Instituto de Química

ABSTRACT This paper aims at describing a method for the determination of different classes of pesticides in sugarcane juice. The QuEChERS sample preparation method was used for the extraction of pesticides and their quantification was carried out by liquid chromatography-tandem mass spectrometry with an electrospray ionization source. After the optimization of the determination parameters of the pesticides, the method was validated by evaluating the analytical curves, linearity, limits of detection and quantification, precision (repeatability and intermediate precision), accuracy (recovery) and matrix effect. The detection limits of the method ranged from 0.83 to 16 μg L−1 and recoveries between 75% and 120% with an RSD lower than 20%. No pesticide residues were detected amongst the samples under analysis.

In this work, two analytical liquid chromatography methods were developed and compared for the characterization of aqueous phases from pyrolysis of lignocellulosic biomasses. NanoLC electron ionization-mass spectrometry (EI-MS) represents a novel and useful tool for both separation and identification of semi/nonvolatile and thermolabile molecules. The use of nanoscale flow rates, the highly reproducibility, and high detailed information on EI spectra are the principal advantages of this technique. On the other hand, comprehensive 2D-LC, providing a two-dimensional separation, increases the overall peak capacity lowering the occurrence of peak coelutions. Despite the use of reversed phase modes in both dimensions, a satisfactory degree of orthogonality was achieved by the employment of a smart design of gradient elution strategies in the second dimension in combination with photodiode array detection (PDA) and atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). Because of the absence of the preliminary extraction procedure, the fingerprint obtained for these samples results is independent of the extraction yield or contamination contrary to the gas chromatography-mass spectrometry (GC-MS) approach where a liquid-liquid extraction of the water phase is necessary. The main classes of identified compounds were phenols, ketones, furans, and alcohols. The synergistic information on the two powerful analytical approaches, e.g., NanoLC EI-MS and LC × LC, in the identification of such complex samples has never been investigated and fully benefit on the one hand from the superior degree of mass spectral information from EI-MS and on the other hand from enhanced LC × LC compound separation.