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Gas chromatographic analysis of organochlorine pesticides - Master's thesis - Dissertation
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1. **Overview**
Modern agriculture heavily relies on pesticides to protect crops from pests and diseases. With increasing demand for food production, the use of various types of pesticides has become widespread. However, this heavy usage comes with serious environmental and health consequences. Pesticides can contaminate soil, water, and air, and residues often remain on food products, posing risks to human health. The trade-off between increased agricultural productivity and environmental safety remains a critical issue today.
In many regions, especially where large-scale farming is common, pesticide residues are frequently found on fruits and vegetables. A recent study conducted in the U.S. and the UK revealed that 73% of tested food crops did not show detectable pesticide levels, but certain crops like fruits and vegetables were more affected. After harvest, some produce is stored for long periods before reaching consumers, which increases the need for preservatives—often including fungicides and other chemical treatments. As a result, it's common for both the outer skin and inner flesh of these foods to contain residual pesticides.
Organochlorine pesticides, such as BHC and DDT, have been widely used in the past. Although China banned the production of BHC and DDT in 1983, their persistence in the environment remains a concern due to their slow degradation. Dicofol, another organochlorine compound, is still used in some agricultural practices, particularly on fruit trees and cotton. Its breakdown product, DDE, is structurally similar to DDT and carries comparable toxicity. This means that even decades after their initial use, these chemicals can still be found in crops, making the detection of pesticide residues an essential step in ensuring food safety.
Gas chromatography is one of the most effective methods for analyzing pesticide residues due to its high sensitivity, selectivity, and speed. According to GB/T 17332-1998, the GC7800 gas chromatograph manufactured by Beijing Purui Analytical Instrument Co., Ltd. has been successfully used to measure organochlorine pesticide residues in tea, delivering reliable and accurate results.
2. **Experimental Setup**
Instrument: GC7800 Gas Chromatograph (Beijing Purui Analytical Instrument Co., Ltd.)
Column: OV-1701 or SE-54, 30m × 0.32mm × 0.5μm (Dalian Zhonghuida Scientific Instrument Co., Ltd.)
Detector: Electron Capture Detector (ECD)
Column Temperature: 200°C
Injector Temperature: 220°C
Detector Temperature: 220°C
Carrier Gas: High-purity nitrogen, 8 mL/min
Tail Gas: 16 mL/min
Injection Volume: 1 μL
This setup ensures precise and consistent analysis of pesticide residues, making it a valuable tool in modern agricultural and environmental monitoring.