3D-printing is an emerging technique that enables the fast prototyping of multiple-use devices. Herein we report the fabrication of a 3D-printed graphene/polylactic acid (G-PLA) conductive electrode ...that works as a sampler and a voltammetric sensor of metals in gunshot residue (GSR) using a commercially-available G/-PLA filament. The 3D-printed surface was used as swab to collect GSR and next submitted to a square-wave voltammetric scan for the simultaneous detection of Pb2+ and Sb3+. The proposed sensor presented excellent analytical performance, with limit of detection values of 0.5 and 1.8 μg L−1 to Pb2+ and Sb3+, respectively, and linear ranges between 50 and 1500 μg L−1. Sampling was performed through the direct contact of G-PLA electrode in hands and clothes of shooters, followed by immersion in the electrochemical cell in the presence of supporting electrolyte for the SWASV scan. The proposed method showed a great performance in the recovery, identification and semi-quantification of Pb2+ and Sb3+ in the evaluated samples without the need for sample preparation. Moreover, the device can be reused as sampler and sensor (until three times without loss of electrochemical performance) and the fabrication is reproducible (RSD = 7%, for three different devices). Hence, this 3D-printed material is an excellent candidate for the analysis of GSR, an indispensable analysis in the forensic field.
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•3D-printed graphene/PLA for the simultaneous determination of lead and antimony.•The same 3D-printed platform as a sampler and a voltammetric sensor of gunshot residues.•No need of surface modification with mercury/bismuth for highly sensitive detection.•Gunshot residues were analyzed by swabbing the 3D-printed electrode for further detection.•Free from interference of Cd, Cu, Fe, Hg and Zn and higher inter-electrode precision (7%).
Although studies have demonstrated the inactivity of hydroxychloroquine (HCQ) towards SARS-CoV-2, this compound was one of the most prescribed by medical organizations for the treatment of ...hospitalized patients during the coronavirus pandemic. As a result of it, HCQ has been considered as a potential emerging contaminant in aquatic environments. In this context, we propose a complete electrochemical device comprising cell and working electrode fabricated by the additive manufacture (3D-printing) technology for HCQ monitoring. For this, a 3D-printed working electrode made of a conductive PLA containing carbon black assembled in a 3D-printed cell was associated with square wave voltammetry (SWV) for the fast and sensitive determination of HCQ. After a simple surface activation procedure, the proposed 3D-printed sensor showed a linear response towards HCQ detection (0.4-7.5 μmol L
) with a limit of detection of 0.04 μmol L
and precision of 2.4% (n = 10). The applicability of this device was shown to the analysis of pharmaceutical and water samples. Recovery values between 99 and 112% were achieved for tap water samples and, in addition, the obtained concentration values for pharmaceutical tablets agreed with the values obtained by spectrophotometry (UV region) at a 95% confidence level. The proposed device combined with portable instrumentation is promising for on-site HCQ detection.
This mini‐review presents an overview of recent trends for 3D printed sensors and biosensors (with a focus on Fused Deposition Modeling (FDM) based technology), along with their posttreatment ...surfaces to improve electrochemical applications. The protocols described in the literature and advances in this field were covered, bringing a critical discussion about the achievements and limitations to improve the electrical properties of conducting filaments, as well as their electroanalytical performance. In addition, the pros and cons of the processes used in surface posttreatment to improve the performance of electrodes constructed by FDM are presented, comparing the time consumed during chemical and electrochemical treatments or combining the two to improve the characteristics of the sensors. Finally, the discussion about the real necessity of surface treatments of electrodes constructed by FDM technology, the techniques used for this, and some ecological protocols are discussed (surface posttreatments with and without reagents) or whether the simple optimization of printing parameters could also significantly improve the electrochemical performance of sensors built with such technologies.
1-(3-chlorophenyl) piperazine (mCPP) is a synthetic drug with hallucinogenic effects that has often been found in seized samples. In this context, easy to use point-of-care tests can be of great ...value in preliminary forensic analysis. Herein, we proposed a simple, fast, and portable electrochemical method for the detection of mCPP in seized samples. The method is based on the use of disposable screen-printed carbon electrodes (SPCE) and rapid screening procedures by square-wave voltammetry using minimal sample sizes (100 μL). mCPP showed an irreversible electrochemical oxidation process at +0.65 V on SPCE (vs Ag) using 0.04 mol L−1 Britton Robinson (BR) buffer solution (pH 7) as the supporting electrolyte. The proposed method exhibited a linear correlation (r = 0.998) between peak current and mCPP concentration in the range of 1–30 μmol L−1 (LOD = 0.1 μmol L−1). Interference studies were performed for adulterants and other classes of drugs of abuse, which can also be found in seized samples containing mCPP, such as caffeine, amphetamine, methamphetamine, 1-benzylpiperazine, 3,4-methylenedioxymethamphetamine, methylone, mephedrone, ethylone and 3, 4-methylenedioxypyrovalerone. The developed method presents great potential as a rapid and simple screening tool to detect mCPP in forensic samples.
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•Portable electrochemical method for forensic applications.•The proposed method requires simple sample preparation procedure (dissolution and dilution in electrolyte).•Fast and simple screening test.
•Nanoporous gold structures electrochemically formed at the gold microelectrodes.•Increase in electroactive area (4.4-fold), decrease in resistance to charge transfer.•Energy-dispersive X-ray proves ...the formation of gold oxide nanostructures.•Improved amperometric detection of dipyrone and cysteine by batch-injection analysis.•Stripping voltammetric detection of lead ions was also improved.
In this paper, we investigate the effect of electrochemical treatment on the surface of low-cost and disposable devices (microchips) containing gold microelectrode arrays (Au-µE). This procedure consisted of electrode anodization to generate nanoporous gold structures (NPAu-μE), which contributed to 4.4-fold increase in the electroactive area and decrease in the resistance to charge transfer. Energy-dispersive X-ray spectra revealed the formation of gold oxide nanostructures. The electrochemical response of these sensors was properly investigated using dipyrone (DIP), cysteine (CyS) and lead(II) as target species, and for all the analytes, enhanced analytical performances were obtained using the treated surface. NPAu-μE was combined with a batch-injection analysis (BIA) cell for the amperometric determination of DIP and CyS, which resulted in detection limits lower than 1.2 µmol L-1, adequate precision (RSD > 4.0 %), wide linear ranges (1.0–200.0 and 5.0–150.0 µmol L−1), and high sample throughput (148 and 185 analysis per hour) for DIP and CyS, respectively. Moreover, the NPAu-µE sensor proved to be suitable for Pb2+ detection by square-wave anodic stripping voltammetry (SWASV), with a detection limit of 2.0 nmol L-1, linear ranges from 24 to 240 nmol L-1, and 289 to 531 nmol L-1, and good precision (RSD = 4.3 %), which enabled a good recovery of Pb2+ added to drinking water at the level corresponding to the WHO allowed threshold limit (48.2 nmol L-1 or 10.0 µg L-1). In summary, we demonstrate that NPAu-μE device can be applied for either organic or inorganic species with satisfactory sensing properties.
•3D printed thermoplastic electrodes produced by fused deposition modeling (FDM).•3D printing parameters affect the electrochemistry of the printed electrodes.•Proof-of-concept using carbon ...black/polylactic acid filament.•Printing orientation, layer thickness, perimeter and speed are evaluated.•Electrochemical and Raman spectroscopy data revealed the best printing conditions.
Thermoplastic filaments containing conductive carbon materials have contributed tremendously to innovations in the scientific scenario, however, the high charge transfer resistance of available materials sets a challenge for the development of 3D-printed electrochemical sensors. To solve this problem, several research groups have proposed chemical and physical post-treatments that are time-consuming and affect the structural integrity of materials. Herein, we systematically investigated the influence of printing parameters (orientation, layer thickness, number of perimeters and printing perimeter speed) on the electrochemical performance of sensors. For these studies, 3D-printed electrodes (rectangular shape) were printed using an affordable filament of carbon black integrated in polylactic acid (CB/PLA), and measurements by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) using 10 mmol/L Ru(NH3)62+/3+ as redox probe were performed. The results showed that electrodes printed under vertical orientation, with lower layer thickness (0.05 mm) and print perimeter speed (30 mm s−1) using two perimeter numbers provided the best electrochemical performance (faradaic peak current intensity and lower peak-to-peak separation). To understand the improvement of electrochemical responses, experiments by Raman spectroscopy and multivariate curve resolution by alternating least squares (MCR-ALS) were carried out which showed greater availability and distribution of conducting sites under the selected conditions. Thus, it can be inferred that 3D-printing parameters are important features to allow the manufacture of improved carbon electrochemical platforms.
A rapid and simple method for the amperometric determination of glucose using a nanocomposite film of nickel oxyhydroxide and multi-walled carbon nanotube (MWCNTs) was evaluated. The NiHCF)/MWCNT ...electrode film was fabricated using the liquid-liquid interface method, and it was used as a precursor for the electrochemical synthesis of nickel oxy-hydroxy (Ni(OH)
/NiOOH/MWCNT). The interaction between nickel oxy-hydroxy and the MWCNTs provided a film that is stable over the electrode surface, with high surface area and excellent conductivity. The nanocomposite presented an excellent electrocatalytic activity for the oxidation of glucose in an alkaline medium. The sensitivity of the sensor was found to be 0.0561 μA μmol L
, and a linear range from 0.1 to 150 μmol L
was obtained, with a good limit of detection (0.030 μmol L
). The electrode exhibits a fast response (150 injections h
) and a sensitive catalytic performance, which may be due to the high conductivity of MWCNT and the increased active surface area of the electrode. Additionally, a minimal difference in the slopes for ascending (0.0561 µA µmol L
) and descending (0.0531 µA µmol L
) was observed. Moreover, the sensor was applied to the detection of glucose in artificial plasma blood samples, achieving values of 89 to 98% of recovery.
To test the reliability and the discriminant and convergent validity of the abbreviated Brazilian Portuguese World Health Organization's Quality of Life Instrument - Spirituality, Religion, and ...Personal Beliefs module (WHOQOL-SRPB BREF).
In a sample of 404 individuals, we applied a general questionnaire, the WHOQOL-BREF, the long-form SRPB, the Brief Religious-Spiritual Coping Scale (RCOPE), and the Beck Depression Inventory (BDI). Priority was given to the 9-item SRPB assessment: its unidimensionality was tested through confirmatory factor analysis and Rasch analysis.
Confirmatory factor analysis of the 9-item SRPB assessment indicated an adjusted model with acceptable fit to data. In the Rasch analysis, general fit measures showed adequate performance. The 9-item SRPB assessment showed good internal consistency (alpha = 0.85), and could differentiate (discriminant validity) between religious and atheist/agnostic respondents (mean = 74.7±14.1 and 56.8±15.5, respectively; t = 6.37; degrees of freedom df = 402; p < 0.01) and between non-depressed and depressed respondents (mean = 76.5±12.9 and 67.1±16.5; t = 5.57; df = 190.5; p < 0.01). Correlations (convergent validity) were significant with the positive-RCOPE subscale (r = 0.58, p < 0.01) and the WHOQOL-BREF domains (Pearson coefficient ranging between 0.24 and 0.49; p < 0.01), but were in the negative direction with the negative-RCOPE subscale (r = -0.10, p < 0.05). Correlation with the long-form SRPB domain (r = 0.934) was almost perfect.
The Brazilian Portuguese 9-item SRPB has good psychometric properties and confirmed the findings of the long-form Brazilian Portuguese version and the abbreviated English version.
The determination of organic and inorganic compounds in a single run is still a great challenge. In this paper, we developed a method for fast simultaneous determination of ascorbic acid (AA) and ...zinc ions (Zn) using batch injection analysis with detection by square‐wave anodic stripping voltammetry (BIA‐SWASV). Britton‐Robinson (BR) buffer solution (pH=6.0) as the supporting electrolyte and boron doped diamond (BDD) as the working electrode. The method presented favorable analytical characteristics such as fast response (67 injections h−1), low detection limits (0.2 and 5.4 μmol L−1 for Zn ions and AA, respectively) and recovery values of 99±3%.
•Disposable sensor with great potential for forensic and on-site applications.•Minimal sample volume requirement (50–100 µL).•Portable electrochemical method.•Simple screening test.
...1-Benzylpiperazine (BZP) is an illegal synthetic drug commonly used in combination with alcoholic beverages for recreational purposes due to its amphetamine-like stimulant and hallucinogenic effects. In this work, we described a simple, portable and low-cost electrochemical method for BZP determination in beverage (vodka, whisky and white wine) and seized street samples. The electrochemical behavior of BZP was investigated by differential pulse voltammetry (DPV) and cyclic voltammetry (CV) using a screen-printed carbon electrode (SPCE), where a single irreversible oxidation processes was presented at around +0.7 V (vs. Ag pseudo reference). An electrochemical mechanism for BZP oxidation at SPCE was proposed. The quantification of BZP in beverage samples was optimized by the DPV technique in 0.12 mol L−1 Britton Robison buffer solution (pH = 5.0) using a drop-casting method of small sample volume (~100 μL) on SPCE. The proposed method showed a good linear range for BZP determination from 1 to 75 μmol L−1 with a low limit of detection (0.3 μmol L−1) and recovery values between 90 and 102%. Additionally, interference studies for other synthetic drugs from piperazine class and for other drugs commonly found in combination with BZP, such as 3,4-methylenedioxymethamphetamine (ecstasy), caffeine and synthetic cathinones, were performed. The analytical performance of the SPCE for detection of BZP in beverage and seized samples presents great potential for a simple and rapid screening method in forensic analysis.
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