Chronopotentiometric Analysis Research Articles

Versatile bimetallic metal-organic framework with nanocutting channels tailored for efficient electrocatalytic water oxidation and glucose detection

Metal–organic frameworks (MOF) with outstanding properties have shown great potential for electrochemical water splitting, particularly for the oxygen evolution reaction (OER) and nonenzymatic glucose detection. In this study, a facile method was used to synthesize CoNiMOF (with 5-aminoisophthalic acid as the organic linker) as electrocatalyst for the OER and glucose oxidation reaction (GOR). In-depth structural and microstructural analyses confirmed the formation of the MOF via metal–ligand (electron donor–acceptor) coordination. Among the different CoNiMOFs, CoNi(1:3)MOF shown to have nanocutting channels along the edges of the microstructural sheets, exhibited good catalytic activity toward the OER and GOR. CoNi(1:3)MOF delivers the best electrocatalytic performance in 1 M KOH with an overpotential of 348 mV at 20 mA cm−2 for the OER, benefitting from the specific morphology and electronic control. Moreover, the electrocatalyst was remarkably stable after 5000 cyclic voltammetry cycles and chronopotentiometric (20 h) analysis. As glucose sensor, CoNi(1:3)MOF exhibits a remarkably low glucose detection limit (1.03 μΜ) and wide detection range (2–500 μΜ and 1–15 mM, respectively). In addition, CoNi(1:3)MOF performed efficiently in an interference study, which revealed the selectivity of the developed sensor. The active formation of bimetallic MOF structures and the synergistic effect between the two metals in the electrocatalyst is attributed to the efficient modulation of the electronic structure, which effectively influenced the OER and GOR performance.

Enriched oxygen vacancy promoted heteroatoms (B, P, N, and S) doped CeO2: Challenging electrocatalysts for oxygen evolution reaction (OER) in alkaline medium

Increasing worldwide energy consumption has prompted considerable study into energy generation and energy storage systems in recent years. Chemical fuels may be produced efficiently via electrocatalytic water splitting, which uses electric and solar power. The development of efficient anodic electrocatalysts for efficient oxygen evolution reaction (OER) is a greater concern of present energy research. Cerium oxide (CeO2) are promising electrocatalysts that exhibit outstanding OER but their reduced stability obstructs the practical application. A novel strategy was established to construct an effective catalyst of heteroatom (N, B, P and S) doped CeO2 matrix were prepared. Moreover, the doping of heteroatoms into the CeO2 matrix processes the improved electronic conductivity, reactive sites, increases the electrochemical catalytic activity, which enhances the water oxidation reaction. Consequently, well-suited alkaline electrolysers were brought together for water oxidation to ideal OER electrocatalytic activity. The OER activity of the electrocatalysts follows the order of S–CeO2 (190 mV@10 mA cm−2), N– CeO2 (220 mV @10 mA cm−2), P– CeO2 (230 mV @10 mA cm−2), B–CeO2 (250 mV @10 mA cm−2) and CeO2 (260 mV @10 mA cm−2) in 1 M of KOH. From the kinetics analysis, Tafel slope value achieved for catalysts CeO2, B–CeO2, P–CeO2, N–CeO2 and S–CeO2 are 142 mV dec−1,121 mV dec−1, 102 mV dec−1, 98 mV dec−1 and 83 mV dec−1 respectively. These results validate that the S–CeO2 electrode is prominent for OER performance with the requirement of cell voltage of 1.42 V at 10 mA cm−2 current density. In addition, sulphur doped CeO2 relatively have excellent stability through chrono-potentiometric analysis lasting for 20 h. Although the heteroatoms doped CeO2 is acts as anode material, the preparation method is widespread, which will reduce the synthesis cost and streamline the preparation of electrode for OER. This research effort delivers a complete advantage for the development of robust, environmentally friendly and highly dynamic electrocatalysts for OER activity.

CuFeN/CNT composite derived from kinetically modulated urchin-shaped MOF for highly efficient OER catalysis

Most reported non-precious-metal catalysts for oxygen evolution reaction (OER) are composed of iron, cobalt, or nickel. Copper, on the other hand, is relatively neglected despite its versatility. In this paper, we describe a series of steps to enhance the OER efficiency of copper-based catalyst, including metal organic framework (MOF)-guided structure control, secondary metal doping, and nitridation. In particular, the effect of growth solvent on coordination kinetics and morphology of the precursor MOFs was studied in detail. The optimal MOF structure was further engineered with Fe doping followed by rapid microwave-assisted nitridation, resulting in CuFeN/CNT composite. Experimental results showed that all three engineering steps have significant impact on the enhanced OER efficiency. CuFeN/CNT composite with optimal Fe doping derived from urchin-shaped CuFeMOF exhibited a greatly enhanced OER performance comparable to that of precious metal catalyst, affording a current density as high as 236.3 mA at an overpotential of 420 mV (RuO2, 215.3 mA). Furthermore, excellent stability in alkaline media was observed during 1000 cycles and chronopotentiometric analysis for over 20 hours. We highlight that the entire synthesis protocol is environmentally benign and sustainable by employing microwave to enable rapid formation and conversion of the precursors with minimal energy consumption.

A Unique Platinum/Titania/Polymer Based Hybrid Organic-Inorganic Heterostructure for Enhanced Photocatalytic Activity

This work delineates synthesis, characterization, and photocatalytic activity of a ‘hybrid organic-inorganic’ catalyst system, that consists of titanium dioxide (TiO<sub>2</sub>), platinum (Pt) and a conductive polymer (polypyrrole). The nanocomposite photocatalyst was developed to enhance exciton separation in the large band-gap oxide semiconductor (TiO<sub>2</sub>) by depositing a noble metal co-catalyst (Pt) at the surface. The hybrid nanocomposite was constructed through sequential sequestration of the building blocks i.e., the monomer (pyrrole) and the metal (Pt) salt, using a photo-deposition technique. At the same time, improvement for light absorbance as compared to pristine TiO<sub>2</sub> was realized through the deposition of a conducting polymer (polypyrrole) at the surface of the semiconductor. The polypyrrole provides a pathway for hole migration, thereby increasing the overall lifetime of the separated charges. The benefit of this architecture is demonstrated through an enhanced degradation (~40% increase) of an industrial dye, methyl orange as a representative example, under visible-light illumination compared to unmodified TiO<sub>2</sub>. Furthermore, photo(electro)chemical analysis of the composite offered valuable insights into the charge transport mechanism. It led to the conclusion that photo illumination results in the participating components to (a) enable visible light absorbance and, (b) facilitate charge separation and utilization at the hetero-interfaces leading to redox activity. Insights into the mechanism of charge separation and transport from chronopotentiometric analysis suggest that the assembly is successful and works as desired.

Hydrogen evolution reaction at extreme pH conditions of copper sulfide micro-hexagons

Electrochemical hydrogen evolution reaction (HER) using non-precious compounds has gained substantial interest in the development of water electrolyzers. Herein, we report the synthesis of Copper sulfide (Cu2S) micro-hexagons via a hydrothermal method, followed by some of the important physiochemical characterizations and electrochemical measurements towards the HER. Cu2S micro-hexagons could catalyze the HER in both basic (1 M KOH) and acidic solutions (0.5 M H2SO4), corresponding to the extreme pH values of 14 and 0, respectively. As manifested from the polarization curve, Cu2S micro-hexagons required an overpotential of −330 mV and −312 mV to deliver a benchmark catalytic current density of 10 mA cm−2 in basic and acidic solutions, respectively. Furthermore, lower overpotentials are complemented with the prominent long-term stability of 24 h, as evident from chronopotentiometric analysis. The superior electrochemical performance of these Cu2S micro-hexagons demonstrates their promising suitability for water-splitting applications.

Enzymatically functionalized polyaniline thin films produced with one-step electrochemical immobilization and its application in glucose and urea potentiometric biosensors.

Glucose and urea enzymatic biosensors were fabricated. One-step electrochemical immobilization process was used to produce thin polyaniline films with entrapped enzymes. Chronopotentiometric analysis, scanning electron microscopy, electrochemical impedance spectroscopy and optical reflectance spectroscopy were used to determine the structure-property relationship of the functionalized polymeric thin films. The device has a recognition stage connected to a potentiometric field-effect-transistor stage and is based on the measurement of microenvironment pH variation or locally produced ions. Optimization of biosensor fabrication and effective measurement conditions were performed. The optimized films presented sensitivity, linearity and detection range to glucose of 14.6 ± 0.4mV/decade, 99.8% and from 10-4M to 10-1mol/L. Two different biosensors were produced based on the enzymatic reaction of urea with selectivity to ammonium or hydroxyl ions. For ammonium ion selective film, the sensor's parameters were 14.7 ± 0.9mV/decade, 98.2% and from 10-5 to 10-1mol/L. For the hydroxyl ion selective film, the same parameters were 7.4 ± 0.5mV/decade, 98.1% and from 10-5 to 10-1mol/L. The change in the oxidation state of the polymeric matrix explains: i) the large loss of functionality of glucose biosensor in time, ii) the conservation of functionality to the hydroxyl ions for urea biosensor and iii) the selectivity variation of the ammonium ion selective urea biosensor. The results indicate that the polymeric matrix has indeed changeable selectivity, what can be applied in different situations for biosensors production.

Microscopic model for pH sensing mechanism in zinc-based nanowalls

Zinc based nanostructures are very promising material for pH sensing since they allow the realization of low-cost, sustainable, and high sensitivity electrodes. The pH sensitivity reported in literature for different ZnO nanostructures spreads from sub- to super-Nernstian, with the microscopic mechanism behind the H+ detection often unrevealed. In this work we synthesize by hydrothermal process and thermal annealing two zinc based nanowalls (NWLs) consisting of layered hydroxide zinc nitrate Zn5(OH)8(NO3)2·2H2O (as grown) and zinc oxide ZnO (annealed) phases, respectively. Scanning electron microscopy, micro Raman spectroscopy, X-ray photoemission spectroscopy were used to characterize the morphology and structure of NWLs. Electrochemical chronopotentiometric analysis in standard buffer solutions (pH 4 to 9) was used to study the response towards pH. Despite the two zinc based NWLs have the same morphology (interconnected sheets 10-20 nm thin, 1.4–1.7 μm wide), truly different behavior as pH sensitive electrodes are evidenced. As grown NWLs show a super-Nernstian response (+83.7 mV/decade), whereas annealed NWLs show a sub-Nernstian response (+27.1 mV/decade). The data are satisfactorily modeled by considering the crystallographic structures and assuming that layered hydroxide zinc nitrate NWLs is sensitive to only H+ (with two simultaneous and independent mechanisms), while zinc oxide NWLs is simultaneously and independently sensitive to both H+ and OH−. These data and the proposed modeling are useful to further develop the pH sensitivity of electrodes based on ZnO nanostructures.

Transport hindrances with electrodialytic recovery of citric acid from solution of strong electrolytes

Abstract Electrodialytic (ED) recovery of citric acid (CA) in the presence/absence of strong electrolytes (NaCl, CaCl 2 and FeCl 3 ) was separately analyzed under different process conditions. Recovery effectiveness was quantitatively estimated from current efficiency values. Efficiency attained optimum value with both flow rate and potential applied, while a monotonic rise was noted with temperature which got lowered beyond 0.1 mol·L − 1 feed concentration. 40% drop in efficiency was recorded in the presence of strong electrolytes (NaCl, CaCl 2 and FeCl 3 ) in feed relative to their presence in concentrate. Severe transport hindrance and efficiency loss were attributed to adsorption and allied physicochemical changes occurred with anion/cation exchange membranes (AEM/CEM) and these were confirmed through contact angle/Chronopotentiometry/AFM/EDX. Sluggish potential rise (Galvanostatic mode) in Chronopotentiometric analysis indicated diffusion limiting transport of organic acids influenced AEM resistance. XRD and EDX analysis indicated the presence of salt hydrates/ions (Ca 2 + /Fe 3 + ) over CEM justifying the resistance buildup due to adsorption of multivalent metal ion(s) and salts.

Direct chronopotentiometric analysis of riboflavin using a glassy carbon vessel as the working electrode

A new method for the determination of riboflavin (vitamin B2) was developed based on chronopotentiometry with a glassy carbon process vessel macroelectrode. The method optimisation included investigation of the most important experimental parameters: type and concentration of the supporting electrolyte, initial potential, reduction current, and the working electrode surface area. The reduction signal of riboflavin appeared at about -0.12 V vs. Ag/AgCl (3.5 mol/dm3 KCl) electrode in 0.025 mol/dm3 HCl as the supporting electrolyte. A linear response was obtained in the the range of 0.05-4 mg/dm3. The limit of detection and limit of quantitation were 0.018 mg/dm3 and 0.054 mg/dm3, respectively. Due to the use of specific working electrode, a significant enhancement of the method relative sensitivity of about 10 times was achieved. The accuracy of the defined method was confirmed by HPLC analyses. The developed method was successfully applied for the quantitation of riboflavin in various pharmaceutical multivitamin preparations.

A comparison of different methods to remove dissolved oxygen: Application to the electrochemical determination of imidacloprid

This study compares different methods for the removal of oxygen from the solution prior to the chronopotentiometric determination of the insecticide imidacloprid on glassy carbon electrode. The research included the application of the chemical method involving addition of sulfite ion, and the physical method of purging the sample with nitrogen stream, as well as their combination. By comparing analytical signals of imidacloprid, chemical method showed almost the same efficiency as conventional physical method, while the best reproducibility was achieved by applying chemical method with addition of the saturated sodium sulfite solution. The method is very simple and can be applied for deoxygenation of the solution prior to the chronopotentiometric analysis. The application of the chemical deoxygenation significantly shortened duration of the chronopotentiometric analysis of imidacloprid from approximately 15 min to 1 min.

Pulse current enhanced electrodialytic soil remediation—Comparison of different pulse frequencies

Energy consumption is an important factor influencing the cost of electrodialytic soil remediation (EDR). It has been indicated that the pulse current (in low frequency range) could decrease the energy consumption during EDR. This work is focused on the comparison of energy saving effect at different pulse frequencies. Based on the restoration of equilibrium, the relaxation process of the soil–water system was investigated by chronopotentiometric analysis to find the optimal relaxation time for energy saving. Results showed that the pulse current decreased the energy consumption with different extent depending on the pulse frequency. The experiment with the frequency of 16 cycles per day showed the best restoration of equilibrium and lowest energy consumption. The energy consumption per removed heavy metals was lower in pulse current experiments than constant current and increased with the pulse frequency. It was found that the transportation of cations through the cation exchange membrane was the rate controlling step both in constant and pulse current experiments, thus responsible for the major energy consumption. Substitution of the cation exchange membrane with filter paper resulted in a dramatic decrease in energy consumption, but this change impeded the acidification process and thus the removal of heavy metals decreased significantly.

A simple and rapid method for histamine determination in fermented sausages by mediated chronopotentiometry

In order to provide the basis for the development of an inexpensive, sensitive, and reliable method for histamine determination in foods, the electrochemical behavior of histamine at planar gold disc electrode was investigated by chronopotentiometry. In solutions with sufficient chloride content dual oxidative mechanism of histamine was observed and included catalytic effect of electrogenerated chlorine. Well defined signal observed at +1.15 V in 0.0025 mol/l hydrochloric acid demonstrated sensitive changes with histamine content and was attributed to histamine. Electrogenerated chlorine facilitated charge transfer between histamine and the gold electrode resulting in enhancement of sensitivity. The effects of the most important experimental parameters of the chlorine-mediated chronopotentiometric analysis, such as the type and concentration of supporting electrolyte, initial potential and oxidation current were optimised. Under optimal experimental conditions, linear response of histamine was observed in the range 2–100 mg/l with achieved limit of detection for 0.27 mg/l of histamine. Developed method was applied for histamine determination in fermented sausages.

Determination of histamine in cheese by chronopotentiometry on a thin film mercury electrode

Simple electroanalytical method for histamine determination based on its irreverse oxidation by a constant current on a thin film mercury electrode was developed in this work. Experimental parameters of chronopotentiometric analysis, such as concentration of the supporting electrolyte, initial potential and dissolution current were optimised. The optimal experimental parameters included an initial potential of −0.4 V and oxidation currents in the range from 3 to 30 μA in 0.02 mol/l sulphuric acid. After the optimisation of experimental parameters, the linear response was obtained in the range 2–90 mg/l of histamine with achieved detection limit of 1.31 mg/l of histamine. The method was applied for the determination of histamine in various types of cheese. Prior sample analysis the procedure for sample preparation was developed and included ultrasonically-assisted extraction and chromatographic separation on a thin layer. To our knowledge, histamine has never previously been determined on mercury electrodes nor by applying chronopotentiometric analysis, thus developed electroanalytical method represents an important contribution to electroanalytical practise. By applying the developed method it is possible to perform simple and fast cheese analysis. Furthermore, in comparison to competitive chromatographic techniques, chronopotentiometric method allows the analysis of foodstuffs under moderate price.

Determination of Lead(II) by Constant Current Stripping Chronopotentiometry Using Bismuth Film Electrode after Extraction of the Bromide Complex into Propylene Carbonate

AbstractA selective and simple method is presented for the determination of Pb(II) by constant current stripping chronopotentiometric analysis (CCSCP) using bismuth film electrode. This method is based on the extraction of the bromide complex into propylene carbonate, followed by CCSCP measurements in the organic phase. CCSCP studies revealed that Pb(II) gave a characteristic response at about −0.52 V vs. Ag/AgCl on the stripping chronopotentiogram (dt/dE curve) after recording a potential vs. time curve at 3.0 μA. The peak height of Pb(II) response was directly proportional to the initial metal concentration of the aqueous phase in the ranges of 1.0–22.0 μg dm−3 (correlation coefficient 0.997) when the optimized parameters were used. A detection limit (S/N=3) of 0.0880 μg dm−3 Pb(II) was obtained at 180 s deposition time. The relative standard deviation was 3.2% on replicate runs (n=12) for the determination of 10.0 μg dm−3 Pb(II). Analysis of certified reference materials has confirmed the applicability of the proposed method for determination of Pb(II) in soil and water samples.

Effect of electrode fabrication methods on the electrode performance for ethanol oxidation

Two palladium/carbon nanofibers modified glassy carbon electrodes, Pd/CNFs/GC-C and Pd/CNFs/GC-E, are fabricated by the conventional powder type method and by the electrophoretic deposition in conjunction with pulse electrodeposition method, respectively. Field emission scanning electron microscopy and high resolution transmission electron microscopy reveal that Pd particles are uniformly dispersed on the two electrodes and X-ray diffraction shows the average Pd particle size of the Pd/CNFs/GC-E electrode is slightly larger than that of the Pd/CNFs/GC-C electrode. Cyclic voltammetric analysis shows that the electrocatalytic activity of Pd/CNFs/GC-E electrode is better than that of Pd/CNFs/GC-C electrode for ethanol oxidation in alkaline media, although the latter has higher Pd loading than the former. This is believed to be due to the higher utilization of Pd catalyst on Pd/CNFs/GC-E electrode than on Pd/CNFs/GC-C electrode, which is confirmed by the electrochemically active surface area measurements. In addition, chronopotentiometric analysis shows the long-term operation stability of Pd/CNFs/GC-E electrode is better than that of Pd/CNFs/GC-C electrode.

Stripping chronopotentiometric analysis of cysteine on nano-silver coat polyquercetin–MWCNT modified platinum electrode

Silver nanoparticles coat polyquercetin (Qu) and multi-walled carbon nanotube (MWCNT) complex films were prepared using an electrochemical coupling strategy on platinum electrode (Ag/Qu/MWCNT/Ch/Pt). The new composite material was characterized by means of field emission scanning electron microscopy, X-ray photoelectron spectroscopy spectra, X-ray diffraction, and electrochemical techniques, which confirmed that polyquercetin plays an important role to obtain a great deal of uniformly dispersed silver nanoparticles and MWCNT complex film with a diameter of 10 ± 6 nm. The resulting Ag/Qu/MWCNT/Ch/Pt electrode shows a significant electrocatalysis for the redox of cysteine (CysH). The stripping chronopotentiometric analysis of CysH has been successfully used with a satisfying effect. A linear range of 1 × 10−10 to 9 × 10−8 M was obtained with a detection limit of 3 × 10−11 M (3σ) and sensitivity of 35 µA/nM. The films were also robust, surviving up to 100 consecutive cyclic voltammograms and sonication.

Development of disposable bulk-modified screen-printed electrode based on bismuth oxide for stripping chronopotentiometric analysis of lead (II) and cadmium (II) in soil and water samples

A bulk-modified screen-printed carbon electrode characterised for metal ion detection is presented. Bismuth oxide (Bi 2O 3) was mixed with graphite-carbon ink to obtain the modified electrode. The best composition was 2% Bi 2O 3 (wt%) in the graphite-carbon ink. The modified electrode with onboard screen-printed carbon counter and silver–silver chloride pseudo-reference electrodes exhibited good performance in the electrochemical measurement of lead (II) and cadmium (II). The electrode displayed excellent linear behaviour in the concentration range examined (20–300 μg L −1) with limits of detection of 8 and 16 μg L −1 for both lead (II) and cadmium (II), respectively. The analytical utility of the modified electrode was illustrated by the stripping chronopotentiometric determinations of lead (II) in soil extracts and wastewater samples.

Whole Cell Electrochemistry of Electricity-Producing Microorganisms Evidence an Adaptation for Optimal Exocellular Electron Transport

The mechanism(s) by which electricity-producing microorganisms interact with an electrode is poorly understood. Outer membrane cytochromes and conductive pili are being considered as possible players, but the available information does not concur to a consensus mechanism yet. In this work we demonstrate that Geobacter sulfurreducens cells are able to change the way in which they exchange electrons with an electrode as a response to changes in the applied electrode potential. After several hours of polarization at 0.1 V Ag/AgCl-KCl (saturated), the voltammetric signature of the attached cells showed a single redox pair with a formal redox potential of about -0.08 V as calculated from chronopotentiometric analysis. A similar signal was obtained from cells adapted to 0.4 V. However, new redox couples were detected after conditioning at 0.6 V. A large oxidation process beyond 0.5 V transferring a higher current than that obtained at 0.1 V was found to be associated with two reduction waves at 0.23 and 0.50 V. The apparent equilibrium potential of these new processes was estimated to be at about 0.48 V from programmed current potentiometric results. Importantly, when polarization was lowered again to 0.1 V for 18 additional hours, the signals obtained at 0.6 V were found to greatly diminish in amplitude, whereas those previously found at the lower conditioning potential were recovered. Results clearly show the reversibility of cell adaptation to the electrode potential and pointto the polarization potential as a key variable to optimize energy production from an electricity producing population.

Determination of cadmium and lead in vegetables by stripping chronopotentiometry

A method for the determination of cadmium and lead in vegetables by stripping chronopotentiometric analysis, after digestion of the sample with concentrated sulphuric acid and dry-ashing, is described. Metal ions were concentrated as their amalgams on a glassy carbon-working electrode previously coated with a thin mercury film and then stripped by a suitable oxidant. Potential and time data were digitally derived and E was plotted versus dt/dE−1, thus increasing both the sensitivity of the method and the resolution of the analysis. Quantitative analysis was carried out by the method of standard addition; good linearity was obtained in the range of examined concentrations, as was shown by the determination coefficients, which were 0.998 (n = 4) for cadmium and 0.993 (n = 4) for lead. Recoveries of 85–100% for cadmium and of 84–97% for lead were obtained from a sample spiked at different levels. Accuracy was demonstrated by analysis of a matching reference sample of cabbage. The detection limits were 1.8 ng g−1 of wet mass for cadmium and 5.1 ng g−1 of wet mass for lead. The relative standard deviations (mean of nine determinations), evaluated on a real sample, were 6.7 and 6.2%, respectively. Results obtained on 10 different commercial samples of pepper (Capsicum annuum), and egg plant (Solanum melongena) were not significantly different from those obtained by graphite furnace atomic absorption spectrophotometry technique. The average content was in the range 3.1–18.6 ng g−1 for cadmium and 38.2–64.3 ng g−1 for lead.

Determination of Ni (II) in beverages without any sample pretreatment by adsorptive stripping chronopotentiometry (AdSCP).

The purpose of this paper was to use adsorptive stripping chronopotentiometry for the determination of Ni (II) in worldwide consumed beverages without any sample pretreatment, using dimethilglyoxime (DMG) as complexing agent and a glassy carbon mercury film electrode as the working electrode. Ni (DMG)2 complex is adsorbed onto the mercury film at an electrolysis potential of -500 mV for 60 s and then reduced by a -5 microA constant cathodic current. The sensitivity of the method was studied for certified reference water and black tea in the pH range 6.5-11. At pH 9.5 in ammonia buffer, a detection limit of 0.2 microg L(-1) was achieved; the instrumental precision (expressed as rsd %) was 1.5%, and the accuracy, expressed as obtained recoveries both from certified and not certified matrixes, ranged from 93.0 to 95.5 %. The chronopotentiometric analysis executed on commercial beverages provided evidence that black tea samples were the richest source of Ni (II) (1500-3700 microg L(-1)), followed by coffee (100.0-300.5 microg L(-1)); bottled mineral water showed a Ni (II) concentration lower than 4.6 microg L(-1). Among alcoholic beverages, red wines presented the highest content of Ni (II) (55.5-105.0 microg L(-1)). Significant differences were noticed between Ni (II) levels of fermented and distillated alcoholic beverages; moreover, canned cola and beer did not show higher Ni (II) levels with respect to the glass-bottled products.