Pressurized Liquid Extraction Coupled with LC–ESI–MS–MS for the Determination of Herbicides Chlormequat and Mepiquat in Flours Stefano Marchese 1,2,& , Daniela Perret 1 , Eleonora Bafile 2 , Alessandra Gentili 2 , Fulvia Caretti 2 Marco Berardino 2 1 Laboratorio Chimico per la Sicurezza, Universita ` ‘‘La Sapienza’’ di Roma, Rome, Italy 2 Dipartimento di Chimica, Universita ` ‘‘La Sapienza’’ di Roma, Piazzale Aldo Moro no 5, P.O. Box 34, Posta 62, 00185 Rome, Italy; E-Mail: stefano.marchese@uniroma1.it Received: 25 March 2009 / Revised: 11 June 2009 / Accepted: 25 June 2009 Online publication: 12 August 2009 Abstract This paper describes a new method for the rapid extraction and unequivocal confirmation of herbicides chlormequat and mepiquat in wheat flours and various flours utilized in infant foods. The highly automated extraction procedure is based on accelerated solvent extraction, followed by liquid chromatography-tandem mass spectrometry as a confirmatory analysis. Typical recoveries from flours and baby food samples ranged from 83 to 99% at a fortifi- cation level of 10 ppb, corresponding to the maximum residue limits established by the European Union; while relative standard deviations (RSD) were less than 10% for all samples. The limit of detection (signal-to-noise ratio = 3) of the method for the considered phenols in baby food samples are less than 0.1 lgg -1 . Traces of the selected herbicides have been detected in about 50% of baby foods, bought from different Roman supermarkets and butcher shops, applying the described methodology. Keywords Column liquid chromatography–mass spectrometry Pressurized liquid extraction Chlormequat and mepiquat Introduction Plant growth regulators are essential components of modern agriculture in developed countries, and their use is increasing in third world countries. In agricultural areas, large quantities of these compounds are employed, most of which are applied either directly to soil or sprayed over crop fields. As a conse- quence, they can enter as contaminants into natural waters, soils or foods. We have focused this study on a particular group of quaternary ammonium plant growth regulator compounds: chlorm- equat and mepiquat. In agriculture, the quaternary ammo- nium herbicides, chlormequat [(2-chlo- roethyl)trimethylammonium); CQ] and mepiquat [(1,1-dimethylpiperidinium); MQ] are utilized either individually, as mixtures, or together with other pesticides [1]. CQ is registered in at least 17 countries and it is particularly adopted to promote sturdier growth in wheat, rye and oats thus reducing the risk of lodging. CQ, in particular, has attracted the attention of enforcement laboratories and regulatory agencies in Europe, re- flected by the numerous publications and website notifications on infringing levels of residues, especially in cereals and their derivatives [2–5]. The Codex Alimentarius Commis- sion has set maximum residue limits (MRLs) for CQ at 3 ppm in wheat and rye (2 ppm in wheat flour), and at 10 ppm in oats [6]. Neither the Codex Alimentarius Commission nor the EU have intro- duced MRLs for MQ in food; however, 2009, 70, 761–767 DOI: 10.1365/s10337-009-1266-x 0009-5893/09/09 Ó 2009 Vieweg+Teubner | GWV Fachverlage GmbH Original Chromatographia 2009, 70, September (No. 5/6) 761