Application of radioisotopes in column chromatography on substituted celluloses-VI The separation of antimony from manganese, iron and other metals

The Chromatographic behaviour of nanogram amounts of antimony in ethyl ether medium was studied by radioisotope techniques on cellobiose, cellulose and seven substituted celluloses. It was found that antimony is strongly retained and can be separated from macro amounts of manganese, iron, gold, uranium, mercury, arsenic and several other metals. Antimony could be quantitatively recovered by elution from natural cellulose and cellobiose. The method can be applied in several analytical problems concerning the separation of traces of antimony.     

XPS and XAES analysis of copper,arsenic and sulfur chemical state in enargites

Enargite, a copper arsenic sulfide with the formula Cu₃AsS₄ is of environmental concern due to its potential to release toxic arsenic species. The oxidation and dissolution of enargite are governed by the composition and chemical state of the outermost surface layer. Qualitative and quantitative analysis of the enargite surface can be initially obtained on the basis of X‐ray photoelectron spectroscopy (XPS) binding energy and intensity data. However, a more precise determination of the chemical state of the principal elements of enargite (copper, arsenic and sulfur) in the altered surface layer and in the bulk of the mineral requires a combined analysis based on XPS photoelectron lines and the corresponding X‐ray excited Auger lines. On the basis of results obtained on natural and synthetic enargite samples and on standards of sulfides and oxides, the Auger parameter α′ of different compounds was calculated and the Wagner chemical state plots were drawn for arsenic, copper and sulfur. Arsenic in enargite is found to be in a chemical environment similar to that of arsenides or elemental arsenic, whereas copper in enargite is in a chemical state that corresponds to copper sulfide, Cu₂S, for all samples irrespective of surface treatment (natural or freshly cleaved). Only sulfur changed from a chemical state similar to that of copper or iron sulfide in freshly cleaved samples to another state in natural enargite in the as‐received state. Thus, it is the sulfur atom at the surface of enargite that is most susceptible to changes in the enargite surface state and composition. A more detailed interpretation of this behavior, based on differences in the initial and final state effects, is proposed here. The concept of Auger parameter and chemical state plot, used here for the first time for investigating enargite, has proved to be a method to unambiguously assign the chemical state of the principal elements copper, arsenic and sulfur in these minerals. Copyright © 2006 John Wiley & Sons, Ltd.     

Application of radioisotopes in column chromatography on substituted celluloses--II. The separation of gold from silver, iron and other metals

The chromatographic behaviour of several metals has been studied on columns of natural and substituted celluloses, by using radioisotopes. It has been found that gram and nanogram amounts of gold are not adsorbed on natural cellulose, and consequently gold can be separated from nanogram amounts of silver, iron, zinc, cadmium, chromium, manganese and cobalt. Gold has a limited tendency to form complexes with the functional groups of the celluloses, but the other metals mentioned formed very stable complexes. The results have also been compared with those obtained for mercury.     

Determination of trace arsenic on hanging copper amalgam drop electrode

Hanging copper amalgam drop electrode has been applied for trace determination of arsenic by cathodic stripping analysis. Detection limit for As(III) as low as 0.33 nM (0.02 μg/L) at deposition time (240 s) could be obtained. For seven successive determinations of As(III) at concentration of 5 nM relative standard deviation was 2.5% (n = 7). Interferences from selected metals and surfactant substances were examined. Absence of copper ions in sample solution causes easier optimization and makes method less vulnerable on contamination. The developed method was validated by analysis of certified reference materials (CRMs) and applied to arsenic determinations in natural water samples.     

Inorganic arsenic speciation in water and seawater by anodic stripping voltammetry with a gold microelectrode

The determination of arsenic in sea and freshwater by anodic stripping voltammetry (ASV) was revisited because of problems related to unstable peaks and inconveniently strong acidic conditions used by existing methods. Contrary to previous work it was found, that As(III) can be determined by ASV using a gold microwire electrode at any pH including the neutral pH typical for natural waters. As(V) on the other hand, requires acidification to pH 1, but this is still a much milder condition than used previously. This is the basis of a new method for the chemical speciation of arsenic in natural waters. The limits of detection are 0.2 nM As(III) at pH 8 and 0.3 nM combined arsenic (III + V) at pH 1 with a 30 s deposition time. These limits are lowered by extending the deposition time. The detection step at pH 8 was stripping chronopotentiometry (SC) as this was found to give a lower detection limit than ASV. Copper is co-determined simultaneously with arsenic. The method was applied successfully to the determination of arsenic as well as copper in samples from the Irish Sea, mineral water and tap water.     

碘酸钾滴定法测定铜阳极泥分银渣中的锡

建立了碘酸钾滴定法测定铜阳极泥分银渣中锡的含量。通过硝酸溶解,过滤除铜,还原铁粉置换分离锑、铋、砷等元素,消除了铜阳极泥分银渣中的铜、锑、砷等杂质元素对锡测定的干扰。方法加标回收率在99.7%~100%。精密度实验结果表明,相对标准偏差(RSD,n=11)小于1.1%。操作过程简单,能满足生产的需要。     

In Process Citation

The chromatographic behaviour of zinc, cadmium and mercury on columns of natural cellulose and substituted celluloses is studied using (65)Zn, (109)Cd and (203)Hg radiotracers. Traces of zinc and cadmium are strongly retained by the functional groups attached on the substituted celluloses ; on the contrary mercury is not retained to any extent. Nanogram amounts of zinc, cadmium and other metals are separated from 3 g of mercury on cellulose phosphate in ethyl ether.     

Determination of arsenic and antimony in electrolytic copper by anodic stripping voltammetry at a gold film electrode

A simple procedure is described for the determination of arsenic and antimony in electrolytic copper. The copper is digested with nitric acid and copper is separated from arsenic and antimony by passing an ammoniacal solution of the sample through a column of Chelex-100 resin. After digestion with sulphuric acid and reduction to arsenic(III) and antimony(III) with sodium sulphite in 7 M sulphuric acid at 80°C, both arsenic and antimony are deposited at-0.30V and their total is determined by anodic stripping; antimony is then selectively deposited at -0.05 V for anodic stripping. The lower limits of determination are 56 ng As and 28 ng Sb per gram of copper; relative standard deviations (n = 5) are in the ranges 6.1–15.0% for 5.5—0.5 ppm arsenic in copper and 4.1–6.8% for 2.6—0.6 ppm antimony.     

Mutual interactions of elements in the hydride technique in atomic absorption spectrometry: Part 1. Influence of selenium on arsenic determination

The interference from selenium(IV) on the determination of arsenic(III) and -(V) by hydride-generation atomic absorption spectrometry is removed if copper is added to the sample solution. This prevents the evolution of selenium hydride but has no influence — up to certain copper concentrations — on the formation of arsine. The possible interference mechanism is discussed. Interferences on selenium determinations are also described.     

A chemical enhancement method for the spectrophotometric determination of trace amounts of arsenic

A highly sensitive spectrophotometric method for the determination of 0.03-1.0 microg of arsenic is described. After extraction as AsI(3) into benzene, it is selectively stripped into water. Both the arsenic(III) and iodide present in the aqueous phase are made to react with iodate in acidic medium in the presence of chloride to form the anionic chloro complex, ICl(-)(2). The determination is completed after extraction of ICl(-)(2) species as an ion-pair with Rhodamine 6G into benzene and measuring the absorption of the extract at 535 nm. The coefficient of variation is 1.5% for 10 determinations of 0.5 microg of arsenic. The method has been applied to the determination of arsenic content in plant materials, high purity iron, copper base alloys and inorganic arsenic levels of natural waters.     

Neutron activation analysis of chalcophile elements using a chelating-agent loaded resin as a group separator

A chelating-agent loaded resin consisting of 8-quinolinol-5-sulfonic acid and an anion-exchange resin was prepared in order to apply the resin to the selective concentration of trace amounts of chalcophile elements in natural water samples prior to neutron activation analysis. Trace amounts of arsenic as well as copper and zinc were successfully collected and determined by the proposed method.     

The electrochemical behavior of ad-atoms and their effect on hydrogen evolution: Part II. Arsenic ad-atoms on platinum

The state of an arsenic layer electrodeposited at various potentials on platinum electrodes has been examined electrochemically. The relation between the state and the electrocatalytic activity for hydrogen evolution has been investigated. The number of vacant sites have been found to increase with lowering of the deposition potential. The activity has been found to depend not on the amount of deposited arsenic but on the number of vacant sites. The difference in the effects of arsenic and of copper on hydrogen evolution is pointed out. This is attributed to the difference in the affinity of the ad-atoms for hydrogen.     

Solvent extraction of arsenic(V) with dispersed ultrafine magnetite particles.

The solvent extraction of arsenic(V) was investigated using heptane containing ultrafine magnetite particles and hydrophobic ammonium salt. Arsenic(V) was favorably extracted from aqueous solutions of pH ranging over 2-7, where the distribution ratio (10(3)) was independent of the pH. Although the addition of alkyl ammonium salt improved the phase separation, no notable influence was observed on the extraction of arsenic(V). Oleic acid suppressed the distribution ratio of arsenic(V) when the concentration exceeded 10(-2) M. Sulfate did not interfere with the extraction, while the presence of more than 10(-3) M phosphate decreased the distribution ratio. Metal cations including calcium(II), manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and lanthanum(III) did not give any serious interference up to the 10(-4) M level. According to equilibrium and kinetic studies, the extraction of arsenic(V) can be interpreted by the adsorption of H2AsO4- onto the surface of dispersed magnetite particles. The relationship between the amount of arsenic(V) extracted in the organic phase and that remaining in an aqueous phase followed a Langmuir-type equilibrium equation. The maximum uptake capacity was determined to be 4.8 x 10(-4) mol/g-magnetite (36 mg As/g). The arsenic(V) extracted in the organic phase was quantitatively recovered by back-extraction with an alkaline solution.     

Activity of Arsenic in Liquid Cu–Fe Base Alloys

Summary. The activity of arsenic in liquid Cu–Fe base alloys was determined by isopiestic and Knudsen cell-mass spectrometer methods. Based on the activity data, the volatilization of arsenic in the extraction and recycling of copper was thermodynamically evaluated.     

Determination of arsenic and arsenic compounds in natural gas samples

Organic arsenic compounds (trialkylarsines) present in natural gas were extracted by 10 cm³ of concentrated nitric acid from 1 dm³ of gas kept at ambient pressure and temperature. The flask containing the gas and the acid was shaken for 1 h on a platform shaker set at the highest speed. The resulting solution was mixed with concentrated sulfuric acid and heated to convert all arsenic compounds to arsenate. Total arsenic was determined in the mineralized solutions by hydride generation. The arsenic concentrations in natural gas samples from a number of wells in several gas fields were in the range 0.01–63 μ As dm^?3. Replicate determinations of arsenic in a gas sample with an arsenic concentration of 5.9 μ dm^?3 had a relative standard deviation of 1.7%. Because of the high blank values, the lowest arsenic concentration that could be reliably determined was 5 ng As dm^?3 gas. Analysis of nonmineralized extracts by hydride generation identified trimethylarsine as the major arsenic compound in natural gas. Low-temperature gas chromatography-mass spectrometry showed more directly than the hydride generation technique, that trimethylarsine accounts for 55–80% of the total arsenic in several gas samples. Dimethylethylarsine, methyldiethylarsine, and triethylarsine were also identified, in concentrations decreasing with increasing molecular mass of the arsines.     

Effect of cellulase adsorption on the surface and interfacial properties of cellulose

The surface properties of several purified cellulose (Sigmacell 101, Sigmacell 20, Avicel pH 101, and Whatman CF 11) were characterised, before and after cellulase adsorption. The following techniques were used: thin-layer wicking (except for the cellulose Whatman), thermogravimetry, and differential scanning calorimetry (for all of the above celluloses). The results obtained from the calorimetric assays were consistent with those obtained from thin-layer wicking – Sigmacell 101, a more amorphous cellulose, was the least hydrophobic of the analysed celluloses, and had the highest specific heat of dehydration. The other celluloses showed less affinity for water molecules, as assessed by the two independent techniques. The adsorption of protein did not affect the amount of water adsorbed by Sigmacell 101. However, this water was more strongly adsorbed, since it had a higher specific heat of dehydration. The more crystalline celluloses adsorbed a greater amount of water, which was also more strongly bound after the treatment with cellulases. This effect was more significant for Whatman CF-11. Also, the more crystalline celluloses became slightly hydrophilic, following protein adsorption, as assessed by thin-layer wicking. However, this technique is not reliable when used with cellulase treated celluloses.     

电感耦合等离子体发射光谱法测定粗二氧化碲中 铜、铅、锑、铋、砷和硒

粗二氧化碲作为碲精炼或碲化工产品生产的重要原料,其中共存元素铜、铅、砷、锑、铋、硒含量的准确测定对于生产过程质量控制和贸易结算具有重要意义,但目前没有粗二氧化碲中铜、铅、砷、锑、铋、硒含量检测的标准分析方法。采用王水和饱和氟化氢铵分解试样,在王水和酒石酸介质中,选用Cu 327.393 nm、Pb 220.353 nm、Sb 217.582 nm、Bi 223.061 nm、As 193.696 nm、Se 196.026 nm为分析谱线,采用电感耦合等离子体发射光谱(ICP-AES)法测定粗二氧化碲中铜、铅、锑、铋、砷和硒含量。各元素校准曲线的相关系数均大于0.999;铜、铅、锑、铋、砷和硒的检出限分别为0.0004%、0.0005%、0.0006%、0.0007%、0.0004%和0.0007%,定量检出限分别为0.0012%、0.0016%、0.0020%、0.0025%、0.0013%和0.0025%。按照实验方法测定5个粗二氧化碲样品中铜、铅、锑、铋、砷和硒,测定结果的相对标准偏差(RSD,n=7)为0.79%~4.8%,加标回收率为96.0%~103%。方法简单,精密度和准确度较高,可用于测定粗二氧化碲中铜、铅、砷、锑、铋、硒含量。     

Determination of Copper in the Presence of Various Amounts of Arsenic with L‐Cysteine Modified Gold Electrodes

An L ‐cysteine modified gold electrode for the determination of copper in the presence of various amounts of arsenic with anodic stripping voltammetry has been studied. The electrode was fabricated by immersing a gold electrode in an ethanol solution of 5mM L ‐cysteine for 60 min. Various parameters, such as the effect of different supporting electrolytes, the pH of the electrolyte and the deposition potential were investigated. Under optimum conditions, copper was accumulated at ?0.3 V (vs. SEC) for 60 s in 0.1 M phosphate buffer pH 5.0 in the presence of different amounts of arsenic. Essentially the same sensitivities (0.33±0.001 μA/μM) and limits of detection (0.13±0.002 μM) of copper were obtained with various amount of arsenic in the range 2 μM to 20 μM.     

Syntheses and comparison of 2,6-di-O-methyl celluloses from natural and synthetic celluloses

2,6-Di-O-methylcellulose was prepared from natural and synthetic celluloses. Natural cellulose was converted to 2,6-di-O-thexyldimethylsilylcellulose, then to 3-mono-O-allyl-2,6-di-O-methylcellulose, and finally into 2,6-di-O-methylcellulose. Alternatively, 2,6 di-O-methylcellulose was synthesized from the synthetic cellulose derivative 3-mono-O-benzyl-2,6-di-O-pivaloylcellulose by depivaloylation and methylation to give 3-mono-O-benzyl-2,6-di-O-methylcellulose, which was debenzylated to yield the dimethyl ether. Both types of 2,6-di-O-methylcellulose are insoluble in water and common organic solvents. The structures of all cellulose derivatives were determined by NMR.     

Spectrophotometric determination of arsenic in concentrates and copper-base alloys by the molybdenum blue method after separations by iron collection and xanthate extraction

A method for determining 0.0001-1% of arsenic in copper, nickel, molybdenum, lead and zinc concentrates is described. After sample decomposition, arsenic is separated from most of the matrix elements by co-precipitation with hydrous ferric oxide from an ammoniacal medium. Following reprecipitation of arsenic and iron, the precipitate is dissolved in approximately 2 M hydrochloric acid and the solution is evaporated to a small volume to remove water. Arsenic(V) is reduced to the tervalent state with iron(II) and separated from iron, lead and other co-precipitated elements by chloroform extraction of its xanthate from an 11M hydrochloric acid medium. After oxidation of arsenic(III) in the extract to arsenic(V) with bromine-carbon tetrachloride solution, it is back-extracted into water and determined by the molybdenum blue method. Small amounts of iron, copper and molybdenum, which are co-extracted as xanthates, and antimony, which is co-extracted to a slight extent as the chloro-complex under the proposed conditions, do not interfere. The proposed method is also applicable to copper-base alloys.