乳粉中三聚氰胺检测方案

SILMECOPreliminary findings on melamine detection using SERStrate Background Melamine is an organic compound that increasingly has become a health concern in the 21stcentury. This was most clearly seen when it was identified as a key part in what is now knownas the 2008 Chinese milk scandal [1]. In order to boost profits some scrupleless milk producerswater down their milk. In order to pass rudimentary tests for protein content melamine isadded to watered-down milk in which nitrogen is used as an indicator. Melamine is used sinceit is very cheap and has a high nitrogen content. Figure 1： Structural formula of melamine Melamine had also been added to infant formula and animal feed to boost apparent proteincontent in these products [1]. On September 11， 2008， Xinhua News Agency in China reportedan outbreak of urinary stones in children younger than 3 years old [2]. The outbreak was linkedto the consumption of melamine in milk powder， as ingestion of melamine can lead toreproductive damage， bladder and kidney stones， and renal failure [2]. The most commontoxicity amongst studies concerning melamine is renal toxicity， which are of most concern tonephrologists [2]. The highest content of melamine found in milk products was 2.563 g/kgpowder， or 2563 ppm [2]. A total of 52，857 children were affected and received treatmentafter the outbreak [2]， with six infant deaths being reported as after-effects of the melamine intheir infant formula [3] After the 2008 scandal， the FDA reported that it had "concluded thatlevels of melamine...at or below 1 part per million (ppm) in infant formula do not raise publichealth concerns" [4]. Until 2011， milk tainted melamine was still being seized in China [3]. Experiment Preliminary tests from Silmeco have been carried out to access whether or not melamine canbe detected in milk using SERStrate in combination with a standard Raman microscope. Testswere carried out by creating two different dilution series by adding known amounts ofmelamine powder to a) water and b) milk. The tests were carried out by placing a 1 pL dropletof melamine water or milk solution onto a SERStrate chip and allowing them to dry beforeperforming Raman spectroscopy with an excitation wavelength of 780 nm. The signalacquisition from a single sample only takes a few seconds and a skilled technician would beable to perform the analysis in a couple of minutes. Bulk melamine powder was measured for comparison. The most intense peak of the powderwas observed at 675 cm and assigned to the in-plane ring breathing Il mode， which involvesan in-plane deformation of the triazine ring with the vibration of the amino nitrogen atoms.The other strong Raman band at 984 cmis the in-plane ring breathing mode l of the triazinering related to the ring nitrogen atoms. The Raman spectrum obtained from SERStrate with melamine solution in milk shows threespecific melamine peaks at 580 cm， 689 cm"and 985 cm. In the milk solution the peak at689 cmhad red-shift about 14 cmfrom that of melamine powder. On the other hand， thering breathing mode l at 985 cm had almost no shift. This observation suggests that themelamine interacts with the SERStrate surfaces through the amino groups rather than thetrazine ring. Figure 2： SERS spectra of milk and water solutions of melamine placedon SERStrate with bulk melamine powder as comparison These preliminary findings show that melamine can be detected as well as identified in milkdown to 10 ppm. Melamine in water has been detected down to concentrations of 1 ppm (notshown in Figure 2). These are orders of magnitude lower than the reported concentrationsregistered in tainted milk formula (5000 ppm) and on the level of the FDA's maximumrecommended levels (1ppm). Conclusion Although this has only been a very rudimentary study we have shown that SERStrate fromSilmeco is a viable method to quickly screen large quantities of milk for melaminecontamination at relevant detection levels. Optimization in sample acquisition from the milk(ie. centrifusion) could be used to further improve the already promising results. For more information please contact Silmeco at info@Silmeco.com References [1] M. McMahon， "What is Melamine?，" 10 June 2014. [Online]. Available： http：//www.wisegeek.org/what-ismelamine.htm.[Accessed 22 June 2014]. [2] A. Kai-ching Hau，"Melamine Toxicity and the Kidney，" 2009. [3] Helena Hong， "China seizes 26 tons of melamine-tainted milk，" CNN， 27 April 2011. [Online]. Available：http：//edition.cnn.com/2011/WORLD/asiapcf/04/27/china.tainted.milk/. [Accessed 22 June 2014]. [4]"Melamine Contamination in China，" FDA， 5 January 2009.[Online]. Available： http：//www.fda.gov/NewsEvents/PublicHealthFocus/ucm179005.htm. [Accessed 22 June 2014].