PRESERVATIVE DISTRIBUTION IN EMULSIONS by SYED JAMSHED ALI KAZMI B. Sc., Agra University, India, 1964 B. Pharm., University of Karachi, Pakistan, 1968 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN PHARMACY in the Division of Pharmaceutics of the Faculty of Pharmaceutical Sciences We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA April 1971 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, 8, Canada. i ABSTRACT Until recently, evaluation of the effectiveness of preservatives in emulsified systems has depended largely on time-consuming microbiological techniques. Mathematical models have now been developed which enable the amount of preservative necessary for adequate preservation to be calcu lated. Determination of the physico-chemical parameters for these models is again a time-consuming process, especially where complex emulsions are involved. In the present work a three-chambered dialysis method has been investigated. Using this method it is possible to determine the concen tration of preservative in the various phases of an emulsion and thus the total concentration required for adequate preservation. Various factors affecting the distribution of preservatives between oil and water and the interaction between preservatives and surfactant are discussed. These factors are then related to the problem of the distribution of a preservative in an oil in water emulsion system. Methodology used to evaluate the various physico-chemical parameters is reviewed and equations for representing the results are discussed. The distribution of benzoic acid between peanut oil and water and mineral oil and water systems was studied over a wide concentration range. The interaction of benzoic acid with aqueous solutionsof the nonionic surfactant cetomacrogol was studied using solubility and equili brium dialysis techniques. The interaction of various other preserva tives with aqueous solutions of the nonionic surfactant cetomacrogol was examined. A comparison was made of various methods of expressing this ii interaction. It is suggested that the Scatchard equation is the most satisfactory equation for describing the binding data. Binding para meters determined from a Scatchard plot in the concentration range of free preservative appropriate for antimicrobial activity were used to calculate the total concentration of preservative required in the sur factant solution. A three-chambered dialysis cell was used to estimate the distribu tion of benzoic acid between the oil phase and the aqueous phase of oil in water emulsions containing peanut oil or mineral oil. The method also differentiates between preservative bound, or solubilized, by the surfactant and free in the aqueous phase. The distribution data was plotted on a three-dimensional graph from which the total concentration of preservative needed to provide a given free concentration in the aqueous phase can be determined. Results from the dialysis method agree closely with those calculated using mathematical models for preservative distribution. Hence the three-chambered dialysis method provides a relatively simple direct method of determining the required preservative concentration without recourse to mathematical models. Supervisor. i i i TABLE OF CONTENTS Page I. INTRODUCTION 1 II. LITERATURE SURVEY 4 A. Distribution of Preservatives in Oil-Water Systems 4 (a) Factors affecting antimicrobial activity of preservatives in oil-water systems 4 (b) Representation of distribution data 11 B. Interaction of Preservatives with Nonionic Surfac tants 18 (a) Potentiation of preservative activity 18 (b) Inactivation of preservative activity 19 (c) Mechanism of inactivation 21 (d) Sites of interaction in surfactant micelle 23 (e) Representation of interaction data 25 C. Distribution and Antimicrobial Activity of Preserva tives in Emulsified Systems 28 D. Prediction of Total Preservative Concentration Re quired in an Emulsion 30 E. Methodology 34 (a) Distribution of preservatives in oil-water systems 34 (b) Interaction of preservatives with nonionic surfactants 35 (c) Distribution of preservatives in oil-water- surfactant systems 43 III. EXPERIMENTAL 46 iv Page A. Apparatus 46 B. Materials 47 C. Temperature 48 D. Analysis of Benzoic Acid 48 E. Analysis of Surface-Active Agents 48 (a) Polarographic analysis 48 (b) Method of Crabb and Persinger 49 F. Permeability of Cellophane Membranes to Cetomacrogol 51 G. Membrane Binding 54 H. Distribution of Benzoic Acid in Oil-Water Systems 55 I. Interaction of Preservatives with Cetomacrogol 55 J. Distribution of Benzoic Acid in Oil-Water-Surfactant Systems 57 (a) Preparation of emulsions 57 (b) Two-chambered dialysis technique 57 (c) Three-chambered dialysis technique 57 IV. RESULTS AND DISCUSSION 61 A. Analysis of Surface-Active Agents 61 B. Permeability of Cellophane Membranes to Cetomacrogol 65 C. Membrane Binding 68 D. Distribution of Benzoic Acid in Oil-Water Systems 68 E. Interaction of Benzoic Acid with Cetomacrogol 71 F. Representation of Preservative-Surfactant Inter action Data 74 G. Distribution of Benzoic Acid in Oil-Water-Surfactant Systems 92 (a) Two-chambered dialysis technique (b) Three-chambered dialysis technique (c) Validity of two- and three-chambered dialysis techniques (d) Applications of three-chambered dialysis technique V. SUMMARY AND CONCLUSION VI. REFERENCES LIST OF TABLES 1. Proportions of benzoic acid undissociated at various pH values 2. Influence of partition coefficient and phase-volume ratio on concentration of preservative in aqueous and oil phase of a two-phase system 3. Minimum inhibitory concentrations and binding parameters for the interaction of preservatives with cetomacrogol 4. Validity of three dimensional calibration curve for the dis tribution of benzoic acid between peanut oil-water-cetomacro- gol systems at various oil-water ratios 5. Validity of three dimensional calibration curve for the dis tribution of benzoic acid between peanut oil-water-cetomacro- gol systems at various cetomacrogol concentrations vii LIST OF FIGURES Page 1. Possible sites of incorporation of solubilizate in a micelle 24 2. Solubility of preservative as a function of surfactant concentration 40 3. Polarographic current voltage curves 50 4. Dynamic dialysis method 53 5. Two-chambered dialysis cell 59 6. Three-chambered dialysis cell 60 7. Polarographic determination of cetomacrogol 62 8. Polarographic determination of surface-active agents 63 9. Colorimetric determination of cetomacrogol ' 64 10. Permeability of Fisher cellophane membrane to cetomacrogol in dynamic dialysis 66 11. Permeability of cellophane membranes to cetomacrogol in equilibrium dialysis 67 12. Binding of benzoic acid with Mi Hi pore VS membrane 69 13. Binding of cetomacrogol with Millipore VS membrane 70 14. Plot of pH-independent partition coefficient of benzoic acid versus the aqueous concentration of unionized benzoic acid 72 15. Plot of pH-dependent partition coefficient of benzoic acid in aqueous phase 73 16. Variation of apparent partition coefficient with free pre servative concentration for the partition of preservative between micelles and aqueous phase of cetomacrogol 77 17. Ratio of Total/Free propyl p-hydroxybenzoate as a function of cetomacrogol concentration at 25° 79 18. Ratio of Total/Free benzoic acid as a function of ceto macrogol concentration at 30° 80 Langmuir-type plot for the interaction of preservatives with cetomacrogol solutions: Benzoic acid and Parahydroxy- benzoic acid Langmuir-type plot for the interaction of preservatives with cetomacrogol solutions: Methyl p-hydroxybenzoate; Propyl p-hydroxybenzoate and Chioroxylenol Double-reciprocal plot for the interaction of preserva tives with cetomacrogol solutions: Benzoic acid and Parahydroxybenzoic acid Double-reciprocal plot for the interaction of preserva tives with cetomacrogol solutions: Methyl p-hydroxyben- zoate; Propyl p-hydroxybenzoate and Chioroxylenol Scatchard plot for the interaction of preservatives with cetomacrogol solutions Variation of free benzoic acid concentration [Df], in the aqueous phase of an emulsion with total benzoic acid con centration [D] for an o/w peanut oil emulsion stabilized with cetomacrogol Ternary graph of the distribution of benzoic acid in an o/w peanut oil emulsion stabilized with cetomacrogol Ternary graph of the distribution of benzoic acid in an o/w mineral oil emulsion stabilized with cetomacrogol Three-dimensional graph of the distribution of benzoic acid in an o/w peanut oil emulsion stabilized with cetomacrogol Three-dimensional graph of the distribution of benzoic acid in an o/w mineral oil emulsion stabilized with cetomacrogol Modified three-dimensional graph of the distribution of ben zoic acid in an o/w peanut oil emulsion stabilized with cetomacrogol Modified three-dimensional graph of the distribution of ben zoic acid in an o/w mineral oil emulsion stabilized with cetomacrogol