An improved synthesis of disulfides linked β-cyclodextrin dimer and its analytical application for dequalinium chloride determination by spectrofluorimetry

An improved synthesis of beta-cyclodextrin (beta-CD) dimer, containing two P-CD moieties that are linked through their sides by disulfides was presented. The dimer was characterized by means of IR,H-1 NMR and elemental analysis. The inclusion complexation behavior of beta-cyclodextrin dimer with dequalinium chloride (DQC) was studied in an aqueous NH4 Ac-HAc buffer solution of pH 4.00 at room temperature by spectrofluorimetry. The apparent association constant of the complex was 1.67 x 10(4) l mol(-1), which showed higher affinity than native beta-CD (K-s = 4.99 x 10(2) l mol(-1)). Based on the significant enhancement of fluorescence intensity of DQC, a spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of DQC in bulk aqueous solution in presence of beta-CD dimer. The linear range was 6.38-1.60 x 10(3) ng ml(-1) with the detection limit 1.9 ng ml(-1). There was no interference from the excipients normally used in tablets and serum constituents. The proposed method was successfully applied to the determination of DQC in tablets and serum. (c) 2005 Elsevier B.V. All rights reserved.