Accumulation of selected metals in the fruits of medicinal plants grown in urban environment of Islamabad,Pakistan

The present study is based on the measurement of selected metals (Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Pb, Sr and Zn) in the fruits of eight medicinal plants (Carrisa opeca, Phyllanthus emblica, Solanum nigrum, Zizyphus nummularia, Zizyphus mauritiana, Physalis minima, Opuntia dillenii and Phoenix dactylifera) and relevant soil samples by atomic absorption spectrometry. Highest average concentrations of Cu (14.4 mg/kg), Cr (19.0 mg/kg), and Zn (125 mg/kg) were found in the fruits of P. minima, C. opeca and Z. nummularia, respectively, while O. dillenii showed the elevated mean levels of Cd (3.49 mg/kg), Sr (61.4 mg/kg), Mg (0.21%), Ca (6.62%) and Mn (44.6 mg/kg). However, highest average levels of Pb (41.7 mg/kg) and Co (38.4 mg/kg) were found in Z. mauritiana. Overall, most of the fruit samples showed higher contributions of Ca and Mg, followed by Fe, Zn, Co and Pb. In the case of soil samples, highest concentration was observed for Ca, followed by Fe, Mg, Mn and Sr, while lowest concentration was shown by Cd. Bioaccumulation factors exhibited significantly higher accumulation of Co (0.813–1.829) and Pb (0.060–2.350) from the soil to the fruits. Principal component analysis revealed significant anthropogenic contributions of Pb, Fe and Co in the fruit samples. Contamination factors and enrichment factors of Cd and Pb in the soil indicated very high contamination and extreme enrichment of these metals.     

Geochemical fractions and modeling adsorption of heavy metals into contaminated river sediments in Japan and Thailand determined by sequential leaching technique using ICP-MS

In order to provide information on the chemical processes in sediment fractions and their adsorption models, we investigated the contaminated sediments of the Sumida River in Tokyo, Japan and the Chao Phraya River in Bangkok, Thailand. Samples were leached through a sequential leaching technique to perform metal concentration analysis for the sediment fraction assessment and then samples were tested for the model adsorption of the highest level of sediments contaminated by heavy metals using the isotherm Langmuir and Freundlich equations. Metal (Pb, Cd, Zn, As, Cu, Ca, Fe, and Mn) concentration in the leached solutions was analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The pattern of geochemical fractions in both sediment samples showed the maxima leached levels of Cd (38.6 %), Ca (55.2%), and Mn (41.3%) in the soluble fraction; Pb (52.1%), and Zn (56.7%) in the reducible fraction; Cu (61.2%) in the oxidizable fraction; and As (47.1%) and Fe (55.9%) in the residual fraction. The total level fractions of Pb (62.6 ppm), Zn (240 ppm), As (27.2 ppm), Fe (16,636 ppm) and Mn (419 ppm) in the Chao Phraya River sediments were higher compared to those in the Sumida River, indicating the high anthropogenic effect in Bangkok. In the most contaminated sediments, the higher adsorption capacity of heavy metal concentrations was contributed by SiO_2, CaCO_3, and Al₂O₃ determined by the X-ray diffraction and organic contents. The model of adsorption of Cd fitted to the linear form of Langmuir’s equation with the correlation coefficients (r² = 0.94), b (0.467) and k (7137), whereas Pb, Cu, Cr, and Zn conformed to the model of the Freundlich equation.     

Determination of trace impurities in titanium dioxide by slurry sampling electrothermal atomic absorption spectrometry

A slurry sampling electrothermal atomic absorption spectrometry method for the determination of Al, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, Tl and Zn in powdered titanium dioxide is described. The behaviour of the titanium matrix in the atomizer and its interferences with the determination of Al, Fe, Co, Ni and Mn were studied. A tungsten carbide modified graphite tube was used to improve the signal shape and the repeatability for the determination of Fe. For all elements, except for Cd and Pb, quantification by a calibration curve established with aqueous standards was possible. No chemical modifier was used throughout in order to minimize contamination. For the contamination risk elements such as Ca, Fe, K, Mg, Na and Zn, the slurry sampling technique allows to achieve limits of detection (3σ of the blank) 5–20 times lower than the solution technique, resulting for these elements in values of 1, 3, 0.5, 0.5, 0.9 and 2 ng g⁻¹, respectively, and, generally being in the range of 0.2 ng g⁻¹ (Cd) to 10 ng g⁻¹ (Al and Tl). The results obtained by the slurry sampling technique are compared with those of other independent methods including four solution methods and neutron activation analysis.     

Simultaneous removal of copper(II), lead(II), zinc(II) and cadmium(II) from aqueous solutions by multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were used successfully for the removal of heavy metals from aqueous solution. Characterization techniques showed the carbon as nanotubes with an average diameter between 40 and 60 nm and a specific surface area of 61.5 m² g^?1. The effect of carbon nanotubes mass, contact time, metal ions concentration, solution pH, and ionic strength on the adsorption of Cu(II), Pb(II), Cd(II) and Zn(II) by MWCNTs were studied and optimized. The adsorption of the heavy metals from aqueous solution by MWCNTs was studied kinetically using different kinetic models. A pseudo-second order model and the Elovich model were found to be in good agreement with the experimental data. The mechanism of adsorption was studied by the intra-particle diffusion model, and the results showed that intra-particle diffusion was not the slowest of the rate processes that determined the overall order. This model also revealed that the interaction of the metal ions with the MWCNTs surface might have been the most significant rate process. There was a competition among the metal ions for binding of the active sites present on the MWCNTs surface with affinity in the following order: Cu(II) > Zn(II) > Pb(II) > Cd(II).     

Analytical possibilities of different X-ray fluorescence systems for determination of trace elements in aqueous samples pre-concentrated with carbon nanotubes

This study was aimed to achieve improved instrumental sensitivity and detection limits for multielement determination of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Se, Pb and Cd in liquid samples by using different X-ray fluorescence (XRF) configurations (a benchtop energy-dispersive X-ray fluorescence spectrometer, a benchtop polarised energy-dispersive X-ray fluorescence spectrometer and a wavelength-dispersive X-ray fluorescence spectrometer).The preconcentration of metals from liquid solutions consisted on a solid-phase extraction using carbon nanotubes (CNTs) as solid sorbents. After the extraction step, the aqueous sample was filtered and CNTs with the absorbed elements were collected onto a filter paper which was directly analyzed by XRF.The calculated detection limits in all cases were in the low ng mL^− 1 range. Nevertheless, results obtained indicate the benefits, in terms of sensitivity, of using polarized X-ray sources using different secondary targets in comparison to conventional XRF systems, above all if Cd determination is required.The developed methodologies, using the aforementioned equipments, have been applied for multielement determination in water samples from an industrial area of Poland.     

Synthesis and spectroscopic,magnetic and cyclic voltammetric characterization of some metal complexes of methionine: [(C5H10NO2S)2MII]; MII = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)

Some metal complexes of DL–methionine were prepared in aqueous medium and characterized by different physico-chemical methods. Methionine forms 1:2 complexes with metal, M(II). The general empirical formula of the complexes is proposed as [(C₅H₁₀NO₂S)₂M^II]; where M^II = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II). All the complexes are extremely stable in light and air and optically inactive. Magnetic susceptibility data of the complexes demonstrate that they are high spin paramagnetic complex except Zn(II), Cd(II) and Hg(II) complexes. The bonding pattern in the complexes are similar to each other as indicated by electronic absorption spectra and FTIR spectral analysis. The current potential data, peak separation (AE) and the peak current ratio (i_pa/i_pc) of the (Mn, Cu and Cd) complexes indicate that the charge transfer processes are irreversible, the systems are diffusion controlled and also adsorptive controlled. The charge transfer rate constant of metals in their complexes are less than those in their metal salts at identical experimental conditions due to the coordination of metal with methionine.     

Trace Cd,Co, and Pb elements distribution during Sulcis coal pyrolysis: GFAAS determination with slurry sampling technique

A simple and fast method based on graphite furnace atomic absorption spectrometry (GF AAS) and slurry sampling technique (SlS) was developed to determine trace Cd, Co and Pb in high-sulphur coal (Sulcis, Italy) and coal chars derived at 600, 750 and 950 °C under N₂ atmosphere for developing a clean coal for electricity production. The proposed method was then coupled to a four-step sequential chemical extraction method for assessment of metals distribution in coaled samples. The slurries were prepared by varying sample mass (1–50 mg), volume (1–3 mL) and kind of dispersing medium (1% v/v Triton X-100 and 2 N HNO₃), and sonication time (5–30 min). Pyrolysis/atomization temperatures as well carrier gas flow rate were optimised. Pd(NO₃)₂ and NH₄H₂PO₄ were employed to stabilize Cd and Pb, respectively, in the pyrolysis stage of furnace program. The use of HNO₃ as dispersing agent was found to be effective in lowering the high level of background absorption on the Cd analytical signal produced by raw coal matrix. Conversely, coal charred samples did not show significantly level of background interferences, so that Triton X-100 dispersing agent could be used for all analytes. Calibration curve against acid-matched standards was allowed for Cd, whereas the standard addition calibration was used for Co and Pb owing to chemical matrix interferences. The precision, expressed as relative standard deviation (% RSD, n = 5), was better than 5% for Cd, Co, and Pb at 1, 10, and 15 μg L^? 1 levels, respectively. The accuracy of the analytical method was checked by analyzing a BCR No. 182 steam coal certificated reference material and the results were in good agreement with certificated and informed values. The solid detection limits (3σ_blank) were as low as 0.001 Cd, 0.01 Co, and 0.01 Pb mg kg^? 1, using 30 mg sample mass and slurry concentration of 30 m v^? 1 for Cd, and 50 mg sample mass and 50 m v^? 1 slurry concentration for Co and Pb. The content of elements in Sulcis coal was found to be 0.33 Cd, 4.0 Co, and 3.8 Pb mg kg^? 1 and mostly associated to sulphates and di-sulphides as indicated by the leaching test. Under pyrolysis conditions Cd significantly volatilised (about 64%) at temperature higher than 600 °C, whereas residue chars at 950 °C are enriched in Co and Pb up to 20%. The proposed method is suitable for routine metals monitoring in coaled samples.     

Quantitative determination of trace metals in high-purity silicon carbide powder by laser ablation inductively coupled plasma mass spectrometry without binders

We have developed a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method to directly determine the concentrations of trace metals in high-purity powdery silicon carbide (SiC) samples. The sample preparation procedure is simple and rapid. The sample was formed into pellets using no binders and heated at 1000 °C for 2 h. The operation parameters for LA and ICP-MS were optimized to achieve a table signal intensity and high sensitivity. National Institute of Standards and Technology Standard Reference Materials glasses were chosen as calibration standards, with ²⁹Si chosen as the internal standard. The relative sensitivity factor obtained from the glass matrix was used to calculate the concentrations of analytes in the SiC ceramic samples. The regression correlation coefficients of the calibration curves for elements with internal standard correction ranged from 0.9981 to 0.9999, which are better than those obtained with an external standard correction method only. The relative standard deviation of the measured trace element concentrations was less than 5%. The limits of detection were 0.02, 0.08, 0.04, 0.005, 0.01, 0.02, 0.004, 0.07, and 0.006 mg kg^− 1 for B, Ti, Cr, Mn, Fe, Ni, Co, Cu, and Sr, respectively. The method was applied to analyze SiC samples with two different particle sizes. The analysis showed good agreement with the results of inductively coupled plasma optical emission spectrometry. The reliability of the proposed method was confirmed by determining the contents of B, Ti, Cr, Mn, Fe, Ni, and Cu in BAM-S003.     

Electrothermal vaporization coupled with inductively coupled plasma array–detector mass spectrometry for the multielement analysis of Al2O3 ceramic powders

An electrothermal vaporization (ETV) system useful for the analysis of solutions and slurries has been coupled with a sector-field inductively coupled plasma mass spectrometer (ICP–MS) equipped with an array detector. The ability of this instrument to record the transient signals produced for a number of analytes in ETV–ICP–MS is demonstrated. Detection limits for Mn, Fe, Co, Ni, Cu, Zn and Ga are in the range of 4–60 pg μL^− 1 for aqueous solutions and in the low μg g^− 1 range for the analysis of 10 mg mL^− 1 slurries of Al₂O₃ powders. The dynamic ranges measured for Fe, Cu and Ga spanned 3–5 orders of magnitude when the detector was operated in the low-gain mode and appear to be limited by the ETV system. Trace amounts of Fe, Cu and Ga could be directly determined in Al₂O₃ powders at the 2–270 μg g^− 1 level without the use of thermochemical reagents. The results well agree with literature values for Fe and Cu, whereas deviations of 50% at the 90 μg g^− 1 level for Ga were found.     

Studies on transport phenomena in electrothermal vaporization sample introduction applied to inductively coupled plasma for optical emission and mass spectrometry

In the present work electrothermal vaporization (ETV) was used in both inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectrometry (OES) for sample introduction of solution samples. The effect of (Pd + Mg)-nitrate modifier and CaCl₂ matrix/modifier of variable amounts were studied on ETV-ICP-MS signals of Cr, Cu, Fe, Mn and Pb and on ETV-ICP-OES signals of Ag, Cd, Co, Cu, Fe, Ga, Mn and Zn. With the use of matrix-free standard solutions the analytical curves were bent to the signal axes (as expected from earlier studies), which was observed in the 20–800 pg mass range by ICP-MS and in the 1–50 ng mass range by ICP-OES detection. The degree of curvature was, however, different with the use of single element and multi-element standards. When applying the noted chemical modifiers (aerosol carriers) in microgram amounts, linear analytical curves were found in the nearly two orders of magnitude mass ranges. Changes of the CaCl₂ matrix concentration (loaded amount of 2–10 μg Ca) resulted in less than 5% changes in MS signals of 5 elements (each below 1 ng) and OES signals of 22 analytes (each below 15 ng). Exceptions were Pb (ICP-MS) and Cd (ICP-OES), where the sensitivity increase by Pd + Mg modifier was much larger compared to other elements studied. The general conclusions suggest that quantitative analysis with the use of ETV sample introduction requires matrix matching or matrix replacement by appropriate chemical modifier to the specific concentration ranges of analytes. This is a similar requirement to that claimed also by the most commonly used pneumatic nebulization of solutions, if samples with high matrix concentration are concerned.     

Solid Phase Extraction of Trace Metals in Seawater Using Morpholine Dithiocarbamate‐Loaded Amberlite XAD‐4 and Determination by ICP‐AES

Abstract

Application of morpholine dithiocarbamate (MDTC) coated Amberlite XAD‐4, for preconcentration of Cu(II), Cd(II), Zn(II), Pb(II), Ni(II) and Mn(II) by solid phase extraction and determination by inductively coupled plasma (ICP) atomic emission spectrometry (AES) was studied. The optimum pH values for quantitative sorption of Cu(II), Cd(II), Zn(II), Pb(II), Ni(II), and Mn(II) were 6.5–8.0, 7.0–8.5, 6.0–8.5, 6.5–8.5, 7.5–9.0, and 8.0–8.5, respectively. The metals were desorbed with 2 mol L^?1. The t_1/2 values for sorption of metal ions were 2.6, 2.9, 2.5, 2.6, 3.0, and 3.8 min respectively for Cu(II), Cd(II), Zn(II), Pb(II), Ni(II) and Mn(II). The effect of diverse ions on the determination of the previously named metals was studied. Simultaneous enrichment of the six metals was accomplished, and the method was applied for use in the determination of trace metal ions in seawater samples.     

Thermodynamic and isotherm studies of the biosorption of Cu(II), Pb(II), and Zn(II) by leaves of saltbush (Atriplex canescens)

The Freundlich and Langmuir isotherms were used to describe the biosorption of Cu(II), Pb(II), and Zn(II) onto the saltbush leaves biomass at 297 K and pH 5.0. The correlation coefficients (R²) obtained from the Freundlich model were 0.9798, 0.9575, and 0.9963 for Cu, Pb, and Zn, respectively, while for the Langmuir model the R² values for the same metals were 0.0001, 0.1380, and 0.0088, respectively. This suggests that saltbush leaves biomass sorbed the three metals following the Freundlich model (R² > 0.9575). The K_F values obtained from the Freundlich model (175.5 · 10⁻², 10.5 · 10⁻², and 6.32 · 10⁻² mol · g⁻¹ for Pb, Zn, and Cu, respectively), suggest that the metal binding affinity was in the order Pb > Zn > Cu. The experimental values of the maximal adsorption capacities of saltbush leaves biomass were 0.13 · 10⁻², 0.05 · 10⁻², and 0.107 · 10⁻² mol · g⁻¹ for Pb, Zn, and Cu, respectively. The negative ΔG^∘ values for Pb and the positive values for Cu and Zn indicate that the Pb biosorption by saltbush biomass was a spontaneous process.     

Trace metal accumulation in tissues of sole (Solea senegalensis) and the relationships with the abiotic environment

The distribution patterns and the organ-specific accumulation trends of 10 trace metals (iron, manganese, zinc, copper, chromium, nickel, cobalt, lead, cadmium and silver) and 4 major elements (sodium, potassium, calcium and magnesium) in 10 different tissues (heart, muscle, kidney, stomach, intestine, liver, gill, gonads, white skin and dark skin) of a benthic fish species (Solea senegalensis) from a densely populated coastal area affected by anthropogenic activities, the Bay of Cadiz (SW Spain), have been investigated. High variability of metal concentrations among tissues were found for Ca, Fe, Zn, Cu, Pb and Ag. Factor analysis was applied to study this variability. Five principal components were found explaining the 92.95% of the total variance and similarities in behavioural patterns of bioaccumulation were described. They associated Mg, Cr, Ni and Mn to intestine and stomach tissues (PC1), Ag, Cu and Cd to liver (PC2), Zn, K and Co to gonads (PC3), Na, Fe and Pb to gill, heart and kidney tissues (PC4) and Ca, Pb and Mn to gill and dark skin (PC5). The metallic concentration in the sediment and water was also studied. The pollution in this area was found moderate with outstanding values of Zn, Cu and Pb (average values of 139, 50.4 and 75.6?mg?kg^?1, respectively) in sediment and dissolved Cu (average value of 2.5?µg?L^?1). Metal bioconcentration trends followed the order Zn?>?Cu?>?Cd?>?Pb for dissolved metals in seawater, Cu?>?Zn?>?Cd?>?Pb?≈?Mn?>?Fe?≈?Ni?≈?Co for metals associated to particulate matter and Zn?≈?Cu?>?Cd?>?Mn?>?Co?≈?Fe?>?Ni?≈?Pb?>?Cr for metals in the sediment. Higher values were found for copper in liver, zinc in gonads and lead in gill, showing the relationship between biotic and abiotic environment. In addition, Cd bioconcentration factors were found high in liver and gill showing the sensitivity of sole to this metal even at low concentrations.     

Heavy elements concentrations,physiochemical characteristics and natural radionuclides levels along the Saudi coastline of the Gulf of Aqaba

This paper represents the first work on the concentrations of heavy elements, physiochemical characteristics and activity levels of the naturally occurring radionuclides in the Saudi Arabian coastline of the Gulf of Aqaba. Concentrations of 19 heavy elements were measured, namely: Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, V and Zn. The radioactivity levels of ²³⁸U, ²³²Th and ⁴⁰K were estimated to be: 17 ± 1.7, 22.5 ± 3.7 and 649.6 ± 64.2 Bq kg^?1, respectively. The measurements were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). In addition, physiochemical characteristics of 19 sediment samples (i.e., saturation percentage, pH, electrical conductivity, organic matter, cation exchange capacity and content of clay, silt and sand) have been determined. Indications for high correlation between most heavy elements are found. The correlation between heavy elements and the radionuclides ²³⁸U, ²³²Th and ⁴⁰K was generally significant.     

Determination of major and trace elements in six herbal drugs for relieving heat and toxicity by ICP-AES with microwave digestion

ObjectiveTo establish a method to simultaneously determine major and trace element contents of Na, K, Cu, Fe, Zn, Mn, Ca, Mg, Cr, Ni, Pb, Se, As and Cd in six herbal drugs.MethodsMicrowave digestion procedure was applied under optimized conditions for digesting medicinal herbs. Concentrations of elements were determined by ICP-AES.ResultsThe results indicated that the herbal drugs were abundant in major and trace element contents which are healthy for human body. After optimizing the microwave digestion technology, the recovery of the element was 96.79–103.47% and the RSD < 5.0%.ConclusionICP-AES combined with the microwave digestion technology has a lot of merits in terms of saving time and effort, reducing environmental pollution, fast and accurate determination of results in determining major and trace elements.     

Micro-electrodeposition in the presence of ionic liquid for the preconcentration of trace amounts of Fe,Co, Ni and Zn from aqueous samples

The paper presents the preconcentration of trace elements via electrodeposition onto a (micro)aluminum cathode in the presence of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] as a supporting electrolyte. The advantages of the proposed method include very simple instrumentation for the preconcentration of trace elements and low-cost reagents. The experiment showed that the use of ionic liquid in the electrodeposition process significantly improves sensitivity, recovery and detection limits for the determination of trace amounts of iron, cobalt, nickel and zinc. The preconcentrated metals were determined using X-ray fluorescence spectrometry. The optimum parameters for electrodeposition such as pH, the volume of the analyzed solution, the voltage and the deposition time were studied. Under the optimized conditions, the detection limits were 5, 2, 3 and 6 μg L^− 1 for iron, cobalt, nickel and zinc, respectively. The precision and recovery of the method were in the range of 3–5.5%, and 92–103%, respectively. The calibration was performed using aqueous standards of Fe(III), Co(II), Ni(II) and Zn(II) in the range 0.01–0.25 mg L^− 1. The method was applied successfully in water analysis.     

Determination of lead(II) in fly ash leachate using a newly developed simple spectrophotometric method

A new simple method for the spectrophotometric determination of Pb(II) in fly ash leachates was developed. These leachates tend to contain a large amount of Ca(II) and Zn(II); this interferes with spectrophotometric determination of Pb(II) when conventional colorimetric agents are used. A copolymer consisting of protoporphyrin IX disodium salt and acrylamide was synthesized as a colorimetric agent. A measuring reagent containing ethylenediamine-N,N′-dipropionic acid (EDDP) as a masking agent for Zn(II) and an appropriate amount of Ca(II) together with the copolymer was applied to determine Pb(II). The temporal change in the absorption spectrum of the measuring reagent was acquired with a newly developed portable spectrophotometer for this method. The composition of EDDP and Ca(II) in the measuring reagent was optimized to measure leachates contaminated with Ca(II) and Zn(II). The detection limit and relative standard deviation of Pb(II) measured using the optimized method were 0.05 mg L^?1 and 2.3%, respectively. The tolerance limits for Ca(II) and Zn(II) contaminants, where errors of less than 10% were allowed at a concentration of 0.5 mg L^?1 Pb(II), were 4000 and 4 mg L^?1, respectively. The determination of Pb(II) in various samples of actual leachates from incinerator fly ash was examined with this method. The obtained values correlated well with those obtained by flame atomic absorption spectroscopy.     

Counter-current chromatography for oil analysis: Retention features and kinetic effects

Application of counter-current chromatography (CCC) for oil analysis has been suggested for the first time. CCC looks very promising as a tool for pre-concentration and isolation of trace elements from oil. Features of stationary phase retention of two-phase liquid systems (oil or oil products–aqueous nitric acid solutions) in CCC have been investigated. The influence of physicochemical properties of crude oil and oil products used as a mobile phase on the volume of stationary phase (acidic aqueous solutions) retained in CCC was studied. Chromatographic behavior of several oil samples was studied. It has been shown that physicochemical properties of test oil influence its chromatographic behavior. Optimal values of density and viscosity (ρ < 0.85 g/cm³, n < 7 cSt) of crude oil and oil products that could be analyzed using CCC were estimated. The influence of the column rotational speed and flow rate of mobile phase on the stationary phase retention was also investigated. It is known that kinetic aspects (mass transfer of elements between phases) can play a very important role in selecting an optimal composition of stationary phase for the pre-concentration of elements from oil. The influence of nitric acid concentration in the stationary phase on mass transfer was studied. Kinetic characteristic for trace element recovery has been investigated for the optimization of pre-concentration conditions of trace elements from crude oil and oil products. The extraction recoveries of Zn, Mn, Fe, Ni, V, Cu, Cd, Pb and Ba by CCC in dynamic mode are in the range of 75–95% while they are lower than 35% under batch conditions.     

Functionalised resin-modified carbon paste sensor for the voltammetric determination of Pb(II) within a wide concentration range

A carbon paste electrode bulk-modified with a functionalised macroporous resin is described as a voltammetric sensor for Pb(II) ions. The commercially available product, QuadraPure™TU, admixed into the paste at a ratio of 30% (v/v), contains thiourea residues that act as a highly effective functional group for chelating Pb(II). By combining with square-wave anodic voltammetry and “open-circuit” accumulation, the stripping peak of lead in 0.1 M acetate buffer could be calibrated over a wide concentration range of 0.005–5 mg l⁻¹ Pb, with possible extension up to 25 mg l⁻¹, when the signal of interest was not seriously affected by the presence of other common metals. Applicability of the sensor in practical analysis has been tested on selected water samples or a certified reference material and the respective results agreed well to those obtained by ICP-MS and to the content declared.     

Spatial distribution and contamination assessment of heavy metals in urban road dusts from Urumqi, NW China

This study reports the spatial distribution pattern and degree of heavy metal pollution (Cd, Cr, Cu, Ni, Pb, Mn, Be, Co, Zn and U) in 169 urban road dust samples from urban area of Urumqi city. The spatial distribution pattern shows that Cu, Pb, Cr and Zn have similar patterns of spatial distribution. Their hot-spot areas were mainly associated with main roads where high traffic density was identified. Ni and Mn show similar spatial distributions coinciding with the industrial areas, while the spatial distribution patterns of Co and U show hot-spot areas were mainly located in the sides of the urban area where the road dust was significantly influenced by natural soils. The spatial distributions of Be and Cd were very different from other metals. The geo-accumulation index suggests that road dust in Urumqi city was uncontaminated to moderately contaminated with Cd, Cu, Ni, Pb, Mn, Be, Zn and U. The integrated pollution index shows IPIs of all road dust samples were higher than 1, suggesting that the road dust quality of Urumqi city has clearly been polluted by anthropogenic emission of heavy metals. Moreover, the spatial distribution pattern of IPIs also shows several distribution trends in the studied region.