含CTAB的开放体系与封闭体系的液膜振荡

本文对水(十六烷基三甲基溴化铵,CTAB)/硝基甲烷(苦味酸)/水(葡萄糖)体系的液膜振荡进行研究.应用电势线性扫描法通过测定界面电压变化研究了开放体系与封闭体系的液膜振荡并进行了对比,对开放体系还研究了不同滴定速度对液膜振荡的影响.根据J.Srividhya和M.S.Gopinathan的数学模型,对开放体系的振荡进...     

降解水中有机毒物的新型反应体系研究

利用空气中的氧电化学合成H₂O₂,制备具有较高电流效率的空气电极.将空气电极用于构成降解有机毒物的新型反应体系电化学氧化体系、光激发氧化剂氧化体系和光电-Fenton氧化体系.实验测量了H₂O₂在不同体系不同条件下的分解速率,并与相应的传统式体系作了比较.实验测量了苯胺在新型体系中的矿化反应速率,发现H₂O₂的分解速率与苯胺的矿化速率有良好的平行关系,其中H₂O₂分解速率最快的光电-Fenton体系是氧化降解有机分子的最佳体系.通过光电-Fenton体系和光-Fenton体系的比较,揭示了空气电极/溶液界面在光电-Fenton体系中所起的重要作用.初步讨论了苯胺分子在光电-Fenton体系中矿化反应的机制.     

混杂光固化体系的原理及应用

混杂光固化或双重固化是指在同一体系中采用两种或两种以上不同类型的聚合反应来使体系固化的方法,它是原位改性高分子的一种新方法.混杂光固化体系包括自由基-阳离子混杂光固化体系、自由基-缩聚混杂体系和自由基-自由基混杂体系等.本文综述了混杂光固化体系的原理及其应用.     

Rb2SO4-n-prOH-H2O三元体系10℃,30℃及50℃的等温平衡溶解度

采用半微量相平衡装置,测定了Rb2SO4-n-prOH-H2O三元体系10℃,30℃和50℃的等温平衡溶解度.这三个温度下体系的平衡固相皆为无水Rb2SO4.在30℃和50℃时体系在共饱和点处出现三相:醇相,水相和固相,而体系在10℃时溶液相不分层.确定了体系的分层温度,同时给出了体系10℃的溶解度关系式.     

高分子科学中的平均场理论和1/N展开

利用1/N展开理论考察高分子物理中的几个典型高分子体系.研究发现,平均场理论只有在体系具备一定对称性时才适用.在中性高分子溶液中,不论是单组分、多组分还是嵌段共聚物体系,1/N展开理论对于N取值不小于6时是适用的.对于聚电解质体系,平均场理论仍然可以粗糙地描述弱带电聚电解质的统计性质.对于强带电聚电解质体系,由于体系对称性大为降低,平均场理论不再适用,标度理论或许会是一个适合的方法.     

阴离子分散剂对酸化膨润土流变性的影响

研究了阴离子分散剂聚丙烯酸钠对质量分数为10%的酸化膨润土分散体系流变性的影响. 结果表明, 添加0.4%分散剂的分散体系的剪切应力、表观黏度和屈服应力最低. 其它体系流体均表现为从假塑型到胀流型流体的转变, 而含0.4%分散剂的体系始终表现为胀流型流体. 采用Herschel-Bulkley模型对各体系的流变曲线进行了拟合, 得到较好的拟合曲线, 同时探讨了酸化膨润土分散体系的流变机理.     

对高分子体系进行分子动力学模拟方法的研究

以单链聚乙烯为例,研究了多种对高分子体系进行分子动力学模拟的方法.结果表明,不同的力场条件可以导致明显不同的结果.在使用OPLS力场的真空条件下.在100K体系出现了玻璃化现象,在200和300K条件下体系出现了局部结晶现象,而在400和500K体系出现了熔化现象.在给定体系中加入周期性边界和在300K下进行分子动力学模拟,无序和结晶状态都具有一定的稳定性.     

高碳烯烃氢甲酰化研究

高碳烯烃氢甲酰化是最重要的石化技术之一.本文从均相催化体系和两相催化体系两个方面介绍了国内外近年来在研究与开发上取得的进展.两 相催化体系的开发正在成为研究的主流引人瞩目,预期新催化剂体系和两相体系在高碳烯烃氢甲酰化应用上将有突破.     

丙烯酰胺双水相聚合体系稳定性研究

通过浊点滴定法测定了不同温度下PAAmPEGH2O双水相体系相图,发现分相浓度随着温度的升高先增后降,55℃时分相浓度最低.双水相聚合体系微观结构显示,分散相以砾状液滴形式均匀分散在连续相中.研究了聚合过程中聚合体系粘度的变化,以及聚合温度、分散介质、单体、引发剂及乳化剂等对聚合体系最终粘度的影响,聚合体系最终粘度在一定范围内随分散介质和单体浓度增加变化不大,但是超过某一浓度后聚合体系粘度急剧增加;聚合体系中加入少量乳化剂对体系粘度影响不大,但加入大量乳化剂后体系稳定性变差,聚合体系粘度急剧增加;聚合体系最终粘度随着聚合温度升高先降后增,与相图的预测结果一致.     

阴阳离子表面活性剂混合体系在克拉玛依油田中获得超低界面张力

利用阴阳离子表面活性剂复配技术,在克拉玛依油田实际油水体系中获得了超低界面张力.通过添加非离子保护剂的第三组分,阴阳离子表面活性剂混合体系在克拉玛依油田回注水体系中的溶解度大大提高.确定了相关体系能够获得超低界面张力的表面活性剂的浓度和混合的比例范围,在克拉玛依油田的多个实际油水体系中获得了具有较大复配比例和较低表面活性剂浓度的实际配方,其中部分体系油水界面张力可接近10-4mN·m-1.同时,这类阴阳离子表面活性剂混合体系具有很好的抗吸附能力,在石英砂吸附72 h后体系依然呈现优良的超低界面张力.     

Improvement of the silver/silver chloride reference electrode and its application to pH measurement

When a silver/silver chloride (Ag AgCl ) reference electrode was used continuously in a low conductivity solution or reductive solution, it was often observed that stability of the liquid junction potential was lost. This phenomenon was remarkable with a Ag AgCl reference electrode compared to a calomel reference electrode. We found that 340 mg l(-1) of silver was dissolved in 3 M potassium chloride (KCl) internal solution as silver complex ions (AgCl(-(x-1))(x)) for x = 2 or 3. However, only 1.93 mg l(-1) of silver chloride (AgCl) can theoretically be dissolved in water. The complex ion that effused into the sample solution through the liquid junction clogged the liquid junction (e.g. porous ceramic) as AgCl, or as metallic silver (Ag) in reducing solution. Therefore, the constant effusion of KCl internal solution was inhibited, and the liquid junction potential became unstable or fluctuating. A new reference electrode was developed, which can eliminate AgCl(-(x-1))(x) in 3 M KCl internal solution by the use of chelating resins. A combination of this reference electrode with a pH electrode made long-term stable pH measurements possible.     

Needle-type ultra micro silver/silver chloride reference electrode for use in micro-electrochemistry.

A needle-type ultra micro silver/silver chloride reference electrode having a micro capillary with outer and inner diameters of 1.0 microm and 0.5 +/- 0.2 microm, respectively, was constructed. This micro reference electrode can be stuck into a living cell, and is applicable to use in very small environments, such as an electrochemical cell of an electrochemical scanning tunneling microscope or the detection portion of a micro-TAS. Excellent stability and repeatability of the micro reference electrode potential could be obtained by filling the micro capillary with agar gel containing 3.33 mol/L potassium chloride as a salt bridge, by covering the bare part of the silver wire on which silver chloride was deposited, and by electromagnetic shielding of the measurement cell and wire lead from the electromagnetic waves. The electrode showed stable potential for 7 days after its fabrication using 3.3 mol/L potassium chloride aqueous solution containing silver chloride as an internal electrolyte solution. The electrode exhibited constant electrode potential and excellent stability in test solutions of pH 5-9. The electrode potential of a commercial pH glass electrode measured against the micro reference electrode in standard pH buffer solutions was in good accordance with the Nernst equation.     

Determination of the performance of glass electrodes in aqueous solutions in the physiological ph range and at the physiological sodium ion concentration

A method for testing glass electrodes in the physiological pH range (6.4–7.6) and at the physiological sodium ion concentration (0.15 mol l^-1), based on indirect comparison of potentials with the hydrogen gas electrode, is developed according to a scheme described earlier. The hydrogen ion sensitivity and the sodium ion error of a glass electrode can be determined with three different aqueous solutions of amine buffers and their hydrochlorides; two of these have different pH values and one also contains a sodium salt (at the higher pH value). A cell without a liquid/liquid junction, containing silver/silver chloride reference electrodes, is used at 37° C. The accuracy of both determinations is ±0.2 mV (±0.003 pH). The results for some commercial glass electrodes tested with this method are presented.     

Investigation of a Thin‐film Quasi‐reference Electrode Fabricated by Combined Sputtering‐evaporation Approach

This paper presents the development of a thin‐film quasi‐reference electrode (tQRE), which was fabricated by sputtering silver (Ag) on a conducting gold layer. The Ag layer was subsequently covered by silver chloride (AgCl) with the aid of e‐beam evaporation. The functionality of the tQREs as reliable reference electrodes was confirmed by observing the potential response in solutions with various chloride ion concentrations. The influence of solution pH on the potential change of the tQREs was evaluated. In the solution with controlled ionic strength, the tQREs were able to provide stable and consistent potential outputs. Experimental investigation of the electrochemical sensors with integrated tQREs demonstrated potential applicability of the tQREs to be incorporated into miniaturized and disposable lab‐on‐a‐chip sensors for point‐of‐care/in‐situ measurements.     

Variability of selectivity coefficients of solid-state ion-selective electrodes

The generalized model for the selectivity mechanism of solid-state ion-selective electrodes has been experimentally verified. The experimental parameters investigated were the concentration of interfering ion, temperature and stirring. Among the systems studied were electrodes sensitive to chloride (bromide, iodide), bromide (chloride, iodide), iodide (chloride, bromide), silver (copper, lead), copper (silver, lead) and lead (silver, copper), the species given in brackets being considered as the interferents. The model has been confirmed except for cases where the concentration of ions formed at the electrode surface by metathesis is too small to be the factor that dictates the electrode potential.     

Determination of 3-methyl-4,5-dihydro-1,2,3-oxadiazolium ion,a putative nitrosamine metabolite,by ion-pair chromatography with electrochemical detection

A method for the chromatographic separation and detection of 3-methyl-4,5-dihydro-1,2,3-oxadiazolium (MDO) ion has been developed. Convenient retention times were obtained on a reversed-phase LC column by using the ion-pairing reagent 1-octanesulfonic acid in phosphate buffer as the mobile phase. The cyclic voltammogram of the analyte showed an irreversible cathodic wave between ?0.62 and ?0.78 V when silver/silver chloride wire was used as the reference electrode, permitting its detection at the nanomole level in aqueous solution. The best results were obtained with glassy carbon as the working electrode. The detector response was both reproducible and linear for injected amounts ranging from 6.2 to 62 nmol, suggesting that the method might be useful for determining the extent to which certain carcinogenic N-nitroso compounds are metabolically converted to the MDO ion and its homologues in vivo and in vitro.     

No more conventional reference electrode: Transition time for determining chloride ion concentration

Ion selective electrodes (ISE) are used extensively for the potentiometric determination of ion concentrations in electrolytes. However, the inherent drift in these measurements and the requirement of a stable reference electrode restrict the feasibility of this method for long-term in-situ applications. This work presents a chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode for measuring chloride ion concentration. An anodic current pulse is applied to a Ag/AgCl working electrode which initiates a faradaic reaction that depletes the chloride ions near the electrode surface. The rate of change in potential at the Ag/AgCl electrode, due to chloride ion depletion, reaches an inflection point once the chloride ions deplete completely near the electrode surface. The moment of the inflection point, also known as the transition time, is a function of the chloride ion concentration and is described by the Sand equation. It is shown that the square root of the transition time is linearly proportional to the chloride ion concentration. Drift in the response over two weeks is negligible: 59 μM/day when measuring 1 mM of Cl⁻ ions using a 10 A m⁻² current pulse. The transition time at a specific ion concentration can be tuned by the applied current pulse, e.g., in a solution containing 5 mM chloride ions, the transition times with current pulses of 10 and 20 A m⁻² are 1.56 and 0.25 s, respectively. The moment of inflection determines the response, and thus is independent of the absolute potential of reference electrode. Therefore, any metal wire can act as a pseudo-reference electrode, enabling this approach for long-term and integrated-sensor applications such as measurement inside concrete structures.     

Sequential injection with lab-at-valve (LAV) approach for potentiometric determination of chloride

Sequential injection with “Lab-at-Valve (LAV)” approach is demonstrated for potentiometric determination of chloride. The LAV flow-through electrode system consists of two Ag/AgCl electrodes: one as a reference electrode, silver chloride activated surface-silver wire soaked in a constant-concentration chloride ion solution in a small tube covered with a polymer-membrane, another as a working electrode (a similar silver chloride activated surface-silver wire) placed in a flow channel. The electrode system is attached at one port of a 10 port multiposition valve. A modified autoburette was used as a propelling device. Using SI operation via a program written in-house, based on LabVIEW^®, a standard/sample is inserted, via the selection valve, in potassium nitrate as an electrolyte and water is used as a carrier. The zones are transported from the holding coil to the flow cell to monitor the difference in potential due to concentration cell behavior. The potential difference is then recorded as a peak. Peak height is proportional to logarithm of chloride concentration. The SI-LAV for chloride determination is very simple, fast, precise, accurate, automatic and economical. Applications to mineral drinking water and surface water have been made. The results agree with those of IC and titrimetric methods.     

Silver(I) ion-selective membrane based on Schiff base-p-tert-butylcalix[4]arene

A PVC membrane electrode for silver(I) ion based on Schiff base-p-tert-butylcalix[4]arene is reported. The electrode works well over a wide range of concentration (1.0 x 10(-5)-1.0 x 10(-1) mol dm-3) with a Nernstian slope of 59.7 mV per decade. The electrode shows a fast response time of 20 s and operates in the pH range 1.0-5.6. The sensor can be used for more than 6 months without any divergence in the potential. The selectivity of the electrode was studied and it was found that the electrode exhibits good selectivity for silver ion over some alkali, alkaline earth and transition metal ions. The silver ion-selective electrode was used as an indicator electrode for the potentiometric titration of silver ion in solution using a standard solution of sodium chloride; a sharp potential change occurs at the end-point. The applicability of the sensor to silver(I) ion measurement in water samples spiked with silver nitrate is illustrated.     

Discontinuous-flow potentiometric determination of chloride in a large-volume wall-jet cell using an ion-selective electrode based on a silver chloride film chemically deposited on a silver iodide support

A robust and sensitive chloride ion-selective electrode can be prepared by modifying the surface of an iodide-selective electrode using the chemical reaction with mercuric chloride in an oxidizing medium containing excess chloride. A thin film of silver chloride is thus formed ensuring a rapid and reproducible response to chloride. The analytical parameters of this electrode are similar to those of commercial silver chloride ion-selective electrodes, but its electrical impedance and signal noise are substantially lower and the response somewhat faster. Its sensitivity toward surfactants is somewhat suppressed. The electrode was used for discontinuous flow potentiometric (DFP) determinations in a large-volume wall-jet cell in which the electrode surface can be continuously reactivated by a cleaning solution contained in the cell. The method was applied to determination of chloride in ground waters from an industrial waste dumping site. The limit of determination is low 9 mug Cl(-)/l (2.6 x 10(-7)M), the precision good (the relative standard deviation varies from 0.6 to 3.0% for chloride contents from 2.90 to 0.15 mg/l, respectively) and the method correlates satisfactorily with the results of an indirect AAS determination of chloride. The sample throughput is high-90 measurements can be carried out per hour, corresponding to 30-40 determinations per hour.