| Organophosphorus pesticides (OPPs) are usually employed in protecting against insects during agriculture production. Up to now, various pesticides have been developed and used to prevent plants against diseases and insect pests. However, the potential hazard of pesticide toxicity to environment and human health has become more and more obvious. At present, due to a widely varied, large differences in polarity and stability of those frequent usage of OPPs, determination techniques with high sensitive and effectiveness for OPPs are highly required. Nevertheless, current extraction and detection methods have been proved with many disadvantages, such as prolonged sample pretreatment time and uneven recovery, which caused serious influence in the detection speed and precision.To this end, in this paper, we established a rapid and accurate determination method for organophosphorus pesticide residue in vegetables by integrating two aspects of sample preparation and instrument testing method. First of all, based on the physical and chemical properties of pesticide, the main technique parameters of gas flow micro-extraction technique including the rate of gas flow, temperature of sample phase and extraction time, were investigated. These parameters were proofed with positive effect on extraction efficiency though experiment and thesis, and an efficient gas flow purging micro-extraction method was developed for quick detection of OPPs in vegetables. The parameters of gas chromatography mass spectrometry (GC/MS) detection were optimized, and microextraction technique combined with GC-MS technique was established for rapid determination of OPPs residues in vegetables. The details of the contents and results of the thesis are as follows:1. Through the optimization of GC-MS conditions, the best GC-MS analysis and detection method for 28 kinds of organophosphorus pesticide was established. Analysis conditions of GC-MS is documented as follows: The analytes were separated on a DB1701ms fused-silica capillary column (30 m × 0.25 mm; thickness 0.25 μm), the programmed temperature:the GC oven program started at an initial temperature of 70℃ and was held for 2 min, then increase by 20 ℃/min to 150℃, by 5℃/min to 190℃ and kept for 2 min, by 10℃/min to 280℃, and held for 8 min. Other operating conditions was documented as follows:the injection temperature was 250℃ in splitless mode; the column flow was 1.0 mL/min; and helium (99.999% pure) was used as a carrier gas. The electron impact was used as source, the energy was 70 eV, and the temperature of ion source was set at 230℃. In the case of 28 OPPs standard samples, a good linear relationship was found with the concentration of OPPs from 5.0 to 1000 μg/L, the linear correlation coefficient (r2) was greater than 0.99; the lowest detection limit of method range (S/N= 3) is 0.3～ 3.0 μg/kg; the minimum quantitative limit (S/N= 10) was 1.0～10 μg/kg; the relative standard deviation (RSD) was 1.6%～3.2 (n= 3).2. Using new micro-extraction instrument of ME-101, the complete extraction and clean-up conditions was explored for the 28 of organophosphorus pesticide standard sample, this paper mainly examines influence of the sample temperature (Td), inert gas flow rate (u), and the extraction time (t) on extraction efficiency. The best conditions was established for extraction of OPPs in vegetables. The extraction conditions:volume of extraction solvent was 10 μL, extraction temperature was-4℃, gas flow rate was 2 mL/min, sample temperature was 250℃, and extraction time was 2min.3. A rapid detection method of residual OPPs in vegetable and edible fungus samples was established by combining the gas flow purge microextraction instrument (ME-101) and gas chromatography mass spectrometry. This method was evaluated through the real samples spiked with low, medium, high three concentration levels. Recovery of real spiked samples range from 88.67% to 122.48%, with RSD was 2.0% ～12.4%. Results showed that this method meets the requirement of real samples.4. Comparison of this method with soxhlet extraction, accelerated solvent extraction, and ultrasonic extraction. For detection of 28 OPPs in vegetales, the recovery of this method was 94.47%～113.48%, the average of RSD was 7.2%, volume of extraction solvent was 10 μL, extraction time was 2 min; the recovery of soxhlet extraction was 80.04%～106.02%, the average of RSD was 7.7%, volume of extraction solvent was 200 mL, extraction time was 6～8 h; the recovery of accelerated solvent extraction was 82.63%～109.32%, the average of RSD was 7.4%, volume of extraction solvent was 100 mL, extraction time was 10 min; the recovery of ultrasonic extraction was 83.14%～108.41%, the average of RSD was 7.7%, volume of extraction solvent was 30 mL, extraction time was 20 min. The recovery of this method is consistent with the above methods, satisfying the requirements of trace analysis. In terms of extraction time and extraction solvent, this method is fast and solvent-saving, conducive to the mass sample testing.5. We also attempted to extend the applications of ME-101 extraction method, and tried to combine he micro-extraction device with accelerated solvent extraction and ultrasonic extraction methods. Our experimental results showed that the recovery of organic phosphorus pesticides in vegetables by the accelerated solvent extraction and micro extraction purification methods were determined as 88.25%～108.35% with the average relative standard deviation of 4.4%-10.3%; while that data were determined from 85.72% to 107.52% by using ultrasonic extraction and purification of micro extraction methods, along with the average relative standard deviations of 5.1%～10.6%. Our finding indicated that the recovery and relative standard deviation meet the requirements of trace analysis, which indicated that this method could extend to the applications of micro-extraction device.6. We also made this ME-101 micro-extraction device to be mounted on mobile devices, resulting in the realization of on-line detection of organophosphorus pesticides of several leafy vegetables samples without processing. It is believed that this strategy is helpful to realize the real-time and automatic monitoring samples detection technology.7. The rapid detection method of ME-101/GC-MS was used for monitoring organophosphorus pesticide residues in vegetables retailed in Yanji. In the 33 kinds of vegetables (2180 samples), the percentage of detection of residual pesticide is 44.95%, pesticide was detected in most in leaf vegetables, the number was up to 684; the detection in edible fungi was minimum, the number was 164. The most residual OPPs were chlorpyrifos, dichlorvos, methamidophos, and mara sulfur phosphorus in all kinds of vegetables. Residues pesticide was detected more than 2 kinds in each vegetables, the amount of pesticide and residues kinds was highest for the celery. As can be observed from the monitoring data, the pesticides is very common in retailed vegetables in Yanji city.8. The mean concentration of residual OPPs was determined in sold vegetables in Yanji market by using the rapid detection method of builted ME-101/GC-MS. The dietary intake of risk assessment was investigated by using the mean concentration of residual 28 kinds of pesticide in vegetables and edible fungi. Results showed that the pesticide risk factors was less than 100% for edible fungi, which indicated that food would pose unacceptable risks for the general population. The pesticide risk factors of leaf vegetables such as celery, cabbage, spinach, turnip were demonstrated to be less than 100%, which indicated that these four vegetables in Yanji city may produce an unacceptable risk for the common person.Moreover, using the rapid detection method of new ME-101/GC-MS, a survey was performed aganist organophosphorus pesticide residues in vegetables and edible fungi in Yanji, and the health risk assessment was also analyzed for long-term intake of vegetables with residue pesticide in people. It is of great significance for monitoring the use of pesticides in our oblast, and determining the risk of the long-term exposure to low dose regularly intake OPPs pesticides. |
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