Emulsion Assist.lecturer Qasim Allawi Bader MSc.pharmaceutics College of pharmacy /University of Kerbala

Preservation of emulsions Preservation against microbial growth. Preservation against atmospheric oxygen.

Preservation against growth of microorganism Cause unpleasant odour,discoloration,change in consistency and cracking. Mould growth will appear more serious for the patient bec. It is obvious to the eye and can contain many pathogenic bagteria which may lead to serious health hazard. M.o. multiply well in the aq.phase of the emulsion,most fungi and many bacteria will grow at room temp. and tolerate a wide pH range.

Some E.A. possess antimicrobial activity e.g. alkali soaps,cetremide and to a smaller degree alkyl sulphat. Others such as clays they do not provide the growth of M.O and do not inhibit their growth. Third group which include natural polysaccharides, can be used as energy source by bacteria and moulds. Other constituents of emulsion that can be utilized by the m.o. is aliphatic hydrocarbons by pseudomonas aeurogenosa, arachis oil by aspergillus and liquid paraffin by penicillium.

Heavy contamination may be introduced to emulsion by: 1.Natural E.A. like gum,starches and clays 2.Deionized water because bacteria can multiply in resin beds that used in the purification process. 3.Carelessly cleaned equipment 4.Poor closures on containers

Prevention of bacterial and mould contamination in the emulsion by: 1.Minimizing the four sources of contamination 2.Using antimicrobial agent

Reversal of the sources of contamination 1.Using ing. Of high quality from reliable sources. 2.Boiling water immediately before use to destroy vegetative m.o. 3.Using equipments that is easily cleaned. 4.Choosing well fitting closures.

Using antimicrobial agent This agent should included in the emulsion and should be: 1.Free from toxic effects 2.Bactericidal rather than bacteriostatic. 3.Rapid in action.(from 10 min. to 2 hr). 4.Has wide antibacterial spectrum 5.Resistant to attack by m.o. 6.Retain activity in the presence of large numbers of bacteria 7.Its activity unaffectedby emulsion ingredients.

Bec. Microbial growth occur in the aq.phase of an emulsion,there must be an adequate concentration of preservative in the water and this conc. Is influenced by several factors include: 1.Partitioning of preservative between oil and water 2.Phase volume ratio

Partitioning of preservative between oil and water When the oil:water partition coefficient of a preservative exceeds 1 (as with phenolic bactericides in an arachis oil/water system) then the conc. In the aq. Phase is lower than the overall conc. When this coefficient is less than 1(as with phenol in a liq. paraffin/water system) then the aq.phase conc. Is greater than the overall concentration. Emulsion containing vegetable oils are more difficult to preserve than emulsions containing liq. paraffin.

Phase volume ratio When a preservative is more soluble in water than oil( oil:water partition coefficient is less than 1) then any increment in the proportion of oil increases the conc. Of preservative in the aq.phase. If the preservative is more soluble in oil than water so any increment in the oil proportion will lower the aq. Phase conc.

Examples of preservatives for emulsion 1.Organic acids Benzoic acid good antifungal and antibacterial preservative in pH. Below 5 Used in conc. Of 0.1% w/v with chloroform to preserve liq. Paraffin emulsion Sodium benzoate is more water soluble (1:2) compared with( 1:350) for benzoic acid. Sorbic acid used in conc. 0.1 % w/v to preserve acacia and tragacanth mucilages and non ionic surfactants and it ineffective in pH above 6.5 and irritate the skin of some people

2. Esters of parahydroxybenzoic acid Methyl,ethyl,propyl and butyle esters of PHBA are popular preservatives Active against moulds rther than bacteria Effective at pH 7-9 Cause slight numbing of the mouth. With chain length, activity increased but solubility decreased. Methyl ester is more soluble 1:500

3. Chloroform 4. Chlorocresol 5. phenoxyethanol 6. Quaternary ammonium compounds 7. Organic mercurial compounds

Preservation from atmospheric oxygen Fats and oils of animal and vegetables origin are susceptible to oxidation by atmospheric oxygen and enzymes produced by m.o. And is controlled by antioxidant and antimicrobial preservative respectively.