Simple and cost-effective pH and T sensors from top to bottom: New chemical probes based on sonogel-carbon transducers for plasma analyses

The present work introduces two novel approaches to fabricate simple and cost-effective pH and temperature probes. Sinusoidal voltage methodologies were employed to electrodeposit polyaniline (PANI) at different growth times (10-20 min) on the surface of an affordable Sonogel-Carbon electrode to conform a robust pH sensor. The presence of PANI and its phases were corroborated by electrochemical means. The sensibility, reversibility and selectivity of the produced sensor were very adequate to apply it in physiological samples. In this regard, the proposed sensor was evaluated in artificial blood serum as well as untreated plasma samples obtaining outstanding results in comparison with a gold reference technique (error <2 %). In addition, a new composite sonogel material, intrinsically modified with multiwalled carbon nanotubes, was attached on top of an electrode couple to one-step fabricate a new temperature probe, relating resistance of the probe with the surroundings temperature. In this case, an optical microscopy characterization was performed to study the sturdiness of the layer. Remarkably, suitable results in terms of sensitivity and selectivity were obtained. The probes were assessed in artificial and untreated plasma samples as well, with the corresponding validation step (error <1 %) by using a commercial temperature probe.

Development of a molecularly imprinted membrane for selective, high-sensitive, and on-site detection of antibiotics in waters and drugs: Application for sulfamethoxazole

Sulfonamides are among the widespread bacterial antibiotics. Despite this, their quick emergence constitutes a serious problem for ecosystems and human health. Therefore, there is an increased interest in developing relevant detection method for antibiotics in different matrices. In this work, a straightforward, green, and cost-effective protocol was proposed for the preparation of a selective molecularly imprinted membrane (MIM) of sulfamethoxazole (SMX), a commonly used antibiotic. Thus, cellulose acetate was used as the functional polymer, while polyethylene glycol served as a pore-former. The developed MIM was successfully characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The MIM was used as a sensing platform in conjunction with a smartphone for optical readout, enabling on-site, selective, and highly sensitive detection of SMX. In this way, a satisfactory imprinting factor of around 3.6 and a limit of detection of 2 ng mL-1 were reached after applying response surface methodologies, including Box-Behnken and central composite designs. Besides, MIM demonstrated its applicability for the accurate and selective detection of SMX in river waters, wastewater, and drugs. Additionally, the MIM was shown to be a valuable sorbent in a solid-phase extraction protocol, employing a spin column setup that offered rapid and reproducible results. Furthermore, the developed sensing platform exhibited notable regeneration properties over multiple cycles and long shelf-life in different storage conditions. The newly developed methodology is of crucial importance to overcome the limitations of classical imprinting polymers. Furthermore, the smartphone-based platform was used to surpass the typically expensive and complicated methods of detection.

Magnetic Molecularly Imprinted Chitosan Combined with a Paper-Based Analytical Device for the Smartphone Discrimination of Tryptophan Enantiomers

The separation of enantiomers plays a critical role in pharmaceutical development, ensuring therapeutic efficacy, safety, and patent protection. It enables the production of enantiopure drugs and enhances our understanding of the properties of chiral compounds. In this study, a straightforward and effective chiral detection strategy was developed for distinguishing between tryptophan (TRP) enantiomers. The approach involved the preparation of a magnetic molecularly imprinted chitosan (MMIC) for preparation of the sample, which was combined with a nitrocellulose membrane (a paper-based analytical device, PAD) integrated with D-TRP covalently grafted with polymethacrylic acid (PAD-PMA_D-TRP). Discriminating between the TRP enantiomers was achieved using AuNPs as a colorimetric probe. Indeed, the presence of D-TRP rapidly induced the aggregation of AuNPs due to its strong affinity to PAD-PMA_D-TRP, resulting in a noticeable change in the color of the AuNPs from red to purple. On the other hand, L-TRP did not induce any color changes. The chiral analysis could be easily performed with the naked eye and/or a smartphone. The developed method exhibited a detection limit of 3.3 µM, and it was successfully applied to detect TRP in serum samples, demonstrating good recovery rates. The proposed procedure is characterized by its simplicity, cost-effectiveness, rapidity, and ease of operation.

Feather-like Gold Nanostructures Anchored onto 3D Mesoporous Laser-Scribed Graphene: A Highly Sensitive Platform for Enzymeless Glucose Electrochemical Detection in Neutral Media

The authors present a novel sensing platform for a disposable electrochemical, non-enzymatic glucose sensor strip at physiological pH. The sensing material is based on dendritic gold nanostructures (AuNs) resembling feather branches, which are electrodeposited onto a laser-scribed 3D graphene electrode (LSGE). The LSGEs were fabricated via a one-step laser scribing process on a commercially available polyimide sheet. This study investigates several parameters that influence the morphology of the deposited Au nanostructures and the catalytic activity toward glucose electro-oxidation. The electrocatalytic activity of the AuNs-LSGE was evaluated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and amperometry and was compared to commercially available carbon electrodes prepared under the same electrodeposition conditions. The sensor demonstrated good stability and high selectivity of the amperometric response in the presence of interfering agents, such as ascorbic acid, when a Nafion membrane was applied over the electrode surface. The proposed sensing strategy offers a wide linear detection range, from 0.5 to 20 mM, which covers normal and elevated levels of glucose in the blood, with a detection limit of 0.21 mM. The AuNs-LSGE platform exhibits great potential for use as a disposable glucose sensor strip for point-of-care applications, including self-monitoring and food management. Its non-enzymatic features reduce dependence on enzymes, making it suitable for practical and cost-effective biosensing solutions.

Geographical Classification of Saffron (Crocus Sativus L.) Using Total and Synchronous Fluorescence Combined with Chemometric Approaches

There is an increasing interest in food science for high-quality natural products with a distinct geographical origin, such as saffron. In this work, the excitation-emission matrix (EEM) and synchronous fluorescence were used for the first time to geographically discriminate between Moroccan saffron from Taroudant, Ouarzazate, and Azilal. Moreover, to differentiate between Afghan, Iranian, and Moroccan saffron, a unique fingerprint was assigned to each sample by visualizing the EEM physiognomy. Moreover, principal component analysis (LDA) and linear discriminant analysis (LDA) were successfully applied to classify the synchronous spectra of samples. High fluorescence intensities were registered for Ouarzazate and Taroudant saffron. Yet, the Azilal saffron was distinguished by its low intensities. Furthermore, Moroccan, Afghan, and Iranian saffron were correctly assigned to their origins using PCA and LDA for different offsets (Δλ) (20-250 nm) such that the difference in the fluorescence composition of the three countries' saffron was registered in the following excitation/emission ranges: 250-325 nm/300-480 nm and 360-425 nm/500-550 nm. These regions are characterized by the high polyphenolic content of Moroccan saffron and the important composition of Afghan saffron, including vitamins and terpenoids. However, weak intensities of these compounds were found in Iranian saffron. Furthermore, a substantial explained variance (97-100% for PC₁ and PC₂) and an important classification rate (70-90%) were achieved. Thus, the non-destructive applied methodology of discrimination was rapid, straightforward, reliable, and accurate.

Incorporation of carbon black into a sonogel matrix: improving antifouling properties of a conducting polymer ceramic nanocomposite

A new electrochemical sensor device has been developed through the modification of a polyaniline-silicon oxide network with carbon black (CB). Enhanced electrical conductivity and antifouling properties have been achieved due to the integration of this cheap nanomaterial into the bulk of the sensor. The structure of the developed material was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy techniques. Cyclic voltammetry was used to characterize electrochemically the Sonogel-Carbon/Carbon Black-PANI (SNG-C/CB-PANI) sensor device. In addition, differential pulse voltammetry was employed to evaluate the analytical response of the sensor towards sundry chlorophenols, common environmental hazards in aqueous ecosystems. The modified sensor material showed excellent antifouling properties, which led to a better electroanalytical performance than the one displayed with the bare sensor. Notably, a sensitivity of 5.48 × 10³ μA mM^-1 cm^-2 and a limit of detection of 0.83 μM were obtained in the determination of 4-chloro-3-methylphenol (PCMC) at a working potential of 0.78 V (vs. 3 M Ag/AgCl/KCl), along with proficient values of reproducibility and repeatability (relative standard deviation < 3%). Finally, the analysis of PCMC was carried out in multiple validated water samples using the synthesized SNG-C/CB-PANI sensor device, obtaining excellent results of recovery values (97-104%). The synergetic effect of polyaniline and carbon black leads to novel antifouling and electrocatalytic effects that improve the applicability of this sensor in sample analysis versus complex conventional devices.

Ultrasound-promoted synthesis of a copper-iron-based catalyst for the microwave-assisted acyloxylation of 1,4-dioxane and cyclohexene

A copper-iron-based catalyst has been prepared by a low-temperature co-precipitation and sonication method. The use of high-energy ultrasound reduces the time required for the preparation process from one workweek to one day with respect to the catalysts obtained by conventional coprecipitation and thermal treatment methods. The resulting material has been characterized at compositional, textural, structural, and chemical levels by ICP-AES, BET, SEM-EDS, XRD, TEM, and FTIR among other techniques. The material shows catalytic activity in the acyloxylation reaction of 1,4-dioxane and cyclohexene under microwave irradiation. In parallel with the optimized catalyst synthesis, the use of microwaves allowed for a substantial improvement in the outcome of the reaction in terms of cleanliness, yield, and time.

What Is Left for Real-Life Lactate Monitoring? Current Advances in Electrochemical Lactate (Bio)Sensors for Agrifood and Biomedical Applications

Monitoring of lactate is spreading from the evident clinical environment, where its role as a biomarker is notorious, to the agrifood ambit as well. In the former, lactate concentration can serve as a useful indicator of several diseases (e.g., tumour development and lactic acidosis) and a relevant value in sports performance for athletes, among others. In the latter, the spotlight is placed on the food control, bringing to the table meaningful information such as decaying product detection and stress monitoring of species. No matter what purpose is involved, electrochemical (bio)sensors stand as a solid and suitable choice. However, for the time being, this statement seems to be true only for discrete measurements. The reality exposes that real and continuous lactate monitoring is still a troublesome goal. In this review, a critical overview of electrochemical lactate (bio)sensors for clinical and agrifood situations is performed. Additionally, the transduction possibilities and different sensor designs approaches are also discussed. The main aim is to reflect the current state of the art and to indicate relevant advances (and bottlenecks) to keep in mind for further development and the final achievement of this highly worthy objective.

A Sensitive Electrochemical Sensor Based on Sonogel-Carbon Material Enriched with Gold Nanoparticles for Melatonin Determination

In this work, the development of an electrochemical sensor for melatonin determination is presented. The sensor was based on Sonogel-Carbon electrode material (SNGCE) and Au nanoparticles (AuNPs). The low-cost and environmentally friendly SNGCE material was prepared by the ultrasound-assisted sonogel method. AuNPs were prepared by a chemical route and narrow size distribution was obtained. The electrochemical characterization of the SNGCE/AuNP sensor was carried out by cyclic voltammetry in the presence of a redox probe. The analytical performance of the SNGCE/AuNP sensor in terms of linear response range, repeatability, selectivity, and limit of detection was investigated. The optimized SNGCE/AuNP sensor displayed a low detection limit of 8.4 nM melatonin in synthetic samples assessed by means of the amperometry technique. The potential use of the proposed sensor in real sample analysis and the anti-matrix capability were assessed by a recovery study of melatonin detection in human peripheral blood serum with good accuracy.

Polyaniline Nanofibers-Embedded Gold Nanoparticles Obtained by Template-Free Procedure with Immobilization Prospects

In this work, template-free nanostructured conducting polymers (nCPs)-embedded gold nanoparticles (AuNPs) from aniline, thiophene and 3,4-ethylenedioxythiophene have been prepared via a one-pot sonochemical method. The synthesis of the nanocomposite (nCPs-AuNPs) was achieved in a short period of time (5-10 min), by applying high-energy ultrasound to an aqueous mixture of a CP precursor monomer and KAuCl4, in the presence of LiClO4 as dopant. The synthesis process is simpler, greener and faster in comparison to other procedures reported in the literature. Remarkably, bulk quantities of doped polyaniline PANI-AuNPs nanofibers were obtained. Subsequently, they were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR), as well as by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). PANI-AuNPs nanofibers were also employed as immobilization matrix for a benchmark enzyme, glucose oxidase (GOX). Finally, glucose was determined in real samples of white and red wines by using the so-obtained GOX-PANI-AuNPs/Sonogel-Carbon biosensor, providing outstanding recoveries (99.54%). This work may offer important insights into the synthesis of nanostructured conducting polymers and also stimulates the exploration of the applications of these nanocomposites, especially in research fields such as (bio)sensors, catalysis and composite materials.

E-Tongues/Noses Based on Conducting Polymers and Composite Materials: Expanding the Possibilities in Complex Analytical Sensing

Conducting polymers (CPs) are extensively studied due to their high versatility and electrical properties, as well as their high environmental stability. Based on the above, their applications as electronic devices are promoted and constitute an interesting matter of research. This review summarizes their application in common electronic devices and their implementation in electronic tongues and noses systems (E-tongues and E-noses, respectively). The monitoring of diverse factors with these devices by multivariate calibration methods for different applications is also included. Lastly, a critical discussion about the enclosed analytical potential of several conducting polymer-based devices in electronic systems reported in literature will be offered.

Simultaneous Detection of Glucose and Fructose in Synthetic Musts by Multivariate Analysis of Silica-Based Amperometric Sensor Signals

Silica-based electrodes which permanently include a graphite/Au nanoparticles composite were tested for non-enzymatic detection of glucose and fructose. The composite material showed an effective electrocatalytic activity, to achieve the oxidation of the two analytes at quite low potential values and with good linearity. Reduced surface passivation was observed even in presence of organic species normally constituting real samples. Electrochemical responses were systematically recorded in cyclic voltammetry and differential pulse voltammetry by analysing 99 solutions containing glucose and fructose at different concentration values. The analysed samples consisted both in glucose and fructose aqueous solutions at pH 12 and in solutions of synthetic musts of red grapes, to test the feasibility of the approach in a real frame. Multivariate exploratory analyses of the electrochemical signals were performed using the Principal Component Analysis (PCA). This gave evidence of the effectiveness of the chemometric approach to study the electrochemical sensor responses. Thanks to PCA, it was possible to highlight the different contributions of glucose and fructose to the voltammetric signal, allowing their selective determination.

Fast microwave-assisted synthesis of magnetic molecularly imprinted polymer for sulfamethoxazole

A fast and simple strategy based on the microwave technique for the preparation of magnetic molecularly imprinted polymers (MMIPs) is proposed for the selective determination of sulfamethoxazole (SMX). The MMIPs were synthesized at 70 °C in 20 min, being much faster than the conventional techniques. A computational approach based on density functional theory was used to design the MMIP and compare the two most used monomers in MIPs, including methacrylic acid (MAA) and acrylamide (AM). Then, two different MMIPs were prepared using AM and MAA as monomers. The resultant materials were characterized with X-ray diffraction, thermogravimetric analysis, scanning/transmission electron microscopy, and Fourier-transform infrared spectroscopy. Besides, the adsorption characterizations suggested that the adsorption of SMX followed the pseudo-second-order model in the kinetic study and the Sips model in the isotherm study. The experimental results corroborated the computational approach. Furthermore, Both MMIPs demonstrated good selectivity. The MMIP-AM and MMIP-MAA were applied as adsorbents in magnetic dispersive solid-phase extraction combined with UV-visible spectroscopy to quantify SMX. The obtained limits of detection and quantification were lower than 0.59 and 1.77 μM, respectively for both MMIPs. The sensitivity of both MMIPs was in the range of 0.021-0.023 (SI). Our findings revealed that there is no significant difference in the analytical parameters between MMIP-AM and MMIP-MAA. However, the application of both MMIPs in a real sample (tap water) showed that the recovery values of SMX obtained with MMIP-AM (68-70%) were lower than that with MMIP-MAA (80-90%) suggesting that MMIP-MAA is more appropriate for SMX determination.

One-minute and green synthesis of magnetic iron oxide nanoparticles assisted by design of experiments and high energy ultrasound: Application to biosensing and immunoprecipitation

The present study is focused on the ultrafast and green synthesis, via the co-precipitation method, of magnetic nanoparticles (MNPs) based on iron oxides using design of experiments (DOE) and high energy sonochemical approach, considering two main factors: amplitude (energy) of the ultrasound probe and sonication time. The combination of these techniques allowed the development of a novel one-minute green synthesis, which drastically reduced the amount of consumed energy, solvents, reagents, time and produced residues. This green sonochemical synthesis permitted to obtain mean particle sizes of 11 ± 2 nm under the optimized conditions of amplitude = 40% (2826 J) and time = 1 min. Their composition, structure, size, morphology and magnetic properties were assessed through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning and transmission electron microscopy (SEM & TEM), and vibrating sample magnetometry (VSM). The characterization results indicate the proper formation of MNPs, and the correct functionalization of MNPs with different coating agents. The functionalized MNPs were used as: i) biosensor, which could detect mercury in water in the range of 0.030-0.060 ppm, and ii) support onto which polyclonal antibodies were anchored and successfully bound to an osteosarcoma cell line expressing the target protein (TRIB2-GFP), as part of an immunoprecipitation assay.

Study of solvent effect on the synthesis of magnetic molecularly imprinted polymers based on ultrasound probe: Application for sulfonamide detection

In this work, a comparative study of the effect of various solvents on the synthesis of magnetic molecularly imprinted polymers (MMIPs) based on the use of high-power ultrasound probe is reported for the first time. Dimethylsulfoxide (DMSO), dimethylformamide (DMF), ethanol, acetonitrile and acetone were studied as solvents for the synthesis of MMIPs. Several crucial experimental conditions such as the time of synthesis and the applied amplitude were investigated. DMSO, DMF and ethanol were successfully used for ultrasound-assisted synthesis of MMIPs. However, for the polymerization performed using acetonitrile and acetone, no significant conversion to product was observed. Under optimal conditions for each solvent tested, the synthesized MMIPs were characterized using several techniques such as Scanning/Transmission Electron Microscopy (SEM and STEM modes), X-Ray Diffraction, Fourier Transform Infra-Red Spectroscopy, Thermal Gravimetric Analysis and Vibrating Sample Magnetometer system. The study of adsorption time of MMIPs showed that fast adsorption occurred due to the presence of specific imprinted sites on the surface. Moreover, isotherm study showed that the experimental equilibrium data fitted well with Freundlich model. The results of selectivity study indicated that MMIPs could selectively recognize the target molecule. Due to its high adsorption properties and easiness of preparation, MMIP-DMSO was used successfully as adsorbent material in solid-phase extraction coupled to a colorimetric method for sulfamethoxazole (SMX). After optimizing analytical conditions, a calibration plot was performed in the concentration range from 0.2 to 5 µg·mL^-1 with limits of detection and quantitation of 0.06 and 0.2 µg·mL^-1, respectively. The developed procedure was applied successfully for SMX determination in spiked tap and mineral waters showing satisfactory recoveries. Besides, reusability study demonstrated that MMIP could be reused at least 8 times keeping good binding capacity.

Fast route for the synthesis of decorated nanostructured magnetic molecularly imprinted polymers using an ultrasound probe

In this paper, we report for the first time a novel, simple and fast method for the synthesis of magnetic molecularly imprinted polymers (Mag-MIPs) based on high-energy ultrasound probe. Sulfamethoxazole (SMX) was used as template molecule, methacrylic acid as functional monomer, ethylene glycole dimethacrylate as crosslinking agent and magnetic nanoparticles (NPs) as the supporting core. The effects of time (5, 7.5 and 10 min) and the applied amplitude (20, 30, 40, 50 and 60%) using the ultrasound probe for the synthesis of Mag-MIPs were studied and optimized. By applying the proposed synthesis method, the US-magMIPs synthesis time was satisfactorily reduced from several hours to a few minutes (7.5 min) in a simple way. For comparison purposes, the Mag-MIP and the non imprinted polymer (MagNIP) were also synthesized employing an ultrasound bath assisted approach (2 h, 65 °C). Magnetic NPs and US-magMIPs synthesized by both ways were investigated by means of several characterization techniques such as Fourier Transform Infrared (FT-IR) spectroscopy, Scanning/Transmission electron microscopy (SEM and STEM modes), X-Ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and Dynamic Light Scattering (DLS). The results obtained confirms clearly the formation of magnetic NPs and their successful decoration by the imprinted polymer in both synthesis ways. The sulfonamide binding efficiency of US-magMIPs synthesized by the ultrasound probe and ultrasound bath were investigated according to the adsorption isotherm. The obtained results showed that the US-magMIP synthesized with the probe has more binding capacity compared to the one synthesized with US bath. The adsorption time was studied and both synthesized US-magMIPs reached the maximum adsorption capacity toward SMX after 1 h and the US-magMIP probe tends to have more easiness to bind SMX in less time. The selectivity studies of the synthesized US-magMIPs based on probe and bath showed a high affinity for SMX compared to its structural analogues such as sulfadiazine, sulfamerazine and sulfacetamide.

Prediction of parameters related to grape ripening by multivariate calibration of voltammetric signals acquired by an electronic tongue

An electronic tongue (ET) consisting of two voltammetric sensors, namely a poly-ethylendioxythiophene modified Pt electrode and a sonogel carbon electrode, has been developed aiming at monitoring grape ripening. To test the effectiveness of device and measurement procedures developed, samples of three varieties of grapes have been collected from veraison to harvest of the mature grape bunches. The derived musts have been then submitted to electrochemical investigation using Differential Pulse Voltammetry technique. At the same time, quantitative determination of specific analytical parameters for the evaluation of technological and phenolic maturity of each sample has been performed by means of conventional analytical techniques. After a preliminary inspection by principal component analysis, calibration models were calculated both by partial least squares (PLS) on the whole signals and by the interval partial least squares (iPLS) variable selection algorithm, in order to estimate physico-chemical parameters. Calibration models have been obtained both considering separately the signals of each sensor of the ET, and by proper fusion of the voltammetric data selected from the two sensors by iPLS. The latter procedure allowed us to check the possible complementarity of the information brought by the different electrodes. Good predictive models have been obtained for estimation of pH, total acidity, sugar content, and anthocyanins content. The application of the ET for fast evaluation of grape ripening and of most suitable harvesting time is proposed.

Amperometric inhibition biosensors based on horseradish peroxidase and gold sononanoparticles immobilized onto different electrodes for cyanide measurements

New biosensors based on inhibition for the detection of cyanide and the comparison of the analytical performances of nine enzyme biosensor designs by using three different electrodes: Sonogel-Carbon, glassy carbon and gold electrodes were discussed. Three different horseradish peroxidase immobilization procedures with and without gold sononanoparticles were studied. The amperometric measurements were performed at an applied potential of -0.15V vs. Ag/AgCl in 50mM sodium acetate buffer solution pH=5.0. The apparent kinetic parameters (Kmapp, Vmaxapp) of immobilized HRP were calculated in the absence of inhibitor (cyanide) by using caffeic acid, hydroquinone, and catechol as substrates. The presence of gold sononanoparticles enhanced the electron transfer reaction and improved the analytical performance of the biosensors. The HRP kinetic interactions reveal non-competitive binding of cyanide with an apparent inhibition constant (Ki) of 2.7μM and I50 of 1.3μM. The determination of cyanide can be achieved in a dynamic range of 0.1-58.6μM with a detection limit of 0.03μM which is lower than those reported by previous studies. Hence this biosensing methodology can be used as a new promising approach for detecting cyanide.

Electrochemical analysis of endosulfan using a C18-modified carbon-paste electrode

Successful applications of different analytical procedures to determine quantitatively endosulfan and its metabolites in aqueous media can be found in recent literature. Fundamentally, they have made use of solid-phase extraction (SPE) and gas (GC) or liquid chromatography (LC), sometimes coupled to mass spectrometry (MS). In this paper, a new and alternative methodology to determine quantitatively endosulfan in aqueous media is reported. A C18-modified carbon-paste electrode has been used to determine voltammetrically endosulfan, despite its unfavourable electrochemical properties and behaviour. The methodology proposed is based on the decrease experienced by the peak intensity corresponding to voltammetric signals of Cu(II) when successive and constant additions of endosulfan are carried out. This decrease is directly proportional to the concentration of endosulfan what allows to perform an indirect quantification of the pesticide. The detection limit obtained is 40 ng l(-1), this value being under the limits specified by European norms and EPA reports.