Sodium Ion-selective Electrode Research Articles

Improved performance of Prussian blue solid contact allowing flow injection amperometric detection of potassium ions in the excess of sodium

Catalytically synthesized Prussian blue nanoparticles are a versatile solid contact for potassium and sodium ion-selective screen-printed electrodes. The cathodic peak current proportional to cation concentration was registered in flow injection amperometry regime. The ability of K+ to penetrate Prussian blue lattice resulted in 2–4-fold higher response to potassium ions relatively to sodium ions. Such intrinsic selectivity of Prussian blue to potassium provided an order of magnitude higher sensitivity of K+-selective electrodes in comparison to Na+-sensors, based on nanoparticles covered with the corresponding ion-selective membranes. In contrast to other known solid contacts, Prussian blue provides the highest sensitivity of potassium-selective electrodes in an amperometric regime (20–50 mA·cm−2·M−1). Moreover, 1 × 10-6 M is the lowest limit of detection ever achieved for Prussian blue-based ion-selective electrodes. The improved sensitivity and selectivity allowed flow injection amperometric detection of potassium ions in the presence of interfering ions. Despite K+ concentration is approximately 40-fold lower than Na+, sensors are applicable for detection of pathological and normal potassium and sodium ions in blood serum. The sensors designed in this work have opened a new opportunity for analyzing biological fluids with ion-selective electrodes in an amperometric regime.

Ion-Electron Transduction Layer of the SnS2-MoS2 Heterojunction to Elevate Superior Interface Stability for All-Solid Sodium-Ion Selective Electrode.

The high selectivity and fast ion response of all-solid sodium ion selective electrodes were widely applied in human sweat analysis. However, the potential drift due to insufficient interfacial capacitance leads to the deterioration of its stability and ultimately affects the potential accuracy of ion analysis. Designing a novel ion-electron transduction layer between the electrode and the ion selective membrane is an effective method to stabilize the interfacial potential. Herein, the SnS2-MoS2 heterojunction material was constructed by doping Sn in MoS2 nanosheets and used as the ion electron transduction layers of an all-solid sodium ion selective electrode for the first time, achieving the stable and efficient detection of Na+ ions. The proposed electrode exhibited a Nernst slope of 57.86 mV/dec for the detection of Na+ ions with a detection limit of 10-5.7 M in the activity range of 10-6-10-1 M. Via the electronic interaction at the heterojunction interfaces between SnS2 and MoS2 materials, the micro-nanostructure of the SnS2-MoS2 heterojunction was changed and SnS2-MoS2 as the ion-electron transduction layer acquired excellent capacitance (699 μF) and hydrophobicity (132°), resulting in a long-term potential stability of 1.37 μV/h. It was further proved that the large capacitance and high hydrophobicity of the ion-electron transduction layer are primary reasons for the excellent stability of the all-solid sodium ion selective electrode toward Na+ ions.

Finding a perfect match of ion-exchanger and plasticizer for ion-selective sensors

Application of neutral ionophore based ion-selective sensors requires presence of ion-exchanger in the receptor phase, silently assuming that it is not only soluble but also dissociates to ions in the applied plasticizer. Although for typically applied ion-selective membrane constituents (plasticizers - ion-exchanger pairs) dissociation of ion-exchangers to ions is proven by theoretical (or close to) performance of resulting sensors, search for alternative plasticizers or ion-exchangers requires a method allowing estimation of the match of properties of involved compounds. In this work we propose a simple optical approach allowing estimation of ion-exchanger interactions with plasticizer. The results were confirmed by conductivity studies of model plasticizers solutions. The estimated dissociation constants of model ion-exchangers in plasticizers used are in excellent agreement with the results of optical studies. It was shown that solubility coupled with poor dissociation to ions of ion-exchanger affects performance of the resulting ion-selective membrane. Rational choice of properties of ion-exchanger and plasticizer allows finding a perfect match of the two, that results in improvements in performance of sensors (e.g. detection limits). As model sensors potassium and sodium ion-selective electrodes with poly(vinyl chloride) (PVC) based membranes, plasticized with classical plasticizer bis(2-ethylhexyl sebacate) or biodegradable alternative acetyl tributyl citrate, were prepared and studied using selected ion-exchangers.

Potentiometric Chemical Sensors Based on Metal Halide Doped Chalcogenide Glasses for Sodium Detection.

Chalcogenide glasses are widely used as sensitive membranes in the chemical sensors for heavy metal ions detection. The lack of research work on sodium ion-selective electrodes (Na+-ISEs) based on chalcogenide glasses is due to the high hygroscopicity of alkali dopes chalcogenides. However, sodium halide doped Ga2S3-GeS2 glasses are more chemically stable in water and could be used as Na+-sensitive membranes for the ISEs. In this work we have studied the physico-chemical properties of mixed cation (AgI)x(NaI)30-x(Ga2S3)26(GeS2)44 chalcogenide glasses (where x = 0, 7.5, 15, 22.5 and 30 mol.% AgI) using density, DSC, and conductivity measurements. The mixed cation effect with shallow conductivity and glass transition temperature minimum was found for silver fraction r = Ag/(Na + Ag) ≈ 0.5. Silver addition decreases the moisture resistance of the glasses. Only (AgI)22.5(NaI)7.5(Ga2S3)26(GeS2)44 composition was suitable for chemical sensors application, contrary to the single cation sodium halide doped Ga2S3-GeS2 glasses, where 15 mol.% sodium-halide-containing vitreous alloys are stable in water solutions. The analytical parameters of (NaCl)15(Ga2S3)23(GeS2)62; (NaI)15(Ga2S3)23(GeS2)62 and (AgI)22.5(NaI)7.5(Ga2S3)26(GeS2)44 glass compositions as active membranes in Na+-ISEs were investigated, including detection limit, sensitivity, linearity, ionic selectivity (in the presence of K+, Mg2+, Ca2+, Ba2+, and Zn2+ interfering cations), reproducibility and optimal pH-range.

Characterization of the key taste compounds during bread oral processing by instrumental analysis and dynamic sensory evaluation

The process of taste release and perception during chewing bread was investigated using high-performance liquid chromatography and sodium ion-selective electrode analysis combined with dynamic sensory evaluation. The result of the dynamic quantitative descriptive analysis and temporal dominance of sensation elucidated that sour, salty, and sweet tastes were significantly (P < 0.05) changed during oral processing. The salty taste was the dominant taste at the initial stage of chewing, whereas the sweet taste took the dominant place after 7 s. Seventeen taste-active compounds with the taste activity value more than 1 were identified. According to partial least squares regression analysis, 9 taste compounds were detected as the potent taste compounds contributing to changes in the taste perception during bread oral processing. Malic acid, succinic acid, sodium chloride, valine, and sucrose were confirmed as the key taste compounds contributing to bread oral processing through addition experiments. Malic acid had a stronger enhancing ability of sour and salty perception than succinic acid but weaker inhibition ability to decrease sweet perception than succinic acid.

Mean Ionic Activity Coefficients of NaBr in the Ternary System NaBr–SrBr2–H2O at 288.15 K using the Cell Potential Method

In this paper, a sodium ion selective electrode (Na-ISE) and a bromide ion selective electrode (Br-ISE) were used to form a liquid-free potential reversible battery: Na-ISE|NaBr (m1) and SrBr2 (m2)...

Printed Wearable Sensor Patch for Multi-Analytes Detection in the Sweat Range

Printed Wearable Sensor Patch for Multi-Analytes Detection in the Sweat Range

P.233 Doxycycline attenuates anxiety and microglia activation induced by repeated lipopolysaccharide

Sodium hyodeoxycholate (NaHDC) is the main component of hog bile salts, which play a role in the absorption of sparingly soluble materials in the intestinal solution. The biosurfactant has an amphiphilic molecular structure, similar to that of ursodeoxycholate from bear gallbladder. Micelle formation from hyodeoxycholate was studied at 308.2 K using pyrene fluorescence probe to determine critical micelle concentrations (cmc) at various NaCl concentrations. The change in the fluorescence spectrum peak ratios with NaHDC concentration indicated two steps for bile salt aggregation. The first step was the formation of small micelles (cmc) at 5 mM, and the second step was the formation of stable aggregates at 14 mM in aqueous solution. The aggregation of hyodeoxycholate, analyzed using the stepwise association model, was found to grow its aggregation number from 4 to 7 with increasing concentration. The aggregation number in aqueous solution was also confirmed by the static light scattering method. The average measured aggregation number of the micelles was 6.7. The micellar size was relatively small as measured by either method, but it was covered by general aggregation number of human bile salts. The degree of counterion binding to the micelles, determined using a sodium ion-selective electrode, was ca. 0.5 for the NaHDC micelles. This value was relatively high among typical bile salts. Moreover, the solubilization capacity of the NaHDC micelles was assessed using cholesterol. It became clear that NaHDC micelles hardly solubilized cholesterol compared to typical human bile salts. The maximum solubilization by NaHDC was equivalent only to that by sodium ursodeoxycholate

레이저 유도 그래핀 기반 나트륨, 칼륨 이온 선택성 전극 개발

레이저 유도 그래핀 기반 나트륨, 칼륨 이온 선택성 전극 개발

Control of the colloidal depletion force in nonionic polymer solutions by complexation with anionic surfactants

HypothesisCharge, size and concentration of depletants control the magnitude and range of depletion and structural forces. Noncovalent association of nonionic polymers with ionic surfactants may therefore synergistically enhance these forces to an extent that depends on the structure and composition of the resulting complexes. ExperimentsForces were measured between a silica sphere and a silica plate in solutions of Pluronic F108 nonionic poly(ethylene oxide – block – propylene oxide – block – ethylene oxide) triblock copolymers and anionic sodium dodecylsulfate (SDS) surfactants using colloidal probe atomic force microscopy as a function of polymer, surfactant and NaCl background electrolyte concentrations. Trends in the magnitudes of the depletion attraction minimum and the first repulsive maximum in the oscillatory structural force were interpreted with the aid of pyrene solubilization assays, sodium ion-selective electrode analysis, and dynamic light scattering measurements that characterized the formation, charge, and hydrodynamic radius of F108/SDS complexes respectively. FindingsSynergistic enhancement of the depletion force and first repulsive maximum occurred within a finite range of SDS concentrations, to an extent that depended on F108 and NaCl concentrations. This was due mainly to charging of F108/SDS complexes. Size effects were important at low NaCl concentration. Forces measured above the synergistic SDS concentration range were indistinguishable from those in polymer-free SDS solutions due to the appearance of excess unbound SDS micelles.

Solid-State Planar Reference Electrode With Ion-Selective Electrodes for Clinical Diagnosis

A solid-state planar reference electrode (SSPRE) was fabricated and evaluated using polymer membrane, comprising polyvinyl chloride-co-polyvinyl acetate, nitrophenyl octyl ether as plasticizer, and potassium tetraphenylborate as anion blocker, and was used for the fabrication of SSPRE. Screen-printed Ag/AgCl electrode was used as the base electrode for the fabrication of SSPRE and was evaluated in background electrolyte solutions containing KNO3/KCl and was observed that there was no significant potential dependence on anions present in the background electrolyte. Furthermore, SSPRE was tested using a series of cations and anions in solution and varying pH of the background electrolyte with respect to commercial Ag/AgCl with 0.1 M KCl reference electrode. It was noted that the SSPRE provided stable potential by tuning the design of the screen-printed electrodes and the membrane potential. The reference potential does not differ in various background electrolyte solutions, except thiocyanate, which gave a negative shift at high concentration, ca. 0.1 M. Furthermore, the SSPRE was integrated with screen-printed potassium and sodium ion-selective electrodes, and was tested, and the performance was evaluated.

All-Solid-State Sodium-Selective Electrode with a Solid Contact of Chitosan/Prussian Blue Nanocomposite.

Conventional ion-selective electrodes with a liquid junction have the disadvantage of potential drift. All-solid-state ion-selective electrodes with solid contact in between the metal electrode and the ion-selective membrane offer high capacitance or conductance to enhance potential stability. Solution-casted chitosan/Prussian blue nanocomposite (ChPBN) was employed as the solid contact layer for an all-solid-state sodium ion-selective electrode in a potentiometric sodium ion sensor. Morphological and chemical analyses confirmed that the ChPBN is a macroporous network of chitosan that contains abundant Prussian blue nanoparticles. Situated between a screen-printed carbon electrode and a sodium-ionophore-filled polyvinylchloride ion-selective membrane, the ChPBN layer exhibited high redox capacitance and fast charge transfer capability, which significantly enhanced the performance of the sodium ion-selective electrode. A good Nernstian response with a slope of 52.4 mV/decade in the linear range from 10−4–1 M of NaCl was observed. The stability of the electrical potential of the new solid contact was tested by chronopotentiometry, and the capacitance of the electrode was 154 ± 4 µF. The response stability in terms of potential drift was excellent (1.3 µV/h) for 20 h of continuous measurement. The ChPBN proved to be an efficient solid contact to enhance the potential stability of the all-solid-state ion-selective electrode.

Determination of Solubility of Sodium Salts in Aqueous Surfactant and STPP Solutions Using an Ion Selective Electrode

Solubility of inorganic salts in the mixed systems containing surfactants and sodium tripolyphosphate (STPP) is very important for the production of laundry detergents. In this work we explored the solubility of NaCl, Na2SO4, and Na2CO3 in aqueous surfactant and STPP solutions using an ion selective electrode at 298.15 K. In the experiments, electromotive forces (EMF) for the ternary systems were measured using an ion-meter with a sodium ion-selective composite electrode and the relationship between the solubility and EMF was analyzed by a potentiometric analysis. The proposed method has advantages in avoiding the solid–liquid separation operation and solution supersaturation. The experimental results indicated that the salting-out effect caused by surfactant and STPP can decrease the solubility of sodium salts in the aqueous systems.

Determination and Modeling of Activity Coefficients of Sodium Chloride in (Glycerol + Water) Mixtures Based on Potentiometric Measurements

In this work, the results concerning to the mean activity coefficient measurements for NaCl in the (glycerol + water) system using the potentiometric method are reported. The potentiometric measurements were performed on the galvanic cells without liquid junction of the type: Ag|AgCl|NaCl (m), glycerol (wt%), H2O (1 - wt)%|Na-ISE, in various mixed solvent systems containing 0, 5, 10, 20 and 30 mass fraction percents of glycerol over ionic strength ranging from 0.0020-3 mol kg-1 at T = 298.2 K. The sodium ion selective electrode and Ag-AgCl electrode as self-made electrodes had a reasonably Nernst response. The modified zeolite was used to fabricate the sodium ion selective electrode as electrochemical sensor. The modeling of the investigated system was made based on an extended Debye-Huckel equation, the Pitzer and Pitzer-Simonson-Clegg models. The unknown parameters were determined for each model. The resulting values of the mean activity coefficients, osmotic coefficients and excess Gibbs energy are reported for the studied system.

An Integrated Glucose Sensor with an All-Solid-State Sodium Ion-Selective Electrode for a Minimally Invasive Glucose Monitoring System

We developed a minimally invasive glucose monitoring system that uses a microneedle to permeate the skin surface and a small hydrogel to accumulate interstitial fluid glucose. The measurement of glucose and sodium ion levels in the hydrogel is required for estimating glucose levels in blood; therefore, we developed a small, enzyme-fixed glucose sensor with a high-selectivity, all-solid-state, sodium ion-selective electrode (ISE) integrated into its design. The glucose sensor immobilized glucose oxidase showed a good correlation between the glucose levels in the hydrogels and the reference glucose levels (r &gt; 0.99), and exhibited a good precision (coefficient of variation = 2.9%, 0.6 mg/dL). In the design of the sodium ISEs, we used the insertion material Na0.33MnO2 as the inner contact layer and DD16C5 exhibiting high Na+/K+ selectivity as the ionophore. The developed sodium ISE exhibited high selectivity (\( \log \,k^{pot}_{Na,K} = -2.8\)) and good potential stability. The sodium ISE could measure 0.4 mM (10−3.4 M) sodium ion levels in the hydrogels containing 268 mM (10−0.57 M) KCl. The small integrated sensor (ϕ &lt; 10 mm) detected glucose and sodium ions in hydrogels simultaneously within 1 min, and it exhibited sufficient performance for use as a minimally invasive glucose monitoring system.

Micelle formation of sodium hyodeoxycholate

Sodium hyodeoxycholate (NaHDC) is the main component of hog bile salts, which play a role in the absorption of sparingly soluble materials in the intestinal solution. The biosurfactant has an amphiphilic molecular structure, similar to that of ursodeoxycholate from bear gallbladder. Micelle formation from hyodeoxycholate was studied at 308.2K using pyrene fluorescence probe to determine critical micelle concentrations (cmc) at various NaCl concentrations. The change in the fluorescence spectrum peak ratios with NaHDC concentration indicated two steps for bile salt aggregation. The first step was the formation of small micelles (cmc) at 5mM, and the second step was the formation of stable aggregates at 14mM in aqueous solution. The aggregation of hyodeoxycholate, analyzed using the stepwise association model, was found to grow its aggregation number from 4 to 7 with increasing concentration. The aggregation number in aqueous solution was also confirmed by the static light scattering method. The average measured aggregation number of the micelles was 6.7. The micellar size was relatively small as measured by either method, but it was covered by general aggregation number of human bile salts. The degree of counterion binding to the micelles, determined using a sodium ion-selective electrode, was ca. 0.5 for the NaHDC micelles. This value was relatively high among typical bile salts. Moreover, the solubilization capacity of the NaHDC micelles was assessed using cholesterol. It became clear that NaHDC micelles hardly solubilized cholesterol compared to typical human bile salts. The maximum solubilization by NaHDC was equivalent only to that by sodium ursodeoxycholate

Thermodynamic properties determination of ternary mixture (NaCl + Na2HPO4 + water) using potentiometric measurements

In this work, the thermodynamic properties of the ternary mixed electrolyte system (NaCl+Na2HPO4+water), using the potentiometric method, are reported. The potentiometric measurements were performed on the galvanic cells without liquid junction of the type: Ag–AgCl|NaCl (m1), Na2HPO4 (m2), H2O|Na-ISE, over total ionic strengths from (0.0130 to 4.000)mol·kg−1 for different series of salt molal ratios r (r=mNaCl/mNa2HPO4=2.5, 5.0, 7.5, and 10.0) and pure NaCl in aqueous system at T=298.2. The PVC based sodium ion selective electrode (Na-ISE) and Ag–AgCl electrode used in this work were prepared in our laboratory and had a reasonably Nernst response. The activity coefficient results were interpreted based on the Harned rule and Pitzer model. The unknown Pitzer mixing interaction parameters (θClHPO4, ψNaClHPO4) were evaluated for the ternary system studied according to Pitzer graphical method .Then, the parameters obtained with the Pitzer model were used to calculate the values of the mean activity coefficients of Na2HPO4, the osmotic coefficients, the solvent activity and the excess Gibbs free energy for the whole series of the studied mixed electrolyte system.

The associations of macrocyclic ethers with cations in 1,4-dioxane/water mixtures; potentiometric Na+ and K+ binding measurements and computational study

This paper deals with the study of different degrees of association constants of Na+ and K+ ions with macrocycles of [12]crown-4, [15]crown-5, [18]crown-6, and Diaza[18]crown-6 in (1:1)dioxane/water mixture using the sodium and potassium ion selective electrodes (ISE). The gas phase molecular mechanical and quantum chemical calculations of [18]crown-6 and diaza[18]crown-6 were performed at MM+, AM1, MINDO/3, HF/6-31G(d), and B3LYP/6-31G(d) levels with the help of Gaussian03 program. Conformational abilities were compared with the ion binding results of ISE measurements. The results were also discussed in terms of oxygen charges and enthalpy stabilized association mechanism.

Ion-specific and charge effects in counterion binding to poly(styrenesulfonate) anions

In order to obtain a deeper insight into effects occurring when an electrolyte solution is added to a solution of a strong polyelectrolyte, the microcalorimetric and potentiometric titrations of poly(sodium 4-styrenesulfonate) (Na(+)PSS(-)) solution with different alkali, earth-alkali and tetraalkylammonium nitrate, perchlorate and chloride solutions were performed. From the calorimetric titrations the differences in sign and magnitude of enthalpy change upon addition of various electrolytes were observed depending on the salt used. Potentiometric titrations using a sodium ion selective electrode have revealed that addition of an electrolyte is accompanied by the increase in sodium activity until a certain critical value is reached, which seems to be the consequence of counterion substitution on the polyelectrolyte chain. In the case of addition of lithium and sodium salts the experimental results for ΔH of mixing can be qualitatively correctly explained by the Poisson-Boltzmann and Monte Carlo calculations based on the continuum solvent models. This is not the case for the mixtures with KNO(3), RbNO(3) and CsNO(3) salts. The results suggest that the ion-specific effects, associated with the changes in the water structure, have to be taken into account when thermodynamic properties of polyelectrolytes in solution are concerned. The calorimetric results imply that the enthalpically observed cation specificity for binding to a poly(styrenesulfonate) group could be correlated with corresponding cation hydration enthalpies. The counterion substitution of sodium with divalent cations was found to be endothermic, which is in qualitative agreement with the electrostatic theory.

Study of Sodium Ion Selective Electrodes and Differential Structures with Anodized Indium Tin Oxide

The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO as the reference electrode. Anodized-ITO was fabricated by anodic oxidation at room temperature, a low cost and simple manufacture process that makes it easy to control the variation in film resistance. The anodized-ITO based on EGFET structure has good linear pH sensitivity, approximately 54.44 mV/pH from pH 2 to pH 12. The proposed sodium electrodes prepared by PVC-COOH, DOS embedding colloid, and complex Na-TFBD and ionophore B12C4, show good sensitivity at 52.48 mV/decade for 10−4 M to 1 M, and 29.96 mV/decade for 10−7 M to 10−4 M. The sodium sensitivity of the differential sodium-sensing device is 58.65 mV/decade between 10−4 M and 1 M, with a corresponding linearity of 0.998; and 19.17 mV/decade between 10−5 M and 10−4 M.