Cloud point method applied to the extraction and preconcentration of thiabendazole pesticide from whole grape juice samples and amperometric detection by HPLC

Abstract

A cloud point method was developed and applied for the first time to extract and preconcentrate thiabendazole (TBZ) from commercial whole grape juice samples, with determination by high performance liquid chromatography coupled to electrochemical detection (HPLC/EC), using a cathodically pretreated boron-doped diamond electrode (BDD). The best conditions for extraction and preconcentration of TBZ by cloud point extraction (CPE) were performed at pH 6.0, by adding 1 mL of the surfactant Tergitol TMN-6 at 10% (mass-to-mass ratio), without heating (at 27 °C) and ultrasonic stirring time of (20 kHz) for 60 min. The HPLC/EC determination was duly validated in a C8 column, in mobile phase with a 69 : 31 ratio (V/V) of phosphate buffer (pH 7.0):ACN, at a flow rate of 1.2 mL min⁻¹ and electrochemical detection with BDD electrode by applying 1.40 V × Ag/AgCl (3.0 mol L⁻¹). Under these conditions, the procedure showed a preconcentration factor (F_C) of 21.7, and limits of detection (LOD) and quantification (LOQ) of 6.64 × 10⁻⁹ mol L⁻¹ (or 1.33 μg L⁻¹) and 1.66 × 10⁻⁸ mol L⁻¹ (or 3.34 μg L⁻¹), respectively. The method provided a percent recovery of 81% to 98%, with a coefficient of variation between 3% and 15%.