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IntroductionDiosmin, which is chemically named 3′,5,7-trihydroxy-4′-methoxy flavone 7, rutinoside (I), is a newly developed flavonoid in Rutaceae plants. Flavonoids are widely used for their phlebotonic and antioxidant properties, and also as vascular protectors. [1][2][3][4][5][6][7][8] Recent clinical studies have demonstrated that the diosmin can be used to treat venous leg ulcers and hemorrhoids. 3 Diosmin drug has been successfully used as chemopreventive agents in urinary-bladder 9 and colon carcinogenesis. 10 The drug shows good tolerability and is quite safe and nontoxic. 3 Diosmin has certain biological activities, including an anti-inflammatory effect and an inhibition of prostaglandin synthesis.11 In view of increasing interest in these bioflavonoids, especially that used in treating chronic venous, chronic hemorrhoids and as antioxidants, several methods have been reported for the determination of diosmin in plant extracts, 12,13 biological fluids, 13,14 and pharmaceutical formulations. 12 A survey of the literature reveled that there are few methods for diosmin determination in pharmaceutical formulations or biological fluids. These methods include: spectrophotometry, spectrodensitometry, 15 and liquid chromatography 16 as well as HPLC methods. 17 Recently, an excellent HPLC method for the simultaneous determination of diosmin in flavonoid extracts and soft gelatin capsules has been published. 17 Currently, no literature data could be found on the electrochemical behavior of diosmin, in general, or its voltammetric determination, in particular.Therefore, the aim of the present study is to investigate the oxidative behavior of the diosmin at GCE using cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques, and also to optimize the experimental conditions for the determination of this compound in pharmaceutical dosage forms. A methodology for the direct and simple determination of the drug in spiked human serum at a very low level is also included. Experimental Reagents and solutionsDiosmin and Dioven ® tablets were obtained from Amriya Rhone-poulenc Pharmaceutical Industries Co., Alexandria, Egypt. The stated composition of each tablet contains 150 mg diosmin. A diosmin stock solution (1 × 10 -3 M) of diosmin was prepared daily by dissolving an appropriate amount in 2 ml of NaOH (0.02 M) and completed to 10 ml with double-distilled water. Dilute solutions were then prepared by diluting the stock solution with water in calibrating measuring flasks, transferred to polyethylene bottles, and were finally kept in a refrigerator. A systematic study on the electrochemical behavior of diosmin in Britton-Robinson buffer (pH 2.0 -10.0) at a glassy carbon electrode (GCE) was made. The oxidation process of the drug was found to be quasi-reversible with an adsorptioncontrolled step. The adsorption stripping response was evaluated with respect to various experimental conditions, such as the pH of the supporting electrolyte, the accumulation potential and the accumulation time. The observed an...

The redox characteristics of the drug domperidone at a glassy-carbon electrode (GCE) in aqueous media were critically investigated by differential-pulse voltammetry (DPV) and cyclic voltammetry (CV). In Britton-Robinson (BR) buffer of pH 2.6-10.3, an irreversible and diffusion-controlled oxidation wave was developed. The dependence of the CV response of the developed anodic peak on the sweep rate (nu) and on depolizer concentration was typical of an electrode-coupled chemical reaction mechanism (EC) in which an irreversible first-order reaction is interposed between the charges. The values of the electron-transfer coefficient (alpha) involved in the rate-determining step calculated from the linear plots of E (p,a) against ln (nu) in the pH range investigated were in the range 0.64 +/- 0.05 confirming the irreversible nature of the oxidation peak. In BR buffer of pH 7.6-8.4, a well defined oxidation wave was developed and the plot of peak current height of the DPV against domperidone concentration at this peak potential was linear in the range 5.20 x 10(-6) to 2.40 x 10(-5) mol L(-1) with lower limits of detection (LOD) and quantitation (LOQ) of 6.1 x 10(-7) and 9.1 x 10(-7) mol L(-1), respectively. A relative standard deviation of 2.39% (n = 5) was obtained for 8.5 x 10(-6) mol L(-1) of the drug. These DPV procedures were successfully used for analysis of domperidone in the pure form (98.2 +/- 3.1%), dosage form (98.35 +/- 2.9%), and in tap (97.0 +/- 3.6%) and wastewater (95.0 +/- 2.9%) samples. The method was validated by comparison with standard titrimetric and HPLC methods. Acceptable error of less than 3.3% was also achieved.

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Microstructures of sodium borosilicate glasses with intermediate silica content, doped with CuO, were examined. Electron micrographs of heat-treated glasses show two randomly distributed phases. DC conductivity measurements indicate that alkali oxide is associated with B2O3. CuO is assumed to act as a network modifier in the borate matrix and does not affect the phase separation process. Optical absorption in the UV and visible regions was also examined. Phase separation causes a shift of the UV edge towards longer wavelengths, which is considered to be a result of light scattering on SiO2-rich particles produced by heat treatment.

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