Analytical Methods Validation of an ultra-performance liquid chromatography-tandem mass spectrometry method for determination of ractopamine: Application to residue depletion study in swine Yichun Dong b,1 , Xi Xia a,1 , Xia Wang b , Shuangyang Ding a , Xiaowei Li a , Suxia Zhang a , Haiyang Jiang a , Jinfeng Liu a , Jiancheng Li a , Zhongze Feng b , Ni Ye b , Mingxia Zhou b , Jianzhong Shen a,⇑ a Department of Pharmacology and Toxicology, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China b China Institute of Veterinary Drug Control, Beijing 100081, China article info Article history: Received 6 May 2010 Received in revised form 25 October 2010 Accepted 31 December 2010 Available online 8 January 2011 Keywords: Ractopamine Ultra-performance liquid chromatography Tandem mass spectrometry Swine Residue depletion abstract A sensitive and reliable method was developed and validated for the analysis of ractopamine in swine tissues. The sample preparation procedure was based on hydrolysis overnight, extraction with ethyl ace- tate, and solid-phase extraction cleanup. The target compound was determined by ultra-performance liquid chromatography coupled with tandem mass spectrometry. The average recoveries ranged between 93.3% and 106.5%, with relative standard deviations of 7.2–12.8%. The detection and quantification limits were 0.2 and 0.5 lg/kg, respectively. The depletion profile of ractopamine was studied in healthy pigs after oral administration of feed containing 20 mg/kg ractopamine for 30 consecutive days. Ractopamine residues were still detected 11 days post-medication in all tissues examined with the exception of mus- cle. The highest ractopamine level was found in lung tissue. The developed method has been successfully applied to the depletion study of ractopamine in swine tissues. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Ractopamine (RCT) is a phenethanolamine with b-adrenergic agonist properties and has been approved as a feed additive for swine and cattle in the United States and some other countries. It was used to improve protein-to-fat ratio and produce leaner carcassess (Elliott et al., 1993; Engeseth et al., 1992; Sainz, Kim, Dunshea, & Campbell, 1993). However, RCT is not licensed for ani- mal production in China and Europe due to the potential risk to consumers for adverse cardiovascular and central nervous system effects (Brambilla et al., 2000). Concerns surrounding food safety and international trade have necessitated the development of ana- lytical methods for determination of RCT and required the residue depletion study to be conducted. A number of methods, in most cases gas chromatography (GC) or liquid chromatography (LC) coupled to mass spectrometry (MS), are currently available for the analysis of ractopamine in a variety matrices. The matrix that have been examined included muscle (Antignac, Marchand, Le Bizec, & Andre, 2002; Kootstra et al., 2005; Shao et al., 2009; Shishani, Chai, Jamokha, Aznar, & Hoffman, 2003), liver (Antignac et al., 2002; Blanca et al., 2005; Churchwell et al., 2002; Fesser et al., 2005; Moragues & Igualada, 2009; Shao et al., 2009; Thompson et al., 2008; Wang, Li, Zhang, & Shen, 2006; Williams, Churchwell, & Doerge, 2004), kidney (Antignac et al., 2002; Shao et al., 2009), lung (Antignac et al., 2002), urine (Antignac et al., 2002; Blanca et al., 2005; Dickson, McNeil, Lee, & Fesser, 2005; Moragues et al., 2009; Nielen et al., 2008; Thompson et al., 2008; Van Hoof et al., 2005), retina (Anti- gnac et al., 2002; Bocca, Fiori, Cartoni, & Brambilla, 2003; Church- well et al., 2002; Fesser et al., 2005; Williams et al., 2004), hair and feed (Nielen et al., 2008). Residue depletion study of ractopamine in swine tissues has also been reported (Qiang et al., 2007; World Health Organization/Food and Agriculture Organization of the Uni- ted Nations, 2004). Nevertheless, these studies merely focused on the residues of RCT in muscle, liver, kidney, and fat. To our knowl- edge, no report exists describing the residue depletion of ractop- amine in tissues like lung or stomach. The stomach and intestine tissues are also part of food sources in some countries and the depletion data in these tissues would be helpful for safety evaluation. In this paper, a sensitive and reliable analytical method using ultra-performance liquid chromatography-tandem mass spec- trometry (UPLC-MS/MS) has been developed and validated for the determination of ractopamine in swine tissues. The proposed method was successfully applied to monitor residue depletion of ractopamine in swine tissues (muscle, liver, kidney, lung, stomach, 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.12.138 ⇑ Corresponding author. Tel.: +86 10 62732803, fax: +86 10 62731032. E-mail address: sjz@cau.edu.cn (J. Shen). 1 These authors contributed equally to this work. Food Chemistry 127 (2011) 327–332 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem