Analytical Method And Its Application Of The Organochlorine Pesticide Residue In Soils

A threat from organochlorine pesticide residue (OCPs) has been paid more attention at recent years. In this thesis, studies are mainly focused on the analytical methods of OCPs in soil samples. The trace analytical techniques for 18 OCPs species in soil samples are developed including sample preparation methods of microwave extraction (MWE) combining with Florisil solid phase extraction (SPE) purification, and the concentrations of OCPs in soils are analyzed by gas chromatography with electron capture (GC-ECD) and confirmed by gas chromatography-mass spectrometry (GC-MS).For the experimental conditions of extraction, a mixture slovent of acetone/hexane (1: 1, v/v) was used as an optimal extraction agent for MWE. Through using the orthogonal experimental design method, the conditions of MWE are optimized. The results show that the optimal conditions are as following as 15min extraction time, 120℃extraction temperature under the conditions of solvent in 30mL, the recovery rates of OCPs are almost all optimal and satisfied. There was no significant difference between the effects of MWE and soxhlet extraction (SE). A comparison of the SE and MWE shows that 100 mL organic solvent extract for 16 h was used by SE whereas only 30 mL of organic solvent extract and 15min used by MWE. Moreover, the method of MWE could treat 10 samples in a beach time, which show that the method of MWE was much time saved with a high efficiency.The purification technique of SPE has an advantage of operating simply, saving solvent and automation of the samples batch treatment. Experimental shows that SPE purification has more applicability than sulfonation for purified more OCPs species. Then, A comparison of purification techniques by Silica gel (Si) and Florisil SPE are studied. The extraction was purified with acetone/hexane (1: 9, v/v) as eluent solvent for Si and Florisil columns, and 18 OCPs could be eluented completely by 10mL and 6 mL eluent solvent respectively; the recovery rates by Si and Florisil columns were in the ranges of 83.12%~117.42%, 85.18%~114.22%, respectively.These two methods both have good purification effect. Experiment shows that the time cost for Florisil SPE purification is one time shorter than that of Si SPE purification. Consequently,Florisil SPE purification is used as the best purification method in this thesis. The analytical methods for OCPs were also studied. Analytical parameters of GC-MS and detection conditions of GC-ECD are optimized, and the performance parameters of the two instruments are compared. GC-MS is with obvious superiority in qualitative detection, which can identify the compounds structure exactly. To overcome the highly qualitative limitation of GC is only depended on retention time. The instrumental detection limit (IDL) of 18 OCPs detected by GC-MS were ranged within 0.060～0.89μg/kg whereas the method detection limit (MDL) were ranged within 0.16～1.86μg/kg; the recovery rates of 18 OCPs with spike levels of 5, 20, 40μg/kg in the blank soil samples were within 74.48%～118.90%, and the relative standard deviations (RSD) were within 4.40%～15.93%. The IDL of 18 OCPs detected by GC-ECD were ranged within 0.0090~0.088μg/kg whereas the MDL were ranged within 0.14～1.69μg/kg; the recovery rates of 18 OCPs with spike levels of 5, 20, 40μg/kg were within 71.20%～116.40%, and RSD were within 1.17%～9.91%. It shows that the IDL of OCPs by GC-ECD is lower than that by GC-MS, and the precision of OCPs by GC-ECD is better than that of OCPs by GC-MS, In this thesis, external standard method of GC-ECD was used in quantitative analysis of unknown soil samples,and the results were confirmed by SIM mode of GC-MS.The analytical methods established above were applied to measure the trace OCPs in soil samples in the farmland located in suburbs, Langfang, and the quality assurance and quality control are also established in analytical process. Result shows that the analytical methods has many advantages including simple and rapid, solvent saving, precise and high efficiency, which are suitable for measuring the OCPs in environment soil samples.