Development of a Sensitive HILIC-MS/MS Method for Quantification of Melamine, Derivatives, and Potential Precursors in Various Water Matrices

Melamine (MEL) has broad applications and can be released to the aquatic environment from various sources, including industry, agriculture, traffic, and household articles. In addition, MEL derivatives ammeline (AMN), ammelide (AMD), and cyanuric acid (CYA) as well as potential precursors cyromazine (CYRO) and hexa(methoxymethyl)melamine (HMMM) are relevant related substances. However, occurrence and transformation in water resources has not yet been thoroughly investigated. Here, we developed a sensitive analytical method for quantification of these analytes by hydrophilic interaction liquid chromatography (HILIC) coupled to tandem mass spectrometry (MS/MS). Direct injection achieved limits of quantification (LOQs) of 0.1 µg/L (AMN 0.2 µg/L; CYA 1 µg/L), while LOQs could be improved to 0.01 µg/L (CYA 0.05 µg/L) by applying evaporation for analyte pre-concentration. The method was extensively validated, showing good recovery, repeatability, and linearity. The evaluation of the matrix effects revealed method applicability for various water matrices, including surface water and wastewater. During proof-of-concept measurements, HMMM in combination with MEL and its derivatives was found in multiple samples, emphasizing the importance of including precursors. In the future, the developed method with its novelty of covering both MEL derivatives and precursors can be applied for comprehensive monitoring programs elucidating MEL sources and transformation in water resources.