1426 Munaretto et al.: Journal of aoaC InternatIonal Vol. 99, no. 6, 2016 SPECIAL GUEST EDITOR SECTION Guest edited as a special report on “Multiclass, Multiresidue Methods for Determination of Pesticides by Modern Extraction and Detection Techniques: the Combination of QuEChERS and High- Resolution Mass Spectrometry (HRMS)” by Tomas Tuzimski. 1 Corresponding author’s e-mail: renato.zanella@ufsm.br This study was funded by the Brazilian National Council for Scientifc and Technological Development and the Coordination for the Improvement of Higher Education Personnel, which provided fnancial support and fellowship grants. DOI: 10.5740/jaoacint.16-0276 Quantitative Multiclass Pesticide Residue Analysis in Apple, Pear, and Grape by Modifed QuEChERS and Liquid Chromatography Coupled to High-Resolution Mass Spectrometry Juliana S. Munaretto, Mariela de S. Viera, Manoel l. MartinS, and Martha B. adaiMe, renato Zanella 1 Federal University of Santa Maria, Chemistry Department, Laboratory of Pesticide Residue Analysis (LARP), Roraima Avenue 1000, 97105-900 Santa Maria-RS, Brazil Most of the analytical methods currently applied in food control laboratories are focused on the determination of target compounds using LC coupled to tandem MS, which is an effective technique, but low-resolution MS is limited. Thus, a method for determination of pesticide multiresidues in fruits (pear, apple, and grape) using a modifed quick, easy, cheap, effective, rugged, and safe method and LC coupled to quadrupole time-of-fight (Q-TOF) MS was developed and validated. The proposed method showed good linearity (r 2 > 0.99) from 1 to 100 μg/L. Recoveries for blank samples spiked at 0.01, 0.04, and 0.10 mg/kg were between 66 and 122%, with RSDs <28%. Respective LOQs for apple, pear, and grape matrixes were 0.01 mg/kg for 112, 120, and 118 compounds, and 0.04 mg/kg for 22, 12, and 17 compounds, and average mass accuracy error was 3.2 ppm. LC with Q-TOF MS detection using protonated molecular ion and/or adducts and mass accuracy provided reliability for the method. The proposed method is effective for pesticide residue determination in apple, pear, and grape samples, proving that high-resolution MS using full scan mode can be a powerful and reliable technique for quantifcation purposes, being adequate for application in the surveillance of maximum residue limits set by different legislations. A nalysis of pesticide residues is of paramount importance for protection of human health and for trade and offcial control purposes. A great number of substances have been used in agriculture, and regulatory guidelines set maximum residue limits (MRLs) in food to avoid contamination and negative health effects (1, 2). In Brazil, the monitoring of pesticide residues in food is regulated by the Ministry of Agriculture, Livestock, and Food Supply, and by Codex Alimentarius worldwide; in both cases, minimum MRL values of 0.01 mg/kg are established (3, 4). These low MRLs have promoted the development of more powerful and sensitive analytical methods to comply with the requirements in complex samples such as food (5). Thus, most of the analytical methods currently applied in food control laboratories are focused on identifcation of target compounds (6–10). Jardim and Caldas (11) presented two Brazilian pesticide residue monitoring programs between 2001 and 2010 in which a total of 13 556 samples of 22 fruit and vegetable crops were analyzed. Pesticide residues were found in 48.3% of the samples; 13.2% presented some irregularity, mostly “nonauthorized active ingredient use”; and less than 3% of the samples showed residue levels above the MRL. In general, the scenario of pesticide residues in foods investigated within the Brazilian governmental monitoring programs is similar to what has been found in other countries (8, 11). Currently, LC coupled to MS represents the most fexible and effective (i.e., high sensitivity and selectivity) technique used to determine chemical contaminants in many different food matrixes (12–15). These multiresidue methods are typically carried out using MS with triple quadrupole (QqQ) in selected reaction monitoring mode (15–19). Although LC coupled to tandem MS (MS/MS) provides adequate quantifcation performance and high effciency for multiresidue analyses, low- resolution sequential MS is sometimes limited for trace analysis in complex matrixes due to the presence of several interferences, and false negatives can also occur due to insuffcient selectivity (15). High-resolution MS (HRMS) instruments working in full scan mode show high specifcity due to high mass accuracy and high mass resolution (resolving power) and they are able to provide greater reduction in chemical noise, thereby enhancing the selectivity. However, HRMS instruments such as time-of-fight (TOF) or Orbitrap have been applied mainly for structure elucidation or confrmation purposes (10, 20). Modern quadrupole TOF (Q-TOF) instruments performing MS/MS analysis generate spectra with better qualitative information, providing enough sensitivity to quantify target contaminants at concentrations below their MRLs (1, 21). Because modern residue monitoring programs are based in multiclass/multiresidue pesticide determination, the introduction of new, faster, and more effective analytical approaches is