Applications of Anodic Stripping Voltammetry

The application of anodic stripping voltammetry for the quantitative analysis of Cd, Pb, and Cu in natural waters is described in this experiment. 

Earlier work on the application of anodic stripping voltammetry to the determination of methods in seawater is reviewed in Table 5.9. 

Constantini, S., Giordano, R., Rizzica, M. and Benedetti, L. (1985). Applicability of anodic stripping voltammetry and graphite furnace atomic absorption spectroscopy to the determination of antimony in biological matrices. Analyst 110,1355. 

Mn(II) produces well defined reduction waves in most sample media and has been successfully determined in a wide range of sample types from natural waters to steel samples. Determination is usually carried out in alkaline conditions (pH 9.5), the reduction current appearing at —1.55 V versus SCE. Detection limits are generally of the order of 10 moll . Cr(III), Cr(n), and Ee(II) reduction peaks may, however, be a source of interference. The application of anodic stripping voltammetry (ASV) will lower the detection limits further for Mn. 

Applications of anodic stripping voltammetry, are chiefly for the determination of trace amounts of amalgam-forming metals (Fig. 5), while cathodic stripping voltammetry is used for determining species that form insoluble salts with mercury. The preconcentration stage allows determination in the concentration range 10 tolO M. 

The four variations of this technique are to be found in Table 14.2. The schemes of operation are shown in Fig. 14.6. Important applications for trace metals are the use of anodic stripping voltammetry (ASV) to determine trace quantities of copper, cadmium, lead and zinc, and adsorptive stripping voltammetry (AdSV) of trace quantities of nickel and cobalt—pre-concentration by adsorption accumulation of the oxime complexes followed by reduction to the metal is employed, as reoxidation of these metals in ASV is kinetically slow and does not lead to well-defined stripping peaks. 

In this section the instrumentation and the experimental procedure to determine the Cd, Cu and Pb total dissolved concentration is described in some detail. Several reviews regarding the general theoretical and experimental aspects of anodic stripping voltammetry and its application in sea water (or natural water) analysis can be found in the literature (15 17, 41, 59, 62, 67, 68). Details of the speciation procedure are reported below. 

G. Zhao, K. Liu, S. Lin, J. Liang, X. Guo, and Z. Zhang, Application of a carbon nanotube modified electrode in anodic stripping voltammetry for determination of trace amounts of 6-benzylaminopurine. Microchim. Acta 143, 255—260 (2003). 

Early work [400] on the application of cyclic and anodic stripping voltammetry to the determination of lead showed a poor correlation between peak current values and Pb11 concentration at high pH values. This is due to the low electrochemical activity of PbOH. 

Wang et al. [34] have introduced a new heated mercury film electrode based on a screen printed carbon substrate. It was used in anodic stripping and exhibited a significantly improved signal-to-noise ratio. A directly heated mercury film electrode for anodic stripping voltammetry has been described by Jasinski [35]. Different factors influencing the quality of analytical determination have been investigated. Renewed mercury electrodes and examples of their various applications have been reviewed in Ref. 36. Lovric and Scholz [37] have discussed the conditions... 

Daniele, S., B. Salvatore, M.A. Baldo, P. Ugo, and G. Mazzocchin. 1989. Determination of heavy metals in real samples by anodic stripping voltammetry with mercury microelectrodes. Part 2. Application to rain and sea waters. Anal. Chim. Acta 219 19-26. 

Anodic stripping voltammetry (ASV) is the oldest, and still the most widely used version of stripping analysis [3]. The technique is applicable to metal ions that can be readily deposited at the working electrode, and particularly for those metals that dissolve in mercury. In this case, the metals are being preconcentrated by electrodeposition into a small-volume mercury electrode (a thin mercury film or a hanging mercury drop). The preconcentration is done by cathodic deposition at a controlled potential and time. The deposition potential is usually ca. 0.3 Y more negative than E° for the least easily reduced metal ion to be determined. The metal ions reach the mercury electrode by diffusion and convection, where they are reduced and concentrated as amalgams ... 

The analytical use of GECE modified in situ by using bismuth solution for square wave anodic stripping voltammetry (SWASV) of heavy metals is also studied [36]. The use of this novel format is a simpler alternative to the use of mercury for analysis of trace levels of heavy metals. The applicability of these new surface-modified GECE to real samples (tap water and soil samples) is presented. 

A practical application of BCFMEs is the determination of gold by anodic stripping voltammetry [124], In this work, the BCFMEs were employed for the determination of tetrachloroaurate(III) complex in spiked samples of tap water. The methodology proposed is very easy and the details can be found in Procedure 46 in CD accompanying this book. 

Twenty years ago the main applications of electrochemistry were trace-metal analysis (polarography and anodic stripping voltammetry) and selective-ion assay (pH, pNa, pK via potentiometry). A secondary focus was the use of voltammetry to characterize transition-metal coordination complexes (metal-ligand stoichiometry, stability constants, and oxidation-reduction thermodynamics). With the commercial development of (1) low-cost, reliable poten-tiostats (2) pure, inert glassy-carbon electrodes and (3) ultrapure, dry aptotic solvents, molecular characterization via electrochemical methodologies has become accessible to nonspecialists (analogous to carbon-13 NMR and GC/MS). 

Anodic stripping voltammetry (ASV) was applied to the determination of copper traces present as Cu(dik)2. The differential pulse technique was used to strip the amalgamated copper from a hanging mercury drop electrode. The experimental variables such as scan rate of electrode potential, deposition potential, deposition time and stirring speed of the solution could be optimized. The linear range of the calibration plot was 0.05-1 (xM and the LOD was 0.014 fiM Cu(II). A method was used for the determination of copper in breast milk and beer as typical examples of application, consisting of minerahzation of the sample, extraction of Cu(II) from the aqueous solution with a 1 M solution of acacH in chloroform and ASV end analysis . 

Goto, M. Ikenoya, K. Kajihara, M. Ishii, D. Application of semi-differential analysis to anodic stripping voltammetry. Anal. Chim. Acta 1978, 101, 131-138. 

Liu KZ, Wu QG, Liu HI. 1990. Application of a Nafion - Schiff-base modified electrode in anodic-stripping voltammetry for the determination of trace amounts of mercury. Analyst 115(6) 835-837. 

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). 

The aim of this work is to demonstrate how the screen printed electrodes (SPEs) can be used for on site heavy metals monitoring in surface waters in the frame of the WFD. The sensors used consist of mercury-coated screen-printed electrodes coupled with square wave anodic stripping voltammetry (SWASV) (Palchetti et al., 1999). Three metals Cu, Cd, and Pb which are classically analysed in water matrices have been considered. Moreover, Cd and Pb belong to the priority substances list of the WFD. Performance criteria of the device are first established to evaluate the level of confidence of the method. The potential use of the device and its main advantages are then highlighted through two illustrative field applications. 

For an idea of some historic and more recent applications of electrochemical techniques, the reader is referred to Table 2.11 of applications providing examples of applications of electrochemical analytical techniques to elemental determinations in a variety of materials. Shearer and Morris (1970) report on the microdetermination of fluorine in organic compounds with a fluoride ion electrode following an oxygen flask combustion based on the careful work of Morris. Dabeka et al. (1979) developed a microdiffusion and fluoride-specific electrode determination of fluoride in foods. Determination of lead and cadmium in foods by anodic stripping voltammetry ... 

OsTAPCZUK P, Valenta P, Rutzel H and Nurn-BERG HW (1987) Application of differential pulse anodic stripping voltammetry to the determination of heavy metals in environmental samples. Sci Total Environ 60 1-16. 

The literature on procedures for PbB determination is abundant. Those techniques that have been shown to provide accurate and precise PbB determinations in routine use include anodic stripping voltammetry (ASV), flame atomic absorption spectrophotometry (FAAS), discrete sampling FAAS, and graphite furnace AAS (GF-AAS). The method most widely used for routine determination is AAS in its various modifications. The relatively slow analysis rate of ASV tends to limit the application of this technique to that of a backup or reference method. Whatever the technique which is applied, it should be emphasized that avoidance of contamination, careful handling of the blood samples and frequent intra- and interlaboratory checks are more important for ensuring precision and reliability than the method itself. 

Anodic stripping voltammetry is readily applicable for those metals that form an amalgam with mercury, for example, Ag, As, Au, Bi, Cd, Cu, Ga, In, Mn, Pb, Sb, Sn, Tl, and Zn. One important cause of interferences is intermetaUic compound formation of insoluble alloys... 

---