Simple, insensitive to environmental matrix interferences method of trace cadmium determination in natural water samples (original) (raw)
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Determination of very toxic metal — Cadmium in natural water samples
Desalination, 2009
A potentiometric stripping method for a direct measurement of cadmium in various natural water samples using a Stripping analyzer M1 (designed and manufactured in Serbia) unit has been developed. In order to ascertain optimum conditions for the determination of the effect of the mercury time electrodeposition, the electrolysis potential and the solution stirring rate of the cadmium analytical signal have been examined. Linearity of the cadmium analytical signal was achieved within the wide range of the mass concentrations, from 1 μg/L to 15 μg/L. A detection limit of 0.10 μg/L was obtained, with a reproducibility of 3.55% expressed as the coefficient of variation. The accuracy of the method was confirmed by parallel analyses by flameless atomic absorption spectrophotometry as the reference method.
Physicochemical Problems of Mineral Processing
This article aims to investigate in detail to what extent surfactants affect the determination of cadmium by anodic stripping voltammetry. In recent years, the production and use of surfactants have been steadily increasing, so that their concentration in environmental water samples is rising. At the same time, it is known that organic compounds, such as surfactants, often hinder the voltammetric determination of trace elements by stripping. Non-ionic (Triton X-100, Brij 35, Tween 20, Tween 60, Tween 80), cationic (CTAB, CTAC, DTAB, HPC) and anionic (DSS, SDS) compounds were selected to investigate the effect of surfactants on the voltammetric signal of cadmium. At the same time, the extent to which the addition of Amberlite resins to the analysed solution eliminates the interfering effect of surfactants was tested. Three types of Amberlite resins XAD-2, XAD-7 and XAD-16 were selected for the study and the ratio of resin weight to solution volume was determined. Finally, the determi...
A sensitive voltammetric method has been developed for the determination of cadmium(II) utilizing a carbon paste electrode modi®ed with N-p-chlorophenylcinnamohydroxamic acid. The analyte was accumulated at the modi®ed electrode surface (via complexation) under open circuit and precisely controlled convective condition. It was then quanti®ed electrochemically by differential pulse anodic stripping voltammetry in a different nondeaerated electrolyte solution following medium exchange. Detailed experiments were conducted to establish the optimal carbon paste composition, pH and concentration of accumulation and stripping solutions, preconcentration time, bulk cadmium(II) concentration, and instrumental parameters. Two good linearities were obtained between the voltammetric current and cadmium concentration employing different preconcentration times. One was acquired in the concentration range 2.00610 77 ±3.20610 76 M Cd(II) (r 0.999) and the other from 4.00610 78 to 1.60610 77 M Cd(II) (r 0.999) with 1 min and 2 min preconcentration time, respectively. The detection limit was found to be 9.80610 79 M (1.1 ppb) Cd(II) with 2 min preconcentration time. For a series of six determinations of Cd(II) at 1610 76 M and 8610 78 M levels relative standard deviations of 2.6% and 5.5%, respectively, were achieved. Electrochemical cleaning was used to regenerate the surface rapidly and reproducibly; and this allows the use of a single modi®ed electrode surface in multiple analytical determinations over several weeks. Many common metal ions had little or no effect on the determination of cadmium(II). The method was veri®ed by the determination of trace cadmium(II) in municipal and mineral waters.
Eclética Química Journal, 2019
A voltammetric method for the cadmium quantification was developed using minimal instrumentation. A manual homemade potentiostat for linear voltammetry was used. An Ag reference electrode and auxiliary and working electrodes of writing graphite were employed for the electroanalysis. The electrolytic conditions for the quantification were stablished. Linearity, detection and quantification limits, precision and accuracy were evaluated. The conditions for the quantification were KCl 1 mol L-1 as supporting electrolyte and pH 5. The range of quantification was from 10-3 to 1.5∙10-2 mol L-1. The linear correlation (r), determination (R2) and adjusted (R2adj.) coefficients were 0.9986, 0.9972 and 0.9970. The detection and quantification limits were 3∙10-4 mol L-1 and 10-3 mol L-1. Results showed an acceptable repeatability, with coefficients of variation from 1.5 to 5.8% depending on the concentration. Uncertainty associated with the cadmium concentration was in the range of 1.2∙10-4 to 7∙10-5 mol L-1, diminishing with the increasing of the concentration. A good accuracy was observed, with recoveries between 86.84 and 109.64%.
Electroanalysis, 2010
A reliable screen-printed sensor for cadmium speciation analysis is presented here. Its development has been focused on the achievement of a reproducible and repeatable sensor. The electrode construction and its surface coating are discussed in detail. The optimized procedure has permitted to obtain very accurate sensors with detection limit of 0.2 mg (Cd) L À1 using SWASV for only 60 s of deposition time. The electrochemically accessible, i.e. potentially bioavailable, fraction of the cadmium present in an untreated river water sample has been successfully quantified without degassing. These results give a glimpse of the potential of this membrane-free sensor in real matrices.
International Journal of Environmental Analytical Chemistry, 2003
Nanotrace Cd determination in natural waters using two new flotation collectors, lead(II) heptyldithiocarbamate, Pb(HpDTC) 2 , and cobalt(III) heptyldithiocarbamate, Co(HpDTC) 3 , are presented. The optimization of the most important experimental parameters for flotation is given. Zeeman electrothermal atomic absorption spectrometry (ZETAAS) is used as an instrumental technique for Cd measurement. The results are compared with those obtained by other preconcentration procedures as independent methods. The limit of detection of ZETAAS using Pb(HpDTC) 2 as collector is 4.8 ng/L, while using Co(HpDTC) 3 it is 3.0 ng/L.
Journal of Analytical Methods in Chemistry
The present study introduces a novel electrode for rapid, highly sensitive, and selective electrochemical sensor for cadmium(II) using 5% N1-hydroxy-N1,N2-diphenylbenzamidine (HDPBA) modified carbon paste electrode (CPE) (HDPBA‒CPE). Surface characterizations and structural analysis of the proposed HDPBA‒CPE were performed using several analytical techniques. The voltammetric measurements of Cd(II) were conducted by cyclic voltammetry (CV) and square wave anodic stripping voltammetry (SWASV). Several experimental conditions such as composition and pH of buffer solutions, HDPBA composition, accumulation potential and time, and other voltammetric conditions were optimized. Cd(II) was preconcentrated on the modified electrode surface for 270 s using Britton Robinson (B-R) buffer (0.1 M, pH 4) at −1.0 V versus Ag/AgCl, followed by electrochemical oxidation of the accumulated Cd(II) in the positive scan of SWASV after a quiet time of 10 s. Under optimized parameters, the proposed method ...
Optical Chemical Sensor for Screening Cadmium (II) in Natural Waters
Journal of Sensor Technology, 2012
Membrane based optical chemical sensor (optode) for Cd(II) was developed by the immobilization of a dye 1-(2-Pyridylazo)-2-Napthol (PAN) in the Tri-(2-Ethylhexyl) Phosphate (TEHP) plasticized Cellulose Triacetate (CTA) matrix. Various combinations of PAN immobilized in the cellulose triacetate CTA and Polystyrene (PS) matrices plasticized with Tri-(2-Ethylhexyl) Phosphate TEHP, 2-Nitrophenyl Octyl Ether (NPOE) and Dioctyl Phthalate (DOP) were studied to arrive a suitable composition and found that the optode does not require any extractant to produce a distinct colour change on complexation with Cd(II). On sorption of Cd(II) in the optode matrix, PAN changes color of the optode from golden yellow to violet red having a maximum absorbance ( max = 553 nm) within 150 min of total equilibration time at pH = 7.5. The optode developed in the present work was studied for its analytical application for Cd(II) in the aqueous samples by spectrophotometry and as well as Flame Atomic Absorption Spectrophotometry (FAAS). This preconcentrated optode showed a linear response by UV-visible spectrophotometry at λ max = 553 nm over a concentration range of 10 ng•mL-1 to 500 ng•mL-1 of Cd(II) ions. Where as the aqueous solutions was also subjected to FAAS before and after equilibration of the optode and found to be linear in the concentration range of 250 ng•mL-1 to 5000 ng•mL-1 of Cd(II) ions. The optode found to be reversible and can be desorbed by equilibrating it with 0.01 mol•L-1 HNO 3. The applicability of the developed optode in real samples was studied by determining cadmium in the natural waters spiked with a known amount of Cd(II) ions.