scholarly journals Zn2+-heparin interaction studied by potentiometric titration

1992 ◽  
Vol 287 (3) ◽  
pp. 849-853 ◽  
Author(s):  
D Grant ◽  
W F Long ◽  
F B Williamson
Keyword(s):  
Indirect Method ◽  
Solution Phase ◽  
Equilibrium Thermodynamic ◽  
Ph Change ◽  
Saturation Binding ◽  
Heparin Interaction ◽  
Low Concentrations ◽  
Initial Ph ◽  
Isothermal Saturation ◽  
Direct Proportionality

Measurement of the decrease in pH that accompanies the addition of Zn2+ to heparin in solution provided an indirect method of examining cation-polyanion interaction. Construction of plots analogous to isothermal saturation binding plots revealed the existence, for defined conditions of interaction, of a [heparin]-independent direct proportionality between the fraction of the maximal pH change occurring and the [Zn2+]/[heparin disaccharide] ratio. This accords with results from polarimetric examination of Ca(2+)- and Cu(2+)-heparin interactions. It suggests that, under the conditions used, cation-heparin interaction may result in the formation of a complex that exists in a colloid-like phase, between which and the aqueous phase, exchange of cations does not follow simple solution-phase reversible equilibrium thermodynamic behaviour. The results suggest that the putative Zn(2+)-containing complex is less stable in the presence of NaCl than is the corresponding Ca(2+)-containing complex. Addition of Zn2+ to low concentrations of heparins is accompanied by the usual decrease in pH, followed by a removal of H+ from solution as the [Zn2+]/[heparin disaccharide] ratio increases, suggesting dissolution of the putative complex. This reversal of the initial pH change was not seen for most other cation-heparin interactions under the conditions studied.

scholarly journals A Theoretical and Experimental Study of Electrochemical pH Control at Gold Interdigitated Microband Arrays

2021 ◽  
Author(s):  
Bernardo Patella ◽  
Robert Daly ◽  
Ian Seymour ◽  
Pierre Lovera ◽  
James Rohan ◽  
...  
Keyword(s):  
Electrode Array ◽  
Ph Control ◽  
Reduction Peak ◽  
Solution Ph ◽  
Ph Indicator ◽  
Ph Change ◽  
Initial Ph ◽  
The Impact ◽  
Strong Acids

In electroanalysis, solution pH is a critical parameter that often needs to be adjusted and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without additional reagents. FEA simulations have been performed to guide experimental design for both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode array in buffered solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap. The final pH achieved at both, protonators and sensor electrodes, after 1 second, was shown to be largely uninfluenced by the initial pH of the solution. The impact of buffer concentration was modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., by cycling a gold electrode in solution and identifying the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model’s prediction

scholarly journals Technical note: Stability of tris pH buffer in artificial seawater stored in bags

Ocean Science ◽  
2021 ◽  
Vol 17 (3) ◽  
pp. 819-831
Author(s):  
Wiley H. Wolfe ◽  
Kenisha M. Shipley ◽  
Philip J. Bresnahan ◽  
Yuichiro Takeshita ◽  
Taylor Wirth ◽  
...  
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Technical Note ◽  
Artificial Seawater ◽  
Upper And Lower Bounds ◽  
Sensor Calibration ◽  
Time Data ◽  
Ph Change ◽  
Ph Measurements ◽  
Experimental Conditions ◽  
Initial Ph

Abstract. Equimolal tris (2-amino-2-hydroxymethyl-propane-1,3-diol) buffer in artificial seawater is a well characterized and commonly used standard for oceanographic pH measurements. We evaluated the stability of tris pH when stored in purportedly gas-impermeable bags across a variety of experimental conditions, including bag type and storage in air vs. seawater over 300 d. Bench-top spectrophotometric pH analysis revealed that the pH of tris stored in bags decreased at a rate of 0.0058±0.0011 yr−1 (mean slope ±95 % confidence interval of slope). The upper and lower bounds of expected pH change at t=365 d, calculated using the averages and confidence intervals of slope and intercept of measured pH change vs. time data, were −0.0042 and −0.0076 from initial pH. Analyses of total dissolved inorganic carbon confirmed that a combination of CO2 infiltration and/or microbial respiration led to the observed decrease in pH. Eliminating the change in pH of bagged tris remains a goal, yet the rate of pH change is lower than many processes of interest and demonstrates the potential of bagged tris for sensor calibration and validation of autonomous in situ pH measurements.

Mechanisms of aluminum tolerance in Triticum aestivum (wheat). IV. The role of ammonium and nitrate nutrition

1985 ◽  
Vol 63 (12) ◽  
pp. 2181-2186 ◽  
Author(s):  
Gregory J. Taylor ◽  
Charles D. Foy
Keyword(s):  
Triticum Aestivum ◽  
Phase Ii ◽  
Aluminum Tolerance ◽  
Triticum Aestivum L ◽  
Al Tolerance ◽  
Solution Ph ◽  
Ph Change ◽  
Initial Ph ◽  
Nutrient Solutions

Five cultivars of Triticum aestivum L. (wheat) were grown for 21 days in solution cultures with aluminum (+Al) (74 μM) and without Al (−Al) at an initial pH of 4.5. Patterns of nitrogen depletion and pH change were biphasic. Ammonium [Formula: see text] was rapidly depleted and solution pH declined during phase I. Depletion of nitrate [Formula: see text] was most rapid and solution pH increased after [Formula: see text] was exhausted from solutions (phase II). Cultivar tolerance to Al was negatively correlated with the rate of pH decline induced by cultivars, and the rate of pH decline was positively correlated with the rate at which cultivars depleted [Formula: see text] from +Al and −Al nutrient solutions. Cultivar tolerance to Al was also negatively correlated with the rate of [Formula: see text] depletion from +Al and −Al solutions. Cultivar tolerance to Al was positively correlated with the rate of [Formula: see text] depletion during phase II but only when plants were grown with Al. These results support the hypothesis that differential Al tolerance among cultivars of T. aestivum is caused by differences in the rate of [Formula: see text], and possibly [Formula: see text], uptake. Such diffferences in N preference may have caused differences in pH and Al solubility in the nutrient solutions.

COMPARING SEGREGATION PROFILES OF Sn AND Sb IN SINGLE AND POLYCRYSTALLINE Cu

2012 ◽  
Vol 19 (01) ◽  
pp. 1250006
Author(s):  
J. K. O. ASANTE ◽  
W. D. ROOS
Keyword(s):  
Electron Spectroscopy ◽  
Auger Electron ◽  
Indirect Method ◽  
Bulk Diffusion ◽  
Solute Segregation ◽  
Interaction Energies ◽  
Surface Enrichment ◽  
Experimental Conditions ◽  
Low Concentrations ◽  
Equilibrium Segregation

The kinetics as well as the equilibrium segregation profiles of very low concentrations of Sn (0.14 at.%) and Sb (0.12 at.%) in a polycrystalline Cu sample were measured by Auger electron spectroscopy. These profiles were compared to those from a Cu(100) , Sb , Sn ternary single crystal which was subjected to the same experimental conditions. The results are explained in terms of solute segregation to grain boundaries and surface interfaces. The comparison also indicate that not only bulk diffusion, interactions and segregation energies play a role in the surface enrichment of the species, but in polycrystalline samples, the doping order of the specimen is to be considered as well. The differences in interaction energies of Sn and Sb also suggest an indirect method of measuring the concentrations of nonsegregating impurities in polycrystalline samples.

scholarly journals Technical note: Interpreting pH changes

2021 ◽  
Vol 18 (4) ◽  
pp. 1407-1415
Author(s):  
Andrea J. Fassbender ◽  
James C. Orr ◽  
Andrew G. Dickson
Keyword(s):  
Technical Note ◽  
Ion Concentration ◽  
Ph Change ◽  
Ph Measurements ◽  
Hydrogen Ion Concentration ◽  
Ph Changes ◽  
The Past ◽  
Initial Ph ◽  
Relative Change

Abstract. The number and quality of ocean pH measurements have increased substantially over the past few decades such that trends, variability, and spatial patterns of change are now being evaluated. However, comparing pH changes across domains with different initial pH values can be misleading because a pH change reflects a relative change in the hydrogen ion concentration ([H+], expressed in mol kg−1) rather than an absolute change in [H+]. We recommend that [H+] be used in addition to pH when describing such changes and provide three examples illustrating why.

Simple and Sensitive Determination of Urea in Serum and Urine

1992 ◽  
Vol 38 (5) ◽  
pp. 619-623 ◽  
Author(s):  
J L Orsonneau ◽  
C Massoubre ◽  
M Cabanes ◽  
P Lustenberger
Keyword(s):  
Urine Samples ◽  
Ph Change ◽  
Low Concentrations ◽  
Analytical Recovery ◽  
Urea Determination ◽  
Sensitive Determination ◽  
Ph Increase ◽  
Clinically Significant ◽  
Hydrolysis Of

Abstract In this method for serum and urinary urea determination, the same reagent is used without predilution of urine samples. The method is based on the pH increase resulting from the ammonia released by urease hydrolysis of urea. o-Cresolphthalein complexone is used to monitor the pH change colorimetrically. Urea concentration and absorbance at 570 nm are linearly related for concentrations as great as 600 mmol/L for urine samples and 100 mmol/L for serum. There are no clinically significant interferences from physiological substances or drugs, and precision and accuracy are excellent (CV approximately 2%, except at very low concentrations in serum; analytical recovery was 99% in urine, 100% in serum). Results by this method (y) and by the Astra method (x) for urine correlated well (y = 0.991x - 2.87, Sy/x = 9.21, r = 0.994), as did the results by this method and by the total enzymatic method (x') for serum (y = 1.002x' + 0.192, Sy/x' = 0.598, r = 0.997). This method is applicable to automated as well as manual instruments, and one-reagent or two-reagent formats can be used.

Exchange and solution phase chemistry of acid, highly weathered soils .I. Characteristics of soils and the effects of lime and gypsum amendments

Soil Research ◽  
1994 ◽  
Vol 32 (2) ◽  
pp. 251 ◽  
Author(s):  
NW Menzies ◽  
LC Bell ◽  
DG Edwards
Keyword(s):  
Soil Solution ◽  
Exchange Capacity ◽  
Solution Phase ◽  
Exchangeable Cation ◽  
Solution Ph ◽  
Ph Change ◽  
Median Concentration ◽  
Surface Samples ◽  
Weathered Soils ◽  
Highly Weathered Soils

Exchange and solution phase characteristics were evaluated on surface and subsoil horizons of 60 acid, highly weathered soils in the unamended state, and on 39 of the surface horizons following addition of CaCO3 or CaSO4.2H2O. Soil solutions from unamended surface samples were dominated by Na (median concentration 0.65 mM), while the other major cations were present at lower levels (median concentrations: Ca, 0.09; Mg, 0.14; K, 0.28 mM). This pattern was more pronounced in the subsoil samples where the median concentrations of the nutrient cations were < 0.05 mM, whereas the median concentration of Na was 0.28 mM. The cation exchange capacity of surface samples was dominated by Ca, Mg and Al, while Al was the major exchangeable cation in the subsoil. Addition Of CaSO4.2H2O decreased soil solution pH and increased electrical conductivity and the concentration of Ca, Mg, Na, K and Al in the soil solution. The soil solution pH change resulting from CaSO4.2H2O addition could not be predicted on the basis of the characteristics of the soil in the unamended state.

scholarly journals The affect of temperature and pH on the food safety of kombucha tea

2016 ◽  
Author(s):  
Ryan Hammel ◽  
BCIT School of Health Sciences, Environmental Health ◽  
Vanessa Karakilic ◽  
Fred Shaw
Keyword(s):  
Food Safety ◽  
Room Temperature ◽  
Sampling Period ◽  
Farmers Markets ◽  
Ph Change ◽  
Safety Issues ◽  
Food Borne ◽  
Kombucha Tea ◽  
Initial Ph ◽  
Food Borne Illness

  Objectives: Kombucha tea is becoming an increasingly popular food item within the Vancouver area. The tea is prepared through fermentation at room temperature during which acidic by-products are produced lowering the overall pH of the tea. Though the pH eventually reaches levels below 4.6, many health authorities prevent the sale of kombucha in farmers markets due to potential food safety issues. The initial pH before fermentation is around 5.5 and is then left at room temperature to ferment. As a result, this process potentially could allow for food borne illness causing organisms to survive and proliferate within the sugared tea. This research project will investigate the relationship of pH and time during fermentation at both room and refrigeration temperatures. Fermentation within a refrigerator could provide a safer alternative fermentation method Methods: The pH was measured using a pH meter for 30 samples at both room and refrigeration temperatures providing a total of 60 samples. The pH was measured periodically every twelve hours for a total of 120 hours. The data was analyzed using a linear regression model to determine if the pH change over time was statistically significant. The time at which the pH dropped below 4.6 was also noted for food safety purposes Results: At room temperature the pH steadily decreased in a linear fashion throughout the entire sampling period, dropping below 4.6 within 12 hours. The pH decreased in a nearly identical fashion when fermented in a refrigerator for the first 72 hours of sampling. After the 72 hour mark the pH stabilized at approximately 3.75, whereas the pH at room temperature continued to decrease down to 3.10 after the full sampling period Conclusion: The results indicate that kombucha tea becomes a non-potentially hazardous food within the first 12 hours of fermentation. The pH dropped below 4.6 after 12 hours at which point no food borne illness causing bacteria are able to survive and proliferate within the tea. The observed decrease in pH during the first 72 hours within a refrigerator is unlikely to have resulted from the fermentation process and therefore is not a feasible practice. Fermentation at room temperature appears to be a relatively safe process if home brewers are able to measure the pH change and carry out the process in a sanitary manner  

scholarly journals Changes of pH inβ-Lactoglobulin andβ-Casein Solutions during High Pressure Treatment

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Karsten Olsen ◽  
Bo B. Jespersen ◽  
Vibeke Orlien
Keyword(s):  
Tertiary Structure ◽  
Additive Model ◽  
Pressure Treatment ◽  
Ph Change ◽  
Pressure Dependency ◽  
Casein Solution ◽  
Initial Decrease ◽  
Initial Ph ◽  
Ph Decrease

The pH changes in the milk systems,β-lactoglobulin B,β-casein, and mixture ofβ-lactoglobulin andβ-casein (pH 7 and ionic strength 0.08 M) were measuredin situduring increasing pressure up to 500 MPa. An initial decrease to pH 6.7 was observed from 0.1 to 150 MPa forβ-lactoglobulin, followed by an increase to pH 7.3 at 500 MPa. The initial decrease is suggested to be caused by the deprotonation of histidine, while the increase is suggested to result from an increase of hydroxide ions due to the loss of tertiary structure. The change in pH of theβ-casein solution displayed an almost linear increasing pressure dependency up to a pH of 7.7 at 500 MPa. The limited tertiary structure ofβ-casein could allow exposure of all amino acids; thus the increase of pH can be caused by binding of water protons resulting in an increase of hydroxide ions. Addition ofβ-casein toβ-lactoglobulin (1:1) was found to suppress the initial pH decrease found for theβ-lactoglobulin solution. The pH change of the mixture did not suggest any intermolecular interaction, and a simple additive model is proposed to calculate the pH change of the mixture from the corresponding individual samples.

Effects of Acetic Acid and Arginine on pH Elevation and Growth of Bacillus licheniformis in an Acidified Cucumber Juice Medium†

2015 ◽  
Vol 78 (4) ◽  
pp. 728-737 ◽  
Author(s):  
ZHENQUAN YANG ◽  
XIA MENG ◽  
FREDERICK BREIDT ◽  
LISA L. DEAN ◽  
FLETCHER M. ARRITT
Keyword(s):  
Acetic Acid ◽  
Citric Acid ◽  
Bacillus Licheniformis ◽  
Pathogenic Bacteria ◽  
Ph Change ◽  
Ph Values ◽  
Vegetable Products ◽  
Initial Ph ◽  
Tomato Products ◽  
Ph Elevation

Bacillus licheniformis has been shown to cause pH elevation in tomato products having an initial pH below 4.6 and metabiotic effects that can lead to the growth of pathogenic bacteria. Because of this, the organism poses a potential risk to acidified vegetable products; however, little is known about the growth and metabolism of this organism in these products. To clarify the mechanisms of pH change and growth of B. licheniformis in vegetable broth under acidic conditions, a cucumber juice medium representative of a noninhibitory vegetable broth was used to monitor changes in pH, cell growth, and catabolism of sugars and amino acids. For initial pH values between pH 4.1 to 6.0, pH changes resulted from both fermentation of sugar (lowering pH) and ammonia production (raising pH). An initial pH elevation occurred, with starting pH values of pH 4.1 to 4.9 under both aerobic and anaerobic conditions, and was apparently mediated by the arginine deiminase reaction of B. licheniformis. This initial pH elevation was prevented if 5 mM or greater acetic acid was present in the brine at the same pH. In laboratory media, under favorable conditions for growth, data indicated that growth of the organism was inhibited at pH 4.6 with protonated acetic acid concentrations of 10 to 20 mM, corresponding to 25 to 50 mM total acetic acid; however, growth inhibition required greater than 300 mM citric acid (10-fold excess of the amount in processed tomato products) products under similar conditions. The data indicate that growth and pH increase by B. licheniformis may be inhibited by the acetic acid present in most commercial acidified vegetable products but not by the citric acid in many tomato products.

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