Differential Titration Based on Transient ISE Response

Abstract

A new way of evaluating potentiometric titrations based on the transient response of some ISE's is described. The method is illustrated using the titra 2+ tion of sulphate with a Ba solution using a Na-ISE in weakly mineralized waters.     

Potentiometric Measurements in Non-Aqueous Media Using Bromide and Iodide Ion Selective Membrane Electrodes

Abstract

Solid membrane bromide and iodide ion selective membrane electrodes were evaluated for their performance in non-aqueous media. The electrodes were evaluated in several alcohols and glacial acetic acid.     

Bayesian Methods for Ion Selective Electrodes

With the increasing use of ion‐selective electrodes in environmental and health applications, it is important to know the precision of estimated concentrations. A Bayesian model for non‐linear calibration is introduced which provides estimates of measurement precision by incorporating uncertainty in calibration parameters and inherent random noise in emf response. The analysis of lead in 17 soil samples demonstrates that large gains in precision are possible when calibrations are extended to include multiple electrodes and standard addition data. The results highlight the need for improved calibration and routine use of standard addition as ion selective electrodes become increasingly popular for demanding, real world applications.     

氟的离子选择电极瞬时电位法测定

研究了氟离子选择电极瞬时电位分析法，其检出限和Nernst响应下限均低于传统电位分析法，空白液切换到试液时瞬时电位达到稳定的峰电位Vp比传统电位法的响应快得多，可以实现小体积试液的快速准确分析；用该法测定了自来水和矿泉水中氟的含量；利用校正曲线的截距和检出限计算了LaF3的溶度积，在0.1mol/L KNO3介质中Ksp(LaF3)=10^-28.45，在0.001mol/L柠檬酸钠＋HAc-NaAc缓冲液（pH=5.50，离子强度I＝0.10mol/L)介质中溶度积K′sp(LaF3)=10^-26.26；据此，计算得柠檬酸与La^3 络合物的稳定常数K1=10^5.46和K2=10^3.99；用离子水合吉氏自由能ΔGh(F^-,g)解释了不同浓度F^-试液瞬时电位的跃迁时间。     

Selective Determination of Nicorandil with a Single Planar Solid-state Potentiometric Ion Selective Electrode

Novel screen-printed electrodes (SPEs) were constructed for the quantitation of nicorandil (NIC) in its pharmaceutical formulations. Different ion-exchangers and plasticizers were investigated, but the optimal potentiometric response was obtained using nicorandil-phosphotungstate (NIC-PTA) ion associate and tricresyl phosphate as a plasticizer. A Nernstian response of 58.80±1 mV/decade was obtained over a concentration range of (1×10⁻⁶–1×10⁻²) M with 1×10⁻⁵ M as a detection limit. Sensor morphology was characterized using scanning electron microscopy (SEM). The method was validated for the assay of NIC with high selectivity, accuracy (average recovery=100.54 %), and precision (%RSD≤2).     

Solid Contact Micropipette Ion Selective Electrode for Potentiometric SECM

New solid contact ammonium micropipette electrodes (ISE), well applicable in scanning electrochemical microscopy are reported. The solid contact was made of a PEDOT nanowire coated carbon fiber, lowered down close to the orifice, and dipped inside the cocktail being in the pipette tip. This configuration provided low electrical resistance and good potential stability. Submicron tip size, usual in case of micropipette ISE‐s easily can be fabricated in this way. The applicability of the electrode in SECM has been proved in SG/TC mode imaging urease enzyme active spots in urea solutions.     

Studies On The Use Of Halide Ion Selective Electordes In Salt Media And The Extension Of The Generalized Standard Addition method To Determine The Concentration Of Halide Ions In Geothermal Brins

Abstract

The effect of chloride on the bromide and iodide solid state precipitate electrodes is studied and selectivity constants calculated. The use of multiple linear regression analysis to determine the initial concentration of halide ions in solutions is studied and the resulting technique is used to determine fluoride, iodide and bromide in a geothermal-geopressured brine.     

Determination of Formaldehyde by Argento-Metric Potentiometric Titration Using an Iodide-ion Selective Electrode

Abstract

An argentometric potentiometric method for the precise determination of formaldehyde using an iodide -ion electrode is described. Formaldehyde was determined by titrating the iodide-ion generated by the reaction with iodine in an alkaline medium. The accuracy and precision were better than 0.1% under the optimum condition.     

Determination of Pyrethroids by Potentiometric Titration with Silver Nitrate Solutions Using Semiconductor Indicator Electrodes

Characteristics of modified electrodes with InAs and InSb membranes were studied in AgNO₃solutions. Based on the results obtained, a simple and rapid procedure was developed for the potentiometric titration of cyano group-bearing pyrethroids with AgNO₃solutions.     

The Impossibility of Measuring Individual Ion Activity Coefficients Using Ion Selective Electrodes

The pressing aim of this work is to prevent an error from proliferating. In arecent paper, a new procedure for calculating the junction potentials has beenpresented, whose purported goal is to allow individual ion activities and activitycoefficients to be identified using the appropriate ISEs. As convincing and usefulas this procedure may seem, it is, however, fallacious. The present analysisconsiders the results obtained when applying the procedure to typical friendlycases liable to precise thermodynamic–mathematical treatments. It is shown thatthe individual ion activities found are a mere artifact of the initial settings and,therefore, change accordingly. The implications raised from the values of suchindividual ion activities and, in particular, those concerned with the modifiedHydration Theory, are, in turn, devoid of any real experimental validation.     

用电活性离子对制成的离子选择电极测定阳离子表面活性剂

制备了3种基于不同电活性物质(十二烷基二甲基苄基铵-四苯硼、十六烷基三甲基铵-四苯硼、十八烷基三甲基铵-四苯硼)的阳离子表面活性剂离子选择电极,并对其性能做了测定,结果显示该类电极对阳离子表面活性剂十二烷基二甲基苄基氯化铵、十六烷基三甲基溴化铵、十八烷基三甲基氯化铵均有能斯特响应。以此类电极作为指示电极,四苯硼钠溶液作为滴定剂,对阳离子表面活性剂(十二烷基二甲基苄基氯化铵、十八烷基三甲基氯化铵、海明1622)进行了活性物含量的测定,与两相滴定法测定结果进行了比较。     

双臂套索冠醚PVC膜碘离子选择电极

研究了两种新型双臂套索冠醚1，10－二（5－氯－8－羟基喹啉－7－亚甲基）－1，10－二氮杂－4，7，16－三氧杂－13，19－二硫杂环二十一烷（Ⅰ）和1，13－二（5－甲基－8－羟基喹啉－7－亚甲基）－1，13－二氮杂－4，7，10－三氧杂－16，19－二硫杂环二十一烷（Ⅱ）为载体的PVC膜电极的响应行为；实验结果表明，两电极均显示阴离子响 应，其中对碘离子具有优良的能斯特电位响应性能，线性范围为10^－5－10^-1mol/L，斜率分别为－59．1mV/pcI-和－57．6mV/pcI-；电极具有读数稳定，重复性好，PH值范围宽等优点；将该电极用于药品中碘含量的测定，其结果与药典法一致。     

Complexometric Titration of Metals Using a Lead Selective Electrode

Abstract

A solid state lead selective electrode is used satisfactorily to indicate the end point eufing the complexometric titration of Ni, Co, Zn and V (IV) with EDTA, CDTA, and DTPA, in presence of a small amount of the corresponding lead complex. The optimum pH for the titration was in the range of 4.0 to 6.0. The quantity of lead complex used was variable and should be determined in each case. The best results are obtained when the metals being determined are present in the range of 25 to 50 micromoles. Nickel, cobalt, and zinc give good results with DTPA at pH 6.0; vanadium(IV) gives excellent results with any of the three reagents in the pH range of 4.0 to 6.0.     

Determination of Sulphur in Solid and Liquid Samples by Potentiometric Titration with Ion Selective Electrode.

Abstract

This paper describes a potentiometric method for the determination of sulphur in solid and liquid samples, using a sulphide ion selective electrode after the reduction distillation step. The determination of sulphide in solid and liquid samples without prior treatment was carried out by direct and titration potentiometric methods.

The reproducibility of the method and the recovery of sulphate in solid samples was investigated using analytical reagent grade 99% sodium sulphate. Portions of aproximately 100 mg of reagent were subjected to the reduction distillation process. After the ion selective electrode showed a stable value of the potential, indicating that all the sulphate had been reduced to sulphide, the potentiometric titration with lead nitrate solution was performed. A mean recovery of 98% of sulphate was found. The potentiometric titration method described in this work, can be applied to determine S⁼ in solid samples with the advantage that it does not require sample solubilization or extraction prior to the determination. The method yields an almost total reduction of sulphur and also a good precision.     

Potentiometric Quantification of the Benzoate Ion in Nonalcoholic Beverages Using a Solid Electrode Modified with a Polypyrrole‐Based Selective Membrane

This work presents the results obtained on the construction of a potentiometric ion‐selective electrode based on a polypyrrole (PPy) selective membrane to quantify the benzoate ion in nonalcoholic beverages. The electrode modification with benzoate (Benz^?1) ion doped‐Ppy was carried out under an imposed potential, while the electrosynthesis optimization was undertaken using the modified Simplex method, such that the film’s sensitivity was maximized toward the benzoate ion. The maximum sensitivity recorded was ?52.02±1.55 mV/decade [Benz^?1] using a graphite powder‐araldite resin composite electrode. During the modified electrode’s characterization it was found out that the response and drift were relatively short, namely 2 min and 0.4 mV min^?1 respectively, within the 7 to 9 pH range, exhibiting a detection limit of 7×10^?4 mol L^?1 and a quantification range of 3×10^?3 at 10^?1 mol L^?1. Selectivity coefficients were evaluated with the Matched Potential Method obtaining in all cases values much less than 1. The benzoate concentration in commercially available juices and sweetened beverages was evaluated comparing the results obtained with the proposed ion‐selective electrode and those of HPLC, the usually accepted technique. A statistical analysis of the results led to the conclusion that there exists no meaningful difference between the results obtained with both techniques, which shows the usefulness of the ion‐selective electrode to proceed with the quantification in real samples.     

离子选择性电极动力学分析法测定银

光度法测定某些金属离子催化K_4Fe(CN)_6与水的取代反应的动力学分析已有报道,但干扰较多,灵敏度低。用氰离子选择电极的电位动力学法测定Hg~(2+)、Au~(3+)已有研究。本文探讨了对银离子的测定,发现在一定条件下银离子浓度与电位值的变化有线性关系,线性范围在2.5×10~(19)～8.0×10~(-8)mol/L。此法干扰较少,灵敏度高。同时对该反应的机理也进行了初步探讨。     

A Method of Determining Selectivity Coefficients Based on the Practical Slope of Ion Selective Electrodes

It is a problem to be solved that the experimental selectivity coefficients of ion selective electrodes( ISEs) depend on the activity. This paper studied the new method of determining selectivity coefficients. A mixed ion response equation, which was similar to Nicolsky-Eisenman (N-E) equation recommended by IUPAC, was proposed. The equation includes the practical response slope of ISEs to the primary ion and the interfering ion. The selectivity coefficient was defined by the equation instead of the N-E equation. The experimental part of the method is similar to that based on the N-E equation. The values of selectivity coefficients obtained with this method do not depend on the activity whether the electrodes exhibit the Nernst response or non-Nernst response. The feasibility of the new method is illustrated experimentally.     

Enantioanalysis of Butaclamol Using Enantioselective Potentiometric Electrodes

Abstract

Three enantioselective, potentiometric electrodes were proposed for the enantioanalysis of butaclamol. The electrodes were based on immobilization of maltodextrins (MDs) of different dextrose equivalences [4.0–7.0, I; 13–17, II; 16.5–19.5, III] into carbon paste. The electrodes based on MD I and II were used for the enantioanalysis of S-butaclamol within linear concentration ranges of 10^?10 to 10^?7 and 10^?10 to 10^?8, respectively, with slopes of 51.20 and 57.59 mV/decade of concentration; whereas the electrode based on MD III was used for the enantioanalysis of R-butaclamol within a linear concentration range between 10^?10 and 10^?7 with a slope of 58.50 mV/decade of concentration. Recoveries greater than 90% were recorded for the enantioanalysis of butaclamol in synthetic and urine samples.     

铋膜电极微分电位溶出法测定生物材料中痕量铅

研究了镀铋膜电极替代镀汞膜电极痕量铅的微分电位溶出分析法(DPSA)。考察并优化了同位镀铋膜测定铅的条件。结果表明,在HAc-NaAc(pH=4.4)介质中,铅可在镀铋膜电极上得到灵敏的微分电位溶出峰;利用标准加入法对人尿及血中痕量铅进行了测定。本法避免了镀汞膜电极对人体健康及环境的危害。