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.
•Fused deposition modeling 3D-printed electrode for (bio)sensors applied to real samples.•Enzymatic glucose biosensing on 3D-printed graphene-PLA electrode in plasma.•Oxygenated groups from PLA ...matrix favored enzyme immobilization by crosslinking.•Graphene-PLA 3D-printed electrochemical response improves after surface treatment.•Rapid and precise analysis of urine and saliva by pulsed amperometry using flow system.
Additive manufacturing, also known as 3D-printing, is receiving great interest by chemists due to the easy design of novel materials, fast prototyping and reducing waste, which enables large-scale fabrication of electrochemical devices. Herein we demonstrate the development of (bio)sensors for the analysis of biological fluids using 3D-printing. Fused deposition modelling was used to fabricate (bio)sensing platforms from commercially-available filaments made of polylactic acid containing graphene (G-PLA). An enzymatic glucose biosensor fabricated on the G-PLA surface was developed and applied for glucose sensing in blood plasma using chronoamperometry. Oxygenated groups from the polymeric matrix provides suitable condition to enzyme immobilization by crosslinking with glutaraldehyde. The biosensor presented a limit of detection (LOD) of 15 μmol L−1, inter-day and intra-day precision lower than 5 %, and adequate recovery values (90–105 %) for the analysis of plasma. We also show that the surface treatment of the 3D-printed sensor (mechanical polishing followed solvent immersion) provides improved electrochemical properties for the direct detection of nitrite and uric acid. Differential-pulse voltammetry and multiple-pulse amperometry under flow conditions were evaluated and compared for the determination of both species in saliva and urine. Highlights are presented for the amperometric detection within a linear range from 0.5–250 μmol L−1 for both analytes, LODs of 0.02 and 0.03 μmol L−1 for uric acid and nitrite, respectively, and high precision (RSD < 2.1 %). This report shows the first application of 3D-printed sensors and biosensors for the analysis of real biological samples with analytical features comparable to conventional modified electrodes.
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.
Additive manufacturing or three-dimensional (3D)-printing is an emerging technology that has been applied in the development of novel materials and devices for a wide range of applications, including ...Electrochemistry and Analytical Chemistry areas. This review article focuses on the contributions of 3D-printing technology to the development of electrochemical sensors and complete electrochemical sensing devices. Due to the recent contributions of 3D-printing within this scenario, the aim of this review is to present a guide for new users of 3D-printing technology considering the required features for improved electrochemical sensing using 3D-printed sensors. At the same time, this is a comprehensive review that includes most 3D-printed electrochemical sensors and devices already reported using selective laser melting (SLM) and fused deposition modeling (FDM) 3D-printers. The latter is the most affordable 3D-printing technique and for this reason has been more often applied for the fabrication of electrochemical sensors, also due to commercially-available conductive and non-conductive filaments. Special attention is given to critically discuss the need for the surface treatment of FDM 3D-printed platforms to improve their electrochemical performance. The insertion of biochemical and chemical catalysts on the 3D-printed surfaces are highlighted as well as novel strategies to fabricate filaments containing chemical modifiers within the polymeric matrix. Some examples of complete electrochemical sensing systems obtained by 3D-printing have successfully demonstrated the enormous potential to develop portable devices for on-site applications. The freedom of design enabled by 3D-printing opens many possibilities of forthcoming investigations in the area of analytical electrochemistry.
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•We review the contributions of 3D-printing to fabricate electrochemical sensors.•Different 3D-printing methods are compared highlighting fused deposition modeling (FDM).•Surface treatment and modification with (bio)chemical mediators for improved performance.•Strategies for fabrication of conductive filaments are presented for future applications.•3D-printing of all-in-one electrochemical devices in different designs are assessed.
This work shows that the electrochemical activity of a 3D-printed electrode fabricated using a conductive composite of polylactic acid (PLA) containing carbon black (CB) can be substantially improved ...through a simple and fast chemical/electrochemical pretreatment in 0.5 mol L−1 NaOH. Scanning electron microscopy and infrared spectroscopy data showed that the pretreatment process promotes the removal of the non-conductive PLA material, providing greater exposure of the conductive particles. Cyclic voltammetry of the redox probe ferricyanide/ferrocyanide indicated faster electron transfer on the treated 3D-printed surface and increase in electroactive area. Moreover, electrochemical impedance spectroscopic results also confirmed faster electron transfer after surface pretreatment. As a proof-of-concept, a low-cost and sensitive method for the determination of cadmium and lead in real urine and saliva samples by square-wave anodic stripping voltammetry was developed. The chemical/electrochemical treatment provided an impressive 30-fold current increase in the detection of both metals. Acceptable limits of detection (2.9 μg L−1 for Cd2+ and 2.6 μg L−1 for Pb2+), wide linear ranges for both metals (30 μg L−1 to 270 μg L−1; R = 0.997), high stability (RSD lower than 4.5%; n = 10), and adequate recovery values (between 93% and 112%) for the analysis of spiked samples were achieved. Additionally, interday (n = 3), intra-day (n = 3), inter-electrode (n = 2) and inter-treatment (n = 2) experiments revealed RSD values lower than 6.5%, which indicates high reproducibility of the proposed treated 3D-printed electrode. The strategy here proposed opens up new applications for 3D-printed electrode in analytical electrochemistry with improved electrochemical sensing properties in comparison to screen-printed electrodes.
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•Screen-printed gold electrodes for fuel bioethanol analysis.•Stripping voltammetric determination of Pb, Cu and Hg in fuel bioethanol.•Routine and on-site determination of metals in ...fuel bioethanol.•Promising applications of screen-printed electrodes for fuel analysis.
The potential application of commercial screen-printed gold electrodes (SPGEs) for the trace determination of lead, copper, and mercury in fuel bioethanol is demonstrated. Samples were simply diluted in 0.067molL−1 HCl solution prior to square-wave anodic stripping voltammetry (SWASV) measurements recorded with a portable potentiostat. The proposed method presented a low detection limit (<2μgL−1) for a 240s deposition time, linear range between 5 and 300μgL−1, and adequate recovery values (96–104%) for spiked samples. This analytical method shows great promise for on-site trace metal determination in fuel bioethanol once there is no requirement for sample treatment or electrode modification.
Trace amounts of copper decrease significantly the oxidative stability of biodiesel while antioxidants, mostly tert-butylhydroquinone (TBHQ), are commonly introduced to the biofuel to guarantee ...induction period values within regulatory limits. Hence, a simple method to monitor the most used antioxidant and the most deleterious contaminant in biodiesel can give a fast response on its quality. In this context, this work presents a simple, efficient, low cost and sensitive method for the simultaneous and direct determination of copper and the antioxidant TBHQ in biodiesel. The biodiesel samples were diluted in 90% (v/v) ethanol and 10% (v/v) water containing 0.1 mol L−1 HCl (final concentration) as the supporting electrolyte generating a homogeneous mixture in which Cu(II) and TBHQ were directly detected using the square wave voltammetry (SWV) on a gold working electrode. The presence of biodiesel in the selected electrolyte facilitated the separation of analyte peaks facilitating the treatment of data and quantification. The linear responses for the simultaneous determination were in the range between 5 and 100 μg L−1 and 4.2–81.5 mg L−1 for copper and TBHQ (R > 0.997), respectively. High precision (RSD = 4.0% and 3.9%, n = 20) and limit of detection (LOD) values of 0.31 μg L−1 and 1.0 mg L−1 (0.030 μg g−1 and 0.102 mg g−1 in biodiesel) for Cu(II) and TBHQ, respectively, were obtained. Recovery values between 97% and 104% for both copper and TBHQ were obtained.
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•Rapid method for simultaneous determination of copper and the antioxidant TBHQ in biodiesel.•Biodiesel aliquot 100-fold diluted in hydroethanolic electrolyte with 0.1 mol L−1 HCl in the cell.•The presence of biodiesel facilitated the separation of the voltammetric peaks of analytes.•LOD values of 0.030 μg g−1 and 0.102 mg g−1 in biodiesel for Cu(II) and TBHQ, respectively.•Fast protocol to identify metallic contaminants and attest the required presence of TBHQ.
Capillary electrophoresis (CE) methods have unique potential for applications in quality control of pharmaceutical formulations. Here, we show that a single and ultra-fast CE method can be used for ...the determination of hydrochlorothiazide (HCT) in combination with nine other active ingredients in a single run in different pharmaceutical samples: atenolol (ATE), metoprolol (MET), propranolol (PRO), benazepril (BEN), captopril (CAP), enalapril (ENA), lisinopril (LIS), ramipril (RAM), and valsartan (VAL). This goal was achieved using a single and simple background electrolyte (BGE) composed of 10 mmol L-1 of boric acid with pH adjusted to 9.0 with sodium hydroxide. All samples can be analyzed in less than 1 min with the attainment of good analytical performance, such as high-resolution separation (r > 1.3), low sample and reagents consumption (environmentally friendly method), low relative standard deviation (RSD) values for peak area (< 4.0%) and migration times (< 1.7%), and linear relationships with good correlation coefficients (> 0.995). Furthermore, recovery tests showed good results (100 ± 5%) for all evaluated compounds.
The fabrication of carbon black/polylactic acid (PLA) electrodes using a 3D printing pen is presented and compared with electrodes obtained by a desktop fused deposition modelling (FDM) 3D printer. ...The 3D pen was used for the fast production of electrodes in two designs using customized 3D printed parts to act as template and guide the reproducible application of the 3D pen: (i) a single working electrode at the bottom of a 3D-printed cylindrical body and (ii) a three-electrode system on a 3D-printed planar substrate. Both devices were electrochemically characterized using the redox probe Fe(CN)63−/4- via cyclic voltammetry, which presented similar performance to an FDM 3D-printed electrode or a commercial screen-printed carbon electrode (SPE) regarding peak-to-peak separation (ΔEp) and current density. The surface treatment of the carbon black/PLA electrodes fabricated by both 3D pen and FDM 3D-printing procedures provided substantial improvement of the electrochemical activity by removing excess of PLA, which was confirmed by scanning electron microscopic images for electrodes fabricated by both procedures. Structural defects were not inserted after the electrochemical treatment as shown by Raman spectra (iD/iG), which indicates that the use of 3D pen can replace desktop 3D printers for electrode fabrication. Inter-electrode precision for the best device fabricated using the 3D pen (three-electrode system) was 4% (n = 5) considering current density and anodic peak potential for the redox probe. This device was applied for the detection of 2,4,6-trinitrotoluene (TNT) via square-wave voltammetry of a single-drop of 100 μL placed upon the thee-electrode system, resulting in three reduction peaks commonly verified for TNT on carbon electrodes. Limit of detection of 1.5 μmol L−1, linear range from 5 to 500 μmol L−1 and RSD lower than 4% for 10 repetitive measurements of 100 μmol L−1 TNT were obtained. The proposed devices can be reused after polishing on sandpaper generating new electrode surfaces, which is an extra advantage over chemically-modified electrochemical sensors applied for TNT detection.
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•3D pen fabricated carbon black/polylactic acid electrodes compared with 3D-printed electrodes.•Morphological analysis shows no difference, except to electrochemical surface treatment.•Highly reproducible planar three-electrode devices were fabricated (RSD = 4%, n = 5).•Similar results to those obtained on 3D-printed or screen-printed electrodes.•Application to TNT detection in a single drop (100 μL placed upon the device).
Three-dimensional printing techniques have been widely used in the fabrication of new materials applied to energy, sensing and electronics due to unique advantages, such as fast prototyping, reduced ...waste generation, and multiple fabrication designs. In this paper, the production of a conductive 3D-printing filament composed of Ni(OH)2 microparticles and graphene within a polylactic acid matrix (Ni-G-PLA) is reported. The nanocomposite was characterized by thermogravimetric, energy-dispersive X-ray spectroscopic, scanning electronic microscopic, Raman spectroscopic and electrochemical techniques. Characteristics such as printability (using fused deposition modelling), electrical conductivity and mechanical stability of the polymer nanocomposite were evaluated before and after 3D printing. The novel 3D-printed disposable electrode was applied for selective detection of glucose (enzyme-less sensor) with a detection limit of 2.4 μmol L−1, free from the interference of ascorbic acid, urea and uric acid, compounds typically found in biological samples. The sensor was assembled in a portable electrochemical system that enables fast (160 injection h−1), precise (RSD < 5%) and selective determination of glucose without the need of enzymes (electrocatalytic properties of the Ni-G-PLA nanocomposite). The obtained results showed that Ni-G-PLA is a promising material for the production of disposable sensors for selective detection of glucose using a simple and low-cost 3D-printer.
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•Production of a conductive 3D-printing filament composed by nickel microparticles and graphene within a PLA matrix.•Fast 3D printing of disposable electrodes for selective detection of glucose (enzyme-less sensor).•Single step fabrication of electrodes modified with nickel nanoparticles.•Direct printing of modified electrodes.
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