Influence of Pretreatment of Expanded Graphite on Its Sorption Properties with Respect to Petroleum

Petroleum sorption on expanded graphite prepared from residual graphite hydrosulfate at 300-900°C was studied as influenced by pretreatment of the sorbent with water.     

Interconnection between the Structures and Sorption Characteristics of Mesophase Materials of MCM-41 Type Containing Alkylpyridines

Under the conditions studied for the synthesis of mesophase materials with alkylpyridinium halides an increase in the density of packing of these molecules in the encapsulated micelles was observed with an increase in the length of the alkyl radicals. The difference in the density of packing of these surface active reagents (SAR) depended to a considerable extent on the perfection of the hexagonal structure and the characteristic absorption properties of the mesophase materials of MCM-41 type.     

Stabilization of Graphite Nitrate by Intercalation of Organic Compounds

New thermally stable intercalation compounds of graphite were obtained by the further intercalation of a series of organic compounds into graphite nitrate. The stabilization is explained by the formation of hydrogen bonds between the protonated form of the modifying substance and neutral surrounding molecules.     

Synthesis and properties of residual graphite nitrate obtained by treatment of graphite nitrate with water

The possibility of obtaining residual graphite nitrate by water treatment of graphite nitrate and its subsequent drying was studied. The expansion coefficients were determined in the temperature range 500–900°C with a step of 100°C for the samples obtained.     

Influence Exerted by Pyrite Impurity in the Initial Graphite on Properties of Residual Graphite Hydrosulfates

The influence exerted by the particle size and the distribution of sol impurities in the initial graphite, and also by pyrite additives, on the properties of residual graphite hydrosulfates synthesized by oxidation in the CrO₃-H₂SO₄ system was studied.     

Sorption of Industrial Oil by Expanded Graphite

Sorption of industrial oil by expanded graphite prepared from residual graphite hydrosylfate at 300-900°C was studied. The sorption isotherms of both neat oil and oil from its aqueous suspension were measured. The sorption capacity for oil was studied as influenced by the specific surface area and specific volume of expanded graphite sorbent.     

Effect of Solubilization in Bitemplate Synthesis of a Homologous Series of Organosilica Mesophases and Mesoporous Molecular Sieves

Peculiarities of bitemplate synthesis of a homologous series of organosilica mesophases (precursors of mesoporous molecular sieves of MCM-41 type) were studied, and an influence of a nature of templating substances and a solubilization on a perfection of their spatial structure was found. n-alkyl(C₈–C₁₈)pyridinium halides as solubilizers (micelle-forming surfactants) and monoethanolamides of saturated n-(C₁₀–C₁₆)aliphatic acids as solubilizate were used. Some physicochemical factors promoting a spatial ordering of organosilica mesophases and mesoporous molecular sieves were considered.     

Development and validation of a LC-MS/MS method for d-cycloserine determination in human plasma for bioequivalence study

A reliable and high throughput high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated for determining levels of the antitubercular drug-d -cycloserine in human plasma. Plasma samples analyte with an internal standard (IS) (niacin) were prepared by solid-phase extraction using Waters Oasis MCX cartridges. The chromatographic separation was performed using the HILIC mode on a YMC-Pack SIL-06 column (150?×?4.6 mm; 3 μm) under isocratic conditions. The run time of analysis was 5 min. The mobile phase consisted of methanol, propanol-2 and 0.075 % trifluoroacetic acid (66.5:28.5:5, v/v/v). Protonated ions formed by turbo ion spray in positive mode were used to detect the analyte and the IS. MS/MS detection was used to monitor the fragmentation of 103–75?m/z for cycloserine and 124 to 80?m/z for niacin (IS) on an API 4000 (AB Sciex) triple quadrupole mass spectrometer. A linear dynamic range of 0.3–30 μg/mL was established for cycloserine using 0.2 mL human plasma and a 1 μL injection volume. The mean relative recovery of cycloserine and niacin were 77.2 and 82.4 %, respectively. The procedure of sample preparation was consistent and reproducible (precision, 0.8–3.4 %; accuracy, 93.8–104.9 %). The method was validated in accordance with requirements of the European Medicines Agency and successfully applied to a bioequivalence study of 250 mg tablet formulations in 23 healthy human subjects.     

Determination of Rhein in blood plasma by HPLC with UV detection and its application to the study of bioequivalence

A method is proposed for determining rhein (an active metabolite of diacerein) in human blood plasma by reversed-phase high-performance liquid chromatography with UV detection. The analyte was selectively extracted from blood plasma by liquid-liquid extraction with a 5% solution of tert-butyl methyl ether in ethyl acetate. The recovery of rhein is 68 ± 3%, LOQ 100 ng/mL. The stability of the analytes and linearity, selectivity, sensitivity, reproducibility, and accuracy of the developed method are evaluated. The pharmacokinetics of diacerein in the oral administration of drug formulations by 18 healthy volunteers is studied.