Figure 1.
Bentazon (A) and CD derivative (B), where R is H, 2-hydroxypropyl (CH2CHOHCH3) or sulfobutylether ((CH2)4 SO3 Na) for βCD, HPCD and SBECD, respectively.
Figure 2.
Electrochemical oxidation of bentazon.
(A) Differential pulse voltammetry curves for 5.0×10−4 M Btz in buffer phosphate pH 6.0 in the absence and presence of different HPCD concentrations. Curves 1–10: 0, 2, 4, 6, 8, 10, 12, 14, 20 and 30 mM HPCD; (B) Current dependence on the concentration of HPCD for bentazon in buffer phosphate pH 6.0. Current values obtained from DPV measurements. Inset: Plot of 1/[CD] versus 1/(1-I/I0) for bentazon in buffer phosphate pH 6.0.
Figure 3.
Determination of the stoichiometry of the complex.
Continuous variation plot (Job plot) of the absorption change in dependence of the bentazon mole fraction.
Figure 4.
(a) Bentazon, (b) βCD, (c) Btz-βCD (PM), (d) Btz/βCD (KN), (e) Btz/βCD (FD).
Figure 5.
(a) Bentazon, (b) HPCD, (c) Btz-HPCD (PM), (d) Btz/HPCD (KN), (e) Btz/HPCD (FD).
Figure 6.
(a) Bentazon, (b) SBECD, (c) Btz-SBECD (PM), (d) Btz/SBECD (KN), (e) Btz/SBECD (FD, 1∶1), (f) Btz/SBECD (FD, 1∶2).
Table 1.
FT-IR spectrum assignments for Btz.
Figure 7.
(A) Bentazon, (B) HPCD and (C) Btz/HPCD inclusion complex (KN).
Figure 8.
Thermal stability of free molecules and the inclusion complex.
DTA thermogram of (a) bentazon, (b) HPCD and (c) Btz/HPCD inclusion complex (KN).
Table 2.
Thermal decomposition temperature obtained by DTA.
Figure 9.
Btz photodegradation profiles in distilled water and in the presence of different cyclodextrins. Bentazon (•), Btz/βCD (▴), Btz/SBECD (○), and Btz/HPCD (▪).
Figure 10.
Concentration of bentazon against increasing concentrations of HPCD.
Figure 11.
Dissolution profiles in water of bentazon (•), Btz/βCD (KN) (▴), Btz/SBECD (KN)* (○), and Btz/HPCD (KN) (▪). (*: inclusion complex and free bentazon mixture).
Table 3.
Surface tension (γ) of water and aqueous solutions of systems under study.