FOOD ANALYSIS

ANDRÉ SCHREIBER1*, FANNY FU2, SU-HSIANG TSENG3 *Corresponding author 1. AB SCIEX, 71 Four Valley Drive, Concord, Ontario, L4K 4V8, Canada 2. AB SCIEX, Taiwan 3. Food and Drug Administration, Ministry of Health and Welfare, Taiwan

Andrè Schreiber

LC-MS/MS analysis of emerging food contaminants Quantitation and identification of dicyandiamide in milk and other protein-rich foods

KEYWORDS: dicyandiamide, melamine, milk, food, quantitation, LC-MS/MS

This paper describes an analytical workflow for the detection of dicyandiamide and other nitrogen rich Abstractcompounds in milk and other protein-rich foods. Food samples were extracted using a simple liquid extraction followed by extensive dilution to minimize possible ion suppression effects ionisation. Liquid chromatography (LC) separation used a normal phase gradient on a hydrophilic interaction chromatography (HILIC) column followed by tandem mass spectrometry (MS/MS) detection. Two selective multiple reaction monitoring (MRM) transitions were detected for each target analyte using the ratio of quantifier and qualifier ion for identification. The sensitivity of the LC-MS/MS system allowed the quantitation of dicyandiamide and other nitrogen rich compounds in milk and other protein-rich foods with limits of quantitation down to low μg/kg. Dicyandiamide was quantified in milk with a limit of quantitation of less than 1μg/kg after 200x dilution of the sample extract. Recovery was determined to be 97.3% with a relative standard deviation of 3.66%.?

INTRODUCTION

Recent issues with adulteration of food using nitrogen rich compounds to make the protein content of food appear higher than the actual value highlighted the need for both food manufacturers and regulatory agencies to utilize fast and accurate analytical techniques to proactively ensure product safety. In 2007, melamine and cyanuric acid in wheat gluten Figure 1. Potential adulterants (non-protein nitrogen sources), including added to pet food caused renal failure and sickened melamine, cyanuric acid, ammelide, ammeline, cyromazine, dicyandiamide, and killed large numbers of cats and dogs. In 2008, urea, biuret, triuret, amidinourea, (top left to bottom right) Chinese authorities discovered the adulteration of milk and infant formula with melamine by several Chinese producers. There were hundreds of thousands serious concern. Analytical methods to detect potential of victims and six confirmed deaths in China, as well as adulterants (non-protein nitrogen sources), including product recalls in many countries. (1-4) amidinourea, ammelide, ammeline, biuret, cyanuric acid, In response to the melamine contamination a large number cyromazine, dicyandiamide, melamine, triuret, and urea of analytical methods were developed for the detection of (Figure 1) have been developed and validated to test milk melamine and its analogues, including several published by products and bulk protein. (4, 5) the United States Food and Drug Administration (FDA) that Recently, traces of dicyandiamide were found in also targeted cyanuric acid. (4-8) milk produced in New Zealand. Milk producers and However, the Kjeldahl method, the traditional standard government agencies moved quickly to reassure there technique for measuring protein content by indirectly was no risk to health. Here we present a fast, easy, measuring the nitrogen content in food, remains the most and sensitive LC-MS/MS method for the detection of widespread methodology. As long as protein content in dicyandiamide and other nitrogen rich compounds in food is not determined directly, economic adulteration milk and other protein-rich foods with limits of quantitation with nitrogen rich compounds will continue to be a down to low μg/kg.

32 Agro FOOD Industry Hi Tech - vol 25(1) - January/February 2014