Wave Adsorptive Stripping Voltammetry Research Articles

Glycine-modified Pencil Graphite Electrode as a Sensor for Caffeine Determination: A Voltammetric Study

Background: Caffeine (CAF) is a widely used chemical in foods and pharmaceuticals that is consumed by a lot of people every day. Overconsumption of caffeine can lead to some undesirable symptoms. However, CAF is considered a crucial nervous system stimulant. Aims: This study aimed to find an accurate and effective route for determining caffeine using voltammetric techniques. Objective: In this work, for the first time, a glycine (Gly) modified pencil graphite electrode (Gly/PGE) was used for the determination of caffeine (CAF) by Square Wave Adsorptive Stripping Voltammetry (SWAdSV) technique. Methods: The modification procedure of PGE by Gly was accomplished by performing the cyclic voltammetry (CV) technique for 10 cycles at a potential range of 0.8 to 1.8 V. Moreover, the characterization of Gly/PGE was done by applying the CV technique in aqueous and non-aqueous media and electrochemical impedance spectroscopy (EIS) in addition to the SEM technique. The movement type of CAF toward Gly/PGE was proven to be a diffusion-controlled process by conducting some measurements at different scan rates. The supporting electrolyte for the determination of CAF was studied, where 100 mM of sulfuric acid (H2SO4) provided the best result. Optimization of accumulation time, pulse size, and wave frequency were implemented and found to be 60 s accumulation time, 50 mV pulse size, and 25 Hz wave frequency. The stability of Gly/PGE was studied in different mediums, such as air, ultrapure water, and acetonitrile (CH3CN). Results: The determination of CAF under optimum conditions was within the linear concentration range of 0.1–75 μM, with a correlation coefficient of R2 = 0.9990. The limit of detection (LOD) and limit of quantification (LOQ) were 0.070 and 0.231 μM, respectively. Conclusion: An effective voltammetric methodology was suggested to determine CAF. This methodology has great promise to be applied in different matrices to determine CAF.

Silica graphite as an ink additive for stencil printed electrodes: A novel approach for electroanalytical determination of sulfanilamide

Silica-graphite composites present a high surface area, mechanical and chemical stability, and high functionality to be applied in electrochemical sensing. Indeed, those materials have been successfully employed to build composite electrodes such as carbon paste electrodes for a wide range of applications. Despite excellent performance, this kind of electrodes have been replaced by stencil printed electrodes (SPEs), emerging as a scalable alternative for manufacture offering sensors disposables, low-cost, customizable, and miniaturized. Based on this, herein a novel silica-graphite (SiG) composite is described as an ink additive aiming scalable production of SPEs with high functionality and surface area. The SPE as well as SiG were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, thermogravimetric analysis, and contact angle. After an accumulation step, SiG-SPE pretreated has shown a significant improvement on oxidation of sulfanilamide compared with unmodified SPE. Electrochemical surface activation and pre-concentration conditions were investigated to enhance sensitivity and selectivity. Under optimized conditions, silica-graphite stencil printed electrode (SiG-SPE) was employed for the electrochemical determination of sulfanilamide by using square wave-adsorptive stripping voltammetry (SWAdSV). It was possible to achieve a linear dynamic range (LDR) from 2 to 20 mmol L−1 with a limit of detection (LOD) and quantification (LOQ) of 0.34 and 1.13 mmol L−1, respectively. The stability of the sensors was evaluated over five weeks, and a decrease of around 5.5 % in response was observed compared to fresh electrodes. SiG-SPE also presented high selectivity and low matrix interference for sulfanilamide determination with a recovery range of 96.2–100.1 % for urine and 98.2–106.1 % for commercial fat milk. Those results suggest that SiG is a promising ink additive for the production of low-cost and high-performance sensors, showing enhanced analytical properties, mechanical resistance, and chemical stability.

Electrochemical Properties and Determination of Serotonin with Graphene/Coal Tar Pitch/Pencil Graphite Sensor Electrode using Square Wave Adsorptive Stripping Voltammetry Technique

In the present work, electrochemical and spectroelectrochemical behaviors of Serotonin (5-HT) were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Cyclic voltammetric experiments of 5-HT on graphene/coal tar pitch/pencil graphite electrode (GR/CTP/PGE) were carried out between 0.0 V and 1.8 V potential range at a scan rate of 100 mV s-1 with 20 cycles in non-aqueous media. Surface characterizations were performed using CV, EIS and scanning electron microscope (SEM). Effect of different pH values was investigated by square wave voltammetry (SWV) for determination of 5-HT. Optimization of accumulation time was determined using square wave adsorptive stripping voltammetry (SWAdSV) within potential range of -0.2 to +0.6 V. 5-HT standard solutions changing from 75 µM to 1.0 µM were prepared and the corresponding peak currents were measured. From the obtained data calibration equation was derived Ip = 0.0329C5-HT + 0.1511 with correlation coefficient (R2) 0.9958. LOD was 3.51x10-7 M and LOQ was 1.05x10-6 M.

Investigation of Electrochemical Properties and Behaviors of NBITEP Molecule; Availability of Sensor Electrode in Determination of Hg2+ with SWAdSV Technique

This Master's Thesis focuses on the synthesis and structural elucidation of 4-(2-((6-nitro-1h-benzo[d]imidazol-2-yl)thio)ethyl)phenol (NBITEP) molecule, along with its electrochemical behaviors. Electrochemical studies were carried out employing a glassy carbon (GC) electrode as the working electrode. The cyclic voltammetry (CV) technique was utilized for modification and characterization processes. Furthermore, the potential of the modified surface as a sensor electrode for Hg2+ ion detection was investigated using square wave adsorptive stripping voltammetry (SWAdSV). Detailed examinations were conducted in a phosphate buffer solution (PBS) medium specifically for Hg2+ ion detection, demonstrating the suitability of the reduced NBITEP modified GC electrode surface as a sensor electrode.

How to overcome the difficulty in assaying Ni in biodiesel samples? Extraction induced by microemulsion breaking and square wave adsorptive stripping voltammetry could be the answer

Herein, a simple, green, and relatively inexpensive approach to determine nickel (Ni) in biodiesel samples by square wave adsorptive cathodic stripping voltammetry (SWAdCSV) is presented. A method based on the accumulation of Ni as Ni(II)-dimethylglyoxime (Ni(II)(HDMG)2) on the glassy carbon electrode was carried out in a solution containing the aqueous phase extract (APhEx) obtained from an extraction induced by microemulsion breaking (EIMB), which was achieved by adding a few microliters of ultrapure water to a microemulsion composed of biodiesel, n-propanol and a diluted HNO3 solution. The LOD and LOQ were 0.2 μg L−1 and 0.8 μg L−1, respectively, and the accuracy was evaluated by recovery assays of spiked samples and by analyzing a standard reference material. Results obtained from a comparative method (HR-CS GF AAS) were also used for this evaluation. The method was applied to biodiesel samples produced from different feedstocks. To the best of the authors knowledge, it is the first time that: 1) Ni in biodiesel is determined by a voltammetric method; 2) EIMB is applied to extract Ni from this matrix and 3) this type of sample preparation method is used with adsorptive stripping voltammetry.

Fabrication of mesoporous carbon with a large surface area to achieve sensitive electrochemical sensing for nitazoxanide drug determination in human serum

Abstract Mesoporous carbon (MC) with a large surface area was developed to mix with the conventional carbon paste (CP) electrode. The developed MC/CP sensor had the highest sensitivity compared to many sensors made from other materials. A common drug, nitazoxanide (NTZ), was used as an application example. Using the MC/CP electrode and square wave-adsorptive stripping voltammetry (SW-AdSV), the concentration of NTZ in human serum was quantitatively estimated. We achieved a limit of quantification (LOQ) of 22 nM.

A simple electroanalytical methodology for determination of zaleplon by adsorptive stripping voltammetry in oral fluids

A glassy carbon electrode (GCE), modified with reduced graphene oxide (ErGO) (ErGO/GCE) was prepared for the determination of zaleplon, a common hypnotic pharmaceutical in synthetics and oral fluids. The modified electrode was evaluated using cyclic voltammetry, Raman spectroscopy, and scanning electrochemical microscopy (SECM). The electroanalytical studies were developed by square wave adsorptive stripping voltammetry (SW-AdSV) and parameters such as pH, accumulation potential, deposition time, and current response were optimized to determine zaleplon in Britton Robinson buffer. The validation was made using saliva-certified reference materials (Fusayama/Meyer Artificial Saliva and Artificial Saliva for Pharmaceutical Research showing good accuracy and reproducibility. The ErGO/GCE system showed a linear response between 10 and 130 µg/L at pH 10.0. The limit of detection was 5.30 μg L−1. The methodology was applied in the determination of zaleplon in saliva samples, obtaining excellent results (RSD < 10%), allowing the sensitive detection of zaleplon.

Electrochemical testosterone biosensor based on pencil graphite electrode electrodeposited with copper oxide nanoparticles

Accurately monitoring the blood levels of testosterone (TST) in a sensitive, simple, and rapid manner is of paramount importance for the diagnosis and treatment of various medical conditions, as well as for controlling pharmaceutical quality and facilitating doping detection. TST, the primary male sex hormone, plays a crucial role in facilitating human physical performance, protein synthesis, and the development of muscle mass. Consequently, TST and its analogues are frequently abused by athletes as performance-enhancing steroid in order to increase muscle mass and enhance their performance. The use of such steroids is strictly prohibited to guarantee fair play. In this study, we employed a pencil graphite electrode that was electrochemically modified with CuO nanoparticles (CuONPs) for determination of TST. The electrode response was significantly enhanced by approximately fourfold compared to the unmodified pencil graphite electrode (PGE) when electrodeposition CuONPs onto PGE surface was performed at a potential of −0.6 V for 200 s. The success of modification was confirmed through morphological analysis using scanning electron microscopy and energy-dispersive x-ray spectroscopy. Using square wave adsorptive stripping voltammetry analysis in Britton–Robinson buffer at pH 6.0, we demonstrated that the proposed sensor exhibited sensitivity to detect TST within a linear range of 5–200 nM. The detection limit of sensor was calculated 4.6 nM (1.32 ng ml−1). The sensor platform developed for the accurate, sensitive, and specific determination of TST holds tremendous potential for the development of point-of-care devices and their integration into lab-on-a-chip research.

The First Electroanalytical Study Of Umifenovir (Arbidol) Used As A Potential Antiviral Drug For The Treatment of SARS-CoV-2: A Voltammetric Quantification On The Boron-Doped Diamond Electrode By Using Anionic Surfactant Media

In this work, an electroanalytical procedure for sensing umifenovir (arbidol) by square wave adsorptive stripping voltammetry (SW-AdSV) was developed utilizing an anodically pretreated boron-doped diamond electrode. Measurements of umifenovir using cyclic voltammetry with phosphate buffer solution (PBS, 0.1 M, pH 2.5) revealed irreversible behaviour, adsorption-controlled as well as an ill-defined (+1.13 V, PA1) and a well-defined (+1.47 V, PA2) two oxidation peaks. Umifenovir oxidations depend critically on supporting electrolytes and pH. The second oxidation peak (PA2) current of the umifenovir was enhanced by adding sodium dodecyl sulfate (SDS, anionic surfactant) in the chosen supporting electrolyte. Umifenovir was quantified using its second oxidation peak (PA2) at about +1.39 V. Using the optimized condition, the oxidation peak current of PA2 showed a linear relationship for umifenovir determination in the concentration range from 0.005 to 1.0 μg ml−1 (9.73 × 10−9−1.95 × 10−6 M), with a detection limit of 0.0014 μg ml−1 (2.72 × 10−9 M) in PBS (PH 2.5) with SDS. Finally, the developed approach was successfully utilized to determine umifenovir in the pharmaceutical formulation and urine samples. To the best of our knowledge, this is the first electroanalytical approach for voltammetric sensing of umifenovir.

Fast and Simple Preparation of a Sensor Based on Electrochemically Reduced Graphene Oxide (rGO) for the Determination of Zopiclone in Pharmaceutical Dosage by Square Wave Adsorptive Stripping Voltammetry (SWAdSV)

AbstractThe interactions of zopiclone with electrochemically reduced graphene oxide (rGO) modified electrode were examined. A comparison of GC/rGO and glassy carbon electrode (GC) by electrochemical impedance spectroscopy and scanning electrochemical microscopy (SECM) shows that the modified surface is much less conductive than GC. The role of rGO is to act as a site of specific adsorption of the analyte. Molecular dynamics showed that the monoanionic form of zopiclone presents more interactions with defects of rGO. The analytical methodology allowed obtaining a linearity of 10–130 μg L−1, with a limit of detection of 2.14 μg L−1 using SWAdSV at pH 10.0.

On spot detection of nickel and cobalt from exhausted batteries by a smart electrochemical sensor

This work presents the realization and the application of an user-friendly electrochemical platform based on screen-printed electrodes for the simultaneous determination of nickel and cobalt ions in real samples by means of square wave adsorptive stripping voltammetry (SWAdSV). The sensor was realized by electrodepositing in situ a bismuth film onto graphite screen-printed electrodes (GSPEs). The sensor surface was fully characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).The experimental conditions for the determination of nickel and cobalt in the form of dimethylglyoximate complexes were studied and optimized. Linear calibration curves for Ni(II) and Co(II), determined individually and together, in the range 10–40 μg/L for nickel and 10–60 μg/L for cobalt, respectively, were obtained. The limits of detection for nickel and cobalt determination were 2.5 μg/L and 2.4 μg/L, respectively. The performance of the sensor in terms of reproducibility and selectivity was also studied. The applicability of the developed platform was assessed by determining nickel and cobalt in samples deriving from an industrial process of recycling exhausted batteries and in soil samples.

Square wave-adsorptive stripping voltammetric technique development and validation for the determination of budesonide in pharmaceuticals and biological fluids using graphite working electrode

The cyclic voltammetry method was preliminarily used to study the reversibility nature of the electrochemical behaviour of budesonide (BDN) compound. The square wave-adsorptive stripping voltammetry (SW-AdSV) technique was applied to evaluate an electrochemical reduction of BDN in the phosphate buffer pH 2.5. The ultra-trace graphite working electrode was used to accumulate BDN onto its surface. An SW-AdSV reduction peak was observed in the potential of −0.98 V using Ag/AgCl reference electrode and Pt auxiliary electrode. Different parameters ,such as pH, buffer solutions, accumulations time and potential, frequency, amplitude and scan were investigated, and convection rates parameters were studied to acquire a high reduction response. The repeatability, stability, recovery, calibration curve and limit of detection and quantification parameters were studied to evaluate the analytical performance of the SW-AdSV technique. Repeatability and stability were monitored for 20 µM of BDN to give a 0.29% relative standard deviation (RSD%) that was achieved for five measurements and a very stable current for 120 min. The linearity was evaluated by studying the calibration curve over the range of 2 –25 µM (n = 8), given a linear relation between BDN concentrations and SW-AdSV signals. The limits of detection (LOD) and quantification (LOQ) were calculated to become 40 nM (0.017 ppm) and 0.134 µM (0.0577 ppm), respectively. The developed and validated method was successfully applied to the electrochemical study of BDN in pharmaceuticals and biological fluids.

Analytical Comparison of Cefadroxil Determination by Square Wave Adsorptive Stripping Voltammetric and Spectrophotometric Methods

The goal of this research is to verify the proposed nano-silver amalgam paste electrode (Ag-nano-SPE) method to compare with a spectrophotometric technique based on derivatization with potassium periodate (KIO4 ), 2,4-dinitrophenyl hydrazine (DNP) and sodium hydroxide (NaOH) for the estimation of cefadroxil (CFDL) by square wave adsorptive stripping voltammetry (SWAV). The different parameters of both methods were optimized in detail separately and then compared their efficiency, selectivity, sensitivity and applications. The SWAV produced a reduction peak with a precise definition at -0.160 V while measuring CFDL in 0.04 molL-1 Britton–Robinson buffer at pH 4, accumulation potential (0.5 V), accumulation time (10 sec), and with stirring rate of 200 rpm. Whereas, the CFDL was measured at 515 nm (λmax) by UVVisible spectrophotometer after the derivatization by using 1.5 mL of 0.5 mM DNP, 1.5 mL of 6.52 mM KIO4 and 0.5 mL of 10 M NaOH solution at room temperature. The linear response for CFDL was found using the SWAV and spectrophotometric techniques along a linear dynamic range from 0.033 - 0.304 and 0.051 - 1.376 µM, respectively. However, the precision, detection limit and quantification limit of SWAV for CFDL in the samples and standards significantly lower (p &lt;0.01) as compared to spectrophotometric method. This indicates that the SWAV is more sensitive and selective than the spectrophotometric technique for regular CFDL analysis.

Voltammetric determination of sulfur in biodiesel microemulsion using a silver solid amalgam electrode.

Monitoring sulfur in biodiesel is of fundamental importance because even in low concentrations, it can harm the operation of the engine parts and increase the emission of toxic gases and particulate material. Hence, a simple, quick and sensitive adsorptive stripping voltammetry (AdSV) method based on a silver solid amalgam electrode (AgSAE) was developed to determine sulfur in biodiesel. The novel electrochemical method was evaluated through the linear sweep adsorptive stripping voltammetry (LSAdSV), square wave adsorptive stripping voltammetry (SWAdSV) and differential pulse adsorptive stripping voltammetry (DPAdSV) in a NH3/NH4+ buffer solution (pH 9.0), containing Na2SO3. The method was applied in biodiesel microemulsion samples under optimal conditions. To this end, a ternary phase diagram was constructed, employing three components: biodiesel/propan-1-ol/buffer solution. The microemulsion with the best response was found to be 25% NH3/NH4+ buffer (pH 9.0), 5.0% biodiesel and 70% propan-1-ol. The method reached a detection limit in the order of 10-7 mol L-1 of sulfur, and recovery values between 80% and 116%. The method was applied in the determination of sulfur in biodiesel, and the amount in the samples was found to be below the value stipulated by the regulatory agencies. The method can be a promising alternative for determining sulfur in the microemulsion of biodiesel, with the ability to provide a fast response regarding the quality of this biofuel.

An overview of recent developments of carbon-based sensors for the analysis of drug molecules

This review summarizes some recent developments in the fabrication of modified sensors and biosensors using carbon-based materials. The great potential of carbon-based electrodes as sensing platforms is exciting due to their unique electrical and chemical properties, high accessibility and high biocompatibility. Carbon-based materials are particularly interesting due to almost infinite possibility of their functionalization with a wide variety of organic molecules, biologically important compounds and pharmaceuticals. This review is specifically focused on recent developments in the utilization of various carbon-based electrodes in sensing devices for the electrochemical investigation of drug molecules. Various voltammetric techniques considered in this effort include linear sweep voltammetry (LSV), cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV), and square wave adsorptive stripping voltammetry (SWAdSV). The carbon-based electrode materials considered in this review comprise carbon paste, carbon nanotubes, graphite, graphene, and glassy carbon. The analytes chosen are some routinely used drugs such as paracetamol (PC), diclofenac sodium (DCF), 5-fluorouracil (5-FU), cetirizine (CTZ) and salbutamol (SAL). All here reported sensing electrodes produced very good results in electrochemical investigations of these drug molecules.

Novel voltammetric strategy for determination and electrochemical evaluation of progesterone by CPT-BDD electrode

In this study, electrochemical properties of progesterone at boron doped diamond (BDD) electrode surface were examined in strongly acidic medium (HClO4 and H2SO4). A fast, sensitive, selective and simple electroanalytic method has been proposed with a cathodically pre-treated (CPT-BDD) electrode in 0.5 M H2SO4 medium. Progesterone yielded a well-defined voltammetric response in 0.5 M H2SO4 medium at +1.51 V (vs. Ag/AgCl). Using the optimal square wave-adsorptive stripping voltammetry (SW-AdSV) conditions, the oxidation peak was used to determine of progesterone in the concentration range of 0.1 to 7.1 μM. Limit of detection is 0.012 μM; the relative standard deviation value for the concentration value of 3.1 μM (n = 11) was calculated as 4.87%. The developed voltammetric method was successfully applied to serum and drug samples.

A Review: Square Wave Adsorptive Stripping Voltammetry Determination ofPesticide and Ultra-trace Inorganic Ions in Environmental Samples

Environmental pollution caused by pesticides and ultra-trace amounts of inorganic ions in the different environmental samples has become an issue of serious concern in the last years. Thus, the development of novel, simple, fast, sensitive, and cheap methods for the detection of pesticide residues and ultra-trace inorganic ions in the environmental sample is very significant task now days. The SWAdSV can be conjuncted with different modified electrode such as SWAdSV with modified Hanging mercury drop electrode, SWAdSV with multi-walled carbon nanotube paste electrode, SWAdSV with boron-doped diamond electrode, SWAdSV with flow-injection analysis detection and etc. SWAdSV can be used to perform an experiment much faster than normal and differential pulse techniques, which typically run at scan rates of 1 to 10 mV/sec. Square wave voltammetry employs scan rates up to 1 V/sec or faster, allowing much faster determinations. A typical experiment requiring three minutes by normal or differential pulse techniques can be performed in a matter of seconds by square wave voltammetry. The aim of the review was the use of square wave adsorptive stripping voltammetry in conjunction with different modified electrode for the determination of pesticide and ultra-trace inorganic ions in environmental samples.

Nitrogen and sulfur co-doped graphene quantum dots/nanocellulose nanohybrid for electrochemical sensing of anti-schizophrenic drug olanzapine in pharmaceuticals and human biological fluids

A nanohybrid prepared from green source (nanocellulose, NC) and nitrogen, sulfur co-doped graphene quantum dots (N, S@GQDs) was prepared for the electrochemical detection of olanzapine (OLZ), atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. Polar groups on the surface of NC and N, S@GQDs provide more anchoring sites for adsorption of OLZ onto the electrode surface. In addition, it provides high conductivity, good mechanical strength, large surface area, and excellent electrical conductivity. The nanocomposite was characterized morphologically and electrochemically by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square wave adsorptive stripping voltammetry (SWAdSV). Under the optimized conditions, the modified electrode has a good response in the range of 1.5–90.0 × 10−8 M with LOD of 0.5 × 10−8 M. The proposed electrode offers high sensitivity, selectivity, and reliability towards OLZ detection. The SWAdSV was used to determine OLZ in pharmaceutical tablets, human plasma and urine with good recoveries % and reasonable RSD% values.

Determination of Chromium in Natural Water by Adsorptive Stripping Voltammetry Using In Situ Bismuth Film Electrode.

Development of adsorptive stripping voltammetry (AdSV) combined with in situ prepared bismuth film electrode (in situ BiFE) on glassy carbon disk surface using diethylenetriamine pentaacetic acid (DTPA) as a complexing agent and NO3− as a catalyst to determine the trace amount of chromium (VI) is demonstrated. According to this method, in the preconcentration step at Edep = −800 mV, the bismuth film is coated on the surface of glassy carbon electrodes simultaneously with the adsorption of complexes Cr(III)-DTPA. In addition to the influencing factors, the stripping voltammetry performance factors such as deposition potential, deposition time, equilibration time, cleaning potential, cleaning time, and technical parameters of differential pulse and square wave voltammetries have been investigated, and the influence of Cr(III), Co(II), Ni(II), Ca(II), Fe(III), SO42−, Cl−, and Triton X has also been investigated. This method gained good repeatability with RSD <4% (n = 9) for the differential pulse adsorptive stripping voltammetry (DP-AdSV) and RSD < 3% (n = 7) for the square wave adsorptive stripping voltammetry (SqW-AdSV), and low limit of detection: LOD = 12.10−9 M ≈ 0.6 ppb (at a deposition potential (Edep) of −800 mV and the deposition time (tdep) of 50 s) and LOD = 2.10−9 M ≈ 0.1 ppb (at Edep = −800 mV and tdep = 160 s) for the DP-AdSV and SqW-AdSV, respectively. This method has been successfully applied to analyze chromium in natural water.

Multianalyte voltammetric determination of traffic-linked metals in marine organisms employed as pollution bio-monitors

ABSTRACT A new procedure is proposed for the voltammetric determination of ultra-trace cadmium(II), copper(II), lead(II), platinum(II), palladium(II), rhodium(III) and zinc(II) by a single run of square wave adsorptive catalytic stripping voltammetry. The voltammetric cell was based on a typical three-electrodes set-up: working electrode (stationary hanging mercury drop), reference electrode (Ag|AgCl|KClsat) and auxiliary electrode (platinum). The supporting electrolyte contained the formazone complex together with dimethylglyoxime and the disodium salt of ethylenediaminetetraacetic acid. Validation of the analytical procedure was obtained by the analysis of standard reference materials (Mussel Tissue BCR-CRM 278, Oyster Tissue NIST-SRM 1566a). Comparison with spectroscopic measurements was performed. Good accuracy was achieved. The analytical procedure was finally applied to mussels and clams sampled on the mouth of Po river, employed as bio-monitors.