Automated Determination of Cd^(2+) and Pb^(2+) in Natural Waters with Sequential Injection Analysis Device Using Differential Pulse Anodic Stripping Voltammetry

An electrochemical flow device has been developed for the determination of heavy metal ions(HMI)in water using multiwalled carbon nanotubes(MWCNTs)/Nafion(NA)/Hg electrode,by mean of diff erential pulse anodic stripping voltammetry coupled with sequential injection analysis.The accuracy of the determination was ensured by the great electrical conductivity of MWCNTs and the high adsorption capacity of Hg.NA was used for MWCNTs immobilization for the long-term application of the electrode.The mercury film was cleaned after determination and another one would form during deposition.A lower limit of detection and a wider determination range of Cd^(2+)and Pb^(2+)could be achieved using the automatically analytical device combining with the MWCNTs/NA/Hg-modified electrode.The real-time monitoring of Cd^(2+)and Pb^(2+)in fresh water using this device continued for 10 days.The results indicated that the method was potential for on-site and real-time determination of HMI in water samples.

Determination of Trace Thiocyanate by a Chitosan-Modified Glassy Carbon Electrode

A chitosan modified glassy carbon electrode(CMGCE) was employed for the determination of thiocyanate. The measurement was carried out by means of anodic stripping voltammetry. The effects of several experimental parameters, such as pH, the amount of modifier, deposition potential and deposition time were studied for analytical application, respectively. A liner response was obtained in the concentration range of 3 5×10 -8 - 9.3×10 -7 g/mL of SCN -. The detection limit was found to be 1.9×10 -8 g/mL. The method was satisfactorily used to detect SCN - in saliva.

Investigations of Thallium(Ⅰ) Underpotential Deposition on the Silver Rotating Disk Electrode and Its Analytical Application

The cyclic voltammetry(CV) and the square wave technique were used for the investigations of thallium(Ⅰ) underpotential deposition(UPD) on the silver electrode. A solution of 10 \{mmol/L\} HClO 4+10 mmol/L NaCl was selected as the supporting electrolyte. The calibration plots for Tl(Ⅰ) concentration in the range of 2×10 -9 -1×10 -7 mol/L were obtained. The detection limit was 5×10 -10 mol/L. For the solutions of 4 0×10 -9 mol/L thallium added before the urine sample pretreatment procedure, the average recovery was 105 6% with a relative standard deviation(RSD) of 15.5%.

Lead and Cadmium Distribution in Tubes of Galvanized Steel by Hot-Dip Used for Drinking Water Supply

The main objective of this work was to evaluate the presence of lead and cadmium in galvanized steel tubes by hot-dip used exclusively for drinking water supply.In this research,samples of galvanized tubes were removed from walls of residential buildings with 30 years of use.In the process of hot galvanizing,the manufacturing standards allow or for low cost conveniences,and the use of primary zinc ingot with 1.6%metallic impurities,such as lead and cadmium,is allowed,enabling the incorporation of these metals into the zinc coating deposited on the carbon steel.The associated corrosion of these tubes can release these toxic metals,contaminating the drinking water used by residents.The samples taken from the tubes were evaluated by a square-wave anodic stripping voltammetry technique,and the results for lead and cadmium suggested randomly distributed levels,indicating that the contents of these contaminants depend mainly on the quality of the added primary zinc and the operational conditions of the immersion bath.The metallographic evaluations performed on the samples of the galvanized tubes showed irregularities in thickness and even a lack of the zinc layer deposited on the carbon steel surface.These facts suggest that galvanized tubes should not be used for drinking water.

PSO-SVM applied to SWASV studies for accurate detection of Cd(II)based on disposable electrode

Square wave anodic stripping voltammetry(SWASV)is an effective method for the detection of Cd(II),but the presence of Pb(II)usually has some potential and negative interference on the SWASV detection of Cd(II).In this paper,a novel method was proposed to predict the concentration of Cd(II)in the presence of Pb(II)based on the combination of chemically modified electrode(CME),machine learning algorithms(MLA)and SWASV.A Bi film/ionic liquid/screen-printed electrode(Bi/IL/SPE)was prepared and used for the sensitive detection of trace Cd(II).The parameters affecting the stripping currents were investigated and optimized.The morphologies and electrochemical properties of the modified electrode were characterized by scanning electron microscopy(SEM)and SWASV.The measured SWASV spectrograms obtained at different concentrations were used to build the mathematical models for the prediction of Cd(II),which taking the combined effect of Cd(II)and Pb(II)into consideration on the SWASV detection of Cd(II),and to establish a nonlinear relationship between the stripping currents of Pb(II)and Cd(II)and the concentration of Cd(II).The proposed mathematical models rely on an improved particle swarm optimization-support vector machine(PSO-SVM)to assess the concentration of Cd(II)in the presence of Pb(II)in a wide range of concentrations.The experimental results suggest that this method is suitable to fulfill the goal of Cd(II)detection in the presence of Pb(II)(correlation coefficient,mean absolute error and root mean square error were 0.998,1.63 and 1.68,respectively).Finally,the proposed method was applied to predict the trace Cd(II)in soil samples with satisfactory results.

Graphene-platinum nanocomposite as a sensitive and selective voltammetric sensor for trace level arsenic quantification

A simple protocol for the chemical modification of graphene with platinum nanoparticles and its subsequent electroanalytical application toward sensitive and selective determination of arsenic has been described.Chemical modification was carried out by the simultaneous and sequential chemical reduction of graphene oxide and hexachloroplatinic acid in the presence of ethylene glycol as a mild reducing agent.The synthesized graphene-platinum nanocomposite(Gr-nPt)has been characterized through infrared spectroscopy,x-ray diffraction study,field emission scanning electron microscopy and cyclic voltammetry(CV)techniques.CV and square-wave anodic stripping voltammetry have been used to quantify arsenic.The proposed nanostructure showed linearity in the concentration range 10-100 nM with a detection limit of 1.1 nM.The proposed sensor has been successfully applied to measure trace levels of arsenic present in natural sample matrices like borewell water,polluted lake water,agricultural soil,tomato and spinach leaves.