Detection of melamine in a human renal uric acid stone by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)

► Melamine content in urine and uric acid stone specimens was analyzed. ► Uric acid stone was first screened by a FTIR method. ► One melamine FTIR positive stone was confirmed by MALDI-TOF MS. ► MALDI can detect melamine in stones which urinary melamine was undetectable. ► MALDI-TOF MS can be an additional analytical method for melamine exposure.