Determination of thiabendazole in aqueous solutions using a cucurbituril-enhanced fluorescence method

The complexation of thiabendazole (TBZ) with the cucurbit[6]uril (Q[6]), cucurbit[7]uril (Q[7]) and symmetric tetramethyl-cucurbit[6]uril (TMeQ[6]) in aqueous solution has been investigated using UV–vis and fluorespectrometry. The experimental results show 1:1 host–guest inclusion complexes at pH 6.5 for all three macrocyclic hosts, and the corresponding formation constants by UV and fluorescence methods are (5.37 ± 1.05) × 104 L mol−1 and (1.47 ± 0.41) × 104 L mol−1 for the Q[6]-TBZ system (7.76 ± 0.51) × 104 L mol−1 and (9.36 ± 0.22) × 104 L mol−1 for the Q[7]-TBZ system (1.28 ± 0.78) × 104 L mol−1 and (2.69 ± 0.55) × 104 L mol−1 for the TMeQ[6]-TBZ system, respectively. Based on the enhancement of the fluorescence intensity of TBZ with the addition of Q[n]s in neutral media, a fluorespectrometry method for the determination of TBZ in aqueous solution in the presence of Q[n] was established. In the range of 6.0 × 10−8 mol L−1–8.0 × 10−6 mol L−1 a linear relationship was obtained between fluorescence intensity and TBZ concentration. The detection limit was found to be between 5.51 and 8.85 × 10−9 mol L−1. The interference of coexisting ions was found to be slight. The proposed method has been successfully applied to the determination of TBZ in different aqueous solutions with satisfactory recoveries of 92–103%. The method seems to be suitable for environmental water analysis.