Subcritical Water Extraction Of Some Organic Chlorine Pollutants In Soil

Sample preparation techniques play a key role in environmental analysis, especially in the determination of trace or ultra-trace amount of persistent organic pollutants (POPs) in the environmental samples. Recently development of sample preparation methods concerning organic solvent-free or less volume of organic solvent consumption is in the edge-of-state of this field, due to the concern of the hazard of the organic reagent disposal to the environment. In this paper, a new environmental sample preparation technique, subcritical water extraction, has been studied and applied to the extraction of some kinds of trace organic pollutants from soil. The extraction of chlorophenols from soil by subcritical water extraction coupled with solid phase extraction (SBWE-SPE) has also been studied.1) The optimization of operation parameters of GC-ECD was studied for 2,4-dichlorophenol (2,4-DCP), 4-chlorobiphenyl (4-PCB) and hexachlorobenzene (HCB). Simultaneous determination of 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol(PCP) by GC-ECD has been studied too. 2) Three organochlorien compounds with different polarity, i.e., 2,4-DCP, 4-PCB and HCB, had been selected extraction by subcritical water. Under the relative low extraction temperature (125℃), the main extracted compound is 2,4-DCP, and 4-PCB and HCB are quantitative extracted under 250℃. The optimum subcritical water extraction conditions for HCB in the soil sample are extracting 75 min with 4mL water under 250℃. This method had been applied in the determination of HCB in the real soil sample. The result was agreement with it by standard method.3) The operation parameters of subcritical water extraction of three chlorophenols were optimized. The optimized operation condition is: the pH of solvent is 9, volume of extraction water is 20mL, temperature is 130℃, extraction time is 45 min. Under this condition, the recoveries of three kinds of chlorophenols are in the range of 78~98%.4) With ACF as solid-phase, the chlorophenols has been simultaneous extracted by static SBWE coupled with solid phase extraction (SPE). It's a good approach to solve the problem that often occurred in the off-line SBWE-SPE, which is the return of organic compounds to the soil when the polarity of water increases dramatically as the temperature of the extraction cell decreases.