Effect of pH, phosphate buffer concentration and the ionic strength on the stability of cefotetan disodium

The stability of cefotetan disodium between the pH range 2-8 has been studied using a stability-indicating HPLC assay method. The optimum pH range of stability appears to be 3.6-6.4. At pH 2 or 8, the decomposition was approximately 2 times faster than between pH 3.6-6.4. The HPLC method used is accurate and precise with percent relative standard deviation of 1.0 based on 5 readings. The decomposition of cefotetan followed first-order law. The K_h and K_oh values were estimated to be 3.8 and 4.4 × 10⁴ d^-1.     

Important Information for Readers of High-Performance Liquid Chromatography Literature

Important information for developing an internal standard for high-performance liquid chromatography has been presented in a tabular form. If acetonitrile is substituted for methanol, the column lives are longer and costly repairs of the chromatograph are not needed that often. Approximately 1% of acetonitrile can be substituted for 2% of methanol.     

Quantitation of spironolactone in the presence of canremone using high-performance liquid chromatography

Two stability-indicating high-performance liquid chromatography methods have been developed to quantify spironolactone in the presence of its product(s) of decomposition. Both methods are accurate and precise with percent relative standard deviation of 0.7 based on 5 readings using microC₁₈ column and 0.9 using microphenyl column. By using different wavelengths, the sensitivity of the methods to quantify spironolactone or canrenone (the major product of decomposition of spironolactone) can be increased many times. Spironolactone appears to be relatively stable between pH values of about 3.4-5.2. In the acidic pH, the decomposition is slower than on the basic side of the pH. Even at pH 7.3, the decomposition was about 3.1 times faster than at pH 2.3.     

Conformation Analysis of GalNAc‐Appended Sugar Amino Acid Foldamers as Glycopeptide Mimics

Sugar amino acid (SAA)‐based foldamers with well‐defined secondary structures were appended with N‐acetylgalactosamine (GalNAc) sugars to access sequence‐defined, multidentate glycoconjugates with full control over number, spacing and position. Conformation analysis of these glycopeptides by extensive NMR spectroscopic studies revealed that the appended GalNAc units had a profound influence on the native conformational behaviour of the SAA foldamers. Whereas the 2,5‐cis glycoconjugate showed a helical structure in water, comprising of two consecutive 16‐membered hydrogen bonds, its 2,5‐trans congener displayed an unprecedented 16/10‐mixed turn structure not seen before in any glycopeptide foldamer.     

Mango ripening: changes in cell wall constituents in relation to textural softening

Ripening of mango (Mangifera indica L., cv. Alphonso) fruit is characterized by a series of biochemical changes resulting in gradual textural softening. From unripe to ripe stage, the starch content came down from 18% to 0.1%; pectin from 1.9% to 0.5%; cellulose from 2% to 0.9% and hemicelluloses from 0.8% to 0.2%. Concomitantly, the total soluble solids increased from 7% to 20%, total soluble sugars from 1% to 15% and pH increased from 2.8 to 5.1. The increase in activity of several of the carbohydrate‐degrading enzymes, which resulted in solubilization of the various polysaccharide fractions, correlated with fruit‐softening phenomenon. Efficient distribution of ¹⁴C‐starch into glucose, fructose and sucrose revealed considerable sugar interconversions indicating active gluconeogenesis during mango fruit ripening. Copyright © 2005 Society of Chemical Industry     

Quantitation of fluoxetine hydrochloride in capsules using high-performance liquid chromatography

A stability-indicating high-performance liquid chromatographic method for the quantitation of fluoxetine hydrochloride in capsules (the only dosage form available) has been developed. The method is accurate and precise with a percent relative standard deviation of 1.04 based on 6 readings. An excellent separation of fluoxetine from methyltestosterone (the internal standard) was achieved, and sharp peaks were obtained by adding acetic acid to the mobile phase. The inactive ingredients present in the capsule powder did not interfere with the assay procedure. The recovery of fluoxetine from the synthetic mixtures was quantitative. The drug appears to be very stable in the acidic medium and highly susceptible to degradation in the basic medium.     

Mango ripening – Role of carbohydrases in tissue softening

A range of cell wall degrading enzymes, both glycanases and glycosidases, was identified in ripe mango (Mangifera indica cv. Alphonso) fruits. Reduction in the mannose content of the hydrolyzed polymeric fractions of ripe mango revealed the possible involvement of an endomannanase and α-mannosidase, the two major enzymes, in mango fruit softening and ripening phenomena. α-Mannosidase was resolved into isoforms I and II by chromatographic methods and their kinetic and inhibition properties were studied.     

Synthesis, characterization, microstructure determination and thermal studies of poly(N-vinyl-2-pyrrolidone–maleic anhydride–styrene) terpolymer

A series of poly(N-vinyl-2-pyrrolidone–maleic anhydride–styrene) terpolymers have been synthesized using titanium(III)-dimethylglyoxime redox initiator system. The usage of redox initiators in the terpolymerization was limited; hence it should be considered as a new approach. The reactivity of the monomers has been studied by well-accepted Kelen-Tudos and Fineman-Ross linear methods and compared with the nonlinear RREVM method. The results also suggested that the RREVM method is the most reliable and superior method for the estimation of reactivity ratios. The reactivity ratios for the terpolymer (r ₁ 0.99 and r ₂ 0.05) obtained from the RREVM method showed that the N-vinyl pyrrolidone-maleic anhydride complex was more predominant than styrene in the terpolymer and the complex had more attraction toward itself than styrene. The microstructure determination study depicts that alternating polymer can be prepared by increasing the styrene feed content. The resonance factor and polarity of the complex were calculated as 5.01 and 0.93, respectively, which were different from those of the individual monomers. These calculations would help in predicting the association of monomers during copolymerization. It was observed that the glass transition temperature of the terpolymer increased as the complex ratio in the terpolymer increased. The terpolymer was thermally stable up to 323 °C.     

Quantitation of 5-Flucytosine in capsules using high-pressure liquid chromatography

A stability-indicating reversed phase HPLC method for the quantitation of 5-flucytosine in capsules (the only dosage form available) has been developed. The method requires the use of a mobile phase without any counterion and the samples can be assayed at room temperature. The method is simple, reproducible, precise and accurate with percent relative standard deviation of 0.77 based on 6 readings. There was no interference from the excipients present in capsules and from fluorouracil (the major product of decomposition of 5-flucytosine). The recovery of 5-flucytosine from the synthetic mixtures was quantitative. A simple extraction procedure for 5-flucytosine from the capsules has been developed.     

Preparation and Evaluation Of Drug-Containing Chitosan Beads

Sulfadiazine beads were prepared by dropping drug-containing solutions of the positively charged polysaccharide, chitosan, into tripolyphosphate (TPP) solutions. The droplets instantaneously formed gelled spheres by ionotropic gelation, entrapping the drug within a three-dimensional network of the ionically linked polymer. To achieve maximum drug content, high payloads, short gelation times, low TPP concentrations, and a low internal to external phase ratio were required. The chitosan beads showed pH-dependent swelling and dissolution behavior. The beads swelled and dissolved in 0.1N HCl, while they stayed intact in simulated intestinal fluid. The release of sulfadiazine in 0.1N HCl decreased with increasing concentration of TPP, but was independent of the TPP concentration in intestinal fluids. The morphology of the beads was investigated by scanning electron microscopy. The porosity of the beads depended on the method of drying.