Ion-selective electrode for the determination of dimethylbenzylammonium ions

A sensor is proposed for the direct potentiometric determination of dimethylbenzylammonium in acid and neutral aqueous solutions. The sensor membrane is made of a polymeric composition on the basis of polyvinylchloride containing an ion associate and a solvent as a plasticizer. Salts of the tetraphenylborate anion and its derivatives served as ionophores. Basic electroanalytical parameters of the developed potentiometric sensors are studied and the pH range of their possible application is determined. The developed sensor is used as a reference electrode in the potentiometric titration of dimethylbenzylammonium with tetraphenylborate anions.     

Valgran, a program for potentiometric titrations with a versatile automatic modular system

A very flexible modular system for use with a portable IBM PC for potentiometric titrations is described. The appropriate software has been developed in order to obtain automatic end-points, and conventional, first-derivative, second-derivative and Gran curves, as well as a listing of the potentiometric points expressed in different ways. All these alternatives are selectable on menu presentations. The potentiometric system has been applied both the research and routine problems.     

Potentiometric study of reaction between periodate and iodide as their tetrabutylammonium salts in chloroform. Application to the determination of iodide and potentiometric detection of end points in acid-base titrations in chloroform

A potentiometric method for the titration of tetrabutylammonium iodide (TBAI) in chloroform using tetrabutylammonium periodate (TBAPI) as a strong and suitable oxidizing reagent is described. The potentiometric conditions were optimized and the equilibrium constants of the reactions occurring during the titration were determined. The method was used for the determination of iodide both in chloroform and aqueous solutions after extraction into chloroform as ion-association with tetraphenylarsonium. The reaction between TBAPI and TBAI was also used as acid indicator for the potentiometric detection of end points of acid-base titrations in chloroform.     

Deep Learning-Enhanced Potentiometric Aptasensing with Magneto-Controlled Sensors

Bioelectronic sensors that report charge changes of a biomolecule upon target binding enable direct and sensitive analyte detection but remain a major challenge for potentiometric measurement, mainly due to Debye Length limitations and the need for molecular-level platforms. Here, we report on a magneto-controlled potentiometric method to directly and sensitively measure the target-binding induced charge change of DNA aptamers assembled on magnetic beads using a polymeric membrane potentiometric ion sensor. The potentiometric responses of the negatively charged aptamer, serving as a receptor and reporter, were dynamically controlled and modulated by applying a magnetic field. Based on a potentiometric array, this non-equilibrium measurement technique combined with deep learning algorithms allows for rapidly and reliably classifying and quantifying diverse small molecules using antibiotics as models. This potentiometric strategy opens new modalities for sensing applications.     

Ionic Liquids Modify the Performance of Carbon Based Potentiometric Sensors

A new type of potentiometric sensor based on a recently constructed carbon ionic liquid electrode (CILE) is described. Two kinds of ionic liquids, i.e., N‐octylpyridinium hexafluorophosphate (OPFP) and 1‐butyl‐3‐methylimidazoluim hexafluorophosphate (BMFP) were tested as binder for construction of the carbon composite electrode. The characteristics of these electrodes as potentiometric sensors were evaluated and compared with those of the traditional carbon paste electrode (CPE). The results indicate that potentiometric sensors constructed with ionic liquid show an increase in performance in terms of Nernstian slope, selectivity, response time, and response stability compared to CPE.     

Towards Reversibility of Ion Transfer Across the Interface between Valinomycin Membranes and Aqueous Electrolyte Solutions

Valinomycin-based potassium-selective membranes doped with potassium tetrakis(4-chlorophenyl)borate (KClTPB) or sodium tetrakis(4-fluorophenyl)borate (NaFTPB) are studied in KCl, NaCl, and CaCl₂ solutions by potentiometric and electrochemical impedance methods. Before contact with KCl, membranes doped with NaFTPB provide Nernstian potentiometric response to Na⁺ ions, which is lost after conditioning the membranes in KCl. The membranes doped with KClTPB even before contact with KCl give no Nernstian response to Na⁺ ions. In CaCl₂ solutions, none of the membranes provide a regular potentiometric response. Despite the difference in potentiometric behavior, the impedance spectra of the membranes are very similar in all solutions regardless of prior conditioning of the membranes. No evidence for a hindrance towards charge transfer processes is observed. The results suggest that the membrane/solution interface is reversible for interfering ions as well as for potassium, and the contamination of solutions with the latter is the sole reason for the lack of Nernstian response in the interfering electrolytes.     

Formula for the equivalence volume in potentiometric titration. As illustrated by the microdetermination of organohalogens with ion-selective electrode

An equation for calculating the equivalence volume in potentiometric titration is suggested. The derivation of this equation is illustrated by the potentiometric titration of halide with incremental addition of the titrant silver nitrate. The equation is generally applicable to any potentiometric titration involving a simple and rapid reaction whose Nernstian response is constant. It is proposed to utilize it for common microdeterminations involving ion-selective electrodes.     

Effects of ion association of lipophilic quaternary ammonium salts in ion-exchange and potentiometric selectivity

It has been found experimentally and substantiated theoretically that the anion-exchange selectivity in water—lipophilic quaternary ammonium salts (QAS) toluene solutions systems as well as the potentiometric selectivity of plasticized PVC membranes containing QAS, are strongly influenced by ion association. In particular, it has been demonstrated that varying the steric accessibility of QAS exchange center is a powerful tool for the selectivity control. The experimental values of the selectivity change caused by variations in the QAS exchange center steric accessibility were about 3 orders of magnitude when the single-charged ions were exchanged for the single-charged ones and more than seven orders when double-charged ions were exchanged for the single-charged. The above effects have also been observed for the potentiometric selectivity of QAS-based PVC membranes and, to some extent, for the potentiometric selectivity of the neutral anion carrier-based membranes doped by QAS to provide anion permselectivity. This fact is of immediate practical interest for the development of ISE with improved selectivity. The obtained results allow to revise the generally accepted idea of QAS as “nonselective” ion-exchangers and to suggest specific ways for controlling the ion-exchange and potentiometric selectivity using the ion association as a tool.     

Influence of decyl alcohol on the potentiometric behavior of three p-alkylbenzenesulfonate ion-selective electrodes

The influence of decyl alcohol on the potentiometric response of three para-alkylbenzenesulfonate (p-RBS) electrodes is analyzed. The results are clearly dependent on the membrane surface polarity due to the presence of the alcohol. The ionophore was the complex trioctylmethylammonium-p-RBS, (TOMA+)-p-RBS-, with R=H, CH3, and C2H5. The nature of the complex plays a fundamental role on the potentiometric behavior of the electrode showing that the more hydrophobic the complex, the better the potentiometric responses. Moreover, the electrodes selectivities for several hydrophilic and hydrophobic interfering anions were determined. The potentiometric results with interfering anions were coherent with the Pearson's hard and soft acid-base character of these anions.     

Comparison of the in vitro susceptibilities of gram-positive organisms to four macrolide antibiotics by the lipoic acid-based potentiometric procedure

The potentiometric measurement of lipoic acid reduction was used to evaluate and compare the in vitro antibacterial activity of four macrolides against sensitive strains of Staphylococcus aureus and Group A Streptococcus. Apparent growth rates of organisms submitted to different antibiotic concentrations could be calculated from the potentiometric data, and a potentiometric minimal inhibitory concentration (MIC) was defined as the antibiotic concentration corresponding to an apparent zero growth rate. The potentiometric MIC of roxithromycin was similar to that of josamycin. Erythromycin and spiramycin exhibited respectively the strongest and the lowest inhibiting power. These potentiometric results were in good agreement with classical MICs. They show that the lipoic acid-based assay may usefully complement the conventional tests of in vitro antibacterial susceptibility to antibiotics.     

Solid-state potentiometric gas sensors—current status and future trends

The development of potentiometric sensors for monitoring environmental gases has become a well-established direction in sensor technology. Various types of potentiometric sensors employing solid electrolytes for in situ measurements of such gases as oxygen, hydrogen, carbon dioxide, sulfur oxides, carbon monoxide, nitrogen oxides, and hydrocarbons are reviewed. Particular concern was given to the CO₂ potentiometric sensor which is an example of successful commercial application. The construction details, working mechanism, and performance of different types of potentiometric gas sensors are given. Special emphasis is given for the mixed-potential electrodes, which seems to be the principal direction for the future research and development of the sensor science and technology. Additionally, the future use of potentiometric sensors for the detection of other environmental gases is discussed.     

The automatic titration of primary aromatic amines with nitrous acid

The “dead-stop” and potentiometric systems have been compared as a basis for the automatic titration of primary aromatic amines with nitrous acid; either system can be used but the potentiometric method is more widely applicable and is less subject to interference. Titrations of sulphanilamide and o-anisidine have been made with two commercial titrimeters and with both instruments the results obtained were at least equal in precision to those which would normally be obtained in manual titrations.     

Construction of a permanganate ion-selective electrode and its application to potentiometric titrations

The construction of a liquid-membrane type permanganate ion-selective electrode and its application to potentiometric titrations are described. The benzylcetyldimethylammonium-permanganate ion-pair in the aqueous phase is easily extracted into nitrobenzene and the extract is employed as the liquid ion-exchange membrane of the ion-selective electrode. The electrode gives Nernstian response to permanganate in the concentration range from 10(-6) to 10(-1)M, and the potential is almost independent of pH over the range from 3.0 to 10.5. The electrode can be used as indicator electrode in potentiometric titrations with permanganate.     

全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量

采用全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量,用盐酸标准溶液进行滴定,考虑自动电位滴定仪的灵敏性和准确度,通过多次对比实验,确定了仪器的最佳工作参数、滴定剂浓度和样品称样量等滴定条件;对两个不同品位试样分别进行了11次平行测定,相对标准偏差(RSD)均小于1％.在碳酸锂试样中加入基准物质无水碳酸钠进行碳酸根的...     

电位滴定分析方法在地质样品主量元素检测中的应用

对电化学分析法与电位滴定法的发展进行了简要介绍。电位滴定法是将电位分析与传统滴定法进行结合的新型分析方法,其反应类型包括酸碱滴定、沉淀滴定、氧化还原滴定与络合滴定,因其仪器操作简单,终点判断更加明确且节省人力的特点而得到广泛关注,因此就近年来电位滴定在地质样品中主量元素检测的应用进行了总结,分别对石灰石、白云石、硅酸盐、铬矿石、铁矿石、锰矿石、铜矿石与水等地质样品的电位滴定检测方法进行了阐述,电位滴定的应用将随着技术发展得以提升。     

A Three‐Dimensional Origami Paper‐Based Device for Potentiometric Biosensing

Current paper‐based potentiometric ion‐sensing platforms are planar devices used for clinically relevant ions. These devices, however, have not been designed for the potentiometric biosensing of proteins or small molecule analytes. A three‐dimensional origami paper‐based device, in which a solid‐contact ion‐selective electrode is integrated with an all‐solid‐state reference electrode, is described for the first time. The device is made by impregnation of paper with appropriate bioreceptors and reporting reagents on different zones. By folding and unfolding the paper structures, versatile potentiometric bioassays can be performed. A USB‐controlled miniaturized electrochemical detector can be used for simple and in situ measurements. Using butyrylcholinesterase as a model enzyme, the device has been successfully applied to the detection of enzyme activities and organophosphate pesticides involved in the enzymatic system as inhibitors. The proposed 3D origami paper device allows the potentiometric biosensing of proteins and small molecules in a simple, portable, and cost‐effective way.     

电位滴定法测定抛光液中的三酸含量

探讨了利用自动电位滴定仪对抛光液中磷酸、硫酸及硝酸的分析方法,以及对溶剂的标定方法。电位滴定法测定三酸,先用硫酸亚铁铵滴定硝酸,再用氢氧化钠滴定磷酸和硫酸,从而计算三酸含量。结果表明,与传统滴定法相比,电位滴定法标定硫酸亚铁铵的相对标准偏差(RSD)从1.1%降至0.13%,标定氢氧化钠的RSD从0.72%降至0.06%。电位滴定法测定自配样品及工厂抛光产品中的硝酸,回收率分别在96%及93%以上。电位滴定法测定自配样品及工厂抛光产品中磷酸和硫酸的回收率偏差在3%以内。手动滴定法测定磷酸和硫酸的回收率偏差在5%~10%,回收效果不如电位滴定法。电位滴定法测定工厂抛光液的三酸加标回收率偏差均小于3%。自动电位滴定法比手工滴定的准确性和精密度明显提高,弥补了手工滴定法只能分析磷酸和硫酸,而无法测定硝酸的缺陷。     

Differential potentiometric stripping analysis

Differential potentiometric stripping analysis, a sensitive instrumental modification of potentiometric stripping analysis, is described. For trace elements like cadmium and lead, which exhibit transport-controlled potentiometric stripping, signal enhancement is possible by employing a scheme involving multiple stripping and re-reduction of the preconcentrated analytes. For such elements the detection limit is below 5 × 10^-10 M with 60-s plating. The accuracy of the technique is tested on a biological reference material. Like potentiometric stripping analysis, the technique presented is not sensitive to reversible redox couples in solution.     

The effect of the ion exchanger site-counterion complex formation on the selectivities of ISEs

Using the model of ideally associated solution, the effect of ion association of the ion exchanger sites with main and foreign counterions on the selectivity of ISEs based on liquid ion exchangers has been considered. Equations which describe the potentiometric selectivity coefficient as a function of ion association constants in the membrane phase and of standard free energies of transfer of the determined and foreign ions from water to the membrane are obtained for the following main cases: (a) the determined and foreign ions are single-charged; (b) the determined ion is double-charged and the foreign ion is single-charged. It is shown that in the case of single-charged main and foreign ions, the ratio of the ion association constants has a great effect on the potentiometric selectivity of membranes, only if the ion exchanger sites produce less strong associates with the determined counterion as compared with the foreign one. Otherwise, this effect is insignificant. The selectivity for double-charged ions should increase, other things being equal, as the first constant of association of these ions with the ion exchanger sites increases. The effect of producing ion triplets of the type I(2)R((+/-)) on the selectivity of ISEs is also considered. Experimental data are presented which illustrate the effect of the nature of the ion exchanger on the potentiometric selectivity. Some procedures employing the factor of ion association for increasing the potentiometric selectivity of liquid ion exchange membranes are considered.     

Determination of free nitrilotriacetic acid in environmental water samples by ion chromatography with potentiometric and amperometric detection with a copper electrode

An ion-chromatographic method is described for the analysis of free nitrilotriacetic acid in water samples. Separations are achieved on a polymer-based anion-exchange column with 6 mM nitric acid as eluent. Both potentiometric and amperometric detection have been applied using metallic copper as the indicator electrode. Detection limits are at about 500 ng injected in the potentiometric mode and 100 ng in the amperometric mode. On-line sample preconcentration is possible for volumes up to 2 ml of river water samples. The response of the detector to other aminopolycarboxylic and aminopolyphosphonic acids has been investigated.