| Pesticides play a production increase active role in agricultural production.but problems caused by it have gradually been widespread concern at the same time recent years. Pesticide residues in foods beginning to show features which are many types and trace residues. And bring a lot of challenges to conventional pesticide detection. Governments have begun to develop and implement more stringent limits for pesticide residues meantime. August 1, 2014, Hong Kong Special Administrative Region started Pesticide Residues Management System "Regulation of Pesticide Residues in Food " The standards regulation ruled the number of 360 kinds of pesticides, 7083 limits which exceeds the current standards numbers of the mainland. And Hong Kong "Regulation" has a lot of materials are not limited in the the current mainland standards. In this study, detection method of pesticides from Hong Kong Regulation were studied and established for the first time. and high-throughput detection of pesticides was also explored.The research background was introduced in the first chapter. The "Regulations" was compared with Chinese mainland standards. The research statuses of multi-residue detection technology and sample pre-treatment technology were settled.A method for screening of 249 residue compounds from the Hong Kong`s regulation on pesticide residues in foods was developed by liquid chromatography coupled with quadrupole time-of-flight mass spectrometry(LC-Q-TOF/MS). Liquid chromatography technology using liquid as mobile phase was developed in early 1970 s. It has a wider detection range, better applicability compared with gas chromatography. TOF mass spectrometry has a rapid development in recent years with characteristics of high throughput and high resolution. The theory numbers of detected ions are unlimited and the deviation of accurate mass of target ions was usually no more than hundred thousandth. There are other characteristics such as spectral library retrieval, unknown material structure analysis and so on. This chapter maximize detected 249 target compounds from the "Regulation" of Hong Kong binding LC spectrometry with time of flight mass assay. Two databases of accurate mass and fragment ions were created. Target precursor ions’ s form were confirmed and collision energies were optimized. For liquid chromatography conditions such as column and mobile phases were comparative studied. Qu ECh ERS was adopted because of its high versatility in sample pretreatment. Solvent extraction and purification powder compositions were optimized and 11 kinds of common food matrix effects were evaluated. The results demonstrated that the linear range was from 10 to 500 μg/kg with good correlation coefficients(r>0.90). The method quantitation limits were in the range of 10~100 μg/kg(S/N≥10). There are 163 compounds quantitation limits were 10 μg/kg, 33 compounds quantitation limits were 20 μg/kg, 36 compounds quantitation limits were 50 μg/kg, 17 compounds quantitation limits were 100 μg/kg. For rices, mushrooms, soybeans, spinaches, tomatoes, broccolies, grapefruits, chives, carrots, lettuces, cucumbers, The average recoveries at three spiked levels were in the range of 23.2%~133.2%, 35.6%~137.6%, 38.7%~140.2%, and relative standard deviation(RSD) of 1.3%~19.2%(n=6).Matrix effect significant showed significant inhibition effect. Matrix-matched external standard method was adopted for quantification finally. 383 of 534 commercial fruit and vegetable samples were not detected in some places for conducting practical application. There was a higher pesticide detection rate in samples of grapes, strawberries, celery, cabbage. Fungicides and insecticides such as dimethomorph and carbendazim have a high detection frequency.A method for screening of 182 residue compounds from the Hong Kong`s regulation on pesticide residues in foods was developed by gas chromatography coupled with quadrupole time-of-flight mass spectrometry(GC-Q-TOF/MS) in this chapter. Compounds that get gasified easily and thermal stability especially for the LC-Q-TOF method unresponsive in second chapter were detected by gas chromatography. The method achieved the detection of Hong Kong, in the 182 kinds of pesticide residues from the "Regulation" combined with the advantages of gas chromatography and time –of –flight mass spectrometry. Two databases of accurate mass using EI ion source and fragment ions were created and two characteristic ions of each substance was selected. Extraction solvent and collision energies were optimized. 11 kinds of common food matrix effects were evaluated. The method quantitation limits were in the range of 10~100 μg/kg(S/N≥10). There are 114 compounds quantitation limits were 10 μg/kg, 49 compounds quantitation limits were 20 μg/kg, 13 compounds quantitation limits were 50 μg/kg, 6 compounds quantitation limits were 100 μg/kg, 2 compounds quantitation limits were 500 μg/kg.For rices, mushrooms, soybeans, spinaches, tomatoes, broccolies, grapefruits, chives, carrots, lettuces, cucumbers, The average recoveries at three spiked levels were in the range of 36.1%~121.5%、35.4%~125.8%、37.2%~128.9%, and relative standard deviation(RSD) of 0.8%~17.6%(n=6). Matrix effect significant showed significant enhancement effect. Matrix-matched external standard method was adopted for quantification finally. 253 of 326 commercial fruit and vegetable samples were not detected in some places for conducting practical application. There was a higher pesticide detection rate in samples of chives, lettuces. Fungicides and insecticides such as endosulfan and chlorpyrifos have a high detection frequency.The high-throughput detection technology was compared with two classical GB methods. GB methods are "Determination of 500 Kinds of Pesticides and Related Chemicals Residues by Gas Chromatography-Mass Spectrometry"(GB/T 19648-2006)and "450 Pesticides and Related Chemicals Residues in Fruits and vegetables by Liquid Chromatography-Tandem Mass Spectrometry"(GB/T 20769-2008). Advantages and disadvantages of this method was concluded through comparing the operation steps, the time required to complete pre-treatment, the detection time, the amount of reagent, internal standard, recoveries, precision, detection limits, suitable matrix, instruments. The results show that the high-throughput detection technology has the advantages of less pretreatment steps, detected time and reagent, no internal standard, widely applicable matrix. There was some disadvantages in the comparison of the experimental methodology while the results can still meet the relevant regulations in the end.The method is simple, efficient, sensitive, widely applicable matrix. It is The numbers of suitable food matrices applications for using high-throughput detection method is the most in the currently reported which using an accurate mass determination of suspected substances. fragment ions spectrograms confirmation. The method can effectively avoid false positive situation, has strong ability of qualitative and also quantification accuracy.It can meet the actual applications and greatly simplify inspection process as well. |
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