Screening and confirmatory methods for the determination of melamine in cow's milk and milk-based powdered infant formula: Validation and proficiency-tests of ELISA, HPLC-UV, GC-MS and LC-MS/MS

In recent years, two adulteration incidents concerning the addition of melamine, a small polar compound which is very rich in nitrogen, to pet food and infant formula products have occurred in China. These issues prompted private as well as governmental laboratories to develop methods for the analysis of melamine and related compounds in a wide variety of food products and ingredients. The development of methods was focussed on both, screening and quantification purposes, ranging from highly sophisticated chromatographic-mass spectrometric techniques to immuno-selective assays. The present work describes two screening and two confirmatory methods dedicated to the determination of melamine in cow's milk and milk-based powdered infant formula. Screening methods are enzyme-linked immunosorbent assay (ELISA) and liquid chromatography coupled to ultraviolet detection, while confirmatory methods are based on gas and liquid chromatography coupled mass spectrometry techniques. Performance and validation data of the four methods, and results obtained in the frame of internal and European proficiency-tests are shown.