流动注射离子交换预浓集火焰原子吸收光谱法直接测定人尿中痕量镉

应用高效的流动注射在线离子交换预浓集火焰原子吸收光谱测定系统直接测定了人尿中痕量镉。选择２００μＬ锥形离子交换柱，内装多孔玻璃固定化的８－羟基喹啉离子交换剂，在ｐＨ９条件下样品流速为３．５ｍＬ／ｍｉｎ，４０ｓ装样，用２ｍｏｌ／ＬＨＣｌ洗脱，在分析速度为６０样／ｈ，获得３０倍的富集倍率。检出限为０．３μｇ／Ｌ。镉含量水平为４０μｇ／Ｌ的尿样，连续测定１１次的相对标准偏差为１．５％。尿标准参考物...?     

流动注射在线吸发离预浓集冷蒸气原子吸收法测定痕量镉

研究了IRC－718离子交换树脂、122螯合树脂和MuromacA-1树脂对镉 的预浓集条件,建立了超痕量镉的流动注射在线吸着分离预浓集冷蒸气发生原子吸收光谱测定方法,在每小时进样60,60和45次速度下检出限（3σ）分别为3．0,3．0和2．4ng/L,线性范围0－0．3μg/L,对0．2μg/L镉测定的相对标准偏差为2．0％－2．6％（n=11),。讨论了用这3种离子交换树脂微柱进行分离预浓集时条件参数的优化、抗干扰能力以及对天然水样的回收率,并分别进行了水样的测定。     

痕量铅的在线SHA离子交换预浓度流动注射原子吸收测定

采用羟基磷灰石微型柱的流动注射系统与火焰原子吸收光谱联结对工业废水中铅进行预浓集测定。在进样时，被分析物沉积在羟基磷灰石微型柱上，并通过注射半胱氨酸（碱性条件下）予以洗脱。该方法成功地应用于工业废水的分析。通过回收实验，标准物质分析等方法评价了准确度。４ｍｌ样品体积的检测限：为４μｇ／Ｌ（４ｍＬ／ｍｉｎ），进样时间１ｍｉｎ，２μｇ／ｍＬ和０．２μｇ／ｍＬ含量测定的相对标准偏差分别为１．５％和２．２     

氨基乙酸纤维柱分离富集-ICP-AES测定海水中痕量钼和钒

制备了微柱填充物－氨基乙酸纤维滤纸片，在ｐＨ３．７±０．１条件下同时分离和富集了海水中μｇ／Ｌ级的钼和钒，并采用电感耦合等离子体原子发射光谱法测定。钼和钒的富集倍数为９５．７，回收率为９２％～１０４％和９８％～１１２％，４次测定的相对标准偏差分别为８．２％和４．９％。     

流动注射在线阴离子树脂预富集火焰原子吸收测定痕量铜

研究了以阴离子交换树脂作吸附剂的流动注射在线微柱预富集火焰原子吸收测定铜的新方法。在最佳条件下富集１５０ｓ，富集２３倍，检出限０．２μｇ／Ｌ，ＲＳＤ为１．６％，分析速度２０次／ｈ。天然水样中可能存在的离子不干扰铜的测定。所建立的方法已用于水样中痕量铜的测定。     

在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收法测定水中痕量铅

应用高效的在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收系统直接测定水呈痕量铅。实验用内装２００ｍｇＡｍｂｅｒｌｉｔｅＸＡＤ－４键合的５－磺酸－８羟基喹啉螯合树脂的锥形柱,在ＰＨ９条件下样品流速为８．０ｍＬ／ｍｉｎ,９０ｓ采样,用０．５ｍｏｌ／Ｌ Ｈｃｌ洗脱,在分析速度为３０样／ｈ,获得３６倍的富集,经石英缝管增敏,灵敏度提高达１１５倍,线性范围为０－２００μｇ／Ｌ,检出限为１μｇ／Ｌ。铅含量水平５０μｇ／Ｌ的水样连续测定１１次的相对标准偏差２．５％,可直接测定水体中μｇ／Ｌ级的铅。     

在线流动注射-巯基棉分离富集-ICP-AES 测定粮食中铜、镉、铅的研究

研究了巯基棉对待测元素Ｃｕ、Ｃｄ、Ｐｂ的预富集性能,并与改进的流动注射法（双流路）相结合,建立了一套新型、高效的在线流动注射－巯基棉分离富集－ＩＣＰ－ＡＥＳ分析体系,提高了分析方法的频率和灵敏度。Ｃｕ、Ｃｄ、Ｐｂ各元素的检出限分别为０．７μｇ／Ｌ、０．５μｇ／Ｌ和２．９μｇ／Ｌ。１０次的相对标准偏差分别为１．７１％、２．９４％和４．４９％。回收率为８７．８％～１０２．４％。     

流动注射—阳离子交换预富集—ICP—AES法在线分析磷矿中钙,镁,铝,铁 …

用７３２型强酸性阳离子交换树脂分离富集,并与改进的流动注射（双流路）相结合,建立了新型、高效的流动注射－阳离子交换预富集－ＩＣＰ－ＡＥＳ在线分析体系。研究了酸度、流速、淋洗剂浓度等的选择、共存离子的干扰情况并应用于矿样的分析。Ｃａ,Ｍｇ,Ａｌ,Ｆｅ各元素的检出限分别为０．９μｇ／Ｌ,０．６μｇ／Ｌ,５．５μｇ／Ｌ,１．４μ／Ｌ;１０次测量的相对标准偏差分别为３．４４％,１．５３％,１．６０％,２．     

活性炭微柱在线流动注射预富集-火焰原子吸收快速顺序测定铜、钴、镍、镉、铅的研究

采用双柱富集的流动注射在线预富集系统与220FS顺序多元素原子吸收分光光度计联用，使用圆锥型活性炭微柱为预富集柱，在pH4～5．5范围内，以吡咯啶二硫代氨基甲酸铵(APDC)为络合剂，6mol／L HNO3为洗脱剂，实现了Cu、Co、Ni、Cd、Pb5种元素的快速顺序测定。该体系对以上5种元素的富集倍数为9．8～15．5之间，34s富集的检出限(3σ)Cu为1．81，Co为3．10，Ni为1．66，Cd为0．28，Pb为4．90μg/L；相对标准偏差Cu 1．13％；Co1．24％；Ni2．26％；Cd0．95％；Pb1．77％。     

氢化物发生电感耦合等离子体原子发射光谱法同时测定水和生物样品中…

研究了一种小型同心氢化物发生配置一个气液分离器后与多道ＩＣＰ－ＡＥＳ联用，同时测定水和生物样品中砷、铋、锑、硒的方法。检出限为砷０．４μｇ／Ｌ，铋０．５μｇ／Ｌ，锑１．４μｇ／Ｌ，硒０．５μｇ／Ｌ，相对标准偏差为砷２．７％，铋１．５％，锑２．７％，硒１．９％。用本法测定美国和国家标准物质中的氢化元素，结果满意。     

从物质本原到干水:水的概念的发展史

在古代哲学中,水被视为一种物质本原。17世纪化学学科形成后,水被定义成一种化学元素。18世纪的化学革命中,水被发现是氢氧化合物。19世纪原子分子论的创立,使水的概念得到微观表征。至20世纪,重水的发现和干水的发明使水的概念有了新的发展。总之,水的概念的发展史,反映了化学思想的发展和科学技术的进步,对化学研究和化学教育均有重要的启示。     

A model study on the mechanism and kinetics for the dissociation of water anion

Quantum chemical computations using both density functional theory (B3LYP functional) and wavefunction (MP2 and CCSD(T)) methods, with the 6-311++G(3df,2p) and aug-cc-pVnZ (n = D,T,Q) basis sets, in conjunction with a polarizable continuum model (PCM) method for treating structures in solution, were carried out to look again at a series of small negatively charged water species [(H₂O)_n]^•–. For each size n of [(H₂O)_n]^•– in aqueous solution with n = 2, 3, and 4, two distinct structural motifs can be identified: a classical water radical anion formed by hydrogen bonds and a molecular pincer in which the excess electron is directly interacting with H atoms. In aqueous solution, both motifs have comparable energy content and likely coexist and compete for the ground state. Some water anion isomers can dissociate when interaction with a water molecule, [(H₂O)_n]^•– + H₂O → H^•(H₂O)_m + OH^–(H₂O)_n–m, through successive hydrogen transfers with moderate energy barriers. This reaction can also be regarded as a water-splitting process in which the H transfers involved take place mainly within a water trimer, whereas other water molecules tend to stabilize transition structures through microsolvation rather than direct participation. Calculated absolute rate constants for the reversed reaction H^•(H₂O)₂ + OH^–(H₂O)₂ → [(H₂O)₄]^•־ + H₂O with both H and D isotopes agree well with the experimentally evaluated counterpart and lend a kinetic support for the involvement of a tetramer unit.     

多金属氧酸盐催化的水氧化研究进展

氢气以其清洁无污染、燃烧值高等优点成为未来最具潜力的可再生能源之一,而清洁生产氢气的最佳选择之一即为裂解水. 利用太阳能模拟光合作用实现水的全分解产生氢气和氧气是目前最为理想的能源转化方式,并且已经引起了众多研究者的关注. 水分解的半反应之一--水氧化反应由于其过程复杂,一直是制约水分解的瓶颈. 所以寻找高效、稳定的水氧化催化剂便成为了突破该瓶颈的关键. 多金属氧酸盐是一类以前过渡金属氧簇为基本单元形成的多金属氧簇化合物. 由于多金属氧酸盐在物理、化学性质方面具有无法比拟的特性,使得其在催化、药物、纳米科技和材料科学等方面已被广泛地应用. 多金属氧酸盐的全无机配体可很好地抵御水氧化反应的强氧化性环境,故将其作为水氧化催化剂越来越引起研究者们的注意,并且已有多种多金属氧酸盐被设计为水氧化催化剂. 本文详细介绍了各种不同过渡金属取代的多金属氧酸盐水氧化催化剂的研究进展.     

电解离子水及其生成器

本文介绍了电解离子水的制备原理和应用。原水经电解后，阳极室生成酸性离子水，阴极室生成碱性离子水。酸性离子水具有杀菌消毒作用，碱性离子水具有保健作用。同时，简要介绍了离子水生成器的研究进展。     

Determination of differences in free and bound water contents of beef muscle by DSC under various freezing conditions

The differences in bound water content of beef semimembranous muscle samples obtained from previously chilled (24 h at +4°C) middle-aged beef carcasses were determined by the use of DSC. Initially, samples obtained from fresh, unprocessed meat were frozen at –40, –50 or –65°C to determine their melting peaks for freezable water (free water) content with the use of DSC. The samples were then subjected to an environment with an ambient temperature of –30, –35, –40 or –45°C, with no air circulation, or with an air circulation speed of 2 m s^–1, until a thermal core temperature of –18°C was attained; this was followed by thawing the samples until a thermal core temperature of 0°C was reached. This process was followed by subjecting the samples to the ambient temperatures mentioned above, to accomplish complete freezing and thawing of the samples, with DSC, and thereby determination of the freezable water contents, which were then used to determine the peaks of melting. The calculated peak areas were divided by the latent heat of melting for pure water, to determine the freezable water contents of the samples. The percentage freezable water content of each sample was determined by dividing its freezable water content by its total water content; and the bound water content of each sample was determined by subtracting the percentage free water content from the total. In view of the fact that the free water content of a sample is completely in the frozen phase at temperatures of –40°C and below, the calculations of free and bound water contents of the samples were based on the averages of values obtained at three different temperatures.     

Determination of freezable water content of beef semimembranous muscle DSC study

The freezable water contents of samples obtained from previously chilled semimembranous muscle of middle-aged beef carcasses after a 24 h cooling period a room at in 5±1C were determined by differential scanning calorimetry (DSC) at –5, –10, –15, –20, –30, –40, –50 and –65C. This was accomplished by freezing the samples at the above-mentioned temperatures, followed by thawing to 35C, and measuring the melting peaks of freezable water. The areas of these peaks were determined by using the peak integration method programs through a computer linked to the DSC, and they were then used to determine the latent heat of melting (H _m) in kJ kg^–1 at each freezing temperature. The resultant latent heat of melting per sample was divided by the latent heat for pure water to determine the amount of freezable water present in these samples. This amount of freezable water was divided by the total water content of the meat sample to determine the percentage of freezable water in the sample. The percentage of freezable water was subtracted from 100 to determine the percentage of bound water present in the sample.     

Analysis of Fischer-Tropsch by-product waters by gas chromatography

This paper describes a quantitative technique for the determination of organic constituents in Fischer-Tropsch by-product waters. Temperature-programmed gas chromatography on derivatized bonded polar capillary columns provides the required separation that permits reliable quantitation of individual compounds. A preliminary combined gas chromatographic–mass spectrometric survey to identify the components present in Fischer-Tropsch by-product waters is presented. The elution order of 58 identified components is tabulated. Components identified in a typical Fischer-Tropsch by-product water include C₁–C₉ linear and branched alcohols, C₃? C₈ ketones, C₂? C₆ carboxylic acids, and C₂? C₄ linear aldehydes.     

Interaction of water with the regenerated cellulose membrane studied by DSC

One to three endothermal peaks atributted to melting of bulk and interfacial water were observed by DSC in the regenerated cellulose — water system. The profiles of thermal effects depend on water content, time of conditioning, film pretreatment and the conditions applied during the preceding freezing-thawing cycles. The occurrence might be deduced of melting-crystallisation processes. A large amount of non-freezable strongly bounded water was also detected. Although cellulose absorbs water quickly after immersion, the structural changes consisting on ordering of polymer fraction occur during further conditioning due to increase in strength of water binding. Using the membranes in the separation module at 90°C causes weakening of these bonds. Differences between interaction of particular cellulose films with water can be detected during the first, the second and the third heating. This revised version was published online in July 2006 with corrections to the Cover Date.     

Water sorption and permeation in chitosan films: Relation between gas permeability and relative humidity

The water sorption of chitosan has been studied at 20 °C. Water transport is governed by a Fickian process for relative humidities lower than 0.4, and in that range of partial pressures, the diffusion coefficient is concentration‐dependent. At a higher activity, anomalous diffusion is observed. The sorption isotherm is well described by the Guggenheim‐Anderson‐de Boer (GAB) model, and the clustering phenomenon observed at high relative pressures can be studied with the parameters of this model. The water permeability coefficient greatly increases with the relative pressure, and the water plasticization effect leads to a loss of the gas barrier properties under wet conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3114–3127, 2001