The Study On Single Drop-microextraction In Analysis Of The Residue Of Organochlorine Pesticides

The first step of retention analysis is to extract and clean up the trace pesticides. It has a direct effect on the accuracy of results. At present, the common methods, for example, Thin-film Chromatography, Gas Chromatography, Liquid Chromatography and Gas Chromatography-mass spectrum, require analyzing purer samples. The complicated matrixes will interfere with the retention analyses and damage the instruments. So sampling, concentration and purification are important preparation steps in the retention analyses of pesticides. Liquid-liquid extraction is a typical and traditional method of preparation that deals with complicated samples. Now it is still used in 70% of retention analyses of pesticides. Recently, lots of new techniques of preparation have appeared, such as Acceleration Solution Extraction (ASE), Microwave Assisted Extraction (MAE), Supercritical Fluid Extraction (SFE), Solid Phase Extraction (SPE), Solid Phase Microextraction(SPME), Liqud-Liquid Microextraction(LLME). These techniques have respective advantages and shortcomings. This thesis adopts the method of Single Drop Extraction to analyze organochlorine pesticides in water and honey samples and compares it with Liquid-Liquid Extraction and Solid Phase Microextraction.In the first place ,this thesis summarizes the development of One Drop Extraction in the field of chromatography and studies the possibility of the joint use of Single-Drop Extraction-Gas Chromatography-ECD to detect in water eight mixed organochlorine pesticides, namely, -666, -666, -666, -666, P, P' -DDE, P, P' -DDD, O, P' -DDT, P, P' -DDT. Factors that affect the efficiency of One Drop Extraction such as extractive solvents, extractive time, extractive temperatures, stirring speed, solvent volume, water sample volume and ionic strength are optimized. Under these conditions, the linear range of seven target samples is from 0.04 to 4.0ng/ml except for P,P' -DDD, with its linear range from 0.4-4.0 ng/mL and the relative coefficient is from 0.9976-0.9999.The recoveries arefrom 77.6%to 104%, and the standard deviations are from 1.3% to 13.1%. The LODs of 666 and DDT are 20.2ng/L and 121ng/L separately. Compared with LLE and SPME, SPME is highest in accuracy and precision. Though LLE has the lowest LOD, the optimized SDE is fast and higher in linearity and requires little solvent. Though the LOD of SDE is higher than that of LLE, it can meet the demands of the national standards. So the SDE-GC- ECD method established in this experiment is a fast, economical and reliable way to detect the residue of organochlorine pesticides in water samples.Secondly, this thesis studies the possibility of the joint appliance of Single-Drop Extraction-Gas Chromatography-ECD to analyze and detect eight mixed organochlorine pesticides in honey samples. Under optimized lab conditions, the linear range of seven target samples is from 0.1 to 10 ng/ml except for P,P' -DDD, with its linearity ranging from 0.4-10 ng/mL and the relative coefficient is from 0.9974-0.9999. The recoveries are from 81.4% to 93.9%, and the standard deviations are from 2.5% to 22.8%. The LODs of 666 and DDT are 41ng/L and 141ng/L separately. Compared with SPME, the optimized SDE, when used to detect residue of organochlorine pesticides in honey samples, can not only dismiss the influence of background and the purification process, but also lower the LOD of DDT. This method can also reduce cost. Although the accuracy and precision of the method are a bit lower than those of the SDE or the SPME, they are within the permitted ranges. So the SDE-GC- ECD established in this experiment in detecting residue of organochlorine pesticides in honey is rapid, inexpensive and reliable.