Development of melamine certified reference material in milk using two different isotope dilution mass spectrometry...

Area of Science:

• Food Safety and Analysis
• Analytical Chemistry
• Metrology

Background:

• The melamine crises highlighted the urgent need for reliable testing methods and reference materials.
• Existing analytical methods required validation and standardization for accurate melamine detection in food products.
• A certified reference material (CRM) is essential for quality control and method validation in food analysis.

Purpose of the Study:

• To develop and characterize a new certified reference material (CRM) for melamine in milk (GLHK-11-02).
• To validate two novel gravimetric isotope dilution mass spectrometry (IDMS) methods for melamine quantification.
• To ensure accurate and reliable melamine analysis in food testing laboratories.

Main Methods:

• Preparation of a skimmed milk-based CRM (GLHK-11-02) fortified with melamine.
• Development and application of two gravimetric isotope dilution mass spectrometry (IDMS) methods: liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS).
• Thorough investigation of experimental parameters including standard purity, isotope equilibration, extraction efficiency, and matrix interferences.

Main Results:

• Excellent precision was achieved with coefficients of variation of 2.5% (LC-IDMS/MS) and 1.9% (GC-IDMS).
• Analytical data from both methods showed no significant difference, confirming accuracy and reliability.
• Certified value for melamine in GLHK-11-02 was 1.14 mg kg(-1) (dry mass fraction) with an expanded uncertainty of 7.1%.

Conclusions:

• The developed melamine in milk CRM (GLHK-11-02) is a reliable tool for method validation and proficiency testing.
• Both LC-IDMS/MS and GC-IDMS methods are sufficiently accurate and reliable for melamine certification.
• The CRM will enhance the technical competence of food and chemical testing laboratories in melamine analysis.