Assessment of Potassium Zinc Ferrocyanide as an Alkali-Metal Ion-Exchanger in Ion-Selective Electrodes

Abstract

Silicone rubber membranes containing potassium zinc ferrocyanide have been assessed as ion-selective electrode sensors for the determination of alkali metal ions. The slope of the calibration graph for potassium ion is 59 mV per decade change in concentration within the concentration range 5 × 10^?4 to 10^?1 M at 25°C. Selectivity constants (K_K + _/M+)are 9. 5, Cs⁺; 3. 3, Rb⁺; 0. 025, Na⁺; 0. 003, Li⁺; and 1.8, NH₄ ⁺, calculated from potential data obtained at 10^?1 M concentrations of each ion separately. Similar membranes prepared from PVC responded similarly with a slight improvement in selectivity.     

A New Comparative Potentiometric Method for Analysis of Omarigliptin Using Three Different Sensors

This work represents first attempt for potentiometric determination of the most recent antidiabetic; omarigliptin. Three sensors, employing potassium tetrakis (p-chlorophenyl) borate as a lipophilic cation exchanger, were developed and compared. One liquid contact ion-selective electrode and two carbon paste-based solid contact ones, plain one and another one modified with polyaniline nanoparticles, were employed. Performances of fabricated sensors were assessed as per IUPAC recommendations. Incorporation of hydrophobic polyaniline nanoparticles as ion-to-electron transducer layer at solid contact/ion-sensitive membrane interface enhanced sensitivity and stability of the third sensor showing LOD of 2.5×10⁻⁷ mol L⁻¹ and slope of 58.57 mV decade⁻¹. The three sensors were applied for omarigliptin determination in presence of its degradation products, in dosage form and spiked human plasma.     

Two Thiourea-based Colorimetric Sensors for Anions: Structure and Binding Study

Two colorimetric thiourea-based chemsensors with two relatively rigid arms, 2A and 2B, were synthesized. Their binding abilities with halide anions, AcO^?, [Formula: See Text] were studied by UV-Vis spectroscopy in DMSO. The two sensors showed a notable selective color response to F^? anion from colorless to green-yellow in recognition. The structures of the two sensors and their binding behaviors are discussed. The association constants were calculated by nonlinear fittings of 1:1, 1:2 or 1:1 to 1:2.     

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.     

Novel Zn-Fe LDH/MWCNTs and Graphene/MWCNTs Nanocomposites Based Potentiometric Sensors for Benzydamine Determination in Biological Fluids and Real Water Samples

Two sensitive and selective potentiometric sensors based on zinc-iron layered double hydroxides/multiwalled carbon nanotubes (Zn−Fe LDH/MWCNTs) (sensor I) and graphene/multiwalled carbon nanotubes (Gr/MWCNTs) (sensor II) nanocomposites were developed for benzydamine hydrochloride (Benz) determination. The investigated sensors displayed excellent Nernstian slopes 58.5±0.7 and 59.5±0.5 mV decade⁻¹, detection limits 8.3×10⁻⁷ and 1.9×10⁻⁷ mol L⁻¹, long lifetimes, adequate selectivity, high chemical, and thermal stability within pH range of 2.4–8.5 for sensors І and ІІ, respectively. The surface morphology of sensors was analyzed using a Transmission Electron Microscope (TEM). The analytical method was efficiently implemented for Benz determination in biological fluids and surface water samples.     

A dual-fluorophore sensor approach for ratiometric fluorescence imaging of potassium in living cells

Potassium is the most abundant intracellular metal in the body, playing vital roles in regulating intracellular fluid volume, nutrient transport, and cell-to-cell communication through nerve and muscle contraction. On the other hand, aberrant alterations in K⁺ homeostasis contribute to a diverse array of diseases spanning cardiovascular and neurological disorders to diabetes to kidney disease to cancer. There is an unmet need for studies of K⁺ physiology and pathology owing to the large differences in intracellular versus extracellular K⁺ concentrations ([K⁺]_intra = 150 mM, [K⁺]_extra = 3–5 mM). With a relative dearth of methods to reliably measure dynamic changes in intracellular K⁺ in biological specimens that meet the dual challenges of low affinity and high selectivity for K⁺, particularly over Na⁺, currently available fluorescent K⁺ sensors are largely optimized with high-affinity receptors that are more amenable for extracellular K⁺ detection. We report the design, synthesis, and biological evaluation of Ratiometric Potassium Sensor 1 (RPS-1), a dual-fluorophore sensor that enables ratiometric fluorescence imaging of intracellular potassium in living systems. RPS-1 links a potassium-responsive fluorescent sensor fragment (PS525) with a low-affinity, high-selectivity crown ether receptor for K⁺ to a potassium-insensitive reference fluorophore (Coumarin 343) as an internal calibration standard through ester bonds. Upon intracellular delivery, esterase-directed cleavage splits these two dyes into separate fragments to enable ratiometric detection of K⁺. RPS-1 responds to K⁺ in aqueous buffer with high selectivity over competing metal ions and is sensitive to potassium ions at steady-state intracellular levels and can respond to decreases or increases from that basal set point. Moreover, RPS-1 was applied for comparative screening of K⁺ pools across a panel of different cancer cell lines, revealing elevations in basal intracellular K⁺ in metastatic breast cancer cell lines vs. normal breast cells. This work provides a unique chemical tool for the study of intracellular potassium dynamics and a starting point for the design of other ratiometric fluorescent sensors based on two-fluorophore approaches that do not rely on FRET or related energy transfer designs.

We report a dual-fluorophore approach for ratiometric fluorescent imaging of K⁺ levels in live cells. Intracellular esterases cleave RPS-1 to detach the K⁺-responsive fluorophore (PS525) from its internal standard (Coumarin 343).     

Application of Precipitation-based and Nanoparticle-based Techniques for Fabrication of Potentiometric Sensors for Nano Molar Determination of Chitosan and Polyvinyl Pyrrolidone in Pharmaceutical Formulations and Biological Fluids

Chitosan (CH) is one of the most abundant biopolymers with multiple applications. Polyvinyl pyrrolidone (PVP) has specific binding and detoxification properties that are of great interest in health care. Hence, it arises a crucial urge to develop economic sensors to analyze CH and PVP in pharmaceutical formulations and biological samples. Two portable sensors were fabricated using precipitation-based technique, and nanoparticles-based technique, for determination of CH and PVP in sensor 1 and 2; respectively. Linear responses of 10⁻⁵ to10⁻⁷ M and 10⁻² to10⁻⁷ M at pH 3.6–4.8 and 7.2–8.4, with ideal Nernstian slopes of 60.00 and 59.83 mV /decade, and nanomolar LODs of 94.90 and 81.20 nM were observed for CH and PVP; respectively. The percentage recoveries were 100.40±1.03 and 100.19±0.64 for sensors 1 and 2; respectively. Both sensors were successfully applied in biological fluids without pre-treatment. Accurate results were obtained using sensor 1, in pure form, pharmaceutical formulations, human plasma, rat liver and rat brain, as well as sensor 2, in pure form, pharmaceutical formulations and urine samples. The results were statistically compared with the reported methods and no significant difference was observed.     

Synthesis of Novel 2-Iminothiazolidin-4-ones

Abstract

Thiazolidin-4-ones are known to exhibit diverse biological activities such as antimicrobial, anticancer, antidiarrheal, anticonvulsant, antidiabetic, antihistaminic, and antifungal activities. In the present investigation, a series of 2-haloacetamides was prepared by reacting chloroacetyl chloride with amines in dry benzene under reflux conditions. The formed 2-haloacetamides reacted with potassium thiocyanate in refluxing dry acetone to afford new 2-iminothiazolidin-4-ones. The 5-arylidene-2-imino-3 (napthalen-2yl)-thiazolidin-4-ones were prepared by condensing 2-iminothiazolidin-4-ones with substituted benzaldehydes. All the products were characterized by infrared, mass, and ¹H and ¹³C NMR techniques.     

Disposable Stochastic Dot Sensors for the Assay of Ascorbic Acid in Pharmaceutical Samples,Beverages, and Biological Fluids

Eight disposable stochastic dot sensors based on porphyrins and modified diamond or carbon pastes were employed for the assay of ascorbic acid in pharmaceutical, beverages, and biological samples. The advantage of using such sensors for the assay of ascorbic acid is the possibility of qualitative and quantitative assay of ascorbic acid in one run of the experiment. The covered linear concentration range for these sensors was between 10^?14 and 10^?5 mol/L with high sensitivities. The proposed dot sensors were used reliably (RSD < 1%) for the assay of ascorbic acid from different samples for more than 6 months, with a recovery higher than 92.00%.     

微波辐射合成N-(2-氯-1-氧-5-吡啶甲基)二甲酰亚胺类化合物和生物活性研究

以二甲酰亚胺钾3a～3g与2-氯-5-氯甲基吡啶的N原子氧化后得到的2-氯-1-氧-5-氯甲基吡啶发生亲核取代反应, 用传统和微波两种方法合成了7种未见文献报到的化合物N-(2-氯-1-氧-5-吡啶甲基)二甲酰亚胺类化合物4a～4g. 对比两种合成方法, 在常压下, 微波辐射作为反应热源具有用时少、环境友好、易纯化和产率高的特点. 这些目标化合物4a～4g的结构经元素分析结果, IR, GC-MS, ¹H NMR, ¹³C NMR确证. 初步的生物活性测定结果表明, N-(2-氯-1-氧-5-吡啶甲基)二甲酰亚胺类部分化合物具有良好的杀虫活性.     

Sulfonamides as Ionophores for Ise. III. Guanidinium Ion-Selective Electrodes Based on Lipophilic Bis-Sulfonamide Podands

Abstract

PVC membrane ion-selective electrodes based on bis-sulfonamide podands and DOS (Bis(2-ethylhexyl)-sebacate) as plasticizer are described. They were found to behave as guanidinium ion sensors, exhibiting high selectivity for guanidinium ions over potassium ions.     

Application of Membrane-Selective Electrodes for the Determination of Pioglitazone Hydrochloride in the Presence of Its Acid Degradant or Metformin Hydrochloride in Tablets and Plasma

Abstract

Polyvinyl chloride (PVC) membrane sensors for the determination of pioglitazone hydrochloride (PIO) and metformin hydrochloride (MET) were described by using the ion association complexes between these drugs with either sodium tetraphenyl-borate (TPB) or ammonium reineckate (RNC) counter ions. The performance characteristics of the sensors were evaluated according to IUPAC recommendations, reveal a fast, stable and linear response over the concentration range 3.162 × 10^?5 ? 1 × 10^?2 M for PIO and 1 × 10^?3 ? 1 × 10^?1 M for MET. The sensors are used for determination of PIO and MET in tablets and plasma. The developed method was found to be simple, accurate and precise when compared with the reported method.     

A Highly Selective Potassium Sensor for the Detection of Potassium in Living Tissues

The development of highly selective sensors for potassium is of great interest in biology. Two new hydrosoluble potassium sensors (Calix‐COU‐Alkyne and Calix‐COU‐Am) based on a calix[4]arene bis(crown‐6) and an extended coumarin were synthesized and characterized. The photophysical properties and complexation studies of these compounds have been investigated and show high molar extinction coefficients and high fluorescence quantum yields. Upon complexation with potassium in the millimolar concentration range, an increase of one‐ and two‐photon fluorescence emission is detected. A twofold fluorescence enhancement is observed upon excitation at λ=405 nm. The ligands present excellent selectivity for potassium in the presence of various competitive cations in water and in a physiological medium. The photophysical properties are not affected by the presence of a large amount of competing cations (Na⁺, Ca²⁺, Mg²⁺, etc.). Ex vivo measurements on mouse hippocampal slices show that Calix‐COU‐Alkyne accumulates extracellularly and does not alter the neuronal activity. Furthermore, the sensor can be utilized to monitor slow extracellular K⁺ increase induced by inhibition of K⁺ entry into the cells.     

Screen-printed electrochemical sensors for label-free potentiometric and impedimetric detection of human serum albumin

Herein, two electrochemical methods based on potentiometric and impedimetric transductions were presented for albumin targeting, employing screen-printed platforms (SPEs) to make easy and cost-effective sensors with good detection merits. The SPEs incorporated ion-to-electron multi-walled carbon nanotubes (MWCNTs) transducer. Sensors were constructed using either tridodecyl methyl-ammonium chloride (TDMACl) (sensor I) or aliquate 336S (sensor II) in plasticized polymeric matrices of carboxylated poly (vinyl chloride) (PVC-COOH). Analytical performances of the sensors were evaluated using the above-mentioned electrochemical techniques. For potentiometric assay, constructed sensors responded to albumin with −81.7 ± 1.7 (r² = 0.9986) and −146.2 ± 2.3 mV/decade (r² = 0.9991) slopes over the linearity range 1.5 μM–1.5 mM with 0.8 and 1.0 μM detection limits for respective TDMAC- and aliquate-based sensors. Interference study showed apparent selectivity for both sensors. Impedimetric assays were performed at pH = 7.5 in 10 mM PBS buffer solution with a 0.02 M [Fe(CN)₆]^−3/−4 redox-active electrolyte. Sensors achieved detection limits of 4.3 × 10⁻⁸ and 1.8 × 10⁻⁷ M over the linear ranges of 5.2×10⁻⁸–1.0×10⁻⁴ M and 1.4×10⁻⁶–1.4×10⁻³ M, with 0.09 ± 0.004 and 0.168 ± 0.009 log Ω/decade slopes for sensors based on TDMAC and aliquate, respectively. These sensors are characterized with simple construction, high sensitivity and selectivity, fast response time, single-use, and cost-effectiveness. The methods were successfully applied to albumin assessment in different biological fluids.     

Fabrication and Characterization of Novel Salicylic Acid Sensors Using Different Reagents (Ferric and Copper)

Abstract

Fabrication of optical fiber salicylic acid (SA) sensors based on immobilization of ferric(III) nitrate and copper(II) acetate on Dowex‐50x8 is presented in this paper. The SA forms a stable purple complex with immobilized Fe³⁺ at pH 2.1 with a response time of 10 min while it forms a stable yellowish green complex with immobilized Cu²⁺ at pH 6.5 with a response time of 8 min. The reflectance spectra of the sensors were measured by using an optical fiber spectrophotometer. The results showed these SA sensors have maximum reflectance at 786 nm and 725 nm for SAFe complex and SACu complex, respectively. The useful dynamic response ranges are 0.02–0.50 g/L (SAFe) and 0.40–1.40 g/L (SACu). These complexes are stable for more than 24 hours. A good reproducibility (0.90%— SAFe; 0.86%— SACu) of measurement was obtained with these sensors.     

Carbon dots as a fluorescent probe for label-free detection of physiological potassium level in human serum and red blood cells

A unique photoluminescence carbon dots (CDs) with larger size were prepared by microwave-assisted method. Complex functional groups on the surface of the CDs facilitate the nanoparticles to form affinity with some metal ions. Taking advantage of the effective fluorescence quenching effect of K⁺, a highly sensitive CD-based fluorescence analytical system for label-free detection of K⁺ with limit of detection (LOD) 1.0 × 10⁻¹² M was established. The concentrations of potassium ion in biological samples such as human serum are usually found at millimolar levels or even higher. The proposed method begins with a substantial dilution of the sample to place the K⁺ concentration in the dynamic range for quantification, which covers 3 orders of magnitude. This offers some advantages: the detection of K⁺ only needs very small quantities of biological samples, and the dilution of samples such as serum may effectively eliminate the potential interferences that often originate from the background matrix. The determined potassium levels were satisfactory and closely comparable with the results given by the hospital, indicating that this fluorescent probe is applicable to detection of physiological potassium level with high accuracy. Compared with other relative biosensors requiring modified design, bio-molecular modification or/and sophisticated instruments, this CD-based sensor is very simple, cost-effective and easy detection, suggesting great potential applications for successively monitoring physiological potassium level and the change in biological system.     

酰腙类化合物的合成和阴离子识别研究

本文设计合成了3种新型的酰腙类受体分子。利用紫外-可见吸收光谱及 ¹H NMR考察了其与F^-、Cl^-、Br^-、I^-、CH₃COO^-、HSO₄^-、NO₃^-等阴离子的作用。结果表明，该类受体分子能较好地识别阴离子F^-和CH₃COO^-，在DMSO溶液中主客体之间形成氢键加合物。尤其对于受体3(间苯双对硝基苯氧乙酰腙)，加入F^-和CH₃COO^-时，溶液颜色有明显变化，受体3对这两种阴离子可实现裸眼识别。     

Halogen-Substituted Cyclotrigermenes: The π(Ge = Ge)-σ*(Ge–X) Interaction and a Unique Dynamic Behavior

Abstract

The halogen-substituted cyclotrigermenes (^tBu₃Si)₃Ge₃X (X = F, Cl, Br, I) (2) were synthesized by the reaction of tris(tri-tert-butylsilyl)cyclotrigermenylium tetrakis(2,3,5,6-tetrafluorophenyl)borate) (1 ⁺?TTFPB^?) with potassium halides (KF, KCl, KBr, KI). Intramolecular halogen migration over the three-membered ring skeleton was observed in the solution.

GRAPHICAL ABSTRACT     

Improved Enzyme Electrode for Amygdalin

Abstract

A new variant of enzymatic electrode for amygdalin is described. It consists of a cyanide-selective membrane electrode on whose; surface a dialysis membrane is fixed which contains covalently immobilized β-glucosidase. The sensor thus achieved ensures improved response characteristics over similar sensors mentioned in literature. Its response to amygdalin is linear within 10^?1 ? 10^?5 moles/1; the response time is smaller and the stability is higher than those of similar sensors described in literature.     

Potassium selective chromoionophores

The ionisable chromoionophores5 were synthesised from simple precursors. These chromoionophores extract alkali metal cations from aqueous solutions at pH > 7 into dichloromethane. The ratio of extraction coefficients for the chromoionophore5c for K⁺ and Na⁺ indicate that it has potential for use in optical fibre sensors for K⁺ in the presence of Na⁺, Mg²⁺ and Ca²⁺ at extracellular concentrations.This paper is dedicated to the memory of the late Dr C. J. Pedersen.