Detection of melamine in milk by surface-enhanced Raman spectroscopy coupled with magnetic and Raman-labeled nanoparticles

• Published in: Analytical and bioanalytical chemistry Vol. 403; no. 7; pp. 2009 - 2017
• Main Authors: Yazgan, Nazife Nur, Boyacı, İsmail Hakkı, Topcu, Ali, Tamer, Uğur
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2012; Springer
• Subjects: Analysis; Analytical Chemistry; Animals; Biochemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Food Science; Gold; Gold - chemistry; Laboratory Medicine; Limit of Detection; Linearity; Melamine; Metal Nanoparticles; Microscopy, Electron, Transmission; Milk; Milk - chemistry; Monitoring/Environmental Analysis; Monomolecular films; Nanoparticles; Nanorods; Original Paper; Raman spectroscopy; Recovery; Reproducibility of Results; Spectroscopy; Spectrum Analysis, Raman - methods; Triazines - chemistry; Melamine; Surface-enhanced Raman spectroscopy; Magnetic nanoparticles; Milk
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-012-5971-1

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. Figure 1 Melamine acts as a cross linker molecule between the magnetic AuNPs and Raman-labeled nanorods