Glass membrane electrodes with solid-state internal contacts for pH and pNa measurements

Like minerals and rocks, natural glasses, can provide important information on the history of the Earth, the Moon, and the planets. However, they are much rarer on the surface of the Earth than crystalline rocks and minerals (mineralogists have described about 3450 minerals). The reason for this difference can be found in the contents of water and other volatiles in the parental melt. These components reduce the viscosity of terrestrial magmas and increase the diffusion rate of dissolved oxides, with consequent crystal growth. It is unusual to find lava on the surface of the Earth that has solidified sufficiently fast to be preserved as glass. Conditions on the Moon are different. The lunar surface has been found to contain a wide variety of different kinds of glass, but only about 90 minerals have been identified. A similar, though less pronounced, phenomenon can be observed for the meteorites except for “wet” carbonaceous chondrites.

coverslip. When KB cells were grown on these composite coverslips and treated with directin, the orientation of the cells followed the longitudinal direction of the coverslip in a zigzag fasion. Experiments with different kinds of glass and other substrates are now in progress. Summary.-We have found an agent in extracts derived from human urine which can be identified by its induction of directional growth of malignant cells in a defined in vitro system. The extract sensitizes malignant cells to submicroscopic, directional clues in their environment. Nine cell lines have been examined so far, four malignant and five normal ones. The normal cell lines studied did not respond to directin.

Paper 1000905

Based upon the results of in vitro studies, antimony electrodes are generally considered to have inferior electrochemical properties when compared with glass electrodes. Since a direct comparison in man is lacking, a 24-hour ambulatory intragastric pH recording was performed in 10 healthy male subjects simultaneously using glass and antimony electrodes. In the first set of experiments (when both electrodes were calibrated in buffers of pH 7 and 1 at 37 degrees C: beaker calibration) significantly lower pH recordings during fasting periods were registered with the antimony electrode. This difference could be corrected by a modified calibration, using the external skin reference electrode of the antimony electrode (finger calibration). In the second series of experiments (performed after finger calibration) comparable recordings of 24-hour intragastric pH could be obtained with antimony and glass electrodes in the same subjects. The reason for statistically insignificant differences of pH recordings with both electrodes in the early hours of the morning remains uncertain. The drift of glass and antimony electrodes did not differ. It is concluded from these data that, after adequate calibration, inferior electrochemical properties of antimony electrodes do not influence intragastric pH recordings in man.

A “lab-to-fab” transition is described that enables the semi-automated production of thin-film potentiometric pH electrodes, designed for use in sterile single-use bioreactors. Manual methods of materials deposition and film casting are replaced with spray coating on a moving web and the production of membranes with a programmable dispenser operating at constant rates. These provide a greater degree of control over membrane thickness and a reduction in voltage spread between electrodes, which are evaluated in batches using a multichannel analyzer. Gamma-ray ionization of the pH electrodes introduces a predictable voltage drift that follows a log decay function on the day timescale; the voltage decay rate correlates with membrane thickness and can be modeled as a parallel diode–capacitor circuit. Batches of radiation-sterilized pH electrodes were tested in cell culture media and yielded mean pH values within 0.05 units relative to a commercial meter (ground truth) following a single-point calibration protocol. Quantitative uncertainty analysis attributes more than half of total error to variations caused by ionizing radiation, and yields novel insights into strategies for reducing uncertainty.

Automated analyzer for the determination of potassium and sodium in whole blood

Evaluation of the chloramine-T membrane electrode response in acidic solutions. The determination of the p Ka of N-chloro- p-toluenesulfonamide (chloramine-T acid)

The stated purpose of this paper is to provide a simple and quick method to assemble pH electrodes using readily available materials. The present assembled electrodes are comparable with commercial pH electrodes, with accuracy for pH determination in the range 2–12. Furthermore, the constructed simple pH electrodes exhibit a fast and stable response with a relatively wide linear range, meaning that these electrodes offer the promise of potential utilization in experiments. The inexpensive assembly and use of these pH glass membrane electrodes lends itself to introductory electrochemistry lab experiments at only a fraction of the cost of commercial electrodes. Under the guidance of instructors, students could make and test their own electrodes for chemical experiments. This might be helpful for students to gain a deeper understanding of the fundamentals of electrochemistry, such as the structure of ion-selective electrodes, the Nernst equation, etc.

A previously published research 2 with membranes of a BeO‐containing glass was continued. Electrodes of the glass in question show increasing responsiveness to monovalent cations according to the series:C3H7(NH3)+ < Li+ < Na+ < NH4+ < K+ < Rb+ < Ag+ < H+.In alkaline solutions, which may contain considerable amounts of Na+ by the side of K+, the glass electrodes are very suitable for the determination of the pK. The responsiveness of the electrodes to K+ and to the other monovalent cations can be expressed as a characteristic constant.

Temperature and frequency dependent ac electrical measurements were used to explore density of states, conduction mechanisms and dielectric properties of nickel disulfide (NiS2) nanoparticles. The NiS2 nanoparticles were prepared by conventional one step solid state reaction method at 250 °C. X-ray diffraction (XRD) confirmed cubic phase of prepared nanoparticles. Scanning electron microscope (SEM) images revealed presence of irregular shaped nanoparticles as small as 50 nm. The ac electrical measurements were carried out from 300 K to 413 K. Two depressed semicircular arcs from 20 Hz to 2 MHz showed presence of bulk and grain boundary phases in NiS2 nanoparticles at all temperatures. Small polaron hopping conduction from 300 K to 393 K and correlated barrier hopping conduction mechanism at temperatures higher than 393 K was observed. High value of density of states (of the order of 1024 eV−1cm−3) was calculated from ac conductivity. At low frequencies high values (of the order of 104-107) of real part of dielectric constant (ε′) were observed at different temperatures. These observations suggest that NiS2 nanoparticles may find applications in electronic devices.

A laboratory prototype monitor, based on direct potentiometry, has been designed and constructed for the determination of residual water in organic solvents using the proton isoconcentration technique (PICT). In the monitor, a sample stream is bled off and mixed with a buffer before passing through a cell containing a pH glass electrode, a reference electrode and an automatic temperature compensation probe. The instrument is calibrated with standard solutions containing water in the same solvent, the useful (i.e., sensitive) water range being 0–10%m/m water. The system is controlled by a program running on a general purpose minicomputer. Results obtained for residual water in methanol, ethanol, propan-1-ol, propan-2-ol, ethane-1,2-diol, propanone and butan-2-one show PICT to be sensitive, accurate and reproducible with an average response time of 7–10 min.

Effects of pH control by acid addition at the aqueous processing of cathodes for lithium ion batteries

The rapid development of mobile electronics, electric-vehicles and intermittent power generation relies on the availability of advanced electrochemical energy storage systems such as high capacity lithium ion batteries (LIBs). Although the state-of-the-art commercial LIBs have impressive electrochemical performance, they are suffering from relative low capacities due to the usage of host materials for storing lithium ions safely and reproducibly. The host material for LIB anode is dominated by graphite with a theoretical capacity of 372 mAh g-1. To further improve the capacity and energy density of LIBs, revolutionary changes in electrode materials, electrolytes, additives, binders and cell design are much needed. Alloying anode materials like Si, Ge and Sn have much higher theoretical capacities (4200, 1600 and 990 mAh g-1 for Si, Ge and Sn, respectively) as compared to graphite. However, a high capacity inevitably leads to a large electrode volume change during lithiation and de-lithiation process (e.g. 300% for Si-based anodes). Such a huge volume change can cause electrode pulverization, detachment of active materials from conductive additives, unstable solid-electrolyte interphase, and eventually result in a rapid, permanent capacity loss. Although Si-based anode has caught much research attention, formidable challenges remain to develop an electrode fabrication method that is efficient, low-cost, scalable, highly reproducible, and self-assembled, thus boosting the commercialization potential of Si-based anodes. As inspired by the hollow fiber membrane technology that has been successfully commercialized in the last decades to provide billions of gallons of purified drinking water worldwide, we report the use of carbonized asymmetric membrane electrodes (fiber and thin film types) that contain silicon, silicon monoxide, germanium, tin dioxide or vanadium (V) oxide to significantly increase LIB electrode capacity while maintaining a long cycling life and an excellent rate performance. These asymmetric membrane electrodes are fabricated using a modified reverse-osmosis membrane technology, the phase-inversion method combined with dip-coating and carbonization. The asymmetric membrane electrodes have a thin, nanoporous top layer (up to several microns) and a thick, macroporous bottom layer (up to 200 µm). The top layer can prevent fractured anode materials from falling away, while the bottom layer can efficiently accommodate the large volume changes of high capacity alloying anodes. 90% capacity of thin film asymmetric membrane at 1000 mAh g-1 containing Si nanoparticles can be retained after 200 cycles with an initial capacity loss of ~ 30%. Combining phase inversion with sol-gel chemistry, this method can be extended to obtain SnO2 and V2O5 asymmetric membranes. Thin film SnO2 asymmetric membrane electrode demonstrates a specific capacity of 500 mAh g-1 a current density of 280 mA g-1 (~0.5C) with >96% capacity retention after 400 cycles. When the current density is increased from 28 to 560 mA g-1, more than 65% capacity can be retained. The V2O5 electrode can be cycled at 0.5C with a capacity of 160 mAh g-1 for 380 times with ~100% capacity retention. The same method can be employed to stabilize micron-size Ge and Si alloying anodes with >80% capacity retention in 100 cycles. Most recently, our group has successfully fabricated various fibrous Si and Sn asymmetric membrane electrodes whose electrochemical performance is compared to thin film Si and Sn asymmetric membrane electrodes. e.g. ~90 % initial capacity at ~1,200 mAh g-1 can be maintained in 300 cycles applying a current density of 400 mA g-1 with an initial capacity loss less than 15%. These asymmetric membrane electrodes have been systematically characterized using extensive instruments spanning from scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, powder X-ray diffractometer (PXRD), thermogravimetric analyzer (TGA), surface area analyzer (BET method) to X-ray photoelectron spectroscopy (XPS), as well as various electrochemical tests such as cycling and rate performance, cyclic voltammetry, and electrochemical impedance spectroscopy, purposing to understand the relationship between structure, chemical composition and electrochemical properties for these asymmetric membrane electrodes.

Simultaneous measurements with magnesium ion-selective and pH glass electrodes have been used for determination of the stability constants of magnesium ions with various biologically relevant ligands by alkalimetric titration under physiological conditions (37 ○C, I=0.15 mol⋅dm−3). New systems were investigated: magnesium with pyroglutamate, pyridoxine and HEPES, along with citrate, lactate, glycinate, aspartate and glutamate. For comparison, calcium stability constants with the same ligands were determined similarly, using calcium ion-selective and pH glass electrodes. Ligand protonation constants, necessary for the calculation of the metal complex formation constants, were also determined.

The P-wave velocities and electrical conductivities of gabbro were measured using ultrasonic transmission method and impedance spectroscopy from room temperature to 1100℃ at 1—2 GPa, and the factors controlling the P-wave velocity and the microscopic conductance mechanisms of the rock were analyzed. The experimental results show that the P-wave velocities of gabbro drop abruptly at temperatures of 800—850℃ and under pressures of 1—2 GPa due to the occurrence of grain boundary phases and dehydration melting; however, the electrical conductivities and electronic conduction mechanisms have not changed obviously at temperatures of 800—850℃. At temperatures Below 680℃, only one impedance arc (I) corresponding to grain interior conduction occurs at frequencies between 12 Hz and 10 5 Hz, the second arc (II) corresponding to grain boundary conduction occurs at temperatures above 680℃. The total conductivity of this rock is dominated by the grain interior conductivity as the occurrence of grain boundary conduction has a small effect on the total conductivity. The laboratory-measured velocities are consistent with the average P-wave velocity observations of lower crust and upper mantle. The conductivity values correspond well with the gabbroite composition of the lower crust and upper mantle; however, they are about 1—2 orders of magnitude lower than MT data from the high conductive layers. The experiments confirm that the dehydration of hydrous minerals can induce the partial melting, and the low seismic velocity zones might be correlated with the high conductive layers if partial melting occurs.