Studies On The HPLC-MS/MS Method For Determination Of Carbamate Pesticides In Grains

N-methyl carbamates are one kind of the most widely used pesticides nowdays, due to their broad specum of activity, relatively rapid disappearance, effectiveness and selectivity. With the inscreasing use of the pseticides both in amount and in spectrum,more atttention is given to residues in crops and their harms on human health and the environment. Many countries have established the Mamxium Residue Limits of carbamates for grains, making our country faced with more technical barriers of grain export. Therefore, it is urgent and significant to establish a simple, rapid and selective method to determine carbamate rsidues in grains. High Performance Liquid Chromatography-Tandem Mass Spectrometry as an efficient analytical technology, is developing very fast these years. It can achieve excellent selectivity and sentivity. With its powerful qualitative ablity and high accury, it has become the most prefered technology for the ultra-trace analysis of pesticides in complex matrice. The present work majorly focuses on the study of HPLC-MS/MS method for the determination of nine carbamate pesticides in grains. The carbamates were extracted with acetonitrile, cleaned up with alumina-N solid phase extration (SPE) cartridges, and determined by HPLC-ESI(+)-MS/MS.There is carbonyl group in the functional group of carbamates, and most of the carbamates have a phenyl group. Based on the basic viewpoint of "selective intercourse between molecules", if the substance which needs to be separated has a similar structure with the stationary phase, it can be better separated because of its enhanced intercourse with the stationary phase. So, we choose benzenesulfonyl,which has a a similar structure with the carbamates, as a specific functional group and synthesized a stationary phase which contained benzenesulfonyl group. The chromatographic performance of the stationary phase was primarily evaluated.In chapter 1, the research status of carbamate residues analysis was summarized. The extraction, clean-up and determination methods of carbamates in various matrix were presented and evaluated in detail. Based on some literature reviews, acomprehensive summary was made concerning the origins and mechanisms of matrix effects, its consequences and the possible ways of compensating it.In chapter 2, a method for the determiantion of nine carbamate residues in grains by HPLC-MS/MS was studies and established. The influences of extraction solvent and clean-up means on the recoveries of the pesticides were studied;the mobile phase compisition on the seperation and mass spectrometric signal response of the pesticides was examined;the influence of different mass spectrometric conditions on the sensitivy of the method was also studied. The results showed that acetonitrile had the best extraction efficiency on the nine carbamates;alumina-N SPE cartridge could effectively eliminates most of the impurities from the crude extract;the mobile phase composed of methanol-ammonium acetate solution (5mmol/L) could seperate most of the pseticides and the pseticides showed good mass spectrometric signal responses in it.In chapter 3, the consequences of "matrix effects" on the analytical results were evaluated, results showed that the existence of matrix effects had to a high extent an adverse effect on different aspects of the method, such as sensitivity, repeatability, quantification and so on. Different ways of compensating matrix effects were also studied. Results demonstrated that: through modifying mass spectrometric conditions, improving retention and seperation, through a more extensive sample clean-up, matrix effects could be sharply reduced, the employ of matrix-matched calibration in quantification could effectively compensate the effects of matrix components.In chapter 4, a benzenesulfonyl bonded phase was synthesized and characterized with FT-IR and Scan Electron Microscope. Its chromatographic performance was primarily evaluated under mobile phase of methanol-acetic acid solution(pH=4.5). Results showed that the bonded phase had a weaker retention towards polar substances, but its separation ability and stability remained to be improved.