Potential of SERS for rapid detection of melamine and cyanuric acid extracted from milk

Abstract

Melamine, a nitrogen-rich chemical, was implicated in the pet and human food recalls in 2007 and in the global food safety scares in 2008 involving milk and other milk-derived products. In this study, we investigated the feasibility of using surface-enhanced Raman spectroscopy (SERS) coupled with SERS-active gold substrates for rapid detection of trace amounts of melamine and its analogue (that is, cyanuric acid) in liquid milk. Raman signals of tested samples were significantly enhanced by SERS. The identification limit for SERS using gold substrate can reach 2 ppm of melamine in liquid milk. Partial least squares (PLS) models were established for the quantification of melamine in liquid milk by SERS: R = 0.90, RMSEP = 1.48 9 10 -5 . Our results demonstrate that rapid detection of melamine in milk can be achieved by SERS; while detection of cyanuric acid in milk remains a challenging task due to rapid enol-keto tautomerism of cyanuric acid. The SERS method is faster and simpler than other traditional methods, and requires minimum sample preparation. These results demonstrate that SERS could be used to detect food contaminants such as melamine in foods and food ingredients quickly and accurately.

Rapid detection of melamine with 4-mercaptopyridine-modified gold nanoparticles by surface-enhanced Raman scattering

“…The enhancement associated with SERSup to 10 14 times [23]-is widely attributed to two primary mechanisms: the short-range chemical effect and the longrange classical electromagnetic effect. Recently, several groups have reported the determination of melamine using SERS by detecting the signal from melamine directly with roughened gold substrates [24], silver colloid substrate [25] or other SERS substrates [26][27][28]. However, the signal from melamine itself is relatively weak, and the detection limits of these direct sensing methods are unsatisfactory (most are more than 10 ppb).…”

Application of surface enhanced Raman spectroscopy for analyses of restricted sulfa drugs

“…The chemical enhancement theory attributes the SERS enhancement effects to charge-transfer between adsorbed analyte molecules and roughened metal surface. Although SERS enhancement effect is a rather complicated phenomenon with many questions unresolved, SERS has a great promise as an analytical method in detecting and determining trace amounts of toxicant or prohibited drugs as indicated in some research reports over a diverse fields [14][15][16].…”

Common milk adulteration and their detection techniques

“…Both the European Commission and the United States Food and Drug Administration (USFDA) have applied a maximum acceptable limit of 2.5 mg/kg for melamine in imported foods, and 1 mg/kg in infant formula (Lawley, 2013). This was later adopted by United Nation's food standard body, Codex Alimentarius Commission through a new rulings in 2010 (Domingo, Tirelli, Nunes, Guerreiro, & Pinto, 2014;FAO, 2010;B. Liu, Lin, & Li, 2010).…”