Determination of carbaryl and carbofuran in fruits and tap water by β-cyclodextrin enhanced fluorimetric method

Abstract

The effect of β-cyclodextrin (CD) and hydroxypropyl-β-cyclodextrin (HPCD) in water solutions on the UV-Vis and fluorescence spectra of carbaryl (1-naphthyl- N-methylcarbamate, CY) and carbofuran (2,2-dimethyl,2-3-dihydro-7-benzofuranyl- N-methylcarbamate, CF) was investigated. Host–guest interactions were observed by UV-Vis and spectrofluorimetry and the association constants for the 1:1 complexes ( K A, mol −1 dm 3) with CD and HPCD were determined. The values obtained were 190±10 and 123±7 mol −1 dm 3 for CF and 350±50 and 644±53 mol −1 dm 3 for CY, respectively. The values of the fluorescence quantum yield ratios ( φ complexed/ φ free) were 1.24±0.01 with CD and 1.310±0.007 with HPCD for CY, but much higher for CF being 7.0±0.1 with CD and 9.3±0.4 with HPCD. The limits of detection (LOD) for the fluorimetric determination under the better conditions were 14.5 ng cm −3 for the complex CF:CD and 1.94 ng cm −3 for the complex CY:CD in water, with notable improvement specially in the case of CF. We observed higher analytical sensitivity with the cyclodextrins (CDs) in presence of alcohols but not better LOD. The method is rapid, simple, direct and sensitive and the recovery of CY and CF was found to be between 100 and 112% in fruits and 97 and 109% in tap water. The allowed level of carbamates in banana can be detected by the proposed method.