A novel spectrofluorometric method for the determination of methiocarb using an amphiphilic p-sulfonatocalix[4]arene

The characteristics of host–guest complexation between tetrabutyl ether derivatives of p-sulfonatocalix[4]arene (SC4Bu) and methiocarb [3,5-dimethyl-4-(methylthio) phenyl methylcarbamate] were investigated by fluorescence spectrometry. Upon addition of methiocarb, the fluorescence intensity of SC4Bu was quenched regularly and a slight red shift was observed for the maximum emission peak. These results indicated that the SC4Bu-methiocarb complex was formed a 1:1 mole ratio. An association constant of 1.67 × 104 L mol−1 was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed. Based on the results, a novel spectrofluorimetric method was described for the determination of methiocarb with a detection limit at 0.05 μg mL−1. This method is very simple and shows high sensitivity and selectivity. Moreover, the proposed method was successfully applied to the determination of methiocarb in water samples.

Graphical abstract. The characteristics of host–guest complexation between tetrabutyl ether derivatives of p-sulfonatocalix[4]arene (SC4Bu) and methiocarb [3,5-dimethyl-4-(methylthio) phenyl methylcarbamate] were investigated by fluorescence spectrometry. A 1:1 stoichiometry for the complexation was established and was verified by Job's plot. The interaction mechanism of the inclusion complex was discussed. The quantum-mechanical molecular model was implemented in the Gaussian 03 program package.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► In this paper, the host–guest complex between SC4Bu and methiocarb were studied. ► A 1:1 stoichiometry for the complexation was established. ► The limit of detection is 0.05 μg mL−1. ► The relevant free energy change for this system is ΔG = −24.03 kJ mol−1 at 298 K.