Press Release Source: Dionex Corporation
The 2008 China melamine scandal in which the discovery of milk powder adulterated with melamine led to a global recall of Chinese infant milk formula, chocolates, biscuits, cakes, and other milk-based products is resurfacing. This month, the China Daily reports that melamine-contaminated milk-based products from three companies have been removed from shelves in the Guizhou province.
In the 2008 contamination scandal, 6 infants died, over 300,000 people got sick, and executives from two companies responsible for the contaminated products were executed.
Melamine, used in the manufacturing of plastics and fertilizer, is added to milk products to artificially inflate the protein content as determined by the commonly used protein assays. Cyanuric acid and melamine are structurally similar and often occur in solution together forming an insoluble compound which promotes the formation of crystals in the kidneys (urolithiasis) leading to the formation of kidney stones.
Dionex has several solutions for the analysis of melamine described in this information bulletin.
Solution 1: Determining Melamine and Cyanuric Acid using LC-MS and the Dionex Acclaim® Mixed-Mode WAX-1 column
This presentation titled, Simultaneous Determination of Melamine and Cyanuric Acid Using LC-MS with the Acclaim Mixed-Mode WAX-1 Column and Mass Spectrometric Detection, introduces a sensitive, simple, and high-throughput method for simultaneous determination of melamine and cyanuric acid by LC-MS and uses stable isotope labeled internal standard (ISTD) for quantification.
Highlights of the method include:
Guidelines for sample extraction techniques are described in Dionex Technical Note 209, Accelerated Solvent Extraction Sample Preparation Techniques for Food and Animal Feed Samples, and Dionex Technical Note 208, Methods Optimization in Accelerated Solvent Extraction.
Dionex Technical Note 209
Dionex Technical Note 208
Solution 2: Bruker Daltonics solution analyzes Melamine by LC/MS/MS using a Dionex system and consumables
Bruker Daltonics coupled their high-capacity ion trap (HCT) mass spectrometer with the Dionex UltiMate® 3000 HPLC system and the Dionex Acclaim® Mixed Mode WAX-1 column to detect and quantify melamine and cyanuric acid in five minutes.
Solution 3: Application Note 224 describes how to determine melamine in milk powder using Reversed-Phase HPLC with UV detection
This application note titled, Determination of Melamine in Milk Powder by Reversed-Phase HPLC with UV Detection, demonstrates how an ion-pairing reversed-phase method can be run with an Acclaim 120 C18 column and an UltiMate 3000 system with UV detection following the regulated method.
Solution 4: Application Note 221 describes a quick and simple method to determine melamine in liquid milk and milk powder
Application Note 221, Rapid Determination of Melamine in Liquid Milk and Milk Powder by HPLC on the Acclaim Mixed-Mode WCX-1 Column with UV Detection, describes an efficient and simple method for preparing liquid milk and milk powder samples using a Dionex UltiMate 3000 system and the Acclaim Mixed-mode WCX-1 column. The column exhibits good retention of melamine, using ammonium acetate buffer and acetonitrile as the mobile phase. This mobile phase makes this method compatible with MS detection.
The method described in Application Note 224 (described above) is not able to successfully analyze liquid milk, so another method was developed using the Mixed-Mode column that could be used for both liquid and powdered milk samples. The application chemists also developed a new sample preparation procedure, and further demonstrated that their method was accurate by recovery studies, and also for powdered milk samples by comparing the results to the method in Application Note 224.
Solution 5: Application Note 231 describes how to determine melamine in milk by IC with UV detection
Application Note 231, Determination of Melamine in Milk by Ion Chromatography with UV Detection, describes how melamine is separated on the Dionex IonPac® CS17 column, designed for amine separations, and detected at 240 nm. During this work, the lab discovered that some samples had compounds that interfered with melamine determinations. To eliminate this problem, the lab designed an online sample preparation method that traps the melamine on a TCC-LP1 and washes interfering compounds to waste before eluting the melamine on to a CS17 columns set. This method also features all the reproducibility and productivity advantages of eluent generation.
As you can see from the above solutions, Dionex has spent a considerable amount of time and effort coming up with a range of solutions for the analysis of melamine to match the different needs of customers. In addition to solving this analytical challenge using a common C18 RP method, Dionex has applied its considerable expertise in column development (two Mixed Mode columns, the nano-engineered Trinity® column, and a uniquely designed IC column) along with its expertise in application development to give customers a wide range of options for quick and easy solution to this analytical problem.
Articles Highlighting Dionex Solutions for Melamine Analysis
American Laboratory
A Fast Method for the Determination of Melamine in Liquid Milk and Milk Powder by HPLC with UV Detection
This article compares results of experiments using the current C18 method and a new, rapid HPLC method performed using an Acclaim Mixed-Mode WCX-1 column (Dionex Corp., Sunnyvale, CA). The column features a mixed-mode silica-based packing material that incorporates both hydrophobic and weak cation-exchange properties, and demonstrates high potential for separating samples that contain a mixture of ionic and neutral compounds, without requiring ion-pairing compounds.
Melamine analysis of liquid or powdered milk is completed within 10 min, about half the time required for the C18 separation. The background noise is significantly reduced using the WCX-1 column, and the mobile phase is also compatible with MS detection. A new sample preparation method that eliminates the SPE and evaporation steps is also demonstrated.
Journal of Agricultural and Food Chemistry
Use of Methanol for the Efficient Extraction and Analysis of Melamine and Cyanuric Acid Residues in Dairy Products and Pet Foods
The recent worldwide shortage of acetonitrile has prompted the development of a new method using methanol as an alternative organic solvent in the extraction and liquid chromatographic analysis of melamine and cyanuric acid that may be present as contaminants in dairy products and pet foods. A simple extraction of melamine and cyanuric acid residues in fortified samples was successfully achieved, using a methanol-water mixture and analysis by isotopic dilution high-performance liquid chromatographytriple- quadrupole mass spectrometry (HPLC-MS/MS).
A two-step centrifugation procedure was employed to remove matrix components from extracts. The separation of melamine and cyanuric acid was carried out on a Dionex Acclaim Trinity P1 column, with a methanol and ammonium acetate buffer used as the mobile phase. Excellent linearity was achieved for both the melamine and cyanuric acid calibrations. A variety of dairy products and pet foods were fortified with melamine and cyanuric acid at three levels, 1, 2.5, and 10 ug/g, producing recovery yields of 101- 119% for melamine and 84-123% for cyanuric acid. The lower limit of quantification (LLOQ) of melamine was 0.03 ug/g for liquid milk and 0.05 ug/g for dry infant milk formula. The quantitative results were comparable with those derived from previous methods that have been proposed by the U.S. Food and Drug Administration for the screening of melamine and its analogues in foods.
About Dionex
Dionex is a global leader in the manufacturing and marketing of liquid chromatography and extraction systems, consumables, and software for chemical analysis. The Company's systems are used worldwide in environmental analysis and by the life sciences, chemical, petrochemical, food and beverage, power generation, and electronics industries. Our expertise in applications and instrumentation helps analytical scientists to evaluate and develop pharmaceuticals, establish environmental regulations, and produce better industrial products. For more details on Dionex solutions, please visit us at www.dionex.com.
