pH-metric Study Research Articles

PH-metric titration technique for the study of metal-complexes of substituted 2- Oxo-2H-Chromene-3-Carbohydrazide derivatives in solution: calculation of stability constants

Background: In coordination chemistry, the stability of complexes is expressed in terms of the formation constant of complexes. In coordination complexes, the temperature is very important. It plays an important role in complex formation reaction. Temperature affects metal-ligand stability constant (log K) and proton-ligand stability constant (pK). The metal ion Mn2+, Co2+, Ni2+, and Cu2+ at different temperatures form complexes with 4-sulfamethoxazoleazo-3-methyl-2-pyrazolin-5-one are reported. The metal-ligand stability constant (logK) and proton-ligand stability constant (pK) of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) with organic ligand n-[2-hydroxy-1-napthalydene]-2-methylanilline at 0.1 M ionic strength in 60% dioxane-water medium is studied. The study of thermodynamic parameters and stability constant of complexes of substituted thiazole Schiff bases with rare earth metal ions in mixed solvent is reported. Objective: The study of coordination compounds and a lot of work has been done on metal-ligand stability constant. The same transition metal ion form complexes with substituted pyrazole for this metal-ligand stability constant are determined. Method: Pointwise Calculation Method Half Integral Method. Result: The values of logK1 and logK2 are determined from the metal-ligand formation curve at formation numbers 0.5 and 1.5. In all cases, logK1 is greater than logK2. The ratio logK1/logK2 is positive and greater than one in all systems. This implies that there is little or no steric hindrance to the addition of the secondary ligand molecules. The difference between logK1 - logK2 is usually positive. If the difference between logK1 and logK2 is less than 2.5, simultaneous formation of 1:1 and 1:2 complexes occurs and if it is more than 2.5, then stepwise complex formation occurs. In the present case, in all systems, it is less than 2.5. This indicates the simultaneous formation of 1:1 and 1:2 complexes takes place. Conclusion: A pH-metric study of Substituted 2-oxo-2H-chromene-3-carbohydrazide derivatives with metal ions Fe(III), and Mn(II) occurs. The graphical representation of the curve shows that the acid + ligand curve is separated from the corresponding acid + ligand + metal curve in this system. The formation of a complex is indicated. Half integral method and pointwise calculation method give nearly similar results. The values of stability constants for all systems indicate that the complexes formed in these processes are stable.

Evolution of gastroesophageal reflux after laparoscopic vertical gastrectomy. A radiographic, manometric and pH-metric study.

the relationship between laparoscopic vertical gastrectomy (LVG) and gastroesophageal reflux (GER) is still controversial. Therefore, its study is of great interest in order to obtain definitive conclusions. The goal of the study was to establish whether LVG modifies pH-metric GER in obese patients and to analyze the associated factors. the first 26 patients who underwent LVG in our institution were enrolled in the study. A barium swallow, 24-hour ambulatory pH-metry and four-channel intraluminal esophageal manometry (IEM) were all performed before and one year after surgery. among the pH-metric data, there was a significant increase in the DeMeester index after the procedure (p = 0.028), while other parameters remained unchanged. Furthermore, 50% of patients with preoperative pH-metric GER had normal values at one year after surgery. IEM showed a decrease in lower esophageal sphincter (LES) pressure and in the mean wave amplitude at the distal third of the esophagus (p = 0.007 and p = 0.025, respectively). The rate of newly-developed hiatal hernias in the radiographic study was 36.4%. LVG mildly increases GER, which is likely related to the development of hiatal hernias and a decrease in LES pressure and esophageal sweep. However, LVG should not be contraindicated for patients with preoperative pH-metric GER, as this may clear after the procedure.

PH-Metric study of picolinic acid with Cu (II), Co (II) and Fe(II)ions

pH-Metric measurements of picolinic acid were studied with Cu(II), Co (II) and Fe(II)metal ions at 0.2 M ionic strength in water by Irving-Rossotti titration technique for determination of stability constants. 1: 1 complexes were formed in present investigation in between picolinic acid (PA) and Cu (II), Co (II)and Fe(II) metal ions. Values of proton-ligand stability constant (pK) and metal-ligand stability constants log k were evaluate and compared from resultant data.

Determination of the composition and stability constants of complexes in Co (II) - malic acid system

This paper presents the results of spectrophotometric and pH-metric study of Co (II) - malic acid system. Optical density of solutions was determined spectrophotometrically in a wide wavelength range at constant ionic strength and pH values. The compositions of the complexes formed in the system were determined. The results obtained are confirmed by pH titration. It was shown that the stability of complexes varies in the row: Co (II): H3Mt = 1:2 <1:1 < 2:1.

Studies of new phosphothreonine complexes formed in binary and ternary systems including biogenic amines and copper(II)

Binary and ternary systems of copper(II) with O-phospho-L-threonine (Thr-P) and biogenic amines (putrescine or spermidine or spermine) have been investigated. The studies were performed in aqueous solution. Overall stability constants of the complexes were determined by pH-metric study and the coordination sites were identified by 31P NMR, visible and electron paramagnetic resonance spectroscopies. Results of the equilibrium and spectral studies have shown that in the phosphothreonine binary system Cu(HThr-P), Cu(Thr-P) and Cu(Thr-P)(OH) are formed. In the binary system at low pH, only the phosphate group is involved in coordination but at higher pH, the efficiency of −PO4 2− is low and the amine and carboxylate are the main sites of coordination. Formation of complexes was established in ternary systems with all bioamines studied. In these systems the reaction centers of phosphothreonine are the same as in the binary systems: phosphate, carboxylate and amine. Additionally, amine groups from the polyamines (PAs) are involved in the complex formation. Besides the heteroligand complexes with intermolecular interactions, also molecular complexes with the protonated bioamine in the outer coordination sphere appeared. In these molecular species, PA was involved in non-covalent interactions with the anchoring phospho-threonine complex.

Solvent Effect on Protonation Equilibria of l-Aspartic Acid and Ethylenediamine in Dioxan–Water Mixtures

A pH-metric study of protonation equilibria of l-aspartic acid and ethylenediamine in dioxan-water media of varying composition (0–60 % v/v) has been made at different concentrations of the ligands maintaining an ionic strength of 0.16 mol l−1 at 303.0 K. The best fit chemical models are arrived at using MINIQUAD75 based on statistical parameters like crystallographic R factor, χ2, skewness and kurtosis. The variation in the protonation constants with the dielectric constant of the medium is attributed to the electrostatic and non electrostatic forces.

Ph-Metric Study of Binary and Ternary Complexes of Innertransition Metals With Carboxylic Acids and Amino Acids

The present work deals with the study of proton - ligands and metal- ligands Constant of Binary and ternary complexes. Where M= Innertranition metals, L= Primary ligands( malic acid, ,maleic acid and Malonic acid) and secondary ligands B = Glycine have been studied Potentiometrically in biologically relevant conditions. At ionic strength μ= 0.1M NaClO4. All the ligands forns 1:1:1 ternary complexes, the relative stability of ternary complexes expressed in terms of statistical parameter Δ log k and - Δ log k values suggest that the formation of ternary complexes are favorable and variation of Δ log k has been explained in terms of metal-ligand-п interaction, size of chelate ring, and steric factor.

The influence of copper(ii) ions on noncovalent interactions in the systems including phosphoserine and biogenic amines

Ternary systems of copper(II) complexes with phosphoserine and biogenic amines (putrescine or spermidine or spermine) have been investigated. The studies were performed in aqueous solution using the potentiometric method with computer analysis of the data, 13C and 31P nuclear magnetic resonance, visible and electron paramagnetic resonance spectroscopies. The composition and overall stability constants of the complexes were determined by the pH-metric study and the coordination sites were identified by spectroscopic methods. The reaction centres are phosphate, carboxyl and amine groups from phosphorylated serine as well as amine groups from polyamine. These centres are also the potential sites of the noncovalent interactions (in the systems without metal). In the systems studied only protonated complexes formed. Besides the heteroligand complexes and heteroligand complexes with intermolecular interactions, molecular complexes with the protonated bioamine in the outer coordination sphere appeared. In these molecular species polyamine was involved in noncovalent interactions with the anchoring phosphoserine complex.

(075). The extra-esophageal manifestations of GERD: pH-metric study about 289 cases

(075). The extra-esophageal manifestations of GERD: pH-metric study about 289 cases

PH-Metric study of gamma-irradiated table sugar for dosimetry purpose

Table sugar has been studied for a long time as a dosimeter in radiation accident and in high-dose dosimetry by using different analytical techniques especially electron paramagnetic resonance (EPR) and optical absorption spectrometry (OA). In this work, we report the results obtained by pH-metry on gamma-irradiated sugar. Table sugar samples were exposed to gamma radiation with doses of 0.1–58 kGy. Aqueous solutions of sugar were prepared with different concentrations ranged from 1% to 60% (w/w). It was found that sugar solutions showed strong decrease of pH up to concentration of 10% (w/w) followed by a slow decrease for the concentrations between 10 and 60% (w/w). Two possible mechanisms are proposed to explain the acidity increasing of the sugar solutions based on the existence of a carbonyl radical induced by gamma irradiation in solid table sugar with an open ring structure. Results for radiation response, post-irradiation change, reading temperature, dose-rate effect and repeatability are presented in this study. The results showed that pH-metric/sugar solution is an adequate high-dose dosimetric system in the dose range of 0.1–10 kGy.

Nocturnal gastroesophageal reflux disease in asthmatics patients: a pH-metric study on 81 cases

Zouiten, Lilia; Karoui, Sami; Belkhodja, Asma; Matri, Samira; Taieb Jomni, Mohamed; Boubaker, Jalel; Filali, Azza Author Information

PH-metric study of the setting reaction of monocalcium phosphate monohydrate/calcium oxide-based cements.

Hydraulic calcium phosphate cements (CPCs) that are used as osseous substitutes, set by an acid-base reaction between an acid calcium phosphate and a basic calcium salt (often a phosphate). In order to gain a better understanding of the setting of the monocalcium phosphate monohydrate-calcium oxide cement that we developed and in the aim to improve its mechanical properties, the setting reaction was studied by pH-metry. The two methods described in the literature were used. In the first, cement samples were prepared then crushed after different storage periods at 37 degrees C, 100% RH. The powder was then immersed in pure water with stirring and the pH was measured after equilibration. In the second technique, the starting materials were poured into water while stirring and the pH were followed over time. The two methods gave different results. The first procedure provided information concerning the pH of the surrounding liquid following the partial dissolution of the cement components, rather than any information about pH changes during setting. The second method is more appropriate to follow the pH variations during setting. In this second procedure, the effects of different parameters such as crushing time, stirring rate, liquid-to-powder (L/P) ratio and temperature were investigated. These parameters may impact substantially on the shape and position of the pH=f(t) curves. One or three pH jumps were observed during the setting depending on the composition of the liquid phase. The time at which these pH jumps occurred depended on the pH of the liquid phase, the concentration of the buffer, the crushing of starting materials, the L/P ratio and the temperature. Good linear correlations were obtained (i) between the time of the pH jumps and the L/P ratio and the temperature and (ii) between the time of the first pH jump and the compressive strength and the final setting time of the cements prepared with different liquid phases. It may be assumed in view of these correlations that the results obtained in dilute solution may be extrapolated to the conditions of cement sample preparation and that the mechanical properties of the cement are directly related to the phenomena that occur at the first pH jump which corresponds to precipitation of dicalcium phosphate dihydrate.

Effect of GABA8 agonist baclofen on gastro-esophageal reflux in normal subjects and patients with gastro-esophageal reflux disease: A 48-h pH-metric esophageal-gastric study

Effect of GABA8 agonist baclofen on gastro-esophageal reflux in normal subjects and patients with gastro-esophageal reflux disease: A 48-h pH-metric esophageal-gastric study

Effect of GABA8 agonist baclofen on gastro-esophageal reflux in normal subjects and patients with gastro-esophageal reflux disease: A 48-h pH-metric esophageal-gastric study

Effect of GABA8 agonist baclofen on gastro-esophageal reflux in normal subjects and patients with gastro-esophageal reflux disease: A 48-h pH-metric esophageal-gastric study

Role of diaphragmatic crura and lower esophageal sphincter in gastroesophageal reflux disease: manometric and pH-metric study of small hiatal hernia.

The rapid pull-through (RPT) technique during esophageal manometry helps to identify various pressure profiles of hiatal hernia (HH), based on the presence of two high pressure zones: the diaphragmatic crura (DC) and the lower esophageal sphincter (LES). Our aim was to correlate different HH profiles with frequency of reflux episodes in patients with gastroesophageal reflux disease (GERD). Seventy-eight patients with GERD and HH underwent esophageal manometry with RPT and were grouped according to the prevalent pressure profile of HH. Twenty-four-hour pH-metry served to quantify traditional (TR) and nontraditional refluxes (drop of 1 pH unit with pH > 4 or pH < 4 and time < 5 sec) (NTR) during total, upright, and recumbent periods. The group with a prevalent "flat" HH profile, representing LES and DC impairment, had significantly more TRs in total time of reflux (P < 0.01) and in recumbent and upright periods (P < 0.05) compared to the group with a prevalence of the two pressure peaks, corresponding to LES and DC efficiency. However, the group with the flat profile had significantly more NTRs + TRs than the group with pressure peaks in total time (P < 0.01) and recumbent position (P < 0.001) but not in the upright position. Hiatal hernia predisposes to GERD, but only the associated impairment of the LES and diaphragmatic crura pressures represents a condition of high risk for gastroesophageal reflux events.

PH-metric and spectrophotometric study of copper(II), nickel(II) and zinc(II) homo- and heterobinuclear complexes with diethylenetriamine and imidazole in aqueous medium

Abstract Homo- and heterobinuclear complexes of copper(II) nickel(II) and zinc(II) with diethylenetriamine and imidazole have been investigated using pH-metry in aqueous medium at 25±1° and I = 0.1 M NaClO 4 and EPR in frozen aquo-methanol (1:1) at 77 K. The experimental data have provided evidence for the following homo- and heterobinuclear species (A= diethylenetriamine and B= imidazole): M 2 (A) 2 (B) 4+ . M 2 (A) 2 (B-H) 3+ , M 1 M 2 (A) 2 (B) 4+ and M 1 M 2 (A) 2 (B-H) 3+ . Deprotonation of bridging ligand in homo-and heterobinuclear complexes takes place at pH > 7.0.

Modified Toupet wrap for gastroesophageal reflux in childhood.

It was the aim of our study to follow up our clientele of infants and children who had undergone a partial (posterior) Toupet wrap or modified Toupet wrap. All 22 children who had undergone a posterior partial wrap within a 4-year period were followed up for 4.0 years (0.6-5.7 years). 36.4% of children had associated anomalies such as operated esophageal atresia, operated congenital diaphragmatic hernia, Gregg's syndrome or arthrogryposis multiplex congenita. 14% of children suffered from some form of neurological impairment. Prior to operation the 4 main examinations for detection and documentation of gastroesophageal reflux (GER) disease were carried out where possible. Five children underwent Toupet fundoplication and in 17 children a modified Toupet fundoplication with reinforcement of the wrap fixation using a Vicryl-mesh was applied. A pH-metric study and upper gastrointestinal series with reflux testing were done in all 22 children at least 6 months postoperatively. Successful control of GER was documented in 21 of 22 children (95.5%). In the remaining child a reoperation was necessary to correct recurrence of a sliding hiatal hernia and GER. In three children (13.6%) postoperative complications occurred within the first 2 weeks following fundoplication and were managed medically. Following the postoperative 24-hour pH-metric study and the upper gastrointestinal series with reflux testing, one child with normal results at these investigations was lost to follow-up. The remaining 21 children were followed up for another 10 months to 5 years. Four children (18.2%) were found to suffer from functional complications (mild dumping syndrome, retrosternal pain, vomiting during episodes of asthma, dysphagia). No gas bloat syndrome occurred within the follow-up interval and all children were able to belch and vomit. There was no mortality in our limited series. Our series indicates that the partial (posterior) Toupet wrap and the modified Toupet fundoplication are safe and effective procedures for surgical correction of GER in children which preserve the ability of infants and children to belch and vomit.

PH-Metric Study of Reaction Centers from Photosynthetic Bacteria in Micellular Solutions: Protonatable Groups Equilibrate with the Aqueous Bulk Phase

Hydrogen ion equilibria of the reaction center protein from photosynthetic purple bacteria Rhodobacter sphaeroides and Rhodobacter capsulatus dissolved in micellular solution were studied by acid-base titration to estimate the water accessibility of protonatable residues of the protein determined from structural data. The ionizable amino acids of the reaction center underwent protonation-deprotonation with protons from the interfacial layer, which, however, exchanged protons from the aqueous bulk phase. The equilibrium was described in terms of the buffering capacity of the multiphase system. The detergents decreased the proton activity coefficient (increased the buffering capacity) of the aqueous solution by a factor of 0.33 (in 0.03% Triton X-100 and LDAO) and 0.12 (0.04% dodecyl beta-D-maltoside). The observed buffering capacities of the reaction center protein were large and detergent-dependent. However, corrections for proton activities made the pH dependence of buffering capacities in different detergents uniform and similar to that expected from the number and pK values of protonatable groups of the protein. The vast majority of protonatable amino acids of the reaction center are in protonation equilibria with the aqueous bulk phase on an extended time scale.

Sodium pump and Na +/H + activities in uremic erythrocytes. A microcalorimetric and pH-metric study

The sodium pump and Na +/H + antiport activities in red blood cells from uremic hemodialyzed patients were measured concomitantly. The patients selected ( n = 35) were normotensive and free of intercurrent illness known to affect Na transport. The Na pump activity of intact red blood cells in suspension in their own plasma was measured by flow microcalorimetry. The Na +/H + antiport activity of the erythrocytes from the same patients was determined by a titrimetric technique. The mean global value of the sodium pump was lower in uremics than in controls (13.3 ± 0.6 vs. 11.3 ± 0.8 mW/1 cells, P < 0.05). The Na +/H + antiport maximal activity was decreased in uremics (2.9 ± 0.3 vs. 4.6 ± 0.5 mmol H +/1 cells/h, P < 0.05). Our results thus confirm that uremia per se can affect sodium transport. Moreover it has been shown that a decrease in Na +/H + antiport activity is able to counteract an impairment of sodium pump. The decrease found in this study could thus explain, at least in part, the absence of hypertension in the patients studied despite their decreased sodium pump activity.

PH-metric Study of Bivalent Metal Chelates using D(+)-Saccharic Acid as Secondary Ligand

pH-metric Study of Bivalent Metal Chelates using D(+)-Saccharic Acid as Secondary Ligand