title: Detection of melamine in milk by surface-enhanced Raman spectroscopy coupled with magnetic and Raman-labeled nanoparticles.
abstract: A new method based on surface-enhanced Raman spectroscopy (SERS) has been developed for sensitive and rapid detection of melamine. Spherical magnetic-core gold-shell nanoparticles (AuNPs) and rod-shaped gold nanoparticles (nanorods) labeled with a Raman-active compound were used to form a complex with the melamine molecules. 5,5'-Dithiobis(2-nitrobenzoic acid) was used as Raman-active compound because it is readily adsorbed by a gold nanoparticle surface forming a self-assembled monolayer (SAM) and has strong Raman scattering at 1330 cm(-1), because of the symmetric NO(2) stretch. The calibration curve was obtained by plotting Raman band area at 1330 cm(-1) against melamine concentration. A linear relationship was obtained with a high determination coefficient (R(2)=0.997). The method was validated for linearity, sensitivity, precision (intra-day and inter-day repeatability), and recovery. In the model system, the limits of detection (LOD) and quantification (LOQ) were 0.38 and 1.27 mg L(-1), respectively. For melamine-spiked milk samples, LOD and LOQ values were 0.39 mg L(-1) and 1.30 mg L(-1), respectively. Intra and inter-day precision were 3.73 and 4.94 %, respectively. This method was applied to samples of skimmed milk that had been spiked with melamine at different concentrations. The recovery of the method was 95-109 % in the concentration range 2-15 mg L(-1), and average RSD was 1.71 %. Total analysis time was less than 15 min.
authors.affiliation: Department of Food Engineering, Faculty of Engineering, Hacettepe University, 06800 Beytepe, Ankara, Turkey.
authors.forename: Nazife Nur
authors.initials: NN
authors.lastname: Yazgan
authors.forename: Ismail Hakkı
authors.initials: IH
authors.lastname: Boyacı
authors.forename: Ali
authors.initials: A
authors.lastname: Topcu
authors.forename: Uğur
authors.initials: U
authors.lastname: Tamer
mesh_terms: D000818:Animals; D006046:Gold / Q000737:chemistry*; D057230:Limit of Detection; D053768:Metal Nanoparticles; D046529:Microscopy, Electron, Transmission; D008892:Milk / Q000737:chemistry*; D015203:Reproducibility of Results; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014227:Triazines / Q000737:chemistry*
chemical_list: D014227:Triazines; D006046:Gold; C011907:melamine