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Title of Thesis

Tauqir Ahmad
Institute/University/Department Details
University of Karachi/ Department of Pharmaceutical Chemistry
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
suphacetamide, degradation products, suphanilamide, antioxidants, sodium metabisulphite, sodium edentate

The degradation reactions and metabolic transformation of sulphacetamide and suphanilamide have been reviewed along with the analytical techniques used for detection, identification and assay of these compounds. The various physicochemical and biological factors affecting the formulation of eye-drops have been discussed

The photolysis of sulphacetamide and sulphanilamide has been studied at pH 1-13 in buffered and unbuffered solutions using thin layer chromatography and spectrophotometric techniques. Sulphanilamide has been shown to be an early intermediate in the degradation sequence of sulphacetamide in both acid and alkaline solutions. The various degradation products of sulphacetamide have been separated on fluorescent silica gel layers and some of these have been identified as sulphanilamide, sulphanilic acid, azobenzene-4, 4-disulphonamide, azoxybenzene-4, 4-disulphonamide, azobenzene-4, 4-disulphomic acid and blue product. On the basis of partial characterization a skeleton of the possible structure of blue product has been suggested

Various methods available for the assay of sulphonamides have been examined and found to be inapplicable to the present work. A multicomponent spectrophotometric method has, therefore, been developed to assay sulphacetamide, sulphanilamide and the major degradation products, i.e. azobenzene-4, 4-disulphonamide and blue product, during photolysis, and to follow the kinetics of degradation. A number of reaction schemes for the degradation pathways of sulphacetamide and sulphanilamide have been proposed

The photolysis of sulphacetamide proceeds by a second-order reaction at pH 1-13. The log k-pH profiles for sulphanilamide and sulphacetamide are non-linear, which is most likely to be due to a difference in the state of ionization of the molecules at the reaction pH. The buffer salts (citrate, borate) catalyse the rate of photolysis probably by facilitating singlet to triplet transitions and further conversions to the degradation products

Sulphacetamide undergoes hydrolysis of sulphanilamide which may be attacked on the aromatic-NH2 group and/or the –SO2NH2 group leading to the formation of azo and azoxy derivatives and/or the blue product and sulphanilic acid through radical mechanism. The formation of the azo derivative appears to be favored in alkaline solution, whereas that of the blue product in acid solution. The apparent quantum yields for the photolysis of sulphacetamide and sulphanilamide at pH7 (phosphate buffer) and 0.17 and 0.33 respectively

Among the antioxidants studied, a combination of sodium metabisulphite or thiourea and sodium edentate appears to be most effective for the photo stabilization of aqueous solutions of sulphacetamide and sulphanilamide

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents 0
133.35 KB
2 1 Literature Survey 12
1181.24 KB
  1.1 Introduction 12
  1.2 Chemistry Of Sulphacetamide 17
  1.3 Degradation Reactions Of Sulphacetamide 18
  1.4 Application Of Physiochemical Techniques To The Study Of Sulphacetamide And Degradation Products 31
  1.5 Formulation Of Eye-Drops 63
3 2 Qualitative Studies 81
1112.07 KB
  2.1 Materials 81
  2.2 Methods 85
  2.3 Photolysis Of Sulphacetamide And Sulphanilamide 90
4 3 Quantitative Studies 135
4096.47 KB
  3.1 Assay Produres 135
  3.2 Kinetic Studies 160
  3.3 Determination Of Quantum Yield 282
5 4 Discussion And Conclusions 303
1593.97 KB
  4.1 Discussion 303
  4.2 Conclusions 354
  4.3 Suggestions For Further Work 359
  4.4 Appendices 362
  4.5 Appendix-A 362
  4.6 Appendix-B 369
6 5 References 407
330.95 KB