3D-Printed Microdevices: From Design to Applications.

3D printing represents an emerging technology in several fields, including engineering, medicine, and chemistry [...].

A miniaturized additive-manufactured carbon black/PLA electrochemical sensor for pharmaceuticals detection.

Additive manufacturing is a technique that allows the construction of prototypes and has evolved a lot in the last 20 years, innovating industrial fabrication processes in several areas. In chemistry, additive manufacturing has been used in several functionalities, such as microfluidic analytical devices, energy storage devices, and electrochemical sensors. Theophylline and paracetamol are important pharmaceutical drugs where overdosing can cause adverse effects, such as tachycardia, seizures, and even renal failure. Therefore, this paper aims at the development of miniaturized electrochemical sensors using 3D printing and polylactic acid-based conductive carbon black commercial filament for theophylline and paracetamol detection. Electrochemical characterizations of the proposed sensor were performed to prove the functionality of the device. Morphological characterizations were carried out, in which chemical treatment could change the surface structure, causing the improvement of the analytical signal. Thus, the detection of theophylline at a linear range of 5.00-150 µmol L-1 with a limit of detection of 1.2 µmol L-1 was attained, and the detection of paracetamol at a linear range of 1.00-200 µmol L-1 with a limit of detection of 0.370 µmol L-1 was obtained, demonstrating the proposed sensor effectively detected pharmaceutical drugs.

Nanostructures of Prussian blue supported on activated biochar for the development of a glucose biosensor.

This work emphasizes the utilization of biochar, a renewable material, as an interesting platform for anchoring redox mediators and bioreceptors in the development of economic, environmentally friendly biosensors. In this context, Fe(III) ions were preconcentrated on highly functionalized activated biochar, allowing the stable synthesis of Prussian blue nanostructures with an average size of 58.3 nm. The determination of glucose was carried out by indirectly monitoring the hydrogen peroxide generated through the enzymatic reaction, followed by its subsequent redox reaction with reduced Prussian blue (also known as Prussian white) in a typical electrochemical-chemical mechanism. The EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-Hydroxysuccinimide) pair was employed for the stable covalent immobilization of the enzyme on biochar. The biosensor demonstrated good enzyme-substrate affinity, as evidenced by the Michaelis-Menten apparent kinetic constant (4.16 mmol L-1), and analytical performance with a wide linear dynamic response range (0.05-5.0 mmol L-1), low limits of detection (0.94 µmol L-1) and quantification (3.13 µmol L-1). Additionally, reliable repeatability, reproducibility, stability, and selectivity were obtained for the detection of glucose in both real and spiked human saliva and blood serum samples.

Simultaneous detection of dopamine and ascorbic acid by using a thread-based microfluidic device and multiple pulse amperometry.

This study presents a novel approach for the simultaneous detection of ascorbic acid (AA) and dopamine (DA) using an affordable and user-friendly microfluidic device. Microfluidic devices, when combined with electrochemical detectors like screen-printed electrodes (SPEs), offer numerous advantages such as portability, high sample throughput, and low reagent consumption. In this study, a 3D-printed microfluidic device called a µTED was developed, utilizing textile threads as microfluidic channels and an unmodified SPE as the amperometric detector. The method employed multiple pulse amperometry (MPA) with carefully selected potential values (+0.65 V and -0.10 V). The reduction current signals generated by dopamine o-quinone were used to calculate a correction factor for the oxidation signals of ascorbic acid, enabling simultaneous quantification. The developed microfluidic device ensured a stable flow rate of the carrier solution at 1.19 µL s-1, minimizing the consumption of samples and reagents (injection volume of 2.0 µL). Under the optimized experimental conditions, a linear range from 50 to 900 µmol L-1 was achieved for both DA and AA. The obtained sensitivities were 2.24 µA L mmol-1 for AA and 5.09 µA L mmol-1 for DA, with corresponding limits of detection (LOD) of 2.60 µmol L-1 and 1.54 µmol L-1, respectively. To confirm the effectiveness of the proposed method, it was successfully applied to analyze AA and DA in a commercial blood serum sample spiked at three different concentration levels, with a medium recovery rate of 70%. Furthermore, the MPA technique demonstrated its simplicity by enabling the simultaneous determination of AA and DA without the need for prior separation steps or the use of chemically modified electrodes.

Circular Economy Electrochemistry: Recycling Old Mixed Material Additively Manufactured Sensors into New Electroanalytical Sensing Platforms.

Recycling used mixed material additively manufactured electroanalytical sensors into new 3D-printing filaments (both conductive and non-conductive) for the production of new sensors is reported herein. Additively manufactured (3D-printed) sensing platforms were transformed into a non-conductive filament for fused filament fabrication through four different methodologies (granulation, ball-milling, solvent mixing, and thermal mixing) with thermal mixing producing the best quality filament, as evidenced by the improved dispersion of fillers throughout the composite. Utilizing this thermal mixing methodology, and without supplementation with the virgin polymer, the filament was able to be cycled twice before failure. This was then used to process old sensors into an electrically conductive filament through the addition of carbon black into the thermal mixing process. Both recycled filaments (conductive and non-conductive) were utilized to produce a new electroanalytical sensing platform, which was tested for the cell's original application of acetaminophen determination. The fully recycled cell matched the electrochemical and electroanalytical performance of the original sensing platform, achieving a sensitivity of 22.4 ± 0.2 µA µM-1, a limit of detection of 3.2 ± 0.8 µM, and a recovery value of 95 ± 5% when tested using a real pharmaceutical sample. This study represents a paradigm shift in how sustainability and recycling can be utilized within additively manufactured electrochemistry toward promoting circular economy electrochemistry.

Novel Additive Manufactured Multielectrode Electrochemical Cell with Honeycomb Inspired Design for the Detection of Methyl Parathion in Honey Samples.

The development and increase in the number of crops recently have led to the requirement for greater efficiency in world food production and greater consumption of pesticides. In this context, the widespread use of pesticides has affected the decrease in the population of pollinating insects and has caused food contamination. Therefore, simple, low-cost, and quick analytical methods can be interesting alternatives for checking the quality of foods such as honey. In this work, we propose a new additively manufactured (3D-printed) device inspired by a honeycomb cell, with 6 working electrodes for the direct electrochemical analysis of methyl parathion by reduction process monitoring in food and environmental samples. Under optimized parameters, the proposed sensor presented a linear range between 0.85 and 19.6 µmol L-1, with a limit of detection of 0.20 µmol L-1. The sensors were successfully applied in honey and tap water samples by using the standard addition method. The proposed honeycomb cell made of polylactic acid and commercial conductive filament is easy to construct, and there is no need for chemical treatments to be used. These devices based on 6 working electrodes array are versatile platforms for rapid, highly repeatable analysis in food and environment, capable of performing detection in low concentrations.

Flexible Label-Free Platinum and Bio-PET-Based Immunosensor for the Detection of SARS-CoV-2.

The demand for new devices that enable the detection of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) at a relatively low cost and that are fast and feasible to be used as point-of-care is required overtime on a large scale. In this sense, the use of sustainable materials, for example, the bio-based poly (ethylene terephthalate) (Bio-PET) can be an alternative to current standard diagnostics. In this work, we present a flexible disposable printed electrode based on a platinum thin film on Bio-PET as a substrate for the development of a sensor and immunosensor for the monitoring of COVID-19 biomarkers, by the detection of L-cysteine and the SARS-CoV-2 spike protein, respectively. The electrode was applied in conjunction with 3D printing technology to generate a portable and easy-to-analyze device with a low sample volume. For the L-cysteine determination, chronoamperometry was used, which achieved two linear dynamic ranges (LDR) of 3.98-39.0 µmol L-1 and 39.0-145 µmol L-1, and a limit of detection (LOD) of 0.70 µmol L-1. The detection of the SARS-CoV-2 spike protein was achieved by both square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) by a label-free immunosensor, using potassium ferro-ferricyanide solution as the electrochemical probe. An LDR of 0.70-7.0 and 1.0-30 pmol L-1, with an LOD of 0.70 and 1.0 pmol L-1 were obtained by SWV and EIS, respectively. As a proof of concept, the immunosensor was successfully applied for the detection of the SARS-CoV-2 spike protein in enriched synthetic saliva samples, which demonstrates the potential of using the proposed sensor as an alternative platform for the diagnosis of COVID-19 in the future.

Circular Economy Electrochemistry: Creating Additive Manufacturing Feedstocks for Caffeine Detection from Post-Industrial Coffee Pod Waste.

The recycling of post-industrial waste poly(lactic acid) (PI-PLA) from coffee machine pods into electroanalytical sensors for the detection of caffeine in real tea and coffee samples is reported herein. The PI-PLA is transformed into both nonconductive and conductive filaments to produce full electroanalytical cells, including additively manufactured electrodes (AMEs). The electroanalytical cell was designed utilizing separate prints for the cell body and electrodes to increase the recyclability of the system. The cell body made from nonconductive filament was able to be recycled three times before the feedstock-induced print failure. Three bespoke formulations of conductive filament were produced, with the PI-PLA (61.62 wt %), carbon black (CB, 29.60 wt %), and poly(ethylene succinate) (PES, 8.78 wt %) chosen as the most suitable for use due to its equivalent electrochemical performance, lower material cost, and improved thermal stability compared to the filaments with higher PES loading and ability to be printable. It was shown that this system could detect caffeine with a sensitivity of 0.055 ± 0.001 µA µM-1, a limit of detection of 0.23 µM, a limit of quantification of 0.76 µM, and a relative standard deviation of 3.14% after activation. Interestingly, the nonactivated 8.78% PES electrodes produced significantly better results in this regard than the activated commercial filament toward the detection of caffeine. The activated 8.78% PES electrode was shown to be able to detect the caffeine content in real and spiked Earl Grey tea and Arabica coffee samples with excellent recoveries (96.7-102%). This work reports a paradigm shift in the way AM, electrochemical research, and sustainability can synergize and feed into part of a circular economy, akin to a circular economy electrochemistry.

Novel and highly stable strategy for the development of microfluidic enzymatic assays based on the immobilization of horseradish peroxidase (HRP) into cotton threads.

The use of biological components in the development of new methods of analysis and point-of-care (POC) devices is an ever-expanding theme in analytical chemistry research, due to the immense potential for early diagnosis of diseases and monitoring of biomarkers. In the present work, the evaluation of an electrochemical microfluidic device based on the immobilization of horseradish peroxidase (HRP) enzyme into chemically treated cotton threads is described. This bioreactor was used as a channel for the build of the microfluidic device, which has allowed to use of a non-modified screen-printed electrode (SPE) as an amperometric detector. Cotton threads were treated using citric acid, and the immobilization of HRP has been performed by EDC/NHS crosslinking, connecting amine groups of the enzymes to carboxylic acids in the cellulosic structure. For the analytical evaluation, an amperometric assay for hydrogen peroxide detection was performed after the injection of H2O2 and hydroquinone (HQN) concomitantly. The enzymatic reaction consumes H2O2 leading to the formation of O-quinone, which is readily reducible at non-modified SPE. Several experimental parameters related to enzyme immobilization have been investigated and under the best set of conditions, a good analytical performance was obtained. In addition, the threads were freezer-stored and, after 12 weeks, 84% of hydrogen peroxide sensitivity was maintained, which is very reasonable for enzyme-based systems and still offers good analytical precision. Therefore, a simple and inexpensive microfluidic system was reported by crosslinking carboxylic groups to amine-containing macromolecules, suggesting a new platform for many other protein-based assays.

Electrochemical (Bio)Sensors Enabled by Fused Deposition Modeling-Based 3D Printing: A Guide to Selecting Designs, Printing Parameters, and Post-Treatment Protocols.

The 3D printing (or additive manufacturing, AM) technology is capable to provide a quick and easy production of objects with freedom of design, reducing waste generation. Among the AM techniques, fused deposition modeling (FDM) has been highlighted due to its affordability, scalability, and possibility of processing an extensive range of materials (thermoplastics, composites, biobased materials, etc.). The possibility of obtaining electrochemical cells, arrays, pieces, and more recently, electrodes, exactly according to the demand, in varied shapes and sizes, and employing the desired materials has made from 3D printing technology an indispensable tool in electroanalysis. In this regard, the obtention of an FDM 3D printer has great advantages for electroanalytical laboratories, and its use is relatively simple. Some care has to be taken to aid the user to take advantage of the great potential of this technology, avoiding problems such as solution leakages, very common in 3D printed cells, providing well-sealed objects, with high quality. In this sense, herein, we present a complete protocol regarding the use of FDM 3D printers for the fabrication of complete electrochemical systems, including (bio)sensors, and how to improve the quality of the obtained systems. A guide from the initial printing stages, regarding the design and structure obtention, to the final application, including the improvement of obtained 3D printed electrodes for different purposes, is provided here. Thus, this protocol can provide great perspectives and alternatives for 3D printing in electroanalysis and aid the user to understand and solve several problems with the use of this technology in this field.

Influence of filament aging and conductive additive in 3D printed sensors.

3D printing technology combined with electrochemical techniques have allowed the development of versatile and low-cost devices. However, some aspects need to be considered for the good quality and useful life of the sensors. In this work, we have demonstrated herein that the filament aging, the conductive material, and the activation processes (post-treatments) can influence the surface characteristics and the electrochemical performance of the 3D printed sensors. Commercial filaments and 3D printed sensors were morphologically, thermally, and electrochemically analyzed. The activated graphene-based (Black Magic®) sensor showed the best electrochemical response, compared to the carbon black-filament (Proto-Pasta®). In addition, we have proven that filament aging harms the performance of the sensors since the electrodes produced with three years old filament had a considerably lower intra-days reproducibility. Finally, the activated graphene-based sensor has shown the best performance for the electrochemical detection of bisphenol A, demonstrating the importance of evaluating and control the characteristics and quality of filaments to improve the mechanical, conductive, and electrochemical performance of 3D printed sensors.

Biosensing strategies for the electrochemical detection of viruses and viral diseases - A review.

Viruses are the causing agents for many relevant diseases, including influenza, Ebola, HIV/AIDS, and COVID-19. Its rapid replication and high transmissibility can lead to serious consequences not only to the individual but also to collective health, causing deep economic impacts. In this scenario, diagnosis tools are of significant importance, allowing the rapid, precise, and low-cost testing of a substantial number of individuals. Currently, PCR-based techniques are the gold standard for the diagnosis of viral diseases. Although these allow the diagnosis of different illnesses with high precision, they still present significant drawbacks. Their main disadvantages include long periods for obtaining results and the need for specialized professionals and equipment, requiring the tests to be performed in research centers. In this scenario, biosensors have been presented as promising alternatives for the rapid, precise, low-cost, and on-site diagnosis of viral diseases. This critical review article describes the advancements achieved in the last five years regarding electrochemical biosensors for the diagnosis of viral infections. First, genosensors and aptasensors for the detection of virus and the diagnosis of viral diseases are presented in detail regarding probe immobilization approaches, detection methods (label-free and sandwich), and amplification strategies. Following, immunosensors are highlighted, including many different construction strategies such as label-free, sandwich, competitive, and lateral-flow assays. Then, biosensors for the detection of viral-diseases-related biomarkers are presented and discussed, as well as point of care systems and their advantages when compared to traditional techniques. Last, the difficulties of commercializing electrochemical devices are critically discussed in conjunction with future trends such as lab-on-a-chip and flexible sensors.

Sensing of L-methionine in biological samples through fully 3D-printed electrodes.

The variation in biomarkers levels, such as L-methionine, can be an indicator of health problems or diseases, such as metabolism, neuropsychiatric disorders, or some virus infections. Thus, the development of accurate sensors, with low-cost and rapid response has been gaining increasing importance and attractiveness for the early diagnosis of diseases. In this regard, we have proposed a method for L-methionine electrochemical detection using a low-cost and simple arrangement of 3D-printed electrodes (working, reference, and auxiliary electrodes) based on polylactic acid/graphene filament (PLA-G), in which all electrodes were printed. The working electrode was chemically and electrochemically treated, showing a high electroactive area, with graphene edge plans exposure and better electron transfer when compared to the untreated electrode. An excellent analytical performance was obtained with a sensitivity of 0.176 µAL µmol-1, a linear dynamic range of 5.0 µmol L-1- 3000 µmol L-1 and limit of detection of 1.39 µmol L-1. The proposed device was successfully applied for L-methionine detection in spiked serum samples, showing satisfactory recovery values. This indicates the potentiality of the proposed arrangement of electrodes for the L-methionine detection in biological samples at different concentration levels.

Additive-manufactured (3D-printed) electrochemical sensors: A critical review.

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.

Waterproof paper as a new substrate to construct a disposable sensor for the electrochemical determination of paracetamol and melatonin.

Disposable electrochemical sensors using sustainable and cheap materials are an exciting alternative to produce new kinds of sensing platforms. Waterproof paper (WP) is a biodegradable and biocompatible material that allows dropped of the sample on its surface without absorption by fibers. Also, WP can be used for miniaturized sensors construction. In this work, a conductive ink was produced with nail polish and graphite powder, using the WP as the sensor substrate for paracetamol (PAR) and melatonin (MEL) voltammetric determination. PAR is a pharmaceutical commonly used in high doses for the relief of pain and fever, and MEL is a hormone related to several diseases besides a direct relation to sleep quality. Using differential pulse voltammetry for PAR determination, the WP sensor showed a linear response in the concentration ranging from 0.50 µmol L-1 to 100 µmol L-1 with a limit of detection (LOD) of 53.6 nmol L-1. Square wave voltammetry was applied for MEL determination, and the proposed electrode presented linear response ranging from 0.80 µmol L-1 to 100 µmol L-1 and LOD of 32.5 nmol L-1. The sensor showed excellent repeatability and reproducibility for consecutive measurements. Then, the disposable WP sensor was successfully applied in the determination of PAR and MEL in pharmaceutical and biological samples, with recovery values, above 91.1%. The described architecture allowed the manufacture of a disposable, simple, and low-cost electroanalytical device that can be used for electrochemical sensing.

Comparison of activation processes for 3D printed PLA-graphene electrodes: electrochemical properties and application for sensing of dopamine.

This paper reports the comparison of the electrochemical properties of 3D PLA-graphene electrodes (PLA-G) under different activation conditions and through different processes. In this work, the performance of the electrodes was evaluated after polishing, electrochemical and chemical treatments and a combination of them. The best results were obtained with hydroxide activation using 1.0 mol L-1 NaOH for 30 min of immersion, which promoted the saponification of PLA exposing the graphene nanoribbon structures. The improvement was more evident also after electrochemical activation, which led to a great increase in surface area, defects, electron transfer rate and amount of edge sites. The analytical performance of the proposed PLA-GNaOH-30-EC electrode was evaluated in the presence of dopamine (DA) by three electrochemical techniques, presenting a broad linear range, and limits of detection of 3.49, 2.17 and 1.67 µmol L-1 were obtained by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), respectively. The separation and quantification of DA in the presence of AA and UA was also reported. The sensor showed good repeatability and reproducibility and was successfully applied to DA determination in synthetic urine and human serum, showing good recovery, from 88.8 to 98.4%. Therefore, the activation methods were essential for the improvement in the 3D PLA-G electrode properties, allowing graphene surface alteration and electrochemical enhancement in the sensing of molecular targets.

Quick electrochemical immunoassay for hantavirus detection based on biochar platform.

This work describes the first method using biochar (BC) as carbonaceous platform for immunoassay application. BC is a highly functionalized material obtained through biomass pyrolysis under controlled conditions. Due to the highly functionalized surface, covalent binding between BC and biomolecules can be performed by EDC/NHS conjugation. The application of the modified electrode was done with Hantavirus, that are etiologic agents mainly transmitted by wild rodents. Among its pathologies Hantavirus Cardiopulmonary Syndrome (HCPS) arises at Americas, caused by Hantavirus Araucária and reaches 40% lethality. The diagnostic is based on the presence of specific hantavirus nucleoprotein (Np), under viremic condition or IgG2b antibodies (Ab), during first symptoms. The results presented a device sensitivity of 5.28 µA dec-1 and a LOD of 0.14 ng mL-1 to the Np detection, ranging from 5.0 ng mL-1 to 1.0 µg mL-1, the Ab detection works as qualitative type sensor above 200 ng mL-1. Both sensors were evaluated its selectivity and serum samples; selectivity against Gumboro disease, VP2 protein, and antibody IgG2a against Yellow fever disease (YF), respectively. So, the devices here proposed are promising tool suitable for both rodent and human hantavirus clinical surveys.

Green method for glucose determination using microfluidic device with a non-enzymatic sensor based on nickel oxyhydroxide supported at activated biochar.

This paper reports the use of nickel ions supported at activated biochar carbon paste electrode (NiAB-CPME) coupled in a microfluidic thread-based electroanalytical device (µTED) for non-enzymatic glucose determination. Biochar was initially prepared from castor oil cake at 400 °C and activated by HNO3 refluxing. Activation process promoted an increase of functional groups, surface area and porosity in comparison to precursor biochar. Activated biochar (AB) has shown an excellent performance to spontaneous preconcentration of Ni(II) ions. In alkaline conditions a stable voltammetric profile associated to Ni(OH)2/NiOOH redox pair was verified and a significant catalytic effect was observed in presence of glucose which was used for its monitoring. Microfluidic device was assembled at a plastic platform printed using 3D printer being easy to construction using low cost materials. Non-enzymatic amperometric glucose sensor coupled in µTED showed a good repeatability of 3.84% for successive injections of glucose (n = 10), a constant flow rate of 1.11 µL s-1 and an analytical frequency of 61 injections per hour. A linear dynamic range (LDR) from 5.0 to 100.0 µmol L-1, limit of detection (LOD) of 0.137 µmol L-1 and limit of quantification (LOQ) 0.457 µmol L-1 glucose were obtained. The proposed device was applied to glucose determination in real biological samples of human saliva and blood serum. Finally, the method was considered a green analytical procedure with Eco-Scale score of 81.

Activated biochar: Preparation, characterization and electroanalytical application in an alternative strategy of nickel determination.

This work reports for the first time the use of chemically activated biochar as electrode modifier for nickel determination. The biochar activation was performed by refluxing with HNO3, which promoted a higher nickel preconcentration compared to unmodified and modified biochar precursor electrodes. Morphological and structural characterization revealed the increase of surface acid groups, surface area and porosity of biochar after activation. Nickel determination was investigated adopting an alternative voltammetric methodology based on monitoring the Ni(II)/Ni(III) redox couple. In the proposed method, it was not necessary to use a complexing agent and the biochar itself was responsible for the analyte preconcentration. A linear response for Ni(II) concentration range from 1.0 to 30 µmol L-1 and a limit of detection of 0.25 µmol L-1 were obtained. The method was successfully applied for Ni(II) determination in spiked samples of bioethanol fuel and discharge water, with recoveries values between 103 and 109%.

Biochar prepared from castor oil cake at different temperatures: A voltammetric study applied for Pb(2+), Cd(2+) and Cu(2+) ions preconcentration.

Biochar is a carbonaceous material similar produced by pyrolysis of biomass under oxygen-limited conditions. Pyrolysis temperature is an important parameter that can alters biochar characteristics (e.g. surface area, pore size distribution and surface functional groups) and affects it efficacy for adsorption of several probes. In this work, biochar samples have been prepared from castor oil cake using different temperatures of pyrolysis (200-600°C). For the first time, a voltammetric procedure based on carbon paste modified electrode (CPME) was used to investigate the effect of temperature of pyrolysis on the adsorptive characteristics of biochar for Pb(II), Cd(II) and Cu(II) ions. Besides the electrochemical techniques, several characterizations have been performed to evaluate the physicochemical properties of biochar in function of the increase of the pyrolysis temperature. Results suggest that biochar pyrolized at 400°C (BC400) showed a better potential for ions adsorption. The CPME modified with BC400 showed better relative current signal with adsorption affinity: Pb(II)>Cd(II)>Cu(II). Kinetic studies revealed that the pseudo-second order model describes more accurately the adsorption process suggesting that the surface reactions control the adsorption rate. Values found for amount adsorbed were 15.94±0.09; 4.29±0.13 and 2.38±0.39µgg(-1) for Pb(II), Cd(II) and Cu(II) ions, respectively.