Analytical Methods Pyrethroid residue determination in organic and conventional vegetables using liquid-solid extraction coupled with magnetic solid phase extraction based on polystyrene-coated magnetic nanoparticles Xi Yu, Hongshun Yang ⇑ Food Science and Technology Programme, c/o Department of Chemistry, National University of Singapore, 117543 Singapore, Singapore National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Suzhou, Jiangsu 215123, PR China article info Article history: Received 26 September 2015 Received in revised form 24 May 2016 Accepted 27 August 2016 Available online 29 August 2016 Keywords: Vegetables Organic Nanoparticles HPLC Pyrethroids Extraction technique abstract A detection method using polystyrene-coated magnetic nanoparticles based extraction technique cou- pled to HPLC was developed for trace amount of pyrethroids residue detection in vegetable matrixes. The recoveries for five kinds of commonly used pyrethroids were in the range of 91.6%–116.2%. The sensitivity and precision of the method were satisfactory with the limits of detection and limits of quan- tification in the range of 0.0200–0.0392 ng g À1 and 0.072–0.128 ng g À1 , respectively. The intra-day and inter-day relative standard deviations for the recoveries of the analytes were lower than 6.8% and 10.7%, respectively. The nanoparticles can be washed and recycled after use. The results indicate that the developed method was efficient, fast, economical and environmentally friendly. The method was successfully applied to detect the pyrethroids residue in ten pairs of commonly consumed organic and conventional fresh vegetables in Singapore. Pyrethroids residue was detected in four kinds of conven- tional vegetables and one kind of organic vegetable. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Vegetables are a very important category of food materials due to their high contents of dietary fiber, vitamins, antioxidants, min- erals and diverse beneficial phytochemicals (Demmig-Adams & Adams, 2002; Ren et al., 2014). Regular consumption of vegetables brings great health beneficial effect for human beings by enhancing human immunity and preventing diseases such as diabetes, consti- pation, cardiovascular diseases, and even colon cancer (Fu et al., 2015; Murphy et al., 2012; Ren, Perera, & Hemar, 2012). However, pesticides residue in vegetables, especially leafy vegetables has been a concern due to the high reliance on the synthetic pesticides in order to boost crop yields (Wilkowska & Biziuk, 2011). Long term over dose exposure to synthetic pesticides can lead to severe health problems since most of these chemicals are teratogenetic or even carcinogenic (Walorczyk et al., 2013). Even worse, they usually cannot be metabolised thoroughly in short term in human body and will thus be accumulated in the form of prototype or metabolite to a dangerous level (Bøhn et al., 2014). Pyrethroids are widely applied synthetic pesticides derived from naturally occurred chrysanthemum esters (Radford, Panuwet, Hunter, Barr, & Ryan, 2014). Although pyrethroids are mainly applied to crops, they can be accumulated in soil and spread to every link of food production and every part of our daily diet via contamination (Bayen, Zhang, Desai, Ooi, & Kelly, 2013; Farajzadeh, Khoshmaram, & Nabil, 2014; Yu, Sun, Jiang, Gao et al., 2012). Moreover, according to vast research, the contamina- tion of pyrethroids can diffuse to the environment through water circulation such as irrigation and rainfall (Bayen, Yi, Segovia, Zhou, & Kelly, 2014; Bayen et al., 2014; Fernández-Ramos, Šatíns ky ´ , & Solich, 2014). Therefore, it is important to develop accurate and effective technique to detect pyrethroids residue in various matrixes, especially vegetables (Zhu et al., 2014). Many efforts have been paid to determine pyrethroids in food matrixes since they started to be widely used (Ling & Huang, 1995; Watanabe & Baba, 2015). Due to the complexity of the food matrixes, in the determination the most affective step is the pre- concentration since it is decisive in achieving high accuracy and low limit of detection (Bidari, Ganjali, Norouzi, Hosseini, & Assadi, 2011). A competitive enzyme-linked immunosorbent method was developed to extract pyrethroids residue from lettuce and peach (Park et al., 2004) then a clean-up routine using solid phase extraction cartridges to facilitate analysis of pyrethroids http://dx.doi.org/10.1016/j.foodchem.2016.08.115 0308-8146/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Food Science and Technology Programme, c/o Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 Singapore, Singapore. E-mail address: chmynghs@nus.edu.sg (H. Yang). Food Chemistry 217 (2017) 303–310 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem