DETERMINATION OF THE STABILITY OF COMPLEX COMPOUNDS OF COPPER (II), ZINC (II), CADMIUM (II) AND SILVER (I) WITH COVALENTLY IMMOBILIZED SULFUR CONTAIN LIGANDS

"The purpose of this study is to determine the stability of the obtained coordination compounds of some d-metals with covalent immobilized sulfur-containing ligands. To achieve this goal, coordination compounds of copper (II), zinc (II), cadmium (II) and silver (I) ions with covalent immobilized sulfur-containing ligands - О,О-di- (2-aminoethyl) -dithiophosphate potassium - polyester matrix (KD2AEDTP-PEM), O,O-di- (2-aminoethyl) -dithiophosphate potassium - carbamide-formaldehyde matrix (KD2AEDTP-KFM). Studies were carried out to determine the acid-base properties of covalent-immobilized sulfur-containing ligands - KD2AEDTP-PEM, KD2AEDTP-KFM and the concentration stability of the obtained coordination compounds with ions of copper (II), zinc (II), cadmium (II), and silver (I). Based on the results of integral and differential potentiometric titrations, it was established that the ionization constants (pK) of the dithiophosphoric group in KD2AEDTP-PEM and KD2AEDTP-KFM are 3.23 and 3.35, and the ionization constants of the amino group are 9.76 and 9.63, respectively. As a result of studies of polymer ligands by potentiometric titration via the method of individual weighed portions, it was shown that polyfunctional polymer ligands have the ability to form stable coordination compounds with metal ions of copper (II), zinc (II), cadmium (II) and silver (I). "

Preparation, analytical Studies and application of a New Azodye Derived from Pharmaceutical Materials (Procaine Hydrochloride & Salicylic acid)

Procaine hydrochloride was used as an aromatic amine, and salicylic acid (5-[2-(diethylamino)-4-benzoateazo]-2-hydroxybenzoic acid) was used to make a new azodye derived from pharmaceutical materials ( PS ).C.H.N., H1-NMR, I.R., and visible spectroscopic techniques have also been used to characterize dye. At different pH values ( 2 - 12 ), the electronic spectra of this azo dye was investigated in terms of acid-base properties, which included defining isobestic points and determining protonation and ionization constants. The effect of different polarities of solvents on the electronic spectra was the subject of another study. The dye has been used in a variety of applications, including as an indicator for strong acid with strong base and for nitrite determination.

Ionic Equilibria and pH

Ionic Equilibria and pH reviews the quantitative aspects of aqueous acid-base chemistry. Definitions and concepts are presented and appropriate worked examples illustrate calculations of concentration, pH and ionization constants. Acid-base properties of salts (salt hydrolysis) is introduced and explained along with the common-ion effect and calculation of hydrolysis constants. Equilibria of acid-base buffers with respect to buffer preparation, calculating the pH of a buffer solution and application of the Henderson-Hasselbalch equation, buffer range and buffer capacity is discussed. Determining the pH during acid-base titrations, selecting the appropriate acid-base indicators, and generating pH titration curves are explained.

Physicochemical Properties and Solubility of Hydrochloride Mucolytic Agents

Two widely used active pharmaceutical ingredients (API), ambroxol hydrochloride (AMB·HCl) and bromhexine hydrochloride (BMH·HCl), belong to the expectorant and mucokinetic group of drugs. Their applications are found in the treatment of the upper respiratory tract and bronchopulmonary diseases. The compounds have similar chemical structures, but are different enough to distinguish their physicochemical properties. To understand better the bioavailability of the drugs a series of experiments was performed to establish significant parameters. With differential scanning calorimetry (DSC) the temperature and the enthalpy of fusion were determined with no observed polymorphic transformations. The phase diagrams for binary systems {active agent (1) + solvent (2)} were determined with three solvents: 1-octanol, water and ethanol, to describe phase equilibria by correlation with the local composition models: Wilson, UNIQUAC and NRTL. Finally, the Bates–Schwarzenbach method was used to establish the ionization constants of AMB·HCl and BMH·HCl at two temperatures: room temperature 298.2 K and human body temperature 310.2 K. Our study can give an insight into further drug delivery system design and help to create more effective drug application forms.

Protolytic Equilibria in Organized Solutions: Ionization and Tautomerism of Fluorescein Dyes and Related Indicators in Cetyltrimethylammonium Chloride Micellar Solutions at High Ionic Strength of the Bulk Phase

Ionic equilibrium of 22 hydroxyxanthenes, including halogen and nitro derivatives of fluorescein, and their thio- and aza analogues, were studied spectrophotometrically in micellar solutions of cetyltrimethylammonium chloride at ionic strength of the bulk phase 4.0 M KCl. This micellar pseudophase is characterized by the electrostatic surface potential of +(15–16) mV and the ETN value of 0.623. In the case of dyes bearing the COOH group, colorless lactone is the predominant tautomer of the molecular form H2R. A new classification of fluoresceins is developed. The dyes were divided into four groups based on the nature of tautomerism of the anions. In the case of the fluorescein type, the monoanions HR− exist predominantly as “carboxylate” tautomers, with ionized carboxylic and non–ionized hydroxylic group. For the dyes of the eosin type, the situation is opposite, while for the intervening type of compounds, the concentrations of the two tautomers are comparable. Dyes capable of forming lactone anions HR− were classified as the fourth type. For some of them, even the dianion R2− exists as a lactone. The relationship between the stepwise ionization constants, Ka1/Ka2, varies from 1.3 to 1.07 × 105 and is determined by the state of tautomeric equilibrium of molecules and ions.

Third dissociation constant of phosphoric acid in H2O and D2O from 75 to 300 °C at p = 20.4 MPa using Raman spectroscopy and a titanium-sapphire flow cell

The first reported Raman spectra and ionization constants for the phosphate ion in H2O and D2O above 50 °C quantify deuterium isotope effects under hydrothermal conditions.

Development and validation of methods of quantitative determination of biologically active compound n-(2-[4-oxo-3(4h)-quinazolinyl]propionyl)guanidine

This paper presents the results of the selection and justification of the conditions for determination of a new biologically active compound (BAC) VMA-13-15, which is N-(2-[4-oxo-3(4H)-quinazolinyl]propionyl)guanidine bymeans of the spectrophotometry. By using the calculated values of BAC ionization constants, it was proposed to use purified water as a solvent. The maximum light absorption at 266 nm was chosen as the analytical wavelength. This was justified by the fact that in aqueous solutions 99% BAC are in the molecular form, which allows to determine it with the error limit of 1.29%, and with the least amount of dilutions. The study showed that the proposed method is specific and linear in the analytical concentration of 0.0010.004%, as well as it is precise and correct, which confirms the possibility of its use for quantitative determination.