Differential Pulse Anodic Stripping Voltametry Research Articles

Cost effective and shape controlled approach to synthesize hierarchically assembled NiO nanoflakes for the removal of toxic heavy metal ions in aqueous solution

Hierarchical mesoporous NiO nanoflakes (NiOs) have been synthesized in high yield via a simple, economical and environmentally friendly hydrothermal route. The as-prepared NiOs were characterized by powder X-ray diffraction (PXRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction patterns (SAED), X-ray energy dispersive spectroscopy (EDS) and nitrogen adsorption–desorption techniques (Brunauer–Emmett–Teller, BET). Adsorption of heavy metal ions onto the as-prepared sample from aqueous solutions was investigated using differential pulse anodic stripping voltametry (DPASV) technique and discussed. The product possesses a BET surface area of 69.27 m2 g−1. It is found that NiOs exhibited the excellent performance for the removal of Hg(II), Pb(II) and Cd(II) from aqueous solution. The equilibrium adsorption data of Hg(II), Pb(II) and Cd(II) on the as-prepared NiOs were analyzed by Langmuir and Freundlich models, suggesting that the Langmuir model provides the better correlation of the experimental data. The adsorption capacities for removal of Hg(II), Pb(II) and Cd(II) were determined using the Langmuir equation and found to be 1324 .5, 1428 .9 and 1428 .5 mg g−1, respectively. Adsorption kinetics of all the metal ions followed pseudo second-order model. Moreover, NiOs can be recycled by simple acid treatment, which could retain the high removal efficiency in three successive cycles. This study suggests that nanoflakes could be explored as a new adsorbent with high efficiency and recyclability for removing heavy metal ions from aqueous solution.

Zinc (Zn) Analysis in Milk by Microwave Oven Digestion and Differential Pulse Anodic Stripping Voltametry (DPASV) Technique

Milk is very important component of human diet. The presence of over limit of heavy metal in milk may create significant health problems. In the present study, the direct determination of Zinc (Zn) heavy metal in milk samples of different brands was carried out by differential pulse anodic stripping Voltammetric technique at Hanging Mercury Drop Electrode (HMDE). Milk samples were processed by microwave oven digestion using HP/VHP Vessels and TFM Liners and nitric acid (HNO3 ).Determination of Zn was made in acetate buffer (pH 4.6) with a sweep rate (scan rate) of 59.5 mV/s and pulse amplitude 50mV by HMDE by standard addition method. The solution was stirred during pre-electrolysis at -1150mV (vs. Ag/AgCl) for 90 seconds and the potential was scanned from -1150V to +100V (vs. Ag/AgCl). The zinc ions were deposited by reduction at -1150 mV on HMDE. The stripping current arising from the oxidation of metal was correlated with the concentration the metal in the sample. .As a result the minimum level of Zn observed in the milk sample of different brands was determined as 2.28 mgL−1 .

Effect of soil properties and sample preparation on extractable and soluble Pb and Cd fractions in soils

The effect of soil extraction procedures and/or sample pretreatment (drying, freezing of the soil sample) on the extractability of cadmium and lead was tested in a model experiment, with an employment of optical emission and atomic ab- sorption spectrometry methods. In the first part, 6 extraction procedures were compared: 2 mol l-1 HNO3, 0.43 mol l-1 CH3COOH, 0.05 mol l-1 EDTA, Mehlich III extraction procedure (0.2 mol l-1 CH3COOH + 0.25 mol l-1 NH4NO3 + 0.013 mol.l-1 HNO3 + 0.015 mol.l-1 NH4F + 0.001 mol.l-1 EDTA), 0.01 mol.l-1 CaCl2, and deionised water. Addi-tionally, two methods of soil solution sampling were compared, and the centrifugation of satu-rated soil and the use of suction cups and dif-ferential pulse anodic stripping voltametry was applied to assess free and complexed metals portions. The results showed that different soil sample extraction methods and/or sample pre-treatments including soil solution sampling can lead to different absolute values of mobile cadmium and lead content in soils. However, the interpretation of the data can lead to similar conclusions as are apparent from the compari- son of the soil solution sampling methods where fairly good correlation was observed (for Cd r = 0.76, and for Pb r = 0.74). The ambiguous results were reported for voltammetric determinations of free and complex portions of Cd and Pb where a different behavior was observed for water extracts of soil and soil solution obtained using suction cups. Moreover, a changing extent of lead complexation was determined with prolonged storage of the samples. The results confirmed that soil and/or soil solution sampling under immediate soil conditions and limitations of pre-extraction operations are necessary.

Contribution to biomonitoring of some trace metals by deciduous tree leaves in urban areas

Leaves of the deciduous tree species, horse chestnut (Aesculus hippocastanum L.) and Turkish hazel (Corylus colurna L.) were used as accumulative biomonitors of trace metal pollution in the urban area of Belgrade. Using differential pulse anodic stripping voltametry, trace metal concentrations (Pb, Cu, Zn, Cd) were determined at the single leaf level (ten leaves per species, per month), during two successive years with markedly different atmospheric level of trace metals. Increased trace metal concentrations in the leaves of A. hippocastanum reflected elevated atmospheric trace metal pollution, whereas C. colurna L. did not respond accordingly. The contents of Pb and Zn in soil over the same period also followed this trend. Anatomical analyses, in young as well as in old leaves of both species, indicated typical foliar injuries of plants exposed to stressful air conditions. Water relations that correspond to leaf age may have contributed to the considerable trace metal accumulation in leaves.

Elucidation of interference mechanisms caused by iron on stibine electrochemical generation by differential pulse anodic stripping voltametry. A case study

The interference effect caused by the presence of iron – both (II) and (III) oxidation states – on the electrochemical generation of SbH 3 has been characterized. Interference from Fe(III) was more severe than for Fe(II). Total signal suppression was obtained for a Fe(III) : Sb(III) concentration ratio of 5 : 1, whereas a 40% suppression was obtained for Fe(II). A mechanism is proposed based on the results obtained by differential pulse anodic stripping voltametry. The standard conditions used for the hydride electrochemical generation were simulated in the differential pulse anodic stripping voltametry measurements in order to achieve valid conclusions. The reduction of Fe(II) onto the cathode surface prevents the formation of stibine avoiding the recombination of Sb 0 with the hydrogen atoms adsorbed on the surface. The mechanism by which the Fe(III) interferes on the stibine formation is related to the co-deposition of the iron and antimony that also avoid the further recombination of the Sb 0. The formation of a specie of stoichiometry not determined (probably 1 : 1) on the cathode surface may justify the larger interference effect observed for the Fe(III).

Environmental factors determining the trace-level sorption of silver and thallium to soils

Silver (Ag) and thallium (Tl) are nonessential elements that can be highly toxic to a number of biota even when present in the environment at trace levels. In spite of that, the literature on the chemistry and fate of Ag and Tl in soils is extremely scanty. In that context, the key objective of this research was to compare the sorption characteristics of trace amounts of Ag and Tl on a range of soils and minerals. A second objective was to determine the extent to which the composition and surface chemistry of the sorbents, as well as other environmental factors (simulated acid rain application and the presence of competing ions like K + and NH 4 +) influence the sorption and lability of Ag and Tl. To this end, short-term and long-term sorption isotherms were generated under batch conditions for trace levels of Ag and Tl onto three illite-rich mineral soils from central New York (silt loam and fine sandy loam), a peaty-muck soil drained for agricultural use, and soil minerals (ferrihydrite and birnessite). Silver sorbed more strongly than thallium to all the soils. The peaty-muck soil sorbed Ag more strongly than the mineral soils, confirming that silver sorption to soils is dominated by soil organic matter either through exchange or complexation. The organic matter-rich soil's retention of Tl, however, was similar to that of the sandy soil. Amounts of Ag and Tl sorbed to the mineral soils increased after a 1-year incubation period. Whereas Ag sorption to the peaty-muck soil also increased with time, Tl sorption was unaffected. Short batch studies indicated that high amounts of Tl sorb to birnessite (30% by mass). However, subsequent X-ray diffraction (XRD) analysis of the solid did not detect the presence of any Tl 3+ as Tl 2O 3 on the MnO 4. In contrast, Tl(I) was relatively poorly sorbed on noncrystalline ferrihydrite at pH 5.1 (1.5% by mass). Thus, Mn oxides may play a role in Tl retention by soils; whereas, contrary to previous reports, iron oxides do not effectively sorb Tl. Acid rain and addition of potassium (K +) and ammonium (NH 4 +) as competing ions had no long-term effect on Ag or Tl sorption. Thallium remaining in the all the batch sorption solutions, as determined by flame atomic absorption spectroscopy (FAAS) and differential pulse anodic stripping voltametry (DPASV), was completely labile, which may have important environmental consequences.

Cadmium, copper and lead contamination of the seawater column on the Prestige shipwreck (NE Atlantic Ocean)

As a result of the Prestige tanker sinkage on 19 November 2002, vast amounts of heavy fuel were dump from the shipwreck lying on the bottom to the surface of the NE Atlantic Ocean. The heavy metal contamination of the water column was studied from 4–8 December 2002 taking advantage of an opportunistic cruise onboard the R/V Atalante. Clean laboratory procedures were used in order to analyse 32 water samples and two heavy fuel samples (cargo tanker and surface seawater of the shipwreck area) by means of differential pulse anodic stripping voltametry and electrothermal atomic absorption spectrometry. Around 25 kg of Cd, 170 kg of Cu and 10 kg of Pb were released into the ocean water over seventy days of which 2% (Cd), 23% (Cu) and 71% (Pb) remain in the floating fuel patches on the sea surface. In the Prestige shipwreck area, where the seawater was free of oil patches, copper (2.8–8.5 nM) and lead (0.10–0.78 nM) contamination was only observed in the uppermost ocean layer, from 100 m depth for copper and the top ocean for lead. On the contrary, the cadmium levels (0.02–0.41 nM) observed were within typical or uncontaminated values.

Cadmium, copper and lead contamination of the seawater column on the Prestige shipwreck (NE Atlantic Ocean)

As a result of the Prestige tanker sinkage on 19 November 2002, vast amounts of heavy fuel were dump from the shipwreck lying on the bottom to the surface of the NE Atlantic Ocean. The heavy metal contamination of the water column was studied from 4–8 December 2002 taking advantage of an opportunistic cruise onboard the R/V Atalante . Clean laboratory procedures were used in order to analyse 32 water samples and two heavy fuel samples (cargo tanker and surface seawater of the shipwreck area) by means of differential pulse anodic stripping voltametry and electrothermal atomic absorption spectrometry. Around 25 kg of Cd, 170 kg of Cu and 10 kg of Pb were released into the ocean water over seventy days of which 2% (Cd), 23% (Cu) and 71% (Pb) remain in the floating fuel patches on the sea surface. In the Prestige shipwreck area, where the seawater was free of oil patches, copper (2.8–8.5 nM) and lead (0.10–0.78 nM) contamination was only observed in the uppermost ocean layer, from 100 m depth for copper and the top ocean for lead. On the contrary, the cadmium levels (0.02–0.41 nM) observed were within typical or uncontaminated values.

The distributions of colloidal and dissolved organic carbon, major elements, and trace elements in small tropical catchments

In tropical surface waters, ultrafiltration, differential pulse anodic stripping voltametry, and atomic absorption spectrometry were used to determine the distribution and association of major and trace elements with different size fractions of dissolved organic carbon (DOC < 0.45 μm). DOC is mainly concentrated in the low molecular size ranges (<20 kD). However, in podzolization areas, an important part of the DOC is found in the higher molecular weight fractions (20 kD < DOC < 100 kD). The higher molecular weight fractions have a higher site density. Complexation capacities are in the range of 1–11 μM in bulk solution. In podzolization areas the higher molecular weight fractions control the speciation of Ca, Mg, and Fe. In the other tropical environments major elements are present as free ions and the low molecular weight fraction of DOC controls the speciation of trace metals (Cu).

Polarographic determination of metallic impurities on lapped silicon wafers

The method is based on the anodic oxidation of silicon layers in a 0.05 M KNO 3-10% H 2O-ethylene glycol electrolyte. The silicon oxide is completely dissolved with 0.1 M hydrofluoric acid, and then the appropriate supporting electrolyte is added. For copper, cadmium, and lead determinations, a 0.1 M citric acid-1 M nitric acid supporting electrolyte is used and differential pulse anodic stripping voltametry provides a detection limit of 0.5 ng ml −1 with a precision of ±5% (at 5 ng ml −1). For iron determination, a 0.1 M triethanolamine hydrochloride-0.1 M potassium bromate-0.1 M sodium hydroxide supporting electrolyte is used and differential pulse polarography provides a detection limit of 2 ng nm −1 with a precision of ±2% (at 5 ng ml −1). The results were confirmed by furnace atomic absorption spectrophotometry (FuAAS) by using the same oxide removal solution. FuAAS provides a detection limit of 1 ng ml −1 with a precision of ±10% (at 5 ng ml −1).

Cadmium in the Rhône river

The distribution of cadmium in the Rhône river was studied using differential pulse anodic stripping voltametry with a static mercury drop electrode. For 11 potentially contaminated river stations, the Cd in true solution averaged 39 ± 23 ng kg −1, adsorbed on suspended matter was 19 ± 22 ng kg −1 (liquid phase) and suspended matter content was 2.4 ± 1.5 mg kg −1 (solid phase), equivalent to 40 ± 24, 22 ± 24 and 38 ± 31%, respectively, of the total carried under these conditions. For sediments the mean Cd content was 0.9 ± 0.6 mg kg −1. The water values are low by world standards, even though sampling was biased towards sites potentially contaminated. This could be partially due to the unusual water pH of 7.8–8.5.

Incidence de la complexation sur la toxicite du cadmium et du cuivre vis a vis de daphnia magna

Abstract Differential pulse anodic stripping voltametry and equilibrium computation were used to determine the levels of copper and cadmium, in free ionic state and in complexed species, under the effect of EDTA and HK2PO4. A variation of short term toxicity between the two chemical species was observed on the daphnia. The results of this study lead to conclusions on the stoechiometry and stability of these complexes, and on the determination of the toxic chemical species.

Enrichissement des sediments marins en cuivre par l'intermediaire des substances humiques enrichment of marine sediments with copper transported by humic substances

Abstract A commercial product of humic acids was used to study the complexation of Cu2+ by humic substances. The precipitation of the same substances by the major inorganic salts of sea water was examined. The conditional formation constant of these complexes (K) was determined by complexometric titrations followed by a differential pulse anodic stripping voltametry procedure: the measurements of the anodic current during the titration gave a value of log K = 7. Among sea water ions, Ca2+ was the most efficient agent of precipitation (70 % of removal). Calcium ions did not displace the Cu2+ions from the humic‐copper complex during the precipitation. Consequently a significant accumulation of copper via humic substances mediation should be expected in the marine sediments.

Temperature-controlled electrothermal atomization-atomic absorption spectrometry using a pyrometric feedback system in conjunction with a background monitoring device

The construction of a temperature-controlled feedback system for electrothermal atomization-atomic absorption spectrometry (ETA-AAS) using an optical pyrometer applied to the atomization stage is described. The system was used in conjunction with a fast-response background monitoring device. The heating rate of the furnace amounted to 1400° s −1 with a reproducibility better than 1%. The precision of the temperature control at a steady state temperature of 2000°C was 0.1%. The analytical improvements offered by the present system have been demonstrated by the determination of cadmium and lead in blood and finally by the determination of lead in serum. Both the sensitivity and the precision of the method have been improved. The accuracy of the method was checked by determining the lead content for a number of scrum samples both by ETA-AAS and differential pulse anodic stripping voltametry (DPASV) and proved to be satisfactory.

Copper bioavailability to marine bivalves and shrimp: Relationship to cupric ion activity

Studies were performed to determine the effects of dissolved substances present in natural seawater and sediment on the bioavailability of added Cu +2. Whole clams Macoma inquinata and shrimp, Pandalus danae, were exposed to four concentrations of Cu in a flow-through seawater system. Bioaccumulation of Cu was reduced in shrimp, Pandalus danae, clams, M. inquinata, and excised clam gills, Protothaca staminea, exposed to an aged, compared with an unaged, Cu-seawater solution. This is thought to be due to slow complexation of the Cu by dissolved substances present in natural seawater. In a static system, with added sediment, more than 50% of the added Cu +2 became bound to the organic fraction of the sediment and was unavailable to suspension feeding clams, Protothaca staminea. In contrast, deposit feeding clams, Macoma inquinata, placed in the sediment approximately doubled in Cu body burden within two months. Complexed Cu appears to be less bioavailable than ionic Cu and hence measurements of ionic and weakly complexed Cu by differential pulse anodic stripping voltametry provide a better prediction of bioavailable Cu than conventional measurements of total Cu-seawater concentrations.

Distribution of some heavy metals in the Gulf of Fos

Measurements of copper, lead, cadmium and zinc were determined using the differential pulse anodic stripping voltametry technique in a marine industrialized area, the Gulf of Fos, near Marseilles. Results show an important contamination of the whole area, with particularly high values near the coast. Comparing our results with those of the literature, we see that the Gulf of Fos is probably one of the most polluted areas in Europe.