Residue Analysis and Dissipation of Bromothalonil in Tobacco

To study residue and dissipation of bromothalonil in tobacco, a modified QuEChERS combined with gas chromatography triple quadrupole-tandem mass-spectrometry (GC-MS/MS) liquid chromatography-tandem mass spectrometry method was developed. Samples were extracted with acetonitrile, cleaned up with primary secondary amine (PSA), and then determined with GC-MS/MS. The results showed that the average recoveries of bromothalonil were 85.8%-94.5% and 83.2%-110.0%, with relative standard deviations (RSDs) of 1.4%-10.6% and 7.3%-14.1% in fresh and cured tobacco leaves, respectively. The limit of quantification (LOQ) of this method was 0.01 mg/kg for both fresh and cured tobacco leaves. The dissipation and terminal residues were investigated in Qingdao and Changsha, China from 2012 to 2013. The dynamic results showed that the half-life of bromothalonil in fresh tobacco leaves was 7.8-14.9 d. The terminal residues of bromothalonil in cured tobacco leaves were determined after the first and second application at levels of 162 g.a.i/hm^-2 and 243 g.a.i/hm^-2. The terminal residues were 0.010-0.13 mg/kg 14 days after the last application in cured tobacco leaves. Based on the tobacco bacterial wilt incidence conditions, the incidence period, the use of pesticides in tobacco and OECD MRL calculator findings, we recommend the residue limit of bromothalonil in tobacco leaves of 0.2 mg/kg, and the safety interval of 14 d.