Detecção eletroquímica do fungicida tiabendazol extraído de amostras de suco de uva integral por ponto nuvem com eletrodo de diamante dopado com boro.

Abstract

Whole grape juice, in Brazil and in the world, has been gaining prominence over the years as it represents an excellent option for wine, due to its provenance and in terms of substances with antioxidant potential, even though it can be consumed more widely by the population. The increase in consumption requires greater production capacity and, therefore, the improvement of management techniques and extensive use of intensive agricultural products, such as pesticides. Since the ingestion of these substances in food predicts different types of intoxication, acute or chronic, techniques with the potential to determine and detect them appear as a quality control measure. In this sense, the methodology proposed in this work aims to detect and determine the Thiabendazole (TBZ) fungicide in whole white grape juice, combining Cloud Point Extraction (CPE) with High Performance Liquid Chromatography (HPLC) coupled with electrochemical detection using a Boron-Doped Diamond electrode (DDB). In view of this, Cyclic Voltammetry and Differential Pulse techniques were used for the electrochemical characterization of TBZ and its behavior on the surface of the working electrode. From these techniques it was possible to select the best pH condition for the mobile phase (7.0), respecting the limits of use of the chromatographic column. The best conditions for extraction and pre-concentration of TBZ pointed to a CPE performed at pH 6.0, by adding 1mL of the surfactant Tergitol TMN 6 at 10% (m/m), without heating (at 27°C) and ultrasonic agitation (20 kHz) for 60 min. The procedure showed a pre-concentration factor (FC) of 13. The HPLC separation was performed in C8 column, in mobile phase with Phosphate Buffer (pH 7.0):ACN in the ratio 69:31 (V/V), flow of 1.2 mL/min and electrochemical detection with DDB by applying 1.40 V x Ag/AgCl (3.0 mol/L). The process was duly validated, presenting limits of detection (LOD) and quantification (LOQ) of 14.5 μg/L and 36.2 μg/L, respectively. These values are approximately 240 times lower than what was found in the literature for the determination of TBZ in whole grape juice. Method recovery was evaluated between 98.7% and 116.1% with a coefficient of variation between 4.8% and 7.4%. The application of the proposed method allowed the detection and determination of TBZ in one of the analyzed samples of commercial white whole grape juice.