No abstract

Cellulose was treated with subcritical water in a batch reactor within a temperature range of 200–300 °C and reaction time of 5–60 min. The main phases, such as water-soluble fraction, acetone-soluble fraction and solid residue (remaining cellulose or char), were separated and analyzed. The analysis of water-soluble phase was done by HPLC equipped with UV and RI detector, whereas acetone-soluble phase was analyzed by GC–MS. Total sugar content was determined by the phenol-sulfuric acid colorimetric method. The properties of char such as specific surface area, pore volume, and pore diameter were determined by gas adsorption method. A water-soluble phase mainly consists of sugar monomers and monomer degradation products, while acetone-soluble phase, referred to also as bio-oil, consists of furans, phenols, carboxylic acids, aldehydes, ketones, and high molecular compounds. The reaction mechanism of cellulose in subcritical water has been proposed based on the obtained results.

No abstract

Prednisolone, an important active pharmaceutical ingredient, is a synthetic glucocorticoid used for the preparation of various pharmaceutical products with anti-inflammatory and immunosuppressive properties. It is a challenge in high-performance liquid chromatography (HPLC) to separate the prednisolone peak and its structurally related substance (hydrocortisone), which only differs in a double bond at the C-1 position. Successful application of the HPLC method according to the European Pharmacopoeia monograph for related substances of prednisolone is very often limited to the chromatographic system available. This is due to the nonbaseline separation of the prednisolone and hydrocortisone peaks, which is strongly influenced by the instrument parameters and the chosen C18 column. First, an adjusted European Pharmacopoeia method for related substances of prednisolone was developed within the allowable adjustments. Next, an improved stabilityindicating reversed-phase HPLC method for related substances of prednisolone was developed and validated for use in quality control laboratories for routine analysis. The optimized separation was performed on a Phenomenex Gemini C18 column (150 mm × 4.6 mm, 3 μm) using a gradient mobile-phase system consisting of acetonitrile/tetrahydrofuran/water (15:10:75 v/v/v), acetonitrile/water (80:20 v/v), and ultraviolet detection at 254 nm. A baseline separation was achieved, and stability indicating capability was demonstrated by a forced degradation study.

In the present work, the degradation of different sugars, such as lactose, cellobiose, sucrose, galactose, glucose, fructose and xylose, was performed in batch reactor with subcritical water at temperature of 250 °C and reaction time of 1, 5 and 15 min. The yields of water-soluble phase, acetonesoluble phase, solid residue and gases were determined. The influence of reaction time and difference in sugar structure on the yield of phases and conversion of sugars was studied. Sugars with keto-and furanose structures were less stable than aldo-and pyranose-sugars. The most stable sugars were aldo-hexoses (galactose and glucose). The water-soluble fraction, which is composed of sugars and their derivatives, was analyzed by HPLC using RI and UV detectors. The detected degradation products by HPLC were:

No abstract

The solubilities of pesticides (permethrin and dicofol) in CO 2 were measured by a static-analytic method at pressures ranging from 10.0 MPa to 25.0 MPa and temperatures of 293.2 K, 303.2 K, and 313.2 K. Due to the nonconventional shape of some solubility isotherms, solid-liquid transitions of pesticides under pressure of CO 2 were determined using a modified capillary method. Since the solubilities depend on solvent density, the experimental binary solid-fluid equilibrium data were correlated as a function of solvent density by two different models.