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.