Low-level quantification of melamine and cyanuric acid in limited samples of rat serum by UPLC–electrospray tandem mass spectrometry

This paper reports the development and validation of a methodology for the low-level quantification of melamine and cyanuric acid in limited samples of rat serum. The methodology, based upon ion-exchange solid phase extraction (SPE) and ultra-performance liquid chromatography (UPLC) coupled with electrospray tandem mass spectrometry (MS/MS) in multiple reaction monitoring (MRM) mode, relies on the use of stable isotope-labeled internal standards and requires only 15 μL samples of serum. The method provides a recovery of 80–110% of melamine with a signal suppression of ca. 55%, and a recovery of 50–90% of cyanuric acid with a signal suppression ca. 40–60%, affording lower limits of quantification (LLOQ) for melamine or cyanuric acid of, respectively, 5 ppb (mean accuracy 109%; CV = 4.9%) and 10 ppb (mean accuracy 96%; CV = 8.6%). The small sample requirements, excellent sensitivity, accuracy and precision, and high-throughput (5 min of instrument run time) make this methodology optimal for toxicokinetic or exposure assessments studies.