| Persistent organochlorine pesticides (OCPs) were easily enriched in human adipose tissue, serum and breast milk through the delivery of the food chain. And finally threatened to human health and survival. The OCPS and some simple primary metabolites of them had been studied in breast milk in the previous studies. In order to further improve the detection scale of OCPs and deeply assess the human burden and dietary exposure of OCPs, this study was aimed at developing an innovative method covering seven major categories of the27components including parent compounds and their primary secondary metabolites using a stable isotopic dilution technique coupling with LVI-GC-MS/MS. In order to further improve method’s sensitivity and accuracy to meet the detection level of part per trillion, the comprehensive studies involved the sample pretreatment (including the extraction and separation and mass spectrometry detection) were carried out and cleaning up) and instrumental analysis (including chromatographic finally a satisfactory method was successfully validated.100breast milk samples collected from shanghai are between the year of2010and2012were determined by the method developed, which confirmed the practicability of this method, In additionally, based on the monitoring data of100breast milk samples and the reported data from Shanghai area between the year of2002and2010and the developed countries (such as the United States, Japan, Korea, some European countries) and some developing countries in Asia and Africa, the comprehensive comparison studies were carried out in terms of the regional exposure difference, the change trends along time, the main contribution of individual target analyte to the whole exposure of OCPs in breast milk and so on. The research work is divided into three chapters.In the first chapter, formation processes and hazards of OCPs and metabolites were introduced. The research progresses on OCPs and metabolites were summarized in breast milk and dairy products at home and abroad. The significance and content of the study were expounded in the end of this chapter.The detailed process of how to develop the detection method was elaborated in the second chapter, In order to further improve the sensitivity and accuracy of detection to meet requirements for trace detection in breast milk, the pre-treatment method was based on accelerated solvent extraction (ASE), solid phase extraction (SPE) cleanup followed by gel Permeation chromatography (GPC) cleanup. So low background and small interference was retained even when the sample was concentrated250times. In order to compensate the potential loss of the target analytes during the process of pre-treatment and injection of GC-MS/MS, the stable isotopic standards were employed as isotopic internal standards to calibrate their native analytes and as internal standards to calibrate the remaining target analytes with close retention time and similar chemical properties to them. Due to the strong anti-matrix interference capability, gas chromatography-tandern mass spectrometry (GC-MS/MS) was used to enhance the accuracy of qualitative and quantitative, and improve the detection sensitivity and accuracy. The dynamic linear was in the range of0.5to100mg/L of each pesticide, the correlation coefficients R2were higher than0.998. The minimum detection limits (MDL) of27target analytes were between0.066and1.7ng/kg. The detection sensitivity is increased100fold Compared with the previous reported. Best accuracy and precision of the method were obtained with satisfactory recoveries at the low spiked level. At the spiked level of0.016μg/kg, the average recoveries were between60.2%and123.7%with the relative standard deviations of less than13.5%. At the spiked level of0.08μg/kg, the average recoveries were between70.1%and119.8%with the relative standard deviations of less than14.4%. The results of method validation indicated that it was a sensitive, accurate and suitable method for determination of real samples.In the third chapter, the investigated results of100breast milk samples were discussed. Due to the increased sensitivity of the method, the detectable rate was greatly improved to more than76%, In addition to8-HCH with54%of detectable rate, HCHs and DDTs were the predominant pollutants of OCPs with the mean pollution levels of251583pg/g and62404pg/g, respectively. Pollution levels of OCPs were declined significantly in comparison with monitoring results from2002to2007. The gap with the developed countries was gradually narrowed on pollution levers of OCPs. The detectable rates of persistent OCPs and metabolites were high and pollution levels of some metabolites, such as hexachlorobenzene, DDE were still high, therefore the health risks can not be ignored. Continuous monitoring of OCPs pollution in breast milk should be strengthened. Some new and high toxic metabolites of OCPS (such as DDMU, DDM, DDOH, DBP, Endosulfan lactone and Endosulfan ester), which were continuously detected in breast milk, should be considered including the detected objects of persistent OCPs. So it is more accurate and comprehensive to grasp the trends in organisms, real exposed levels in the human body and assess the human burden of persistent OCPs of Shanghai residents. |
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