Development and Optimization of a SERS Method for On-site Determination of Nitrite in Foods and Water
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Development and Optimization of a SERS Method for On-site Determination of Nitrite in Foods and Water Pinyi Ma & Fanghui Liang & Xinpei Li & Qingqing Yang & Di Wang & Daqian Song & Dejiang Gao & Xinghua Wang
Received: 26 November 2013 / Accepted: 17 February 2014 # Springer Science+Business Media New York 2014
Abstract A rapid, sensitive, and selective detection method of nitrite in foods and water was established by surface-enhanced Raman spectroscopy (SERS) based on the diazo reaction of nitrite with p-nitroaniline and 1-naphthylamine in acidic solution. The azo dye (4-(4-nitrophenyldiazenyl)naphthalene-1aminium, NNA), which was derived from the diazo reaction, was determined by SERS using citrate-coated silver nanoparticles (AgNPs) as SERS substrates. The concentrations of nitrite in samples were finally calculated from the intensities of SERS signals generated by NNA in the testing solutions. By using the present method combined with a portable miniature Raman spectrometer, on-site determination of nitrite could be performed easily and efficiently. The effects of several experimental parameters on the intensity of SERS signals, such as the volume of AgNP solution and the mixing time of AgNPs and NNA, were investigated. The linear range of the method was 0.1–10.0 mg L−1. The limits of detection (LODs) were 0.01, 0.03, and 0.05 mg L−1 at 720, 1,459, and 1,609 cm−1, respectively. The method was applied to the determination of nitrite in real food and water samples, with recoveries in the
P. Ma : X. Li : Q. Yang : D. Wang : D. Song : X. Wang (*) College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012, People’s Republic of China e-mail: [email protected] F. Liang Department of Pharmacy, Changchun Medical College, Jilin Street 6177, Changchun 130031, People’s Republic of China D. Gao Changchun Jilin University Little Swan Instruments Co., Ltd., Chuangxin Road 1203, Changchun 130012, People’s Republic of China
range of 86.9–103.4 % and relative standard deviations (RSDs) less than 9.64 %. Keywords Nitrite . On-site determination . Food . Surface-enhanced Raman spectroscopy (SERS) . Silver nanoparticles (AgNPs) . Diazo reaction
Introduction Nitrite is an essential intermediate in the biological nitrogen cycle. However, nitrite is undesirable in water and foods owing to its toxicity. Nitrite can promote the irreversible oxidization of hemoglobin and reduce the blood capacity to transport oxygen (Wang et al. 2009). Also, there is a potential for nitrite to be metabolized to carcinogenic N-nitroso compounds in human body (Dunham et al. 1995; Mirvish 1995). The nitrogen fertilizers used in agriculture have main roles in the production of nitrite in the water environment (Gopalan et al. 2010). Nitrite is usually added to processed meat products as its sodium or potassium salt to retain the red color and flavor of fresh meat (Pourreza et al. 2012; Unnikrishnan et al. 2013). Nowadays, the limits of nitrite in foods and water were specified by government authorities of many countries to avoid the ad
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