Potentiometric Stripping Analysis Research Articles

On-site environmental water analyses by ICP-MS

ICP-MS analyses on drinking and vadose waters were performed on-site at a disused industrial/mining site in the former DDR. The results indicate the viability of performing on-site analyses of matrix samples for heavy metals while maintaining precision and accuracy better than other conventional techniques such as potentiometric stripping analysis (PSA). The precision, on a NIST 1643c water standard run frequently during the campaign, is better than 2% in most cases. Duplicate and triplicate runs performed on three samples prove precision comparable with, if not better, than conventional techniques and home-based laboratories. ‘Hot spot’ identification of heavy metal anomalies were located quickly and the environmental assessment report was accomplished within hours of the first sample being analysed. Polluted water samples are notable for their high Zn (maximum 12000 ppb), Mn (maximum 656 ppb), Ni (maximum 126 ppb), Co (29.8 ppb), As (maximum 22.5 ppb), Sb (maximum 54.9 ppb) and Pb (maximum 184 ppb).

Potentiometric Stripping Analysis: A Review

Abstract A bibliographic review (150 references) on potentiometric stripping analysis (PSA) is performed. Theoretical, instrumental, analytical applications and advantages, and inferences of other modern PSA techniques are considered, like derivative PSA, constant-current PSA, multichannel potentiometric monitoring stripping analysis, differential PSA, constant-current enhanced PSA, derivative adsorptive PSA, kinetic PSA and reductive PSA. Implementation of PSA in flow systems is also considered, namely continuous-flow and flow-injection systems.

Application of potentiometric stripping analysis for speciation of copper complexes with adsorbable ligands on the mercury electrode

Potentiometric stripping analysis (PSA) was used for the determination of equilibrium parameters of complexes of copper(II) with humic acids (HA, adsorbable at the mercury electrode surface), at pH 6.5. The calculations were performed by the DeFord-Hume's method or through the material balance of the metal together with the equation dt dE = C D ̄ 1 2 [Cu] t , ( t is the stripping time, E is the working electrode potential, C is a constant, D ̄ is the average diffusion coefficient of all forms of metal present in the solution and [ Cu] t is the total copper(II) concentration). For comparison, the study was also carried out by differential pulse anodic stripping voltammetry (DPASV) and by potentiometry with a copper(II) ion-selective electrode (ISE). It was found that for HA concentrations lower than 0.1 mmol/l the adsorption phenomena do not interfere in the determination of the equilibrium parameters ( K def ) by PSA, but interfere markedly in DPASV. The values of the function log K def = f( log θ) obtained by both PSA and ISE techniques fit the same isotherm, the form of which is typical for chemical systems involving heterogeneous ligands. In contrast, the values of log K def obtained by DPASV fit a non-typical isotherm in total disagreement with that obtained by ISE.

Determination of copper in human plasma by stripping potentiometry on a mercury film electrode in ethylenediamine medium

The use of ethylenediamine improves the determination of copper by potentiometric stripping analysis on a mercury film electrode, with respect to the usual determination method in acidic medium. The influence of chemical and methodological parameters is discussed, and the reliability of the method is checked with certified reference materials. Influence of the acid digestion protocol in open and high pressure closed vessels is investigated. The method developed has been applied to the measurement of the copper level in mineralized human plasma samples. The results have been compared with those obtained by electrothermal atomic absorption spectroscopy in a graphite furnace.

Ion exchange micro columns for on-line preconcentration of heavy metalsII. On-line break-through test for zinc, cadmium and lead.

An on-line break-through test for zinc, cadmium and lead has been carried out by means of a flow-through cell and computerized potentiometric stripping analysis. This test has been applied to seventeen ion-exchange materials and enabled within a short time a predecision about the suitability of a resin for a special preconcentration problem. For the determination of the three trace elements in drinking water five ion exchangers are found to be appropriate without restriction and eight resins with some restrictions (not suitable for all three elements, weak matrix influences).

Oscillating flow injection stripping potentiometry

A fully computerized flow injection (FI) manifold with a peristaltic pump allowing periodic alternation of the flow direction and incorporating a detector system capable of performing potentiometric stripping analysis (PSA) is outlined. The measuring technique has been named oscillating flow injection stripping potentiometry (OFISP). It combines the attractive features of both traditional flow injection analysis (FIA) and batch PSA and at the same time overcomes some of the most serious drawbacks of the latter resulting from the fact that potentiostatic deposition and chemical stripping occur in the same solution. An experimental study of the influence of the main parameters of the flow system on its behaviour was performed using Cu(II) solutions in the μg l −1 concentration range as samples. The potentiostatic deposition was carried out on an Hg precoated glassy carbon electrode and Hg(II) ions were utilized as oxidant in the chemical stripping step.

Signal enhancement of potentiometric stripping analysis using digital signal processing

Four digital signal processing methods, moving average smoothing, polynomial smoothing, rectangular low pass filtering and exponential low pass filtering have been compared in this study of potentiometric stripping analysis (PSA) data. For the filtering methods, a new procedure is introduced based on treating the potential coordinate as mathematically equivalent to a time coordinate to transform data to the frequency domain. After Fourier transformation, each method has yielded signal-to-noise ( S N ) improvement over the original data, for example exponential low pass filtering providing a 2.3 times S N enhancement. Peak area measurement was unaffected by the two smoothing methods, while an undesirable increase in peak area was observed in the two filtering methods. A linear peak area-concentration relationship was retained in all cases. The original peak height calibration is poorly correlated linearly, although the complex curve is reproducible. However, after digital signal processing, peak height as the measuring parameter gave a good linear relationship to concentration. The filtering approach which allows optimum filtering and best peak resolution was readily established. The resolution of overlapping potential peaks, using copper and bismuth peaks as the example, was best improved using the rectangular low pass filtering method.

Application of potentiometric stripping analysis for speciation of copper complexes with a non-adsorbable ligand on a mercury electrode

Potentiometric stripping analysis (PSA) was used for determination of conditional stability constants (δ′) of copper(II) complexes. Glycine was used as a model of a non-adsorbable ligand on the mercury electrode that forms well defined 1:1 and 1:2 copper(II)-glycine complexes, which are labile within the time scale of the analytical technique. The calculations were performed by the DeFord-Hume method, which was applied to the shifts in peak potential ( dt dE vs. E) provoked by the presence of different concentration of the ligand in the metal solution. For comparison purposes, the study was also carried out by differential pulse anodic stripping voltammetry (DPASV). The results obtained by PSA both at pH 6.0, log β′ 1 = 5.0 ± 0.2 and log β′ 2 = 7.6 + 0.2, and at pH 6.5, log β′ 1 = 5.7 ± 0.6 and log β′ 2 = 8.5 ± 0.4 (standard deviations are given), were in agreement with those obtained by DPASV and from the literature, which indicates that PSA is suitable for this type of study.

Determination of formation constants of metal complexes by potentiometric stripping analysis

AbstractA method based on the data obtained from complexometric titration followed by potentiometric stripping analysis is developed. Optimization of the experimental conditions, namely: choice of the proper oxidant, deposition potential, plating time, concentration, and pH, considerably reduced the errors contributed by kinetic dissociation. This method was applied to ethylenediaminetetraacetic acid (EDTA) titration with lead and gave a formation constant for Pb‐EDTA that agreed well with literature values. The method may be applied to the determination of formation constants of 1 : 1 complexes with Kf values about 1020. The feasibility of the metal ion depends mainly on the solubility of the metal in the mercury in addition to its reversible behavior at the thin mercury film electrode.

Potentiometric stripping analysis vs. differential pulse anodic stripping voltammetry for copper(II) analysis at relatively positive deposition potential

A comparative study of potentiometric stripping analysis (PSA) and differential pulse anodic stripping voltammetry (DPASV) for copper analysis at relatively positive deposition potential, E d = −0.3 V vs. Ag AgCl(s) , 3 mol/l KCl, was carried out both in 0.01 mol/l KNO 3, pH 6.5, and in a saline water (ionic strength ca. 0.5 mol/l, pH 7.5). A deposition time of 3 min was used. When a static mercury drop electrode was used as working electrode, PSA allowed determinations of copper in both media with the following limits of detection (LOD): 0.15 μmol/l, for 0.01 M KNO 3, and 0.28 μmol/l for saline water. DPASV allowed copper determination in 0.01 M KNO 3 with LOD = 0.18 μmol/l, but not in the saline water, because the baseline was not well-defined. When a thin mercury film was used as the working electrode, the DPASV defection capability improved markedly in 0.01 M KNO 3, LOD = 0.018 μmol/l, but the determination of copper in the saline water was still unfeasible at E d = − 0.3 V. These results indicate that PSA can be applied to copper analysis in saline waters at more positive deposition potentials than DPASV, but the LOD of PSA was too high to allow copper speciation in natural waters. In addition, it was verified that the presence in the solution of organic matter (humic acids 0.12 or 0.30 mg C/l), adsorbable at the working electrode, had no effect on the PSA signal, but markedly interfered in the DPASV response.

Reductive potentiometric stripping analysis of lead with potassium ferrocyanide as the reducing agent on a glassy carbon electrode

Reductive potentiometric stripping analysis (RPSA), with potassium ferrocyanide as the reducing agent on a glassy carbon electrode, is applied for the determination of lead over the range 2 × 10−8–5 × 10−6 M. The relative standard deviation of 2 × 10−6 M lead for ten consecutive measurements is 2.5%. This technique has been used to determine the minute amount of lead in a human hair sample solution.

Digestion-free determination of heavy metals (Pb, Cd, Cu) in honey using anodic stripping differential pulse voltammetry and potentiometric stripping analysis

Experiments have been carried out to assess the potential of differential pulse voltammetry and potential stripping analysis for determining Pb, Cu and Cd directly in dissolved honey samples using a flow-through cell. With the hanging mercury drop electrode Pb alone can be determined only if the electrode is first modified in-situ with Triton X 100 to increase the separation between the Pb peak and a broad, interfering adsorption peak which overlaps the Cu peak. If the (more sensitive) thin film mercury electrode is used the interference encountered is less so also Cu and Cd can be determined. With potentiometric stripping analysis Cu and Pb can be determined using normal procedures. The determination of Cd, however, can only be carried out if the concentration of the oxidizing agent [Hg(II)] in solution is decreased. A good agreement has been obtained between the values found and those obtained after high pressure digestion of the samples.

Portugal — Study of the lability of copper(II)-fulvic acid complexes by ion selective electrodes and potentiometric stripping analysis: In ANAL. CHIM. ACTA (293/3 (261–270) 1994) H.M.V.M. Soares and M.T.S.D. Vasconcelos of the Faculty of Science report a “Study of the lability of copper(II)-fulvic acid complexes by ion selective electrodes and potentiometric stripping analysis”

Portugal — Study of the lability of copper(II)-fulvic acid complexes by ion selective electrodes and potentiometric stripping analysis: In ANAL. CHIM. ACTA (293/3 (261–270) 1994) H.M.V.M. Soares and M.T.S.D. Vasconcelos of the Faculty of Science report a “Study of the lability of copper(II)-fulvic acid complexes by ion selective electrodes and potentiometric stripping analysis”

Potentiometric Stripping analysis—a new technique for tissue analysis used to correlate chemical speciation with progress of wound healing

ABSTRACTPSA has been adapted to the analysis of 20 mg samples of skin for copper at 12 and zinc at 33 ppb of dry mass. This technique can be applied to other metal analyses, can be extended to human samples and produces data which, used as input, will permit considerably more precise chemical speciation data reflecting bioavailabilities etc. Other methods of analysing such low levels are reviewed and all suffer from disadvantages compared with PSA when used in a hospital environment—extremely expensive, highly skilled technologists required, slow turn around of results, large sample volumes necessary, non-applicable to physiological concentrations. The PSA method can now be applied to assessing and monitoring treatment of copper and zinc levels for patients.

Field Screening of Chromium, Cadmium, Zinc, Copper, and Lead in Sediments by Stripping Analysis

Stripping analysis (SA) was successfully employed for field verification of metals contaminants in soils and sediments at hazardous waste sites. Microwave digestion procedures were tailored to meet the needs of field activities and electrochemical measurements. An adsorptive stripping voltammetric (AdSV) scheme was used for monitoring total chromium and for chromium speciation, while conventional anodic stripping voltammetry (ASV) and potentiometric stripping analysis (PSA) were used for measuring cadmium, zinc, copper, and lead. The results demonstrate that SA is capable of on-site identification of contaminated layers in soils and sediments. Concentration values measured by SA correlated well with those obtained by U.S. Environmental Protection Agency (EPA)-approved atomic or mass spectroscopy methods. The remarkable sensitivity, portability, low-power need, and low cost of SA make it an attractive choice for on-site analysis of selected metals during site characterization and remediation activities. 12 refs., 6 figs., 2 tabs.

Printed microelectrode array and amperometric sensor for environmental monitoring

A disposable electrochemical sensor for the determination of heavy metal traces has been designed for environmental field analysis. The sensor is supported on a polycarbonate film and consist of an amperometric transducer in combination with an adjacent silver-ink reference electrode. The transducer itself is composed of a network of carbon disc microelectrodes. This array of microelectrodes covers a sensing area of 5 × 5 mm and is made up of some 1000–3000 electrodes. Individual disc microelectrodes measuring 15 μm diameter, have a recessed geometry with hole depth of less than 10 μm and centre-to-centre separation between 100 and 300 μm. A novel three-stage fabrication process based on conventional thick-film printing techniques, vacuum polymerisation of a dielectric and a uv excimer laser photoablation process was used to pattern the disc array structure. This microfabrication method has been evaluated on a laboratory scale and batch production. Amperometric performance and structural characteristics of the electrochemical sensor have been examined by chronoamperometry and electron microscopy. Variations in the sensor current response were studied in order to reduce the diffusion shielding characteristics of individual discs. An optimal microelectrode spacing was assigned to the sensor of 160 μm giving more than one thousand discs per device. The printed sensor is currently under development for single-use field measurements of heavy metals using potentiometric stripping analysis.

Potentiometric Stripping Analyses: Using a Flexible, Low-cost Computerized Instrument

This paper describes a simple and economic way to construct a computerized potentiometric stripping analysis system for teaching and research purposes.

Effects of surface-active substances in square-wave voltammetry and potentiometric stripping analysis of amalgam-forming metal ions

The influence of surface active substances (SAS) (Triton X-100, sodium dodecyl sulfate and dodecyl pyridinium chloride (DPC)) on the potentiometric stripping analysis (PSA), square-wave voltammetry (SWV) and anodic stripping square-wave voltammetry (ASSWV) of Cd2+, Cu2+, Zn2+ and Bi(III) are measured for various contact times and detergent concentrations. Diagnostic criteria for the presence of SAS in electrolytes are reported. Zinc ions accumulate in the adsorbed layer of DPC, probably as a ZnCl+ complex. An anomalous dependence of zinc SWV peak currents on the delay time is observed.

Study of the lability of copper(II)-fulvic acid complexes by ion selective electrodes and potentiometric stripping analysis

Two electroanalytical techniques, direct potentiometry with a copper ion selective electrode (ISE) and potentiometric stripping analysis (PSA), were used to evaluate the lability of copper-fulvic acid complexes (Cu-FA) in 0.5 mol/l sodium perchlorate and in synthetic sea water. The determinations were performed at pH 6.5, and for sea water also at pH 7.5. By ISE potentiometry, in 0.5 mol/l sodium perchlorate, the FA total complexation capacity (CC) in the 1–150 mg/l FA concentration range, as well as the 1:1 Cu-FA conditional stability constants for two different types of binding sites ( K 1 and K 2) and the respective metal-binding capacities ( C 1 and C 2; C 1 + C 2 = CC) were obtained. It was found that CC was approximately constant over the FA concentration range studied: 1.81 mmol/g of FA or 5.2 mmol/g of total organic carbon (TOC). For 0.2–18 ⋎FA⋎ t/⋎Cu⋎ t molar ratio range, the values of the complexation parameters were as follows: log K 1 = 5.77 ± 0.09, C 1 = (4.7 ± 1.2) × 10 −5 mol/l and log K 2 = 4.22 ± 0.10, C 2 = (14.8 ± 1.7) × 10 −5 mol/l (95% confidence limits, 20°C). These parameters were also obtained at 25°C. K 1 and K 2 decreased with the decreasing of ⋎FA⋎ t/⋎Cu⋎ t. The labile copper fraction was determined by PSA, in a large ⋎FA⋎ t/⋎Cu⋎ t molar ratio range (89-1.6) in 0.5 mol/l sodium perchlorate medium, at −0.5 V vs. SCE and 20°C. The results were compared with the inorganic copper(II) fraction obtained by a computational simulation based on equilibrium considerations. The lowest lability (dissociation of ca. 8% of the Cu-FA complexes) was found for the highest ⋎FA⋎ t/⋎Cu⋎ t ratio, which corresponded to ⋎Cu-FA⋎/TOC = 0.06 mmol/g. The lability increased up to ca. 61% when ⋎FA⋎ t/⋎Cu⋎ t decreased down to 6 (or ⋎Cu-FA⋎/TOC = 0.8 mmol/g) and slightly decreased down to ca. 50% for lower ⋎FA⋎ t/⋎Cu⋎ t values (the lowest was 2 mmol/g). In synthetic sea water, the inert copper(II) fraction (i.e., ⋎Cu⋎ t/⋎Cu⋎ labile measured by PSA) was not very different from that found for 0.5 mol/l sodium perchlorate for identical ⋎FA⋎ t/⋎Cu⋎ t at pH 6.5. Similar results were obtained at pH 7.5. These results suggest that the PSA kinetic behaviour of FA in sea water may not be very different from that observed for the simpler medium of similar ionic strength.

Potentiometric stripping analysis of thallium in natural waters

The determination of Tl(I)_by potentiometric stripping analysis (PSA) has been studied. Effects of experimental variables such as the plating, deposition and stirring regimes, and the amount of oxidant are described. After optimization of the relevant experimental variables, an amount of 0.35 · 10 −9 mol/l Tl + was measured in river Rhine water.