Determination of cobalt by air-assisted liquid–liquid microextraction

Abstract

A rapid and selective technique for extraction, preconcentration and determination of trace amounts of cobalt in water and pharmaceutical samples by air-assisted liquid–liquid microextraction combined with flame atomic absorption spectrometry is proposed. 1-Nitroso-2-naphthol is used as a complexing agent and 1-octanol as an extraction solvent. Parameters relevant for analytical effectivity, i.e. pH of sample solution, concentration of complexing agent, volume of extraction solvent, and number of extraction cycles are optimized using a Box–Behnken design. At optimum conditions, a dynamic linear range of 5–600?µg L^?1 is obtained, with a limit of detection of 1.2?µg L^?1. The method is used for determination of Co(II) in environmental water and pharmaceutical samples.     

Biochemical properties of beryllium potentially relevant to its carcinogenicity†

The carcinogenicity of beryllium to several animal species is well established and evidence exists which strongly suggests that this is the case in human exposure. In this review several biochemical properties of the metallocarcinogen are considered including, the causation of cell transformation, and infidelity of DNA synthesis, inhibition of cell division and enzyme induction, and interference with regulatory mechanisms controlling gene expression. These effects are discussed in relation to beryllium chemistry, cellular accumulation mechanisms and distribution to subcellular organdies and molecular targets. It is suggested that the ultimate location and interactions of the metal ion in cell nuclei and its selective inhibition of certain protein phosphorylation reactions in particular are the biochemical effects potentially most relevant to induction of beryllium carcinogenesis.     

Rapid liquid chromatographic analysis of Metoclopramide in pharmaceutical preparations

A sensitive, accurate and reproducible method for the analysis of metoclopramide, a gastrointestinal drug, has been described. An isocratic HPLC elution method was employed which requires about 10 minutes to be performed. The concentration of metoclopramide hydrochloride preparations was found to be 95.1 ±0.3% and 94.21 ±0.25% in tablet and injection formulations, respectively.     

Speciation and carcinogenic classification—some limits of assessment and prevention procedures—the case of “nickel”

The speciation of nickel is of the highest importance for the definition of lists of substances for regulatory activity in terms of prevention, regarding possible cancer risk. A review is made of the different attitudes of outstanding administrations in front of nickel speciation. Some of them show a maximum of care in chemical definition, others reflect a lack of scientific rigor leading to generic classifications, more or less abusive. The great complexity of the chemistry and physicochemistry of nickel imposes the “two‐level speciation concept” (chemical and physicochemical), at least for compliance with the “Good Laboratory Practice” as far as experimental toxicology is concerned. Recommendations are exposed for the attention of toxicologists and regulators who have been for some years now extremely solicited for prevention aims.     

Levels of selected heavy metals in commercial fish from five freshwater lakes,Pakistan

The levels of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Hg are estimated by atomic absorption in the muscle of six commercial species of fish belonging to five freshwater lakes of Pakistan. The species included Mastacembelus armatus, Tor putitura, Mystus seenghala, Wallago attu, Catla catla and Labeo rohita. The fish were procured in comparable weight ranges so that a viable comparison of trace metal content could be effected. As, Fe, Pb, Zn and Hg showed elevated levels of 0.006–6.967, 0.933–6.133, 0.060–4.108, 0.978–5.363 and 0.030–3.211 μg/g, wet weight. The relevant statistical parameters, such as standard deviation, standard error, skewness and its t‐value are also reported for establishing the randomness of the distribution in relation to the corresponding data of freshwater lakes of the world and examined in view of species‐specificity and origin.     

云南宣威地区燃煤排放颗粒物中石英矿物的特征

云南宣威地区是我国人群肺癌死亡率最高的地区之一,过往研究表明,该区的高肺癌死亡率可能与居民室内燃煤排放颗粒物中的多环芳烃(PAHs)有关,而最近研究发现,其中的nm级石英可能是导致肺癌发生的原因, 但鲜见该区燃煤排放颗粒物中细粒石英矿物的研究. 为探究燃煤排放细粒矿物的分布特征,采集了肺癌高发区宣威市来宾镇及周边5个乡镇煤矿中的15个煤样,使用光学显微镜、X射线衍射仪(XRD)、带能谱的扫描电镜(SEM/EDS)分析了煤样的煤岩组分及矿物组成. 结果表明:宣威煤以中挥发分、较高镜质组烟煤为主,煤中主要矿物为石英、鲕绿泥石、高岭石和方解石;不同煤样中,矿物质的结晶程度有所差异;单颗粒统计结果显示,在所统计的775个矿物颗粒中,石英颗粒占37.9%,并且粒径多分布在1~2μm之间; 石英矿物颗粒的形状不规则且以微粒的形式填充在煤缝隙中. 石英与鲕绿泥石共存的现象显示,宣威煤中石英来源于富含Fe和Al的硅质热液流,而非岩石碎屑沉积;此外,在肺癌高发区(来宾镇),其煤中Si+Fe质矿物颗粒含量较Si质矿物高. 今后将重点研究石英颗粒在Fe参与下的生物活性.      

液氮冻融破碎生物污泥制备生物絮凝剂

利用城市剩余生物污泥,采用液氮冻融破碎、提取液提取的方法制备了生物污泥絮凝剂。对絮凝剂的制备条件及其絮凝性能进行了研究,结果表明:采用液氮冻融破碎,pH为1.0的稀盐酸溶液作为提取液提取所制备的絮凝剂,对高岭土悬浮液的絮凝效率可达98.5%。液氮冻融破碎的次数对絮凝剂制备没有明显影响。同时考察了絮凝剂投加量以及絮凝体系的pH对絮凝剂絮凝活性的影响。     

基于农户意愿的矿区耕地损害补偿测度研究——以庞庄、垞城、柳新煤矿开采为例

矿产资源的开发利用,在支撑社会经济发展的同时却带来区域资源生态环境的破坏,尤其是矿区农户承担着较大的外部成本。论文以矿区耕地损害为研究对象,在调查农户认知和接受补偿意愿的基础上,通过构建计量模型,测算基于农户意愿下的补偿额度。结果表明:①调查结果显示,69.19%的农户因煤矿开采失去一部分耕地,49.19%的农户表示耕地质量降低,95.14%的农户认为居住环境遭到破坏,93.51%的农户认为采矿破坏了耕种文化传承;②实证结果表明,庞庄、垞城、柳新煤矿周边农户每年接受最低补偿分别为34 780.80、36 506.85和35 397.60元/hm²,其中经济损害受偿意愿分别为12 731.10、18 982.80、11 230.95元/(hm²·a),社会保障损害受偿意愿分别为11 782.35、10 777.95、12 765.00元/(hm²·a),生态损害受偿意愿分别为7 277.10、4 282.35、7 306.05元/(hm²·a),文化传承损害受偿意愿分别为2 990.25、2 463.75和4 095.6元/(hm²·a);③对比分析发现,当前政策下矿区耕地损害补偿额度一般在9 458.70~15 764.40元/(hm²·a)之间,明显低于基于农户意愿下的补偿额度,并且56.76%的农户表示不接受一次性补偿。以上结果能够为矿区生态补偿和政策创新提供决策依据和定量参考。     

Influence of slope aspect on soil physico-chemical and biological properties in the mid hills of central Nepal

This study assessed the influence of slope aspect and land use on soil physio-chemical and biological properties (soil quality indicators) on contiguous south- and north-facing slopes of the mid hills in central Nepal, having the same climate, vegetation and parent material. In each aspect, two treatments (agriculture and forest) were chosen and four replicates taken for each treatment. Soil sample collection and microarthropod extraction was done according to the standard methodology: soil core samples (10 × 10 × 5 cm) and extraction with the modified Berlese–Tullgren funnel. The investigated soil variables were temperature, moisture, faunal abundance and diversity, organic matter, organic carbon, bulk density and pH. Except in a few cases, all considered soil properties showed significant differences between aspects and land use. Soils of the north-facing slope had higher SOC content, moisture, faunal abundance and diversity, and lower temperature and pH. Variations due to topographic aspect induced varied microclimates, causing differences in faunal abundance and diversity; soil moisture, temperature and organic matter trends affected soil fertility and ultimately soil quality. Further studies are required to clarify the complex interactions between soil properties (physio-chemical and biological), vegetation and slope aspect in Nepal, as well as to develop soil biological indicators as a tool to assist in sustainable land management.     

离子液体氯化1-辛基-3-甲基咪唑对酵母细胞增殖生长和细胞膜通透性的影响

为探讨咪唑类离子液体氯化1-辛基-3-甲基咪唑([C₈mim][Cl])对酵母细胞的增殖生长和细胞膜通透性的影响,以不同浓度的[C₈mim][Cl]处理酵母细胞,研究离子液体对酵母细胞增殖和菌落形成的影响,通过测定酵母细胞外液蛋白质和核酸的含量,判断膜通透性的大小和[C₈mim][Cl]对细胞膜性结构的损伤。结果显示,0.1 mmol·L^-1的[C₈mim][Cl]延长了酵母细胞到达对数生长期的时间,在6～9 h之间对酵母细胞的增殖存在明显的抑制作用。1 mmol·L^-1的[C₈mim][Cl]使酵母细胞增殖不能到达对数生长期,对酵母细胞的增殖一直具有较强的抑制作用。随着离子液体浓度的增加,小菌落的数量增多。当平板内[C₈mim][Cl]浓度达到10 mmol·L^-1时,完全抑制了菌落的形成。[C₈mim][Cl]处理酵母细胞后,细胞外液中OD₂₈₀、OD₂₆₀的值显著升高。研究表明,细胞膜等膜性结构通透性的增加是离子液体[C₈mim][Cl]抑制酵母细胞增殖生长的原因之一。