This work presents potential applications of low-cost fused deposition modeling 3D-printers to fabricate multiuse 3D-printed electrochemical cells for flow or batch measurements as well as the ...3D-printing of electrochemical sensing platforms. Electrochemical cells and sensors were printed with acrylonitrile butadiene styrene (ABS) and conductive graphene-doped polylactic acid (G-PLA) filaments, respectively. The overall printing operation time and estimated cost per cell were 6 h and $ 6.00, respectively, while the sensors were printed within minutes (16 sensor strips of 1 × 2 cm in 10 min at a cost of $ 1.00 each sensor). The cell performance is demonstrated for the amperometric detection of tert-butylhydroquinone, dipyrone, dopamine and diclofenac by flow-injection analysis (FIA) and batch-injection analysis (BIA) using different working electrodes, including the proposed 3D-printed sensor, which presented comparable electroanalytical performance with other carbon-based electrodes (LOD of 0.1 μmol L−1 for dopamine). Raman spectroscopy and scanning electron microscopy of the 3D-printed sensor indicated the presence of graphene nanoribbons within the polymeric matrix. Electrochemical impedance spectroscopy and heterogeneous electron transfer constants (k0) for the redox probe Ru(NH3)6+3 revealed that a glassy-carbon electrode presented faster electron transfer rates than the 3D-printed sensor; however, the latter presented lower LOD values for dopamine and catechol probably due to oxygenated functional groups at the G-PLA surface.
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•Low-cost fused deposition modeling (FDM) 3D-printers to produce cells and electrodes.•Multiuse cells for flow- (FIA) and batch-injection analysis (BIA) as well for batch condition.•Designs and printing conditions accessible for any FDM 3D-printers.•Graphene-doped PLA printed sensors for voltammetric and amperometric detection.•Electroanalytical performance similar to GCE modified with carbon nanomaterials.
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.
Midazolam (MID) is a sedative drug which can be added in beverage samples as drug-facilitated-sexual assault (date rape drug). This type of drug has short half-life in biological fluids (not ...detectable) which often prevents the correlation between drug abuse and crime. In this work, we described a simple and low-cost method for fast screening and selective determination of MID in beverage samples (vodka, whiskey and red wine). For the first time, the electrochemical oxidation of MID was used for this purpose. The oxidation mechanism was studied using electrochemical techniques (cyclic and square-wave voltammetry) and computational simulations (density functional theory calculations). Differential-pulse voltammetry, boron-doped diamond electrode (BDDE), and Britton-Robinson (BR) buffer (pH = 2) were selected as electrochemical analysis technique, working electrode and supporting electrolyte, respectively. Different linear response ranges (4–25 μmol L−1 with r = 0.9972; 1–10 μmol L−1 with r = 0.9951; 1–15 μmol L−1 with r = 0.9982) and limits of detection (0.46, 0.43 and 0.33 μmol L−1) were obtained for the analysis of vodka, whisky, and red wine solutions, respectively. The precision and accuracy were satisfactory considering the low relative standard deviation values (RSD < 6.3%, n = 15) and minimal sample matrix effects (recovery values between 87 and 103%).
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•Fast screening and selective determination of midazolam.•The electrochemical oxidation of midazolam has been studied for the first time.•The electrochemical oxidation showed better selectivity than the electrochemical reduction.•The oxidation mechanism was proposed.
Herein, a compact batch injection analysis cell for screen printed electrodes (BIASPE cell) is reported. The proposed system shows several requirements of a portable system that include ...easy‐to‐operate (“user‐friendly”), high‐speed quantitative and qualitative analysis, excellent cost effectiveness, and low‐power requirements (all auxiliary components are battery‐powered). Similar to analytical microsystems, small volumes of samples (5 to 100 μL) are required for analysis, however, the robustness of the system here proposed is considerably higher. The combination of the BIASPE cell with battery‐powered accessories (electronic micropipette, potentiostat and tablet or laptop computer) can be considered as a robust portable electroanalytical system. Electrochemical methods with portable characteristics can be now easily developed.
This work presents a simple electrochemical method for 2-naphthylamine (2NAP) determination in perfume by differential-pulse voltammetry (DPV) employing a boron-doped diamond (BDD) electrode ...cathodically treated. Simple dilution of sample in supporting electrolyte was performed before electrochemical analysis. A borate buffer solution of pH 10.0 containing 20% (v/ (LOD) of 0.0046 µmol L-1 with a linear range between 0.5 and 90 µmol L-1, and RSD < 2.9%, respectively. Recovery values for spiked samples with 2NAP were between 102 and 104%. The proposed method is feasible to be applied for 2NAP detection and quantification on perfume samples with simple sample preparation.
This work presents a portable electrochemical system for the continuous monitoring of corrosion inhibitors in a wide range of matrices including ethanol, seawater and mineral oil following simple ...dilution of the samples. Proof-of-concept is demonstrated for the sensing of 2,5-dimercapto-1,3,5-thiadiazole (DMCT), an important corrosion inhibitor. Disposable screen-printed graphitic electrodes (SPGEs) associated with a portable batch-injection cell are proposed for the amperometric determination of DMCT following sample dilution with electrolyte (95% v/v ethanol + 5% v/v 0.1molL-1 H2SO4 solution). This electrolyte was compatible with all samples and the organic-resistant SPGE could be used continuously for more than 200 injections (100µL injected at 193µLs-1) free from effects of adsorption of DMCT, which have a great affinity for metallic surfaces, and dissolution of the other reported SPGE inks which has hampered prior research efforts. Fast (180h-1) and precise responses (RSD < 3% n = 10) with a detection limit of 0.3µmolL-1 was obtained. The accuracy of the proposed method was attested through recovery tests (93–106%) and the reasonable agreement of results of DMCT concentrations in samples analyzed by both proposed and spectrophotometric (comparative) methods.
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•Continuous sensing of a corrosion inhibitor on screen-printed graphitic electrodes.•Batch-injection analysis with organic-resistant electrodes for portable detection.•Ethanol, seawater and mineral oil samples analyzed after simple dilution.•High sample throughput (180h-1), RSD < 3% (n = 10) and low LOD (0.3µmolL-1).•Recovery tests (93–106%) and comparison with spectrophotometry attested accuracy.
Tibolone (TIB) is a synthetic steroid banned by the World Anti‐Doping Agency (WADA) due to its similar properties to estrogen and progesterone. In this work, a simple and low‐cost electrochemical ...method for the determination of TIB and its metabolites (3‐α hydroxytibolone and 3‐β hydroxytibolone) in authentic human saliva is reported. Square‐wave voltammetry (SWV) with an unmodified boron‐doped diamond (BDD) electrode and phosphate buffer 0.1 mol L−1 were selected as the electrochemical technique, working electrode, and supporting electrolyte, respectively. Analytical characteristics of the proposed method include good repeatability (RSD <2.4 %), wide linear range (1 to 110 μmol L−1; r=0.999) and low detection limit (0.3 μmol L−1). Average recovery values (104±3 % for TIB and 98±5 % for the metabolites) for direct analysis of spiked saliva samples (only diluted in supporting electrolyte) indicate that no significant matrix interference was observed. The proposed method was also efficient for the determination of TIB in pharmaceutical samples (statistically similar results to those obtained by HPLC).
Anti‐doping: The steroid tibolone is a synthetic steroid banned by the World Anti‐Doping Agency (WADA). In this work, a simple and low‐cost electrochemical method is reported for the first time for fast screening analysis of TIB and its metabolites (3‐α hydroxytibolone and 3‐β hydroxytibolone) in authentic human saliva samples using a boron‐doped diamond electrode and square‐wave voltammetry. The method has great potential to be used in anti‐doping analysis.
In this work, the performance of two methods for simultaneous determination of propyphenazone (PRO), paracetamol (PAR), and caffeine (CAF) were compared. One is based on the use of a conventional ...electrochemical cell (steady‐state condition) and the other on the use of a batch injection analysis (BIA) cell; both systems were associated with square‐wave voltammetric detection (SWV). Three well separated (▵E ≥ 0.25 V) oxidation peaks were obtained for PRO, PAR, and CAF using 0.1 mol L−1 H2SO4 as electrolyte and a boron‐doped diamond (BDD) as working electrode. In addition, the electrochemical oxidation mechanism of PRO is being proposed for the first time. The average relative standard deviations of CB and BIA methods were 4.1 % and 3.1 %, respectively. The conventional system presented better limits of detection and the BIA system a significantly greater throughput (four times faster). Statistical comparison between the results obtained with both proposed methods and those obtained by chromatography was carried out and no significant differences were observed (95 % confidence level).
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