Milking the Melamine MessDetecting melamine in food products using LC-MS-MSDipankar Ghosh The recent discovery of melamine in infant formula manufactured and sold in China has revitalized concerns about the possible presence of the chemical in other products, particularly processed foods such as cookies and candy that contain milk ingredients.1-3 Government agencies and food manufacturers alike are searching for analytical solutions to reassure the public that this contaminant can be detected and prevented from entering the food supply chain. Melamine by itself is nontoxic in low doses, but when combined with cyanuric acid, has been linked to kidney problems for both humans and animals. Melamine is an industrial-grade chemical commonly used in the manufacturing of plastics, flame retardants and other products. The chemical has a high nitrogen content that makes it possible for unscrupulous food manufacturers to boost the protein content of food products, which can deceive certain quality-control checks that are standard in the food industry. As such, the international food manufacturing industry is taking the detection of melamine very seriously by developing analytical methods to determine the presence of the contaminant in the complex sample matrices typical of food products. Regulatory agencies respond
Melamine is not approved for use in food or animal feed. Recently, the U.S. Food and Drug Administration (FDA) announced that eating a very tiny amount of melamine—2.5 parts per million—would not raise health concerns, even if a person ate food that was tainted with the chemical daily. In spite of that pronouncement, officials stressed the scientific assessment does not mean that U.S. authorities will tolerate any melamine that is deliberately added to foods. Officials also said that infant formula sold to U.S. consumers must be completely free of melamine.4 "If products are adulterated because they contain melamine, [authorities] will take appropriate actions to prevent the products from entering commerce," the FDA said in a statement. The agency said the 2.5 parts-per-million standard was intended to address situations where the chemical accidentally comes into contact with food, such as where it is used for industrial purposes in a factory that makes food products. In Europe, the European Commission Joint Research Centre’s Institute for Reference Materials and Measurements is gathering information and reviewing methods to detect melamine in food and feed products to address concerns about possible melamine contamination in products on the European market.5 Although the EU does not import milk or other dairy produce from China, processed foods such as cookies and chocolates might contain traces of milk powder. The European Commission recently decided that all products originating from China and containing more than 15% of milk as an ingredient must be checked for the presence of melamine. In order to protect the European citizens, products containing more than 2.5 mg/kg are to be immediately destroyed. The United Kingdom’s Food Standards Agency reports that local authorities at seaports and airports carry out regular checks on imported food to ensure that it meets strict EU food safety requirements. The Food Standards Agency works with port health authorities and local authorities to ensure EU controls are strictly enforced. According to the agency, there has been a longstanding ban on the import of milk and other products of animal origin from China, as controls on the food industry in China do not meet the very strict requirements set in the EU. Detection techniques for melamine
Detecting melamine in food requires methods that are sensitive and accurate enough to detect very low levels of contaminants in complex samples typical of most food products. One of the preferred methods for detecting melamine in food products is LC-MS-MS (liquid chromatography coupled with tandem mass spectrometry) analysis. After melamine was discovered in pet food last year, the FDA developed a method for detecting melamine in catfish.6 Laboratory Information Bulletin No. 4396 states, “Because animals may eat food contaminated with melamine residues, there is a need for analytical methods to determine melamine residues that may be present in animal tissues.” To develop this bulletin, the FDA used the Thermo Scientific TSQ Quantum triple quadrupole mass spectrometer (Thermo Fisher Scientific, San Jose, CA) coupled with the company’s Surveyor LC-MS pump and autosampler. The method showed that the instrumentation detected melamine at levels of 10 parts per billion in catfish extract, exceeding the agency’s requirements (Figure 1).
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| Figure 1: Chromatogram of cyanuric acid and melamine spiked into catfish matrix, at a level of 50 ppb for cyanuric acid and 10 ppb for melamine. | In a separate development, the National Center for Food Safety and Technology (NCFST) needed to quickly learn more about the effects of food processing on the chemical to learn how to accurately detect the presence of melamine in food. In July 2007, the NCFST began using Thermo Scientific’s TSQ Quantum Ultra triple stage quadrupole system coupled with the Accela high-speed chromatography system to develop its LC-MS-MS method to monitor melamine and its hydrolytic products in processed foods.7 The TSQ system enables highly selective reaction monitoring (H-SRM) performance, which facilitates the quick and efficient analysis of complex samples such as animal tissue. This LC-MS-MS solution has yielded accuracy and precision values for this method that were well within the guidelines of the FDA for analytical method development and validation. Currently the LC-MS-MS method developed by the NCFST is being used as a reference by the laboratories under Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) in China to develop a similar LC-MS-MS method using TSQ Quantum systems for the detection of melamine in milk and infant formula. Conclusion
Both government agencies and food manufacturers are working to establish detection methods for melamine in both internal and official quality-control checks. LC-MS-MS is a powerful technique for the global food industry to use as they work towards compliance with current regulations regarding the presence of melamine in food products for both humans and animals, building on the lessons learned during the pet food recall of 2007, as well as the infant formula and milk product recalls of this year. References
1. World Health Organization. Available at http://www.who.int/foodsafety/fs_management/infosan_events/en/index.html. Accessed 10 October 2008.
2. Dutch food authority finds melamine in cookies. Available at http://www.aol.com.au/news/story/Dutch-food-authority-finds-melamine-in-cookies/1061301/index.html. Accessed 10 October 2008.
3. Melamine-Tainted Candy Found In CT. Available at http://www.wfsb.com/health/17599817/detail.html. Accessed 10 October 2008.
4. Tiny bit of melamine in food is OK, experts say. Associated Press. http://www.msnbc.msn.com/id/27009289/from/ET/. Accessed 10 October 2008
5. Melamine contamination: JRC reviews detection methods. Available at http://ec.europa.eu/dgs/jrc/index.cfm?id=2820&obj_id=242&dt_code=HLN&lang=en. Accessed 10 October 2008.
6. Andersen, Wendy C.; Turnipseed, Sherri B.; Karbiwnyk, Christine M.; and Madson, Mark R. Determination of Melamine Residues in Catfish Tissue by Triple Quadrupole LC-MS-MS with HILIC Chromatography. Laboratory Information Bulletin No. 4396. U.S. Food and Drug Administration. May 2007.
7. Varelis, Peter; Beck, Jonathan; Wang, Kefei; and Ghosh, Dipankar. Analysis of Melamine and Cyanuric Acid in Food Matrices by LC-MS/MS. Thermo Fisher Scientific Application Note No. 424. 2008. Dipankar Ghosh is strategic marketing manager, environment & food safety for Thermo Fisher Scientific. He may be contacted at ChromatographyTechniques@advantagemedia.com.
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