Analytical, Nutritional and Clinical Methods Determination of herbicide residues in olive oil by gas chromatography–tandem mass spectrometry Marı ´a A. Aramendı ´a a , Victoriano Borau a , Fernando Lafont b , Alberto Marinas a, * , Jose ´ M. Marinas a , Jose ´ M. Moreno a , Francisco J. Urbano a a Department of Organic Chemistry, University of Co ´ rdoba, Campus de Rabanales, Ediﬁcio C-3, E-14014 Co ´ rdoba, Spain b Servicio Central de Apoyo a la Investigacio ´ n (SCAI), Unidad de Espectrometrı ´a de Masas, Universidad de Co ´ rdoba, Campus de Rabanales, E-14014 Co ´ rdoba, Spain Received 18 October 2006; received in revised form 22 January 2007; accepted 28 January 2007 Abstract This paper reports a method for the analysis in olive oil of multiresidues of the herbicides of low-medium polarity most widely used by Andalusian olive growers. The method, which uses gas chromatography/tandem mass spectrometry (GC–MS/MS), was developed within the framework of Project CAO00-005, which spanned the period from 2000 to 2004. The results obtained for more than 3000 samples of virgin olive oil and organic olive oil analyzed over such a period are reported. Samples were extracted with an acetoni- trile/n-hexane mixture and cleaned up by passage through Florisil columns prior to analysis. A linear determination range for the her- bicides from 1 to 500 lg kg 1 and a correlation coeﬃcient better than 0.996 were achieved. The reproducibility, as relative standard deviation, was quite acceptable (8–11%), and so were herbicide recoveries (90–102%). The proposed method has been transferred to both public and private laboratories in the Andalusian region. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Herbicides; Olive oil; Gas chromatography; Tandem mass spectrometry; Triazines; Diuron; Norﬂurazone; Diﬂufenican; Oxyﬂuorfen 1. Introduction Crop protection products in general and herbicides in particular are essential for the subsistence of modern agri- culture. However, the use of these substances poses poten- tial hazards for humans, animals and the environment, and has thus aroused a strong interest in identifying their pres- ence in food, drinking water and soils. The triazines sima- zine and terbuthylazine, and diuron, are among the herbicides most widely used by olive growers in the Spanish region of Andalusia. The low detection levels set by regula- tory bodies and the complex nature of olive oils potentially containing herbicides have so far precluded the develop- ment of a straightforward, robust, sensitive, selective, accu- rate method for their routine screening in such an intricate type of matrix as regards identiﬁcation and quantitation. 0308-8146/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2007.01.063 Abbreviations: GC–MS/MS, gas chromatography-double fragmentation mass spectrometry; MRL, maximum residue level (or limit); GPC, gel permeation chromatography; GC-NPD, gas chromatography–nitrogen– phosphorus detection; GC–MS, gas chromatography–mass spectrometry; LC–LC-UV, coupled-column liquid chromatography with UV detection; HPLC-DAD, high-performance liquid chromatography-diode array detection; HPLC–APcI–MS, high-performance liquid chromatography– atmospheric pressure chemical ionization–mass spectrometry; HPLC–ES– MS, high-performance liquid chromatography–electrospray ionization– mass spectrometry; K ow , octanol–water partition coeﬃcient; LD 50 , lethal dose; 50% or median lethal dose; GC–ECD, gas chromatography–electron capture detection; RSD r , relative standard deviation for repeatability; RSD R , relative standard deviation for reproducibility; Rec, recovery; L- OQ, limit of quantitation. * Corresponding author. Fax: +34 957 212066. E-mail address: alberto.marinas@uco.es (A. Marinas). www.elsevier.com/locate/foodchem Food Chemistry 105 (2007) 855–861 Food Chemistry