Optimization Of Pretreatment Method On Semi-volatile Organic Compounds In Groundwater

Groundwater is a valuable source of water supply and occupies a pivotal positionin China. However, with the rapid increase in population and the high-speedeconomic and social development, organic pollution of groundwater in China isincreasingly prominent, and organic pollutants in groundwater caused great harm tohuman health. Therefore, strengthening monitoring of organic pollution ingroundwater is of great significance to groundwater quality monitoring and pollutionprevention, and can also provide a scientific basis for the formulation of relevantstandards.For determination of trace organic compounds in groundwater, the accuracy andreliability of the results depends on the pre-treatment process. In this thesis,semi-volatile organic pollutants were selected as the object of this study, throughcomparison of two pretreatment methods, recovery efficiencies were discussed usinggas chromatography-mass spectrometry (GC/MS) between liquid-liquid extractionand solid phase extraction. The goal is to get an appropriate pre-treatment methods forSVOCs in groundwater.A liquid-liquid extraction method for multi-component semi-volatile organiccompounds was established in this thesis and a comparative study was conductedamong controversial extraction methods. The results showed that pH adjustmentorders had a significant impact on liquid-liquid extraction method formulti-component semi-volatile organic compounds, and to adjust pH to acidic (pH<2)first will get a higher extraction efficiency than to adjust to alkaline (pH>11)first.The recoveries of acids, base and neutrals and supplements and pesticides were10.7%,5.9%,12.9%higher respectively, while the difference between precisions of the twogroups was not significant. A separate study was conducted given the worse recovery of acidic organiccomponents. Successive experiments using response surface methodology to optimizethe liquid-liquid extraction and solid phase extraction method for the investigation ofthe precision and recovery were conducted, and results showed that the optimalliquid-liquid extraction of phenolic substances were when salting dosage was30g,the oscillation frequency was267rpm, and oscillation time was2min. Averagerecovery of pH1was26.3%,8%higher than the average recoveries of pH4with18.3%. Thus low pH value is more conducive to the improvement of recovery rate,and precisions between the two different pHs were not significant. Extraction ofphenolic compounds was also studied in this thesis by solid phase extractiontechnology, and was compared with the optimal liquid-liquid extraction method.Results showed that average recovery of solid-phase extraction was46.0%with RSDof13%, and the average recovery of optimal liquid-liquid extraction was31.6%witha precision of25%. This is because the disk used in solid phase extraction has a goodselectivity of phenolic substances, and it has a more ideal recovery and precision thanthe liquid-liquid extraction method.This research provides a reliable analytical method for monitoring oganicpollution in groundwater, and lays a solid theoretical foundation to further carry outgroundwater organic contamination investigation and treatment.