Determination of Cyromazine and Melamine Residues in Vegetables by Triple Quadurupole Liquid Chromatography-Tandem Mass Spectrometry with Hydrophilic Interaction Chromatography

A fast,sensitive and specific method was developed to determine cyromazine and its metabolite melamine in vegetables.The targets were extracted with the mixture of methanol-water(9∶1,V/V) from vegetables.The pH of extract was adjusted with hydrochloric acid.Then partial extract was purified through strong cation-exchange cartridge without concentration.After the residues were eluted with 8 mL methanol-ammonium solution(95∶5,V/V),the eluate was evaporated to dry with nitrogen stream and then dissolved in 5 mL mobile phase.Hydrophilic interaction chromatography combined with MS/MS was used to simultaneously determine cyromazine and melamine.The mobile phase was composed of acetonitrile and water with 0.1% formic acid(9∶1,V/V).The correlation coefficient was 0.999 for both compounds when concentrations ranged from 0.01 to 0.25 mg/L.Signals of cyromazine and melamine were suppressed in matrices.The peak area of cyromazine in matrices reduced to 41%-52%.And the peak area of melamine in matrices reduced to 78%.At fortification level of 0.04 and 0.20 mg/kg in vegetables,the average recoveries were 84.25%-101.3% for cyromazine and 72.5%-97.1% for melamine.And the RSD was 4.5%-10.7% for cyromazine and 4.3%-10.8% for melamine.The LOD was 0.01 mg/kg for cyromazine and 0.005 mg/kg for melamine.The method was used to determine the cyromazine and melamine residues in vegetables from market.