Selective extraction of blood plasma exchangeable copper for isotope studies of dietary copper absorption

Measuring mineral absorption by fecal monitoring is labor-intensive and relies on good volunteer compliance. Blood indicators of absorption could be advantageous and we have developed a method for selective extraction-of recently absorbed (exchangeable) copper based on dialysis of plasma with histidine and subsequent copper extraction using Chelex resin. The potential for measuring copper absorption by transient enrichment of exchangeable copper with the stable isotope 65Cu from an ingested tracer, was also investigated. This method was compared with that of the fecal monitoring technique in a human volunteer, who consumed a 6 mg dose of 65Cu with inhibitors of copper absorption. Holmium was used as a non-absorbable rare-earth marker of unabsorbed tracer excretion, allowing estimation of re-secreted 65Cu (44 microg d(-1)), and hence calculation of true tracer absorption, which was only 10.8%. Monitoring plasma tracer kinetics showed potential for estimation of copper absorption without the need for fecal copper analysis.     

Determination of ultrafiltrable and exchangeable copper in plasma: stability and reference values in healthy subjects

The knowledge of copper (Cu) distribution in blood contributes to a better understanding of copper metabolism and to a better approach and follow up of related diseases such as Wilson’s disease (WD). Many tests can be used to investigate patients who may have WD but they show many drawbacks and do not allow real patient monitoring. Knowing that the Cu overload can result from the free and easily exchangeable form of copper in plasma, a two-step method (ultrafiltration–determination by ETAAS) was carried out to determine these two fractions. The ultrafiltration procedure and the instrumental determination showed good repeatability, and a very low limit of detection was obtained (0.7 nmol/L). In vitro stability of both ultrafiltrable copper (CuUF) and exchangeable copper (CuEXC) was studied. Plasma was ultrafiltered in 44 presumably healthy subjects to determine CuUF and CuEXC and to set reference values ranges. The method was applied on a few patients showing good correlation between both parameters and the clinical and biological features of the patients. Figure Ultrafiltrable fraction of plasma copper is very instable in vitro. A 50% loss occurs within 6 hours after blood sampling     

Application of a Sequential Extraction Procedure to Calcareous Soil Samples: Preliminary Studies

Abstract

The localization of trace metals in soils is usually performed by sequential extraction procedures. Our purpose was to study the fractioning of copper in calcareous soils, in order to predict its mobility, using the extraction procedure proposed by Tessier et al. This preliminary study is devoted to the improvements of this method applied to calcareous soil samples.

First, it was necessary to assess the experimental conditions allowing the complete solubilisation of the different compartments involved in the extraction procedure with their appropriate reagent (acetic acid-sodium acetate and carbonates, iron hydroxide and hydroxylamine, organic matter and hydrogen peroxide, fluorhydric-perchloric acid and residual fraction). The complete solubilisation of each compartment was tested by measuring the residual phase.

Secondly, it was necessary to study the analytical protocol for the determination of copper with electrothermal atomic absorption; an improvement of this determination was particularly necessary for the reagent used for the exchangeable fraction (sodium acetate at pH = 8.5).

According to the experimental results, the quality (repeatability, concordance of the sum of fractions with the total content of copper determined with independent measurement) of the proposed protocol seems to be quite good.

Some results of the fractioning of copper in calcareous soil samples are given; these samples are characterised by a high value of copper in the residual fraction corresponding to a poor availability of this element.     

Speciation of copper and zinc in natural freshwater: comparison of voltammetric measurements, diffusive gradients in thin films (DGT) and chemical equilibrium models

In situ measurements of copper and zinc using diffusive gradients in thin films (DGT) in two distinct natural water systems were compared to metal speciation assessed by competitive ligand exchange (CLE) and voltammetric measurements. In a dynamic river system, where dissolved metal concentrations vary significantly over short-time periods, DGT technique provided averaged values of the metal concentrations over time. In microcosms, at different total dissolved concentrations of copper and zinc, DGT technique measured a similar fraction as measurements of labile metal performed by voltammetry. The proportion of DGT and voltammetric-labile zinc to dissolved zinc was 61±4% and, respectively, 76±9%. DGT technique was measuring 81±8% of exchangeable copper (by exchange with catechol). These two fractions were similarly influenced by the addition of NTA. In the absence of NTA, copper measured by DGT represented 34±4% of dissolved copper whereas in the presence of NTA, this proportion raised to 57±2%. These measurements were compared to calculations performed with speciation programs using several models for the complexation by humic and fulvic substances, namely Model VI (WHAM), NICA-Donnan and SHM. The predicted speciation by these three models was similar. The prediction of free zinc ion and labile zinc concentrations were in agreement with experimental data. Calculated concentrations of free copper ion were overestimated because these models are not considering strong specific copper-binding ligands probably present in natural water.     

Differenzierung der bindungsformen von kupferspuren in pflanzlichen lebensmitteln mittels ionenaustausch an cellulose-materialien und gel-filtration

(Differentiation of the chemical forms of trace amounts of copper in peas and soy meal by means of ion-exchange on cellulose materials and molecular exclusion chromatography.)Studies on the binding forms of the water-soluble copper contents of peas and soy meal in the ppm region are reported. These foodstuffs contain quite different organic substances. For peas, the amount of copper exchangeable on DEAE-Cellulose increases strongly between pH 7 and 7.5 (amphoteric substances); with soy meal, no such pH dependence is observed. Molecular exclusion chromatography indicates that the amphoteric copper compounds consist entirely of high-molecular-weight substances. The copper compounds that are not exchangeable on DEAE-Cellulose at pH 8.6, contain about 50% high-molecular-weight substances and about 25% low-molecular-weight substances. The trace amounts of copper at the microgram-level were determined spectrophotometrically by means of the selective reagent, lead diethyldithiocarbamate, after extraction.     

Aflatoxin B(1) adsorption by natural and copper modified montmorillonite

Adsorption of aflatoxin B(1) (AFB1) by natural montmorillonite (MONT) and montmorillonite modified with copper ions (Cu-MONT) was investigated. Both MONTs were characterized using the X-ray powder diffraction (XRPD) analysis, thermal analysis (DTA/TGA) and scanning electron miscroscopy/electron dispersive spectroscopy (SEM/EDS). The results of XRPD and SEM/EDS analyses of Cu-MONT suggested partial ion exchange of native inorganic cations in MONT with copper occurred. Investigation of AFB1 adsorption by MONT and Cu-MONT, at pH 3, 7 or 9, showed that adsorption of this toxin by both MONTs was high (over 93%). Since AFB1 is nonionizable, no differences in AFB1 adsorption by both MONTs, at different pHs, were observed, as expected. Futhermore, it was determined that adsorption of AFB1 by both MONTs followed a non-linear (Langmuir) type of isotherm, at pH 3. The calculated maximum adsorbed amounts of AFB1 by MONT (40.982mg/g) and Cu-MONT (66.225mg/g), derived from Langmuir plots of isotherms, indicate that Cu-MONT was much effective in adsorbing AFB1. Since, the main cation in an exchangeable position in MONT is calcium, and in Cu-MONT both calcium and copper, the fact that ion exchange of inorganic cations in MONT with copper increases adsorption of AFB1 suggests that additional interactions between AFB1 and copper ions in Cu-MONT caused greater adsorption.     

Fractionation and speciation analysis of heavy metals in the Azov Sea bottom sediments

The fractionation and speciation analysis of heavy metals in bottom sediment samples from the Azov Sea were performed. Seven-step sequential extraction was used to extract element species differing in physicochemical mobility and biological availability. Special attention was paid to the study of ecologically valuable mobile fractions: exchangeable, acid-soluble, readily reducible, and readily oxidizable ones. It was shown that the total concentration of mobile copper, zinc, and lead species isolated in four extraction steps was higher than the MPCs for mobile species extractable with an ammonium acetate buffer solution (1.1–3.3 PMC), which points to the technogenic contamination of bottom sediments and their potential hazard to hydrobionts. For finely dispersed silt samples taken near the Kerch Strait, elevated concentrations of zinc and copper (up to 10 and 5 mg/kg, respectively) were found in the most mobile exchangeable fraction directly available to living organisms, which indicates the presence of an active contamination source in this water area. The binding of metals to mineral phases in samples of different lithological types was studied.     

Spectroscopic and density functional studies of the red copper site in nitrosocyanin: role of the protein in determining active site geometric and electronic structure

The electronic structure of the red copper site in nitrosocyanin is defined relative to that of the well understood blue copper site of plastocyanin by using low-temperature absorption, circular dichroism, magnetic circular dichroism, resonance Raman, EPR and X-ray absorption spectroscopies, combined with DFT calculations. These studies indicate that the principal electronic structure change in the red copper site is the sigma rather than the pi donor interaction of the cysteine sulfur with the Cu 3d(x2-y2) redox active molecular orbital (RAMO). Further, MCD data show that there is an increase in ligand field strength due to an increase in coordination number, whereas resonance Raman spectra indicate a weaker Cu-S bond. The latter is supported by the S K-edge data, which demonstrate a less covalent thiolate interaction with the RAMO of nitrosocyanin at 20% relative to plastocyanin at 38%. EXAFS results give a longer Cu-S(Cys) bond distance in nitrosocyanin (2.28 A) compared to plastocyanin (2.08 A) and also show a large change in structure with reduction of the red copper site. The red copper site is the only presently known blue copper-related site with an exogenous water coordinated to the copper. Density functional calculations reproduce the experimental properties and are used to determine the specific protein structure contributions to exogenous ligand binding in red copper. The relative orientation of the CuNNS and the CuSC(beta) planes (determined by the protein sequence) is found to be key in generating an exchangeable coordination position at the red copper active site. The exogenous water ligation at the red copper active site greatly increases the reorganization energy (by approximately 1.0 eV) relative to that of the blue copper protein site, making the red site unfavorable for fast outer-sphere electron transfer, while providing an exchangeable coordination position for inner-sphere electron transfer.     

Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.     

Electrodeposition and characterization of Cu-TiO2 nanocomposite coatings

Cu-TiO₂ nanocomposites were prepared by electrodeposition method onto copper substrate using an acid copper plating bath containing dispersed nanosized TiO₂. The composition of codeposited TiO₂ nanoparticles in the composite coatings was controlled by the addition of different concentrations of TiO₂ nanoparticles in the bath solution. The average crystallite size was calculated by using X-ray diffraction analysis and it was ~32 nm for electrodeposited copper and ~33 nm for Cu-TiO₂ composite coatings. The crystallite structure was fcc for electrodeposited copper and Cu-TiO₂ nanocomposite coatings. The surface morphology and composition of the nanocomposites were examined by scanning electron microscopy and energy dispersive X-ray spectroscopy analysis. The effect of TiO₂ content on the corrosion and wear resistance properties of the nanocomposite coatings was also presented. The codeposited TiO₂ nanoparticles in the deposit increased the corrosion and wear resistance, which were closely related with TiO₂ content in the nanocomposites. The wear resistance and microhardness of the Cu-TiO₂ nanocomposite coatings were higher than electrodeposited copper. The corrosion resistance property of the electrodeposited copper and Cu-TiO₂ nanocomposite coatings was evaluated by electrochemical impedance and Tafel polarization studies. Cu-TiO₂ composite coatings were more corrosion resistant than electrodeposited copper.     

A pre-concentration procedure employing a new imprinted polymer for the determination of copper in water

This work describes the development by response surface methodology (RSM) of a procedure for copper determination by inductively coupled plasma optical emission spectrometry (ICP OES) in water samples after extraction by copper imprinted polymer. Results of the two-level full factorial design (2⁴) based on an analysis of variance demonstrated that only the solution pH; amount of polymer and adsorption time were statistically significant. Optimal conditions for the extraction of copper samples were obtained by using Box-Behnken design. Solution pH; amount of polymer and adsorption time were regarded as factors in the optimisation study. The working conditions were 4.6, 0.03?g and 3.5?h, for solution pH, amount of polymer; and adsorption time, respectively. Under the optimised experimental conditions, the detection limit of the proposed method followed by ICP OES was found to be 0.8?µg?L^?1. The relative standard deviation (RSD) was found to less than 0.81%. The pre-concentration factor was 22.5. The accuracy of the optimised procedure was evaluated by analysis of certified reference material. The method was applied to the determination of copper in water samples.     

Improved antibacterial activity of HAP garlanded PLGA ultrafine fibers incorporated with CuO: synthesis and characterization

Well-organized nanocrystalline hydroxyapatite nanoparticles garlanded poly(dl-lactide-co-glycolide) (PLGA) ultrafine fibers with efficient antibacterial properties are of great interest in the development of new products. In the present study, hydroxyapatite doped PLGA ultrafine fibers incorporated with copper oxide nanocrystals were fabricated via two step methodology. Primarily; copper oxide nanocrystals were synthesized using wet chemical method. Then the as-synthesized nanocrystals were used for the preparation of composite fibers using electrospinning technique. The properties of pure and composite ultrafine fibers were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and electron probe mapping analysis. The in vitro antimicrobial activity of synthesized pure and hydroxyapatite doped PLGA ultrafine fibers was investigated against model organism Escherichia coli (gram negative) using optical density method and morphological damage was observed by TEM. Ultrafine fibers with average diameter ranges from 1.0 to 1.2 μm were obtained. Uniform distribution of hydroxyapatite was observed. Admirable antimicrobial activity against E. coli was achieved which could be attributed by the synergy between hydroxyapatite and copper oxide. In contrast to pristine PLGA, lower concentrations of hydroxyapatite–copper oxide doped PLGA nanocomposite were needed to strongly inhibit the growth of E. coli. Our results report successful preparation of hydroxyapatite–copper oxide based novel nanocomposite. The developed hybrid nanocomposite possess exceptionally good antibacterial activity against E. coli due to the synergistic effect of hydroxyapatite and copper oxide. The antimicrobial nanocomposite can be utilized for a range of bio-functional purposes such as a good candidate for water purification, antibiofouling, wound dressings and bone tissue engineering etc.     

涡旋提取-电感耦合等离子体发射光谱(ICP-OES)法测定酸性和中性土壤中交换性盐基总量

传统的土壤交换性盐基总量检测方法前处理过程复杂,检测时间长,建立涡旋提取-电感耦合等离子体发射光谱(ICP-OES)法,大大提高了检测效率。采用涡旋提取中性和酸性土壤中交换性盐基总量,结合电感耦合等离子发射光谱仪（ICP-OES）同时测定土壤提取液中交换性盐基总量钙镁钠钾含量。通过考察土液比,涡旋时间,涡旋转速以及方法的精密度和准确度。结果表明,最佳涡旋条件为土液比为1:50,涡旋时间为20 min,涡旋速度为1500 r/min。利用ICP-OES测定国家标准物质RMH-A275、RMH-A274和GBW07458a（ ASA-7a）土壤提取液中交换性盐基总量钙镁钠钾含量,各元素测定结果均在标准值范围内,相对标准偏差均小于2 %,交换性钙镁钠钾的方法检出限分别为0.048 cmol/kg、0.035 cmol/kg、0.038cmol/kg和0.072 cmol/kg。应用该方法检测20份耕地实际土壤样品,与国标法相比,交换性盐基总量钙镁钠钾的测定值相对误差均小于2 %,满足土壤样品分析检测的要求。该方法操作简便、试剂用量少,准确度和精密度好,适用于大批量生态地球化学评价土壤样品中交换性盐基总量钙镁钾钠的测定。     

Determination of trace impurities in high purity copper using sector-field ICP-MS: continuous nebulization, flow injection analysis and laser ablation

High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was applied for multielement-determination in high-purity copper (approx. 99.99%). The samples were introduced into the instrument by three different introduction systems, which were studied with respect to high accuracy, low detection limits and fast analysis: continuous nebulization (CN), flow injection analysis (FIA) and laser ablation (LA). The trueness of the applied method was checked by the analysis of high-purity copper reference material (BCR Cu074). All values obtained for this CRM using CN were in the range of the stated uncertainty for the 9 elements determined: Ag, As, Bi, Cr, Fe, Ni, Pb, Sb, and Sn with contents in the range of 0.5–13 μg/g. Another approach for checking the trueness of the method was to compare the results obtained by this method characterizing the purity of a 4N (99.99% copper content) copper material with those obtained by application of electrothermal atomic absorption spectrometry (ET-AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). For further characterizing, the concentrations of 49 elements were found in this material below detection limits of HR-ICP-MS in the range of low μg/kg and sub μg/kg. The combination of HR-ICP-MS and a flow injection analysis system (FIAS) improved the robustness of the system in regard to high matrix concentrations. Therefore, matrix concentrations up to 4 g/L could be used for liquid analysis and detection limits were lowered by a factor of 2–5. A calibration method for bulk analysis with laser ablation was developed with doped copper powder as pressed pellets for calibration standards. This method proved to be an excellent fast semi-quantitative method, which was less time consuming in comparison with the analysis of liquids. After application of correction factors the deviation between the results obtained by laser ablation and by analysis of liquids was ≈ 15% for most elements. The method offered the possibility to check for potential losses of analytes occurring during the wet chemical operations. Received: 23 November 1998 / Revised: 25 February 1999 / Accepted: 2 March 1999     

Determination of trace impurities in high purity copper using sector-field ICP-MS: continuous nebulization, flow injection analysis and laser ablation

High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was applied for multielement-determination in high-purity copper (approx. 99.99%). The samples were introduced into the instrument by three different introduction systems, which were studied with respect to high accuracy, low detection limits and fast analysis: continuous nebulization (CN), flow injection analysis (FIA) and laser ablation (LA). The trueness of the applied method was checked by the analysis of high-purity copper reference material (BCR Cu074). All values obtained for this CRM using CN were in the range of the stated uncertainty for the 9 elements determined: Ag, As, Bi, Cr, Fe, Ni, Pb, Sb, and Sn with contents in the range of 0.5–13 μg/g. Another approach for checking the trueness of the method was to compare the results obtained by this method characterizing the purity of a 4N (99.99% copper content) copper material with those obtained by application of electrothermal atomic absorption spectrometry (ET-AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). For further characterizing, the concentrations of 49 elements were found in this material below detection limits of HR-ICP-MS in the range of low μg/kg and sub μg/kg. The combination of HR-ICP-MS and a flow injection analysis system (FIAS) improved the robustness of the system in regard to high matrix concentrations. Therefore, matrix concentrations up to 4 g/L could be used for liquid analysis and detection limits were lowered by a factor of 2–5. A calibration method for bulk analysis with laser ablation was developed with doped copper powder as pressed pellets for calibration standards. This method proved to be an excellent fast semi-quantitative method, which was less time consuming in comparison with the analysis of liquids. After application of correction factors the deviation between the results obtained by laser ablation and by analysis of liquids was ≈ 15% for most elements. The method offered the possibility to check for potential losses of analytes occurring during the wet chemical operations. Received: 23 November 1998 / Revised: 25 February 1999 / Accepted: 2 March 1999     

Defect of nanocrystalline copper and silver

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水和氯化铵提取-电感耦合等离子体发射光谱(ICP-AES)法测定石灰性土壤中交换性钾钠钙镁

为了提高石灰性土壤中交换性钾钠钙镁的分析效率及分析准确度,本文创新性采用水和氯化铵对石灰性土壤进行处理,并采用振荡交换、离心分离的方式进行石灰盐清洗、钾钠钙镁离子交换提取,提取液直接在电感耦合等离子体发射光谱仪(ICP-AES)上测定。该方法交换性盐基钙、镁、钾、钠的检出限分别为0.01、0.009、0.004、0.012cmol/kg。用国家一级标准物质GBW07498-新疆棕漠土和新疆地区石灰性土壤进行验证,方法精密度均小于5%,回收率在97％~105%。方法适用于石灰性（碱性）土壤（特别是新疆土壤）样品中交换性钾、钠、钙、镁的分析测定。     

Evaluation and Application of the Internal Standard Technique for the Direct Determination of Copper in Fruit Juices Employing Fast Sequential Flame Atomic Absorption Spectrometry

Abstract

The present paper describes the evaluation and application of internal standard for the determination of copper in fruit juices, employing Fast Sequential Flame Atomic Absorption Spectrometry (FS FAAS). The internal standards tested were indium, cobalt, and nickel using correlation graphs. However, indium was used, considering the composition of the samples. After this step, copper was determined in fruit juices using indium as internal standard. This method allows the determination of copper with a limit of quantification of 0.011 mg L^?1. The fruit juice samples selected for analysis were of grape, orange, pineapple, peach, cashew, and strawberry. The contents of copper in these samples varied from 0.02 to 0.42 mg L^?1. The analytical results were compared with the results obtained by analysis of these samples after complete mineralization using acid digestion and determination employing FS FAAS. The statistical comparison by a t-test (95% confidence level) showed no significant difference between the results. The relative standard deviations (RSD) with and without the use of the internal standard for a copper solution containing 0.4 mg L^?1 were of 0.62 and 1.94%, respectively. The use of indium as internal standard provided more accurate analytical results, as well as better analytical performance for the determination of copper in juice samples.     

Speciation Analysis of Serum Copper by Ultrafiltration Combined with Graphite Furnace Atomic Absorption Spectrometry

Ultrafiltration combined with graphite furnace atomic absorption spectrometry (GFAAS) was used to study protein binding and speciation of copper in human serum. Ultrafiltration was carried out using a cell unit with ultrafiltration membranes having a nominal cut‐off of 10,000 Dalton. The effects of various experimental factors including the kind and concentration of electrolyte, sample storage, pH. pressure and the preconditioning of the membranes on the speciation analysis of serum copper by ultrafiltration were examined. It was observed that 4.5 ± 2.3% of the total copper in serum was ultrafiltrable and this value did not seem to be influenced by the total serum elemental concentration, the pH (6.5–10) and the pressure (≤ 1.5 kg/cm²). The preconditioning of the ultrafiltration system with 0.1 mol/L calcium nitrate can overcome the adsorption loss of copper effectively, and the addition of tris‐HCl solution (pH 7.4) to serum accelerates the ultrafiltration. The present method was proved to be suitable for speciation analysis for its simplicity, rapidity, small sample requirement and easy control. The results obtained with the method are accurate and reliable.     

The rapid determination of silver to silver plus copper ratios in coins using 14 MeV neutron activation analysis

A non-destructive method for the analysis of the silver to silver plus copper ratio in coins using 14 MeV neutron activation analysis has been studied. The mass of silver to the mass of copper is obtained by measuring the 0.511 MeV annihilation radiation emitted by⁶⁴Cu and¹⁰⁶Ag at two separate times after irradiation. A series of British silver three-penny pieces dated 1891–1941 were analysed and agreed well with the mint assay. The interference from the presence of zinc in some coins was investigated.