Fluorimetric determination of sulphathiazole in honey by means theformation of CDs inclusion complexes

Abstract

tThe inclusion complex of sulphathiazole in -cyclodextrin has been investigated. A 1:2 stoichiometryof the complex was established and formation constants K2(42.83 ± 3.27 M−1) and K1(4.98 ± 0.36 M−1)were calculated by using the changes produced on the native fluorescence of the drug, when includedon the hydrophobic cyclodextrin cavity. An enhancement in the fluorescence emission of sulphathiazoleand protection of the drug against photochemical reactions has been attained upon inclusion. In solu-tions of -CD dual emission (458 nm) was noticed in STZ. Formation of the inclusion complex of STZshould result in dual emission, which is due to a twisted intramolecular charge transfer band (TICT).A fluorimetric method for the determination of sulphathiazole has been proposed and applied in honeywithout sample treatment. The optimized fluorimetric method showed detection and quantitation limitsof 9.74 ng/g and 32.48 ng/g, respectively. Selectivity is high, showing no cross-reactivity to other chemi-cally related antibiotics. The results obtained for blind honey samples (mean recovery 97%), were in goodagreement with those obtained by liquid chromatography separation and mass spectrometry detection(LC–MS) (mean recovery 102%), showing that the proposed method might be used for the determinationof sulphathiazole residues without expensive equipment.