Additives anodic stripping

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. 

Whang, C. W., Page, J. A., vanLoon, G., and Griffin, M. R, Modified Standard Additions Calibration for Anodic Stripping Voltammetry, Anal. Chem. 56, 1984, 539-542. 

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]. 

A Ru(0001) sample, with vacuum deposited Cu, has been characterized by cyclic voltammetry by transferring to an electrochemical cell (16). Figures 4e-4h shows the anodic stripping curves for four different coverages of Cu. A single stripping peak was observed at +110 mV for 0.6 ML Cu and shifted to +145 mV for 5.2 ML Cu. This peak represents the removal of the first monolayer of Cu or Cu in direct contact with the Ru surface. The curve for 5.2 ML Cu shows an additional peak at -20 mV for the stripping of multilayer Cu. 

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. 

Fig. 3.2 Sono-square-wave anodic stripping voltammetric traces for an insonated deposition of 60 s at —1.5 V. Traces show background corrected standard additions to sono-solvent extracted laked horse blood solution (test solution 0.05%, by volume-blood). Each 10 (tl addition corresponds to an increase in copper concentration of 0.22 pg/1. Calibration graph shown inset (R = 0.9972) gives concentration of 1.637 mg/1 (reprinted from [64] with permission)...

Fig. 3.14 Anodic stripping square-wave voltammetry (ASSWV) of 1 X 10- M Dependence of peak currents on the accumulation time, itacc = —0.8 V, tacc = 5 s. (1) organic carbon-free water and (2) double-distilled water contaminated by unknown surfactant. Additions of Triton X-100 to (2) inmg/1 (3) 0.1, (4) 0.3, (5) 0.5, (6) 0.8 and (7) 1. Esv/ = 30 mV, / = 100 Hz and AE = 2.4 mV (reprinted from [247] with permission)...

First the responses Rq are measured for the sample. Thereafter K is determined by fitting the changes in the concentrations of the analytes in the sample, brought about by the standard additions, to the changes in the responses. Once all elements in the calibration matrix, K, have been determined, the concentration vector of the analytes in the sample is calculated. The method has been successfully applied to absorption spectrophotometry , anodic stripping voltametry and ICP-atomic emission spectrophotometry Attractive features of the method are that automation is very easy and automatic drift compensation is possible . A drawback is that all interferents should be known and be corrected for. 

The shape and position of the anodic stripping peak should be, in principle, independent of the starting material. This peak, however, is influenced by the conditions of metal deposition. Thus, as described by Komorsky-Lovric et al. [131], the stripping peak of electrochemically deposited lead differs from that recorded for lead compounds mechanically attached to graphite electrodes. Additionally, the presence of other depositable metals often gives rise to intermetallic compounds whose subsequent oxidative dissolution differs from those recorded for the individual metals... 

Shams E, Abdollahi H, Yekehtaz M, Hajian R (2004) H-point standard additions method in the analysis by differential pulse anodic stripping voltammetry Simultaneous determination of lead and thin.Talanta 63 359-364. 

The figure below shows a series of standard additions of Cu2+ to acidified tap water measured by anodic stripping voltammetry at an iridium electrode. The unknown and all standard additions were made up to the same final volume. 

Anodic stripping voltammograms of tap water and live standard additions Of 100 ppb Cu2. [From M. A Nolan and S. P. Kounaves, "Microlabricated Array of Ir Microdisks for Determination of Cu2 or Hg2 Using Square Wave Stripping Voltammetry" Anal. Chem. 1999, 71, 3567.]... 

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.

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. 

In anodic stripping voltammetry the mercury film and the metal ion to be determined are often co-deposited (called in situ mercury deposition). The thin mercury film has characteristics similar to a thin-layer cell, described in Section 9.10. Additionally, it can be easily used in hydrodynamic systems29. 

In both studies [3.107, 3.109, 3.175, 3.177, 3.178, 3.330-3.336], the decrease of 9A2(0 of fho adsorption peak A2 with increasing polarization time was used as a measure for the rate of 2D Me-S surface alloy formation. Anodic stripping after extended polarization at A gives additional and direct information on the kinetics of this process. However, such stripping experiments were not systematically carried out. 

Many researchers have attempted to determine mercury levels in the blood, urine, tissues, and hair of humans and animals. Most methods have used atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), or neutron activation analysis (NAA). In addition, methods based on mass spectrometry (MS), spectrophotometry, and anodic stripping voltametry (ASV) have also been tested. Of the available methods, cold vapor (CV) AAS is the most widely used. In most methods, mercury in the sample is reduced to the elemental state. Some methods require predigestion of the sample prior to reduction. At all phases of sample preparation and analysis, the possibility of contamination from mercury found naturally in the environment must be considered. Rigorous standards to prevent mercury contamination must be followed. Table 6-1 presents details of selected methods used to determine mercury in biological samples. Methods have been developed for the analysis of mercury in breath samples. These are based on AAS with either flameless (NIOSH 1994) or cold vapor release of the sample to the detection chamber (Rathje et al. 1974). Flameless AAS is the NIOSH-recommended method of determining levels of mercury in expired air (NIOSH 1994). No other current methods for analyzing breath were located. 

It is used in combination with square wave anodic stripping voltammetry (SWASV) using a PalmSens portable instrument (Palm Instrument BV, Houten, The Netherlands) for the measurement of metals such as Cu (II), Cd (II) and Pb (II) (labile metallic complexes and free metals) in water. These disposable sensors require no calibration for use in the screening mode, so, many samples may be tested for the presence or the absence of metals in water. The quantification can also be performed using the standard addition method in less than 15 min. 

The results for Cd, Cu and Pb in RM05 and RM12 were obtained with Palmsens - Screen Printed Electrode Voltametric Sensor (Simultaneous determination with square wave anodic stripping voltametry - SWASV) with standard addition... 

Figure 7.11. DPASV (differential pulse anodic stripping voltametry) polarograms obtained for the exudate solutions obtamed from either Fe-deficient (-Fe) or Fe-sufficient (4- Fe) ryegrass Lolium perenne ). at two levels of addition of Cu (0.14 and 0.71 xM). The dashed line indicates the electric potential corresponding to the labile Cu species (presumably dominated by Cu- ) that was obtained in the Cu solution without exudates (0.011 V). The shift of the peak toward more negative electric potential values and lower intensities is indicative of increasing complexahon of Cu with decreasing Cu concentrations and increasing phytosiderophore secretion as a result of Fe deficiency. (Adapted from Thomas et al., 2005.)...

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