Analytica Chimica Acta 571 (2006) 1–11 Optimization of LC–MS/MS using triple quadrupole mass analyzer for the simultaneous analysis of carbosulfan and its main metabolites in oranges Carla Soler a,∗ , Brett Hamilton b , Ambrose Furey b , Kevin J. James b , Jordi Ma ˜ nes a , Yolanda Pic´ o a a Laboratori de Bromatologia i Toxicologia, Facultat de Farm` acia, Universitat de Val` encia, Av. Vicent Andr´ es Estell´ es s/n, 46100 Burjassot, Val` encia, Spain b PROTEOBIO Department of Chemistry, Mass Spectrometry Centre for Proteomics and Biotoxin Research, Cork Institute of Technology, Bishopstown, Cork, Ireland Received 18 March 2006; received in revised form 11 April 2006; accepted 13 April 2006 Available online 27 April 2006 Abstract This paper describes an analytical method involving a simple solvent extraction for the simultaneous liquid chromatography coupled to quadrupole tandem mass spectrometry (LC–MS/MS) determination of carbosulfan, its most toxic metabolite –carbofuran –, and its other main metabo- lites – 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxy-7-phenolcarbofuran, 3-keto-7-phenolcarbofuran, 7-phenolcarbofuran and dibutylamine – in oranges. Chromatography was performed on a Zorbax Bonus-RP (150 mm × 2.1 mm, 5 m). The mobile phase was a ternary gradient water–methanol–acetonitrile with 1.0 mM ammonium acetate at flow rate of 0.2 ml min -1 . The LC separation and MS/MS optimization were studied to select the most appropriate operating conditions. The method developed has also been validated. The limits of quantification (LOQs) were from 1 g kg -1 for carbofuran to 10 g kg -1 for 3-keto-7-phenolcarbofuran. Extracts spiked with carbosulfan and its metabolites, at LOQ level, yielded average recoveries in the range 60–94%, with relative standard deviations (R.S.D.s) less than 15%. Calibration curves for carbosulfan and its metabolites (range LOQ–1000LOQ) were linear, with coefficients of correlations better than 0.990. The method was successfully applied to establish the primary degradation products in oranges treated with carbosulfan. The LC–MS/MS method developed is simple, rapid, and suitable for the quantification and confirmation of carbosulfan and seven of its main metabolites in orange at levels lower than 10 g kg -1 . © 2006 Elsevier B.V. All rights reserved. Keywords: Liquid chromatography–tandem mass spectrometry; Triple quadrupole; Food; Fruits; Pesticides; Metabolites; Carbamates 1. Introduction Carbamate pesticides have great significance in pest con- trol. They are increasingly used, instead of organochlorine and organophosphorus pesticides, due to their broad spectrum of biological activity, and lower environmental persistence [1]. Their toxicity is mediated through the inhibition of the acetyl- cholinesterase (AChE) [2]. After the application of carbamates for crop protection, they can be transformed into several metabo- lites [3], which can be more toxic and persistent than the parent compound [4,5]. For this reason, the importance of the presence ∗ Corresponding author. Tel.: +34 963 544 958; fax: 34 963 544 954. E-mail address: carla.soler@uv.es (C. Soler). not only of carbamates but also of their metabolites in food must be considered. This concern has been reflected by the European Union (EU) in the maximum residues limits (MRLs) established for pesticide residues in a variety of agricultural products [6], and the directives that remark the necessity to assess the environ- mental impact of relevant degradation products and to identify these compounds in routine analysis [7]. The carbamate insecticide carbosulfan, that is systemic and characterized by a high liposolubility being extremely toxic to mammals, breaks down into carbofuran, 3-hydroxy carbofuran and 3-keto carbofuran under field conditions, all of them toxic compounds. This is a special case, in which a less toxic pesticide (carbosulfan, DL 50 250 mg kg -1 for rats) is transformed in a more toxic one (carbofuran, DL 50 8 mg kg -1 for rats) after its application. Carbosulfan is considered as a pro-insecticide, in 0003-2670/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2006.04.033