线性变位极谱法研究 XIV: 配位吸附准可逆波电化学参数的测定

本文讨论配位吸附准可逆波测定标准电极反应速率常数(kα)和转移系数(α)的理论与方法, 实验结果证实, 方法简便, 结果正确。     

单扫示波极谱法连续测定水样中锑和锡

在pH 2.1的H_2SO_4-NaOAc介质中,有微量Se(Ⅳ)存在时,Sb(Ⅱ)或Sn(Ⅳ)—草酸铵—α,α′-联吡啶络合物产生灵敏的络合吸附催化波。锑和锡浓度分别在0.5～200ng·ml~(-1)和0.8～250ng·ml~(-1)范围内与峰高呈线性关系。锑和锡的检出限分别为0.2ng·ml~(-1)和0.4ng·ml~(-1)。方法用于水样中痕量锑、锡的连续测定,结果满意。     

镉离子在H2SO4溶液中极谱行为的研究

本文研究了在没有动物胶的0.5M H_2SO_4溶液中镉离子的极谱行为,得到了如下的结果:(1)在0.050～20.0mM CdSO_4 0.5M H_2SO_4的十种溶液中测得的电流-电位曲线都有良好的波形、恒定的极限扩散电流和易于确定的半波电位.这些曲线上都没有极谱极大出现;其极限扩散电流(波高)与镉离子的浓度成正比.在镉离子低浓度(0.050～0.20mM)时,半波电位保持不变,在镉离子高浓度(1.00～20.0mM)时,也仅有很小的变化.故镉离子在0.5MH_2SO_4,溶液中的电流-电位曲线可供定量和定性测定之用.(2)镉离子在低浓度时的极谱波是一种可逆波.(3)前人在H_2SO_4溶液中研究镉离子时之所以没有能得到令人满意的极谱行为的原因是他们在H_2SO4溶液中添加了动物胶的缘故.(4)作者从得到的波形良好的电流-电位曲线上,测定了25±0.2℃时镉离子在0.5M H_2SO_4溶液中的扩散电流常数、半波电位和电极反应中得失的电子数.结果如下: i_d/cm~(2/3)t~(1/6)=3.97μA/mM·mg~(2/3)·s~(-1/2) E_(1/2)=-1.011V(0.5M硫酸亚汞电极)=-0.559V(饱和甘汞电极) n=2 这些数据比Lingane的数据,扩散电流常数2.6μA/mM·mg~(2/3)·s~(-1/2)和半波电位-0.59V(饱和甘汞电极)],要合理些.     

催化极谱法测定痕量铬的研究

本文研究了含氨介质中铬(Ⅲ、Ⅵ)-α,α’-联吡啶-亚硝酸钠体系的电化学行为。建立了测定痕最铬的方法。测定铬的范围为0.004～0.028μg/mL和0.04～0.23μg/mL,检测下限为2.0×10~(-3)μg/mL,用以测定生物样品中良量铬,变异系数为0.8%。     

GC-MS联用技术结合化学计量学方法分析厚朴叶挥发油成分

利用水蒸气蒸馏法提取湖南产厚朴叶的挥发油成分,采用GC-MS联用技术结合化学计量学方法(直观推导式演进特征投影法和选择性离子法)进行分析,同时结合程序升温保留指数辅助定性。结果共鉴定出54种化合物,占挥发油总量的84.95%。主要化学成分为α-、β-和γ-桉油醇,含量分别为13.10%、28.21%和14.67%。此外,含量较高的化合物还有α-蒎烯(2.96%)、芳樟醇(1.71%)、丹皮酚(1.88%)、石竹烯(2.04%)、佛术烯(3.60%)、α-瑟林烯(3.84%)和[1AR-(1Aα,4α,4Aβ,7Bα)]-1A,2,3,4,4A,5,6,7B-八氢化-1,1,4,7-四甲基-1H-环丙烯并[E]奥(1.34%)。研究表明,将化学计量学方法用于中药挥发油成分的分析可提高定性分析的准确性。所得结果可为厚朴药植物资源的开发利用提供依据。     

指示离子Cd2+测定维生素B1的方波极谱法研究

根据Cd2+对维生素B1(VB1)的指示作用,建立了用方波极谱法测定VB1的新方法.在氨-氯化铵缓冲溶液中,VB1不出峰,加入Cd2+后在-0.856 V(vs.SCE)处出现1个固定还原峰,并在-0.360 V(vs.SCE)处可见1个峰高与VB1浓度呈正比的还原峰.依据该还原峰峰高的变化规律可测定VB1的含量.VB1在1.35μg/mL~1.35 mg/mL的范围内有良好的线性关系,检出限可达0.13μg/mL,r为0.999 7.平均加样回收率为99.6%(n=9),RSD为0.9%.利用方法测定营养胶囊中VB1的含量,效果理想,可作为VB1含量的测定方法.     

α-球蛋白与稀土金属离子钆(Ⅲ)的配位作用

采用固定顺磁金属离子浓度,逐渐改变α-球蛋白浓度,测定溶剂水质子弛豫时间变化的方法,研究了稀土离子钆(Ⅲ)与人血α-球蛋白的配位作用.研究结果表明,α-球蛋白中有3个钆(Ⅲ)离子的结合部位,其配合物的离解常数K_d=2.5×10~(-4)(mol/L)。     

抗坏血酸间接示波极谱法测定

抗坏血酸的示波极谱法测定未见报道,作者在工作中发现α,α′-联吡啶与Fe(Ⅲ)在乙酸盐缓冲液中有一良好的络合吸附波,当有抗坏血酸存在时Fe(Ⅲ)被还原为Fe(Ⅱ),此波降低并显红色,即Fe(Ⅱ)与α,α′-联吡啶作田生成红色络离子(可比色测定)。抗坏血酸量在0～120μg/10ml范围内与其极谱波高呈负相关,r=-0.9983,以间接测定抗坏血酸。本法最低检出限10μg/10ml,精密度准确度良好,操作简便快速,宜推广应用。     

基于质谱特征碎裂片段的乳制品中真菌毒素非定向筛查方法研究

该研究采用超高效液相色谱-四极杆-静电场轨道离子阱质谱的数据依赖型扫描,对38种典型真菌毒素标准物质化合物色谱信息、分子离子和二级碎裂片段进行采集,建立了真菌毒素标准数据库并完成了裂解途径解析与特征碎裂片段筛选;采用数据非依赖扫描,获取可追溯的样品质谱信息,构建了乳制品中真菌毒素的非定向筛查方法。该方法确定限(CCα)和检测容量(CCβ)分别为0.01～0.36μg/kg与0.03～0.57μg/kg,回收率为81.9%～111%,相对标准偏差(RSD)为1.1%～6.1%。将所建立的方法用于40个批次巴氏杀菌乳、超高温瞬时灭菌乳、含乳饮料及婴幼儿配方乳粉中真菌毒素的筛查,结果显示该方法快速、简便,可实现乳制品中真菌毒素准确定性和定量。     

超微Ni(OH)2纳米粒子的合成及其对Li+的超高吸附性能

在葡萄糖水溶液中合成得到平均粒径为5 nm的α-Ni(OH)2超微纳米粒子。研究结果发现,在水溶液中葡萄糖浓度能够控制α-Ni(OH)2纳米粒子粒径的大小,我们对其中的原理进行了剖析。当没有葡萄糖存在时,合成得到的Ni(OH)2晶型为β型,且颗粒粒径尺寸分布为微米级别。另外,研究发现α-Ni(OH)2超微纳米粒子室温下对中性水溶液中Li^+具有较强的吸附性能,且这种吸附性能随粒径的减小而剧烈增大;粒径为5 nm的α-Ni(OH)2粒子对Li^+的最大吸附量为214 mg·g^-1(远大于文献报道的有关吸附剂对Li^+的吸附容量),而粒径为1μm的β-Ni(OH)2在相同条件下对Li^+的最大吸附量低于30 mg·g^-1。计算分析表明,Li^+在α-Ni(OH)2纳米粒子表面吸附满足Freundlich方程,符合层层吸附模型。     

铊(I)离子选择电极动力学分析法测定超痕量铁

Fe(II) induces the reaction between Tl3+ and H2O2. The rate of reaction is linearly proportional to the concentration of Fe2+ in the range 2.5 ?10-9-2.5 ?10-8 mol dm-3 (20? and 5 ?10-9-5 ?10-8 mol dm-3 (15?. The standard deviation is less than 0.071 ?10-8. A 1000-fold excess of Zn2+, Cd2+, Mg2+, Ni2+, Pb2+, Ba2+, Ca2+, Li+, Na+, Ag+, NO3-, SO42-, AcO-, HPO42-, 500-fold excess of Al3+, Fe3+, Co2+, Hg2+ and 100-fold excess of Ti4+, Cr3+, Cu2+, Br-, Cl- can be tolerated, but reducing agents such as (NH2)2SO4, NH2OH.HCl interfered. This kinetic method was applied to determine Fe(II) in standard zinc sample and fountain water, with satisfactory results.     

Luminol-K2S2O8体系中金属离子化学发光行为的研究

报导了在自行设计的流动注射式化学发光分析仪上,对Luminal-K2S2O8体系中32种金属离子的化学发光行为的系统研究.确定了对金属离子的最优测定条件以及大多数金属离子的检出极限和线性范围.     

萃取体系二相界面荷电物质传输的电化学研究 I: 邻菲咯啉体系中Ni(II)、Co(II)相转移的电化学性质

用线性电流扫描极谱、恒电流单阶跃计时电位法及等电流双阶跃计时电位法, 研究了Ni(II)、Co(II)-邻菲咯啉(phen)体系在1,2-二氯乙烷(DCE)/水界面相转移的电化学行为。同时, 研究了相转移过程的机理。结果表明, 电解前, Phen与Ni(II)或Co(II)同时在水相时, Ni(II)、Co(II)行为类同; 若电解前Phen在有机相时, Ni(II)、Co(II)的行为截然不同, 原因在于两者与Phen配位反应的动力学的差异。     

Metal-Loaded Sorbents for Selective On-Line Sample Handling and Trace Enrichment in Liquid Chromatography

Abstract

Three different commercially available stationary phases containing a thiol, an 8-hydroxyquinoline (oxine), and a 2-amino-1-cyclopentene-1-dithiocarboxylic acid (ACDA) functional group, were loaded with mercury (Hg(II)), platinum (Pt(IV)) and silver (Ag(I)) ions. The phases were packed in small precolumns and evaluated for their potential towards the selective on-line sample handling and trace enrichment of three model systems in liquid chromatography. The thiol 2-mercaptobenzimidazole was used to study trace enrichment on Hg(II)-loaded phases; the herbicide buturon, which contains an ethynic bond, was selected to study trace enrichment on Ag(I)-loaded phases. The on-line filter effect of Pt(IV)-loaded phases was investigated with 4-chloroaniline as a model compound.

The results indicate that the Hg(II)-ACDA phase should be preferred for the trace enrichment of thiols, a Pt(IV)-ACDA or a Pt(IV)-thiol phase for the anilines and the Ag(I)-oxine phase for the trace enrichment of ethynic compounds.

As environmental application, the selective on-line trace enrichment of buturon from river water samples, on a precolumn packed with Ag(I)-oxine, is shown.     

Electrochemical oxidation of 8-hydroxyquinoline and selective determination of tin(II) at solid electrodes

The electrochemical oxidation of 8-hydroxyquinoline and several structurally related molecules has been investigated by cyclic voltammetry at solid electrodes (GCE, CPE, Pt) as a function of pH in aqueous acetate media. Oxine showed one irreversible oxidation peak whose magnitude decreased in the presence of cations readily complexed by oxine and with concomitent formation of a new oxidation peak at more positive potentials. Tin(II ) was found to exhibit a distinct behavior as its oxidation was catalyzed by the presence of oxine in the analyzed solution. The tin(II )-oxine oxidation peak was found to be linearly related to inorganic tin(II ) concentration allowing its quantitative determination at micromolar levels.     

Theoretical and experimental approach to spectrofluorometric extractive titrations

Spectrofluorometric extractive titration (SFET) is a sensitive method for determining trace amounts of certain metals. This technique combines titration, extraction and fluorometry and is more sensitive than any of these individual techniques. A theoretical treatment is derived and is compared favorably to an experimental procedure using Ga(III) and Al(III) as metals being titrated by 8-hydroxyquinoline(oxine). A sensitivity value for the experimental SFET is derived and calculated for the Ga(III) and Al(III)-oxine systems.     

8-hydroxyquinoline based neutral tripodal ionophore as a copper (II) selective electrode and the effect of remote substitutents on electrode properties

New PVC membrane ion selective electrodes based on 1,3,5-Tris(8-quinolinoxymethyl)-2,4,6-trimethylbenzene (MO8HQ) are reported. The basic sensing material belongs to the group of tripodal ionophores. Also their derivatives prepared by placing suitable substitutents at fifth position of 8-oxine moiety, i.e, 1,3,5-Tris(5-chloro-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5CHQ), 1,3,5-Tris(5-benzoyl-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5BHQ) and 1,3,5-Tris[(5-phenylhydroxymethylene)-8-quinolinoxymethyl]-2,4,6-trimethylbenzene (HYD-8HQ) ionophores have also been used to make copper-selective membrane electrodes. Among all the four electrodes, MO8HQ and HYD-8HQ ionophores based electrodes show excellent response towards Cu (II) ions. The electrodes having composition 33% PVC, 4% MO8HQ and 63% dibutyl phthalate (DBP) and 33% PVC, 6% HYD-8HQ, 63% dibutyl phthalate (DBP) exhibit a good Nernstian response to Cu (II) ions in the range of 1.0 × 10⁻⁶ to 1 × 10⁻¹ M. The electrode shows a reasonably fast response time of 15 s. The effect of pH and electrode response is also reported. It shows good selectivity for Cu (II) ions in comparison to heavy metal ions, transition metal ions and for alkali and alkaline earth metal ions. The electrode response and selectivity remains unchanged for at least 5 months. The electrode can be used as an indicator electrode in the potentiometric titration of Cu (II) ions with EDTA.     

钴(II)-丁二酮肟-亚硝酸盐体系极谱催化波的机理研究

在氨性底液(PH8)中, 钴(II)-丁二酮肟(DMG)-亚硝酸盐体系产生高灵敏的极谱催化波. 利用吸附伏安法, 测定下限可达1×10^-^1^1mol.dm^-^3Co. 我们用多种电化学方法和紫外可见分光光度法证明, 吸附在汞电极表面的[NH4]2[Co(DMG)2(NO2)2]是有很高电活性的混配化合物, 在复杂的电还原过程中, 不仅Co(II)和DMG被催化还原, 而且NO2^-也被催化还原, 从而产生很大的催化电流, 本文再一次证明, “活性钴"在催化波的形成过程中起着重要的作用.     

氯冉酸阴离子桥联双核铜(II)配合物的合成和磁性

本文合成了五种以氯冉酸二价阴离子为桥联配体的Cu(II)单核([CuLCA].H~2O)和双核([Cu~2L~2CA](ClO~4)~2配合物:[Ca(phen)CA].H~2O(1),[Cu~2(phen)~2CA](ClO~4)~2(2),[Cu(NO~2-phen)CA].H~2O(3),[Cu~2(NO~2-phen)~2CA](ClO~4)~2(4)和[Cu~2(bpy)~2CA](ClO~4)~2(5)。经元素分析、红外、固体紫外、顺磁共振、磁化率及变温磁化率的测定对上述各配合物进行了表征。配合物1,3可能是通过水分子中的氢键将两个[CuLCA]单元联接而缔合的假双聚体。配合物2,4,5则由阳[Cu~2L~2CA]^2^+阳离子和弱配位的ClO~4^-阴离子所组成。双核配合物中Cu(II)离子的几何构型可能为畸变的四方锥。所有五种配合物均难溶于水及常见有机溶剂。上述配合物的室温ESR谱呈现ΔM~s=2的从单重态到三重态的半场跃迁。配合物2,5的变温磁化率(4-300K)已测得,利用Heisenberg模型确定交换参数J值为-29.2和-25.7cm^-^1。表明在此类桥联配合物中,两核间存在着反铁磁性交换耦合作用。