scholarly journals Determination of relative acidity scales for some dipolar aprotic solvents by coulometry using a hydrogen-palladium electrode

2008 ◽  
Vol 73 (8-9) ◽  
pp. 871-878 ◽  
Author(s):  
Radmila Dzudovic ◽  
Ljiljana Jaksic
Keyword(s):  
Perchloric Acid ◽  
Supporting Electrolyte ◽  
Sodium Perchlorate ◽  
Electrode Pair ◽  
Tetrabutylammonium Perchlorate ◽  
Palladium Electrode ◽  
The Difference ◽  
Acidity Scale ◽  
Relative Acidity

A coulometric-potentiometric procedure for the determination of relative acidity scales of acetone, methylethyl ketone, methyl-isobutyl ketone and propylene carbonate is described. The range of the relative acidity scale of a solvent was determined from the difference between the half-neutralization potential of perchloric acid and that of tetrabutylammonium hydroxide. The perchloric acid was generated in situ from a hydrogen-palladium electrode in presence of sodium perchlorate or tetrabutylammonium perchlorate as the supporting electrolyte. The electrode pairs glass-SCE and (H2/Pd)ind-SCE were applied for the measurement of the half-neutralization potentials of the acid and base. A wider range of relative acidity scale of the solvents was obtained with the glass-SCE electrode pair and tetrabutylammonium perchlorate as the supporting electrolyte.

scholarly journals Coulometric-potentiometric determination of autoprotolysis constant and relative acidity scale of water

2010 ◽  
Vol 75 (11) ◽  
pp. 1575-1582 ◽  
Author(s):  
Radmila Dzudovic ◽  
Ljiljana Jaksic
Keyword(s):  
Supporting Electrolyte ◽  
Sodium Perchlorate ◽  
Electrolytic Cell ◽  
Electrode Pair ◽  
Strong Base ◽  
Palladium Electrode ◽  
Oxidation Of Hydrogen ◽  
The Difference ◽  
Acidity Scale ◽  
Relative Acidity

The autoprotolysis constant and relative acidity scale of water were determined by applying the coulometric-potentiometric method and a hydrogen/palladium (H2/Pd) generator anode. In the described procedure for the evaluation of autoprotolysis constant, a strong base generated coulometrically at the platinum cathode in situ in the electrolytic cell, in presence of sodium perchlorate as the supporting electrolyte, is titrated with hydrogen ions obtained by the anodic oxidation of hydrogen dissolved in palladium electrode. The titration was carried out with a glass-SCE electrode pair at 25.0?0.1?C. The value obtained pKw = 13.91 ? 0.06 is in agreement with literature data. The range of acidity scale of water is determined from the difference between the halfneutralization potentials of electrogenerated perchloric acid and that of sodium hydroxide in a sodium perchlorate medium. The halfneutralization potentials were measured using both a glass-SCE and a (H2/Pd)ind-SCE electrode pairs. A wider range of relative acidity scale of water was obtained with the glass-SCE electrode pair.

scholarly journals The application of hydrogen-palladium electrode for potentiometric acid-base determinations in tetrahydrofuran

2013 ◽  
Vol 78 (8) ◽  
pp. 1203-1212
Author(s):  
Anja Jokic ◽  
Radmila Dzudovic ◽  
Ljiljana Jaksic ◽  
Snezana Nikolic-Mandic
Keyword(s):  
Maleic Acid ◽  
Glass Electrode ◽  
Indicator Electrode ◽  
Electrode Pair ◽  
Acid Base ◽  
Palladium Electrode ◽  
The Individual ◽  
Acidity Scale ◽  
Relative Acidity

The application of the hydrogen-palladium electrode (H2/Pd) as the indicator electrode for the determination of relative acidity scale (Es, mV) of tetrahydrofuran (THF) and the potentiometric titrations of acids in this solvent was investigated. The relative acidity scale tetrahydrofuran was determined from the difference half-neutralization potentials of perchloric acid and tetrabutylammonium hydroxide (TBAH), which were measured by using both H2/Pd-SCE and glass-SCE electrode pairs. The experimentally obtained value of Es scale THF with a H2/Pd-SCE electrode pair was 1155 mV, and those obtained with glass-SCE electrode pair 880 mV. By using a H2/Pd indicator electrode, the individual acids (benzoic acid, palmitic acid, maleic acid, acetyl acetone, ?-naphthol) and two component acid mixtures (benzoic acid + ?-naphthol, palmitic acid + ?-naphthol, maleic acid + ?-naphthol and maleic acid + ftalic acid) were titrated with a standard solution of TBAH. In addition, sodium methylate and potassium hydroxide proved to be very suitable titrating agents for titrating of the individual acids and the acids in mixtures, respectively. The relative error of the determination of acids in mixture was less than 3%. The results are in agreement with those obtained by a conventional glass electrode. The advantages of H2/Pd electrode over a glass electrode in potentiometric acid-base determinations in tetrahydrofuran lie in the following: this electrode gives wider relative acidity scale THF, higher the potential jumps at the titration end-point and relatively fast response time; furthermore, it is very durable, simple to prepare and can be used in the titrations of small volumes.

scholarly journals Coulometric-potentiometric determination of pKA of several organic bases in propylene carbonate

2008 ◽  
Vol 73 (6) ◽  
pp. 655-659
Author(s):  
Ljiljana Jaksic ◽  
Radmila Dzudovic
Keyword(s):  
Propylene Carbonate ◽  
Supporting Electrolyte ◽  
Sodium Perchlorate ◽  
Potentiometric Method ◽  
Potentiometric Determination ◽  
Pka Values ◽  
Reference Base ◽  
Organic Bases ◽  
Standard Base

The pKA values of protonated triethylamine, pyridine and 2,2'-dipyridyl in propylene carbonate (PC) were determined by applying the coulometric-potentiometric method and a hydrogen/palladium generator anode (H2/Pd). The investigated and reference base were titrated to 50 % with protons electro-generated from hydrogen-saturated palladium, in the presence of sodium perchlorate as the supporting electrolyte. The half-neutralization potentials E1/2(x) and E1/2(st.) of the investigated and standard base, respectively, were measured using a glass-SCE pair. The obtained pKA values were compared with those reported in the literature.

A Micromethod for Rapid Quantitative Determination of Phosphonate Phosphorus

1984 ◽  
Vol 39 (3-4) ◽  
pp. 249-251 ◽  
Author(s):  
Vassilios M. Kapoulas ◽  
Sofia K. Mastronicolis ◽  
Ibrahim C. Nakhel ◽  
Helen J. Stavrakakis
Keyword(s):  
Sulfuric Acid ◽  
Quantitative Determination ◽  
Rapid Method ◽  
Total Phosphorus ◽  
Perchloric Acid ◽  
Quantitative Estimation ◽  
The Other ◽  
The Difference

A rapid method for initial quantitative estimation of the phosphate present in compound containing a carbon-phosphorus bond is described. Two phosphorus assays are employed. One assay is for total phosphorus, which can be determined by digesting with perchloric acid and the other assay is for total non phosphonate phosphorus which can be determined by digesting with sulfuric acid simultaneously. The difference between total phosphorus and the non phosphonate phosphorus determined represents the amount of phosphorus present in a carbon-phosphorus linkage in a crude phospholipids sample

scholarly journals Differences in Nucleotide Hydrolysis Contribute to the Differences between Erythrocyte 6-Thioguanine Nucleotide Concentrations Determined by Two Widely Used Methods

2003 ◽  
Vol 49 (2) ◽  
pp. 260-268 ◽  
Author(s):  
Maria Shipkova ◽  
Victor William Armstrong ◽  
Eberhard Wieland ◽  
Michael Oellerich
Keyword(s):  
Sulfuric Acid ◽  
Perchloric Acid ◽  
Hydrolysis Time ◽  
Nucleotide Hydrolysis ◽  
Azathioprine Therapy ◽  
Thiopurine Therapy ◽  
Background Measurement ◽  
Thioguanine Nucleotide ◽  
The Difference

Abstract Background: Measurement of 6-thioguanine nucleotide (6-TGN) concentrations in erythrocytes is widely accepted for use in optimization of thiopurine therapy. Various chromatographic methods have been developed for this purpose. In preliminary experiments we observed a considerable difference between 6-TGN concentrations determined with two widely used methods published by Lennard (Lennard L. J Chromatogr 1987;423:169–78) and by Dervieux and Boulieu (Dervieux T, Boulieu R. Clin Chem 1998;44:551–5). We therefore investigated methodologic differences between the two procedures with respect to hydrolysis of 6-TGNs to 6-thioguanine (6-TG) in more detail. Methods: We analyzed 6-TGNs in erythrocyte preparations (n = 50) from patients on azathioprine therapy by both methods, using the original protocols. In one set of experiments, we replaced the 0.5 mol/L sulfuric acid in the Lennard method with the 1 mol/L perchloric acid used by Dervieux and Boulieu. In a second set of experiments, we investigated the effect of various dithiothreitol (DTT) concentrations on 6-TG recovery with both methods. In a third set of experiments, we determined the effect of hydrolysis time on both protocols. Results: Direct comparison of both methods showed that 6-TGN concentrations were, on average, 2.6-fold higher in the Dervieux–Boulieu method over the concentration range tested, although the correlation (r = 0.99; P <0.001) was good. Replacement of sulfuric acid by perchloric acid reduced this difference to ∼1.4-fold (r = 0.99; P <0.001). Increasing the DTT concentration enhanced 6-TG recovery. The hydrolysis time used in the Lennard method (1 h) was not sufficient to achieve complete hydrolysis. Conclusions: The difference between 6-TGN concentrations measured by the two methods is attributable, at least in part, to differences in the extent of nucleotide hydrolysis. For optimization of thiopurine therapy, method-dependent therapeutic ranges are necessary, which precludes comparison of results from clinical studies derived with these methods. Efforts must therefore be made to standardize the analytical procedures for the determination of 6-TGN.

scholarly journals Voltammetric Determination of Isopropylmethylphenols in Herbal Spices

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6095
Author(s):  
Magdalena Jakubczyk ◽  
Slawomir Michalkiewicz ◽  
Agata Skorupa ◽  
Daria Slefarska
Keyword(s):  
Electrode Materials ◽  
Supporting Electrolyte ◽  
Sodium Perchlorate ◽  
Total Content ◽  
Standard Addition ◽  
Differential Pulse ◽  
Voltammetric Determination ◽  
Pulse Voltammetry ◽  
Good Agreement

Thymol and carvacrol—the components of herbal spices—are known for their broad biological activity as antimicrobials and antioxidants. For this reason, it is important to develop new methods for their determination in plant material. A simple, rapid, and sensitive method for determination of total content of these analytes in herbal spices using differential pulse voltammetry (DPV) has been developed. The basis of the research is the oxidation process of isopropylmethylphenols on a platinum microelectrode in glacial acetic acid containing acetonitrile (20%, v/v) and 0.1 mol L−1 sodium perchlorate as the supporting electrolyte. Linear voltammetric responses for thymol and carvacrol were obtained in a wide concentration range from 0.39–1105 and 0.47–640 µg mL−1, with a low detection limit of 0.04 and 0.05 µg mL−1, respectively. The analysis was performed using the multiple standard addition method. The results of the voltammetric determination are in good agreement with the data of the standard chromatographic method. To the best of our knowledge, this is the first presentation of an electrochemical procedure to determine these compounds in these environmental and electrode materials.

Electrochemical and spectroelectrochemical studies of β-phosphorylated Zn porphyrins

2013 ◽  
Vol 17 (10) ◽  
pp. 1035-1045 ◽  
Author(s):  
Yuanyuan Fang ◽  
Karl M. Kadish ◽  
Ping Chen ◽  
Yulia Gorbunova ◽  
Yulia Enakieva ◽  
...  
Keyword(s):  
Radical Cation ◽  
Chemical Reaction ◽  
Supporting Electrolyte ◽  
Redox Processes ◽  
Tetrabutylammonium Perchlorate ◽  
Dimer Formation ◽  
The Difference ◽  
Porphyrin Dimers ◽  
Spectroelectrochemical Properties

The electrochemical and spectroelectrochemical properties of two β-phosphorylated Zn porphyrins, [2-diethoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (1) and [2-diisopropoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (2), are reported in CH 2 Cl 2 and PhCN containing tetrabutylammonium perchlorate (TBAP) or tetrabutylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. Under certain solution conditions, three one-electron reductions are observed, with the last process being attributed to the product of a chemical reaction following formation of the porphyrin dianion. Two or three oxidations are observed for the same compounds, again depending upon the solution conditions. In some cases, two well-defined and well-separated one electron oxidations are observed but in others the first one-electron abstraction to give the porphyrin radical cation is split into two redox processes, separated from each other by 110–140 mV. This splitting of the first oxidation into two processes is attributed to linking of the two porphyrins which results when a P = O unit of the phosphoryl substituent on one porphyrin binds to the Zn ( II ) center of a second porphyrin, resulting in dimer formation. The interaction between the two macrocycles is discussed in terms of the difference in potentials between the two split redox processes (ΔE1/2) and the overall data is compared with that for other porphyrin dimers and bis-macrocycles reported in the literature.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

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