SERS Detection of Insecticide Amitraz Residue in Milk Based on Au@Ag Core-Shell Nanoparticles
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SERS Detection of Insecticide Amitraz Residue in Milk Based on Au@Ag Core-Shell Nanoparticles Pan Li 1 & Yuanjie Teng 1
&
Yonghui Nie 1 & Wenhan Liu 1
Received: 16 February 2017 / Accepted: 9 June 2017 # Springer Science+Business Media, LLC 2017
Abstract A simple, rapid, and environmentally friendly surface-enhanced Raman scattering (SERS) method was developed for the determination of trace amitraz in milk with the use of silver-coated gold nanoparticles (Au@Ag NPs) as enhancing reagent. The normal Raman and SERS spectra of amitraz were analyzed, and the peaks were assigned by density functional theory. The morphology of Au@Ag NPs was characterized and confirmed by transmission electron microscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. The SERS effects of Au@Ag NPs were investigated, including the types of solvents for dissolving amitraz, the volume ratio of the Au@Ag NPs and amitraz, and the concentration of aggregating agent (NaCl) for aggregate Au@Ag NPs. Results show that ethanol exerts the least interference on the SERS spectrum of amitraz and is more environmentally sound than methanol. The strongest SERS signal appeared when the volume ratio of Au@Ag NPs and amitraz was 2:1. Moreover, the strongest SERS signals appeared when the concentration of NaCl was 0.025 mol L−1 because of appropriate aggregation. Under the optimum conditions, the concentration of amitraz presents a good linear relationship with Raman intensity (723 cm−1) with a linear range of 9.77 × 10−4~2.93 × 10−2 g L−1. The detected recoveries of amitraz in milk were between 81.7 and 100.5% with a relative standard deviation (RSD) of 2.61~5.51%.
* Yuanjie Teng [email protected] * Wenhan Liu [email protected] 1
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310032, China
Keywords Amitraz . Au@Ag core-shell nanoparticles . Surface-enhanced Raman scattering . Milk
Introduction Amitraz, an effective and universal insecticide and acaricide, is widely used in agriculture and gardening (Vucinic et al. 2007). However, amitraz and its metabolites, which are directly taken in or absorbed through the skin because of its transitivity, cause poisoning (Osano et al. 2002). According to the European Food Safety Authority (EFSA)’s standard, the maximum residue level for amitraz and its metabolites in milk is set to 0.01 mg kg−1 (EFSA 2016). Nowadays, the popular amitraz detection methods are gas chromatography, high performance liquid chromatography, and liquid chromatographymass spectrometry (Jimenez et al. 2004; Skerl et al. 2010; Gao et al. 2016). Although chromatography methods have high sensitivity, good accuracy, and ideal repeatability, they usually need complex and time-consuming pretreatment process. Moreover, few papers report on amitraz detection for milk and mostly focus on honey and fruits samples (Wu et al. 2015). Therefore, establishing a simple pretreatment and high efficiency detection method for am
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