Studies On The Determination Of Multiresidual Organic Pollutants In Environment And Food Samples By LC-MS/MS

Nowadays, a large amount of fungicides have been introduced in agriculture for the control or the prevention of diseases and the protection of quantity and quality of agricultural products. However, the fungicides often contaminate the environment through multiple routes, including spraying, soil seepage, storage and the discharge of waste water, leading to possible ground and surface water contamination as well as causing public health problems due to their high toxicity and long persistence. Perfluorinated compounds (PFC) are a large group of chemicals produced for several decades and widely used for many industrial and consumer applications. They are of toxicological and public concern because of their global occurrence in different environmental media, their persistence and potential to bioaccumulate in organisms. Thus, developing fast, simple and reliable methods to monitor the residues of organic pollutants in environment samples and food samples is of prime importance.Nowadays, GC, LC, GC-MS/MS, LC-MS/MS and HRGC-HRMS are fundamental methods in determination of organic pollutants. However, the using of GC, LC, GC-MS/MS and HRGC-HRMS are affected by several drawbacks that limit a more general use. High production costs for chemicals and materials, poor stability of experimental result and the tedious of test process, make a large-scale use very difficult. LC-MS/MS is becoming one of most powerful techniques for the residue analysis of polar, ionic or low volatility fungicides in complicated matrices, which combines the advantages of LC and MS for the separation and unequivocal identification of fungicides at low micrograms per kilogram levels in real sample matrices. LC-MS/MS provides high selectivity, sensitivity and mass resolution to reduce potential interference and enables the method to routinely achieve low levels of chemical detection, which is capable of discriminating more efficiently than LC and GC.In this paper we developed four analytical methods based on LC-MS/MS for the determination of multiresidual organic pollutants in environment and food samples.Firstly, we developed and validated a method for the quantitative determination of flumorph residues in vegetable and fruit samples using dimoxystrobin as internal standard (I.S.), studied the conversion rule between Z-isomer and E-isomer of flumorph, confirmed their chromatographic behavior by monitoring concentrations of two isomers of them at room temperature under sunlight. Flumorph residues were detected in 70% of the samples analyzed and the highest concentration level was 1.83 μg kg-1 in tomato sample.Secondly, we proposed a simple and sensitive method for the determination of multiresidual fungicides in environment water samples.In which, different modifiers of mobile phase were investigated to enhance ionization efficiency and affect chromatographic separation. The following parameters that affect the SPE procedure efficiency were optimized:the column type, the wash solvent and the elution solvent. Qualitative and quantitative detection of the analytes were carried out under the multiple reaction monitoring (MRM) in positive ionization mode after chromatography separation.Thirdly, we developed an original method for the determination of aflatoxin B1, B2, G1, G2 and M1 in corn by LC-MS/MS. Analysis conditions of liquid chromatography and mass spectrometry were optimized. Aflatoxins were extracted with methanol-water (1:9, V/V) after corn was grinded into powder, purified through an Oasis HLB cartridge, eluted by methanol and water containing formic acid (0.2%), and determinated by electrospray ionization in positive ion mode and using multiple reaction monitoring. The limits of quantification for aflatoxin B1,B2, G1, G2 and M1 were 0.1μg kg-1,0.1μg kg-1,0.2 μg kg-1,0.3 μg kg-1 and 0.2 μg kg-1, respectively. The correlation coefficients were more than 0.9975 in respective linear ranges, and the recoveries for analytes in different matrixs were 74.6-89.6% and the relative standard deviations (RSD) in different concentration levels were all less than 11.3%. The proposed method was sensitive to meet the requirements for monitoring aflatoxin B1, B2, G1, G2 and Ml in corn.Lastly, we developed and optimized a method for analysis of PFOS and PFOA in drinking water samples. This study was conducted with the aim of assessing the exposure to PFOS and PFOA via drinking water in Liaoning province. The concentrations of PFOS and PFOA were centralized in low concentration region and lower than other areas. The contaminate state in drinking water by PFOS and PFOA was bad for the concentration increased year by year, and the increasing rates of PFOS and PFOA in heavy industry cities were faster than in light industry cities. The contaminate level of the larger residential density cities was worse than other cities.