Melamine powder, a nitrogen-containing heterocyclic compound, is widely used in industrial production but poses severe health risks when illegally added to feed, milk, and dairy products. The 2008 Chinese milk scandal and 2007 U.S. pet “poisonous food incident” highlighted the urgency of strict monitoring. This article details melamine’s toxic mechanisms, the reasons for its illegal addition, and detection methods, and provides research progress for food safety inspectors, laboratory technicians, and public health professionals.
Melamine powder (chemical formula:C3H6N6, molecular weight: 126.12) is a white monoclinic crystal with distinct physical and chemical characteristics:
Melamine powder itself has low acute toxicity, but long-term or excessive intake causes serious health damage, with varying sensitivity among populations:
The root cause of melamine contamination in milk, dairy products, and feed is economic fraud driven by flawed detection methods:
Adding 0.01% melamine per kilogram of milk can falsely increase the detected protein content by 0.4%, helping illegal manufacturers meet quality standards (e.g., previous national standard requiring milk protein ≥2.95 g/100 g) and obtain higher purchase prices.
Sublimation Method: Melamine sublimes under vacuum and heating; the content is calculated by the mass difference before and after sublimation.
Potentiometric Titration
Principle: Titrate the melamine solution with standard sulfuric acid; calculate the concentration based on the volume of sulfuric acid consumed when the pH drops from 5 to 3.
Advantage: Simpler than gravimetric methods, suitable for rapid qualitative screening in laboratories.
ELISA Kit Method
Principle: Use antigen-antibody specific binding. Sample-extracted melamine competes with HRP enzyme-labeled melamine for antibody binding; the concentration is determined by measuring absorbance.
Advantages: Fast (results in ~1 hour), simple operation, no need for complex instruments—ideal for on-site qualitative detection by grassroots supervision agencies.
High-Performance Liquid Chromatography (HPLC)
Principle: Simple sample pretreatment (extraction + purification), quantitative analysis via external standard method.
Performance: Quantitative limit of 2 mg/kg, low cost, and wide application in dairy product testing laboratories.
Gas Chromatography-Mass Spectrometry (GC-MS/GC-MS/MS)
Principle: Combines gas chromatography separation and mass spectrometry detection for high specificity and sensitivity.
Performance: GC-MS quantitative limit is 0.05 mg/kg; GC-MS/MS quantitative limit is 0.005 mg/kg—suitable for trace melamine detection.
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Principle: No derivatization required, simple pretreatment, high accuracy, and sensitivity.
Performance: Quantitative limit of 0.01 mg/kg, recognized as a benchmark method for trace melamine detection in food safety supervision.
HPLC | 2 mg/kg | Routine detection of most samples |
GC-MS | 0.05 mg/kg | Trace detection requirements |
LC-MS/MS | 0.01 mg/kg | Ultra-trace detection and confirmation |
On-site detection methods (e.g., ELISA) have low sensitivity and cannot provide quantitative data.
Laboratory quantitative methods (e.g., LC-MS/MS) require expensive equipment and professional operators, making them inaccessible to grassroots agencies.
Complex matrices in feed and animal products (e.g., proteins and fats) can interfere with detection accuracy.
Portable On-Site Detection: Develop handheld, easy-to-operate qualitative devices for rapid screening by grassroots supervisors and the public.
Cost-Effective Quantitative Technology: Optimize existing methods to reduce equipment and reagent costs, enabling widespread use in small and medium-sized laboratories.
Dual Integration: Combine on-site qualitative screening (rapid preliminary judgment) and laboratory quantitative confirmation (accurate result determination) to improve supervision efficiency.
High-Sensitivity Miniaturization: Develop microfluidic chips or biosensors for ultra-trace, rapid detection with lower sample consumption.
Melamine’s illegal addition to animal products poses severe threats to public health, with toxicity mainly targeting the urinary system. Current detection systems rely on complementary qualitative and quantitative methods, but there is an urgent need for more portable, cost-effective technologies.
For food safety supervision, combining on-site rapid screening with accurate laboratory confirmation can improve efficiency. For researchers, developing high-sensitivity, easy-to-use detection tools is the key direction. By strengthening technical research and strict supervision, we can block illegal melamine addition and protect the safety of feed and animal products.
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