Studies On The Determination Of Pesticide Multi-Residues In Foods By Gas Chromatography

Chemical pesticides will gradually degrade and their toxicity will disappear due to the decomposition reaction of sunlight in environment, microbe in soil, enzyme in plants and hydrolysis in water after their application. However, pesticide residues still remain in the crops, the soil and the groundwater and constitute a health risk because of their residual toxicity. To protect consumers' health, many countries have restricted the usage of these deleterious chemicals and have established maximum residue levels (MRLs) to control their levels in foods. In the process of analyzing pesticide residues, sample's preparation is very complicated because there is a very small amount pesticide residued in samples. Therefore, requirement of method's accuracy and precision are not very high, fortified sample recoveries can be between 80% and 120%. But the method's sensitivity must be very high in order to be able to determine trace pesticide. Five chapters are consisted of the paper:In the first chapter, the new development was focused on the reports which were evolved over the last 5 years. The determinations of insecticides, herbicides, miticides, etc. in foods, plants, human body fluids were reviewed. The several methods used in sample preparation, the applications of fixed-fluids and detectors were compared. In the meantime, the developing trends of pesticides residual analysis were discussed.In the second chapter, a simple, rapid, economical and efficient method was described for the determination of residues of fenpropathrin in apple and eggplant with spring quartz capillary column. The mixture of cyclohexane-acetone was used to extract samples, following by a cleanup technique on a column packed with Florisil using the mixture of cyclohexane-petroleum ether to elute the samples. The samples were analyzed by gas chrornatography-electron capture detector (GC-ECD) with detection limit of (LOD) 0.017mg /kg.In the third chapter, a method based on liquid-liquid extraction following by gas chromatography with flame-photometric detector (FPD) was developed for determining 9 organophosphorus pesticide residues in cereal and kidney bean samples. The preparation of samples and the procedure of eliminating water were studied. It was shown that good separations were obtained using a fused-silica capillary column DB-1701 by the optimized temperature program. The process was rapid, and the method was sensitive and practical.In the fourth chapter, a simple and rapid method was described for the determination of 20 kinds of organochlorine pesticide and pyrethroid residues in vegetable and fruit. The mixture of cyclohexane-acetone was used to extract the samples, followed by a cleanup technique on a column packed with Florisil using the mixture of cyclohexane-petroleum ether to elute the samples. The samples were concentrated by rotary vacuum evaporator and analyzed by gas chromatography-electron capture detector (GC-ECD).In the fifth chapter, a method based on homogenized extraction at high speed and cleanup on column packed with Florisil was used to determine the residues of 12 organophosphorus pesticides in Ginkgo Biloba leaves by gas chromatography with flame-photometric detector (GC-FPD).