1520 Lozano et aL.: JournaL of aoaC InternatIonaL V oL. 95, no. 5, 2012 Received November 22, 2011. Accepted by AK February 29, 2012. 1 Corresponding author’s e-mail: amadeo@ual.es DOI: 10.5740/jaoacint.11-509 RESIDUES AND TRACE ELEMENTS In spite of high plant growth regulator application rates, little has been reported in the literature on determination of their residues in fruits and vegetables. This would be useful in monitoring good manufacturing practices and overall safety through the enforcement of maximum residue levels (MRLs). The present work describes method validation for the determination of 1-naphthylacetic acid (NAA) and 2(1-naphthyl)acetamide (NAAm) in tomato and zucchini using the mini-Luke, ethyl acetate (EtOAc) and acetate-buffered quick, easy, cheap, effective, rugged, and safe (QuEChERS) methods. Samples were spiked at two different levels: 50 and 100 µg/kg for NAA and 20 and 100 µg/kg for NAAm. These compounds were analyzed within the same chromatographic run with LC coupled to triple quadrupole MS (LC/(QqQ)MS/MS) in positive and negative electrospray ionization [ESI(+) and ESI(–)] modes for NAAm and NAA, respectively. For analyte confrmation, LC/ESI(-)QTOF-MS was also investigated given that NAA has only one multiple reaction monitoring transition (185.1→140.9 m/z). These three common methods were used to determine linearity, recoveries, precision (RSD), matrix effects, repeatability, and reproducibility (n = 5) for the selected matrixes. In terms of the Directorate-General for Health and Consumers (DG-SANCO) guidelines, only insignifcant differences were found for the multiresidue methods tested, regardless of the commodity. Matrix-matched calibration was used, and LODs were below 10.1 µg/kg for NAA and 6.0 µg/kg for NAAm, which were lower than the MRLs established in current European Union legislation for these compounds. Obtained recoveries for NAA ranged from 87 to 107% with RSD values below 10% for mini-Luke, 83 to 107% with RSD <11% for EtOAc, and 76 to 85% with RSD ≤7% for QuEChERS. NAAm recoveries ranged from 74 to 102% with RSD ≤ 15% for mini- Luke, 76 to 97% with RSD <4% for EtOAc, and 76 to 93% with RSD ≤ 5% for QuEChERS. The linearity of the response over two orders of magnitude was demonstrated (r 2 > 0.996) for all methods used. Good repeatability and reproducibility in terms of RSD were obtained (11.3–17.8%) for these analytical methods. The results were acceptable within the studied ranges for both analytes in all methods. As these multiresidue methods are used at the present time in many laboratories, this survey indicates that these analytes should be included in their monitoring scope. S ynthetic plant growth regulators (PGRs), which control specifc physiological processes in plants such as the division, elongation, and differentiation of plant cells, are used to promote fowering or improve setting in a variety of fruits and vegetables. The application of synthetic 1-naphthylacetic acid (NAA) and 2(1-naphthyl)acetamide (NAAm) auxins (Figure 1) after blossoming is understood to prevent premature fall and thinning of fruits (1–3). However, greater amounts than necessary may act as growth inhibitors and thus be detrimental to the correct development of the plant crops (3). In contrast to most agrochemicals, these compounds in particular are considered to be a moderate hazard to human health with a defned acute reference dose of 0.1 mg/kg bw/day for both NAA and NAAm, as recently reported by the European Food Safety Authority (4). Indeed, the current European Union (EU) regulation has established typical maximum residue levels (MRLs) of 0.05 mg/kg for both NAA and NAAm in most Inclusion of 1-Naphthylacetic Acid and 2-(1-Naphthyl)acetamide into Three Typical Multiresidue Methods for LC/MS/MS Analysis of Tomatoes and Zucchini AnA LozAno European Union Reference Laboratory (EURL), Pesticide Residue Research Group, University of Almería, Department of Hydrogeology and Analytical Chemistry, Ctra. Sacramento S/Nº, La Cañada de San Urbano, 04120, Almería, Spain Andrés Pérez-PArAdA European Union Reference Laboratory (EURL), University of Almería, Pesticide Residue Research Group, Department of Hydrogeology and Analytical Chemistry, Ctra. Sacramento S/Nº, La Cañada de San Urbano, 04120, Almería, Spain University of the Republic, School of Chemistry, Pharmacognosy and Natural Products, 1180 General Flores 2124, Montevideo, Uruguay HorAcio Heinzen University of the Republic, Pharmacognosy and Natural Products, School of Chemistry, 1180 General Flores 2124, Montevideo, Uruguay AmAdeo r. Fernández-ALbA 1 European Union Reference Laboratory (EURL), Pesticide Residue Research Group, University of Almería, Department of Hydrogeology and Analytical Chemistry, Ctra, Sacramento S/Nº, La Cañada de San Urbano, 04120, Almería, Spain Downloaded from https://academic.oup.com/jaoac/article/95/5/1520/5655314 by guest on 13 July 2022