Speciation of nickel in surface waters measured with the Donnan membrane technique

The evaluation of the ecotoxicological risk of nickel (Ni) in surface water is hampered by a lack of speciation data. Six surface waters were sampled and speciation of Ni(II) was measured by the Donnan membrane technique (DMT) combined with radiochemical determination of ⁶³Ni. The free Ni²⁺ ion fraction in the dissolved (<0.45 μm) phase was determined at background Ni concentration ((4-8) × 10⁻⁸ M) and at concentrations in the range of toxicity thresholds for the Ni sensitive species Cerodaphnia dubia (5 × 10⁻⁸ to 2 × 10⁻⁶ M). The free ion fraction ranged from 4 to 45% at background Ni and increased with increasing Ni concentration and water hardness and with decreasing pH. The equilibration time after addition of Ni²⁺ (3 h-7 d) did not significantly change the measured free ion fraction. Predictions of the Humic-Ion Binding Model WHAM (Windermere Humic Aqueous Model) VI overestimated the observed free Ni²⁺ fraction (median > two-fold), even when assuming that all dissolved organic matter (DOM) was present as fulvic acid (FA). The impact of several model parameters affecting the prediction of Ni speciation were evaluated, including the solubility product of Fe(OH)₃, which affects the Fe competition for complexation by DOM. The best fit (R² = 0.88) was obtained by increasing only the distribution term ΔLK₂, which modifies the binding strength of multi-dentate sites, to accommodate the observed dependence of free ion fraction on Ni concentration.     

Speciation studies of nickel and chromium in wastewater from an electroplating plant

A speciation scheme involving the use of flame atomic absorption spectrometry (FAAS) and differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV) techniques was applied to studies of nickel and chromium in wastewater from a nickel-chrome electroplating plant. Dimethylglyoxime (DMG) and diethylenetriaminepentaacetic acid (DTPA) were employed as complexing agents for adsorptive voltammetric determination of Ni and Cr, respectively. Cr(III) and Cr(VI) were determined by exploiting differences in their reactivity towards DTPA at HMDE. Total dissolved metal content was in the range 2906-3141 and 30.7-31.2 mg l⁻¹ for Ni and Cr, respectively. A higher percentage of the metal was present as labile species (mean value of 67.9% for Ni and 79.8% for Cr) suggesting that strongly binding ligands are not ubiquitous in the sample. About 77.8% of Cr was found to exist in the higher oxidization state, Cr(IV). Results on effect of dilution on lability of the metal forms in the sample using DPAdCSV showed slight peak shifts to a more negative (cathodic) value by −0.036 V for Ni and −0.180 V for Cr with a dilution factor of 100, while peak intensity (cathodic current) remained fairly constant.     

Arsenic Speciation Governs Arsenic Uptake and Transport in Terrestrial Plants

Arsenic is a carcinogenic metalloid that occurs in the environment in a variety of chemical forms, showing different mobility, bioavailability and toxicity. Terrestrial plants may accumulate large amounts of arsenic. To understand how terrestrial plants take up, transport and metabolise these arsenic species, it is essential to characterise arsenic speciation in plant tissues. Given that As species can be transformed from one form to another during sample preparation and the measurement process, arsenic speciation in biological extracts needs to be performed with great care. This paper describes the methods used to measure arsenic speciation in plant tissue and assesses the role of As speciation in As metabolism in higher plants.     

Speciation analysis to unravel the soil-to-plant transfer in highly arsenic-contaminated areas in Cornwall (UK)

Two areas near derelict calciners in Cornwall (UK) were chosen to study the uptake of arsenic from arsenic-contaminated soil into indigenous plants (heather, Calluna vulgaris; blackberry, Rubus ulmifulmus; gorse, Ulex europaeus). With total arsenic concentrations in soil ranging from 1240 to 2860 mg kg^?1 at Site 1 (Tuckingmill), no adverse effects on the growth of the plants studied were observed. Very low soil-to-plant transfer factors (0.01 to 0.03) were found although they were much higher when the extractable soil arsenic concentrations were taken into account (0.1 to 1.1). In the central dump area at Site 2 (Bissoe, 9.78% [w/w] arsenic in soil), the only plant to grow was heather, although it was severely impaired. However, heather was thriving at the edge of the dump where higher soil arsenic concentrations were found (10.32% [w/w]), indicating that arsenic is not a growth-limiting factor in itself. Soil-to-plant transfer factors in the range 2 × 10^?5–9 × 10^?4 confirm that arsenic is indeed effectively excluded from uptake, even taking into account extractable soil arsenic concentrations (9 × 10^?4–1.2 × 10^?2).

Extraction of bioavailable arsenic from soil using 0.05 mol L^?1 ammonium sulphate yielded recoveries from 1.18 to 3.34% of the total arsenic, predominantly in the form of arsenate. Extraction of arsenic and its metabolites from plants was achieved with water or a water/methanol mixture yielding recoveries up to 22.4% of the total arsenic, with arsenite and arsenate the predominant arsenic species and a minor fraction consisting of methylarsonic acid, dimethylarsinic acid and trimethylarsine oxide. The identity of the remainder of the non-extractable arsenic species still has to be revealed. Although the data suggest that higher plants synthesise organoarsenic compounds it cannot be excluded that symbiotic organisms have synthesised these compounds.     

铬形态分析的分离富集/原子光谱分析研究进展

综述了铬形态分析的分离富集／原子光谱分析研究进展,详细讨论了铬的存在形态、铬形态分析中的样品前处理方法、分离富集／原子光谱检测技术及应用。     

联用技术在砷形态分析中应用的研究进展

对近年来联用技术在砷的形态分析中应用的研究成果以及存在的一些问题作了详细的阐述，包括：HPLC-AAS，HPIE-AFS，HPLC-ICP-MS，CZE-ICP-MS和HPLC或CZE与ESI-MS联用。     

酒石酸掩蔽铝-丁二酮肟重量法测定镍钴铝三元氢氧化物中镍

镍钴铝三元氢氧化物中Ni质量分数为45%~60%、Al为0.5%~1.5%,丁二酮肟沉淀镍的pH条件下,Al3+会水解沉淀而干扰测定。试验对丁二酮肟重量法进行改进,采用酒石酸作为Al的掩蔽剂,从而建立了酒石酸掩蔽铝-丁二酮肟重量法测定镍钴铝三元氢氧化物中Ni含量的方法。试验评价了Al对丁二酮肟重量法测Ni的干扰,并确定了酒石酸的最佳掩蔽用量,测定实际样品801505型镍钴锰三元氢氧化物（Ni0.8Co0.15Al0.05(OH)2）和851005型镍钴锰三元氢氧化物（Ni0.85Co0.1Al0.05(OH)2）的RSD（n=11）分别为0.24%、0.31%,加标回收率分别为100.20%、99.68%,且测定值与ICP-AES基本一致。     

Speciation of organotin compounds by tandem mass spectrometry

The collison-induced dissociation of a range of organotin compounds has been examined by tandem (MS–MS) mass spectrometry in order to investigate the potential of the technique for speciation without prior chromatographic separation. Tables of parent–daughte ion relationships are prepared for a group of six closely related compounds. The results obtained are sufficiently characteristic to distinguish between the isolated compounds and to identify the individual components of a simple mixture. This procedure has potential applications for less volatile compounds and for quantitative analysis.     

Applications of Nanoparticles in Elemental Speciation

Nanoparticles, notable for their small size, high surface area to volume ratios, and strong adsorption capacity, have been the subject of great interest in analytical chemistry. Over the past decade, nanoparticles have been widely used as adsorbents for elemental speciation. Elemental ions or chelates may interact with nanoparticles by van der Waals forces, hydrogen bonds, and hydrophobic interactions. Various types of nanoparticles used for elemental speciation, including magnetic nanoparticles, carbon nanotubes, metallic oxide nanoparticles, nanostructured mixed oxides, and ion imprinted polymer nanoparticles, are reviewed. Future trends and development in this research area are discussed.     

Speciation of organotin and organoarsenic in water samples

Determination of tributyltin concentrations in water at low levels (0.1–1 ppt) is possible with the hydride generation/gas chromatographic separation/atomic absorption spectrophotometric method. This technique can easily be adapted for the determination of arsenic and methylated arsenic species. Arsenic (III) and arsenic (V) can be separated by selective coprecipitation with dibenzyldithiocarbamate.     

固相萃取–HPLC–ICP/MS法测定水中的烷基汞

建立了固相萃取、高效液相色谱与电感耦合等离子体质谱联用技术测定水中烷基汞的方法。对固相萃取、高效液相色谱和电感耦合等离子体质谱的实验条件进行了优化。在优化条件下,甲基汞和乙基汞的检出限分别为0.5,0.7 ng/L。对地表水、工业废水和生活污水3种水样分别加标10.0,50.0 ng/L进行测定,测定结果的相对标准偏差为3.3%~9.6%(n=6),加标回收率在81.0%~103.0%之间。该方法灵敏度高,实用性强。     

Study of the decomposition of supported nickel acetylacetonate by thermal techniques

The decomposition of supported nickel acetylacetonate (AcacNi) was studied by using thermal techniques to evaluate the nature of the calcination products. Thermogravimetric techniques used in this work indicated transformations occurring during preparation and calcination steps. Results demonstrated the important influence of support modifications upon the catalyst nature finally obtained.     

HG-AFS测定垃圾焚烧炉烟道气中锑的形态

以某垃圾焚烧厂焚烧炉产生的烟道气为研究对象,采用酒石酸提取,对烟道气中sb形态进行了分析,用HG-AFS分别测出样品中Sb（Ⅲ）和总Sb的量,差减法得到Sb（V）的量。结果表明,sb（Ⅲ）和总sb检出限分别为0．13μg／L和0．11μg/L,相对标准偏差（RSD,n=11）分别为5．8％和6．3％,加标回收率在84．8％-113％。     

Speciation of tin in sediments and soils by leaching

For the evaluation of the speciation of Sn in solid samples, a leaching sequence is presented, which takes into account the special properties of the element investigated. The sample is leached with ethanol (organics), 25% acetic acid (carbonates), oxalate (coprecipitation upon Fe/Mn-hydroxides), then oxidized with KMnO₄ (sulfides), and finally sublimed with NH₄I (cassiterite); the silicate fraction is found as the difference to the total decomposition value (e.g. LiBO₂).Final determinations are done by hydride AAS from tartaric acid-solutions, except the ethanol fraction which is submitted to ETA-AAS. In the furnace, addition of HNO₃ and H₂O₂ and rapid heating in the gas-stop mode results in equal sensitivity of organic and inorganic tin in the ethanol extract. The proposed method is checked by coprecipitation/adsorption experiments and by addition of tin-bearing minerals to a natural sediment.The method was applied to fresh water sediments. In sediment cores, the KMnO₄ fraction was dominant, whereas in an oxic surface sediment NH₄I releases the main fraction (cassiterite).     

联用技术测定富硒农产品中硒的形态研究进展

硒的营养功能与农产品硒的形态息息相关。联用技术作为元素形态分析的有效方法,近年来受到了人们广泛关注。对用联用技术测定富硒农产品中硒的形态研究现状及进展进行了综述,包括前处理技术、色谱分离技术和定量检测方法等3个方面。     

Arylcyanation of alkynes catalyzed by nickel

A nickel catalyst prepared from Ni(cod)₂ and PMe₃ is found to effect arylcyanation reaction of alkynes, namely, cleavage of a C-CN bond of an aryl cyanide followed by addition of each fragment across an alkyne. A wide range of functional groups in aryl cyanides tolerated the catalysis, giving variously functionalized β-arylalkenenitriles stereoselectively.     

高效液相色谱法研究铝形态的可靠性

高效液相色谱法在铝形态的研究中发挥着举足轻重的作用,而铝形态的易变性和复杂性要求色谱条件无侵入性和检测手段具有形态选择性。文中列举了若干实例说明高效液相色谱法在铝形态分析中的常用方法和注意事项。     

Speciation of selenoamino acids by on-line HPLC ETAA spectrometry

An analytical method was developed to determine selenoamino acids in the presence of other compounds. Separation has been achieved by High Performance Liquid Chromatography (HPLC) using electrothermal atomic absorption (ETAA) spectrometry as a very sensitive and element-specific detector. On-line HPLC ETAAS speciation of selenocystine and selenomethionine has been studied, using a laboratory made interface. Analytical characterization of the method has been realized with standard solutions. Using a 100μl sample loop, the detection limits were calculated as 8 μgl^?1 for selenomethionine and 10 μgl^?1 for selenocystine with repeatability and reproducibility of 4% and 7% respectively. The method has been applied to the determination of selenoamino acids in an extract of white clover (CRM402) certified for total selenium.     

色谱法分析环境中铝形态的进展

综述了色谱法在环境体系铝形态研究中的应用进展,比较了离子交换色谱、体积排阻色谱、反相高效液相色谱、快速蛋白质液相色谱、毛细管电泳以及流路中嵌入色谱小柱的流动注射分析法的优缺点。引用文献55篇。