Determination of Dufulin residues in cucumber and tomato by gas chromatography-mass spectrometry with solid phase extraction and its fragmentation mechanism

A solid phase extraction coupled with gas chromatography-mass spectrometric(SPE-GC-MS) method was established for the determination of Dufulin residue in cucumber and tomato.After extracted with V(n-hexane):V(acetone)=1:1 mixture in high-speed homogenized extract method,the target samples were cleaned up in solid phase extraction by the mixture of N-propylethylenediamine(PSA),C18 and graphitized carbon(GCB),analyzed by GC-MS under selected ion monitor mode(SIM) and quantified by the external standard method.Good linear between the peak area and the concentration of Dufulin was obtained in the range of 0.01-0.5 mg/L with correlation coefficient not less than 0.999 under the optimum conditions,the limit of detection(LOD)(S/N=3)was 0.003 mg/kg and the limit of quantitation(LOQ)(S/N=10) was 0.01 mg/kg.The average recoveries of Dufulin from the cucumber and tomato blank samples at three spiked levels of 0.01,0.02 and 0.1 mg/kg ranged from 99.9% to 100.2% with RSD of 0.97%-3.07%.The fragmentation mechanism of Dufulin was also studied in which the qualitative ions and quantitative ions were confirmed.