Stripping Voltammetric Determination Of Mercury Research Articles

Stripping voltammetric determination of mercury(II) based on SWCNT-PhSH modified gold electrode

Based on the unique electronic properties and high surface area of carbon nanotubes as well as the chemical interaction between thiol group and Hg(II), a novel electrochemical sensor for the determination of Hg(II) in water was fabricated by the immobilization of thiophenol functionalized single-walled carbon nanotubes (SWCNT-PhSH) onto the gold electrode surface. Various factors such as pH, preconcentration time, deposition potential, and deposition time influencing the determination of Hg(II) were thoroughly investigated in this study. Under optimal conditions, the electrochemical sensor exhibited a wider linearity range from 5.0nM to 90nM Hg(II) with a detection limit of 3.0nM (S/N=3). Interferences from other heavy metal ions such as Cr(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) ions associated with Hg(II) analysis were effectively inhibited. This novel sensor was successfully applied to determine Hg(II) in real water samples with good recovery, ranging from 97–103%. The analytical performance of the as-fabricated electrochemical sensor is superior to most existing sensors.

Adsorptive Stripping Voltammetric Technique for Monitoring of Mercury Ions in Aqueous Solution Using Nano Cellulosic Fibers Modified Carbon Paste Electrode

A simple carbon paste electrode modified with nano cellulosic fibers was developed for stripping voltammetric determination of mercury in aqueous solution. Prepared electrode was characterized using cyclic voltammetry and electrochemical impedance spectroscopy. Differential pulse stripping voltammetry in anodic direction was used for quantification of mercury. Experimental and instrumental parameters affecting the voltammetric measurements are optimized i.e. 0.1 M NaOH as supporting electrolyte, 1 mM acetate buffer of pH 3 as accumulating solvent with 10 min accumulation time. The peak current is proportional to the mercury concentration in a range 300–700 ng/ml, with a detection limit of 97 ng/ml. The relative standard deviation is 1.1 % for 400 ng/ml (five replicates). The proposed method was also applied to the determination of mercury in the presence of CTAB, SDS, Triton X-100 as a representative of cationic, anionic and neutral surfactants. The interference study shows that no effect up to 50-fold excess of cadmium, 25-fold of nickel, 100-fold of zinc and fivefold of copper is observed. The results obtained from the modified electrode are more accurate with lower standard deviation than the unmodified electrode.

Gold nanoparticles-modified screen-printed carbon electrodes for anodic stripping voltammetric determination of mercury in ambient water samples

We present here a simple, fast and cheap procedure for the determination of Hg(II) by square wave anodic stripping voltammetry (SWASV) at a commercial gold nanoparticles-modified screen-printed carbon electrodes (AuNPs-SPCEs), as a tool for environmental waters monitoring. The advantages of electrode nanostructuration are exploited, e.g. no stirring for the deposition step is needed. The surface of the gold nanostructured screen-printed carbon electrodes was characterized using SEM, XPS and electrochemical methods. All experimental variables involved in the voltammetric stripping method were optimized to develop a reliable method capable of measuring dissolved mercury in the low ng/mL range. The proposed method was tested with the NIST 1641d Mercury in Water Standard Reference Material with good agreement. The applicability of the AuNPs-SPCEs for Hg(II) determination in real ambient water samples, namely rain water, river water and industrial waste water, without any sample pretreatment, was successfully demonstrated.

Stripping voltammetric determination of mercury(II) and lead(II) using screen-printed electrodes modified with gold films, and metal ion preconcentration with thiol-modified magnetic particles

A novel approach to the electrochemical determination of heavy metals in tap water using anodic stripping voltammetry was developed using screen-printed electrodes modified with gold films. After optimisation of the experimental conditions, the screen-printed electrodes modified with gold films displayed excellent linear behaviour in the examined concentration range from 2 to 16 µg L-1 mercury and lead in 50 mM HCl with a detection limit of 1.5 µg L-1 and 0.5 µg L-1 for mercury and lead, respectively. In order to decrease the working range down to less than 1 µg L-1, a preconcentration step based on the use of magnetic particles modified with thiols was introduced into the protocol. Applying optimum binding conditions, the assay using screen-printed electrodes modified with gold films displayed excellent linear behaviour in the concentration range 0.1 to 0.8 µg L-1 in 50 mM HCl. The detection limit after a 120 s deposition time for mercury and lead were 0.08 µg L-1 and 0.02 µg L-1, respectively. The method has been applied to the determination of mercury and lead traces in tap water

Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode.

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L(-1) HCl solution containing 0.02 mol L(-1) KI, Hg(2+) was firstly preconcentrated at the MWNT film and then reduced at -0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about -0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I(-) remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg(2+) at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg(2+) over the range 8 x 10(-10)-5 x 10(-7) mol L(-1). The lowest detectable concentration of Hg(2+) is 2 x 10(-10) mol L(-1) at 5 min accumulation. The relative standard deviation (RSD) at 1 x 10(-8) mol L(-1) Hg(2+) was about 6% ( n=10). By using this proposed method, Hg(2+) in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.

Anodic Stripping Voltammetric Determination of Mercury in Water by Using a New Electrochemical Flow Through Cell

A flow through electrochemical cell was designed for the implementation of a simple, efficient, rapid and sensitive method for determination of mercury in water samples by anodic stripping voltammetry. A solid gold or a gold film electrode can be used as working electrode in a wall-jet configuration of the cell. The analyte is electrolyzed on the electrode surface by pumping the liquid sample through a continuous flow manifold at a flow rate of 8 mL/min. Deposition efficiency increased by increasing the velocity at which the sample arrives to the cell. After deposition of the analyte, it was stripped from the electrode by using a linear anodic potential scan at 35 mV/s. Geometric and hydrodynamic variables of the system were studied in order to optimize the analytical response. A detection limit of 0.05 ng/mL was reached by using a preconcentration time of 540 s. The repeatability expressed as relative standard deviation was always less than 3%. The method shows a good selectively and was successfully applied to the determination of mercury in different water samples.

Electrochemical Polishing of the Surface of a Gold Electrode and Its Effect on the Sensitivity of the Stripping Voltammetric Determination of Mercury(II)

The effect of two different techniques for the preparation of the surface of a gold electrode on the sensitivity of the stripping voltammetric determination of mercury(II) was studied. The electrochemical polishing of the electrode in a solution containing thiourea, sulfuric acid, and ammonium thiocyanate lowered the detection limit for mercury down to 2 ng/L and improved the reproducibility of mercury anodic peaks.

Self-assembled monolayers of 2-mercaptobenzimidazole on gold: stripping voltammetric determination of Hg(II)

Monomolecular level modification of electrode surfaces through a self-assembly approach is, of late, gaining importance in view of its many functional applications in areas such as molecular electronics, molecular recognition, electron transfer studies and electroanalysis. Self-assembled monolayer (SAM) modification of a gold electrode with 2-mercaptobenzimidazole (MBI) has been achieved. On this modified electrode, anodic stripping voltammetric determination of mercury at ppm/sub-ppm level concentrations has been successfully attempted. Pre-concentration, prior to stripping, has been effected through a non-electrolytic process involving chemical interactions between MBI and Hg(II). The results are described and discussed with a plausible scheme.

Stripping voltammetric determination of mercury at modified solid electrodes: I. Development of the modified electrodes

The paper describes the development of modified thick film graphite electrodes (TFGEs) for the stripping voltammetric determination of mercury. It is well known that mercury is determined best using gold electrodes. Therefore we have decided to modify the surface of a solid graphite containing electrode so that after the preliminary chemical or electrochemical reduction metallic gold appears in the modified layer on the electrode. Then mercury is deposited electrochemically from the sample solution on the metallic gold and is determined by anodic stripping voltammetry. To this end three different methods for the electrode modification have been chosen: One modified with a gold(III) solution from which gold was reduced chemically using various agents, one modified with a mixture of a gold(III) salt and Nafion and one modified with different insoluble gold(III) complexes. In method 2 as well as in method 3 the gold(III) was reduced cathodically. By virtue of their lifetime, their reproducibility and their sensitivity we preferred the electrodes modified by method 3 using a gold(III)–pyrrolindinedithiocarbamate (PDC) complex. Analytical applications for the mercury determination using this modified electrodes and the efficiency of this procedure will be published in a following paper.

Simultaneous cathodic stripping voltammetric determination of mercury, cobalt, nickel and palladium by mixed binder carbon paste electrode containing dimethylglyoxime

The present paper describes the construction and behaviour of a mixed binder carbon paste electrode (MBCPE) containing dimethylglyoxime (DMG) system appropriate for the cathodic stripping voltammetric determination of mercury(II), cobalt(II), nickel(II) and palladium(II). The mixed binder consisted of liquid paraffin and glycerol. At this electrode in a pH 4.80 buffer solution Hg(II), Co(II), Ni(II) and Pd(II) gave a sensitive cathodic stripping voltammetric wave at −0.93, −1.00, −1.07 and −1.25 V, respectively, which can be used to determine the metal ion concentrations down to 10 −8 M for 120 s of accumulation time. The recommended method was used for the determination of Hg, Co, Ni and Pd in rice, tea and human hair samples.

Preparation of a gold electrode modified with tri-n-octylphosphine oxide and its application to determination of mercury in the environment

A gold film electrode modified with a film of tri-n-octylphosphine oxide (TOPO) in a PVC matrix has been prepared and tested. Cyclic voltammetric experiments have shown that the electrode is useful for highly selective voltammetric determinations of a number of metals, primarily Hg, Cr, Fe, Bi, Sb, U and Pb. The electrode has been applied to the anodic stripping voltammetric determination of mercury in some environmental samples, such as river sediments. Concentrations of 0.02–50 ppm of mercury can be determined with good precision and accuracy, as demonstrated by analyses of reference materials. A selective decomposition of the samples at laboratory temperature decreases the danger of sample contamination and of volatilization of mercury.