硒碳糊电极微分电位溶出法测定铜和铋

建立了掺杂硒碳糊电极同时测定铜和铋的微分电位溶出法。在HCl(0.05mol/L)中,在-0.3V(vs.Ag/AgCl)下,Cu2+和Bi3+电沉积在电极表面,再在溶液中溶解氧的作用下,铜和铋从电极表面溶出,分别于0.30V和0.02V获得灵敏的电位溶出峰。微分电位溶出峰高(dt/dE)与铜和铋的浓度成线性关系,线性范围为5.0×10-9～1.55×10-7mol/L,检出限分别为4.0×10-9和2.5×10-9mol/L(S/N=3)。方法用于实际样品中铜和铋的测定,结果令人满意。     

铕离子掺杂类普鲁士蓝复合汞膜电极的制备及溶出分析特性

在铕离子掺杂类普鲁士蓝(Eu-PB)修饰的玻碳电极表面电沉积汞膜,制备了一种新型化学修饰复合汞膜电极GC/Eu-PB/MFE.研究了修饰层厚度、镀汞方式和汞膜成长过程对复合汞膜形成的影响.以Pb2+和Zn2+为探针离子,对复合汞膜电极和常规玻碳汞膜电极的氢过电位值、表面活性物质的影响、汞膜稳定性和金属离子的溶出伏安行为等进行了对比研究.同时,应用该电极结合示差脉冲阳极溶出伏安法对环境水样中的痕量Pb2+进行了测定.结果表明,Pb2+在该复合汞膜电极上的阳极溶出峰电流与其质量浓度在0.8 ～250 μg/L范围有良好的线性关系(r=0.999 5,n=12),检出限为0.2 μg/L,加标回收率为98% ～102%.用该法对国家铅标准物质溶液对比测定,数据的重复性和准确性均令人满意.     

α-Al2O3纳米粒子对Co-Ni合金异常共沉积电化学行为的影响

为了研究在电化学复合共沉积过程中,惰性纳米粒子和金属离子、电极表面的相互作用,以及由此产生的对合金电化学共沉积行为的影响.本文从两个吸附过程出发: 电解液中的金属离子和H＋在纳米粒子表面的吸附；纳米粒子迁移到阴极表面,在电极表面的吸附.采用Zeta电势和稳态极化以及电化学交流阻抗（EIS）研究了纳米Al2O3粒子和电解液中的金属离子，和电极表面的相互作用,进而分析了纳米粒子对Co2＋和Ni2＋还原沉积的影响规律.通过对阻抗数据的拟合,讨论了Al2O3纳米粒子对等效电路中各物理参数的影响.在H＋和不同金属离子在纳米粒子上发生竞争吸附的基础上,提出了纳米粒子和合金共沉积的可能反应历程.     

基于二次开发平台的阳极溶出伏安仪

建立了一种适合研发电化学仪器的新型二次开发平台, 开发了一系列仪器模块和组件,并利用此平台研制了一种操作方便、成本低廉的微型半自动阳极溶出伏安仪(MASV).仪器采用了20位数模转换器和16位模数转换器, 电流测量范围为 1 pA～20 mA; 支持线形扫描法和微分脉冲伏安法等电化学方法.电解池可原位清洗, 搅拌均匀高效且速度可调; 仪器体积小, 且不需要外接电源, 操作方便.利用MASV进行了一系列阳极溶出实验,获得了Cd2+和Pb2+溶液的标准曲线, 其相关系数均大于0.999, 检出限可达μg/L 数量级,重现性较好.测试了环境水样中的Cd2+和Pb2+的含量.     

壳聚糖修饰电极测定碘的研究

应用共价键合法将壳聚糖修饰在玻碳电极表面,研究了I-在该修饰电极上的微分脉冲阳极溶出伏安特性,并对相关机理进行探讨.实验表明,修饰电极在pH为4.0的0.1mol·L-1KH2PO4溶液中,对I 具有良好的吸附性和选择性,电极响应灵敏.其阳极溶出峰电流在2.0×10-6～2.0×10-3mol·L-1I-浓度范围内呈良好线性关系,检出下限达2.0×10-7mol·L-1.该法应用于食用碘盐中总碘量的测定,取得较好的结果.     

磁流体动力学用于镉的溶出伏安检测

提出了一种基于磁流体动力学效应用于小体积样品中镉的测定的溶出伏安方法。在金属的溶出伏安法测定中,磁场和高浓度的Fe3 的共同作用产生的磁流体动力学效应使得更多的金属离子沉积在电极表面,使金属的溶出峰电流明显提高,极大地提高了测量的灵敏度。在对2mL样品中的Cd测定,磁场强度0.6T,Fe3 浓度为0.12mol/L,富集电位-0.8V,富集时间60s,镉的检出限为3.1×10-9mol/L,线性范围为1×10-8～1×10-6mol/L。本方法灵敏度高、重现性好,可以有效的避免传统的溶出伏安法测定中,由搅拌所产生的较大的背景电流干扰,尤其适用于小体积样品中重金属离子的溶出伏安法分析。     

新型固体汞电极在仪器分析实验中的应用

介绍了仪器分析实验中阳极溶出伏安法的改进方法。利用银汞固体电极阳极溶出伏安法连续测定痕量铜、铅、镉、锌。在pH=4.7的HAc-NH4Ac缓冲液中,富集电位为-1.3V,Cu2 、Pb2 、Cd2 、Zn2 在固体汞电极表面分别还原成金属,并沉积在工作电极上。溶出时电极上沉积的金属分别于-0.13、-0.45、-0.63和-1.00V产生4个灵敏的溶出峰,灵敏度与传统的液态汞电极相当。避免了汞电极使用中的不方便性和毒性。用于大学生实验可得到较好的实验效果。     

氰乙基壳聚糖修饰电极的制作及其应用

在壳聚糖的羟基上引入氰乙基 ,再通过共价键合的方式将改性后的氰乙基壳聚糖修饰到玻碳电极表面。研究了修饰电极的电化学行为以及阳极溶出伏安法测定Cu2 + 的条件。所制成的修饰电极对Cu2 + 的测定选择性进一步提高 ,常见的共存离子不干扰 ,在 pH =3 4的 0 1mol/LKNO3 溶液中 ,修饰电极对铜响应有很高的灵敏度 ,在Cu2 + 质量浓度为 1 0× 10 -8～ 1 0× 10 -6g/mL范围内 ,阳极溶出峰电流与铜的质量浓度呈良好的线性关系。     

电化学活化玻碳/铋膜电极制备及铅、镉离子敏感分析法

以电化学活化玻碳为基底电极原位制备金属铋膜电极,用之于分析Pb2+、Cd2+.方法如下:在氢氧化钠溶液中,由恒电位或循环扫描电位方法活化玻碳电极,随后以稀盐酸替代传统的醋酸缓冲液作为分析溶液将Bi3+与Pb2+、Cd2+共沉积在活化玻碳电极表面,再以方波阳极溶出分析法(SWASV)检测金属离子.结果表明:经简单的电化学清洗步骤即可高重现地再生电极表面,大幅度提高检测Pb2+、Cd2+的灵敏度,检测范围也可拓展至高卤素离子含量的样品.     

溶出伏安法测定乌药中的铜铅镉

在KNO3底液下,用线性扫描阳极溶出伏安法同时测定了乌药样品中铜、铅、镉3种金属的含量.结果表明,在最佳实验条件下,铜、铅、镉的峰电位分别为0.067、-0.45和-0.64V(vs ScE);铜、铅、镉金属离子的质量浓度在0-0.8 mg·L-1范围内,呈现良好的线性关系,相关系数分别为0.991 3、0.990 5...     

Thin-layer chromatographic behavior and separation of alkaline earth metals on silica gel in aqueous sodium perchlorate solution

The thin-layer chromatographic behavior of alkaline earth metal ions (Mg2+, Ca2+, Sr2+, and Ba2+) in aqueous sodium perchlorate solutions on silica gel thin-layers impregnated with sodium hydroxide has been surveyed as a function of salt concentration. At salt concentrations above 2 mol 1(-1), the selectivity of the metals increased with a decrease in the crystal ionic radii; with further increases in salt concentration, the selectivity differences among the metals expanded remarkably. In the present systems, it was supposed that the cation exchange, the surface complexation, and the salting-out effect participate simultaneously in the adsorption of the metals on silica gel. Typical chromatograms for the mutual separation of the alkaline earth metals are presented.     

过渡元素杂多钨硅酸盐氧化还原性质的研究

本文通过极谱和循环伏安法,结合紫外光谱和X射线光电子能谱,研究了过渡元素钨硅杂多酸盐Kn[SiM(H2O)W11O39](M=Mn^2^+,Fe^3^+,Co^2^+,Ni^2^+,Zn^2^+,Cd^2^+)在溶液中的氧化还原性质,提出了它们的还原机理.杂多阴离子的极谱半波还原电位E1/2的顺序为Ni^2^+>Co^2^+>Zn^2^+>Fe^2^+>Mn^2^+,发现杂多阴离子的E1/2与其组分中的过渡元素的电负性X和过渡金属离子与水合电子反应速率常数的对数logke-分别有线性关系,讨论了过渡元素对杂多阴离子氧化还原性的影响.     

A single-site model for divalent transition and heavy metal adsorption over a range of metal concentrations

Metal adsorption data over a range of surface coverages typically are characterized by curvilinear metal adsorption isotherms. These isotherms generally have a slope of 1 at low surface coverage and a shallower slope at higher surface coverages. The curvature of metal adsorption isotherms with increasing surface coverage is frequently interpreted in terms of sequential adsorption onto different types of surface sites, multinuclear surface complexation, or nonideality of metal adsorption. We demonstrate that the curvature of metal adsorption isotherms can also be attributed to changes in surface charge and potential that depend on the predominant type of metal surface complex. A single-site extended triple-layer model is used to reinterpret previously studied metal adsorption isotherms and pH edges for a wide variety of metals (Cd2+, Co2+, Cu2+, Pb2+, and Zn2+) and solids (goethite, hydrous ferric oxide, corundum, and magnetite) in different electrolyte solutions (NaNO3 and NaClO4). Only metal adsorption on ferrihydrite at very low surface coverages is not consistent with the single-site triple-layer model. This discrepancy might be explained if ferrihydrite is in fact not a single phase but a mixture of two or more phases. Metal surface coverages ranging from 10(-4) to 10.2 mmol/m2 on the other minerals can be accounted for with a single-site extended triple-layer model if appropriate metal adsorption reactions are chosen. In addition, several examples suggest that, within the context of the model, surface complexation schemes can be established that describe metal adsorption over both a wide range of surface coverage and a wide range of ionic strength.     

Study of the selection mechanism of heavy metal (Pb2+, Cu2+, Ni2+, and Cd2+) adsorption on clinoptilolite

The study was carried out on the sorption of heavy metals (Ni2+, Cu2+, Pb2+, and Cd2+) under static conditions from single- and multicomponent aqueous solutions by raw and pretreated clinoptilolite. The sorption has an ion-exchange nature and consists of three stages, i.e., the adsorption on the surface of microcrystals, the inversion stage, and the moderate adsorption in the interior of the microcrystal. The finer clinoptilolite fractions sorb higher amounts of the metals due to relative enriching by the zeolite proper and higher cleavage. The slight difference between adsorption capacity of the clinoptilolite toward lead, copper, and cadmium from single- and multicomponent solutions may testify to individual sorption centers of the zeolite for each metal. The decrease of nickel adsorption from multicomponent solutions is probably caused by the propinquity of its sorption forms to the other metals and by competition. The maximum sorption capacity toward Cd2+ is determined as 4.22 mg/g at an initial concentration of 80 mg/L and toward Pb2+, Cu2+, and Ni2+ as 27.7, 25.76, and 13.03 mg/g at 800 mg/L. The sorption results fit well to the Langmuir and the Freundlich models. The second one is better for adsorption modeling at high metal concentrations.     

Detection of aniline at boron-doped diamond electrodes with cathodic stripping voltammetry

Boron-doped diamond (BDD) electrodes were used to investigate the possibility of detecting aniline by linear-sweep cathodic stripping voltammetry. It was found that the dimeric species (p-aminodiphenylamine and benzidine) formed by anodic oxidation of aniline during the accumulation period are involved in electrochemically reversible redox processes and, in acidic media, the shape of the stripping voltammetric response is suitable for aniline detection in the micromolar concentration range. The low background current of conductive diamond is an advantage compared to other electrode materials and allows a detection limit of 1 μM. Weak adsorption properties and the extreme electrochemical stability are additional advantages of BDD and it was found that, even after long-time measurements, the electrode surface can regain its initial activity by an anodic polarization in the potential region of water decomposition.     

Interaction between co-deposited metals during stripping voltammetry at boron-doped diamond electrodes

Electrochemical processes, which underlie the use of conductive diamond electrodes for the simultaneous detection of two or more metal ions in solution by anodic stripping voltammetry (ASV), have been investigated. The model analyte system studied contains the two metal species, Ag+(aq) and Pb2+(aq), and the experimental techniques employed include cyclic and square wave voltammetries, along with X-ray photoelectron spectroscopy and secondary electron microscopy. Although the bulk metallic forms of Ag and Pb are immiscible, several interactions in the system between the two metal species present are observed, which significantly influence the electrodeposition and electrodissolution processes which underlie ASV. The subsequent nucleation and growth of a given metal on the electrode surface is enhanced by the presence of the second metal on the surface. The encapsulation of one metal by the other, within the metal particulates that form on the electrode surface, significantly reduces the stripping yield at the potentials characteristic of the individual metals. The stripping potentials are also influenced by bonding interactions between deposited Ag and Pb, which broaden the characteristic stripping peaks in cyclic voltammetry, as well as producing underpotential deposition and stripping. Given these interactions, the extent to which ASV at diamond electrodes can be used to determine the solution concentrations of Ag+(aq) and Pb2+(aq) is considered.     

Anodic stripping voltammetry of antimony at unmodified carbon electrodes

Antimony is an element of significant environmental concern, yet has been neglected relative to other heavy metals in electroanalysis. As such very little research has been reported on the electroanalytical determination of antimony at unmodified carbon electrodes. In this paper we report the electrochemical determination of Sb(III) in HCl solutions using unmodified carbon substrates, with focus on non-classical carbon materials namely edge plane pyrolytic graphite (EPPG), boron doped diamond (BDD) and screen-printed electrodes (SPE). Using differential pulse anodic stripping voltammetry, EPPG was found to give a considerably greater response towards antimony than other unmodified carbon electrodes, allowing highly linear ranges in nanomolar concentrations and a detection limit of 3.9?nM in 0.25?M HCl. Furthermore, the sensitivity of the response from EPPG was 100 times greater than for glassy carbon (GC). Unmodified GC gave a comparable response to previous results using the bare substrate, and BDD gave an improved, yet still very high limit of detection of 320?nM compared to previous analysis using an iridium oxide modified BDD electrode. SPEs gave a very poor response to antimony, even at high concentrations, observing no linearity from standard additions, as well as a major interference from the ink intrinsic to the working electrode carbon material. Owing to its superior performance relative to other carbon electrodes, the EPPG electrode was subjected to further analytical testing with antimony. The response of the electrode for a 40?nM concentration of Sb(III) was reproducible with a mean peak current of 1.07?µA and variation of 8.4% (n?=?8). The effect of metals copper, bismuth and arsenic were investigated at the electrode, as they are common interferences for stripping analysis of antimony.     

High-voltage contactless conductivity detection of metal ions in capillary electrophoresis

The detection of alkali, alkaline earth and heavy metal ions with a high-voltage capacitively coupled contactless conductivity detector (HV-C(4)D) was investigated. Eight alkali, alkaline earth metal ions and ammonium could be separated in less than 4 min with detection limits in the order of 5 x 10(-8) M. The heavy metals Mn2+, Pb2+, Cd2+ Fe2+, Zn2+, Co2+, Cu2+ and Ni2+ could also be successfully resolved with a 10 mM 2-(N-morpholino)ethanesulfonic acid/DL-histidine (MES/His)-buffer. Zn2+, Co2+, Cu2+ and Ni2+ showed an indirect response. The detection limits for the heavy metals were determined to range from about 1 to 5 microM.     

阳离子交换色谱中色谱柱温度对碱金属与碱土金属离子保留的影响

研究了非抑制型阳离子交换色谱中色谱柱温度(25~50℃)对碱金属离子(Li+、Na+、K+、Rb+)和碱土金属离子(Mg2+、Ca2+、Sr2+)以及NH4+保留的影响。在Shim-pack IC-C1磺酸型阳离子交换柱上,以硝酸为流动相分离碱金属离子,以乙二胺或乙二胺-草酸(柠檬酸)为流动相分离碱土金属离子,随着色谱柱温度的升高,碱金属和碱土金属离子的保留时间均增长,其范特霍夫曲线具有良好的线性关系,斜率为负值,表明在此条件下碱金属和碱土金属离子的保留为吸热过程。在Shim-pack IC-SC1羧酸型阳离子交换柱上,以硫酸为流动相同时分离碱金属和碱土金属离子,随着色谱柱温度的升高,Mg2+、Ca2+的保留时间增长,而K+、Rb+的保留时间缩短,Li+、Na+、NH4+的保留时间基本不变。在此条件下,Mg2+、Ca2+、K+和Rb+的范特霍夫曲线具有良好的线性关系,其中Mg2+和Ca2+的曲线斜率为负值,K+和Rb+的曲线斜率为正值,表明Mg2+和Ca2+的保留表现为吸热过程,K+和Rb+的保留表现为放热过程。研究表明在不同固定相和流动相条件下,色谱柱温度对碱金属和碱土金属离子保留行为的影响不同。     

Voltammetry as an Alternative Tool for Trace Metal Detection in Peloid Marine Sediments

Here was demonstrated for the first time a possible application of abrasive stripping voltammetry in the direct measurement of trace metals in anoxic, sulfidic marine sediments (peloid mud) from a small and shallow (0.2–1 m) marine lagoon in Central Dalmatia, Croatia. Trace amounts of sample compounds are transferred to the graphite electrode surface and electrochemical reduction or oxidation processes are followed by the cyclic voltammetry in seawater or 0.55 M NaCl as electrolyte. After a preelectrolysis at potentials ranging from ?1.0 to ?1.5 V (vs. SCE) a well‐defined anodic stripping peak corresponding to the oxidation of metal deposits generated at deposition potentials is obtained around ?0.74 V (vs. SCE). The same samples were studied by anodic stripping voltammetry at the Hg electrode and inductively coupled plasma‐mass spectrometer (ICP‐MS). ICP‐MS showed higher concentrations of trace metals such as Al, Fe, Mo, Mn. A relatively high concentration of reduced sulfur species (RSS) (10^?3 M) is determined electrochemically in porewater of the peloid mud, indicating that the magnitude of metal enrichment in the sediments is probably controlled by precipitation with sulfide.