Residual Behavior Of Some Pesticides In Chrysanthemum Processing And Pesticide Bioavailability In Environmental Water

Chrysanthemum, as one of the most popular Chinese herbal medicines all over the world, is commonly used to ensure human health in daily life, and its processing products for medicines, food or drinks use also have positive effects on human health concerns. The pesticide residues in chrysanthemum and its processed products may be directly related to human health. The pesticide residues in environmental water showed potential toxicity to aquatic organisms and human. For these reasons, it is considered of interests for analyzing the residue of pesticides in CHMs and its transfer behavior during processing, and bioavailable concentrations of pesticides partition into organisms in environmental water.This study focuses on the development of novel analytical methods for determining pesticide residues in chrysanthemum, and residual behavior during processing of chrysanthemum. For prediction of toxicity in environmental water, a calibration method of using passive sampler, combining with performance reference compounds was developed and validated to measure freely dissolved concentrations of pesticides. The results were listed as following:1. Development of novel multi-residue analytical methods of pesticides in chrysanthemum:The chrysanthemum samples were extracted with n-hexane, and cleaned with a combination of gel permeation chromatography and solid phase extraction for determining 46 pesticides by gas chromatography with electron capture detector. The average recoveries were in a range of 71.3%-102.6%, and relative standard deviations were between 1.4% and 15.7%. The limits of detection and limits of quantification were 0.0005 μg/g～0.1μg/g and 0.002 μg/g～0.2μg/g, respectively. The results demonstrated its application in analyzing pesticide residues in chrysanthemum samples.A novel matrix extraction-vortex-assisted dispersive liquid-liquid extraction based on conventional QuEChERS and dispersive liquid-liquid extraction was developed. This method was validated by determining 9 fungicides in chrysanthemum by gas chromatography with electron capture detector. The average recoveries were in a range of 73.9%～95.1%, relative standard deviations were between 3.5% and 9.7%, and enrichment factors ranged from 51 to 88. The limits of detection and limits of quantification were 0.005 μg/kg ～-0.05 μg/kg and 0.02 μg/kg～0.2 μg/kg, respectively. The proposed method offers good extraction and cleanup efficiency, high sensitivity, and strong potential of applicability.A simultaneous determination method of 10 pesticides in chrysanthemum was performed by high-performance liquid chromatography/tandem mass spectrometry. A novel carbon-based nanomaterials, named multiwalled carbon nanotubes mixing with primary secondary amine as the cleanup sorbent was applied to removing interferences in chrysanthemum samples. The average recoveries were in a range of 78.3%～95.1%, except for cyromazine (58.3%～70.3%), and relative standard deviations were between 3.5% and 9.7%. The limits of detection and quantification were 0.1 μg/kg～1μg/kg and 0.3 μg/kg～3μg/kg, respectively. The application of multiwalled carbon nanotubes and primary secondary amine mixture allowed the elimination of matrix suppression effect from chrysanthemum matrix.2. Study on the change of pesticide residues during processing of chrysanthemum:The residual behavior of 11 pesticides residues from chrysanthemum to its tea infusion was investigated at different infusion conditions:water temperatures (70℃,80℃,90℃,100℃), infusion intervals (5 min,15 min,30 min), infusion times (1,2,3,4,5 times), and with or without cap. The concentrations of the 11 pesticides were in a range of 0.36 μg/kg～185μg/L, and transfer percent were from 1.0% to 91.1% under varied water temperatures and infusion intervals. The transfer percent decreased gradually after each infusion, and the fifth transfer in infusion accounted for only 10% of the first transfer. The transfer of most of the pesticides decreased with the increasing infusion intervals with no-cap procedure. The residual behavior of pesticides from chrysanthemum to tea infusion could be predicted by fitting the data of transfer or loss percentages and physicochemical properties of target pesticides to exponential or log equation. These findings provided practical processing methods for tea infusion in daily life.3. Development of passive sampler-performance reference compound calibration method for bioavailability measurement of 8 pyrethroids in environment water:The polyethylene film was used as passive sampler, combining with performance reference compounds for deriving the freely dissolved concentrations of 8 pyrethroids in surface water. The absorption kinetics study showed the partition coefficient values of 8 pyrethroids were in a range of 0.8×105～1.5×105, and the absorption rate constants of different pyrethroids were similar, ranging from 0.005 min-1 to 0.0074 min-1. The isotropy between absorption of pyrethroids and desorption of performance reference compounds suggested the feasibility of this proposed passive sampling calibration method for measuring freely dissolved concentrations.The performance of the proposed calibration method was validated in fish tank experiments. The freely dissolved concentrations of 8 pyrethroids at different sampling intervals were similar, indicating the applicability of the proposed method. With the addition of humic acid or sea salt, the freely dissolved concentrations decreased by 19%-98% compared with those in fresh water. The passive sampler device was further applied at three sites in Southern California. Five pyrethroids were detected with freely dissolved concentrations of 1.56 ng/L～12.5 ng/L and 7.59 ng/L～92.4 ng/L in 2015 winter and 2016 spring, respectively. Results to date demonstrated the feasibility of coupling polyethylene film with performance reference compounds for in situ monitoring of the bioavailability of pyrethroids in surface water.This study described the development of novel analytical method, residual behavior affected by different processing methods, and bioavailability measurement of pyrethroids in water, which could provide guidance for the relevant research fields in the future.