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A laser-scribed graphene (LSG) device fabricated on polymeric polyetherimide (PEI) substrate is reported for sensitive electrochemical detection of xylazine (XLZ), a veterinary drug that has been associated with drug-facilitated crimes. Morphological characterization was made by scanning electron microscopy (SEM), demonstrating that the electrochemical device presents a highly porous carbonaceous structure. In addition, Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), wettability, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) measurements were used to characterize the PEI-LSG material, which showed superior electroanalytical performance after a simple anodic treatment in an alkaline medium (applying 2 V for 120 s in 0.1 mol L−1 NaOH solution). The electrochemical determination of XLZ was carried out using square wave voltammetry (SWV), which showed sensitivity and coefficient of determination (R2) equal to 0.206 ± 0.008 A L mol−1 cm−2 and 0.991, respectively. In addition, we obtained a low limit of detection (LOD) of 1.39 × 10−7 mol L−1 with a linear response in the concentration range 5.0 to 200.0 × 10−6 mol L−1. The PEI-LSG electrochemical sensor was applied to XLZ detection in commercial beverage and synthetic urine samples, providing recoveries between 96.0 and 114.8%. Collectively, our electrochemical sensor presents an easy method to manufacture reproducible (relative standard deviation (RSD) of 2.56%), low-cost ($0.12), and single-use (disposable) devices, which is a promising way for in-field determination of drug-facilitated sexual assaults and other relevant applications. [ABSTRACT FROM AUTHOR]

This review proposes, for the first time, a recent overview of ecological information involving electrochemical paper-based analytical devices (ePADs) dedicated to sensing environmental and clinical situations. The options of manufacturing methods are screen printing, stencil printing, pencil drawing, laser scribing, inject-printing, and additive printing. We have covered ecological aspects such as resource efficiency, safety, and toxicity regarding using paper-based (bio) electrodes. To see the ecological impact of testing methods by using ePADs, the Analytical GREEnness (AGREE) approach was utilized as a greenness metric calculator model since the tool makes use of 12 principles of Green Analytical Chemistry. Positive and negative concepts from the revised values of AGREE metric of clinical and environmental analysis were introduced and discussed. Also, we finalize the present review informing the life cycle of ePAD and some challenges that can impact the next generation of disposable electrodes. • The greenness metrics involving paper-based electrochemical (bio)sensors have been reviewed. • Ecological impact for environmental and clinical analysis was introduced using the AGREE approach. • Resource efficiency, safety, and toxicity regarding using paper-based (bio)electrodes are discussed. • The life cycle and challenges that can impact the next generation of disposable electrodes are covered. [ABSTRACT FROM AUTHOR]

COVID-19 has led to over 3.47 million deaths worldwide and continues to devastate primarily middle- and low-income countries. High-frequency testing has been proposed as a potential solution to prevent outbreaks. However, current tests are not sufficiently low-cost, rapid, or scalable to enable broad COVID-19 testing. Here, we describe LEAD (Low-cost Electrochemical Advanced Diagnostic), a diagnostic test that detects severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within 6.5 min and costs $1.50 per unit to produce using easily accessible and commercially available materials. LEAD is highly sensitive toward SARS-CoV-2 spike protein (limit of detection = 229 fg·mL-1) and displays an excellent performance profile using clinical saliva (100.0% sensitivity, 100.0% specificity, and 100.0% accuracy) and nasopharyngeal/oropharyngeal (88.7% sensitivity, 86.0% specificity, and 87.4% accuracy) samples. No crossreactivity was detected with other coronavirus or influenza strains. Importantly, LEAD also successfully diagnosed the highly contagious SARS-CoV-2 B.1.1.7 UK variant. The device presents high reproducibility under all conditions tested and preserves its original sensitivity for 5 d when stored at 4 °C in phosphate-buffered saline. Our lowcost and do-it-yourself technology opens new avenues to facilitate high-frequency testing and access to much-needed diagnostic tests in resource-limited settings and low-income communities. [ABSTRACT FROM AUTHOR]

Aldehydes are relevant analytes in a wide range of samples, in particular, food and beverages but also body fluids. Hydrazines can undergo nucleophilic addition with aldehydes or ketones giving origin to hydrazones (a group of stable imines) that can be suitably used in the identification of aldehydes. Herein, 4-hydrazinobenzoic acid (HBA) was, for the first time, used as the derivatizing agent in analytical methodologies using liquid chromatography aiming the determination of low-molecular aldehydes. The derivatization reaction was simultaneously performed along with the extraction process, using gas-diffusion microextraction (GDME), which resulted in a clean extract containing the HBA-aldehyde derivates. The corresponding formed imines were determined by both high-performance liquid chromatography (LC) with UV spectrophotometric detection (HPLC-UV) and capillary electrophoresis with diode array detection (CE-DAD). HBA showed to be a rather advantageous derivatization reagent due to its stability, relatively high solubility in water and other solvents, high selectivity and sensibility, reduced impurities, simple preparation steps and applicability to different separation and/or different detection techniques. Limits of detections (LODs) of the optimized methodologies (in terms of time and pH among other experimental variables) were all below 0.5 mg L −1 , using both instrumental techniques. Furthermore, for the first time, the HBA-aldehyde derivatives were analyzed by LC with mass spectrometry (LC-MS), demonstrating the possibility of identification by MS of each compound. The developed methodologies were also successfully applied in the analysis of formaldehyde and acetaldehyde in several alcoholic beverages. This was also the first time GDME was combined with CE, showing that it can be a valuable sample preparation tool for electrophoresis, in particular by eliminating the interference of ions and inorganic constituents present in the samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gold nanoparticles were synthesized by cysteamine stabilization. • Gold nanoparticles functionalized with Creatine Phosphate (Pcrea) CK-MB. • CK-MB was successfully detected by Surface Plasmonic Resonance (SPR). • Low cost and rapid time of analysis achieved by the biosensor. • A sensitivity comparable with others biosensors was achieved. In this paper, we report a new biosensor for detection of the cardiac biomarker Creatine Kinase (CK-MB) using Surface Plasmon Surface (SPR) technique, with the purpose of the diagnosis of Acute Myocardial Infarction (AMI). For this, we employed gold nanoparticles (AuNP) stabilized with Cysteamine (Cys), and functionalized with Creatine Phosphate (Pcrea), which promote an increase in the sensitivity and accuracy for creatine kinase (CK-MB) detection in saliva and urine samples. The characteristics of the electronic transfer of the sensor could be observed by Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV), that showed significant redox peaks on electrode surface evidencing the high electron exchange process and low resistance charge transfer between the electrolyte solution and the modified surface. The morphological characteristics were confirmed by Atomic Force Microscopy (AFM), micro-Raman and Contact Angle (CA), as well as the adsorption and interaction processes between the materials, which could be observed by Surface Plasmon Resonance (SPR). The SPR analytical curve, ranged from 5.0 ng mL−1 to 100.0 ng mL−1, provided some important parameters, such as limit of detection (LOD) of 0.209 ng mL−1, limit of quantification (LOQ) of 0.696 ng mL−1, and sensitivity of 8.67 × 10–3 ± 0.17 × 10–3 (°) mL ng−1. The specific interaction between functionalized substrate and CK-MB demonstrates a high affinity of 15.14 ng mL−1 based on the Michaelis-Menten fitting. [ABSTRACT FROM AUTHOR]

A new method to manufacture electrochemical devices based on the graphite and colorless nail polish (N-grap) film was developed for tartrazine (Tz) detection. Scanning Electron Microscopy (SEM) demonstrates that the composite material presents a high porous carbon structure. Cyclic voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) were employed to electrochemically characterize the electrode material, which corroborates the porous structure of the N-graph due to the enhanced electroactive area (5.4-fold increase) and presented a heterogeneous electron transfer rate constant (k0) of 5.82 × 10−3 cm s−1 for potassium ferricyanide. The electrochemical determination of the Tz was carried out using square-wave voltammetry (SWV), under the optimized experimental conditions, which showed high sensitivity (0.793 A L mol−1) and a lower limit of detection (LOD) of 2.10 × 10−8 mol L−1 with a linear concentration ranging from 2.0 to 50.0 μmol L−1. The developed sensor was applied for the analysis of Tz in sports drink samples and the result obtained by N-grap device was statistically compared with a spectrophotometric method demonstrating good accordance and the accuracy of the proposed method. Based on these results, we believe that this new fabrication method to produce disposable and low-cost electrochemical devices can be an alternative method for in-field analysis of dye in commercial sport drink samples and other relevant applications. [Display omitted] • A simple method to fabricate disposable and low-cost electrochemical devices using graphite and nail polish is reported. • The composite material presented a porous carbon structure that exhibits high electron transfer kinetics. • The proposed sensor was successfully applied to the sensitive analysis of tartrazine (Tz) in sports drink samples. • The proposed method is reproducible, robust, accurate, and suitable for routine analysis. [ABSTRACT FROM AUTHOR]

The present study highlights the integration of lignin with graphene oxide (GO) and its reduced form (rGO) as a significant advancement within the bio-based products industry. Lignin-phenol-formaldehyde (LPF) resin is used as a carbon source in polyurethane foams, with the addition of 1 %, 2 %, and 4 % of GO and rGO to produce carbon structures thus producing carbon foams (CFs). Two conversion routes are assessed: (i) direct addition with rGO solution, and (ii) GO reduction by heat treatment. Carbon foams are characterized by thermal, structural, and morphological analysis, alongside an assessment of their electrochemical behavior. The thermal decomposition of samples with GO is like those having rGO, indicating the effective removal of oxygen groups in GO by carbonization. The addition of GO and rGO significantly improved the electrochemical properties of CF, with the GO2% sensors displaying 39 % and 62 % larger electroactive area than control and rGO2% sensors, respectively. Furthermore, there is a significant electron transfer improvement in GO sensors, demonstrating a promising potential for ammonia detection. Detailed structural and performance analysis highlights the significant enhancement in electrochemical properties, paving the way for the development of advanced sensors for gas detection, particularly ammonia, with the prospective market demands for durable, simple, cost-effective, and efficient devices. [ABSTRACT FROM AUTHOR]

• The LbL film was applied as electrochemical sensor for propylparaben (ProP). • Statistical method was used for comparison of the sensor with an analytical method. • The proposed sensor detected ProP in comestic samples. Electroanalytical detection of propylparaben (ProP) using gold nanoparticles-electrodeposited onto indium-tin-oxide electrode (AuNP-ITO) functionalized with PEI (poly(ethylene imine)) and NiTsPc (nickel(II) phthalocyanine tetrasulfonate) in the film (ITO-AuNPs-(PEI/NiTsPc) 3, was studied to verify the viability of a modified electrode (non-enzymatic) using Differential Pulse Voltammetry (DPV). It was possible to verify that gold nanoparticle-electrodeposited, which showed average diameters of 72.97 ± 1.60 nm, had electroactive area and increased conductivity with (ITO-AuNPs-(PEI/NiTsPc) 3 in comparison with and the electrode of bare ITO, ITO-(PEI/NiTsPc) 3 and ITO-AuNPs, according to Cyclic Voltammetry (CV). The response obtained by DPV in 0.1 mol L–1 PBS (pH 7.0) to detect ProP in cosmetic with a linear range from 2.0 to 20.0 × 10−6 mol L–1, the limit of detection (LD) obtained was 8.01 × 10−8 mol L−1 and 2.67 × 10−7 mol L−1 for the limit of quantification (LQ). Moreover, the sensor obtained the same performance when statistically compared to capillary electrophoresis (CE). [ABSTRACT FROM AUTHOR]

• Efficient LbL Film Based Voltage Detection Sensor (AuNP-PAH/NiTsPc) 5. • The composition of AuNp with NiTiPc makes highly stable and sensitive sensor for tartrazine detection. • Electrode accuracy was verified using a juice real sample. • The sensor demonstrates satisfying performances for the detection tartrazine. In this work, we report the analytical detection of tartrazine through differential pulse voltammetry (DPV) using gold nanoparticles (AuNPs) and Nickel(II)-phthalocyanine-tetrasulfonic (NiTsPc). The Layer-by-Layer (LbL) film was constructed following the Au-(AuNPs-PAH/NiTsPc) 5 architecture. The electric current characteristics of this sensor were verified by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). As a result of these measurements, a large and well-defined redox peak was obtained, indicating a significant enhancement in electron transfer. Excellent sensing performance was achieved with high sensitivity (25.79 ± 0.47 (µA cm−2) (µmol L−1)−1 and 8.80 ± 0.36 (µA cm−2) (µmol L−1)−1), low limit of detection (0.055 µmol L−1 and 0.122 µmol L−1), and excellent anti-interference and repeatability behavior. The Au electrode modified with the LbL film was also evaluated in commercially available juice samples with a recovery range from 97.74% to 108.26%. [ABSTRACT FROM AUTHOR]

• MeP is the most common paraben, its use can cause cancer and hormonal problems. • Side effects have been observed due to the bioaccumulation of these compounds. • Breast milk has an average of 22.0 μg L−1 of MeP. • Electrochemical sensor and the analytical method have very close results. The sustained use of cosmetics, hygiene products and medicines containing methylparaben (MeP) can be related to cases of cancer in women and children, which is why it is important to develop simple ways to monitor this compound. Gold electrodes were modified with Layer-by-Layer (LbL) films of magnetite nanoparticles (MNP) and polypyrrole (Ppy) for electrochemical determination of MeP. To investigate the synergistic effect between the MNP and Ppy, three different LbL architectures were tested: multilayers of Ppy with an conventional polycation poly(allylamine hydrochloride) – Au/(PAH/Ppy) 3 , MNP with a conventional polyanion poly(vinyl sulfonic acid) – Au/(MNP/PVS) 3 and the hybrid composite film Au/(MNP/Ppy) 3. The highest oxidation current and lowest oxidation potential were achieved by the Au/(MNP/Ppy) 3 electrode in a range up to 131.4 μmol L−1 with a limit of detection of 9.95 × 10−8 mol L−1. The performance of the electrochemical sensor was statistically investigated by the Miller-Miller method demonstrating accuracy comparable to an analytical method (capillary electrophoresis). MeP was determined in urine, breast milk and cosmetic with recovery values varying from 84.0% to 113.3%. [ABSTRACT FROM AUTHOR]

A portable and disposable laser-scribed graphene (LSG) device was fabricated on polyetherimide (PEI) substrate for electrochemical detection of benzodiazepines (BZ) drugs such as diazepam (DZ) and midazolam (MZ) in commercial beverage samples. Morphological characterizations of the LSG material recorded by scanning electron microscopy (SEM) revealed the porous nature of the proposed electrochemical device, which contributed to the enhancement of the electroactive area. Besides, the structural and electrochemical characterizations performed by Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements revealed that the PEI-LSG material presents highly disordered graphene-like structures and high electron transfer features, respectively. The electrochemical detection of DZ and MZ was carried out by Square Wave Voltammetry (SWV), whose analytical curves exhibited two linear intervals in concentrations ranging from 2.5 μmol L−1 to 25.0 μmol L−1 and from 25.0 μmol L−1 to 100.0 μmol L−1 for both BZ. We obtained limits of detection (LOD) and quantification (LOQ) of 0.66 and 2.18 μmol L−1 for DZ and 0.61 μmol L−1 and 2.01 μmol L−1 for MZ, respectively. The developed sensor was applied to detect DZ and MZ in commercial beverages such as juice, whisky, and sugarcane spirit samples to mimic potential forensic evidence of drug-facilitated crimes. The recoveries ranged from 97.1% to 117.2% for DZ and from 92.2% to 114.3% for MZ. In addition, the proposed method presented high manufacturing reproducibility (relative standard deviation (RSD) = 2.18% for DZ and RSD = 3.82% for MZ, n = 8 sensors) and adequate selectivity, highlighting the potential of PEI-LSG sensor as an excellent alternative method for forensic detection of crime facilitating drugs in commercial beverage samples. [Display omitted] • Reproducible and high-performance laser-scribed graphene (LSG) electrodes were fabricated. • A disposable and low-cost electrochemical sensor for determination of benzodiazepine drugs. • Our electrochemical sensor accurately detects diazepam and midazolam in beverage samples. • Portable and miniaturized device for forensic detection of crime facilitating drugs. [ABSTRACT FROM AUTHOR]