title: Effect of formulation pH and storage temperatures on the preservative efficacy of some gases used as propellants in cosmetic aerosols.
abstract: The effects of changes in formulation pH and storage temperature on the preservative activities of some aerosol propellants--butane, carbon dioxide, dimethylether and their combinations were investigated. A preservative challenge test method was used to determine the survival rates of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus niger at formulation pH levels 5.80, 7.28 and 8.10 and storage temperatures of 20 degrees, 30 degrees and 40 degrees C. A significant decrease in the pH of formulations was observed with no corresponding changes in the antimicrobial effectiveness when carbon dioxide was incorporated. Alterations in the antimicrobial profiles of these propellants due to changes in formulation pH were dependent on the propellant and the species of the micro-organism, especially when single propellants were used. Results also showed that the propellants exert antimicrobial activities against the various organisms at the three storage temperatures but there were significantly greater inhibitory activities at 40 degrees C. With a combination of 10% butane/dimethylether (1:2) and 10 bar carbon dioxide there were no differences in the degree of microbial inhibition at the various formulation pH levels and storage temperatures. In most cases, the organisms were completely inactivated within 24 h. These findings showed that the combination of butane/dimethylether with carbon dioxide could be used to protect against microbial contamination and spoliage of formulations of different pH levels as well as those meant for storage at different temperatures.
authors.affiliation: Hygiene Institute, University of Heidelberg, Germany.
authors.forename: Y K
authors.initials: YK
authors.lastname: Ibrahim
authors.forename: H G
authors.initials: HG
authors.lastname: Sonntag
mesh_terms: D000335:Aerosol Propellants; D001234:Aspergillus niger / Q000254:growth & development; D002073:Butanes / Q000494:pharmacology; D002176:Candida albicans / Q000254:growth & development; D002245:Carbon Dioxide / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D003358:Cosmetics / Q000592:standards*; D004340:Drug Contamination / Q000517:prevention & control*; D004926:Escherichia coli / Q000254:growth & development; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008738:Methyl Ethers / Q000494:pharmacology; D011310:Preservatives, Pharmaceutical; D011550:Pseudomonas aeruginosa / Q000254:growth & development; D013211:Staphylococcus aureus / Q000254:growth & development; D013997:Time Factors
chemical_list: D000335:Aerosol Propellants; D002073:Butanes; D003358:Cosmetics; D008738:Methyl Ethers; D011310:Preservatives, Pharmaceutical; D002245:Carbon Dioxide; C046888:butane; C033413:dimethyl ether