Journal articles: 'PH-potentiometry'

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Ma, Ming Ming, Zhi Tong, and Yong Wen. "Poly Silk Peptide Film PH Sensor Based on Zero Current Potentiometry." Advanced Materials Research 450-451 (January 2012): 554–56. http://dx.doi.org/10.4028/www.scientific.net/amr.450-451.554.

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A poly silk peptide film pH sensor has been developed using zero current potentiometry system. A poly silk peptide film coated pencil graphite electrode is connected in series between the working and counter electrodes of a potentiostat, and immersed in solution together with a reference electrode. When the solution pH varies, the resulting zero current potentiometry is linear with the values of the solution pH in the range of 1.81 to 11.58. This pH sensor shows high stability, accuracy, selectivity and reproduction.

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Zimmermann, Peter, Andreas Weltin, Gerald Urban, and Jochen Kieninger. "Active Potentiometry for Dissolved Oxygen Monitoring with Platinum Electrodes." Sensors 18, no. 8 (July 24, 2018): 2404. http://dx.doi.org/10.3390/s18082404.

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Potentiometric oxygen monitoring using platinum as the electrode material was enabled by the combination of conventional potentiometry with active prepolarization protocols, what we call active potentiometry. The obtained logarithmic transfer function is well-suited for the measurement of dissolved oxygen in biomedical applications, as the physiological oxygen concentration typically varies over several decades. We describe the application of active potentiometry in phosphate buffered salt solution at different pH and ion strength. Sensitivity was in the range of 60 mV/dec oxygen concentration; the transfer function deviated from logarithmic behavior for smaller oxygen concentration and higher ion strength of the electrolyte. Long-term stability was demonstrated for 60 h. Based on these measurement results and additional cyclic voltammetry investigations a model is discussed to explain the potential forming mechanism. The described method of active potentiometry is applicable to many different potentiometric sensors possibly enhancing sensitivity or selectivity for a specific parameter.

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Ma, Ming Ming, Zhi Tong, and Yong Wen. "Poly Silk Peptide Film PH Sensor Based on Zero Current Potentiometry." Advanced Materials Research 450-451 (January 2012): 554–56. http://dx.doi.org/10.4028/scientific5/amr.450-451.554.

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Kay, C. J., M. J. Barber, B. A. Notton, and L. P. Solomonson. "Oxidation–reduction midpoint potentials of the flavin, haem and Mo-pterin centres in spinach (Spinacia oleracea L.) nitrate reductase." Biochemical Journal 263, no. 1 (October 1, 1989): 285–87. http://dx.doi.org/10.1042/bj2630285.

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Oxidation-reduction midpoint potentials have been determined for the flavin, cytochrome b557 and Mo-pterin prosthetic groups of spinach (Spinacia oleracea L.) assimilatory nitrate reductase using visible, c.d. and room-temperature e.p.r. potentiometric titrations. At pH 7 and 25 degrees C, the midpoint potential for the FAD/FADH2 couple was determined by c.d. potentiometry to be -280 +/- 10 mV (n = 2). The redox potential for reduction of the haem was determined by visible potentiometry to be -123 +/- 10 mV (n = 1), significantly lower than the previously published value of -60 mV [Fido, Hewitt, Notton, Jones & Nasrulhaq-Boyce (1979) FEBS Lett. 99, 180-182]. Potentials for the Mo(VI)/Mo(V) and Mo(V)/Mo(IV) redox couples, determined by room-temperature e.p.r. potentiometry, were found to be +2 +/- 20 and -6 +/- 20 mV respectively. These values are very similar to the values previously determined for the FAD, haem and Mo-pterin centres in assimilatory nitrate reductase isolated from the unicellular green alga Chlorella vulgaris and indicate a close thermodynamic similarity between the two enzymes.

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Gonzalez, Samantha Lemke, Regina Cristina Aparecida Lima, Eliana Beleski Borba Carneiro, Mareci Mendes de Almeida, and Neiva Deliberali Rosso. "Pectin methylesterase activity determined by different methods and thermal inactivation of exogenous pme in mango juice." Ciência e Agrotecnologia 35, no. 5 (October 2011): 987–94. http://dx.doi.org/10.1590/s1413-70542011000500017.

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Pectin methylesterase (PME) hydrolyzes methyl ester groups in pectin chains to form carboxylic groups, releasing methanol and H3O+. The aim of this study was to determine PME activity in samples of pectinases by UV-VIS spectroscopy, to measure the acid and methanol produced in the reaction of pectin with pectinase and to verify the thermal inactivation of exogenous PME in mango juice. The activity of PME in samples of pectinase was determined by potentiometry, UV-VIS spectroscopy, and by the action of alcohol oxidase. The reaction showed greater activity at pH 4.0 to 4.5 and at a temperature of 45° C. PME activity determined by UV-VIS spectroscopy with bromophenol blue indicator showed a good correlation with the activity determined by potentiometry and with alcohol oxidase. The results showed that bromophenol blue indicators can be used to determine PME activity in samples of pectinases where the optimum pH is located in the acidic range. The thermal inactivation of exogenous PME in mango juice occurred at 75° C for 20 min of exposure.

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Etienne, Mathieu, Paul Dierkes, Thomas Erichsen, Wolfgang Schuhmann, and Ingrid Fritsch. "Constant-Distance Mode Scanning Potentiometry. High Resolution pH Measurements in Three-Dimensions." Electroanalysis 19, no. 2-3 (January 2007): 318–23. http://dx.doi.org/10.1002/elan.200603735.

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Natedungta, W., and W. Prissanaroon-Ouajai. "All-Solid-State pH Sensor Based on Conducting Polymer." Advanced Materials Research 93-94 (January 2010): 591–94. http://dx.doi.org/10.4028/www.scientific.net/amr.93-94.591.

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A solid-state (free of internal electrolyte solution) reference electrode based on metallic silver is simply fabricated via a simple electrodeposition from AgNO3. Potentiometry is carried out to study the performance of the solid-state reference electrode in comparison with the commercial Ag/AgCl reference electrode. In addition, the proposed solid-state reference electrode has been integrated with the PPy-modified pH electrode to form an all-solid-state pH sensor, showing the capability of pH measurement. Absence of the internal solution leads to the pH sensor that is convenient to use and maintenance. In addition, the proposed pH sensor is possibly applied to biochemical and medical processes as well as flow infection analysis.

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Shehatta, I., I. Kenawy, A. H. Askalany, and Ayman A. Hassan. "Thermodynamic of metal complexation of the macrocyclic antibiotic rifampicin." Canadian Journal of Chemistry 79, no. 1 (January 1, 2001): 42–49. http://dx.doi.org/10.1139/v00-172.

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The acid-base and complexation equilibria of rifampicin with H+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+ were studied by means of potentiometry. The stoichiometric equilibrium constants were determined in 50% (v/v) methanol-water medium at different temperatures and constant ionic strength (0.05 M KCl). It was established that rifampicin has two proton-binding sites. The distribution diagram of the corresponding ionic species as a function of pH is given and indicated that rifampicin exists predominantly in the zwitterionic form at pH [Formula: see text] 5. The thermodynamic parameters of protonation and complexation were derived and discussed. The formation of the complexes is spontaneous, more favourable at lower temperatures, entropically unfavourable, and an enthalpy-driven process. The order of the changes in Gibbs energy and enthalpy accompanying the complexation was found to be Mn2+ < Co2+ < Ni2+ < Cu2+ > Pb2+ > Zn2+ > Cd2+ > Hg2+ in accordance with the well-known sequence of Irving and Williams. The transition series contraction energy (Er(Mn-Zn)), and the ligand field stabilization energy (δH) were calculated from the enthalpy changes.Key words: rifampicin, thermodynamics, potentiometry, and complexation.

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9

Gao, Zhu Qing, Xiao Dong Cai, Lei Lei Cheng, and Kai Cheng Ling. "Studies on the Coordination Reactions of Polyphenols and Vanadium (IV) Using pH-Potentiometry." Advanced Materials Research 396-398 (November 2011): 2225–29. http://dx.doi.org/10.4028/www.scientific.net/amr.396-398.2225.

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Protonation constants of pyrocatechol, pyrogallol and gallic acid, and stability constants, thermodynamic properties of their complexes with tetravalent vanadium VO2+ have been calculated by using pH-potentiometry at different temperatures and ionic strength of 0.1mol•L-1NaCl. The results indicated protonation constants and stability constants decrease with increasing temperature. Higher temperature is unfavorable to the complexation reactions. This kind of reaction is exothermic reaction that was spontaneous. Compared with all thermodynamic properties, the enthalpy change is the driving force for the reaction.

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Lefèvre, G., and G. Berger. "Potentiometry up to 275°C: Example of pH titrations of cobalt ferrite particles." Journal of Colloid and Interface Science 430 (September 2014): 12–17. http://dx.doi.org/10.1016/j.jcis.2014.05.017.

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11

Boeyckens, Ann, Jan Schots, Hugo Vandenplas, Freedy Senesael, Wim Goedhuys, and Frans K. Gorus. "Ektachem Slides for Direct Potentiometric Determination of Sodium in Plasma: Effect of Natremia, Blood pH, and Type of Electrolyte Reference Fluid on Concordance with Flame Photometry and Other Potentiometric Methods." Clinical Chemistry 38, no. 1 (January 1, 1992): 114–18. http://dx.doi.org/10.1093/clinchem/38.1.114.

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Abstract With electrolyte reference fluid (ERF)00, results from Kodak Ektachem slides for the direct potentiometric assay of sodium in plasma were significantly correlated with results from flame photometry, but also appeared to be systematically higher, especially in hypernatremic patients. Indirect potentiometry with the Technicon RA-1000 yielded intermediate values. In 23 hypernatremic patients with greater than or equal to 6 mmol/L difference in sodium between Ektachem ERF00 and flame photometry, a clinical survey disclosed the frequent association of large between-method differences with renal failure, diabetes mellitus, and gastrointestinal disease. However, there was no correlation between differences in sodium on the one hand and anion gaps or (lipo)protein concentrations on the other, nor did in vitro addition studies implicate metabolites that often accumulate in the above-mentioned disorders. Unlike indirect methods, sodium measurements by direct potentiometry on Ektachem and Corning were influenced by in vitro changes of pH between 7.0 and 7.9. However, in a group of patients that included many acidotic individuals, between-method differences in sodium appeared not significantly correlated with in vivo blood pH. Use of the equitransferant ERF04 on Ektachem strongly diminishes the systematic differences with flame photometry, reduces the pH-dependency of the results to that of the direct Corning method, and brings the mean analytical recovery of sodium to below 95% (instead of 115% previously) without affecting the ability of Ektachem slides to avoid spuriously low results in the presence of increased (monoclonal) protein concentrations.

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12

Sousa, Myrelle Leal Campos, Isabela Alice Soares de Medeiros, Liege Helena Freitas Fernandes, Smyrna Luiza Ximenes de Souza, Alidianne Fábia Cabral Cavalcanti, and Alessandro Leite Cavalcanti. "In Vitro Analysis of the Erosive Potential of Whey Protein." Research, Society and Development 9, no. 9 (August 27, 2020): e487997742. http://dx.doi.org/10.33448/rsd-v9i9.7742.

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The objective of this study was to evaluate the pH and total soluble solids (TSS) content of whey protein beverages. Nine products of three different flavors (vanilla, strawberry and chocolate) of the following brands Muke®, Best Whey®, and Essencial Nutrition Whey®, had their pH evaluated by potentiometry, and their TSS evaluated by refractometry. The lowest pH recorded was for Muke® Chocolate (5.75), and the highest was for Essencial Nutrition Whey® Cacao (6.91). Regarding TSS, the lowest average was for Essencial Nutrition Whey® Vanilla (10.17), and the highest was for Essencial Nutrition Whey® Red Berry (16.66). There was no statistically significant difference in pH and TSS among the flavors and brands evaluated. It was concluded that the analyzed beverages had a higher pH than the pH that is critical to dental enamel and the TSS content was considered high.

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Mulyasuryani, Ani, Anna Roosdiana, and Arie Srihardyastutie. "THE POTENTIOMETRIC UREA BIOSENSOR USING CHITOSAN MEMBRANE." Indonesian Journal of Chemistry 10, no. 2 (July 21, 2010): 162–66. http://dx.doi.org/10.22146/ijc.21454.

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Potentiometric urea biosensor development is based on urea hydrolysis by urease resulted CO2. The biosensor is used chitosan membrane and the H3O+ electrode as a transducer. The research was studied of effecting pH and membrane thickness to the biosensor performance. The best biosensor performance resulted at pH = 7.3 and 0.2 mm of membrane thickness. The biosensor has a Nerntian factor 28.47 mV/decade; the concentration range is 0.1 up to 6.00 ppm; and the limit of detection is 0.073 ppm. The response time of this biosensor is 280 seconds, efficiency 32 samples and accuracy 94% up to 99%. Keywords: biosensor, potentiometry, urea, chitosan membrane

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14

Kahlert, Heike, Jens R Pörksen, Ibrahim Isildak, Müberra Andac, Murat Yolcu, Jürgen Behnert, and Fritz Scholz. "Application of a New pH-Sensitive Electrode as a Detector in Flow Injection Potentiometry." Electroanalysis 17, no. 12 (June 2005): 1085–90. http://dx.doi.org/10.1002/elan.200403218.

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15

Byrne, Laurann, Michael J. Hynes, Cathal D. Connolly, and Richard A. Murphy. "Influence of the Chelation Process on the Stability of Organic Trace Mineral Supplements Used in Animal Nutrition." Animals 11, no. 6 (June 10, 2021): 1730. http://dx.doi.org/10.3390/ani11061730.

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The effect of the chelation process on the pH-dependent stability of organic trace minerals (OTMs) used as mineral supplements in animal nutrition was assessed using analytical techniques such as potentiometry, Fourier Transform Infrared Spectroscopy (FTIRS) and amino acid profiling. The aim was to understand the influence and relative importance of the manufacturing conditions on mineral chelation and the subsequent pH stability of OTMs. A selection of OTMs were assessed over a wide pH range to account for the typical environmental changes encountered in the gastrointestinal (GI) tract. In the case of proteinate type products, the potentiometric assessment of free mineral concentration indicated that the hydrolysis procedure used to generate the chelating peptides was the major influencer of the pH stability of the products. Many products are available under the umbrella term “OTMs”, including amino acid complexes, amino acid chelates, polysaccharide complexes and proteinates. Significant differences in the pH-dependent stability of a range of commercially available OTMs were observed.

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Beysebekov, Marat K., Assel K. Toktabaeva, and Zharylkasyn A. Abilov. "Sorption of Richlokain on Polycarboxylic Acid Gels." Eurasian Chemico-Technological Journal 5, no. 4 (April 6, 2016): 311. http://dx.doi.org/10.18321/ectj319.

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The sorption immobilization of richlokain on gels of polyacrylic acid (PAAG) or polymethacrylic acid (PMAAG) has been studied. By a number of methods – equilibrium swelling, potentiometry, IR-spectroscopy, and sorption it has been shown that binding of richlokain with these gels leads to the complex formation owing to the electrostatic interaction, which is stabilised by the hydrophobic and hydrogen bonds. Effect of an ionic force, reagent concentration, cross-link degree, hydrophobic nature of gels, and pH of solutions on the sorption process has been studied.

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Heering, Agnes, Daniela Stoica, Filomena Camões, Bárbara Anes, Dániel Nagy, Zsófia Nagyné Szilágyi, Raquel Quendera, et al. "Symmetric Potentiometric Cells for the Measurement of Unified pH Values." Symmetry 12, no. 7 (July 9, 2020): 1150. http://dx.doi.org/10.3390/sym12071150.

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A unified pH scale of absolute values (pHabs scale) enables the comparison of acidities in different solvents. To date, very few different experimental setups have been used for the measurement of values on this scale. The article describes the design and performance of the different symmetric cells used for unified pH measurement by several institutions. Well-established and reliable standard aqueous buffer solutions are the first step of method validation necessary to achieve a robust metrological level for more complex media. The pH of aqueous standard buffers was measured by differential potentiometry, where the potential between two glass electrodes is measured directly. All the tested electrochemical cells prove to be suitable for unified pH measurements. This validation highlights that the method is, to a large extent, independent of the used equipment, including the cell geometry. The inherent symmetry of the cell design helps to reduce the experimental workload and improve the accuracy of obtained results.

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Fernandes, J. C. B., and E. V. Heinke. "Alternative strategy for manufacturing of all-solid-state reference electrodes for potentiometry." Journal of Sensors and Sensor Systems 4, no. 1 (February 12, 2015): 53–61. http://dx.doi.org/10.5194/jsss-4-53-2015.

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Abstract. This paper presents an alternative strategy for manufacturing solid-state reference electrodes based on particles of graphite/silver/silver chloride synthesized by electroless deposition of metallic silver and silver chloride on graphite powder. Two kinds of reference electrodes were manufactured by mixing these particles with epoxy resin and hardener: quasi-reference and all-solid-state containing salts of alkaline or alkaline earth metals. All-solid-state reference electrodes can be sterilized with high-pressure saturated steam at 394.15 K (121 °C) using an autoclave. These electrodes presented a stable potential between pH 2 and 11. The electrode surface was characterized by scanning electron microscopy and showed the presence of silver and salt particles. The size of the silver particles was less than 2.5 μm. We successfully applied the all-solid state reference electrodes in potentiometric cells to measure pH and potassium ions in complex matrix by direct potentiometry and L-ascorbic acid by potentiometric titration.

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Andrasi, Melinda, Peter Buglyo, Laszlo Zekany, and Attila Gaspar. "A comparative study of capillary zone electrophoresis and pH-potentiometry for determination of dissociation constants." Journal of Pharmaceutical and Biomedical Analysis 44, no. 5 (September 2007): 1040–47. http://dx.doi.org/10.1016/j.jpba.2007.04.024.

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Dimitrakopoulos, Lucy T., Telis Dimitrakopoulos, Peter W. Alexander, Dusan Logic, and D. Brynn Hibbert. "A tungsten oxide coated wire electrode used as a pH sensor in flow injection potentiometry." Analytical Communications 35, no. 12 (1998): 395–98. http://dx.doi.org/10.1039/a807697i.

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Midgley, Derek. "Temperature compensation in potentiometry: isopotentials of pH glass electrodes and reference electrodes. Part I. Theory." Analyst 112, no. 5 (1987): 573. http://dx.doi.org/10.1039/an9871200573.

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Voskoboynikova, Olga, Aleksey Sukhanov, and Axel Duerkop. "Optical pH Sensing in Milk: A Small Puzzle of Indicator Concentrations and the Best Detection Method." Chemosensors 9, no. 7 (July 12, 2021): 177. http://dx.doi.org/10.3390/chemosensors9070177.

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Optical chemical sensors can yield distinctively different responses that are dependent on the method applied for readout and evaluation. We therefore present a comprehensive study on the pH determined non-continuously with optical sensors in real milk samples by either photometry or colorimetry (via the RGB-readout of digital images) compared to the pH values obtained electrochemically by potentiometry. Additionally, the photometric determination of pH was conducted with single-wavelength and a dual wavelength ratiometric evaluation of the absorbance. It was found that both the precision and accuracy of the pH determined by photometry benefit from lower concentrations of bromocresol purple, which served as the pH indicator inside the sensor membrane. A further improvement is obtained by the ratiometric evaluation of the photometric sensor response. The pH values obtained from the colorimetric evaluation, however, gain in precision and accuracy if a higher concentration of the indicator is immobilized inside the sensor membrane. This has a major impact on the future fabrication of optical pH sensor membranes because they can be better tuned to match to the most precise and accurate range of the planned detection method.

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Stylianou, Marios, Anastasios D. Keramidas, and Chryssoula Drouza. "pH-Potentiometric Investigation towards Chelating Tendencies ofp-Hydroquinone and Phenol Iminodiacetate Copper(II) Complexes." Bioinorganic Chemistry and Applications 2010 (2010): 1–8. http://dx.doi.org/10.1155/2010/125717.

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Copper ions in the active sites of several proteins/enzymes interact with phenols and quinones, and this interaction is associated to the reactivity of the enzymes. In this study the speciation of theCu2+with iminodiacetic phenolate/hydroquinonate ligands has been examined by pH-potentiometry. The results reveal that the iminodiacetic phenol ligand forms mononuclear complexes withCu2+at acidic and alkaline pHs, and a binuclearOphenolate-bridged complex at pH range from 7 to 8.5. The binucleating hydroquinone ligand forms only 2 : 1 metal to ligand complexes in solution. The pK values of the protonation of the phenolate oxygen of the two ligands are reduced about 2 units after complexation with the metal ion and are close to the pK values for the copper-interacting tyrosine phenol oxygen in copper enzymes.

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Cavalcanti, Alessandro Leite, Ianny Alves Ramos, Rafaela Bastos Leite, Mariana da Costa Oliveira, Karynna de Melo Menezes, Lígia Virgínio Fernandes, Ricardo Dias de Castro, and Fernando Fernandes Vieira. "Endogenous pH, Titratable Acidity and Total Soluble Solid Content of Mouthwashes Available in the Brazilian Market." European Journal of Dentistry 04, no. 02 (April 2010): 156–59. http://dx.doi.org/10.1055/s-0039-1697823.

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Objectives: To evaluate in vitro the endogenous pH, titratable acidity and total soluble solid content (TSSC) of mouthwashes available in the Brazilian market.Methods: The study sample was composed of 10 commercial brands of mouthwashes based on different active ingredients: Cepacol®, Clinerize®, Equate®, Listerine Cool Citrus®, Oral-B®, Periogard ®, Peroxyl®, Plax Overnight®, Prevident 220® and Sanifill®. The experiments were performed in triplicate. The endogenous pH was evaluated by potentiometry, titratable acidity was evaluated by the addition of 0.1N KOH increments to the mouthwashes, and TSSC readings were performed by Brix refractometry using the Abbé refractometer.Results: pH values ranged from 3.56 (Peroxyl®) to 7.43 (Cepacol®) and three mouthwashes presented pHs below 5.5. The titratable acidity values ranged from 0.007 (Periograd®) to 0.530 (Prevident ®). Oral B® and Clinerize® presented the lowest (4.7%) and the highest (23.70%) TSSC, respectively.Conclusions: Some of the mouthwashes evaluated in this study presented low endogenous pH, even below the critical value for enamel dissolution (pH<5.5), high titratable acidity and high TSSC, and may be potentially erosive to the dental tissues if not properly used. (Eur J Dent 2010;4:156-159)

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Teixeira, Marcos F. de S., Luiz A. Ramos, Neila M. Cassiano, Orlando Fatibello-Filho, and Nerilso Bocchi. "Evaluation of a Fe2O3-based graphite-epoxy tubular electrode as pH sensor in flow injection potentiometry." Journal of the Brazilian Chemical Society 11, no. 1 (February 2000): 27–31. http://dx.doi.org/10.1590/s0103-50532000000100006.

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Caudana, Francesco, Giuseppe Ermondi, Maura Vallaro, Marina Shalaeva, and Giulia Caron. "Permeability prediction for zwitterions via chromatographic indexes and classification into ‘certain’ and ‘uncertain’." Future Medicinal Chemistry 11, no. 13 (July 2019): 1553–63. http://dx.doi.org/10.4155/fmc-2019-0071.

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Background: The development of zwitterions to a drug is likely to be more challenging than compounds of other charge types. Results: Two chromatographic indexes (log k′80 PLRP-S and log KWIAM) can be successfully used as permeability classifiers of ampholytes. Moreover, a pragmatic classification into ordinary ampholytes; zwitterions ‘certain’ (i.e., the zwitterionic species is dominant in the physiological pH range); and zwitterions ‘uncertain’ (multiple species are present in the physiological pH range) enables to study the permeability of ampholytic compounds in relation to species distribution. Methodology: Potentiometry (pKa), reversed-phase (RP)-chromatography, tri-layer parallel artificial membrane permeability assays, quantitative structure-property relationships (QSPR) and block relevance (BR) analysis, receiver operating characteristic (ROC) curves. Conclusion: Structures considered as poorly permeable like zwitterions can be integrated in drug discovery programs by applying ad hoc experimental and computational tools.

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Krezel, Artur, Marios Mylonas, Edyta Kopera, and Wojciech Bal. "Sequence-specific Ni(II)-dependent peptide bond hydrolysis in a peptide containing threonine and histidine residues." Acta Biochimica Polonica 53, no. 4 (November 22, 2006): 721–27. http://dx.doi.org/10.18388/abp.2006_3299.

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Previously we demonstrated that Ni(II) complexes of Ac-Thr-Glu-Ser-His-His-Lys-NH2 hexapeptide, representing residues 120-125 of human histone H2A, and some of its analogs undergo E-S peptide bond hydrolysis. In this work we demonstrate a similar coordination and reactivity pattern in Ni(II) complexes of Ac-Thr-Glu-Thr-His-His-Lys-NH2, its threonine analogue, studied using potentiometry, electronic absorption spectroscopy and HPLC. For the first time we present the detailed temperature and pH dependence of such Ni(II)-dependent hydrolysis reactions. The temperature dependence of the rate of hydrolysis yielded activation energy E(a) = 92.0 kJ mol(-1) and activation entropy DeltaS# = 208 J mol(-1) K(-1). The pH profile of the reaction rate coincided with the formation of the four-nitrogen square-planar Ni(II) complex of Ac-Thr-Glu-Thr-His-His-Lys-NH2. These results expand the range of protein sequences susceptible to Ni(II) dependent cleavage by those containing threonine residues and permit predictions of the course of this reaction at various temperatures and pH values.

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Khasanah, Mirartul, Handoko Darmokoesoemo, and Nesti Widayanti. "Pengembangan Elektroda Pasta Karbon termodifikasi Molecularly Imprinted Polymer sebagai Sensor Potensiometri Asam Urat." Jurnal Kimia Riset 1, no. 2 (December 21, 2016): 65. http://dx.doi.org/10.20473/jkr.v1i2.3085.

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ABSTRAK Pengembangan elektroda pasta karbon/molecularly imprinted polymer (MIP) sebagai sensor untuk analisis asam urat secara potensiometri telah dilakukan. MIP dibuat dari monomer metil metakrilat, cross-linker etilen glikol dimetakrilat, dan asam urat sebagai template. Elektroda yang memberikan kinerja optimum dibuat dengan komposisi karbon, MIP, dan parafin 40:25:35(%b/b). Pengukuran larutan asam urat dilakukan pada pH optimum 5. Kinerja elektroda dinyatakan dengan nilai faktor Nernst sebesar 30,19 mV/dekade dengan jangkauan pengukuran 10-6-10-3 M, koefisien variasi 1,36-2,03%, akurasi 63,9-166,0 % dan batas deteksi bawah sebesar 3,03x10-6 M. Pengukuran asam urat dengan elektroda ini tidak diganggu oleh keberadaan urea yang ditunjukkan dengan nilai koefisien selektivitas (Kij) kurang dari satu. Elektroda ini memiliki waktu respon kurang dari dua menit dan waktu hidup selama delapan minggu dengan 104 kali pemakaian. Kata kunci: elektroda pasta karbon, MIP, potensiometri, asam urat ABSTRACTCarbon paste electrode modified molecularly imprinted polymer (MIP) as a sensor to analyze uric acid by potentiometry has been developed. MIP was synthesized by mixing methyl methacrylate as monomer, etylene glycol dimethacrylic acid as cross-linker, and uric acid as template. The electrode which showed the best performance was manufactured by ratio of carbon, MIP, and paraffin of 40:25:35 (w/w). The developed electrode showed the optimum performance on the uric acid pH 5. The performances of carbon paste/MIP electrode was expressed by Nernst factor of 30.19 mV/decade, measurement range of 10-6-10-3 M, the coefficient of variation (CV) of 1.36-2.03% and accuracy of 63.9-166.0%. The detection limit of this method was 3.03x10-6 M. Analysis of uric acid using the electrode was not interfered by urea. The developed electrode showed the response time less than 2 minutes, while lifetime of the electrode was 8 weeks (104 times usage). Keyword : carbon paste electrode, MIP, potentiometry, uric acid

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Evagelou, Vassilis, Anna Tsantili-Kakoulidou, and Michael Koupparis. "Determination of the dissociation constants of the cephalosporins cefepime and cefpirome using UV spectrometry and pH potentiometry." Journal of Pharmaceutical and Biomedical Analysis 31, no. 6 (April 2003): 1119–28. http://dx.doi.org/10.1016/s0731-7085(02)00653-2.

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Deleebeeck, Lisa, Alan Snedden, Dániel Nagy, Zsófia Szilágyi Nagyné, Matilda Roziková, Martina Vičarová, Agnes Heering, et al. "Unified pH Measurements of Ethanol, Methanol, and Acetonitrile, and Their Mixtures with Water." Sensors 21, no. 11 (June 7, 2021): 3935. http://dx.doi.org/10.3390/s21113935.

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Measurement of pH in aqueous-organic mixtures with different compositions is of high importance in science and technology, but it is, at the same time, challenging both from a conceptual and practical standpoint. A big part of the difficulty comes from the fundamental incomparability of conventional pH values between solvents (spH, solvent-specific scales). The recent introduction of the unified pH (pHabs) concept opens up the possibility of measuring pH, expressed as pHabsH2O, in a way that is comparable between solvent, and, thereby, removing the conceptual problem. However, practical issues remain. This work presents the experience of the authors with measuring pHabsH2O values in mixtures of methanol, ethanol, and acetonitrile, with water, but without the presence of buffers or other additives. The aim was to assigned pHabsH2O values to solvent–water mixtures using differential potentiometry and the ‘pHabs-ladder’ method. Measurements were made of the potential difference between glass electrodes immersed in different solutions, separated by an ionic liquid salt bridge. Data were acquired for a series of solutions of varying solvent content. This work includes experiences related to: a selection of commercial electrodes, purity of starting material, and comparability between laboratories. Ranges of pHabsH2O values for selected compositions of solvent–water mixtures are presented.

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De Tommaso, Gaetano, Maria Michela Salvatore, Rosario Nicoletti, Marina DellaGreca, Francesco Vinale, Assunta Bottiglieri, Alessia Staropoli, et al. "Bivalent Metal-Chelating Properties of Harzianic Acid Produced by Trichoderma pleuroticola Associated to the Gastropod Melarhaphe neritoides." Molecules 25, no. 9 (May 4, 2020): 2147. http://dx.doi.org/10.3390/molecules25092147.

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Harzianic acid is a secondary metabolite of Trichoderma, structurally belonging to the dienyltetramic acid subgroup of the tetramic acids. Biological activities of harzianic acid are of great interest for its antimicrobial and plant growth-promoting activities, which might be related to its chelating properties. In the present work harzianic acid, isolated from cultures of a strain of Trichoderma pleuroticola associated to the gastropod Melarhaphe neritoides, was studied as a complexant agent of a number of biologically relevant transition metals (i.e., Zn2+, Fe2+, Cu2+, and Mn2+), using UV-VIS, potentiometry, MS and NMR techniques. Our findings show the coordination capacity of harzianic acid toward the above cations through the formation of neutral or charged complexes in a variable ratio depending on the metal and pH conditions.

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Midgley, Derek. "Temperature compensation in potentiometry: isopotentials of pH glass electrodes and reference electrodes. Part II. Performance of commercial electrodes." Analyst 112, no. 5 (1987): 581. http://dx.doi.org/10.1039/an9871200581.

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Urminská, Jana, Boris Václav, and Peter Ondrišík. "Evaluation Of Exchange Reaction In Soil In Sediments Of A Region Affected By Anthropogenic Activity In Relation To The Time And To The Selected Potentially Toxic Elements." Acta Horticulturae et Regiotectuare 18, no. 2 (November 1, 2015): 30–34. http://dx.doi.org/10.1515/ahr-2015-0007.

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Abstract The aim of this study was to analyse sediments of the selected water reservoirs of Piargs group. Secondly, our purpose was to determine values of exchange reactions in soil of these sediments during the period from 2001 to 2010 and to evaluate environmental hazards caused by the selected potentially toxic elements affected by pH. Based on the results gained by analysis we aim to determine the correlation and statistical significance of dependencies of the analysed environmental parameters. Two different methods, the flow electrochemical method and the atomic absorption spectrometric method have been used to analyse the content of potentially toxic chemical elements in leachate. The analysis of leachate samples, in order to find out the values of exchange reactions in soil, was carried out by potentiometry. Ascertained values of exchange reactions in soil ranged from 5.6 to 7.2. According to the calculated indices of dependencies, the development of pH/KCl values can be evaluated as moderately dynamic. The calculated indices of the Spearman‘s correlation coefficient for exchange reactions in soil demonstrate statistically significant dependence, especially for zinc and cadmium.

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Zubenya, Natalia, Natalia Zubenya, Zholt Kormosh, Diana Saribekova, Diana Saribekova, Sergei Sukharev, and Sergei Sukharev. "Potentiometric Membrane Sensors for Levamisole Determination." Mediterranean Journal of Chemistry 6, no. 2 (November 15, 2016): 7–14. http://dx.doi.org/10.13171/mjc61/016111516/kormosh.

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The ion pair (IP) of levamisole with BiI4 - (SbI4 - ) for the levamisole-selective sensor with a PVC membrane containing - ions were developed. Thermal behavior of obtained IP was investigated by differential thermal analysis that would show the thermal stability and the character of the decomposition of the complex. The thermolysis of Lev+BiI4 - IP undergoes three stages that fit a theoretical interpretation. The linearity ranges of levamisole sensors function are 7.9 ×10-6 – 1×10-1 (7.9 ×10-5 – 1×10-1 ) M. The Nernstian slope of 50.6 – 53.4 mV pC−1 and detection limit of 5.0 × 10−5 – 1.5 × 10−4) M. The working range of pH is 2.8 – 6.0. The efficiency of the use of electrodes for levamisole content control in pharmaceutical preparations was shown by direct potentiometry and potentiometric titration methods.

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Refait, Ph, C. Bon, L. Simon, G. Bourrié, F. Trolard, J. Bessière, and J. M. R. Gènin. "Chemical composition and Gibbs standard free energy of formation of Fe(II)-Fe(III) hydroxysulphate green rust and Fe(II) hydroxide." Clay Minerals 34, no. 3 (September 1999): 499–510. http://dx.doi.org/10.1180/000985599546280.

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AbstractThe redox potential and pH of aerated suspensions of iron(II) hydroxide in sulphate–containing aqueous solutions are measured during the oxidation process. Plateaux corresponding to the equilibrium conditions between Fe(OH)2(s) and Fe(II)-Fe(III) hydroxysulphate GR2(SO2-4)(s) on the one hand, and between GR2(SO2-4)(s) and FeOOH(s) on the other hand, are displayed. Potentiometry, voltammetry, pH-metry and Mössbauer spectroscopy are applied to follow all reactions. The thermodynamic meaning of the measured potential of the first plateau which corresponds to the GR2(SO2-4)(s)/Fe(OH)2(s) equilibrium is demonstrated. The chemical composition of GR2(SO2-4)(s) is found to be FeII4 FeIII2(OH)12SO4·nH2O all along the oxidation process, implying that this compound must be considered as a pure phase with a well-defined composition. The Gibbs standard free energy of formation or chemical potential μ°[GR2(SO2-4)(s)] in ‘anhydrous form’ (n = 0) is determined at −3790±10 kJ mol-1. A consistent value of μ°[Fe(OH)2(s)] at −490±1 kJ mol-1 is obtained.

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Abramovic, Biljana, Vesna Anderluh, Andjelka Topalov, and Ferenc Gaal. "Direct photolysis and photocatalytic degradation of 2-amino-5-chloropyridine." Journal of the Serbian Chemical Society 68, no. 12 (2003): 961–70. http://dx.doi.org/10.2298/jsc0312961a.

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The direct photolysis and photocatalytic degradation of a pyridine pesticide analogue, 2-amino-5-chloropyridine, were investigated employing different analytical techniques ? potentiometry, for monitoring the pH and chloride genera- tion, spectrophotometry, for studying the degradation of the pyridine moiety, ion chromatography, for monitoring nitrate formation, and total organic carbon analysis for investigating the efficiency of the process. The photocatalytic degradation was studied in aqueous suspensions of titanium dioxide under illumination by UV light. It was found that chloride evolution was a zero-order reaction which takes place by direct photolysis, in that way differing from the degradation of the pyridine moiety, which takes place in the presence of titanium dioxide. Changes in pH during degradation indicate the formation of acidic intermediates and nitrate in addition to chloride. The effect of the initial substrate concentration was also investigated by monitoring the reaction of chloride generation as well as the degradation reaction of the pyridine moiety. It was found that degradation of the parent compound (2.5 mmol/dm3) by direct photolysis is completed in about 20 minutes, and of the pyridine moety by photocatalytic degradation in about nine hours. Based on the obtained data a possible reaction mechanism is proposed.

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Khan, Munezza Ata, Umar Ansari, and Murtaza Najabat Ali. "Real-time wound management through integrated pH sensors: a review." Sensor Review 35, no. 2 (March 16, 2015): 183–89. http://dx.doi.org/10.1108/sr-08-2014-689.

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Purpose – Real-time monitoring of wound or injured tissues is critical for speedy recovery, and the onset of a cascade of biochemical reactions provides potential biomarkers that facilitate the process of wound monitoring, e.g. pH, temperature, moisture level, bacterial load, cytokines, interleukins, etc. Among all the biomarkers, pH has been known to have a profound impact on the wound healing process, and is used to determine the incidence of bacterial infection of the wound (persistently elevated alkaline pH), proteolytic activity at the site of injury, take rate in skin grafting, wound healing stage and preparation for wound debridement. Design/methodology/approach – This review highlights the significance of pH in determination of clinical parameters and for selection of an appropriate treatment regime, and it presents an in-depth analysis of the designs and fabrication methods that use integrated pH sensors, which have been reported to date for the real-time monitoring of wound healing. Findings – For an expedited wound healing process, the significance of pH mandated the need of an integrated sensor system that would facilitate real-time monitoring of healing wounds and obviate the requirement of redressing or complicated testing procedures, which are both labor-intensive and painful for the patient. The review also discussed different types of sensor systems which were developed using hydrogel as a pH-responsive system coupled with voltammetry, potentiometry, impedimetric and flex-circuit inductive transducer systems. All of the mentioned devices have considerable potential for clinical applications, and there is need of in vivo testing to validate their efficiency and sensitivity under practical scenarios. Originality/value – This manuscript is an original review of literature, and permission has been granted to use the figures from previously published papers.

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Foti, Claudia, and Ottavia Giuffrè. "Interaction of Ampicillin and Amoxicillin with Mn2+: A Speciation Study in Aqueous Solution." Molecules 25, no. 14 (July 8, 2020): 3110. http://dx.doi.org/10.3390/molecules25143110.

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A potentiometric and UV spectrophotometric investigation on Mn2+-ampicillin and Mn2+-amoxicillin systems in NaCl aqueous solution is reported. The potentiometric measurements were carried out under different conditions of temperature (15 ≤ t/°C ≤ 37). The obtained speciation pattern includes two species for both the investigated systems. More in detail, for system containing ampicillin MLH and ML species, for that containing amoxicillin, MLH2 and MLH ones. The spectrophotometric findings have fully confirmed the results obtained by potentiometry for both the systems, in terms of speciation models as well as the stability constants of the formed species. Enthalpy change values were calculated via the dependence of formation constants of the species on temperature. The sequestering ability of ampicillin and amoxicillin towards Mn2+ was also evaluated under different conditions of pH and temperature via pL0.5 empirical parameter (i.e., cologarithm of the ligand concentration required to sequester 50% of the metal ion present in traces).

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Shen, Hongda, Terence J. Cardwell, and Robert W. Cattrall. "Determination of Ammonia in Waste Waters by a Differential pH Method Using Flow Injection Potentiometry and a Nonactin-Based Sensor." Analyst 122, no. 1 (1997): 89–93. http://dx.doi.org/10.1039/a605155c.

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40

Häggman, Leif, Anders Cassel, and Ingmar Persson. "Short Strong Hydrogen Bonds can Hinder Complex Formation: A Stability and Structure Study of Copper(II) Alkyl-N-iminodiacetic Acid Complexes in Aqueous Systems and Solid State." Journal of Solution Chemistry 50, no. 2 (February 2021): 203–19. http://dx.doi.org/10.1007/s10953-020-01050-7.

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AbstractIn the present study the solution and coordination chemistry of copper(II)–alkyl-N-iminodiacetate systems are studied in aqueous solution by potentiometry, using ion selective copper and pH electrodes, EXAFS (extended X-ray absorption fine structure) and dye probe molecular absorption spectrophotometry. Alkyl-N-iminodiacetates with varying alkyl chain length, methyl (CH3–), n-hexyl (C6H13–), n-dodecyl (C12H25–) and n-octadecyl (C18H37–) were used to tune the amphiphilic properties of the ligands. The polar head groups have both oxygen (hard Lewis base) and nitrogen donor (border-line Lewis base) atoms. This means that metal ions with different bonding characteristics may bind these ligands differently. Furthermore, the chelating properties of the polar head group may be regulated by pH as the acid–base properties of the imine and carboxylic acid groups are different. Copper(II) forms two stable complexes with alkyl-N-iminodiacetates with short alkyl chains, present as monomers in aqueous solution, log10β1 = 11.10(2), log10β2 = 19.5(2) for methyl-N-iminodiacetate, and log10β1 = 12.22(4), log10β2 = 21.9(2) for n-hexyl-N-iminodiacetate. n-Octadecyl-N-iminodiacetic acid, present as large aggregates in acidic aqueous solution, has short strong hydrogen bonds between carboxylic acid and carboxylate groups in the surface of the aggregates, which hinder complex formation at pH values below 4, obstructs it in the pH region 4–7, while the complex formation behaves as for short-chained alkyl-N-iminodiacetates at pH > 7. The structure around copper in copper(II)–alkyl-N-iminodiacetate complexes in aqueous solution and solid state formed at different pH values and copper(II):alkyl-N-iminodiacetate ratios has been determined by EXAFS. The coordination chemistry of copper(II) shows four strong bonds in the equatorial plane, and two different Cu–O/N bond distances, ca. 0.2 Å apart, in the axial positions of a non-centrosymmetric tetragonally elongated octahedron.

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Cavaliere, Franco, Simonetta Masieri, Stefania Nori, Sergio I. Magalini, and Salvatore R. Allegra. "Carbonic Anhydrase in Human Nasal Epithelium: Localization and Effect of the Inhibition by Dichlorphenamide." American Journal of Rhinology 10, no. 2 (March 1996): 113–18. http://dx.doi.org/10.2500/105065896781795003.

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Carbonic anhydrase has not hitherto been reported in nasal mucosa. In the first part of this study, five specimens of human nasal mucosa from the inferior turbinate were obtained from five healthy subjects and tested for this enzyme with a histochemical reaction. Carbonic anhydrase was identified in the columnar ciliated respiratory epithelium, but was absent in the adjacent stratified squamous epithelium. The effect of the inhibition of this enzyme on the pH values and Na, K, and Cl activity in nasal secretion was subsequently investigated. Fifteen patients, affected by endocranial hypertension and to whom dichlorphenamide—an inhibitor of carbonic anhydrase—was administered, were studied. The pH value, determined with a surface electrode before giving the drug and 30, 60, and 90 minutes later, significantly increased and reached a peak at 60 minutes. Na, K, and Cl concentration was assessed by indirect potentiometry in the nasal secretion and in the plasma both before giving dichlorphenamide and 60 minutes later. Although no change was observed in the plasma, in the nasal secretion Na and Cl concentration increased and K concentration decreased. As a consequence, the gradients of Na and K between plasma and secretion decreased, and that of Cl increased. We assume analogous changes in the rate of transport through the mucosa to occur. These results thus suggest that carbonic anhydrase is involved in control of the pH of nasal secretions as well as in the electrolyte transport through the epithelium.

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Farkas, Etelka, Dávid Bátka, Hajnalka Csóka, and Nóra V. Nagy. "Interaction of Imidazole Containing Hydroxamic Acids with Fe(III): Hydroxamate Versus Imidazole Coordination of the Ligands." Bioinorganic Chemistry and Applications 2007 (2007): 1–8. http://dx.doi.org/10.1155/2007/96536.

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Solution equilibrium studies on Fe(III) complexes formed with imidazole-4-carbohydroxamic acid (Im-4-Cha), N-Me-imidazole-4-carbohydroxamic acid (N-Me-Im-4-Cha), imidazole-4-acetohydroxamic acid (Im-4-Aha), and histidinehydroxamic acid (Hisha) have been performed by using pH-potentiometry, UV-visible spectrophotometry, EPR, ESI-MS, andH-NMR methods. All of the obtained results demonstrate that the imidazole moiety is able to play an important role very often in the interaction with Fe(III), even if this metal ion prefers the hydroxamate chelates very much. If the imidazole moiety is inα-position to the hydroxamic one (Im-4-Cha and N-Me-Im-4-Cha) its coordination to the metal ion is indicated unambiguously by our results. Interestingly, parallel formation of (Nimidazole,Ohydroxamate), and (Ohydroxamate,Ohydroxamate) type chelates seems probable with N-Me-Im-4-Cha. The imidazole is inβ-position to the hydroxamic moiety in Im-4-Aha and an intermolecular noncovalent (mainly H-bonding) interaction seems to organize the intermediate-protonated molecules in this system. Following the formation of mono- and bishydroxamato mononuclear complexes, only EPR silent species exists in the Fe(III)-Hisha system above pH 4, what suggests the rather significant “assembler activity” of the imidazole (perhaps together with the ammonium moiety).

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Miller, Adriana, Agnieszka Matera-Witkiewicz, Aleksandra Mikołajczyk, Joanna Wątły, Dean Wilcox, Danuta Witkowska, and Magdalena Rowińska-Żyrek. "Zn-Enhanced Asp-Rich Antimicrobial Peptides: N-Terminal Coordination by Zn(II) and Cu(II), Which Distinguishes Cu(II) Binding to Different Peptides." International Journal of Molecular Sciences 22, no. 13 (June 28, 2021): 6971. http://dx.doi.org/10.3390/ijms22136971.

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The antimicrobial activity of surfactant-associated anionic peptides (SAAPs), which are isolated from the ovine pulmonary surfactant and are selective against the ovine pathogen Mannheimia haemolytica, is strongly enhanced in the presence of Zn(II) ions. Both calorimetry and ITC measurements show that the unique Asp-only peptide SAAP3 (DDDDDDD) and its analogs SAAP2 (GDDDDDD) and SAAP6 (GADDDDD) have a similar micromolar affinity for Zn(II), which binds to the N-terminal amine and Asp carboxylates in a net entropically-driven process. All three peptides also bind Cu(II) with a net entropically-driven process but with higher affinity than they bind Zn(II) and coordination that involves the N-terminal amine and deprotonated amides as the pH increases. The parent SAAP3 binds Cu(II) with the highest affinity; however, as shown with potentiometry and absorption, CD and EPR spectroscopy, Asp residues in the first and/or second positions distinguish Cu(II) binding to SAAP3 and SAAP2 from their binding to SAAP6, decreasing the Cu(II) Lewis acidity and suppressing its square planar amide coordination by two pH units. We also show that these metal ions do not stabilize a membrane disrupting ability nor do they induce the antimicrobial activity of these peptides against a panel of human pathogens.

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Lenar, Nikola, Robert Piech, Jan Wyrwa, and Beata Paczosa-Bator. "Potassium-Selective Solid-Contact Electrode with High-Capacitance Hydrous Iridium Dioxide in the Transduction Layer." Membranes 11, no. 4 (April 4, 2021): 259. http://dx.doi.org/10.3390/membranes11040259.

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This work presents new material for solid-contact layers—hydrous iridium dioxide IrO2·2H2O, characterized by high electrical capacitance value, evaluated using chronopotentiometry (1.22 mF) and electrochemical impedance spectroscopy (1.57 mF). The remarkable electrical parameters of layers resulted in great analytical parameters of IrO2·2H2O-contacted potassium-selective electrodes. Various parameters of ion-selective electrodes were examined in the scope of this work using a potentiometry method including: linear range, repeatability, stability of potentiometric response and sensitivity to varying measurement conditions. The analytical parameters obtained for solid-contact electrodes were compared with the ones obtained for coated disc electrodes to evaluate the influence of the iridium dioxide layer. The linear range of the IrO2·2H2O-contacted K+-selective electrodes covered concentrations of K+ ions from 10−6 to 10−1 M and the potential stability was estimated at 0.097 mV/h. The IrO2·2H2O-contacted electrodes turned out to be insensitive to varying light exposure and changes in the pH values of measured solutions (in the pH range of 2 to 10.5). A water layer test proved that, contrary to the coated disc electrode, the substantial water film is not formed between the ion-selective membrane and iridium dioxide layer.

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Lin, Gui Feng, Yan Hong Wang, Guo Chen Li, Wen Bai, Hong Zhang, and Shi Cheng Wang. "Construction and Application of Molecularly Imprinted Film Sensor on Determination of Chlorpyrifos in Water." Advanced Materials Research 936 (June 2014): 843–49. http://dx.doi.org/10.4028/www.scientific.net/amr.936.843.

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Molecularly imprinted microspheres for recognition of chlorpyrifos were prepared by thermal initiation and precipitation polymerization, and were characterized using scanning electron microscope and infrared spectroscopy. Binding characteristics of the microspheres were also investigated. Sensitive film electrode of chlorpyrifos was prepared using the microspheres above on the surface of gold electrode by spin coating. Electrochemical sensor was constructed with the electrode prepared above as recognition element, and the response characteristics of the sensor to chlorpyrifos in water were investigated based on constant-current potentiometry. It was shown that a reasonable linear response curve between potential and concentration was obtained from 1.0×10-12mol/L to 2.0×10-8mol/L, with a detection limit of 1.0×10-13mol/L. The suitable pH was 2.2~3.4,and response time was 10 min. The imprinted electrode showed relatively high selectivity to chlorpyrifos and was applied to the analysis of chlorpyrifos in the simulated river samples with recovery rates ranging from 89% to 105%.

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Vasilyeva, Marina S., Vladimir S. Rudnev, Irina V. Lukiyanchuk, N. E. Zabudskaya, and I. V. Chasovnikov. "Sn-Containing Oxide Coatings: Formation, Composition, Electroanalytical and Catalytic Properties." Key Engineering Materials 806 (June 2019): 70–75. http://dx.doi.org/10.4028/www.scientific.net/kem.806.70.

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Sn-containing oxide coatings were prepared via plasma electrolytic oxidation (PEO) of Ti plate in the electrolytes with [SnII-EDTA]2- complex anions or SnO2 particles in the anode and anodic-cathodic modes. The coatings formed in electrolyte with SnO2 particles stabilized by SAS contain SnO2 and Sn0. In the electrolyte with [Sn-EDTA]2- complex anions, the SnO2-containing coatings were formed in the anodic mode while Sn0-containing ones were obtained in the anodic-cathodic mode. SnO2-containing structures formed in the electrolytes with [Sn-EDTA]2- anions are shown to be active in catalytic oxidation of CO into CO2 at temperatures above 350 °C. They can be the basis for the preparation of both carriers of catalytically active compounds and catalysts for redox reactions. Potentiometric tests showed that the Sn-containing PEO layers on titanium exhibit the most characteristic pH function for the metal oxide electrodes in the direct potentiometry and acid-base titration.

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Kim, Junghwan, Dae Hee Kim, Jin Cheol Yang, Jae Sang Kim, Ji Ha Lee, and Sung Ho Jung. "Beryllium-Ion-Selective PEDOT Solid Contact Electrode Based on 9,10-Dinitrobenzo-9-Crown-3-Ether." Sensors 20, no. 21 (November 9, 2020): 6375. http://dx.doi.org/10.3390/s20216375.

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A beryllium(II)-ion-selective poly(ethylenedioxythiophene) (PEDOT) solid contact electrode comprising 9,10-dinitrobenzo-9-crown-3-ether was successfully developed. The all-solid-state contact electrode, with an oxygen-containing cation-sensing membrane combined with an electropolymerized PEDOT layer, exhibited the best response characteristics. The performance of the constructed electrode was evaluated and optimized using potentiometry, conductance measurements, constant-current chronopotentiometry, and electrochemical impedance spectroscopy (EIS). Under optimized conditions, which were found for an ion-selective membrane (ISM) composition of 3% ionophore, 30% polyvinylchloride (PVC), 64% o-nitro phenyl octyl ether (o-NPOE), and 3% sodium tetraphenylborate (NaTPB), the fabricated electrode exhibited a good performance over a wide concentration range (10−2.5–10−7.0 M) and a wide pH range of 2.0–9.0, with a Nernstian slope of 29.5 mV/D for the beryllium (II) ion and a detection limit as low as 10−7.0 M. The developed electrode shows good selectivity for the beryllium(II) ion over alkali, alkaline earth, transition, and heavy metal ions.

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Hassan, Saad S. M., and Mona A. Ahmed. "Polyvinyl Chloride Matrix Membrane Electrodes for Manual and Flow Injection Analysis of Chloroquine in Pharmaceutical Preparations." Journal of AOAC INTERNATIONAL 74, no. 6 (November 1, 1991): 900–905. http://dx.doi.org/10.1093/jaoac/74.6.900.

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Abstract Two types of polyvinyl chloride (PVC) matrix membrane electrodes responsive to the antimalarial drug chloroquine have been constructed, electrochemically evaluated, compared, and used in pharmaceutical analysis. Type 1 is the classic PVC model with chloroquine-tetraphenylborate (TPB) sensor; Type 2 is a coated silver disk without internal filling solution. Both electrode types exhibited rapid linear potentiometric response to the logarithmic concentration of diprotonated chloroquine cation in the 10−1–10−6M range with calibration slopes 28-30 mV/concentration decade over the pH range 1.8-6.2. These electrodes were sensitive enough to permit determination of chloroquine phosphate at concentrations as low as 5 μg/mL with good accuracy and precision. Determination of chloroquine in various pharmaceutical preparations using direct potentiometry and potentiometric titration with NaTPB gave an average recovery of 98.8% of the nominal values (SD 0.5%). The Type 2 electrode was also assessed in a flow-through sandwich cell for flow injection analysis. Results were compared with data obtained by the U.S. Pharmacopeia method.

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T Seifert, S., R. Krause, K. Gloe, and T. Henle. "Copper(II)-complexation by non enzymatically glycated peptides." Czech Journal of Food Sciences 22, SI - Chem. Reactions in Foods V (January 1, 2004): S106—S108. http://dx.doi.org/10.17221/10628-cjfs.

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The purpose of our work was to examine the metal binding abilities of selected peptide bound Maillard reaction products (MRPs). The Nα-hippuryl-protected MRPs Nε-fructoselysine and Nε-carboxymethyllysine were synthesised and measurement of stability constants for complexes formed with the physiologically important metal ions copper(II) and zinc(II) was carried out in aqueous solution (T = 298.1 K; I = 0.1M KNO3) using pH-potentiometry. The stability constants of Nε-fructoselysine and Nε-carboxymethyllysine with Cu(II) proved that new coordination centres are formed by the nonenzymatic glycation of proteins. With zinc(II) no complexation was observed. Physiological consequences are discussed, but further studies are necessary in order to clarify the effects of this phenomenon.

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Noriega-Navarro, Roxana, Jésica Castro-Medina, Martha V. Escárcega-Bobadilla, and Gustavo A. Zelada-Guillén. "Control of pH-Responsiveness in Graphene Oxide Grafted with Poly-DEAEMA via Tailored Functionalization." Nanomaterials 10, no. 4 (March 27, 2020): 614. http://dx.doi.org/10.3390/nano10040614.

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Polymer-grafted nanomaterials based on carbon allotropes and their derivatives (graphene oxide (GO), etc.) are typically prepared by successive reaction stages that depend upon the initial functionalities in the nanostructure and the polymerization type needed for grafting. However, due to the multiple variables involved in the functionalization steps, it is commonly difficult to predict the properties in the final product and to correlate the material history with its final performance. In this work, we explored the steps needed to graft the carboxylic acid moieties in GO (COOH@GO) with a pH-sensitive polymer, poly[2-(diethylamino)ethyl methacrylate] (poly[DEAEMA]), varying the reactant ratios at each stage prior to polymerization. We studied the combinatorial relationship between these variables and the behavior of the novel grafted material GO-g-poly[DEAEMA], in terms of swelling ratio vs. pH (%Q) in solid specimens and potentiometric response vs. Log[H+] in a solid-state sensor format. We first introduced N-hydroxysuccinimide (NHS)-ester moieties at the –COOH groups (GO-g-NHS) by a classical activation with N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide (EDC). Then, we substituted the NHS-ester groups by polymerizable amide-linked acrylic moieties using 2-aminoethyl methacrylate (AEMA) at different ratios to finally introduce the polymer chains via radical polymerization in an excess of DEAEMA monomer. We found correlated trends in swelling pH range, interval of maximum and minimum swelling values, response in potentiometry and potentiometric linear range vs. Log[H+] and could establish their relationship with the combinatorial stoichiometries in synthetic stages.

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Journal articles on the topic 'PH-potentiometry'

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