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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]

Abstract This current review article focuses on recent contributions to on-site forensic investigations. Portable and potentially portable methods are presented and critically discussed about (bio)chemical trace analysis and studies performed outside the controlled laboratory environment to rapidly help in crime scene inquiries or forensic intelligence purposes. A wide range of approaches including electrochemical sensors, microchip electrophoresis, ambient ionization on portable mass spectrometers, handheld Raman and NIR instruments as well as and point-of-need devices, like paper-based platforms, for in-field analysis of latent evidences, controlled substances, drug screening, hazards, and others to assist in law enforcements and solving crime more efficiently are highlighted. The covered examples have successfully demonstrated the huge potential of portable devices for on-site applications. Future investigations should consider analytical validation to compete equality and even replace current gold standard methods. Graphical abstract Image 1 Highlights • Electrochemical sensors offer good sensitivity for abuse drugs and explosives. • Paper-based devices have revealed desirable performance for point-of-care testing. • NIR and RAMAN instruments have allowed fast screening at the point-of-need. • Portable MS instruments have exhibited good performance for on-site forensic applications. • Electrophoresis chips have provided excellent ability for STR genotyping. [ABSTRACT FROM AUTHOR]

An office paper-based colorimetric device is proposed as a portable, rapid, and low-cost sensor for forensic applications aiming to detect phenacetin used as adulterant in illicit seized materials such as cocaine. The proposed method uses white office paper as the substrate and wax printing technology to fabricate the detection zones. Based on the optimum conditions, a linear analytical curve was obtained for phenacetin concentrations ranging from 0 to 64.52 µg mL ‒1 , and the straight line was in accordance with the following equation: (Magenta percentage color) = 1.19 + 0.458 (C Phe /µg mL ‒1 ), R 2 = 0.990. The limit of detection was calculated as 3.5 µg mL ‒1 (3σ/slope). The accuracy of the proposed method was evaluated using real seized cocaine samples and the spike-recovery procedure. [ABSTRACT FROM AUTHOR]

A single-step laser scribing process is used to pattern nanostructured electrodes on paper-based devices. The facile and low-cost technique eliminates the need for chemical reagents or controlled conditions. This process involves the use of a CO2 laser to pyrolyze the surface of the paperboard, producing a conductive porous non-graphitizing carbon material composed of graphene sheets and composites with aluminosilicate nanoparticles. The new electrode material was extensively characterized, and it exhibits high conductivity and an enhanced active/geometric area ratio; it is thus well-suited for electrochemical purposes. As a proof-of-concept, the devices were successfully employed for different analytical applications in the clinical, pharmaceutical, food, and forensic fields. The scalable and green fabrication method associated with the features of the new material is highly promising for the development of portable electrochemical devices. [ABSTRACT FROM AUTHOR]

A single-step laser scribing process is used to pattern nanostructured electrodes on paper-based devices. The facile and low-cost technique eliminates the need for chemical reagents or controlled conditions. This process involves the use of a CO2 laser to pyrolyze the surface of the paperboard, producing a conductive porous non-graphitizing carbon material composed of graphene sheets and composites with aluminosilicate nanoparticles. The new electrode material was extensively characterized, and it exhibits high conductivity and an enhanced active/geometric area ratio; it is thus well-suited for electrochemical purposes. As a proof-of-concept, the devices were successfully employed for different analytical applications in the clinical, pharmaceutical, food, and forensic fields. The scalable and green fabrication method associated with the features of the new material is highly promising for the development of portable electrochemical devices. [ABSTRACT FROM AUTHOR]

We report the development of a simple, portable, low-cost, high-throughput visual colorimetric paper-based analytical device for the detection of procaine in seized cocaine samples. The interference of most common cutting agents found in cocaine samples was verified, and a novel electrochemical approach was used for sample pretreatment in order to increase the selectivity. Under the optimized experimental conditions, a linear analytical curve was obtained for procaine concentrations ranging from 5 to 60 μmol L-1, with a detection limit of 0.9 μmol L-1. The accuracy of the proposed method was evaluated using seized cocaine samples and an addition and recovery protocol. [ABSTRACT FROM AUTHOR]

We report the development of a simple and accurate analytical method to detect aminopyrine in seized cocaine samples using a platinum electrode. The quantification of aminopyrine was performed using square wave voltammetry (SWV), where the peak current response was found to increase linearly with aminopyrine concentration over the range 100–1000 μmol L − 1 . The repeatability of the electrode response was determined to be 2.4% (n = 15), and the detection limit of the proposed method was estimated to be 22 μmol L − 1 (3σ/slope). The accuracy of the proposed method was evaluated comparing the measured aminopyrine concentration in seized cocaine sample to the value obtained by gas chromatography coupled to flame ionization detector (GC-FID). An addition and recovery protocol in seized cocaine samples was also performed. [ABSTRACT FROM AUTHOR]

A wearable electrochemical sensor for non-invasive monitoring of trace metals in human perspiration is described. The temporary tattoo-based printable stripping-voltammetric sensor has been applied for real-time monitoring of zinc in sweat using a bismuth/Nafion film electrode during physical activity. The Zn temporary tattoo sensor withstands repeated mechanical stress and displays a well-defined Zn response during on-body testing. Such a non-invasive stripping-voltammetric detection could be readily expanded to epidermal measurements of other relevant heavy metals. [ABSTRACT FROM AUTHOR]

Abstract: We report the development of a simple analytical method that offers reagentless sensing capabilities by using a copper sensor for monitoring melamine. In this method, the anodic dissolution of the copper electrode is initiated electrochemically to release copper ions, which form the melamine chloride copper ionic pair at the electrode surface. After this process, the melamine chloride copper ionic pair can be reduced electrochemically at the surface of the electrode and quantified under the optimized conditions. This protocol eliminates the necessity to contaminate the sample with a copper salt, making the method proposed herein more environmentally benign than other techniques. The elucidation of the electrochemical reduction process of the melamine copper ionic pair was investigated with an electrochemical quartz crystal microbalance (EQCM). The quantification of melamine in milk was performed using differential pulse voltammetry, where the peak current response was found to increase linearly with melamine concentration over the range 5–90μmolL−1. The repeatability of the electrode response was evaluated as 1% (n=20), and the detection limit of the proposed method was estimated to be 0.85μmolL−1 (3σ/slope). The accuracy of the proposed method was evaluated using milk samples and an addition and recovery protocol. [Copyright &y& Elsevier]

Abstract: Nitrate determination plays a very important role in the analysis of environmental samples. In this paper, an activation procedure for nitrate sensing using a modified copper electrode made from flat flexible cables in presence of a low amount of chloride is reported. The proposed method exhibits enhanced electrocatalytic behaviour in the reduction of nitrate compared to a bare copper electrode. The proposed method showed linear response for nitrate in the concentration range 10–1070μmolL−1, with a regression coefficient R 2 =0.999 (n =12) and a limit of detection of 1.8μmolL−1. According to the procedure based on the standard addition technique, the recovery values obtained were 93–103%, showing the accuracy of the proposed method. In addition, the proposed sensor was applied to the determination of nitrate in mineral water samples and the results are in good agreement (for a 95% confidence level according to the Student's t-test) with those obtained using the capillary electrophoresis procedure. [Copyright &y& Elsevier]

Abstract: A simple and fast electrochemical method for quantitative analysis of picric acid explosive (nitro-explosive) based on its electrochemical reduction at copper surfaces is reported. To achieve a higher sample throughput, the electrochemical sensor was adapted in a flow injection system. Under optimal experimental conditions, the peak current response increases linearly with picric acid concentration over the range of 20–300μmolL−1. The repeatability of the electrode response in the flow injection analysis (FIA) configuration was evaluated as 3% (n=10), and the detection limit of the method was estimated to be 6.0μmolL−1 (S/N=3). The sample throughput under optimised conditions was estimated to be 550 samplesh−1. Peroxide explosives like triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) were tested as potential interfering substances for the proposed method, and no significant interference by these explosives was noticed. The proposed method has interesting analytical parameters, environmental applications, and low cost compared with other electroanalytical methods that have been reported for the quantification of picric acid. Additionally, the possibility to develop an in situ device for the detection of picric acid using a disposable sensor was evaluated. [Copyright &y& Elsevier]

We report on the photoconductivity and the photoelectric conversion measured on a thin photorefractive sillenite crystal plate, between transparent electrodes, in the longitudinal configuration where the current is measured along the same direction of the light beam through the sample. Its behavior is based on the already reported light-induced Schottky effect. The wavelength for optimal photoconductivity is determined. A specific parameter is formulated here for quantitatively determining the photoelectric conversion efficiency of the sandwiched material. [ABSTRACT FROM AUTHOR]

This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness 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]

This study describes the development of a simple, disposable, and eco-friendly electrochemical immunosensor for rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Electrochemical devices were manufactured by stencil-printing using low-cost materials such as polyester sheets, graphite flakes, and natural resin. The immunosensor comprises gold nanoparticles stabilized with cysteamine, glutaraldehyde, anti-SARS-CoV-2 S protein monoclonal antibody (Ab1) as the biological receptor, and bovine serum albumin as a protective layer. The COVID-19 diagnostic was based on rapid square wave voltammetry measurements (15 min) using [Fe(CN) 6 ]3-/4- as a redox probe. The method presented a linear response in the concentration range from 250 pg mL−1 to 20 μg mL−1 S protein, with a limit of detection of 36.3 pg mL−1. The proposed immunosensor was stable for up to two weeks when stored at 4 °C and it demonstrated excellent clinical performance in diagnosing COVID-19 when applied to a panel of 44 undiluted swab samples collected from symptomatic patients. In comparison with results obtained through the quantitative reverse transcription polymerase chain reaction method, the proposed immunosensor offered 100 % accuracy, thus emerging as a powerful alternative candidate for routine and decentralized testing, which can be helpful in controlling the COVID-19 outbreak. [Display omitted] • A novel electrochemical immunosensor for rapid detection of SARS-CoV-2 was developed. • Stencil-printed electrochemical sensors were manufactured using polyester sheets, graphite flakes, and natural resin. • A linear behavior was observed in the S protein concentration range from 250 pg mL−1 to 20 μg mL−1. • 44 undiluted swab samples collected from symptomatic patients were successufully analyzed. • A 100 % accuracy was achieved when compared with the results obtained by RT-qPCR. [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]

Abstract: Since the development of batch‐injection analysis (BIA) in 1990, the technique has been constantly upgraded, especially for electrochemical systems, including the creation of novel cell designs and association with new accessories to cover a wide range of applications. BIA systems have provided faster, portable, and more precise analyses. In addition, application of new materials as working electrodes provide improvement on sensitivity and selectivity, resulting in unique advantages for such analytical systems. This review focuses on the most recent advances of BIA systems, including the evolution of designs and materials used to construct BIA cells, with special emphasis to novel materials applied for improved electrochemical sensing. Modified electrodes with inorganic and organic nanomaterials on different substrates, including disposable platforms (screen‐printed electrodes and paper‐based devices) are highlighted. Boron‐doped diamond electrodes (BDDE), carbon‐nanotube and graphene‐modified electrodes have been combined with BIA systems for a wide range of applications that demand on‐site analyses. [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]

This study describes the development of electrochemical paper-based analytical devices (ePADs) using carbon-based paste combining silicone glue and graphite powder. The ePADs were manufactured using the screen-printing technique, which consisted of depositing the conductive ink on a screencast on the paper surface. In addition, an alternative electrical connector was designed and 3D-printed to make the detection method cheaper, portable and reproducible. The morphological, structural, and electrochemical properties of the conductive material developed were investigated through scanning electron microscopy (SEM), Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) measurements. The ePADs combined with the alternative connector revealed high repeatability, reproducibility, and stable responses considering a well-known redox probe ([Fe(CN) 6 ]4-/3-). In addition, the proposed ePAD provided a linear response for standard solutions of ascorbic acid (AA) in the concentration range between 0.1 and 2.0 mmol L−1. The achieved limit of detection was 4.0 μmol L−1. As proof of applicability, the ePADs were evaluated for AA analysis in synthetic biofluids (blood plasma and urine), vitamin C tablets, and food (gelatine and orange juice) samples. The analytical parameters of the proposed device were compared with other reports in the literature and exhibited similar or even superior performance, highlighting its feasibility for sensing applications. [Display omitted] • A carbon-based ink prepared by mixing graphite powder and silicone glue was used to develop screen-printed electrodes on paper. • An inexpensive 3D printed holder ensured simple assembling and suitable reproducibility. • Paper-based sensors revealed great stability and analytical performance. • Ascorbic acid was successfully determined in different samples. [ABSTRACT FROM AUTHOR]

Paper-based microfluidic devices have emerged as powerful platforms for bioanalysis offering advantages over other substrate materials including simpler fabrication protocols, compatibility with multi-purpose detectors, and global affordability. This review presents and discusses important information related to manufacturing methods, integrative sensing materials, the clinical relevance of biomarkers and bioanalysis. Examples of applications involving invasive and non-invasive samples, such as human serum, plasma, saliva, sweat, and urine are highlighted. Also, this review covers examples of (bio)sensing applications including the detection of viruses, microorganisms, neurodegenerative, cancer, diabetes, and allergic diseases. Lastly, the review summarizes recent examples of paper-based wearable devices and hybrid sensors dedicated to clinical applications and challenging points that can be carefully observed for the next generation of paper-based microfluidic sensors. • Microfluidic paper-based devices open new opportunities for bioanalysis. • Fabrication approaches and an overview of the recent devices were discussed. • The proposed review focus was on clinical relevance biomarkers in real samples. • The challenge of the paper devices was discussed to aim at wearable technologies. [ABSTRACT FROM AUTHOR]

Because oral transmission of SARS-CoV-2 is 3–5 orders of magnitude higher than nasal transmission, we investigated debulking of oral viruses using viral trap proteins (CTB-ACE2, FRIL) expressed in plant cells, delivered through the chewing gum. In omicron nasopharyngeal (NP) samples, the microbubble count (based on N-antigen) was significantly reduced by 20 μg of FRIL (p < 0.0001) and 0.925 μg of CTB-ACE2 (p = 0.0001). Among 20 delta or omicron NP samples, 17 had virus load reduced below the detection level of spike protein in the RAPID assay, after incubation with the CTB-ACE2 gum powder. A dose-dependent 50% plaque reduction with 50–100 ng FRIL or 600–800 μg FRIL gum against Influenza strains H1N1, H3N2, and Coronavirus HCoV-OC43 was observed with both purified FRIL, lablab bean powder or gum. In electron micrographs, large/densely packed clumps of overlapping influenza particles and FRIL protein were observed. Chewing simulator studies revealed that CTB-ACE2 release was time/dose-dependent and release was linear up to 20 min chewing. Phase I/II placebo-controlled, double-blinded clinical trial (IND 154897) is in progress to evaluate viral load in saliva before or after chewing CTB-ACE2/placebo gum. Collectively, this study advances the concept of chewing gum to deliver proteins to debulk oral viruses and decrease infection/transmission. [Display omitted] Twitter headline: Chewing gum neutralizing both SARS-CoV-2 and influenza viruses is advanced to clinical testing. [ABSTRACT FROM AUTHOR]

Advanced wound care technologies need to evolve in response to the growing burden of chronic wounds on national healthcare budgets and the debilitating impact chronic wounds have on patient quality of life. We describe here a new type of smart bandage for determination of uric acid (UA) status, a key wound biomarker, formed by screen printing an amperometric biosensor directly on a wound dressing. Immobilized uricase, paired with a printed catalytic Prussian blue transducer, facilitates chronoamperometric detection of uric acid at a low working potential. The smart bandage biosensor interfaces with a custom designed wearable potentiostat that provides on-demand wireless data transfer of UA status to a computer, tablet, or Smartphone by radio frequency identification (RFID) or near-field communication (NFC). The analytical performance of the smart bandage—sensitivity, selectivity, operational stability, and mechanical robustness—is described. Application of these bandages will provide insight into wound status and may reduce the frequency at which dressings are changed, allowing for healthcare cost savings and a reduction in patient stress and pain. [ABSTRACT FROM AUTHOR]

The preparation of fluorene(bisthiophene)-based fluorescent nanofibers for nitroaromatic explosive detection provides a convenient rapid and low-cost strategy aiming at forensic applications. Polycaprolactone (PCL) and fluorene(bisthiophene) derivative (FBT) nanofibers were obtained by electrospinning technique as a free-standing mat and characterized by SEM, FTIR, thermal analysis and fluorescence spectroscopy. The PCL/FBT nanofibers presented high sensitivity towards 2,4,6-trinitrotoluene (TNT) and picric acid (PA), with fluorescence quenching (turn-off mechanism), and selectivity to another kind of explosives. The free-standing mats were used as a cloth strip that was swiped on surfaces contaminated with TNT traces allowing its visual detection under UV light source. These findings are particularly important for the development of a facile and promising strategy to assembly portable optical devices for nitroaromatic explosive detection. [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]

Mental disorders like schizophrenia affect about 0.7% of the world population. Nowadays, the treatment consists of atypical antipsychotic drugs, mainly olanzapine and quetiapine. In this paper, we observed the chemical interaction between both olanzapine and quetiapine, antipsychotic drugs, with dopamine in phosphate buffer solutions at physiological pH using cyclic and differential voltammetry techniques, UV–Vis and EPR spectra. A solution containing both antipsychotic drugs and dopamine resulted in a shift of dopamine's redox processes, hindering its electrochemical oxidation. The chemical interaction was voltametrically investigated and a mechanism is proposed. In addition, it was observed that the reactions of both drugs with DA are first-order, presenting kinetic rate constants of 1.5 10−2 s−1 and 9.0 10−3 s−1 for olanzapine and quetiapine, respectively, at pH = 7.4. To further evaluate the chemical reaction, a minimalist model between PIPES molecule and catechol was proposed and tested. The model presented a similar signal decrease and kinetic rate constant to those observed for both olanzapine and quetiapine reaction with dopamine, reinforcing the data obtained which strongly suggests that the chemical reaction occurs between piperazine and catechol moieties. Unlabelled Image • Neurotransmitter dopamine reacts with antipsychotic drugs olanzapine and quetiapine; • The reaction occurs between the catechol and piperazine moieties from dopamine and the antipsychotics, respectively • A mechanism to the reactions involving both olanzapine and quetiapine with dopamine is proposed; • The reaction rate constants were obtained. [ABSTRACT FROM AUTHOR]