The possibilities of the gas--liquid chromatographic analysis with flame ionization detection of creams of the o/w emulsion type were investigated. Interferences by cream base components in the determination of the active compounds were studied. It appeared to be possible to determine active compounds with a retention index lower than 1900 on ov-17 (e.g. methyl salicylate, menthol, thymol camphor) without clean-up of the cream samples; for the determination of compounds with retention indices between 1900 and 3700, a simple clean-up step suffices. The possible analysis of some of the cream base components together with the active compounds of the creams was investigated as well. Cetomacrogol emulsifying wax, lanette was sx and cetiol v could be determined easily, whether or not a sample clean-up step was incorporated.
The possibilities of applying reversed-phase high performance liquid chromatography to the analysis of o/w emulsion type creams without preceding sample clean-up were investigated. The chromatographic behaviour of cream base components and active compounds in reversed phase systems consisting of methanol-water mixtures as the mobile phase and a chemically bonded octadecyl stationary phase, was studied. A number of active compounds and the preservative (sorbic acid) could be determined--often in one chromatographic run--without complications, by simply dissolving the sample in a suitable solvent mixture and injecting an aliquot of the solution into the chromatograph. Separation was achieved by the proper choice of methanol content, pH and ionic strength of the eluent. The compounds were detected by UV absorption. Some of the lipophilic cream base components could easily be determined in the same manner, with methanol as the eluent and with refraction index detection. The developed procedure was applied to the analysis of a number of creams. Some of the results are presented as examples, demonstrating the suitability of the method for quality control purposes.
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