Probing the Impact of a Pesticide on the Dielectric Properties of Vegetable Peel Extracts in the Low-Frequency Regime

Abstract

The frequency-dependent dielectric properties of pristine and a pesticide treated bottle gourd and pumpkin peel extracts have been measured in the frequency range 100Hz-2MHz. Dielectric parameters such as dielectric permittivity (εʹ), dielectric loss (εʹʹ), and electrical conductivity (σ) of pure and fipronil mixed peel extracts are compared to assess the effect of fipronil on the dielectric properties of the vegetable peel extracts. In the low-frequency regime, the values of εʹ and εʹʹ of peel extracts are observed significantly higher due to the dominance of water-triggered surface charge polarization and dipolar polarizations. Remarkable changes in the values of εʹ, εʹʹ, and σ for bottle gourd and pumpkin peel extracts were observed on increasing the fipronil concentration. Almost monotonic increase in εʹ, εʹʹ, and σ values is observed with the mixing concentration of fipronil as the concentration of fipronil increases. This concentration (of fipronil) dependent behavior of dielectric parameters could offer the way to assess the presence of the pesticide residues in vegetable extracts. The observed dielectric behavior of samples was further analyzed by principal component analysis that offered the discrimination of pure and fipronil treated samples. The presented observations would serve as a tool for the dielectric spectroscopy-based discrimination of pesticide residues in horticultural extracts.