Talanta 83 (2010) 171–177 Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Analysis of sediment-associated insecticides using ultrasound assisted microwave extraction and gas chromatography–mass spectrometry Huizhen Li a,b , Yanli Wei a,b , Jing You a,∗ , Michael J. Lydy c a State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China b Graduate School of the Chinese Academy of Sciences, Beijing 100049, China c Fisheries and Illinois Aquaculture Center and Department of Zoology, 171 Life Science II, Southern Illinois University, Carbondale, Il 62901, USA article info Article history: Received 22 June 2010 Received in revised form 31 August 2010 Accepted 3 September 2010 Available online 15 September 2010 Keywords: Ultrasound assisted microwave extraction (UAME) Organophosphate insecticides Pyrethroid insecticides Sediment abstract An ultrasound assisted microwave extraction (UAME) method was developed to simultaneously extract five organophosphate (OP) and eight pyrethroid insecticides from sediment. The optimized UAME condi- tions were to use 100 ml of a mixture of hexane and acetone (1:1, v/v) solution as the extraction solvents, and extraction time, microwave and ultrasonic power settings of 6 min, 100 W and 50 W, respectively. Extracts were cleaned using solid phase extraction and analyzed by gas chromatography–mass spectrom- etry in negative chemical ionization mode and quantification was based on matrix-matched standard solutions along with internal standard calibration. At the spiked concentrations of 1, 5 and 20 ng/g dry weight (dw), recoveries of OPs were 77.6–122%, 65.2–128% and 75.6–141% with relative standard deviations (RSDs) of 10.6–18.1%, 3.1–12.5% and 8.0–35.3%, respectively, while recoveries of pyrethroids were 78.0–101%, 76.4–104% and 71.0–99.5% with RSDs of 10.3–23.5%, 4.7–17.6% and 8.8–18.7%, respec- tively. Method detection limits ranged from 0.31 to 0.45 ng/g dw for the OP insecticides and from 0.27 to 0.70 ng/g dw for the pyrethroid insecticides. The newly developed UAME method was validated by comparing it to Soxhlet and sonication extraction methods. Better recoveries were achieved for most OPs by the novel UAME method, whereas there was no significant difference in recoveries for most of the pyrethroids. Finally, the UAME method was used to quantify the target insecticides in field-contaminated sediment samples which were collected in Guangzhou, China. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Organophosphate (OP) and pyrethroid insecticides are currently used for pest control in both agricultural and urban areas in China, and their residues are transported to the aquatic environment through runoff events [1]. These insecticides strongly bind to sedi- ment; therefore, their degradation rates are reduced, and as a result, sediment becomes a reservoir for these compounds, and analysis of sediment samples for insecticides is an effective method to quantify insecticide contamination [2]. Due to the strong binding between insecticides and sediment organic carbon (OC), it generally requires an exhaustive extraction method to separate analytes from the complicated matrix com- ponents. Different methods have been developed to extract OP and pyrethroid insecticides from sediment [3–11]. Since its intro- duction in 1879, Soxhlet extraction is still widely used because of its acceptable extraction efficiency and low cost [3]. However, the lengthy extraction time (from 4 to 48 h) which may lead to ∗ Corresponding author. Tel.: +86 20 8529 1497; fax: +86 20 8529 0706. E-mail address: youjing@gig.ac.cn (J. You). potential loss of analytes as well as the requirement of large extraction solvent volumes stimulated studies examining alterna- tive extraction techniques. Sonication extraction [4,5], supercritical fluid extraction (SFE) [6], microwave-assisted extraction (MAE) [7,8] and accelerated solvent extraction (ASE) [9–11] have been employed to extract insecticides from sediment. Although these alternative methods greatly reduced extraction time and solvent usage, most of them, including SFE, pressurized-MAE and ASE, require operation under high pressure which requires sophisti- cated and expensive instruments. In contrast, sonication equipment is relatively inexpensive, and has been shown to be an effective technique to extract organic con- taminants from solid samples [4,5]. In addition to sonication, MAE operated under atmospheric pressure is another relatively low cost alternative extraction method [12,13]. Since its first introduction in 1986 [14], MAE has been used for extracting organic pollutants from various environmental matrices [12,13,15]. Two types of MAE have been developed, namely focused MAE (FMAE) and pressurized MAE (PMAE), corresponding to an open-style system under atmospheric pressure and a closed-style system under a certain pressure, respec- tively [16]. The PMAE method has been extensively used since it can simultaneously extract multiple samples, extraction time is exten- 0039-9140/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2010.09.002