Estimativa de figuras de mérito para um método de determinação de benzo(a)pireno em azeite de oliva por extração líquido-líquido sob baixa temperatura e espectroscopia de fluorescência

Abstract

Low temperature liquid-liquid extraction was employed to extract benzo(a)pyrene (B(a)P) from olive oil. The obtained extract was analyzed by fluorescence spectroscopy. The efficiency of Constant energy synchronous fluorescence (CESF) was evaluated, since it is a essential factor for the detection of B(a)P, in the concentration value (2,0 µg L-1) established by the European Union Comission as the maximum limit of this substance in edible oils. The analyte was extracted from 3,0 mL of olive oil ¬¬¬by 6,0 mL of acetonitrile and acetone 3:2 (v/v) using vortex mixer at 1500 rotations per minute during 5 minutes. The sample underwent cooling at –18 °C which only the oil phase was frozen. The liquid extract was evaporated until dryness at 45 °C and resuspended by 2,5 mL of dimethyl sulfoxide. Fluorescence parametrs were optimized individually through the evaluation of the solvent effect, temperature and the slit length for both excitation and emission monochromators. After optimization, the extraction efficiency for the analyte was about 40% utilizing CESF with the excitation wavelength of 388 nm and Δν in 1230 cm-1. Linearity of the optimized method was established in the range 0,8 – 3,2 µg L-1 to B(a)P, with theoretical LD was 0,008 µg L-1 and LQ was 0,8 µg L-1. The precision and the accuracy were assessed at three concentration levels (0,8; 2,0 and 3,2 µg L-1) with relative standard deviation and bias values less than 15%, respectively. The method represents a viable alternative in comparison to ISO 15753:2016 and other researchs that study the presence of B(a)P in trace concentrations in oils, being simple, fast, selective and highly sensitive. The aplication of low temperature LLE and fluorescence spectroscopy does not require successive clean up steps such as solid phase extraction, providing a lower consumption of organic solvents.