Screen-printed Carbon Electrode Research Articles

Disposable and Sensitive Electrochemical Determination of Isoliquiritigenin in Licorice Using Screen-Printed Carbon Electrode Modified With Multi-Walled Carbon Nanotubes

Herein, a high-sensitive electrochemical sensor based upon a multi-walled carbon nanotubes modified screen-printed carbon electrode (MWCNTs-SPCE) was constructed for the determination of isoliquiritigenin (ISL). The electrochemical properties of ISL on the MWCNTs-SPCE were investigated systematically and a fast and cost-effective method for the determination of ISL was successfully established. A clear irreversible oxidation peak of the ISL was observed at 0.3 V (versus Ag/AgCl) on the MWCNTs-SPCE. The oxidation of ISL on MWCNTs-SPCE was an adsorption reaction accompanied by diffusion. Using differential pulse voltammetry (DPV), we observed that the oxidation peak current of the ISL in phosphate buffer (pH 7) showed a linear relationship from 0.50 to 100 µg/mL and a detection limit of 0.10 µg/mL. This method displayed good repeatability and stability, as well as exhibited excellent selectivity for ISL. Also, we successfully applied the method to determine ISL in Chinese herbal medicine licorice. Validation of the analyses via spike assays showed a recovery rate ranging from 95.39 to 101.00%, which was consistent with high performance liquid chromatography (HPLC).

Computational aptamer design for spike glycoprotein (S) (SARS CoV-2) detection with an electrochemical aptasensor

A new bioinformatic platform (APTERION) was used to design in a short time and with high specificity an aptamer for the detection of the spike protein, a structural protein of SARS-CoV-2 virus, responsible for the COVID-19 pandemic. The aptamer concentration on the carbon electrode surface was optimized using static contact angle and fluorescence method, while specificity was tested using differential pulse voltammetry (DPV) associated to carbon screen-printed electrodes. The data obtained demonstrated the good features of the aptamer which could be used to create a rapid method for the detection of SARS-CoV-2 virus. In fact, it is specific for spike also when tested against bovine serum albumin and lysozyme, competitor proteins if saliva is used as sample to test for the virus presence. Spectrofluorometric characterization allowed to measure the amount of aptamer present on the carbon electrode surface, while DPV measurements proved the affinity of the aptamer towards the spike protein and gave quantitative results. The acquired data allowed to conclude that the APTERION bioinformatic platform is a good method for aptamer design for rapidity and specificity.Key points• Spike protein detection using an electrochemical biosensor• Aptamer characterization by contact angle and fluorescent measurements on electrode surface• Computational design of specific aptamers to speed up the aptameric sequence time

Non-enzymatic glucose sensor using mesoporous carbon screen-printed electrodes modified with cobalt phthalocyanine by phase inversion

The development of non-enzymatic glucose electrochemical sensors is still required to be used for the determination of glucose in complex biological media. This study presents a straightforward and remarkably efficient tool for the preparation of highly stable and sensitive glucose electrochemical sensors based on the deposition of cobalt phthalocyanine (CoPc) onto mesoporous carbon screen-printed electrodes (MCs). Results show that the MC electrochemical activation (aMC) followed by phase inversion (PI), which consisted of drop casting of CoPc in dimethylformamide onto a wetting electrolyte leading to the electrode aMC-CoPc/PI, enhanced sensitivity towards glucose determination in complex media. The beneficial need for MC surface activation and PI has been explored by scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The aMC-CoPc/PI electrode exhibited the highest electrocatalytic activity of the series (namely, MC-CoPc, MC-CoPc/PI and aMC-CoPc) towards glucose oxidation. By using square wave voltammetry technique, the aMC-CoPc/PI glucose electrochemical sensor demonstrated a sensitivity of 22.3 µA mM−1 and a low detection limit of 27.4 µM (S/N = 3) in a linear dynamic range of 0.1 to 3.5 mM. Additionally, it also displayed high selectivity, robust stability, repeatability and reproducibility toward the quantification of glucose concentration in complex samples such as horse serum, intravenous glucose saline solution and culture medium for sperm cells.

MIL-88A derived zerovalent iron embedded mesoporous carbon with carbon black composite based electrochemical sensor for the detection of metol

The release of industrial effluents contributes to environmental degradation, posing a significant challenge to sustainable development. Metol (MTL) is a popular color-developing agent which is extensively used in the hair dyes and photographic industries. The massive usage and improper disposal of MTL into water resources would adversely affect the ecosystem. Therefore, we have prepared a MOF-derived zerovalent iron in mesoporous carbon (Fe@C) with a carbon black (CB) electrocatalyst for the detection of MTL. The structural and elemental details were examined with several spectroscopic techniques. Our prepared electrocatalyst was used to modify the screen-printed carbon electrode (SPCE). The electrochemical property of the fabricated sensor was investigated with impedance and voltammetric measurements. The catalytic activity of Fe@C/CB/SPCE towards MTL was scrutinized with different voltammetric techniques. Consequently, our Fe@C/CB/SPCE demonstrated a low detection limit (0.003 μM), high sensitivity (12.948 μA μM−1 cm−2), two linear ranges (at lower concentrations (0.01–27 μM), and higher concentrations (27–142 μM)), good selectivity, and appreciable stability results. The practical utility of the reported sensor was determined by monitoring MTL in various real-world water samples (tap, pond, and river). Based on the outcomes of the experiment, it would be suggested that our Fe@C/CB is a propitious catalyst for the electrochemical detection of MTL.

Novel Deliberately Sensitive and Selective Tetrahydrozoline Voltammetric Sensors Integrated with a Copper Oxide Nanoparticle/Zeolite Platform.

The present study introduced a novel disposable screen-printed carbon electrodes (SPCEs) modified with copper oxide/zeolite nanostructures for eco-friendly selective differential pulse voltammetric quantification of tetrahydrozoline (THZ) in eyedrop samples and biological fluids. Modification of the electrode matrix with copper oxide nanoparticles/zeolite nanostructures (CuONPs/ZY) with their effective and synergistic electrocatalytic activity enhanced the electrode performance against electrooxidation of THZ at 0.960 V in BR at pH 9.0 with a diffusion-controlled reaction mechanism. The tentative oxidation mechanism based on molecular orbital calculations postulates the oxidation of THZ molecules through oxidation of a nitrogen atom five-membered ring and the participation of two electrons/protons in the electrode reaction. Linear calibration curves were illustrated within a wide THZ concentration range from 0.24 to 57.2 μg mL-1 recording a limit of detection (LOD) value of 0.0799 μg mL-1. The CuONPs/ZY/SPEs exhibited improved performance compared with the sole reported THZ sensor-based gold film-plated carbon paste electrodes, in addition to their high reproducibility of fabrication and measurement and prolonged shelf lifetime. Tetrahydrozoline was successfully assayed in the presence of excipients, degradation products, and chloramphenicol. The presented voltammetric sensor can be considered as an eco-friendly and reliable analytical approach for monitoring THZ residues in eye drop samples and biological fluids with high recovery compared with the official pharmacopeial analytical protocol. The presented sensors were assessed according to an EcoScale tool and also compared with the reported THZ sensor.

A novel ACE2-Based electrochemical biosensor for sensitive detection of SARS-CoV-2

SARS-CoV-2 emerged in late 2019 and quickly spread globally, resulting in significant morbidity, mortality, and socio-economic disruptions. As of now, collaborative global efforts in vaccination and the advent of novel diagnostic tools have considerably curbed the spread and impact of the virus in many regions. Despite this progress, the demand remains for low-cost, accurate, rapid and scalable diagnostic tools to reduce the influence of SARS-CoV-2. Herein, the angiotensin-converting enzyme 2 (ACE2), a receptor for SARS-CoV-2, was immobilized on two types of electrodes, a screen-printed gold electrode (SPGE) and a screen-printed carbon electrode (SPCE), to develop electrochemical biosensors for detecting SARS-CoV-2 with high sensitivity and selectivity. This was achieved by using 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT) and aryl diazonium salt serving as linkers for SPGEs and SPCEs, respectively. Once SARS-CoV-2 was anchored onto the ACE2, the interaction of the virus with the redox probe was analyzed using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Aryl diazonium salt was observed as a superior linker compared to PFDT due to its consistent performance in the modification of the SPCEs and effective ACE2 enzyme immobilization. A distinct pair of redox peaks in the cyclic voltammogram of the biosensor modified with aryl diazonium salt highlighted the redox reaction between the functional groups of SARS-CoV-2 and the redox probe. The sensor presented a linear relationship between the redox response and the logarithm of SARS-CoV-2 concentration, with a detection limit of 1.02 × 106 TCID50/mL (50% tissue culture infectious dose). Furthermore, the biosensor showed remarkable selectivity towards SARS-CoV-2 over H1N1virus.

Development of dialkyl-triazolium ionogels for printed supercapacitor

The use of electrolytes has a very crucial role in supercapacitors. Liquid electrolytes cause many problems, like leakage, whereas aqueous electrolytes show only lower potential windows. These are improved by ionic liquid gel polymer electrolytes. In this work, we have synthesized 4 ILs, namely 1,4-dipropyl-1,2,4-triazolium BF4,1-propyl-4-butyl-1,2,4-triazolium BF4, 1,4-dipropyl-1,2,4-triazolium PF6,and 1-propyl-4-butyl-1,2,4-triazolium PF6 and studied their thermal and electrochemical properties. From them, the most efficient 1,4-dipropyl-1,2,4-triazolium BF4 IL is combined with PVA polymer, made into gel polymer electrolyte, coated over a carbon screen-printed electrode, and tested. The fabricated solid-state capacitor prototype yields a capacitance of 98.8 mFcm−2 at a least scan rate of 2 mV/s and the calculated areal energy density and areal power density were 0.221 µWh and 52 µWcm−2 respectively. Cyclic stability with GCD gave 80 % capacitive retention even after 3000 cycles.

In vitro drug screening models derived from different PC12 cell lines for exploring Parkinson's disease based on electrochemical signals of catecholamine neurotransmitters.

Goldnanostructures anda Nafion modified screen-printed carbon electrode (Nafion/AuNS/SPCE) were developed to assess the cell viability of Parkinson's disease (PD) cell models. The electrochemical measurement of cell viability was reflected by catecholamine neurotransmitter (represented by dopamine) secretion capacity, followed by a traditional tetrazolium-based colorimetric assay for confirmation. Due to the capacity to synthesize, store, and release catecholamines as well as theirunlimited homogeneous proliferation, and ease of manipulation, pheochromocytoma (PC12) cells were used for PD cell modeling.Commercial low-differentiated and highly-differentiated PC12 cells, and home-made nerve growth factor (NGF) induced low-differentiated PC12 cells (NGF-differentiated PC12 cells)were included in the modeling. This approach achieved sensitive and rapid determination of cellular modeling and intervention states. Notably, among the three cell lines, NGF-differentiated PC12 cells displayed the enhanced neurotransmitter secretion level accompanied with attenuated growth rate, incremental dendrites in number and length that were highly resemble with neurons. Therefore, it was selected as the PD-tailorable modeling cell line. In short, the electrochemical sensor can be used to sensitively determine the biological function of neuron-like PC12 cells with negligible destruction and to explore the protective and regenerative impact of various substances on nerve cell model.

FAST MICROWAVE ASSISTED FUNCTIONALIZATION OF CARBON NANOFIBERS: A PROMISING ELECTROCHEMICAL SENSING PLATFORM FOR ELECTROACTIVE ANALYTES

This research introduces a novel approach for swiftly enhancing the electrochemical sensing capabilities of commercial screen-printed carbon electrodes through a rapid acid microwave-assisted functionalization of carbon nanofibers (f-CNFMW). A comparative analysis with the conventional refluxed system functionalization method (f-CNFRefluxed) was conducted to assess the electrochemical performance of the newly developed f-CNFMW. The voltametric study showed that f-CNF-MW significantly enhanced the electron transfer rate when testing common phenolic compounds such as hydroquinone, paracetamol, and caffeic acid. Moreover, the anodic oxidation potential for the majority of irreversible analytes was negatively shifted, indicating the high electro-catalytic activity of f-CNF-MW gained after this treatment, making it analytically useful for the electro-oxidation of some molecules that require high overpotential, mainly for purine bases and nitrite. Additionally, the developed f-CNF-MW exhibited remarkable resistance to fouling phenomena when exposed to bisphenol A and tryptophan, underscoring its potential for real-world applications. To sum up, this study highlights the potential of rapid microwave treatment in producing f-CNF-MW as a promising electrochemical nanomaterial, resulting in substantial improvements in electro-analytical capabilities compared to conventional methodologies.

Sensitive determination of bisphenol S from food samples using chitosan modified polyaniline: Detection optimization via Box Behnken Design

Increased global awareness and the selective ban on bisphenol A (BPA) toxicity have prompted manufacturers to seek alternatives. Bisphenol S (BPS) emerges as one such alternative for potential food packaging replacement. However, BPS is not exempt from toxicity concerns. In this study, we demonstrate a straightforward method using a polyaniline/chitosan (PANI/Cht) composite drop-coated onto a screen-printed carbon electrode to selectively and sensitively detect BPS in food samples. PANI/Cht sensitivity was optimized through Box Behnken Design, considering factors such as dosage, pH, and contact time. ANOVA analysis highlighted dosage and contact time as significant in sensitive BPS detection. The PANI/Cht sensor exhibits excellent linearity (0.2–50 µM) with a low detection limit of 18.65 nM. Furthermore, the sensor showcases satisfactory reproducibility, selectivity, long-term stability, and recoveries for spiked BPS in real food matrices.

Portable smartphone-based aptasensor for nitrofuran detection

A portable electrochemical aptasensor for the detection of nitrofuran (NF) was developed. Aptamer-conjugated gold nanoparticles (Apt-AuNPs) were immobilized on a chitosan (CS) thin film electrodeposited on a screen-printed carbon electrode (SPCE). The modified electrode was connected to a smartphone-controlled near-field communication (NFC) potentiostat. The electrochemical aptasensor determined NF concentration using cyclic voltammetry (CV) and chronoamperometry (CA) techniques. Under optimal conditions, the developed aptasensor exhibited high sensitivity (11.26 ± 0.38 μA L/μg), a wide linear range (0.005 to 0.08 μg/L and 0.08 to 4.0 μg/L), and a low detection limit (0.004 μg/L). Our construction demonstrated excellent stability for NF, with a reduction in current of less than 10 % even after 330 days. Reproducibility (%RSD = 2.19 %) was good, and the device was portable, simple, and selective. Therefore, this aptasensor platform was applied as a smartphone-based wireless NFC potentiostat for NF detection in shrimp pond water and shrimp samples.

Enhanced electrocatalytic activity of bismuth-doped lanthanum stannate pyrochlore for electrochemical detection of the Covid-19 drug nitazoxanide

Nitazoxanide (NAZ) is an antiparasitic drug that reduces inflammation caused by the SARS-CoV-2 virus. The presence of nitro group in this drug makes it an environmental pollutant. Here, an electrochemical sensor for the determination of NAZ was developed based on bismuth-doped pyrochlore lanthanum stannate nanoparticles modified screen-printed carbon electrodes (BLSO NPs/SPCE). The BLSO NPs were prepared by a combination of co-precipitation and thermal calcination processes. The fabricated BLSO NPs were analyzed by different spectroscopic methods. X-ray diffraction analysis (XRD), Fourier transform-infrared spectroscopy (FT-IR), and Raman spectroscopy showed that the lattice parameters of the lanthanum stannate nanoparticles (LSO NPs) were increased after bismuth doping due to cell expansion. The morphology and oxidation state of the elements in the BLSO NPs were analyzed by field emission-scanning electron Microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS). FE-SEM and HR-TEM analysis revealed that LSO, and BLSO exhibits as a nanoparticle morphology with 20–50 nm in size. Cyclic voltammetry (CV) showed that the electrochemical reduction of NAZ was enhanced after bismuth doping due to the synergistic effect of BLSO NPs. Electrochemical determination of NAZ was performed by DPV with a low detection limit of 4 nM between the linear range of 0.01–172 µM and an electrode sensitivity of 0.16 µA µM−1 cm−2. The developed NAZ sensor showed favorable results in terms of selectivity, repeatability, and stability.

Insight into the electrochemical performance of heavy metal-free quantum dots in different buffered ferricyanide/ferrocyanide redox systems

The ferricyanide/ferrocyanide K3[Fe(CN)6]/K4[Fe(CN)6] redox couple is a widely utilized redox probe in electrochemistry. Buffering the K3[Fe(CN)6]/K4[Fe(CN)6] system has become one of the ways to generate improved electron transfer rates and stable electrochemical systems. In recent years, semiconductor quantum dots (QDs) have gained popularity as nanotags in electrochemical applications. Herein, we report on the comparative electrochemical behaviour of cadmium-free AuZnFeSeS quantum dots (QDs)-modified screen-printed carbon electrode (SPCE) in different buffered K3[Fe(CN)6]/K4[Fe(CN)6] electrolyte solutions using voltammetry and electrochemical impedance spectroscopy (EIS) techniques. Our results showed that the QDs/SPCE exhibited faster electron transfer rates, lower energy barrier and lower charge transfer resistance (Rct) in the studied buffered electrolyte solution.

Synthesis and characterization of N-MPG/CuS flower-like/MXene to modify a screen-printed carbon electrode for electrochemical determination of nalbuphine

Nalbuphine (NAL) is a drug with narcotic properties and analgesic effects, and its use has side effects such as drowsiness, nausea, and headache. Excessive use of this drug leads to death. Measuring NAL is important to ensure that the correct dose is administered to the patient and to avoid overdose or underdose. It is also important to monitor the patient's response to the medication and adjust the dosage if necessary. Additionally, measuring nalbuphine levels may be important in cases of suspected overdose or toxicity. In the present research, a very simple and cheap method based on screen-printed carbon electrodes coated with CuS flower-like and N-doped mesoporous graphene and MXene was constructed for the measurement of NAL. At first, the modifier was analyzed by SEM, EDS, and TEM methods. Then, the NAL measurement was done by cyclic and differential pulse voltammetry techniques. Results showed a good ability of the prepared sensor for measurement of NAL in the span of 5–150 μM, which reached a detection limit of 1.6 μM. The prepared sensor showed the capability of NAL measurement in real samples.

Modified exfoliated graphene functionalized with carboxylic acid-group and thionine on a screen-printed carbon electrode as a platform for an electrochemical enzyme immunosensor.

An enzyme immunoassay was developed based on the coulometric measurement of immunoglobulin M (IgM) against Hantaan viruses (HTNV) by using virus-like particles (VLPs) as recognition molecules. The surface functionalization of screen-printed carbon electrodes (SPCEs) was achieved through paste-exfoliated graphene that was modified with a COOH group and a thionine mediator through supramolecular-covalent scaffolds, on SPCEs by using the binder contained in the ink. After the covalent immobilization of the antibody, the sensor was used for the sandwich enzyme immunoassay of IgM against HTNV. By using HTNV VLPs as the second recognization molecules, the resulting sensor efficiently monitored the reaction of IgM against HTNV and anti-IgM antibody with high specificity. By attaching HTNV nucleocapsid protein antibody conjugate with horseradish peroxidase (HRP) onto VLPs, the signal response of the assay was derived from the coulometric measurement of H2O2 reduction mediated by thionine on the electrode surface after the application of a potential (- 0.2V vs. Ag/AgCl). The ratio of charges measured before or after H2O2 addition was used to quantify IgM because these charges could be used as background charges or total charges, respectively. The ratio exhibited good agreement with IgM concentration within a range 0.1 to 1000pgmL-1, and a detection limit of 0.06pgmL-1 was obtained. The assay demonstrated high sensitivity and specificity toward HTNV-specific IgM in serum.

Electrochemical biosensor for the evaluation of monoclonal antibodies targeting the N protein of SARS-CoV-2 virus

The emergence of COVID-19 caused by the coronavirus SARS-CoV-2 has prompted a global pandemic that requires continuous research and monitoring. This study presents a design of an electrochemical biosensing platform suitable for the evaluation of monoclonal antibodies targeting the SARS-CoV-2 nucleocapsid (N) protein. Screen-printed carbon electrodes (SPCE) modified with gold nanostructures (AuNS) were applied to design a versatile and sensitive sensing platform. Electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV), were used to investigate the interactions between immobilised recombinant N (rN) protein and several monoclonal antibodies (mAbs). The electrochemical characterisation of SPCE/AuNS/rN demonstrated a successful immobilisation of rN, enhancing the electron transfer kinetics. Affinity interactions between immobilised rN and four mAbs (mAb-4B3, mAb-4G6, mAb-12B2, and mAb-1G5) were explored. Although mAb-4B3 showed some non-linearity, the other monoclonal antibodies exhibited specific and well-defined interactions followed by the formation of an immune complex. The biosensing platform demonstrated high sensitivity in the linear range (LR) from 0.2 nM to 1 nM with limits of detection (LOD) ranging from 0.012 nM to 0.016 nM for mAb-4G6, mAb-12B2, and mAb-1G5 and limits of quantification (LOQ) values ranging from 0.035 nM to 0.139 nM, as determined by both EIS and SWV methods. These results highlight the system's potential for precise and selective detection of monoclonal antibodies specific to the rN. This electrochemical biosensing platform provides a promising route for the sensitive and accurate detection of monoclonal antibodies specific to the rN protein.

Electrochemical determination of riboflavin in pharmaceuticals using unmodified screen printed carbon electrodes.

In this study, we have devised an efficient and rapid approach to detect riboflavin (also known as Vitamin B2 or VB2) utilizing an unaltered screen-printed carbon electrode (SPCE). The unmodified screen-printed electrodes are created within the laboratory, where carbon ink is applied to a ceramic substrate. All experiments pertaining to the investigation of electrochemical behavior and the fine-tuning of crucial experimental parameters were conducted through cyclic voltammetry (CV). For quantitative assessments, square wave voltammetry (SWV) was employed. The findings indicate that unaltered SPCEs exhibit robust current signals during the riboflavin redox reaction. Riboflavin displays a distinct oxidation peak at -0.136V (vs. Ag/AgCl, 3.0M KCl) in a Britton-Robinson buffer solution (BRBS) at pH 2, which was employed for quantification. The electrode demonstrates a broad linear range from 0.05 to 10µM, boasting a detection limit of 0.03µM. Repeatability stands at 1.45%, while reproducibility is 6.61%. Testing the influence of common interfering compounds yielded negligible results. The sensor effectively determines riboflavin content in pharmaceutical formulations without any prior treatment. This method presents an economical, modifier-free sensor with exceptional sensitivity and cost-effectiveness, making it suitable for rapid riboflavin quantification.

Screen-Printed Carbon Electrode Modified with Carbon Nanotubes and Copper Film as a Simple Tool for Determination of Trace Concentrations of Lead Ions.

A copper film-modified, carboxyl-functionalized, and multi-walled carbon nanotube (MWCNT-COOH)-modified screen-printed carbon electrode (CuF/MWCNTs/SPCE) was used for lead determination using anodic stripping voltammetry. The main parameters were investigated and optimized during the development of the research procedure. The most optimal electrolyte concentrations were determined to be 0.4 M HCl and 6.3 × 10-5 M Cu(II). The optimal parameters for voltammetric stripping measurements are as follows: an accumulation potential of -0.7 V; an accumulation time of 120 s; and a pulse amplitude and pulse time of 120 mV and 2 ms, respectively. The effect of surface active substances and humic substances as potential interferents present in aqueous environmental samples was investigated. The validation of the procedure was carried out using certified reference materials, like waste water SPS-WW1 and environmental matrix TM-25.5. In addition, the developed procedure was applied to investigate lead recovery from natural environmental water, such as rivers and lakes.

Simultaneous Electrochemical Detection of Dopamine and Uric Acid via Au@Cu-Metal Organic Framework.

The incorporation of noble metals with metal-organic frameworks (MOFs) are conducive to the simultaneous electrochemical detection of analytes owing to multiple accessible reaction sites. Herein, Au@Cu-metal organic framework (Au@Cu-MOF) is successfully synthesized and modified as a screen-printed carbon electrode (SPCE), which serves as an excellent electrocatalyst for the oxidation of dopamine (DA) and uric acid (UA). The sensor shows a linear range from 10 μM to 1000 μM, with sensitivity and detection limit of 0.231 μA μM-1 cm-2 and 3.40 μM for DA, and 0.275 μA μM-1 cm-2 and 10.36 μM for UA. Au@Cu-MOF could realize the individual and simultaneous electrochemical sensing of DA and UA, with distinguishable oxidation peak potentials. Moreover, it exhibits reproducibility, repeatability, and stability. Ultimately, the sensor provides an avenue for an ultrasensitive label-free electrochemical detection of DA and UA.

First Acyclovir Determination Procedure via Electrochemically Activated Screen-Printed Carbon Electrode Coupled with Well-Conductive Base Electrolyte.

In this work, a new voltammetric procedure for acyclovir (ACY) trace-level determination has been described. For this purpose, an electrochemically activated screen-printed carbon electrode (aSPCE) coupled with well-conductive electrolyte (CH3COONH4, CH3COOH and NH4Cl) was used for the first time. A commercially available SPCE sensor was electrochemically activated by conducting cyclic voltammetry (CV) scans in 0.1 mol L-1 NaOH solution and rinsed with deionized water before a series of measurements were taken. This treatment reduced the charge transfer resistance, increased the electrode active surface area and improved the kinetics of the electron transfer. The activation step and high conductivity of supporting electrolyte significantly improved the sensitivity of the procedure. The newly developed differential-pulse adsorptive stripping voltammetry (DPAdSV) procedure is characterized by having the lowest limit of detection among all voltammetric procedures currently described in the literature (0.12 nmol L-1), a wide linear range of the calibration curve (0.5-50.0 and 50.0-1000.0 nmol L-1) as well as extremely high sensitivity (90.24 nA nmol L-1) and was successfully applied in the determination of acyclovir in commercially available pharmaceuticals.