Analysis of creams

A standard procedure, consisting of twotlc systems, for the qualitative control of creams is presented. All common cream excipients, except those of very high polarity, are separated in a simple gradient elution system, using diethyl ether as the eluent in a chromatographic chamber saturated withn-pentane. The very polar cream base components are separated usingn-butanol-glacial acetic acid-water (20+2+5) as the eluent. The chromatographic behaviour of common cream excipients as well as threefna cream bases and four commercial cream bases is discussed.     

Analysis of creams

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.     

Analysis of creams

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 onov-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 wax sx and cetiol v could be determined easily, whether or not a sample clean-up step was incorporated.     

Analysis of creams

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 onov-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 wax sx and cetiol v could be determined easily, whether or not a sample clean-up step was incorporated.     

Analysis of creams

The possibilities for the determination of active components in creams by acid-base titrations in non-aqueous solvents were investigated. Interference by cream-base components with the titration of weak organic bases and their halides with perchloric acid in acetic acid, and with the titration of weak acids with tetrabutylammonium hydroxide in N,N-dimethylformamide were studied. It appeared to be possible to determine alkaloid halides, salicylic acid, hexachlorophene and methyl salicylate without previous clean-up of the cream samples.     

Analysis of creams

A standard procedure, consisting of twotlc systems, for the qualitative control of creams is presented. All common cream excipients, except those of very high polarity, are separated in a simple gradient elution system, using diethyl ether as the eluent in a chromatographic chamber saturated withn-pentane. The very polar cream base components are separated usingn-butanol-glacial acetic acid-water (20+2+5) as the eluent. The chromatographic behaviour of common cream excipients as well as threefna cream bases and four commercial cream bases is discussed.     

Analysis of creams

The possibilities for the determination of active components in creams by acid-base titrations in non-aqueous solvents were investigated. Interference by cream-base components with the titration of weak organic bases and their halides with perchloric acid in acetic acid, and with the titration of weak acids with tetrabutylammonium hydroxide in N,N-dimethylformamide were studied. It appeared to be possible to determine alkaloid halides, salicylic acid, hexachlorophene and methyl salicylate without previous clean-up of the cream samples.     

Analysis of creams

The uv absorbing properties of the components of the cream bases as described in the Formulary of the Dutch Pharmacists were investigated. Directuv spectrophotometric determinations without any clean-up steps appeared to be possible for a number of drugs (e.g. tripelennamine HCl, tretinoin, salicylic acid, methyl salicylate, resorcinol, clioquinol), with the help of a solvent mixture in which the cream samples dissolved completely to yield clear solutions. Correcting for the contribution to theuv absorbance by the preservative is sometimes necessary and can be achieved by measuring the absorbance at two wavelengths. The determination of chlorhexidine, as an example of a basic drug withuv absorbing properties which prevent direct measurements of the solution of the cream samples, could be achieved after removal of the interfering compounds by a simple liquid-liquid extraction.     

Structure of cholesterol-containing creams

The colloidal structure of a four-component system consisting of cholesterol, fatty alcohol, petrolatum and water was studied. Depending on the variation of temperature, chain length of the fatty alcohol and concentration of all components, creamy systems of w/o type could be prepared, which present different structural features. Liquid phases as well as crystalline and/or liquid crystalline phases participate in the structure of the creams. The liquid phases are represented by water and by liquid hydrocarbons of low molecular weight of petrolatum. Part of the surfactants is dissolved in this latter phase. The liquid crystalline phase is formed by cholesterol and fatty alcohol together. The characterization of the lamellar liquid crystalline phase was performed by polarized light microscopy and small angle x-ray diffraction. The formation of the lamellar liquid crystals is favoured in a certain molar concentration range of cholesterol and fatty alcohol. The liquid crystalline region is largest with tetradecanol. The lamellar liquid crystals swell with water up to a certain limit. This incorporation of water stabilizes the lamellar liquid crystals so that they are stable in a larger temperature range. The crystalline structures form a network consisting of solid hydrocarbons and the eutectic mixture of cholesterol and fatty alcohol. If water is present the surfactants crystallize as hydrates. A surplus of water can be dispersed as droplets mechanically. Referring to maximum capacity of water incorporation, systems with lowest crystalline amounts (only the network of petrolatum) were best. The surfactants should be completely dissolved.     

Stability of dithranol in creams

The stability of the anthrachinone derivative dithranol in creams was studied during storage at temperatures of 4°C and 20°C. Aluminumcoated tubes with 0.1, 0.3 and 0.5% dithranol were stored and samples were analysed immediately and after 3, 6 and 12 months of storage. The 0.3% dithranol cream was also stored in polypropylene tubes. Drug concentration was analysed by highperformance liquid chromatography. All concentrations tested were stable for 12 months of storage at 4°C in aluminumcoated tubes. This means that these low concentrations are sufficiently stable to be prepared in advance for at least 12 months if prepared as described and kept refrigerated. Polypropylene tubes should not be used.     

BB creams and their photoprotective effect

BB creams appeared on the market quite recently. These creams, which give a perfect complexion by covering up the skin’s blemishes, have a photoprotective effect in the majority of cases. An SPF value ranging from 10 to 45 concerning the products we tested is displayed on the packaging. The 21 commercially-available BB creams were tested to assess their efficacy (determination of the SPF) and their photostability (determination of their efficacy after UV irradiation). It was shown that 70% of the products tested have an SPF determined in vitro by us which matches the SPF displayed on the product. For the remaining 30%, it can be seen that products have SPF values of between 2 and 10 times lower than those indicated on the products. It can also be noted that there is a large disparity in terms of photostability since, under the same experimental conditions, however, some products only lose 5% of their photoprotective efficacy, whereas others lose 60%.     

盐酸多塞平乳膏的经皮渗透性比较研究

目的:对比两种盐酸多塞平乳膏的体外透皮特性。方法:建立反相高效液相色谱法测定盐酸多塞平含量;以小型猪皮肤为屏障,改良Franz单室扩散池为体外模型,进行体外经皮渗透实验,求算累积透过量,并测定药物在皮肤的贮留量和剩余量。结果:盐酸多塞平检测浓度的线性范围为0.010 01～0.800 8μg(r=0.999 8),方法准确简单,重复性好;两种乳膏24 h内的皮肤透过量接近(尤其是4 h内几乎重合),在皮肤中的贮留量也相近,药物透皮后均未发生构型的转化。结论:预测两种药品的药效和安全性基本一致。