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.
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.
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•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.
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•Low-cost fused deposition modeling 3D-printed device for sampling and detection of TNT.•Graphene-doped polylacic acid (G-PLA) filament to fabricate the 3D-printed device.•Nanograms ...of TNT sampled from metallic, granite and glove surfaces were quantified.•Mechanical polishing of the 3D-printed surface improved the electrochemical properties.•Metal determination on the device was also shown; promising for gunshot residue analysis.
Fused deposition modelling 3D printing of a flexible, conductive, disposable and biodegradable platform using graphene-doped polylactic acid (G-PLA) was demonstrated as an integrated device for sampling and detection of explosives. As a proof-of-concept, traces of 2,4,6-Trinitrotoluene (TNT) impregnated on different surfaces were abrasively sampled using the 3D-printed device and readily assembled in a portable electrochemical cell for rapid square-wave voltammetry scans in the presence of 0.1 mol L–1 HCl electrolyte. Nanogram amounts of TNT sampled from metallic, granite and glove surfaces were detected and quantified using the Faraday equation applied to the voltammetric response of TNT immobilised on the electrode surface. Identification of TNT was possible due to the unique voltammetric behaviour obtained on the G-PLA sensor and efficient sampling due to the rough surface and flexibility of the device. Lead and copper determination by stripping voltammetry was also demonstrated on the same device, highlighting the possibility of detecting gunshot residues. Moreover, we demonstrated that simple mechanical polishing of the 3D-printed surface improved the electrochemical sensing properties of the sensor by exposing graphene nanoribbons within the PLA matrix. Hence, this 3D-printed integrated platform holds promise as a rapid and low-cost approach for on-site crime scene investigations.
The adulteration of whiskey with analgesics and sedation drugs has been a common practice to prevent hangover the following day and promote loss of consciousness. In both situations, the portable and ...low cost detection platforms are of paramount importance for forensic investigations. This report describes the use of electrochemical paper‐based analytical devices (ePADs) fabricated by pencil drawing for detecting metamizole, paracetamol and midazolam maleate in whiskey. Different types of paper substrates and graphite pencils were initially characterized with ferrocyanide. The best results were achieved using vegetal paper and Aquarelle/6B pencils. ePADs revealed a decrease in current signal indicating a short lifetime, thus limiting their use to disposable sensors. Despite the short lifetime, the graphite pencil ePADs revealed good electrochemical reproducibility (RSD=3.3 %). The forensic feasibility of the proposed ePADs was demonstrated through the analysis of metamizole and paracetamol in whiskey. The limit of detection (LOD) achieved for paracetamol and metamizole were 45 and 20 mg L−1, respectively. ePADs were also tested to detect midazolam maleate in whiskey. The signal recorded exhibited linear correlation in a wide concentration range (25–1000 mg L−1) and a LOD of ca. 5 mg L−1. Considering the disposability and operational simplicity, ePADs offer a good strategy for detecting adulterations in alcoholic beverages at the point‐of‐need.
The development of a portable analytical procedure is described for rapid sequential detection and quantification of the explosives 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) ...in forensic samples using a graphite sheet (GS). A single GS platform works as a collector of explosive residues and detector after its assembly into a 3D-printed cell. The detection strategy is based on cyclic square-wave stripping voltammetry. The cathodic scan from + 0.1 to −1.0 V with accumulation at 0.0 V enables the TNT detection (three reduction peaks), and the anodic scan from + 0.2 to + 1.55 V with accumulation at −0.9 V provides the RDX detection (two oxidation processes). Low detection limit values (0.1 µmol L
−1
for TNT and 2.4 µmol L
−1
for RDX) and wide linear ranges (from 1 to 150 µmol L
−1
for TNT and from 20 to 300 µmol L
−1
for RDX) were obtained. The sensor did not respond to pentaerythritol tetranitrate (PETN), which was evaluated as a potential interferent, because plastic explosives contain mixtures of TNT, RDX, and PETN. The GS electrode was also evaluated as a collector of TNT and RDX residues spread on different surfaces to simulate forensic scenarios. After swiping over different surfaces (metal, granite, wood, cloths, hands, money bills, and cellphone), the GS electrode was assembled in the 3D-printed cell ready to measure both explosives by the proposed method. In all cases, the presence of TNT and RDX was confirmed, attesting the reliability of the proposed device to act as collector and sensor.
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This study describes the development of a new electrochemical paper-based analytical device (ePAD) on alumina sandpaper substrate through a pencil-drawing process for square wave voltammetry ...measurements of midazolam maleate used as a “date rape drug” in beverages. The proposed ePAD was assembled on a reusable 3D printed holder to delimit its geometric area and ensure better robustness. The ePAD was characterized by scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and Raman spectroscopy. The direct drawing of ePADs on sandpaper platforms through a graphite pencil has offered suitable repeatability (RSD = 1.0%) and reproducibility (RSD = 4.0%) using Fe(CN)64– as redox probe. The proposed ePAD provided linear behaviour in the midazolam maleate concentration range between 2.5 and 150 mg L−1 and a limit of detection of 2.0 mg L−1. The feasibility of the ePAD for forensic application was successfully demonstrated through the detection of midazolam in different beverages (water, beer, liquor, and vodka). The intended application revealed low interference of other compounds present in beverages. Based on the achieved results, the proposed ePAD has offered great accuracy with no statistical difference at 95% confidence level from the data recorded by high performance liquid chromatography. The operational simplicity and the robustness ensured by the assembling on a reusable 3D printed holder make the ePAD drawn on sandpaper platform a powerful and promising analytical tool for the analysis of “date rape drugs” opening new possibilities for on-site forensic investigations.
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•Sandpaper substrate was explored to fabricate electrochemical devices through pencil drawing protocol.•ePADs were assembled on a reusable 3D-printed holder and covered with PDMS to define the geometric area.•The forensic feasibility was demonstrated through the detection of date rape drug.•The achieved results revealed good agreement with the data recorded using HPLC.•The proposed assembled device offered operational simplicity and an environmentally friendly strategy.
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•The electrochemical oxidation of cocaine in acid media is proposed for the first time.•Excellent selectivity for cocaine quantification.•Two methods for fast screening of common ...adulterants in cocaine seized samples.•Minimal sample manipulation (dissolution in electrolyte).
A simple and robust batch-injection analysis system with square-wave voltammetric (BIA-SWV) detection is proposed for the determination of cocaine and screening of the most common adulterants (benzocaine, caffeine, lidocaine, phenacetin, paracetamol, and procaine) in seized cocaine samples. The sample only requires a dissolution step in electrolyte (0.1molL−1H2SO4) prior injection into the BIA cell. SWV scanning is performed after injection of the sample plug and cocaine and adulterants are electrochemically oxidized on a boron-doped diamond electrode (BDDE), resulting in a unique voltammetric profile. The use of BDDE was essential to achieve, for the first time, the electrochemical oxidation of cocaine in an acid medium. Using the optimized experimental conditions, a linear response was found for cocaine concentrations ranging from 6 to 30mgL−1, with a detection limit of 0.27mgL−1 (0.89μmolL−1). The accuracy of the proposed method was estimated by comparing the results obtained for seized cocaine samples by GC-FID and with the addition and recovery protocol. Furthermore, BIA with multiple pulse amperometric (MPA) detection is also proposed as a promising protocol for faster screening of seized cocaine samples.
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%).
Scopolamine (SCP) is a psychoactive drug often added to beverages for recreational or abuse purposes (loss of memory and non‐consensual practices). In this work, a simple and portable method for fast ...in field screening of SCP in beverage (beer, coke, energy drink, sugarcane spirit, vodka, and whisky) and urine samples is presented. The proposed method is based on batch injection analysis with square wave voltammetric (BIA‐SWV) detection using boron‐doped diamond (BDD) as the working electrode. A voltammetric profile with accurate information on the presence or absence of SCP is obtained using a small sample volume (∼50 μL) and a simple sample pretreatment step (dilution in supporting electrolyte). Around two hundred analyses are possible using the proposed system (injection of single sample plug – 120 μL) without the need of electrodes handling or supporting electrolyte exchange (friendly to point‐of‐care or on site screenings). The quantification of SCP in beverages is also possible using the proposed portable protocol, with a limit of detection of 0.18 μmol L−1 and recovery values between 87 to 113 %.
Aqueous solutions containing the commercial azo dye Reactive Orange 122 (RO122) were ozonated in acid and alkaline conditions. Ozone was electrochemically generated using a laboratory-made ...electrochemical reactor and applied using semi-batch conditions and a column bubble reactor. A constant ozone application rate of 0.25
g
h
−1 was used throughout. Color removal and degradation efficiency were evaluated as function of ozonation time, pH and initial dye concentration by means of discoloration kinetics and COD–TOC removal. Experimental findings revealed that pH affects both discoloration kinetics and COD–TOC removal. A single pseudo-first-order kinetic rate constant,
k
obs, for discoloration was found for ozonation carried out in alkaline solutions, contrary to acidic solutions where
k
obs depends on ozonation time. COD–TOC removal supports degradation of RO122 is more pronounced for alkaline conditions. Evaluation of the oxidation feasibility by means of the COD/TOC ratio indicates that the ozonation process in both acid and alkaline conditions leads to a reduction in recalcitrance of the soluble organic matter.
