scholarly journals Determination of low chlorine content in organic compounds and polymers using an «Expert-006» coulometer

2018 ◽  
Vol 84 (7) ◽  
pp. 16-20
Author(s):  
D. Kh. Kitaeva ◽  
A. G. Buyanovskaya ◽  
O. A. Levinskaya ◽  
S. L. Dzvonkovski
Keyword(s):  
Coulometric Titration ◽  
Silver Ions ◽  
Electrolytic Cell ◽  
Chloride Ions ◽  
Chlorine Content ◽  
Residual Chlorine ◽  
Coulometric Determination ◽  
Electrochemical Parameters ◽  
Organic Matrices

A method of visual mercurimetric titration of chloride ions is widely used in elemental microanalysis for determination of chlorine content in organic substances after their combustion in an oxygen-filled flask. However, when chlorine content is less than 0.5%, the mercurimetric method fails to provide essential accuracy, and a more sensitive method of chlorine coulometric titration by electrogenerated silver ions appeared favorable. We consider a possibility of determining the microgram content of chloride-ions in solutions using a digital coulometric analyzer («Expert-006» produced by «Econics-Expert» (Moscow)) supplemented with an electrolytic cell with silver electrodes. The coulometer was tested in different operation modes to select the optimal electrochemical parameters of ion chloride titration and develop a technique for coulometric determination of chloride ions which in combination with the preliminary burning of the analyzed substances in an oxygen-filled flask provides determination of the residual chlorine in organic matrices at a level of 0.1 – 0.5%. The proposed technique was used to determine the residual chlorine in a number of polymers. The relative error did not exceed 5% at chlorine concentrations of 0.16 – 0.28%.

scholarly journals Determination of phenolic compounds in medicinal preparations by galvanostatic coulometry

2021 ◽  
Vol 8 (1) ◽  
pp. 20218110
Author(s):  
N. N. Yaschenko ◽  
S. V. Zhitar ◽  
E. G. Zinovjeva
Keyword(s):  
Phenolic Compounds ◽  
Coulometric Titration ◽  
Experimental Studies ◽  
Coulometric Determination ◽  
Correct Definition ◽  
Galvanostatic Coulometry ◽  
Coulometric Method ◽  
Preliminary Separation ◽  
Ascorbic Acids

In this work, the possibility of using reactions of electrogenerated titrants with phenolic compounds was studied and a method for their coulometric determination in medicaments by galvanostatic coulometry was developed. The research objects were: rutin, salicylic acid and drugs containing phenolic compounds such as «Ascorutin», «Salicylic Paste» and «Salicylic Ointment» of Russian manufacture. Electrogenerated halogens (Cl2, Br2 and I2) and hexacyanoferrate(III)-ions were used as titrants. It was found that for the quantitative determination of phenolic acids, the optimal reagent is electrogenerated bromine, for rutin - electrogenerated bromine and iodine, and for ascorbic acid - any of the studied electrogenerated titrants (Cl2, Br2, I2 and [Fe(CN)6]3-). The correct definition was checked by the «entered-found» method, the error does not exceed 2%. As experimental studies have shown, our method of coulometric titration with electrogenated bromine and iodine is characterized by good reproducibility of results, expression, accuracy and can be used to determine phenolic compounds in drugs, for example, «Ascorutin» tablets. It should be noted that by our procedure it is possible to determine the spectrum of phenol-containing compounds (rutin, ascorbic and salicylic acids) in drugs without their preliminary separation. Therefore, the coulometric method using electrogenerated titrants can be recommended for the determination of salicylic, ascorbic acids and rutin in dosage forms. The proposed method is accurate and eliminates the experiment error in comparison with the Pharmacopoeic method.

The Coulometric Determination of Glucose in Human Serum

1968 ◽  
Vol 14 (5) ◽  
pp. 463-476 ◽  
Author(s):  
Robert K Simon ◽  
Gary D Christian ◽  
William C Purdy
Keyword(s):  
Human Serum ◽  
Glucose Oxidase ◽  
Coulometric Titration ◽  
Aerobic Oxidation ◽  
Enzymatic Reaction ◽  
Complete Recovery ◽  
Serum Levels ◽  
Normal Serum ◽  
Coulometric Determination

Abstract The coulometric titration method is combined with the use of an enzymatic analytic reagent for the determination of glucose in human serum. The glucose in 25 µl. of serum is determined in a protein-free filtrate (PFF) with an accuracy of ± 3% and a coefficient of variation of approximately 2%. The procedure routinely covers a concentration range of 25-250 mg/100 ml. Calibrations are linear to at least 450 mg./100 ml. with zero intercept. Glucose oxidase specifically catalyzes the aerobic oxidation of glucose to hydrogen peroxide. The peroxide reacts with iodide, in the presence of molybdenum (VI) catalyst, to form iodine. A known excess of thiosulfate reduces the iodine as it is produced. The reagents and the sample are incubated at 25.0° and pH 5.1. After 15 min., the pH is adjusted to 8.0 with phosphate reagent to stop the enzymatic reaction. The residual thiosulfate is titrated coulometrically with iodine at pH 8.0 to a dead-stop end point at a generating current of 0.4825 ma. The difference between the sample and thiosulfate reagent titers is proportional to the glucose concentration. The method is empirical. Peroxide-reducing impurities in the glucose oxidase preparation and mutarotation equilibrium prevent the complete recovery of glucose under the conditions of the experiment. Calibrations are reproducible from day to day and week to week. Reagents and the PFF constitute a negligible titration blank. Only 1 calculation is necessary. A simplified apparatus and procedure for the preparation of PFF’s permits 15 manual determinations per hour. Coulometric assays of commercial serum controls are accurate to within 3-4%. Data indicate that the precision of the coulometric method exceeds that of the Auto-Analyzer, Folin-Wu, Glucostat, and Nelson-Somogyi procedures. The proposed method is free from interferences at normal serum levels.

Selectivity coefficients of some simple and complex inorganic ions for Spheron DEAE

1984 ◽  
Vol 49 (10) ◽  
pp. 2349-2354 ◽  
Author(s):  
František Vláčil ◽  
Karel Koňák
Keyword(s):  
Ion Exchange ◽  
Mobile Phase ◽  
Dynamic Method ◽  
Precious Metals ◽  
Inorganic Ions ◽  
Chromatographic Determination ◽  
Chloride Ions ◽  
Chloro Complexes ◽  
Selectivity Coefficients

The selectivity coefficients of the nitrate and chloride ions and of anionic chloro complexes of Au(III), Rh(III), Pd(II), and Pt(IV) for ion exchange on Spheron DEAE in the chloride form are determined by the dynamic method. the complex anion species formed are identified and the ion exchange nature of the sorption of precious metals on this sorbent is confirmed based on the elution order of the precious metals as determined previously by the column chromatography on Spheron DEAE using hydrochloric acid as the mobile phase. The effect of the presence of perchlorate in the mobile phase during the liquid chromatography of precious metals and during the chromatographic determination of nitrate traces is explained.

Decomposition of hydrogen peroxide on nickel-silver two-component catalyst

1984 ◽  
Vol 49 (10) ◽  
pp. 2222-2230 ◽  
Author(s):  
Viliam Múčka ◽  
Rostislav Silber
Keyword(s):  
Hydrogen Peroxide ◽  
Chemical Properties ◽  
Silver Ions ◽  
Surface Concentration ◽  
Chloride Ions ◽  
Nickel Silver ◽  
Silver Catalysts ◽  
Physico Chemical ◽  
Low Degree ◽  
Defective Crystal

The catalytic and physico-chemical properties of low-temperature nickel-silver catalysts with nickel oxide concentrations up to 43.8% (m/m) are examined via decomposition of hydrogen peroxide in aqueous solution. The mixed catalysts prepared at 250°C are composed of partly decomposed silver carbonate or oxide and nickel carbonate or hydroxide decomposed to a low degree only and exhibiting a very defective crystal structure. The activity of these catalysts is determined by the surface concentration of silver ions, which is affected by the nickel component present. The latter also contributes to the thermal stability of the catalytic centres of the silver component, viz. the Ag+ ions. The concentration of these ions varies with the temperature of the catalyst treatment, the activity varies qualitatively in the same manner, and the system approaches the Ag-NiO composition. The catalytic centres are very susceptible to poisoning by chloride ions. A previous exposition of the catalyst to a gamma dose of 10 kGy from a 60Co source has no measurable effect on the physico-chemical properties of the system.

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

Multi-Array Wax Paper-Based Platform for the Pre-Concentration and Determination of Silver Ions in Drinking Water

Talanta ◽  
2021 ◽  
pp. 122474
Author(s):  
Neda Bagheri ◽  
Stefano Cinti ◽  
Eleonora Nobile ◽  
Danila Moscone ◽  
Fabiana Arduini
Keyword(s):  
Drinking Water ◽  
Silver Ions

scholarly journals Managing pH of Organic Matrices and New Commercial Substrates for Ornamental Plant Production: A Methodological Approach

Agronomy ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 851
Author(s):  
Sonia Cacini ◽  
Sara Di Lonardo ◽  
Simone Orsenigo ◽  
Daniele Massa
Keyword(s):  
Methodological Approach ◽  
Buffering Capacity ◽  
Ornamental Plant ◽  
Plant Production ◽  
Climatic Chamber ◽  
Step Procedure ◽  
Coir Dust ◽  
Organic Matrices ◽  
Substrate Mixtures

Professional peat-free substrates for ornamental plant production are increasingly required by nursery growers. Most promising materials are green compost, coconut coir dust, and woody fibre, used alone or in mixtures. One of the major concerns is pH, usually higher than optimal. In this work, a method based on a three-step procedure was adopted to acidify three organic matrices alone or in mixtures and to individuate the most suitable product, between iron(II) sulphate 7-hydrate and elemental sulphur chips. Firstly, the determination of the buffering capacity by dilution with sulphuric acid was carried out to determine dosages. Afterwards, an incubation trial of 84 (iron(II) sulphate) or 120 days (sulphur chips) was conducted on matrices and substrate mixtures with calculated doses in a climatic chamber maintained at 21 °C. Iron(II) sulphate resulted not suitable because it caused a rapid, but not lasting, pH lowering and an excessive electrical conductivity (EC) increase. Sulphur chips could instead guarantee an adequate and lasting pH lowering. These results were then validated in the open field trial on matrices and substrates. The proposed acidification methodology could be considered in developing new substrates, but the rapidity of pH acidification and EC increase on plant and mineral nutrition should be further investigated.

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