排序方式: 共有46条查询结果,搜索用时 140 毫秒
1.
M. Biziuk J. Namiesnik 《International journal of environmental analytical chemistry》2013,93(3-4):193-207
Abstract A simple device for isolation of organic compounds from aqueous samples has been designed and its operating parameters tested during bioth periodic and continuous operation using isolation of organochlorine compounds as an example. A stream of an aqueous sample is pumped at elevated temperature by a piston pump to an unit for expransion of the liquid phase surface, where the liquid is sprayed on the walls of the unit and flows down freely. Organochlorine compounds passing to the gaseous phase are purged with a stream of purified air, oxidied and the chlorides formed are determined coulometrically. The designed device, due to its simplicity, can be built and employed in each averagely equipped laboratory. 相似文献
2.
应用循环伏安法(CV)、线性扫描伏安法(LSV)、控制电位电解库仑法(BE)对西维来司他的电化学行为进行了研究。在0.2mol/LHAc-NaAc(pH=5.6)缓冲液中,对其进行扫描,发现于-1.29V(vs.SCE)处产生一灵敏的还原峰,其峰电流与西维来司他的浓度在1×10-5~2×10-4mol/L范围内呈良好的线性关系(r=0.9976);检出限为2.0×10-6mol/L。对5.0×10-5mol/L西维来司他溶液进行12次平行实验,RSD为0·56%。实验结果表明,西维来司他在极谱电极上有吸附性质,并为此求得了电极反应的电子转移数为4,同时对电极反应机理进行了研究。 相似文献
3.
E. Beinrohr 《Accreditation and quality assurance》2001,6(7):321-324
The possibility of calibration-less determination of trace concentrations of some electrochemically active elements such as
Ag, As, Cd, Hg, Pb, etc. by flow-through coulometry is described. The analyte species are collected quantitative-ly from the
flowing sample solution on a porous working electrode made of vi- treous carbon particles set at either a constant potential
or constant current. The deposit is stripped by a constant current in the next step and the correspond- ing electrical charge
is measured and evaluated. The analyte concentration is calculated by making use of the com- bined Faraday’s laws of electrolysis.
The method exerts detection limits about 1 μg/l or lower and a linear concentration range over 3 orders of magnitude. 相似文献
4.
二氧化碳和氧气的快速电化学方法联合测定 总被引:4,自引:0,他引:4
根据O2和CO2在二甲亚砜(DMSO)介质中Pt电极上的伏安特性,采用微电极并结构计算机控制的电位调制技术,建立了快速联合测定CO2和O2的调制电位脉冲库仑法和调制电位脉冲电流法,取得了满意的结果。一次测量时间快达40ms。CO2检测范围0 ̄10%(体积百分比);O2检测范围不受限制。通过编程设计特定的调制电位-时间波形,可保持连续检测的长期稳定性。 相似文献
5.
恒电流库仑法测定基准试剂三氧化二砷的含量 总被引:2,自引:0,他引:2
用恒电流库仑法测定基准试剂三氧化二砷的含量,以恒电流通过含有碘化钾,基准试剂三氧化二砷试样的弱碱性水溶液,利用工作电极铂阳极上电生滴定剂I2与亚砷酸盐定量反应,以死停终点法确定滴定终点,测量出电解电流和电解时间,根据法拉第电解定律并利用EXCEL计算出基准试剂三氧化二砷的含量。方法的回收率为100%。 相似文献
6.
The possibility of coulometric titrations of cysteine, 2-thio-uracil, 6-mercaptopurine, and 6-thioguanine with iodine and bromine in methanol and with bromine in acetic acid has been investigated. Conditions have been found for the direct titration of the test substances with iodine in methanol based on their 1-electron oxidation to the corresponding disulphides and for their direct and indirect determination with bromine in acetic acid based on their 6-electron oxidation to the corresponding sulphonic acids.On leave from Department of Analytical Chemistry, Charles University, Prague, Czechoslovakia 相似文献
7.
Controlled potential coulometric (CPC) studies were carried out for developing a method to determine gallium at milligram levels, in the mixed supporting electrolyte medium (4 M NaClO4 + 0.5 M NaSCN), employing stirring mercury as a working electrode. Investigations for optimization of working electrode potentials, quantity of charge, level of background current and electrolysis time for achieving quantitative reduction of Ga(III) to Ga and its oxidation back to Ga(III), were undertaken. Effect of gallium content and interference of zinc in of gallium determination were also studied. The developed methodology was employed for the determination of gallium in pure Ga as well as in synthetic U + Ga mixture solutions. Accuracy and precision values of better than 0.5% were obtained at 1-2 mg levels. 相似文献
8.
Using methods of potentiostatic coulometry, the solubility of thallium(I) iodate in 0.1m sodium perchlorate and in 0.1m perchloric acid was determined over the temperature range 2–75°C. Thermodynamic functions were calculated for the dissociation of thallium(I) iodate into its aqueous ions. From the solubilities in the acid solutions the dissociation constant of iodic acid was calculated over the temperature range, along with the value of –1.83±0.07 kcal-mol–1 for the standard enthalpy change for the dissociation. 相似文献
9.
10.
《Electroanalysis》2006,18(22):2225-2231
The mechanism of electrochemical behavior of catechol in the presence of thiaproline is investigated by cyclic voltammetry, controlled‐potential coulometry and spectrophotometric tracing of the reaction coordinate. The results indicate that thiaproline participate in with an ECEC mechanism in a nucleophilic (Michael) addition to o‐quinone. Effect of pH of buffer solution on reaction pathway is studied and showed that addition of thiaproline to the o‐quinone is performed only in solutions with pHs higher than 5. These results indicate that the addition of thiaproline is occurred first from amine functional group. In the second step, the addition of carboxylate group of thiaproline to C‐5 of catechol results the final product with a lactone ring in its structure. Observation of two isosbestic point in absorption spectrum during the progress of the electrolysis together with the FT‐IR results for final product can be presented as evidence for two step addition of thiaproline to catechol. Final product, due to the electron donor property of thiaproline, more easily oxidized respect to the former catechol and as a result, a new redox couple is obtained for this compound in lower potentials. The easier anodic oxidation of addition product (relative to catechol) caused to an increase in anodic current for catechol, which is proportional to the thiaproline concentration. The differential pulse voltammetry (DPV) is applied as a sensitive voltammetric method for the detection of thiaproline. A linear range from 5×10?8 to 5×10?6 M with a detection limit of 1×10?8 M is resulted for thiaproline. With respect to the reversibility of the electrochemical reactions in the mechanism, and also more facile oxidation of the addition products, the square‐wave voltammetry is presented as a method with considerably more sensitivity for the detection of sub‐micromolar amounts of thiaproline. The advantageous properties of the voltammetric method for thiaproline detection lie in its excellent catalytic activity, sensitivity and simplicity. 相似文献