ANALYSIS OF PHARMACEUTICAL CREAMS - A USEFUL APPROACH BASED ON SOLID-PHASE EXTRACTION (SPE) AND UV SPECTROPHOTOMETRY

Solid-phase extraction (SPE) using C-18, diol and ion-exchange sorbent s followed by UV spectrophotometric (conventional and derivative mode) assay was applied to the analysis of basic, acidic and neutral drugs commercially available in creams. A representative set of drugs (prome thazine, chlorhexidine, benzydamine, ketoprofen, ibuprofen, fentiazac, piroxicam, fluorouracil, crotamiton and hydrocortisone acetate) was s elected, and for each drug the appropriate SPE conditions (adsorption, washing and elution) were investigated to obtain a practical and reli able sample clean-up. It was shown that the developed SPE procedures w ere capable of removing interfering cream components (excipients inclu ding preservatives) allowing accurate spectrophotometric analyses to b e performed. In some applications, derivative spectrophotometry was ad vantageous over the conventional absorption mode with respect to highe r selectivity and versatility.