Solid-Contact Potentiometric Cell with Symmetry

When two rough surfaces are loaded together contact occurs at asperity peaks. An interface of solid contact regions and air gaps is formed that is less stiff than the bulk material. The stiffness of a structure thus depends on the interface conditions; this is particularly critical when high stiffness is required, for example in precision systems such as machine tool spindles. The rough surface interface can be modelled as a distributed spring. For small deformation, the spring can be assumed to be linear; whilst for large deformations the spring gets stiffer as the amount of solid contact increases. One method to measure the spring stiffness, both the linear and nonlinear aspect, is by the reflection of ultrasound. An ultrasonic wave causes a perturbation of the contact and the reflection depends on the stiffness of the interface. In most conventional applications, the ultrasonic wave is low power, deformation is small and entirely elastic, and the linear stiffness is measured. However, if a high-powered ultrasonic wave is used, this changes the geometry of the contact and induces nonlinear response. In previous studies through transmission methods were used to measure the nonlinear interfacial stiffness. This approach is inconvenient for the study of machine elements where only one side of the interface is accessible. In this study a reflection method is undertaken, and the results are compared to existing experimental work with through transmission. The variation of both linear and nonlinear interfacial stiffnesses was measured as the nominal contact pressure was increased. In both cases interfacial stiffness was expressed as nonlinear differential equations and solved to deduce the contact pressure-relative surface approach relationships. The relationships derived from linear and nonlinear measurements were similar, indicating the validity of the presented methods.

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Potentiometric Carboxylate Sensors Based on Carbazole-Derived Acyclic and Macrocyclic Ionophores

Chemosensors ◽

10.3390/chemosensors9010004 ◽

2020 ◽

Vol 9 (1) ◽

pp. 4

Author(s):

Ville Yrjänä ◽

Indrek Saar ◽

Mihkel Ilisson ◽

Sandip A. Kadam ◽

Ivo Leito ◽

...

Keyword(s):

Detection Limit ◽

Vinyl Chloride ◽

Anion Exchanger ◽

Linear Range ◽

Ph Sensitivity ◽

Ion Selective Electrodes ◽

Solid Contact ◽

Response Characteristics ◽

Potentiometric Response ◽

Poly Vinyl Chloride

Solid-contact ion-selective electrodes with carbazole-derived ionophores were prepared. They were characterized as acetate sensors, but can be used to determine a number of carboxylates. The potentiometric response characteristics (slope, detection limit, selectivity, and pH sensitivity) of sensors prepared with different membrane compositions (ionophore, ionophore concentration, anion exchanger concentration, and plasticizer) were evaluated. The results show that for the macrocyclic ionophores, a larger cavity provided better selectivity. The sensors exhibited modest selectivity for acetate but good selectivity for benzoate. The carbazole-derived ionophores effectively decreased the interference from lipophilic anions, such as bromide, nitrate, iodide, and thiocyanate. The selectivity, detection limit, and linear range were improved by choosing a suitable plasticizer and by reducing the ionophore and anion exchanger concentrations. The influence of the electrode body’s material upon the composition of the plasticized poly(vinyl chloride) membrane, and thus also upon the sensor characteristics, was also studied. The choice of materials for the electrode body significantly affected the characteristics of the sensors.

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Calibration-Free Potentiometric Sensing With Solid-Contact Ion-Selective Electrodes

TrAC Trends in Analytical Chemistry ◽

10.1016/j.trac.2021.116277 ◽

2021 ◽

pp. 116277

Author(s):

Celeste R. Rousseau ◽

Philippe Bühlmann

Keyword(s):

Ion Selective Electrodes ◽

Solid Contact ◽

Calibration Free

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Ion-to-electron capacitance of single-walled carbon nanotube layers before and after ion-selective membrane deposition

Microchimica Acta ◽

10.1007/s00604-021-04805-1 ◽

2021 ◽

Vol 188 (5) ◽

Author(s):

Elena Zdrachek ◽

Eric Bakker

Keyword(s):

Carbon Nanotube ◽

Ion Selective Electrodes ◽

Solid Contact ◽

Single Walled Carbon Nanotube ◽

Single Walled Carbon ◽

Essential Step ◽

Before And After ◽

Selective Membrane ◽

High Potential Stability ◽

Potential Stability

AbstractThe capacitance of the ion-to-electron transducer layer helps to maintain a high potential stability of solid-contact ion-selective electrodes (SC-ISEs), and its estimation is therefore an essential step of SC-ISE characterization. The established chronopotentiometric protocol used to evaluate the capacitance of the single-walled carbon nanotube transducer layer was revised in order to obtain more reliable and better reproducible values and also to allow capacitance to be measured before membrane deposition for electrode manufacturing quality control purposes. The capacitance values measured with the revised method increased linearly with the number of deposited carbon nanotube–based transducer layers and were also found to correlate linearly before and after ion-selective membrane deposition, with correlation slopes close to 1 for nitrate-selective electrodes, to 0.7 and to 0.5 for potassium- and calcium-selective electrodes. Graphical abstract

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