Unbiased Selectivity Coefficients of Potentiometric Sensors Using Thin Membrane Layers

Solid-contact ion-selective electrodes with thin membranes can more easily achieve complete ion exchange at the sample-membrane interface, giving unbiased selectivity coefficients. The calculated reconditioning rate corresponds well to experimental data. Alternatively, the redox state of the conducting polymer may be electrochemically switched resulting in primary ion expulsion from the membrane and interfering ion uptake from the sample. Both approaches were tested for tetrabutylammonium-selective electrodes. The approach's limitations are identified, which includes primary ions impurities in interfering ion salts and an interaction between primary ion and redox polymer. These limitations are visualized with ionophore-based sodium- and silver-selective electrodes.     

Preparation of Iodide Selective Carbon Paste Electrode with Modified Carbon Nanotubes by Potentiometric Method and Effect of CuS‐NPs on Its Response

In this research, multiwalled carbon nanotubes (MWCNTs) was oxidized and chemically modified through reaction with 3‐(trimethoxysilyl)propan‐1‐amine (TMSPA) and their subsequent reaction with 2‐hydroxy‐3‐methoxy benzaldehyde. Subsequently, this material was metalized by reaction with copper acetate that lead to formation and impergeation of 2‐methoxy‐6‐((3‐(trimethoxysilyl)propylimino)methyl)phenol MMSPIMP? MWCNT‐Cu. This novel material was identified with different techniques such as SEM and FT‐IR analysis. In this work, the reported material are exhibited high accurate and repeatable monitoring of iodide due to its high surface area with various reactive centre. It exhibited selectivity for iodide over the wide linear dynamic range between 1.8×10^?6 and 1.15×10^?1 M, with a Nernstian slope of ?59.12±0.7 mV per decade of activity and detection limit of 1.8×10^?6 M. Copper sulfide nanoparticles were prepared and their effect on the electrode response was investigated. The results were improved in the presence of nanoparticles with fast and stable response, good reproducibility, long‐term stability, high selectivity over the presence of common organic and inorganic anions, high detection limit and dynamic range. The proposed sensor has been applied as potentiometric determination of some iodine species over a pH range of 2.5–10.     

Novel Potentiometric Sensors of Molecular Imprinted Polymers for Specific Binding of Chlormequat

Molecularly imprinted polymers (MIP) were used as potentiometric sensors for the selective recognition and determination of chlormequat (CMQ). They were produced after radical polymerization of 4‐vinyl pyridine (4‐VP) or methacrylic acid (MAA) monomers in the presence of a cross‐linker. CMQ was used as template. Similar non‐imprinted (NI) polymers (NIP) were produced by removing the template from reaction media. The effect of kind and amount of MIP or NIP sensors on the potentiometric behavior was investigated. Main analytical features were evaluated in steady and flow modes of operation. The sensor MIP/4‐VP exhibited the best performance, presenting fast near‐Nernstian response for CMQ over the concentration range 6.2×10⁻⁶–1.0×10⁻² mol L⁻¹ with detection limits of 4.1×10⁻⁶ mol L⁻¹. The sensor was independent from the pH of test solutions in the range 5–10. Potentiometric selectivity coefficients of the proposed sensors were evaluated over several inorganic and organic cations. Results pointed out a good selectivity to CMQ. The sensor was applied to the potentiometric determination of CMQ in commercial phytopharmaceuticals and spiked water samples. Recoveries ranged 96 to 108.5%.     

Novel Biomedical Sensors for Flow Injection Potentiometric Determination of Creatinine in Human Serum

Coated‐wire (CW) and tubular (Tu) type membrane sensors for creatinine are developed. These consist of creatinine tungstophosphate(CTP), creatinine molybdophosphate (CMP) and creatinine picrolonate (CPC) ion‐pair complexes as electroactive materials dispersed in plasticized poly(vinyl chloride) matrix membranes. Electrochemical evaluation of these sensors under static (batch) mode of operation reveals near‐Nernstian response with slopes of 62.9, 58.1, and 55.2 mV decade^?1 over the concentration range 1×10^?2–5.0×10^?6, 1×10^?2–7.5×10^?5, and 1×10^?2?3.1×10^?5 mol L^?1. The lower detection limits are 0.39, 3.49, and 2.20 μg mL^?1 creatinine with CTP, CMP and CPC membrane based sensors plasticized with o‐NPOE, respectively. Tubular and coated wire CTP membrane sensors are incorporated in flow‐through cells and used as detectors for flow injection analysis (FIA) of creatinine. The intrinsic characteristics of the detectors under hydrodynamic mode of operation in a low dispersion manifold are determined and compared with data obtained under static mode of operation. With 10^?2 mol L^?1 phosphate buffer of pH 4.5 as a carrier solution, the tubular and coated wire CTP detectors exhibit rapid response of 58.9 and 50.7 mV decade^?1 over the concentration range 1×10^?2–1×10^?5 mol L^?1 and detection limits of 0.39 μg mL^?1 and 0.85 μg mL^?1, respectively. Validation of the assay methods with the proposed sensors by measuring the lower detection limit, range, accuracy, precision, repeatability and between‐day‐variability reveals good performance characteristics confirming applicability for continuous determination of creatinine. The sensors are used for determining creatinine in human blood serum at an input rate of 40 samples per hour. No interferences are caused by creatine, most common anions, cations and organic species normally present in biological fluids. The results favorably compare with data obtained using the standard spectrophotometric method.     

Development of a New Coated Graphite Phenylephrine Potentiometric Sensor and Its Applications to Pharmaceutical and Biological Analysis

The construction and performance characteristics of a coated graphite phenylephrine‐selective electrode based on incorporation of the ion‐association complex of phenylephrine‐tetraphenylborate in plasticized PVC matrix was studied. The electrode exhibited a Nernstian slope of 59.0 mV/decade to phenylephrine over a wide concentration range from 3.0×10^?6 to 5.6×10^?2 M with a low detection limit of 1.5×10^?6 M. The proposed electrode manifested advantages of fast response, long life time and, most important, good selectivities for phenylephrine relative to a wide variety of common foreign inorganic cations, anions and also organic species. The electrode was successfully applied to determine phenylephrine in adult cold tablets, phenylephrine eye‐drops and also blood serum samples. The inclusion complex formation between α‐ and β‐cyclodextrine and phenylephrine was studied potentiometrically by the proposed electrode.     

Chemically Modified Carbon Paste Electrode for Determination of Sulfate Ion by Potentiometric Method

Four Schiff base complexes of different metal ions, M=Cr(III), Mn(III), Fe(III), and Co(III), were studied to characterize their ability as sulfate ion carriers in carbon paste electrode (CPE). The modified CPE electrode with Schiff base complex of Cr(III), N,N′‐ethylenebis(5‐hydroxysalicylideneiminato) chromium(III) Chloride, showed good response characteristics to SO₄^2? ion. The proposed electrode exhibits a Nernstian slope of 28.9±0.4 mV per decade for SO₄^2? ion over a wide concentration range from 1.5×10^?6?4.8×10^?2 M, with a detection limit of 9.0×10^?7 M. The CPE electrode manifested advantages of relatively fast response time, suitable reproducibility and life time and, most important, good potentiometric selectivity relative to a wide variety of other common inorganic anions. The potentiometric response of the electrode is independent of the pH of the test solution in the pH range 4.0–9.0. The proposed electrode was used as an indicator electrode in potentiometric titration of sulfate with Ba²⁺ ion, the determination of zinc in zinc sulfate tablet and also determination of sulfate content of a mineral water sample.     

Polyaniline‐Based Sensor Material for Potentiometric Determination of Ascorbic Acid

Polyaniline (PANI)‐based sensor material for determination of ascorbic acid was synthesized by oxidative chemical polymerization of aniline on a screen‐printed carbon‐paste electrode. The influence of PANI chemical structure formed under various polymerization conditions on the sensor response was investigated. The presence of aniline dimer derivatives in PANI structure was found to induce significant improvement of the limit of detection and the linear dynamic range without a change in sensitivity. The sensor prepared by aniline polymerization in pH 7 buffer leading to the product containing mainly the aniline dimer‐based units showed the best detection limit of 0.1 µM. It was shown that the PANI‐based sensor could be used for ascorbic acid analysis in the presence of citrate and lactate as interfering ions. A quantitative determination of ascorbic acid concentration in beverages and vitamins was performed.     

Novel Potentiometric PVC‐Membrane and Coated Graphite Sensors for Lanthanum(III)

Preliminary theoretical studies revealed the selective complexation of bis (2‐mercaptoanil) diacetyl (BMDA) with La³⁺ over several alkali, alkaline earth and heavy metal ions. Thus, novel PVC‐based membrane (PBM) and coated graphite membrane (CGM) sensors for La(III) based on BMDA were prepared. The electrodes display Nernstian behavior over wide concentration ranges (i.e., 1.0×10^?5–1.0×10^?1 M for PBM and 1.0×10^?6–1.0×10^?1 M for CGM). The potential response of sensors was pH independent in the range of 4.0–8.0. The sensors possess satisfactory reproducibility, fast response time (<15 s), and specially excellent discriminating ability for La³⁺ ions with respect to most of the cations. The membrane sensor was used as an indicator electrode in potentiometric titration of lanthanum ions with EDTA. The coated graphite membrane electrode was applied in determination of fluoride ions in mouth wash preparations.     

Fabrication of Potentiometric Sensors for the Selective Determination of Ketoconazole

Abstract

The fabrication and analytical applications of two types of potentiometric sensors for the determination of ketoconazole (KET) are described. The sensors are based on the use of KET-molybdophosphoric acid (MPA) ion pair as electroactive material. The fabricated sensors include both polymer membrane and carbon paste electrodes. Both sensors showed a linear, stable and near Nernstian slope of 57.8 mV/decade and 55.2 mV/decade for PVC membrane and carbon paste sensors respectively over a relatively wide range of KET concentration (1 × 10^?2 ? 5 × 10^?5and 1 × 10^?2 ? 1 × 10^?6). The sensors showed a fast response time of < 30 sec and < 45 sec. A useful pH range of 3–6 was obtained for both types of sensors. A detection limit of 2.96 × 10^?5M was obtained for PVC membrane sensor and 6.91 × 10^?6 M was obtained for carbon paste sensor. The proposed sensors proved to have a good selectivity for KET with respect to a large number of ions. The proposed sensors were successfully applied for the determination of KET in pharmaceutical formulations. The results obtained are in good agreement with the values obtained by the standard method.     

New Potentiometric Membrane Sensors Responsive to Pb(Ii) Based on Some Recently Synthesized 9, 10- Anthraquinone Derivatives

ABSTRACT

New potentiometric membranesensorsresponsive to Pb(II) have been developed. The membrane sensors are based on three different 9, 10-anthraquinone derivatives. The electrode based on 1, 4-bis (prop-2¹-enyloxy)-9, 10-anthraquinone exhibits a good Nernstian response for Pb(II) ions over a wide concentration range (2.5×10^?6 - 1.0×10^?2 M) with a slope of 29.8 mV decade^?1. Detection limit is 1.5×10^?6 M. The response time of the sensor is 15s and the useful working pH range is 4.7-6.8. The membrane can be used for more than 4 months without any considerable divergence in potentials. The electrodes revealed comparatively good selectivities with respect to alkali, alkaline earth and some transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of lead ions (with sulfate and oxalate ions), and for the determination of lead in waste waters.     

A Novel Modified Carbon Paste Electrode for Potentiometric Determination of Mercury(II) Ion

A new modified carbon paste electrode (CPE) based on a recently synthesized ligand of Ethyl‐2‐(benzoylamino)‐3‐(2‐hydroxy‐4‐methoxyphenyl)‐2‐propenoate (EBHMP) as a suitable carrier for Hg²⁺ ion was described. The electrode exhibit a super Nernstian slope of 48.5±1.0 mV per decade for Hg²⁺ ion over a wide concentration range from 3.0×10^?7–3.1×10^?2 M. The lower detection limits are 1.0×10^?7 M Hg²⁺. The electrode has a fast response time (ca. 5 s), a satisfactory reproducibility and relatively long life time. The proposed sensor shows a fairly good selectivity toward Hg²⁺ ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 1.0–4.0. The proposed electrode was used as an indicator electrode in potentiometric titration of mercuric ion with standard solution of EDTA. The direct determination of mercury in spiked wastewater and an amalgam sample gave results that compare favorably with those obtained by the cold vapor atomic absorption spectrometric method.     

利用60%季铵化聚(4-乙烯)吡啶固定化酶的电位型尿素酶电极的研制

在电位型尿素酶电极的组装过程中，要求尽量不改变尿素酶的构型和构象，使其在酶膜中保持其自然状态，从而可获得较高的酶活力．用ｐＨ玻璃电极作原电极，将尿素酶固定在其表面，常用的有戊二醛交联法［１］和各种聚合物膜法［２～４］．本文利用６０％季铵化的聚（４－乙...     

Potentiometric flow-injection system for determination of alkaline phosphatase in human serum

A flow-injection system for detection of alkaline phosphatase (ALP) activity in human serum samples has been developed. As a specific and inexpensive ALP substrate for this kinetic assay monofluorophosphate (MFP) was applied. For detection of fluoride ions, generated in the course of the biocatalytic hydrolysis of MFP, conventional fluoride ion-selective electrode based on LaF₃-crystalline membrane was applied. After optimization the system allows analysis of human serum with high selectivity and relatively short time of analysis (5–6 samples h⁻¹). Volume of serum required for analysis is 0.05 mL. The system is useful for determination of the enzyme activity in human serum samples at physiological and pathological levels as well as for detection of isoenzymatic forms of ALP.     

Titration of Anionic Surfactants Using a New Potentiometric Sensor

Abstract

An anionic surfactant ion selective electrode has been developed by coating the Ru?i?ka Selectrode with plasticised polyvinyl chloride containing hyaminedodecylsulfate active substance. The electrode responds to dodecylsulfate, in the range 10^?2 ? 10^?2 mol dm^?3 and has been used for potentiometric titration of micromolar amounts of dodecylsulfate with an accuracy of 0.3%. The influence of several organic and inorganic anions has been investigated.     

Determination of Orciprenaline Using a Flow Injection Analysis System with Sequential Potentiometric and Spectrophotometric Detection

Abstract

This work describes an attempt to have a flow injection analysis (FIA) system for Orciprenaline with potentiometric and spectrophotometric detectors working sequentially. The potentiometric detection was performed using an orciprenaline ion-selective electrode made of orciprenaline ion-associate with phosphotungstic acid incorporated in a PVC matrix membrane, followed by sequential spectrophotometric detection of the same sample using the reaction of orciprenaline with phosphomolybdic acid in alkaline medium and measurement at 670 nm using a USB2000 fiber-optic spectrophotometer. The method was applied and validated for the assay of different samples that are 1.0 × 10^?2–1.0 × 10^?7 M orciprenaline, and the recovery values for Alupent® tablets, plasma and urine sample ranged from 99.39–100.93, 99.87–100.57, and 98.83–100.64 respectively for the potentiometric detector and 99.66–100.58, 99.78–100.69 and 99.12–100.92 respectively for the sequential spectrophotometric detector. It was found that using the double detection system compensated for both the unselectivity of the spectrophotometric method and the low detection limit of the potentiometric method (6.3 × 10^?4 M). Although two detectors were used in the measurements, the method is still very simple to design and apply, in addition to being rapid and less expensive than other more sophisticated techniques applied in the literature and can therefore be used for other pharmaceutical compounds as well.     

A Powder Based Polyaniline Carbon Paste Electrode for Urea Analysis

A new polyaniline carbon paste electrode prepared by mixing polyaniline (emeraldine), nafion, graphite powder and urease for urea analysis was exploited. The ratio of polyaniline, nafion, urease and graphite for the construction of the electrodes and the optimal conditions for urea determination were studied. The detection limit of this sensor for urea is 5 μM and the linearity from 5 μM to 7.5 mM is obtained in FIA. This sensor has a response time of 90s and shows good reproducibility and stability (RSD, 6.3%, n = 43). The blood samples from a patient during blood dialysis were taken and analyzed. The urea concentrations in blood obtained from this sensor are comparable with urea test kit method.     

A Potentiometric Method for Determination of Oxidized Ketone Bodies in Milk

Following the decarboxylation of acetoacetic acid by heating and the separation of acetone from milk matrix by steam distillation, acetone was allowed to react with bromine in the presence of nitric acid, causing the formation of bromoacetone and bromide; the latter was then quantified by means of a suitable ion-selective electrode applying the calibration principle. Based on checking reproducibility and on comparative analyses performed by a widely accepted photometric method, the potentiometric method developed was found to be adequate for the determination of the oxidized ketone bodies.     

Phenylboronic Acid‐Gold Nanoparticles for Potentiometric Detection of Saccharides

We propose a concept for the analytical application of gold nanoparticles modified by mercaptophenylboronic acid as a receptor of saccharides in a potentiometric sensor based on a conducting polymer.     

甲基紫电极催化动力学电位法测定亚硝酸根

基于在稀磷酸介质中亚硝酸根对溴酸钾氧化甲基紫的反应具有明显的催化作用 ,应用自制的甲基紫选择性电极跟踪反应液中甲基紫浓度的变化 ,建立了一种测定亚硝酸根的催化电位新方法。该方法在室温下进行 ,操作方便 ,样品溶液不受颜色限制。在选择的最佳条件下 ,检出限为 7 6× 1 0 -7g/L ,线性范围为8 0× 1 0 -7～ 8.0× 1 0 -5g/L。用于肉制品中亚硝酸根含量的测定 ,结果满意     

A Membrane Sensor for Selective Determination of Bisacodyl in Tablets

A novel PVC membrane sensor for bisacodyl based on bisacodyl‐phosphotungstate ion pair complex was prepared. The influence of membrane composition (i.e. percent of PVC, plasticizer, and ion‐pair complex), pH of test solution and foreign cations on the electrode performance were investigated. The optimized membrane demonstrates Nernstian response (60.3 ± 2.1 mV per decade) for bisacodyl cations over a wide linear range from 8.0 × 10^?5 to 5.0 × 10^?3 M at 25 °C. The potentiometric response is independent from the pH of the solution in the pH range of 1.5–3.5. The proposed sensor has the advantages of easy preparation, good selectivity, fast response time, and small interferences from hydrogen ions. It was successfully used for determination of bisacodyl in tablets, and the results obtained with the electrode were in good agreement with the official chromatographic method.