Voltammetry Detection Research Articles

Highly conductive Ti3C2 MXene-supported CoAl-layered double hydroxide nanosheets for ultrasensitive electrochemical detection of organophosphate pesticide fenitrothion.

A novel electrochemical method is presented for ultrasensitive detection of the organophosphate pesticide (OPP) fenitrothion by using Ti3C2 MXene/CoAl-LDH nanocomposite as the electrode modifier. The Ti3C2 MXene/CoAl-LDH nanocomposite is synthesized by growing CoAl-LDH in situ on MXene nanosheets. The combination of two ultrathin 2D materials provides more active sites, larger specific surface area, superior adsorption properties, and better electrical conductivity, which leads to rapid electron-transfer and mass-transfer between the substrate electrode and analytes when it is acted as the electrochemical sensing material. In addition, through the chelation of phosphate groups with the Ti defect sites enriched in MXene, OPP is adsorbed on the electrode. Consequently, the corresponding modified electrode gives rise to a wide linear response range of 0.03 ~ 120μmol/L for the differential pulse voltammetry detection of fenitrothion with a low detection limit of 5.8nmol/L (3σ). The method offers good repeatability, stability, selectivity, and practicability for real samples. This strategy provides a reference platform for the electrochemical monitoring of trace OPPs residue by using MXene/LDH-based nanocomposites.

A novel, rapidly-constructed synergistic copolymer-metallocene electrode with drug-detection capabilities

Electropolymerized poly(diphenylamine-co-4,4′-diaminodiphenyl ether) (P(DPA-co-4,4′-DADPE)) on carbon paste electrode (CPE) surface, forms a thin, porous nanofilm with low impurity content, and high resistance to toxicity and electrocatalytic properties. In this research, we aim to enhance the properties of the copolymer by immersing it in a chloroferrocene solution for only 4 min. This facilitates the formation of a novel, robust synergistic electrode. Optimization of this electrode is influenced by the concentration of ferrocene, immersion time, and scan rate. Various characterization techniques including CV (Cyclic Voltammetry), FESEM (Field-Emission Scanning Electron Microscopy), EDS (Energy-Dispersive X-ray Spectroscopy), XRD (X-ray Diffraction), and IR (Infrared Spectroscopy) were employed to investigate the electrode. This synergistic electrode exhibits a current density of 9.67 and 24.67 times higher compared to nano-copolymer and ferrocene electrodes, respectively. The kinetic parameters, Γ∗, α, ks, and n, for the electrode, are 4.10 × 10−7mol/cm2, 0.485, 61.13 s−1, and 1. As a result, the electrode displays appropriate velocity, quasi-reversible kinetic characteristics, and behavior compatible with the surface adsorption process. Furthermore, it exhibits a higher active surface concentration of redox compared to copolymer and ferrocene electrodes. The synergistic electrode also demonstrates a significant improvement in electron exchange yield with ΔEp, 43 % less than copolymer/CPE. These findings, combined with electrochemical stability and pH independence of the new electrode, resulting from the synergistic effect of ferrocene and copolymer, indicate its potential as a robust redox mediator. Finally, the catalytic effect of the electrode in cyclic voltammetry detection of amoxicillin was confirmed, with a Limit of Detection (LOD) and Limit of Quantification (LOQ) within the dynamic range of 2.00 × 10−5–8.00 × 10−4 M, was estimated equal to 1.42 × 10−6 and 4.73 × 10−6, respectively.

Electrochemical immunosensors for 2,4-dichlorophenoxyacetic acid based on 3-aminopropyltrimethoxysilane modified electrodes

A novel electrochemical immunosensor prepared by direct coating of small molecular hapten on glassy carbon electrode (GCE) is reported for the detection of 2,4-dichlorophenoxyacetic acid (2,4-D). The glassy carbon electrodes were activated by electrochemical method and then were further treated with 3-aminoprpyltriethoxysilane (APS) to functionalize the GCE surface with amino groups for covalent linkage to small molecular hapten of 2,4-D with carboxyl groups. The electrodes were characterized by X-ray photoelectron spectroscopy (XPS). The principle of this immunoassay is based on an indirect competitive immunoassay. Analytes of 2,4-D and hapten of 2,4-D immobilized on glassy carbon electrode (GCE) compete for 2,4-D antibodies labeled by horseradish peroxidase (HRP-anti-2,4-D). After complete immunoreaction, the GCE attached HRP-anti-2,4-D tracers was transferred to a substrate solution containing hydroquinone (QH2) and hydrogen peroxide for square wave voltammetry (SWV) detection. Determination conditions were optimized. The SWV anodic peak current decreased linearly with the increase of 2,4-D concentration over the range from 0.10 to 15.0 mg/L 2,4-D with a detection limit of 0.01mg/L. The performance of this electrochemical immunoassay was successfully evaluated with river water spiked with 2,4-D, indicating that this convenient, rapid, and sensitive technique offers great prospect for the monitoring of trace 2,4-D in environment.

Research on differential pulse voltammetry detection method for low concentration glucose based on machine learning model

In the electrochemical detection process, determining the optimal experimental conditions for the standard curve often requires multiple iterations. A low-concentration glucose detection method that combines electrochemical principles with machine learning was introduced to address the challenge of determining the optimal reactant addition in electrochemical detection. We developed a model that incorporates electrochemical curve features and various experimental conditions as variables. Concentration regression analysis was conducted using five machine learning models: Multiple Linear Regression (MLR), Decision Trees (DT),Artificial Neural Networks (ANN), Random Forest (RF), and Extreme Gradient Boosting (XGBoost). The results show that the performance of the XGBoost model surpasses that of the other models. Compared to the second place—Random Forest model, it reduces the Mean Absolute Error (MAE) by 21.6 % and the Root Mean Square Error (RMSE) by 25.3 %. This method can be used for low-concentration glucose detection, addressing the challenge of determining the optimal experimental conditions. It mitigates the impact of experimental conditions on detection results, enhances concentration determination accuracy, and provides new methods for determining the optimal experimental conditions and improving detection accuracy in the field of detection and analysis.

Dioctylsulfosuccinate Functionalized NiAl-Layered Double Hydroxide for Sensitive Fenuron Electroanalysis Using a Carbon Paste Electrode.

Environmental pollution resulting from the use of pesticides such as fenuron poses significant health risks due to the carcinogenic and teratogenic properties of these compounds. There is an urgent need to develop rapid and cost-effective detection methods for quantifying fenuron. In this study, an inorganic-organic composite material was obtained by intercalating sodium dioctylsulfosuccinate (DSS) within the interlayer space of a nickel-aluminum-layered double hydroxide (NiAl-LDH). The pristine and modified LDHs (NiAl-LDH) were characterized using Fourier transform infrared, X-ray diffraction, and thermogravimetric analysis, confirming the successful intercalation of DSS in the mineral structure. The modified LDH was used to elaborate a sensor for detecting fenuron herbicide via differential pulse voltammetry (DPV) employing a carbon paste electrode (CPE). The electrochemical procedure for fenuron analysis consisted of immersing the working electrode in an electrolytic solution containing the appropriate amount of fenuron, followed by voltammetry detection without any preconcentration step. Compared to CPE modified by pristine LDH, the peak current obtained on the organo-LDH-modified CPE was twice as high. The increase in the fenuron signal was attributed to the high organophilic feature of this composite material induced by DSS modification. To optimize the sensitivity of the organo-LDH modified electrode, the effects of several experimental parameters such as pH of the medium and proportion of the modifier in the paste on the stripping response were examined. Linear calibration curves were obtained for the fenuron concentrations ranging from 0.5 × 10-6 to 1 × 10-6 mol.L-1 and 1 × 10-6 to 5 × 10-6 mol.L-1. The limit of detection (LOD) calculated on the basis of a signal-to-noise ratio of 3 was found to be 1.8 × 10-8 mol.L-1 for the low concentration range with a limit of quantification (LOQ) which was 6 × 10-8 mol.L-1. Furthermore, the interference effect of several inorganic ions and other pesticides potentially affecting fenuron stripping was explored, and the method's applicability was confirmed by determining fenuron levels in a river sample taken from down-town Yaoundé.

Electrochemical detection of p-nitrophenol over nickel nanoparticles supported on Longquan lignite-derived mesoporous carbon fabricated by hard template method

The efficient and clean utilization of low-rank lignite conforms the strategy of carbon neutral development. Herein, a two-step strategy of hard template method and co-precipitation method was designed to prepare nickel nanoparticles supported on mesoporous carbon (Nix/MPC) using the residue from the ethanolysis of Longquan lignite for quantitative detection of p-nitrophenol (NP). The electrochemical reduction properties of modified glassy carbon electrodes (GCEs) with different nickel loadings (x = 10, 15, and 20 wt%) for NP were compared, in which Ni15/MPC/GCE stood out and presented better conductivity, larger electrochemical active surface area, and faster electron transfer rate. According to the differential pulse voltammetry detection results, Ni15/MPC/GCE displays satisfactory detection limit (1.8 µM) and far wider detection concentration range (170 ∼ 10000 µM) than other reported electrochemical sensors. Moreover, Ni15/MPC/GCE exhibits acceptable stability and reproducibility, and the relative standard deviation of NP detection current is only 0.71% under the interference of 100-fold concentration interfering substances. Hence, the constructed Ni15/MPC/GCE demonstrates a promising electrochemical sensor for detecting NP in environmental sewage.

Nanoengineered Carbon Surfaces for Ultrasensitive Neurochemical Detection

Hypothesis-driven methods to tailor the functionality, topology, carbon orientation, and three-dimensional (3D) structure of carbon microelectrodes, for specific classes of neurochemicals, would significantly improve analyte specificity and lower the limits of detection for fast-scan cyclic voltammetry (FSCV) detection in the brain and beyond. FSCV at carbon-fiber microelectrodes is an established technique to study the signaling dynamics of many different neurochemicals in the brain. Despite its widespread applicability to many analytes, most in vivo studies are conducted on bare, unmodified carbon-fiber microelectrodes and many of the fundamental studies of new electrode materials focus on dopamine detection. Manipulations of the carbon surface can have profound effects on electrochemical detection and carefully controlled experiments to manipulate the analyte-electrode interface could provide exquisite information for future design of electrode materials. Here, we will discuss our latest work on synthesizing and manipulating the surfaces of carbon-based materials including graphene-based fibers and porous PAN-derived carbon-fiber, to exploit specific neurochemical-electrode interactions for improved detection. This presentation will demonstrate the importance of understanding the analyte-structure-electrode-surface interface for designing optimal electrodes.

Fabrication of Carbon Nanofiber Incorporated with CuWO4 for Sensitive Electrochemical Detection of 4-Nitrotoluene in Water Samples

In the current work, copper tungsten oxide (CuWO4) nanoparticles are incorporated with carbon nanofiber (CNF) to form CNF/CuWO4 nanocomposite through a facile hydrothermal method. The prepared CNF/CuWO4 composite was applied to the electrochemical detection of hazardous organic pollutants of 4-nitrotoluene (4-NT). The well-defined CNF/CuWO4 nanocomposite is used as a modifier of glassy carbon electrode (GCE) to form CuWO4/CNF/GCE electrode for the detection of 4-NT. The physicochemical properties of CNF, CuWO4, and CNF/CuWO4 nanocomposite were examined by various characterization techniques, such as X-ray diffraction studies, field emission scanning electron microscopy, EDX-energy dispersive X-ray microanalysis, and high-resolution transmission electron microscopy. The electrochemical detection of 4-NT was evaluated using cyclic voltammetry (CV) the differential pulse voltammetry detection technique (DPV). The aforementioned CNF, CuWO4, and CNF/CuWO4 materials have better crystallinity with porous nature. The prepared CNF/CuWO4 nanocomposite has better electrocatalytic ability compared to other materials such as CNF, and CuWO4. The CuWO4/CNF/GCE electrode exhibited remarkable sensitivity of 7.258 μA μM−1 cm−2, a low limit of detection of 86.16 nM, and a long linear range of 0.2–100 μM. The CuWO4/CNF/GCE electrode exhibited distinguished selectivity, acceptable stability of about 90%, and well reproducibility. Meanwhile, the GCE/CNF/CuWO4 electrode has been applied to real sample analysis with better recovery results of 91.51 to 97.10%.

Nafion modified electrochemical sensor integrated with a feedback-loop indium-gallium-zinc oxide thin-film transistor for enhancing dopamine detection limit

Though electrochemical (EC) biosensors have been widely used in various biomaterial analyses, stability issues associated with the experimental setup, background noise, and input/output signal fluctuation are still inevitably critical factors in determining sensor sensitivity and limit-of-detection (LOD). In this work, we propose a new biosensing setup that includes a typical EC biosensor, a TFT (thin-film transistor) and a constant current source. The integrated circuit provides negative feedback control to mitigate current fluctuations induced during the differential pulse voltammetry detection of the EC biosensor. Using dopamine (DA) molecules as the target analyte and electrodes modified with Nafion, our proposed integrated device shows a lower LOD than an EC sensor without TFT feedback.

Reticular synthesis of a conductive composite derived from metal-organic framework and Mxene for the electrochemical detection of dopamine

There is a great demand for the development of electrochemical sensors dealing with reagent-free detection of neurochemicals such as dopamine (DA). This study deals with the synthesis of a nanocomposite prepared from non-conductive [Zn4(btec)2(H2O)6]n·3nH2O (H4BTC = 1,2,4,5-benzene-tetra carboxylate) metal-organic framework (MOF) and titanium-based MXene (Ti3C2) as a conductive probe for the voltammetry detection of redox-active dopamine (DA). The electrochemical sensor for DA was prepared with a glassy carbon electrode (GCE) which is modified with a layer of nanocomposite (MOF–Ti3C2). The modified GCE was used for the detection of DA in the presence of ascorbic acid (AA) and 5-aminovaleric acid (VA) in PBS (0.1 M, pH; 6.5). The MOF-Ti3C2-based GCE demonstrated the detection limit of 110 nM for DA sensing in a linear concentration range (90–300 nM).

MPCVD-Grown Nanodiamond Microelectrodes with Oxygen Plasma Activation for Neurochemical Applications.

Nanodiamonds (NDs) are a carbon nanomaterial that has a diamond core with heteroatoms and defects at the surface. The large surface area, defect sites, and functional groups on NDs make them a promising material for electrochemical sensing. Previously, we dip-coated ND onto carbon-fiber microelectrodes (CFMEs) and found increases in sensitivity, but the coating was sparse. Here, we directly grew thin films of ND on niobium wires using microwave plasma chemical vapor deposition (MP-CVD) to provide full surface coverage. ND microelectrodes show a reliable performance in neurotransmitter detection with good antifouling properties. To improve sensitivity, we oxygen plasma etched ND films to activate the surface and intentionally add defects and oxygen surface functional groups. For fast-scan cyclic voltammetry detection of dopamine, oxygen plasma-etching increases the sensitivity from 21 nA/μM to 90 nA/μM after treatment. Fouling was tested by repeated injections of serotonin or tyramine, and both ND and plasma oxidized nanodiamond (NDO) microelectrodes maintain their currents better compared to CFMEs and therefore are more antifouling. A biofouling test in brain slices shows that ND microelectrodes barely have any current drop, while the more hydrophilic NDO microelectrodes decrease more, but still not as much as CFMEs. Overall, grown ND microelectrodes are promising in neurotransmitter detection with excellent fouling resistance, whereas oxygen plasma etching slightly lowers the fouling resistance but dramatically increases sensitivity.

Sustainable architecting of Co2SnO4/CE-BN-based electrochemical platform for highly selective and ultrasensitive detection of 2-nitroaniline in life samples.

A novel binary heterogeneous electrocatalyst, Co2SnO4, decorated on chemically exfoliated boron nitride sheets (CE-BN) with an exceptional capacity to detect electrochemical properties has been preparedby the simple hydrothermal method. The structural, surface morphology and electrochemical characteristics of Co2SnO4/CE-BN were characterized using a range of physicochemical and electrochemical techniques. Various voltammetric approaches were used to observe the analytical behaviour and applications of Co2SnO4/CE-BN/GCE for the determination of 2-nitroaniline (2-NA). The whole experiment is operated in the potential rangefrom 0 to - 1.0V vs Ag/AgCl (sat. KCl). The impact of operational factors on the peak current of 2-NA was investigated, including the pH, sample concentration, modifier amount and scan speed. With an estimated differential pulse voltammetry detection limit of 0.0371µM and excellent sensitivity of 1,35 µA µM-1cm-2, the produced sensor, Co2SnO4/CE-BN/GCE, revealed high electrocatalytic activity (DPV). The system is more practical and sustainable due to its repeatability, stability and reproducibility with respect to the results achieved for detection of 2-NA. The synthesized Co2SnO4/CE-BN-modified sensor may thus be a likely choice for the detection of 2-NA in actual water sample analysis.

Flexible Glassy Carbon Multielectrode Array for In Vivo Multisite Detection of Tonic and Phasic Dopamine Concentrations.

Dopamine (DA) plays a central role in the modulation of various physiological brain functions, including learning, motivation, reward, and movement control. The DA dynamic occurs over multiple timescales, including fast phasic release, as a result of neuronal firing and slow tonic release, which regulates the phasic firing. Real-time measurements of tonic and phasic DA concentrations in the living brain can shed light on the mechanism of DA dynamics underlying behavioral and psychiatric disorders and on the action of pharmacological treatments targeting DA. Current state-of-the-art in vivo DA detection technologies are limited in either spatial or temporal resolution, channel count, longitudinal stability, and ability to measure both phasic and tonic dynamics. We present here an implantable glassy carbon (GC) multielectrode array on a SU-8 flexible substrate for integrated multichannel phasic and tonic measurements of DA concentrations. The GC MEA demonstrated in vivo multichannel fast-scan cyclic voltammetry (FSCV) detection of electrically stimulated phasic DA release simultaneously at different locations of the mouse dorsal striatum. Tonic DA measurement was enabled by coating GC electrodes with poly(3,4-ethylenedioxythiophene)/carbon nanotube (PEDOT/CNT) and using optimized square-wave voltammetry (SWV). Implanted PEDOT/CNT-coated MEAs achieved stable detection of tonic DA concentrations for up to 3 weeks in the mouse dorsal striatum. This is the first demonstration of implantable flexible MEA capable of multisite electrochemical sensing of both tonic and phasic DA dynamics in vivo with chronic stability.

Hexagonal plate-like NiO/ZnO for highly selective detection of antibiotic drugs in food and biological samples

An ultrasensitive platform is accessible for the selective detection of chloramphenicol (CLP) based on NiO/ZnO inclusion of higher electrical conductivity and surface area has promoted voltammetry detection. The NiO/ZnO material has been prepared through an eco-friendly co-precipitation (CPT) method at room temperature. Here, we have designed and synthesized an effective electrocatalyst of NiO/ZnO with an average size of approximately 55.04 nm through a one-step synthetic protocol. The potential utility of the developed electrode was proved by applying them to the analytical determination of CLP in real samples. The NiO/ZnO modified SPCE demonstrated a significantly higher electrocatalytic effect for CLP reduction, at the potential of – 0.62 V in pH 7.0. The calibration curve for CLP linear range is 0.05 μM – 418.5 μM, and the detection limit is low as 0.07 μM. It is concluded the NiO/ZnO electrode is an effective electrode mediator for the selective detection of CLP. The homogenous hexagonal plate-like NiO/ZnO modified SPCE showed exceptional performance for the CLP determination in real food samples (milk and honey) and biotic samples (human urine).

Improving the accuracy of stripping voltammetry detection of Cd2+ and Pb2+ in the presence of Cu2+ and Zn2+ by machine learning: Understanding and inhibiting the interactive interference among multiple heavy metals

The application of square-wave anodic stripping voltammetry (SWASV) for the accurate detection of Cd2+ and Pb2+ in soils presents tremendous challenges because of the poor anti-interference on the electrochemical interaction among multiple heavy metal ions (HMIs). To improve the SWASV detection accuracy, it is necessary to deeply understand the interactive interference among multiple ions and then propose an efficient method to inhibit the above interference. In this study, the two-dimensional correlation spectroscopy (2D-COS) method was employed to gain insight into the change degree and sequence in peak currents of various HMIs when subjected to the interference of Cu2+, Zn2+, Pb2+, and Cd2+. The 2D-COS results highlighted the severity and complexity of the interactive interferences that could not be comprehensively reflected by the limited information in stripping peak currents of HMIs. Therefore, the feature currents were mined, which contained abundant information about stripping voltammetry. Then, combining the feature currents with machine learning models, the study built the Feature-RF and Feature-SVR models that significantly improved the detection accuracies of Cd2+ and Pb2+ in the presence of Cu2+ and Zn2+. Finally, the proposed method was used to detect Cd2+ and Pb2+ concentrations in real soil extracts, yielding results close to those of the inductively coupled plasma mass spectrometry (ICP–MS) and recoveries close to 100%, validating its practicability. This study provides new insight into interactive interferences among multiple heavy metal ions in SWASV signals and a new method to improve the SWASV detection accuracy of HMIs in complex matrices.

Gadolinium Manganese Oxide Nanorod Catalyst via a Facile Hydrothermal Approach: Application for Voltammetric Sensing of Antibiotic Drug Rifampicin in Pharmaceutical and Biological Samples

This study constructs a rough-surfaced rod structure of gadolinium manganese oxide fabricated by a glassy carbon electrode (GMO NRs/GCE). The resulting nanostructure was applied as an efficient electrocatalyst for the antibiotic drug rifampicin (RIF) sensor. In addition to the crystal structure study by X-ray diffraction (XRD), morphology study by Field Emission Scanning Electron Microscope (FESEM), Transmission electron microscopy (TEM), and the functional group examined by Fourier transform infrared spectroscopy (FTIR), elemental state study by X-ray photoelectron spectroscopy (XPS). As-synthesized samples were characterized systematically by electrochemical methods including cyclic voltammetry (CV), differential pulse voltammetry detection (DPV), and electrochemical impedance spectroscopy (EIS). The improving electrochemical behaviors of GMO NRs could be ascribed to the outstanding electrocatalytic activity with the high surface area and good conductivity. Under the experimental conditions, the quantitative measurement of RIF resulted in a large and wide linear range of 0.15 to 136.15 μM, a low detection limit was calculated to be 0.071 μM. The sensor had good selectivity, reproducibility, and high stability. Importantly, the GMO NRs sensor was effectively applied to determine RIF in serum, urine, and pharmaceutical samples with satisfactory accuracy and recovery.

Electrochemical detection of eutylone using screen-printed electrodes: Rapid and simple screening method for application in forensic samples

In this work, the electrochemical detection of eutylone (EUT), a synthetic cathinone that has been widely used as an illicit stimulant drug is presented for the first time. The electrochemical behavior of EUT was studied using an unmodified glassy carbon electrode and a carbon graphite screen printed electrode (SPE-Gr), where two irreversible oxidation processes were exhibited at around +0.9 V and +1.2 V (vs Ag/AgCl). EUT determination was optimized in 0.1 mol dm−3 borate buffer solution (pH 10.0) at SPE-Gr using differential pulse voltammetry (DPV) detection. The proposed method provided a low LOD (0.33 μmol dm−3) for EUT detection in seized samples with a suitable stability of the electrochemical response using the same or different SPEs. Additionally, the reuse of SPE-Gr for EUT screening in seized samples was successfully demonstrated for many times, providing a low-cost method for application in forensics analysis. Interference studies were performed with other synthetic cathinones, adulterants and illicit drugs found with EUT, showing a good selectivity of the electrochemical response. Furthemore, the addition-recovery and identification studies in seized samples were close to 100 %. Results were confirmed by liquid cromatography mass spectrometry analyses. The analytical performance of the SPE-Gr with DPV suggests a great potential of the proposed method as an easy, fast and inexpensive screening of EUT in seized samples.

Multiplexed Anodic Stripping Voltammetry Detection of Heavy Metals in Water Using Nanocomposites Modified Screen-Printed Electrodes Integrated With a 3D-Printed Flow Cell.

In this study, we present multiplexed anodic stripping voltammetry (ASV) detection of heavy metal ions (HMIs)—As(III), Cd(II), and Pb(II)—using a homemade electrochemical cell consisting of dual working, reference and counter screen-printed electrodes (SPE) on polyimide substrate integrated with a 3D-printed flow cell. Working and counter electrodes were fabricated by the screen-printing of graphite paste while the Ag/AgCl paste was screen-printed as a reference electrode (Ag/AgCl quasi-reference electrode). The working electrodes were modified with (BiO)2CO3-reduced graphene oxide (rGO)-Nafion [(BiO)2CO3-rGO-Nafion] and Fe3O4 magnetic nanoparticles (Fe3O4MNPs) decorated Au nanoparticles (AuNPs)-ionic liquid (IL) (Fe3O4-Au-IL) nanocomposites separately to enhance HMIs sensing. Electrochemical detection was achieved using square wave ASV technique. The desired structure of the flow electrochemical cell was optimized by the computational fluid dynamic (CFD). Different experimental parameters for stripping analysis of HMIs were optimized including deposition time, deposition potential and flow rate. The linear range of calibration curves with the sensing nanocomposites modified SPE for the three metal ions was from 0–50 μg/L. The limits of detection (S/N = 3) were estimated to be 2.4 μg/L for As(III), 1.2 μg/L for Pb(II) and 0.8 μg/L for Cd(II). Furthermore, the homemade flow anodic stripping sensor platform was used to detect HMIs in simulated river water with a 95–101% recovery, indicating high selectivity and accuracy and great potential for applicability even in complex matrices.

Detection of prostate specific antigen in whole blood by microfluidic chip integrated with dielectrophoretic separation and electrochemical sensing

The efficient detection of cancer markers has faced many challenges, such as severe interference, complicated and time-consuming operation, low sensitivity and so on. In this paper, a microfluidic chip integrated with electrodes for dielectrophoretic (DEP) separation, microchannels for electrochemical nanoprobes binding and differential pulse voltammetry (DPV) detection was proposed for the sensitive and rapid detection of prostate specific antigen (PSA) in whole blood. The functional units, which could realize cell separation, PSA derivatization (binding of electrochemical nanoprobes), capture and detection, were integrated on the microfluidic chip. The well-designed V-shaped interdigital electrode arrays provided DEP separation for blood cells with efficiency as high as 98%. Particularly, DEP effect significantly improved the sensitivity of PSA detection and reduced the detection limit by two orders of magnitude. In order to achieve sensitive detection of PSA, binding of electrochemical nanoprobes and then DPV detection was selected and integrated following the DEP separation. A sandwich structure based on electrochemical nanoprobes and dual-aptamers for on-chip DPV detection was proposed, which included self-synthesized electrochemical nanoprobes bovine serum albumin/detection aptamer 2/polythionine@gold nanoparticles (BSA/Apt2/PThi@Au NPs), target PSA, and sensing interface 6-mercaptohexanol/capture aptamer 1/gold nanoparticles on gold electrode (MCH/Apt1/Au NPs/Au). The method of quantitative detection of PSA in whole blood was then established. The excellent performance of the microfluidic chip allowed the determination of PSA in whole blood in the range of 1 pg/mL ∼10 ng/mL with an ultralow limit of detection of 0.25 pg/mL, which was better than the results obtained by conventional methods.

The fabrication of a highly electroactive chiral-interface self-assembled Cu(ii)-coordinated binary-polysaccharide composite for the differential pulse voltammetry (DPV) detection of tryptophan isomers

It is of significance to fabricate excellently performing chiral carbon nanocomposites for chiral electrochemical detection applications.