Voltammetric Determination Of Mercury Research Articles

Voltammetric determination of mercury(II) using a modified pencil graphite electrode with 4-(4-methylphenyl aminoisonitrosoacetyl)biphenyl

A sensitive and selective method for determination of mercury(II) with “4-(4-methylphenyl aminoisonitrosoacetyl)biphenyl (TKO)-modified pencil graphite electrode” was developed. All factors affecting determination process were optimized. Differential pulse voltammetry with 4-(4-methylphenyl aminoisonitrosoacetyl)biphenyl-modified electrode showed a linear response between 1.0 × 10−5 and 1.0 × 10−3 M (R 2 = 0.9994). The detection limit of this electrode was found as 5.85 × 10−7 M (S/N = 3). The effects of different cations on the determination of mercury(II) were investigated and found that modified electrode is highly selective. The developed method was applied for mercury determination in different water samples.

Voltammetric determination of mercury in biological samples using crown ether/multiwalled carbon nanotube-based sensor

Abstract An electrochemical assay for sensitive and selective determination of mercury was suggested. Preparation, characterization, and testing of the electro-catalytic activity of Crown-ether/multi-walled carbon nanotubes (MWCNTs)/CPEs were performed. The voltammetric responses of modified electrodes with various sensing elements and nanomaterials were carefully investigated. Consequently, improving the sensitivity and selectivity were achieved using a combination of 12-crown-4-ether and MWCNTs (10% w/w for each). A linear response was observed from 5 to 110 μg/ml, with the detection limit (S/N = 3) of 0.25 μg/ml. The method was interference free from many species and successfully applied for the determination of mercury in blood, urine or tab-water samples with a high accuracy and precision comparable with the reference method (Atomic Absorption Spectroscopy AAS).

Trace level voltammetric determination of heavy metals and total mercury in tea matrices (Camellia sinensis)

An analytical procedure regarding the voltammetric determination of mercury(II), copper(II), lead(II), cadmium(II) and zinc(II) by square wave anodic stripping voltammetry (SWASV) in matrices involved in food chain is proposed. In particular, tea leaves were analyzed as real samples. The digestion of each matrix was carried out using a concentrated HCl–HNO3–H2SO4 acidic attack mixture; 0.01molL−1 EDTA-Na2+0.15molL−1 NaCl+0.5molL−1 HCl was employed as the supporting electrolyte. The voltammetric measurements were carried out using a conventional three electrode cell, employing, as working electrodes, a gold electrode (GE) and a stationary hanging mercury drop electrode (HMDE). The analytical procedure has been verified on the standard reference materials Spinach Leaves NIST-SRM 1570a, Tomato Leaves NIST-SRM 1573a and Apple Leaves NIST-SRM 1515. For all the elements, the precision as repeatability, expressed as relative standard deviation (sr) was of the order of 3–5%, while the trueness, expressed as relative error (e) was of the order of 3–7%. Once set up on the standard reference materials, the analytical procedure was applied to commercial tea leaves samples.A critical comparison with spectroscopic measurements is also discussed.

Sequential voltammetric determination of mercury(II) and toxic metals in environmental bio-monitors: application to mussels and clams

This article reports the sequential voltammetric determination of Hg(II) and Cu(II) at gold electrode (GE), and of Cu(II), Pb(II), Cd(II), Zn(II) at hanging mercury drop electrode by square wave anodic stripping voltammetry in mussels and clams, possible environmental bio-monitors. The analytical procedure was verified by the analysis of standard reference materials: oyster tissue NBS-SRM 1566a, mussel tissue BCR-CRM 278 and cod muscle BCR-CRM 422. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were always less than 6%. Then, the analytical procedure was transferred and applied to mussels and clams sampled in two lagoon ecosystems connected with Adriatic Sea (Italy): the Goro Bay, located in the Po river mouth area and the lagoon ecosystem located in proximity to Ravenna. A critical comparison with spectroscopic measurements is also discussed.

Proposal for a mercury isolation procedure using cold vapor method in combination with voltammetric determination using a rotating gold electrode

Abstract The optimal process of pre-treatment and activation of gold rotating disc electrode (AuRDE) before voltammetric determination of mercury is proposed. This treatment encompasses polishing of the electrode surface, electrochemical cycling, and activation. This procedure both increases determination sensitivity as well as improves determination reproducibility. The detection limit on the working electrode achieved using this approach amounted to 8.26·10−10 mol L−1for direct mercury determination in water solution (applying 200 s running accumulation). The procedure of the quantitative mercury isolation from complicated sample matrix was developed as well. It provides better selectivity and significant increase of sensitivity of mercury determination. In case of mercury isolation from one liter of water the detection limit is 6.23·10−11 mol L−1 (analyzing a greater sample volume the determined concentration could be lower).

Study of an organically modified clay: Selective adsorption of heavy metal ions and voltammetric determination of mercury(II)

In this work, a hydrophilic clay, Na-montmorillonite from Wyoming, USA, was rendered organophilic by exchanging the inorganic interlayer cations for hexadecyltrimethylammonium ions (HDTA), with the formulae of [(CH 3) 3N(C 16H 33)] + ion. Based on fact that organo-clay has high affinities for non-ionic organic molecules, 1,3,4-thiadiazole-2,5-dithiol was loaded on the HDTA-montmorillonite surface, resulting in the 1,3,4-thiadiazole-2,5-dithiol-HDTA-montmorillonite complex (TDD-organo-clay). The following properties of TDD-organo-clay are discussed: selective adsorption of heavy metal ions measured by batch and chromatographic column techniques, and utilization as preconcentration agent in a chemically modified carbon paste electrode (CMCPE) for determination of mercury(II). The main point of this paper is the construction of a selective sensor, a carbon paste electrode modified with TDD-organo-clay, its properties and its application to the determination of mercury(II) ions, as this element belongs to the most toxic metals. The chemical selectivity of this functional group and the selectivity of voltammetry were combined for preconcentration and determination.

Voltammetric determination of mercury (II) in aqueous media using glassy carbon electrodes modified with novel calix[4]arene

A novel calix[4]arene derivative containing benzothiazole group was coated on glassy carbon electrode (GCE) and then applied to the recognition of mercury ion. Cyclic and square wave voltammetric results showed that the modified electrode selectively recognizes Hg 2+ ion in aqueous media. A new anodic stripping peak at −0.3 V (vs. Ag/Ag +) can be obtained by scanning the potential from −0.6 to 0.6 V, and the peak currents are proportional to the Hg 2+ concentration. The modified electrode in a 0.1 M H 2SO 4+0.01 M NaCl solution shows linear voltammetric response in the range of 25–300 μg l −1 and detection limit of 5 μg l −1 (ca. 2.5×10 −8 M). This modified GCE does not present any significant interference from alkali, alkaline and transition metal ions except for Pb 2+, Ag + and Cu 2+ ions. Only 500, 50 and 100-fold molar excess of Pb 2+, Ag + and Cu 2+ ions, respectively, can lead to voltammetric response comparable with that of Hg 2+. The proposed method was successfully applied to determine mercury in natural water.

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.

Development of a chemically modified electrode based on carbon paste and functionalized silica gel for preconcentration and voltammetric determination of mercury(II)

A mercury-sensitive chemically modified electrode (CME) based on modified silica gel-containing carbon paste was developed. The functional group attached to the silica gel surface was 3-(2-thiobenzimidazolyl)propyl, which is albe to complex mercury ions. This electrode was applied to the determination of mercury(II) ions in aqueous solution. The mercury was chemically preconcentrated on the CME prior to voltammetric determination by anodic stripping in the differential-pulse mode. A calibration graph covering the concentration range from 0.08 to 2 mg 1 −1 was constructed. The precision for six determination of 0.122 and 0.312 mg 1 −1 Hg(II) was 3.2 and 2.9% (relative standard deviation), respectively. The detection limit for a 5-min preconcentration period was 0.013 mg 1 −1. A study for foreign ions was also made.

Voltammetric determination of mercury(II) at a carbon paste electrode in aqueous solutions containing tetraphenylborate ion

The determination of mercury(II) ions can be achieved by monitoring the decrease in the oxidation peak of the tetraphenylborate ion in the presence of this metal ion at a carbon paste electrode. The reaction between mercury(II) and the tetraphenylborate ion results in the formation of diphenylmercury, thus providing the method with good selectivity over other metal ions. Using anodic stripping voltammetry in a neutral electrolyte, a linear dependence of the decrease of peak height was observed on increasing the mercury(II) concentration in the range 1 × 10 −6–8 × 10 −9 M mercury(II). Zinc(II), cadmium(II), lead(II), nickel(II), cobalt(II), tin(II), potassium(I) and ammonium(I) ions did not interfere at a 1000-fold concentration excess. Iron(III) and chromium(III) did not interfere at a 250-fold and 50-fold concentration excess, respectively. Following masking procedures, copper(II), bismuth(III) and silver(I) did not interfere at a 100-fold concentration excess. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal.