Anodic stripping voltammetry sample

The concentration of copper in a sample of sea water is determined by anodic stripping voltammetry using the method of standard additions. When a 50.0-mL sample is analyzed, the peak current is 0.886 )J,A. A 5.00-)J,L spike of 10.0-ppm Cu + is added, giving a peak current of 2.52 )J,A. Calculate the parts per million of copper in the sample of sea water. 

Anodic stripping voltammetry at a mercury film electrode can be used to determine whether an individual has recently fired a gun by looking for traces of antimony in residue collected from the individual s hands, fn a typical analysis a sample is collected with a cotton-tipped swab that had been wetted with 5% v/v HNO3. When returned to the lab, the swab is placed in a vial containing 5.00 mb of 4 M HCl that is 0.02 M in hydrazine sulfate. After allowing the swab to soak overnight,... 

The speciation scheme of Batley and Florence requires eight measurements on four samples. After removing insoluble particulates by filtration, the solution is analyzed for the concentration of anodic stripping voltammetry (ASV) labile metal and the total concentration of metal. A portion of the filtered solution is passed through an ion-exchange column, and the concentrations of ASV metal and total metal are determined. A second portion of the filtered solution is irradiated with UV light, and the concentrations of ASV metal... 

Anodic stripping voltammetry (ASV) has been used extensively for the determination of heavy metals in samples of biological origin, such as lead in blood. ASV has the lowest detection limit of the commonly used electroanalytical techniques. Analyte concentrations as low as 10 M have been determined. Figure 16 illustrates ASV for the determination of Pb at a mercury electrode. The technique consists of two steps. The potential of the electrode is first held at a negative value for several minutes to concentrate some of the Pb " from the solution into the mercury electrode as Pb. The electrode process is... 

Scarponi et al. [93] used anodic stripping voltammetry to investigate the contamination of seawater by cadmium, lead, and copper during filtration and storage of samples collected near an industrial area. Filtration was carried... 

Halliday et al. [396] have described a simple rapid graphite furnace method for the determination of lead in amounts down to 1 xg/l in polluted seawater. The filtered seawater is diluted with an equal volume of deionised water, ammonium nitrate added as a matrix modifier, and aliquots of the solution injected into a tantalum-coated graphite tube in an HGA-2200 furnace atomiser. The method eliminates the interference normally attributable to the ions commonly present in seawater. The results obtained on samples from the Firth of Forth (Scotland, UK) were in good agreement with values determined by anodic stripping voltammetry. 

Analysis of total zinc by anodic stripping voltammetry is problematic because of interference by the hydrogen wave in acidified samples, and due to the inability to detect organically complexed zinc at natural pH values near 8 [ 185]. An improved understanding of zinc in marine systems now requires rapid, sensitive analytical methods that are less prone to contamination, and that can be performed at sea [624],... 

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. 

Cuculic and Branica [788] applied differential pulse anodic stripping voltammetry to a study of the adsorption of cadmium, copper, and lead in seawater onto electrochemical glass vessels, quartz cells, and Nalgene sample bottles. Nalgene was best for sample storage and quartz was best for electroanalytical vessels. 

A kind of standard additions approach can also be used for the measurement of apparent complexing capacity. In this technique, labile copper is measured by differential pulse anodic stripping voltammetry after each of a number of spikes of ionic copper have been added to the sample [420]. 

Fig. 18b. 12. (a) Voltage-time profile for anodic stripping voltammetry (ASV) and (b) ASV of an unknown solution with two aliquot additions of 100 ppb each of Cd and Pb in the final solution. The peak at —190 mV is that of Cu present in the unknown. Experimental conditions Initial deposition potential, Ed = —800 mV, final potential = 0, deposition time, td — 120 s, quite time, tq — 30 s, step potential = 5 mV, pulse height = 20 mV, pulse delay = 100 ms, sampling width — 17 ms, and sampling frequency — 6000 Hz. 

Most of our understanding of the marine chemistry of trace metals rests on research done since 1970. Prior to this, the accuracy of concentration measurements was limited by lack of instrumental sensitivity and contamination problems. The latter is a consequence of the ubiquitous presence of metal in the hulls of research vessels, paint, hydrowires, sampling bottles, and laboratories. To surmount these problems, ultra-clean sampling and analysis techniques have been developed. New methods such as anodic stripping voltammetry are providing a means by which concentration measurements can be made directly in seawater and pore waters. Most other methods require the laborious isolation of the trace metals from the sample prior to analysis to eliminate interferences caused by the highly concentrated major ions. 

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. 

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 common approach used in a number of investigations is to modify the SPCE with a thin film of Hg. Recently, Palchetti et al. [152] have reported on the use of an SPCE modified with a thin film of Hg and cellulose (Methocel) for the determination of Pb2+, Cd2+ and Cu2+, using square-wave anodic stripping voltammetry. Detection limits of 0.3, 1 and 0.5 pgl-1 were obtained for Pb2+, Cd2+ and Cu2+, respectively deoxygenation of sample solution was found unnecessary. In all cases, linearity ranging from lpgl 1 to lmgl-1 and correlations of 0.9998 for Cd and Pb, and 0.9987 for Cu were obtained. 

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. 

Fig. 46.1. Standard addition analysis of gold in tap water sample spiked with 4.95 x 10-8 M AuCkf using anodic stripping voltammetry. Standard addition solution of 2.0 x 10-5 M gold. Eacc = 0.0 V tacc = 10 min v = 100 mV/s. (A) blank tap water (B) sample (C) 25 pL (D) 50 pL (E) 75 pL of the standard addition solution.

Separations may also be made on the basis of complex stability In such cases, a complexant is added to the sample and metal complexes are fractionated by a particular technique and their concentration is monitored (Apte and Batley, 1995 Miller and Bruland, 1997), typically by fluorescence (Aster et al., 1997), ultraviolet-visible (UV-Vis) spectrophotometry (Senesi, 1992 Bjorklund and Morrison, 1997), atomic absorption following solvent extraction (Itabashi et al., 1997), cathodic stripping voltammetry (CSV) (van den Berg et al., 1990 Yokoi et al., 1995 Maxwell and Smyth, 1996 Achterberg et al., 1997) or anodic stripping voltammetry (ASV)... 

The interference caused by chloride ion, Fe(III), and Cu(II) in the determination of nitriloacetic acid and EDTA in natural waters was removed by pre-treating samples (pH > 4) with cation exchangers. Some samples required additional treatment with an anion exchanger (pH 1). The analytes were complexed with Bi (III) before being determined by differential pulse anodic stripping voltammetry at the hanging mercury drop electrode (vs. Ag/AgCl. The detection limit was 0.1 pg/L for EDTA. 

De-proteinisation of diluted whole blood, and acid extraction of lead from proteins with 2M HNOs is the preparation chosen for the National Bureau of Standards reference method for blood-lead analysis [28]. Centrifugation of blood samples treated in this way yields clear supernatant fractions that contain all of the lead present, and which are easily dispensed into electrothermal atomisers using auto-sampling techniques. This method gave results that compared very well with those obtained using anodic stripping voltammetry, r = 0.975, for concentrations of 10—900 pg l-1 of lead in blood [15]. 

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 . 

Flow-injection analysis is also well-suited for the automation of anodic stripping voltammetry. Metals can be plated from the sample solution as it passes over the electrode. Stripping is then carried out in the deox-ygenated carrier stream (15, 34). The sample itself does not have to be deox-ygenated. Detection limits of 3 nM have been reported for lead by this technique (34). 

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