الفهرس | Only 14 pages are availabe for public view |
Abstract The present thesis includes a systematic study on the spectrophotometric determination of the drug sildenafil citrate by forming ion-associate or ion-pair complexes between the drug and some chromotropic acid azo dyes. The present thesis comprises four chapters: 1- Chapter 1: It includes an introduction concerning the important rules of analytical chemistry in the analysis of the pharmaceutical products. Also this chapter includes the spectrophotometric methods used for pharmaceutical analysis. 2- Chapter 2: It comprises the literature survey on the different analytical methods used for determination of sildenafil citrate. Also it includes a literature data on the spectrophotometric determination of some pharmaceutical compounds by using chromotropic acid azo dyes. 3- Chapter 3: It includes the experimental part, where the materials and reagents, preparation of various compounds and solutions and the instruments used are presented. Also this chapter includes the optimum experimental conditions for formation of the ion-associate/pair complexes between the investigated drug and the mono- and bi-azo dyes of chromotropic acid. 4- Chapter 4: It includes the results and discussion. a- Using of some chromotropic acid mono-and bi-azo dyes for quantitative spectrophotometric determination of the investigated drug, where in slightly acidic solutions, the nitrogenous drugs are present in positively charged protonated forms, so ion-associates complexes are formed between the drug and anionic dyes of chromotropic acid. These ion-associates are extracted in organic solvent followed by spectrophotometric determination at their λmax. b- The stoichiometric composition of the formed complexes was carried out using continuous variation method. The results indicated that the complexes 84 were formed having a ratio 1: 2 or 1: 1 (reagent:drug) in case of mono- or – bi-azo dyes, respectively. c- Study on the influence of acidity, effect of extraction solvents, reagent concentration, time and foreign ions are carried out to establish the optimum experimental conditions for formation of the ion-associates. Also the association constants of the formed ion-associates were calculated. d- The ion-association reactions were used for quantitative determination of the drug in pure form and in their pharmaceutical formulation (vigoran). e- The results obtained were treated statistically for estimation of the precision and accuracy. Also the present methods were validated, through calculation of the molar absorptivity, Sandell’s sensitivity, detection limit, quantification limit, application range and comparison of the results with one of the published methods which based on direct measurement of the absorbance of the formed charge-transfer complex with σ acceptors like iodine. f- The solid complexes of SC with the cited reagents were prepared, and then subjected to the elemental analysis, IR and UV/Vis measurements to elucidate the structure of these complexes. The results showed that, the elemental analysis values of C, H, N and S are in good agreement with the calculated values according to the proposed molecular formulae of the complexes. The small shift in the absorption maxima (λmax) in the UV/Vis spectra and the change in the molar absorptivity values of the solid complexes relative to those of pure azo dyes is an indication for formation of new ion-pair complexes. This was confirmed by the changes occuring in the position of the IR spectral bands of the prepared solid complexes. The thesis ends with a list of references that was of great help to the author. |