Residual Migration and Degradation of Spirodiclofen During Tea Growing, Processing and Brewing by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry

Abstract

Tea is one of important economic crops in China. With the continuous expansion of its planting scale and frequent occurrence of diseases and insect pests, chemical pesticides are mostly used to quickly prevent and control diseases and insect pests in tea gardens. However, there are a few kinds of pesticides registered in tea garden. After longterm of single and frequent usage, pests in tea garden are easy to produce resistant, resulting in the control effects reduced and the pesticide usage increased, and a widespread concern is attracted for the pesticide residues in tea. Therefore, it is of great significance to find a new pesticide in tea garden and to evaluate the residue behavior of the pesticide and to set the maximum residue limit standard on tea. In this study, a residue analysis method of spirodiclofen in fresh tea leaves, black tea, green tea, black tea infusion and green tea infusion was established by an optimized QuEChERS pretreatment combined with ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The correlation coefficient (R2) of spirodiclofen in the standard curves of solvent and different matrices were above 0.993 6 at the concentration range of 0.005~2.5 mg/L, and the detection limits (LODs) were all less than 0.002 mg/L. The recoveries of spirodiclofen ranged from 78.8% to 107.5%, and the relative standard deviations (RSDs) were 1.3%~13.9% for four different spiked concentrations, the quantification limits (LOQs) of spirodiclofen in fresh tea leaves, black tea and green tea, and black tea infusion and green tea infusion were 0.002 mg/kg, 0.005 mg/kg and 0.000 2 mg/L, respectively. This method was used to analyze the migration and degradation of spirodiclofen during tea growing, processing and brewing, it was found that the degradation half life of spirodiclofen on fresh tea leaves in Zhejiang was 3.29 day, after processing, from fresh tea leaves to black tea and green tea, the residues of spirodiclofen were significantly reduced 33.6%~51.8% and 22.7%~63.4%, respectively. The leaching rates of spirodiclofen in black tea infusion and green tea infusion were very low, with the total leaching rates were 1.8%~4.3% and 1.5%~2.8%, respectively. The dietary risk assessment showed that the maximum intake of spirodiclofen in human drinking was 0.000 069 mg/kg[DK]•d bw, which was only 069% of the ADI value of spirodiclofen, and the national estimated daily intake (NEDI) of spirodiclofen was 0.362 2 mg, the acceptable daily intake was 0.63 mg, so the risk probability was 57.49%. Thus, the maximum residue limit (MRL) of spirodiclofen in tea can be set at 10 mg/kg in China, which has only a lower risk for human tea intake.

Keywords

• ultra-performance liquid chromatography tandem mass spectrometry (uplc-ms/ms)
• spirodiclofen
• tea processing
• migration and degradation
• leaching rate
• risk assessment
• maximum residue limit (mrl)