Determination and degradation behaviour of thiram and carbendazim by using dispersive liquid to liquid micro extraction

This article describes a novel and sensitive method that employs dispersive liquid-liquid microextraction (DLLME) in conjunction with UV-vis spectrophotometry to detect trace amounts of the fungicides thiram (TMTD) and carbendazim (MBC). The methodology relies on converting TMTD and MBC into a yellow product by using copper sulphate and ethanolic potassium hydroxide, followed by extraction via DLLME. Extraction variables were optimized by using a central composite design (CCD). The method performance was evaluated by using external standard calibration. A linearity range of 0.5 μg/mL to 2.5 μg/mL was found with a correlation coefficient of 0.97. The limits of detection and quantification for TMTD and MBC were 0.002 and 0.2 μg/L, and 0.001 μg/L and 0.1 μg/L, respectively. The relative standard deviation (%) for TMTD and MBC at three concentrations ranged from 3.1 to 16% and from 2.7 to 15.43%, respectively. Recovery rates (%) at three concentrations ranged from 83.6–94.6% for TMTD and 81.4–93.63% for MBC. The equations of degradation for TMTD and MBC in mint plant were C = 2.9e-0.03746t and C = 1.05e-0.04602t. In soil, the equations were C = 2.102e^−0.01653t and C = 15.352e^−0.4992t with R² = 0.973. Additionally, the half-life of TMTD was found to be 3.47 days in mint plant and 35.93 days in soil. Conversely, the half-life of MBC in mint plant was 4.66 days, while in soil it was 43.18 days. The higher half-life of both pesticides in soil compared to the mint plant indicates that these pesticides are resistant to degradation in soil.