Spectrofluorimetric determination of diclofenac in the presence of alpha-cyclodextrin

This study focuses on the complex formed between a-cyclodextrin (CD) and th e anti-inflammatory drug diclofenac in aqueous solution and also on its pot ential analytical applications. It was corroborated that the fluorescence e mission band of diclofenac is significantly intensified in the presence of alpha-CD. From the changes in the fluorescence spectra, it was concluded th at alpha-CD forms a 1:1 inclusional complex with diclofenac and its equilib rium constant was calculated to be 1.20(3) x 10(3) M-1. With the purpose of characterizing the inclusion complex, the acid-base behaviour of diclofena c in both the presence and absence of alpha-CD was spectrophotometrically i nvestigated. From the results obtained, it was inferred that both the carbo xyl and the secondary amino groups of the guest molecule remain outside the cyclodextrin cavity. Further details on the complex structure was obtained by H-1 NMR measurements and semiempirical calculations. In addition to the analysis of the alpha-CD-diclofenac interaction, a new approach for the qu antification of diclofenac in the presence of alpha-CD is described in the range 0-5 mu g ml(-1). An application of the method to the determination of the studied drug in pharmaceutical preparations is shown. (C) 2000 Elsevie r Science B.V. All rights reserved.