大体积固相萃取-气相色谱法测定海水中10种多氯联苯

采用大体积固相萃取-气相色谱法测定海水中10种多氯联苯的含量。海水样品采用大体积样品采样器与聚苯乙烯/二乙烯基苯固相萃取柱进行萃取。萃取流量为5.0mL·min-1,丙酮作为洗脱剂。用Agilent HP-5石英毛细管色谱柱(30m×0.32mm,0.25μm)分离,微池电子捕获检测器检测。10种多氯联苯的质量浓度均在10.0μg·L-1以内与其峰面积呈线性关系,方法的检出限(3S/N)在0.002 3~0.012μg·L-1之间。测定值的相对标准偏差(n=7)在0.9%~1.3%之间,在0.5,1.5,4.0μg·L-1等3个浓度水平进行加标回收试验,回收率在80.7%~127%之间。     

高效液相色谱法测定奶粉和液态奶中的三聚氰胺

建立了奶粉和液态奶中三聚氰胺的高效液相色谱（HPLC）检测方法。经阳离子交换固相萃取柱净化后的样品采用HPLC测定。优化的色谱条件：C18柱（4.6 mm ×200 mm,5 μm）,流动相为乙腈-0.01 mol/L庚烷磺酸钠（pH 3.3）（体积比为10∶90）,流速为1.0 mL/min,检测波长为236 nm,柱温为40 ℃,进样量为20 μL。方法的线性范围为1~500 mg/L,检出限为0.2 mg/kg （S/N=3）,定量限为1 mg/kg （S/N=15）,回收率为81.4%~83.7%,相对标准偏差为3.3%~8.5%（n=6）。     

超高效液相色谱-串联质谱法同时检测环境水体中27种EDCs

应用超高效液相色谱-串联质谱法(UPLC-MS/MS)建立了环境水体中27种典型EDCs的分析方法。通过对固相萃取柱、淋洗液、流动相等的优化,确定以Oasis HLB固相萃取柱、二氯甲烷/丙酮(85:15,V/V)为淋洗液、0.1%氨水/乙腈(7:3,V/V)为流动相做水样预处理。在最优条件下,目标物在水中回收率约85.1%~119.8%,相对标准偏差(RSDs)在5.1%~11%,线性范围均在0.1~1000μg/L,各目标物标准品在UPLC-M S/M S系统中线性相关导致(R2)均大于0.997,检出限(S/N=3)为0.15~0.65μg/L,定量限(S/N=10)为0.20~0.81μg/L。该方法可适用于环境水中27种EDCs的同时检测。     

固相萃取-气相色谱法测定鱼塘投毒案件水样中硫丹的含量

采用固相萃取-气相色谱法测定鱼塘投毒案件水样中硫丹的含量。取自鱼塘的水样调至pH 4,经CNWBOND LC-C18固相萃取柱分离,用三氯甲烷作为洗脱溶剂,所得提取液用CP-SIL8毛细管色谱柱分离,电子捕获检测器检测。α-硫丹和β-硫丹的峰面积与其质量浓度在0.05~5μg·L-1相同的范围内呈线性关系,方法的检出限(3S/N)均为0.01μg·L-1。加标回收率在91.1%~95.8%之间,测定值的相对标准偏差(n=6)小于1%。     

果实类中药材中20种有机磷农药残留量的同时测定

建立了果实类中药材中多种有机磷农药残留同时测定的方法,并对影响提取、净化、检测效率的因素进行优化。样品用乙酸乙酯提取,凝胶渗透色谱收集9~15 min流分,ENVI-Carb固相萃取柱净化,DB-1701毛细管色谱柱分离,火焰光度检测器检测,外标法定量。在优化条件下,20种有机磷农药在0.01~2.0mg/L范围内具有良好的线性关系,相关系数为0.996 6~0.999 5,检出限(S/N=3)为0.66~5.78μg/kg。3个加标水平下的平均回收率为80.2%~109.9%,相对标准偏差为2.3%~13%。该方法操作简便、准确、净化效果好,可满足果实类中药材中多种有机磷农药残留的同时测定要求。     

HPLC-MS/MS正负离子切换测定农田土壤中的2,4-二氯苯氧乙酸、敌稗和二嗪磷

利用串联质谱正负离子切换模式功能,建立了一种能快速同时检测农田土壤中2,4-二氯苯氧乙酸,敌稗和二嗪磷残留的液相色谱-串联质谱(HPLCM S/M S)分析方法。样品以加速溶剂萃取,Supelclean ENVI-18固相萃取柱净化,多反应监测(MRM)正负离子切换电喷雾模式进行分析。色谱柱为Luna C18柱(150 mm×2.0 mm,3μm),流动相为梯度变化的5 mmol/L甲酸铵甲醇溶液和5 mmol/L甲酸铵水溶液。方法检出限(S/N≥3)介于0.94~8.35 ng/L,相关系数≥0.999;在1.0~10.0μg/kg添加水平内,平均加标回收率介于73.8%~106.9%之间,RSD介于5.8%~11%。利用该方法对某地区农田表土的筛查发现该地区存在二嗪磷使用历史,但污染程度较轻。     

在线固相萃取-离子色谱法测定4种芳环磺酸盐中的硫酸根离子

建立一种在线固相萃取-离子色谱测定4种芳环磺酸盐中硫酸根离子含量的新方法。将自装填的多孔石墨化碳固相萃取柱应用于离子色谱系统,对样品进行在线前处理。样品经过多孔石墨化碳固相萃取柱基体消除后进入收集环,通过阀切换方式使待测硫酸根离子转入阴离子分析柱和检测系统。固相萃取流路用1.5 mmol/L碳酸钠以0.8 mL/min的流速对基体在线富集,进样量为20μL,分析柱为SH-AC-3(250 mm×4.0 mm)+SH-AG-3(50 mm×4.0 mm)色谱柱,柱温为35℃,在6 mmol/L碳酸钠-4 mmol/L碳酸氢钠条件下等度洗脱,流速为0.8 mL/min。结果表明:硫酸根离子在0.50~20.00 mg/L范围内呈良好的线性关系,线性相关系数为0.998 3,保留时间、峰高和峰面积的相对标准偏差均在0.28%~2.86%之间,方法检出限为0.010 6 mg/L,回收率为91.01%~109.3%,具有良好的线性关系和重复性。整个在线分析过程在25 min之内完成。该方法进样量少、快速、高效。     

分子印迹固相萃取-高效液相色谱法检测水产品中的孔雀石绿

建立了分子印迹固相萃取-高效液相色谱法测定水产品中孔雀石绿(MG)残留。采用沉淀法合成对MG具有高选择性的分子印迹聚合物,并以其做为吸附材料,制备固相萃取柱。在固相萃取优化条件下,结合高效液相色谱法对7种水产品中MG富集效果进行了考察。结果表明,MG的检出限(S/N=3)为2.0×10~(-3)μg/mL,定量限(S/N=10)为6.7×10~(-3)μg/mL,加标回收率为81.2%~109.7%。与碱性Al2O3柱对比,可以有效的去除基质效应,对水产品中MG有很好的分离富集效果。     

固相萃取-气相色谱-质谱法测定果蔬中36种农药残留

采用气相色谱-质谱法测定果蔬中36种农药残留。果蔬试样经丙酮-水匀质,二氯甲烷液-液萃取,然后过石墨化炭黑固相萃取柱净化,浓缩定容后在DB-5毛细管色谱柱(30 m×0.25 mm,0.25μm)分离,质谱中选择电喷雾离子源-选择离子监测模式。36种农药残留的质量浓度在一定范围内与其峰面积呈线性关系,检出限(3S/N)均不高于15μg·kg-1。加标回收率在75.3%~115%之间,测定值的相对标准偏差(n=6)在0.6%~7.8%之间。     

混合型固相萃取/超高压液相色谱法测定废水中苯胺类化合物

通过对色谱分析、固相萃取和氮吹浓缩条件的优化研究,建立了混合型固相萃取/超高压液相色谱法测定废水中7种苯胺类化合物的方法。200 mL水样以5 mL/min通过MCX混合型固相萃取小柱,经4 mL2%甲酸水溶液锁定,4 mL 25%甲醇水溶液净化,8 mL 2%氨水甲醇溶液洗脱后,洗脱液经50℃氮吹浓缩至1 mL,微孔滤膜(0.22μm,尼龙)过滤后,采用BEH C18色谱柱(2.1 mm×50 mm,1.7μm)进行分离,以甲醇-乙酸铵溶液梯度洗脱,250 nm检测。7种苯胺类化合物可在6.5 min内实现基线分离,在0.1~5.0 mg/L范围内线性关系良好,相关系数均大于0.999,方法检出限(S/N=3)为0.10~0.50μg/L,定量下限(S/N=10)为0.33~1.67μg/L。在0.2μg和1.0μg加标水平下,回收率分别为52%~101%和54%~96%,RSDs分别为2.2%~11.3%和2.5%~9.0%。方法抗干扰能力强、分析速度快、灵敏度高,适用于废水中苯胺类化合物的测定。     

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。     

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.     

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.     

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 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.     

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.     

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