HACH分析仪测定废水中镉

电镀、采矿、冶炼、染料、电池和化学工业等排放的废水中含有重金属镉.镉是一种有害的金属离子,对生物体的影响有累积的作用.快速而准确地测定镉对环境科学、生命科学的研究具有重要意义,因此有很多科学工作者对镉的测定方法进行研究,尤其是用分光光光度法测定镉[1-7].     

纳米钛酸钙粉体的制备及其对水中铅和镉的吸附行为

采用柠檬酸络合溶胶-凝胶法制备了纳米钛酸钙粉体. 以X射线衍射(XRD)、透射电子显微镜(TEM)和傅立叶变换红外光谱(FTIR)对其进行了表征. 考察了该纳米粉体对水中重金属铅和镉的吸附性能, 并以镉离子为例, 系统地研究了吸附热力学和动力学. 结果表明, 该法合成的钛酸钙为钙钛矿结构的纳米粉体, 粒径大小受灼烧温度的影响, 灼烧温度越高, 粉体平均粒径越大, 600 ℃灼烧2 h条件下, 粉体的平均粒径最小, 约为20 nm. 当介质的pH值为4～8时, 钛酸钙对水中的铅和镉具有很强的吸附能力. 其对镉离子的吸附行为符合Langmuir 吸附等温模型和HO准二级动力学方程式, 吸附过程焓变(ΔH)为39.312 kJ•mol－1, 各温度下的自由能变(ΔG)均小于零, 熵变(ΔS)均为正值, 吸附过程的活化能(Ea)为20.359 kJ•mol－1. 该吸附过程是自发的吸热物理过程. 被吸附的铅和镉均可用1 mol•L－1的硝酸完全洗脱回收. 对铅和镉的富集因子均超过200. 将其应用于水中痕量铅和镉的吸附富集和测定, 回收率分别为96.3%～107.2%和93.5%～104.0%, 与石墨炉原子吸收光谱法测定结果一致.     

阻抑褪色动力学光度法测定痕量镉

镉是重要的环境污染物之一.镉的测定方法主要有原子吸收光谱法、吸光光度法等,动力学光度法测定镉的报道较少.作者在试验中发现,在pH3.5的硫脲介质中,痕量镉对溴酸钾氧化甲基红褪色有强烈的阻抑作用.据此研究了动力学条件,建立了动力学光度法测定痕量镉的新方法,并成功地用于水中痕量镉的测定.1 试验部分1.1 主要试剂与仪器镉标准溶液:1mg·ml~(-1),称取CdCl_2·5H_2O0.2432g于50ml烧杯中,加入少量水和浓盐酸2ml,微热溶解后,移入100ml量瓶中,用水稀释定容,摇匀.溴酸钾溶液:0.05mol·L~(-1).甲基红溶液:0.1g·L~(-1)甲酸-氢氧化钠缓冲溶液:pH=3.5,称取氢氧化钠4.5g溶于少量水中,加入甲酸12ml,稀释至200ml.     

微分电位溶出伏安法同时测定甘草中痕量铅和镉

建立了在NH4OAc HOAc介质中,用微分电位溶出伏安法测定中药甘草中痕量铅和镉的方法,利用该法对中药甘草煎煮前后及其煎液中铅和镉的含量进行测定。试验表明,镉和铅分别在-0.66V(vs.SCE)和-0.47V(vs.SCE)电位处形成两个灵敏的二次微分溶出峰;铅在0～0.8mg·L-1,镉在0～0.4mg·L-1范围,峰电流与浓度呈良好的线性关系;铅和镉检出限分别为0.15和0.1μg·L-1,相对标准偏差≤1.39%;铅和镉加标回收率在94%～103%之间。结果表明,该甘草样品中铅和镉含量均低于国家安全标准,甘草煎煮液中铅的浸出率较高,镉的浸出率则较低,方法也适用于其它类似中药。     

湖泊沉积物中镉的测定及环境意义研究

建立了氢化物发生-原子荧光光谱法测定湖泊沉积物中镉的分析方法.优化了沉积物中镉的提取条件和测定条件,研究了Cu元素对测定镉的干扰及消除方法.以武汉市涨渡湖为例,通过对总镉和有效态镉的测定揭示了涨渡湖近百年来镉的各形态垂直分布特征.结果表明:自上世纪50年代以来,涨渡湖沉积物中的总镉由深层到表层呈上升趋势,有效态镉变化不大但其含量维持在较高水平.镉的潜在风险性较大.     

微量进样-火焰原子吸收光谱法测定小白鼠血液中镉

离心分离小白鼠血液中的血红细胞和血清,所得的血红细胞经硝酸和过氧化氢消化处理.结合微量进样系统,进样量为300μL,用火焰原子吸收光谱法测定了小白鼠血液中血红细胞和血清中镉的含量.镉的质量浓度在0.050～0.600 mg·L-1范围内与吸光度呈线性关系,检出限(3s/k)为2.2μg·L-1.加标回收率为97.1%,相对标准偏差(n=6)为3.0%.应用此法测定了饮用0.1 g·L-1硝酸镉溶液15d的小白鼠的血清和血红细胞中镉的含量,试验组的血液中镉含量为对照组的7倍.     

示波极谱法同时测定尿中铅和镉

研究示波极谱法同时测定尿中铅和镉的方法.运用正交试验选择底液的组成为碘化钾-抗坏血酸-浓盐酸-磷酸.用硝酸、高氯酸、盐酸混合酸消化尿样,消化液在酸性介质中,置极谱仪的三电极系统,样品溶液在滴汞电极上产生还原电流,分别于-480 mV和-620 mV处测量铅和镉的峰电流,对尿样中铅和镉进行测定,铅、镉的质量浓度在100 μg·L-1以内与峰电流呈线性关系.铅、镉的相对标准偏差分别为6.91%,6.45%,检出限(3S/N)分别为2.0,1.0 μg·L-1,回收率分别为88.4%～101.4%,83.1%～103.5%.     

镉的纸上层析分离和鉴定

镉及的化合物是一种新的致癌物质,在国内外对它的分析颇有研究,但在分离和富集上存在着一定问题,在分析一些较复杂物质的镉时就遇到了障碍。纸上层析是一种简单易行的分离手段,在镉的分离和鉴定方面很早就有过报导。可是它分离时间长,要求条件严,鉴定不灵敏,没有被人利用。我们使用了用2NHCl饱和的正丁醇作展开剂后,应用了2,2联吡啶亚铁碘化钾作显色剂进行镉的纸上层析试验,认为它分离时间短,效果好,鉴定灵敏,在一般的条件下就可以进行操作,其具体方法如下。 1.分析手续: (1)取含有Cd~(2 )的试液250ml于分液漏斗中,加入10ml氨水,摇匀澄清后分离其沉淀,将清液放入烧杯中加热蒸发浓缩至2—3ml,然后     

双硫腙修饰玻碳电极阳极溶出伏安法测定痕量镉和铅

报道了双硫腙修饰玻碳电极同时测定痕量镉和铅的电分析方法。镉和铅离子通过与电极表面的双硫腙发生螯合作用而富集在电极表面 ,同时在 -1 .2 0V(vs.SCE)还原成零价镉和铅 ,当电极电势从 -1 .2 0V向 -0 .3 0V扫描时 ,被还原的镉和铅从电极表面溶出 ,分别于 -0 .78V和 -0 .4 8V左右形成灵敏的阳极溶出峰。优化了支持电解质及pH值、双硫腙用量、富集电位及时间等实验参数。利用该修饰电极测定镉、铅的线性范围分别为 1 .0×1 0 - 8～ 2 .5× 1 0 - 6 mol L和 5 .0× 1 0 - 9～ 2 .5× 1 0 - 6 mol L。检测限分别为 5 .0× 1 0 - 9mol L和7.0× 1 0 - 1 0 mol L。该法用于实际水样中镉和铅的测定 ,平均回收率分别为 99.3 0 %和 99.5 4 %。     

新试剂用径向基函数网络光度法同时测定微量的镉镍

合成一种新的显色剂(4,4'-二偶氮苯基-2-羧基-重氮氨基偶氮苯,BBDDAB),对镉、镍有灵敏的显色反应,最大摩尔吸光系数分别达到1.90×10～5L·mol-1·cm-1和1.56×10～5 L·mo-1·cm-1.镉镍在最大吸收波长在524和540 nm处线性范围分别为0～0.40μg/mL.和0～0.32μg/mL.尽管两种络合物光谱重叠较严重,但采用分光光度法结合化学计量学中的人工神经网络方法(RBFANN)可实现镉镍的同时测定.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.