Cadmium stripping analysis

Drabek et al. [803] applied potentiometric stripping analysis to the determination of lead, cadmium, and zinc in seawater. The precision was evaluated by several duplicate determinations and was found to be in the range 5-16% relative, depending on the concentration level. The accuracy of the method was evaluated by comparison with other conventional methods, e.g., AAS and ASV, and good agreement between the methods was found. 

The stripping performances of Bi film on glassy carbon or carbon fiber substrates were examined very carefully by Wang et al. [17]. In addition to these materials, GECE (combined with bismuth film), a very easy to prepare and low-cost electrode, can also be used successfully for simultaneous stripping analysis of cadmium and lead. Zinc was also tried to be detected simultaneously with lead and cadmium but it was not possible to obtain undistorted and linearly increased peaks. The poor response to zinc can be probably attributed to the preferable accumulation of Bi on GECE rather than of Zn which is a result of the competition of these two metals for the GECE surface sites as also observed in other works [18]. 

Determination of lead and cadmium in tap water and soils by stripping analysis using mercury-free graphite-epoxy composite electrodes... 

After running the background stripping, add in the same electrochemical cell few microlitres from stock solutions of lead and cadmium so as to obtain a solution with a determined concentration. Run the stripping analysis and repeat it without removal of the electrodes for different concentrations. 

Rozali bin Othman, M., Hill, J.O., and Magee, R.J., Determination of lead and cadmium in biological samples by potentiometric stripping analysis, Fresenius Zeitschrift fuer Analytische Chemie, 326, 350-353, 1987. 

Figure 6.13. (a) Apparatus Tor stripping analysis, (b) Curve A Current-voltage curve for anodic stripping of cadmium. Curve B Residual current curve for blank. Reprinted with permission and adapted from R. D. DeMars and 1. Shairf, Anal. Chem. 29,182S (1957). Copyright by the American Chemical Society... 

For chemical monitoring, a list of priority substances has been established that includes metals such as cadmium, lead, and nickel. As far as metals are concerned, voltammetric techniques and more precisely electrochemical stripping analysis has long been recognized as a powerful technique in environmental samples. In particular, anodic stripping voltammetry (ASV) coupled with screen-printed electrodes (SPEs) is a great simplification in the design and operation of on site heavy metal determination in water, for reasons of cost, simplicity, speed, sensitivity, portability and simultaneous multi-analyte capabilities. The wide applications in the field for heavy metal detection were extensively reviewed (Honeychurch and Hart, 2003 Palchetti et al., 2005). 

Potentiometric stripping analysis, as stated in one review,92 "is not as general an analytical technique for the determination of metal traces as is graphite-furnace atomic absorption spectroscopy." It is used as a complementary technique for assay of some toxic metals in water (zinc, cadmium, lead, and copper in potable water and wastewater,93 94 and lead and thallium in seawater.95 The advantage of anodic stripping voltammetry (ASV) is summarized in two steps, which include electrolytic preconcentration and the stripping process. There are a number of interfering ions that can affect the... 

Adsorptive stripping voltammetry (ASV) is another specialised technique where the SMDE electrode is used for reducible species and carbon paste electrodes for oxidisable ones. This allows enrichment (by factors of 100-1000) of ions at the working electrode before stripping them off for measurement this improves the detection limits. This technique is rapid, sensitive (10 "M), economical and simple for trace analysis. The basic instrumentation for stripping analysis is apotentiostat (with voltammetric analyser), electrode and recorder. While voltammetry is generally very useful for compounds that do not have a chromophore or fluorophore, stripping analysis is the best analytical tool for direct, simultaneous determination of metals of environmental concern, e.g. lead, cadmium, zinc and copper in sea water. 

Amperometric techniques are very useful for detecting analytes that have been separated by chromatographic means but have no chromophores or other easy means of detection. Adsorptive stripping voltammetry (ASV) can be used for the direct sensitive analysis of metals in many types of sample matrix. For example, ASV has been used to determine cadmium, lead and zinc in urine, copper and bismuth in human hair tin in fruit juice, zinc and copper in fish and lead in gunshot residue. Stripping analysis can also be used for other applications such as determining flavanols in wine °, inorganic compounds such as cyanide and pharmaceuticals. ... 

Eriksen (1979) compared different wet digestion procedures for voltammetric stripping analysis of urine and preferred the use of a mixture of nitric, sulfuric, and perchloric acids. Satisfactory recovery (92-100%) of lead and cadmium from spiked samples was obtained. An effective procedure based on a rapid (20 min.) digestion of freeze-dried urine samples coupled with voltammetric analysis was reported (Golimowski et al., 1979). 

Md Noh M. R, Kadara R. O., and Tothill 1. E., Development of cysteine modified screen-printed electrode for the chronopotentiometric stripping analysis of Cadmium (II) in wastewater and soils extract. Anal. Bioanal. Chem., 382, 1175-1186, 2005. 

Figure 8.7 Captured PbS and CdS quantum dots attached to aptamer-bound proteins are dissolved and detected by electrochemical stripping analysis. The position and size of the corresponding metal peaks (cadmium and lead) reflect the identity of a concentration of the corresponding protein. [From Hansen et al. (2006).]...

Stripping analysis has been widely used for measuring trace metals in biological fluids. The use of stripping analysis for decentralized testing of blood lead in children has been particularly successful [46]. Measurements of mercury in fish [48], of antimony in gunshot residues [40], or of cadmium impurities in zinc plant electrolyte [55], represent typical food, forensic, and industrial applications, respectively, of stripping analysis. These,... 

Saei-Dehkordi, S.S. andFallah, A.A. (2011) Determination of copper, lead, cadmium and zinc content in commercially valuable fish species from the Persian Gulf using derivative potentiometric stripping analysis. Microchem. J., 98 (1), 156-162. 

Cadmium, copper, lead Flow potentiometric stripping analysis - [61]... 

Bismuth electrodes have been proposed as a substitute for mercury electrodes. A bismuth film on the surface of a heated carbon paste electrode indeed proved useful for stripping analysis of lead, cadmium and zinc traces [34]. An example belonging to the next chapter, i.e. analysis of DNA bases at a heated carbon paste electrode after adsorptive accumulation, also can be considered to be a kind of stripping analysis [35]. 

Quantum dots have been used as labels in electrochemical stripping analysis and ECL biosens-For example, chronopotentiometric stripping of cadmium from quantum dot cadmium... 

Jagner D, Aren K (1979) Potentiometric stripping analysis for zinc, cadmium, lead and copper in sea wato. Anal Chim Acta 107 29-35... 

Scarponi et al. [781] studied the influence of an unwashed membrane filter (Millpore type HA, 47 mm diameter) on the cadmium, lead, and copper concentrations of filtered seawater. Direct simultaneous determination of the metals was achieved at natural pH by linear-sweep anodic stripping voltammetry at a mercury film electrode. These workers recommended that at least 1 litre of seawater be passed through uncleaned filters before aliquots for analysis are taken the same filter can be reused several times, and only the first 50-100 ml of filtrate need be discarded. Samples could be stored in polyethylene containers at 4 °C for three months without contamination, but losses of lead and copper occurred after five months of storage. 

Nygaard et al. [752] compared two methods for the determination of cadmium, lead, and copper in seawater. One method employs anodic stripping voltammetry at controlled pH (8.1,5.3 and 2.0) the other involves sample pretreatment with Chelex 100 resin before ASV analysis. Differences in the results are discussed in terms of the definition of available metal and differences in the analytical methods. 

Cadmium in acidified aqueous solution may be analyzed at trace levels by various instrumental techniques such as flame and furnace atomic absorption, and ICP emission spectrophotometry. Cadmium in solid matrices is extracted into aqueous phase by digestion with nitric acid prior to analysis. A much lower detection level may be obtained by ICP-mass spectrometry. Other instrumental techniques to analyze this metal include neutron activation analysis and anodic stripping voltammetry. Cadmium also may be measured in aqueous matrices by colorimetry. Cadmium ions react with dithizone to form a pink-red color that can be extracted with chloroform. The absorbance of the solution is measured by a spectrophotometer and the concentration is determined from a standard calibration curve (APHA, AWWA and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). The metal in the solid phase may be determined nondestructively by x-ray fluorescence or diffraction techniques. 

As a result of that reductive process, a deposit of copper metal (denoted in Eq. 2.2 by s for solid ) is formed on the carbon electrode surface. The prominent anodic peak recorded in the reverse scan corresponds to the oxidative dissolution of the deposit of copper metal previously formed. The reason for the very intense anodic peak current is that the copper deposit is dissolved in a very small time range (i.e., potential range) because, in the dissolution of the thin copper layer, practically no diffusion limitations are involved, whereas in the deposition process (i.e., the cathodic peak), the copper ions have to diffuse through the expanding diffusion layer from the solution to the electrode surface. These processes, labeled as stripping processes, are typical of electrochemically deposited metals such as cadmium, copper, lead, mercury, zinc, etc., and are used for trace analysis in solution [84]. Remarkably, the peak profile is rather symmetrical because no solution-like diffusive behavior is observed. 

Radiochemical yields are 80-95% for zinc and quantitative for cadmium. The average relative standard deviation was 25% for zinc and better than 10% for cadmium. The detection limit of the method is 50 ppm cadmium in the ash. Analysis of two Illinois coals with unusually high cadmium content (17 and 21 ppm) gave results in good agreement with those obtained by atomic absorption and by anodic stripping voltammetry (4). The recent development and testing of a radiochemical method for the determination of zinc, cadmium, and arsenic in coal and fly ash, by Orvini et al. (14), has already been discussed in the section on arsenic. 

Analyses for "copper, cadmium, and lead were carried out continually by DPASV. Zinc determinations were excluded to permit use of a lower electrolysis potential. The samples were analyzed at pH 4.9 by sparging with carbon dioxide. An 8-min. electrolysis at —1.0 V vs. silver/ silver chloride and a 25-mV pulse were used during the Seattle-Saanich portion of the trip (Leg 1) while a 10-min. electrolysis and a 50-mV pulse were used from Saanich to Seattle (Leg 2). Application of the DPASV technique resulted in greater sensitivity and thus shorter plating times for the low levels encountered. It also afforded better resolution for "copper than linear-sweep ASV. It should be pointed out, however, that DPASV does not result in shorter analyses times because the stripping portion of the analysis is very slow. Nevertheless, it is worthwhile to limit the time of electrolysis because this also reduces the concentrations of interfering metals accumulated in the mercury fllm. Under the... 

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