen-printing method was used to print the low sheet resistance Interdigitate Electrodes (IDEs) with graphene as conductive ink on the proposed GPP. The screen-printed IDE was functionalized with Polyaniline (PANI) material by drop-cast technique to create a chemiresistive matrix. Further, for selective sensing of glucose, Glucose Oxidase (GOx) enzymes with Green Synthesized Silver Nanoparticles (GS-AgNPs) were immobilized on the PANI material. The proposed GPP-based SPCIDE sensor was used to detect glucose using amperometric measurements. With a correlation coefficient (R2) of 0.9803 and a lower Limit of Detection (LOD) equal to 198 nM, the proposed SPCIDE glucose sensor displays a linear association between change in current and corresponding glucose concentration in the range of 198 nM to 30 mM. An experimental result shows that the created SPCIDE sensor has a sensitivity of 291.19 µA mM−1 cm−2. The study shows that the proposed method may be used to produce facileGPP-based glucose sensors that are inexpensive, eco-friendly, bio-synthesizable, and biodegradable. This may result in developing a Point-of-Care (PoC) diagnostic kit for glucose testing as needed.

Reusable graphite-based electrochemical sensors for L-dopa and dopamine detection.

Afully reusable electrochemical device is proposed for the first timemade from laser cutting and a homemade conductive ink composed of carbon and nail polish. As a sensor substrate, we applied polymethyl methacrylate, which allows the surface to be renewed by simply removing and reapplying a new layer of ink. In addition to the ease of renewing the sensor's conductive surface, the design of the device has allowed for the integration of different forms of analysis. The determination of L-Dopa was performed using DPV, which presented a linear response range between 5.0 and 1000.0μmol L-1, and a LOD of 0.11μmol L-1. For dopamine, a flow injection analysis system was employed, and using the amperometric technique measurements were performed with a linear ranging from 2.0 to 100.0μmol L-1anda LOD of 0.26μmol L-1. To demonstrate its applicability, the device was used in the quantification of analytes in pharmaceutical drug and synthetic urine samples.

Carbon Nanotube Modified Glassy Carbon Electrodes for on‐line and off‐line in vitro Therapeutic Equivalence Assessment of Paracetamol Tablets

AbstractIn vitro bioequivalence assessment of paracetamol tablets was carried out by differential pulse voltammetry (DPV) and amperometry using a multiwalled carbon nanotube modified glassy carbon electrode (GCE/MWCNT). For the DPV developed method, samples were collected from the USP paddle apparatus, while amperometric measurements were carried out in situ. The DPV method was validated in three supporting electrolytes (per in vitro bioequivalence guidelines) by measuring the recovery from standard solutions and paracetamol tablet solutions, while precision was evaluated through the RSD (n=6). In HCl pH 1.2 solution the LOD and LOQ were 48 nM and 160 nM, respectively and the linear range was between 0.18–2.2 μM. In acetate buffer pH 4.5 the LOD and LOQ were 15 nM and 51 nM, respectively and the linear range was between 88 nM–880 nM. And in phosphate buffer pH 6.8 the LOD and LOQ were 4.6 nM and 15 nM, respectively and the linear range was between 88 nM–880 nM. Recovery values were between 95 and 105 % and precision values were less than 5 %. Results showed that both methods were effectively applied for the analysis of samples.

Electrochemical Sensors Based on Self-Assembling Peptide/Carbon Nanotube Nanocomposites for Sensitive Detection of Bisphenol A.

In this study, a cationic amphiphilic self-assembling peptide (SAP) Z23 was designed, and a simple bisphenol a (BPA) sensor, based on SAP Z23/multiwalled carbon nanotubes (Z23/MWCNTs) composite, was successfully fabricated on the surface of a glassy carbon electrode (GCE). The composite material was formed by π-π stacking interaction between the aromatic group on the hydrophobic side of Z23 and the side-wall of MWCNTs, with the charged hydrophilic group of Z23 exposed. During the electrocatalytic process of BPA, a synergistic effect was observed between Z23 and MWCNTs. The current response of the sensor based on composite material was 3.24 times that of the MWCNTs-modified electrode, which was much higher than that of the peptide-based electrode. Differential pulse voltammetry (DPV) was used to optimize the experimental conditions affecting the analytical performance of the modified electrode. Under optimal conditions, the linear range of the sensor was from 10 nM to 100 μM by amperometric measurement with sensitivity and limit of detection (LOD) at 6.569 μAμM-1cm-2 and 1.28 nM (S/N = 3), respectively. Consequently, the sensor has excellent electrochemical performance and is easy to fabricate, making it a good prospect in the field of electrochemical detection in the future.