Loss Of Crystal Water Research Articles

КУЛОНОМЕТРИЧЕСКОЕ ОПРЕДЕЛЕНИЕ ВОДЫ В ФАРМАЦЕВТИЧЕСКИХ СУБСТАНЦИЯХ

The water content is one of the mandatory criteria for the quality of pharmaceutical substances. Violation of the technological process for the manufacture of substances or their storage conditions can lead to undesirable outcomes: loss of crystallization water or dampness, which can cause processes such as hydrolysis, oxidation, decomposition, the formation of undesirable impurities that can have a toxic effect. The regulatory documentation regulates either only the upper limit of the water content, or the upper and lower limits (for substances containing water of crystallization in their structure), depending on the properties of the pharmaceutical substance. Coulometric Fischer titration is a promising method for the determination of water. The titrant is electrogenerated iodine, which is formed during the anodic oxidation of iodide ions contained in the anode solution. Further, iodine oxidizes sulfur (IV) in the presence of water according to the Fisher reaction and is reduced to iodide ions, from which iodine can be generated again. Measuring the current and time duration for electrolysis, on which the amount of iodine electrogenerated at the anode depends, makes it possible to calculate the water content in the pharmaceutical substance. Preliminary removal of moisture from the anolyte and the possibility of water determination only in the injected sample significantly increase the accuracy of the analysis. The advantages of this method are specificity, no need for preliminary standardization of the titrant and creation of calibration graphs, rapidity and simplicity of the experiment, possibility of full automation. A unified method for the determination of water by coulometric Fischer titration in substance of nicotinic acid, bendazole hydrochloride and lizinopril dihydrate has been developed. The relative standard deviation does not exceed 2%, the relative error of the mean is 1.8%. The methods can be used in the practice of analytical laboratories to assess the "Water" parameter in these pharmaceutical substances.

Drugs in ultra-high dilution induce changes in the enthalpy associated with loss of crystallization water in lactose

Drugs in ultra-high dilution (UHD) are used in homeopathy. Lactose is used as a binding medium for UHD drugs. FTIR and Raman spectroscopy revealed that although devoid of molecules of the starting substance, different UHD drugs exhibit different amounts of free water molecules and variation in hydrogen bond strength. The aim of the present study was to establish whether specific water structures in UHD could specifically modify the water structure in lactose, particularly the water of crystallization. 3 UHD’s (potencies), 30cH, 200cH and 1000cH, of 2 drugs, Natrum muriaticum and Sulphur were mixed to lactose samples separately. Differential scanning calorimetry (DSC) of the samples was measured. The thermograms of potencies mixed to lactose differed from each other with respect to temperature and enthalpy associated with the removal of water of crystallization from lactose. We believe that the tested UHD modified the water structure in lactose thereby changing the enthalpy for the removal of water of crystallization. Different levels of thermal energy are needed to remove both free water molecules and water of crystallization from lactose. UHD’s also contributed to the change in enthalpy associated with the removal of water of crystallization from lactose. The tested UHD might have modified the number and strength of hydrogen bonds in the crystal structure of lactose. Specific water structures in liquid aqueous ethanol medium are transferable to the solid medium(lactose).

Hydrates of adenosine 3′,5′-cyclic monophosphate sodium and their transformation

The difference of crystal water behaviors for cAMPNa hydrates was attributed mainly to the steric effects in lattices. Excessive loss of crystal water would destroy the host structure, and result in the disability of reversible transformation.

The solvent effect in obtaining of acid–base multicomponent systems: thermal, structural and luminescence study

Acid–base multicomponent systems based on active pharmaceutical ingredients 2-chloro-5-nitrobenzoic acid (2Cl5NBH) and monoethanolamine were prepared by different reaction pathways. A comparative investigation of crystal structures, thermal stability and photoluminescent properties of studied molecular salts: N-(1,1-dimethyl-3-oxobutyl)monoethanolammonium 2-chloro-5-nitrobenzoate (1) and monoethanolammonium 2-chloro-5-nitrobenzoate (2), obtained in acetone and diethyl ether, was presented. In contrast to our previous results, we find that acetone acts as a reactant in the reaction of 1 forming interaction with the solute, beside diethyl ether which behaves as a solvent in the synthesis of 2. The solid-state structures of 1 and 2 were described and studied by IR spectroscopy and single-crystal X-ray diffraction. Thermogravimetric, derivative thermogravimetric and heat flow methods were used for the characterization of thermal behavior of products. It is shown that both compounds have high thermal stability until 150 °C, excepting the loss of crystallization water in compound 2. The photoluminescence properties of monoethanolammonium salts were compared to free 2Cl5NBH acid in order to examine the role of anion and cation, respectively.

The Effect of Andreasen ́s Packing Distribution Modulus on the Physical and Mechanical Properties of a Low Cement Refractory Castable

Among modern refractory concretes (MRC), those with low cement content (LCC) where CAC = 4-6wt%, are widely commercialized, considering that their properties approximate those of burned bricks of the same class. In this work, the effect of the modulus q of Andreasen ́s particle size distribution, on the physical (porosity, bulk density) and mechanical (flexural strength and dynamic elastic modulus) properties, of either pre-fired or simply dried specimens of a ≥85% Al2O3 LCC ́s, was investigated. The different LCC ́s samples were formulated according to the Andreasen ́s model, using several distribution modulus (q = 0.22, 0.26, 0.30, 0.33 and 0.42). Measurements of the Dynamic Elastic Modulus (DEM) as a function of temperature (25 to 1500°C), using the Impulse Excitation Technique (IET), were taken as a key indicator of the microstructure dynamic behavior. For the sake of just a punctual comparative term, the physical and mechanical properties of a conventional type refractory concrete (CRC) with a higher CAC percentage (15%) formulated with q = 0.26 was also evaluated. The results indicated that distribution modulus values of; q =0.22, 0,26, 0.30 and 0.33 lead to higher DEM values. While q=0.42 lead to the smallest value in the LCC series. Also, higher DEM values ​​were obtained for LCC ́s (CAC = 5%) than for conventional concrete with CAC = 15% under the same value of q for pre-fired samples. In addition, by observing the occurrence of damping effects in specific temperature ranges, the loss of crystallization water from the calcium aluminate hydrates, as well as the development of pyroplastic behavior could be inferred. The gathered information is relevant to predict the behavior of LCC ́s and CRC ́s when put into service for the first time.

Structure and thermal behavior of two bimetallic carboxylates: Cs[M(CCl3COO)3(H2O)3], M = Co, Ni

Bimetallic trichloroacetates of the composition Cs[M(CCl3COO)3(H2O)3], where (I: M = Co, II: Ni) were synthesized. The structures of these compounds have been determined by the single crystal X-ray diffraction. The compounds are isostructural and crystallize in the trigonal system, sp.gr. $$ R\overline{3} $$ . а = b = 10.5770(6), c = 32.8213(2) A, α = β = 90°, γ = 120°, Z = 6, V = 3179.9(4) A3 (for Со compound), а = b = 10.5404(4), c = 32.7116(7) A, α = β = 90°, γ = 120°, Z = 6, V = 3147.4(2) A3 (for Ni compound). The structure contains [M(CCl3COO)3(H2O)3] anions, where (M = Co, Ni). The d-metal atom is located in the distorted octahedral environment of oxygen atoms in the anion. These compounds have nearly the same IR spectra. The thermal stability of the compounds was studied. The thermal behavior of these compounds is similar to each other, but the difference is in the stage of loss of crystallization water—for the nickel compound, this process starts at 20 °C higher than for the cobalt compound. The high-temperature process of the transition of metal chlorides to the gas phase differs: for the cobalt compound, the mass loss begins at 600 °C, whereas for the nickel compound, the mass loss begins at 720 °C. The compounds obtained are the first examples of alkaline metal—transition metal trichloroacetates.

Solid-State Transformations in Inner Coordination Sphere of [Co(NH₃)₆][Fe(C₂O₄)₃]∙3H₂O as a Route to Access Catalytically Active Co-Fe Materials.

Thermal decomposition of [Co(NH3)6][Fe(C2O4)3]∙3H2O in argon atmosphere, at a low heating rate (3°/min), and in large amounts of the initial complex (~0.1 mole), has been studied. It was possible to distinguish four decomposition steps upon heating: In the temperature range of 50–100 °C—the loss of crystal water; 100–190 °C—stability region of dehydrated complex; 230–270 °C—the range of stability of intermediate phase with the formula CoFe(NH3)2(C2O4)2; 270–350 °C—thermal decomposition of the intermediate with the formation of metallic products and further air oxidation with the formation of Co1.5Fe1.5O4. Catalytic properties of thermolysis products were tested in the decomposition reaction of H2O2 (inactive), oxidation of acetone (average activity), and decomposition of ammonium perchlorate (highly active).

Synthesis, Characterization, Thermal and Catalytic Studies of Oxovanadium(IV) Complexes with Tetradentate ONNO Donor Ligands

Oxovanadium(IV) complexes of N2O2 type Schiff bases derived by the condensation of 5-chloro-2-hydroxyacetopheneone or 5-chloro-2-hydroxy-3-nitroacetophenone with trans-1,2-diaminocyclohexane have been synthesized and characterized by elemental analysis, IR and electronic spectra, magnetic moments, ESR, XRD and thermal analysis. The thermal behaviour of the complexes has been assessed using TG-DTG analysis and both the complexes exhibit loss of crystal water in first step whereas ligand segments in the subsequent steps. The various kinetic and thermodynamic parameters such as Ea, ΔH, ΔS, ΔG have been calculated from the TG data. The complexes act as oxidation catalysts for the oxidation of styrene in presence of hydrogen peroxide. The solid state electrical conductivity of complexes show their semiconducting behavior. The geometry around oxovanadium(IV) in both complexes is square pyramidal. The IR spectra suggest bi-negative tetradentate nature of the ligands with ONNO donor sequence sites of the azomethine nitrogen and phenolic oxygen. The crystal system, lattice parameters and unit cell volume of both the complexes have been determined by XRD and belongs to monoclinic crystallized system.

Performance of magnesium phosphate cement at elevated temperatures

This research studied effect of elevated temperature on properties of magnesium phosphate cement (MPC). Properties, including strength, colour, mass loss, and microstructure, of MPC specimens before and after exposure different high temperature were measured or observed in this paper. Seven sample mixtures contained varying amounts of fly ash and sand are considered in the experimental program. The mechanical properties of MPC were measured by heating 40×40×160mm sample to 130, 500 and 1000°C at a rate of 10°C/min. The obtained results demonstrate that strength of MPC decreased significantly when the temperature passed 130°C. After 130°C, the amplitude of strength decreased of MPC became less with the increasing of temperature. The results of Differential thermal analysis (DTA) and thermo-gravimetric analysis (TG) indicate that the crystal water in MKP·6H2O were lost at the temperature of 125°C. The loss of crystal water in MKP·6H2O was the main reason of strength decreasing and mass loss of MPC after exposure to high temperature. The results also show that the presence of fly ash and sand decrease residual strength of MPC.

IR laser-induced protein crystal transformation.

A method and the design of instrumentation, and its preliminary practical realisation, including test experiments, with the object of inducing phase changes of biomolecular crystals by controlled dehydration through heating with infrared (IR) light are described. The aim is to generate and select crystalline phases through transformation in the solid state which have improved order (higher resolution in X-ray diffraction experiments) and reduced mosaic spread (more uniformly aligned mosaic blocks) for diffraction data collection and analysis. The crystal is heated by pulsed and/or constant IR laser irradiation. Loss of crystal water following heating and its reabsorption through equilibration with the environment is measured optically by a video system. Heating proved superior to traditional controlled dehydration by humidity change for the test cases CODH (carbon monoxide dehydrogenase) and CLK2 (a protein kinase). Heating with IR light is experimentally simple and offers an exploration of a much broader parameter space than the traditional method, as it allows the option of varying the rate of phase changes through modification of the IR pulse strength, width and repeat frequency. It impacts the crystal instantaneously, isotropically and homogeneously, and is therefore expected to cause less mechanical stress.

Performance and Utilization of Recycled Aggregates for Airport Cement Concrete Pavement

Cement concrete of airport pavement can be crushed into aggregates for recycle using, and the performance and utilizations of the recycled aggregates were discussed and researched herein. Sieve analysis indicated that the concrete should be crushed many times till the percentage of critical size (31.5mm) can satisfy the gradation requirements. Due to loss of crystal water, the density and water absorption of recycled aggregates were different from the natural ones, so that an empirical corretion equation was addressed subsequently. When the recycled aggregates used in the stablized base, theres no avilable method could yield the optimum water content, therefore a series of compaction and compression tests were employed to set up a modified design method. The results indicated the shrinkage property of recycled aggregates were susceptible to the moisture, either the skeleton-dense material structure and limiting the fine aggregates content were possible ways to eliminate the sensitivity. 7-day unconfined compressive strength results proved the recycled aggregates were suitble for the base course of heavy duty highways and airfield in grade E/F as well.

Synthesis, characterization and antitumor activity of rare earth (Y, La) substituted phosphotungstates containing 5-fluorouracil

Two rare earth substituted Keggin-type phosphotungstates containing 5-fluorouracil, K10C4H4FN2O2Y(PW11O39)210H2O (FYPW) and K9(C4H4FN2O2)2La(PW11O39)218H2O (FLaPW) were synthesized in aqueous solution, and the structures were characterized by Fourier transform infrared spectroscopy (FT-IR), element analysis, inductively coupled plasma spectrometry (ICP), X-ray powder diffraction (XRD) and 1H nuclear magnetic resonance (NMR). Thermal analysis showed that the decomposition processes of the two compounds could be divided into three steps, the loss of crystal water, the decomposition of 5-fluorouracil unit and the decomposition of Keggin-type polyanions. The in vitro cytotoxicities against HEK 293, HeLa and HepG-2 cells were studied by methyl thiazolyl tetrazolium (MTT) assay. The results showed that FYPW and FLaPW had higher antitumor activities than 5-fluorouracil, C4H4FN2O2H2PW12O408H2O and rare earth substituted polyoxometalates K11Ln(PW11O39)2nH2O (Ln=Y, La). It was concluded that introducing 5-fluorouracil and rare earth (Y or La) into its structure was a considerable way to enhance antitumor activities of polyoxometalates.

Visualization of Microwave Energy Distribution in a Multimode Microwave Cavity Using CoCl2 on Gypsum Plates

This study provides a facile method to map the microwave field distribution in a multimode microwave cavity. Anhydrous calcium sulfate powder was used to make the gypsum plates that were used as the carrying medium. Cobalt chloride hexahydrate, whose color changes when losing part or all of its crystal waters, was selected as an indicator of the energy absorption. The cobalt chloride aqueous solution at a concentration of 1.6% was absorbed by the dried gypsum plates. After introducing the plates into a microwave field, those areas that receive more microwave energy were preferably heated, resulting in the release of the moisture and consequently the loss of crystal water from the cobalt chloride hexahydrate. The color change on the plate formed a color map indicating the microwave field distribution. This method was used to investigate the energy distribution of a microwave oven by placing single or multiple plates in horizontal or vertical positions at different locations in the cavity.

Thermal behavior of Cd2+ and Co2+ phenyl-vinyl-phosphonates under non-isothermal condition

The thermal behavior of Cd2+ and Co2+ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation of the organic radical with formation of the pyrophosphoric anion.

Dielectric study of natural inyoite in the frequency range from 10−1 to 107 Hz and the temperature range from −50 to 140°C

For the first time, the method of dielectric dispersion in the 10−1–107 frequency range is applied to study temperature the dependences of permittivity, conductivity, and dielectric modulus of natural inyoite in the temperature range from −50 to 140°C. An anomalous increase in the parameters under consideration is observed at temperatures between 87 and 98°C. According to thermal gravimetrical measurements, this range is characterized by an anomaly resulting from a partial loss of crystallization water.

Thermal stability and oil absorption of aluminum hydroxide treated by dry modification with phosphoric acid

The dry modification of aluminum hydroxide powders with phosphoric acid and the effects of modification of technological conditions on thermal stability, morphology and oil absorption of aluminum hydroxide powders were investigated. The results show that the increase of mass ratio of phosphoric acid to aluminum hydroxide, the decrease of mass concentration of phosphoric acid and prolongation of mixing time are favorable to the improvement of thermal stability of aluminum hydroxide; when the mass ratio of phosphoric acid to aluminum hydroxide is 5:100, the mass concentration of phosphoric acid is 200 g/L and the mixing time is 10 min, the initial temperature of loss of crystal water in aluminum hydroxide rises from about 192.10 to 208.66 °C, but the dry modification results in the appearance of agglomeration and macro-aggregate in the modified powders, and the oil absorption of modified powders becomes higher than that of original aluminum hydroxide.

Copper Bis(1‐methyl‐5‐nitriminotetrazolate): A Promising New Primary Explosive

AbstractCopper bis(1‐methyl‐5‐nitriminotetrazolate) (1) was synthesized and investigated as a new primary explosive. Compound 1 was obtained by dehydration of diaquabis(1‐methylnitriminotetrazolato)copper(II) dihydrate (2) or diaquabis(1‐methylnitriminotetrazolato)copper(II) (3) at 120 °C. Complexes 2 and 3 are easily formed by the reaction of 1‐methyl‐5‐nitrimino‐1,2,3,4‐tetrazole (4) with copper(II) nitrate in aqueous solution in high yields. Single crystals of 1 were obtained by recrystallization from dry methanol, whereas wet methanol favors the yield of diaquabis(1‐methyl‐nitriminotetrazolato)copper(II) dimethanolate (5). Compound 1 was characterized by using single‐crystal X‐ray diffraction, IR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). The sensitivities were investigated by using the BAM drophammer and friction tests, and the heat of formation was calculated on the basis of electronic energies at the B3LYP/SDD level of theory. Compound 1 shows an impact sensitivity that is five times higher and a friction sensitivity that is ten times lower than that of lead azide, which is appropriate. In addition, the long‐term stability of 1 at higher temperatures was tested by using isothermal safety calorimetry (TSC). Compounds 2 and 3 were characterized by single‐crystal X‐ray diffraction, IR spectroscopy, elemental analysis, DSC, bomb calorimetry, and BAM sensitivity tests. In addition, compound 5 was characterized by single‐crystal X‐ray diffraction and elemental analysis. The dehydration of 2 was determined by using thermal gravimetry (TG) to occur by the loss of crystal water in one discrete step. (© WILEY‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Investigation of Thermal Stability of Zn(II), Pt(II) and Pd(II) Complexes with (E)-2-oxo-2-{N'-[1-(pyridin-2-yl)ethylidene]hydrazino}acetamide

Thermal stability of neutral Zn(II), Pd(II) and Pt(II) complexes of formulae [Zn(apsox)2]·3H2O and [M(apsox)Cl] (M=Pd(II), Pt(II), HL=(E)-2-oxo-2-{N ’-[1-(pyridin-2- yl)ethylidene]hydrazino}acetamide) were studied. The results of DSC and TG analyses within the temperature range from 20 to 600 °C in nitrogen atmosphere showed that the loss of crystal water represents the first step during decomposition of the octahedral Zn(II) complex followed by structural rearrangement of its anhydrous form. After that the complex remained stable to about 330 °C. Different from neutral square-planar Pd(II) and Pt(II) complexes, a satisfactory resolution of the peaks in DSC of the Zn(II) complex enabled determination of the activation energies of its structural transformation and thermal degradation.

In situ investigations of the bulk structural evolution of vanadium-containing heteropolyoxomolybdate catalysts during thermal activation

The bulk structural evolution of a vanadium-containing heteropolyoxomolybdate (HPOM), H 4[PVMo 11O 40] × 13H 2O, with vanadium substituting for Mo in the Keggin ion, was studied under reducing (propene) and partial oxidation reaction conditions (propene and oxygen) by in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) combined with mass spectrometry. During treatment in propene, the loss of crystal water in the temperature range from 373 to 573 K was followed by a partial decomposition, reduction of the average Mo valence, and formation of a characteristic cubic HPOM at 573 K. This behavior is similar to the structural evolution of H 3[PMo 12O 40] ×13H 2O during treatment in propene. The formation of cubic Mo x [PVMo 11− x O 40] with Mo centers on extra Keggin framework positions and V centers remaining in the lacunary Keggin ion coincides with the onset of catalytic activity at ∼ 573 K. Detailed investigations of the local structure around the vanadium centers in Mo x [PVMo 11− x O 40] have made it possible to propose a model for the geometric structure of the active site in Mo- and V-containing metal oxide catalysts. The cubic Mo x [PVMo 11− x O 40] phase prepared from H 4[PVMo 11O 40] × 13H 2O is stable in propene and oxygen up to ∼ 620 K and exhibits an onset of activity at ∼ 573 K. This onset of activity is correlated to characteristic changes in the average local Mo structure, indicating a reversible transition from the reduced state of the active site in Mo x [PVMo 11− x O 40] to an oxidized state under propene oxidation reaction conditions.

In situ bulk structural study on solid-state dynamics and catalytic activity correlations of a H4[PNbMo11O40] partial oxidation catalyst

Abstract We report on the preparation and characterization of a niobium containing Keggin type heteropolyoxomolybdate (HPOM), H4[PNbMo11O40] · 13 H2O, with Nb substituting Mo in the Keggin ion. H4[PNbMo11O40] · 13 H2O exhibits a long-range order structure similar to that of H3[PMo12O40] · 13 H2O. The structural evolution of H4[PNbMo11O40] · 13 2O was studied under reducing (propene) and partial oxidation reaction conditions (propene and oxygen) by in situ X-ray diffraction and X-ray absorption spectroscopy combined with mass spectrometry and corroborated by thermogravimetric analysis. Following the loss of crystal water in the temperature range from 373 K to 573 K, a partial decomposition and reduction of the molybdenum and the formation of a characteristic cubic HPOM is observed at 573 K, similar to the structural evolution of H3[PMo12O40] · 13 H2O and H4[PVMo11O40] · 13 H2O during treatment in propene. However, in contrast to H3[PMo12O40] · 13 H2O and H4[PVMo11O40] · 13 H2O, the cubic HPOM decomposes rapidly and the MoO3 formed is subsequently reduced to MoO2. Nb centers in the Keggin ion considerably destabilize the HPOM and accelerate the decomposition towards MoO3. A similar structural evolution is observed under propene and oxygen. The formation of the cubic HPOM with Mo centers on extra-Keggin framework positions coincides with the onset of catalytic activity. However, at about 673 K the active phase further decomposes to a mixture of MoO3 and a more stable cubic HPOM resulting in a pronounced decrease of the catalytic activity. Evidently, preparation and structure-activity relationships for Nb containing mixed metal oxide catalysts need to take into account the particular structure directing properties of Nb during thermal activation.