Comparison of supercritical fluid extraction with Soxhlet extraction for analysis of DDT in soils

Comparison of supercritical fluid extraction with Soxhlet extraction for analysis of DDT in soils

Barber's Orchard (N.C.)

DDT (Insecticide) -- Measurement

Supercritical fluid extraction

Miyakawa, Wakana

2005

Bacon, J. Roger

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The efficiency of supercritical fluid extraction (SFE) for the isolation of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), 1, 1-dichloro-2,2-bis(pchlorophenyl) ethane (DDE), and dichlorodiphenyldichloroethylene (DDD) from soils was investigated by comparing SFE with the Soxhlet extraction method. Soils were spiked with the target chemicals (DDT, DDE, and ODD). These samples were extracted with modified C02 (1 mL of methanol added directly to the sample) at 60�C and 150 atm for 10 minutes in the static mode and 20 minutes in the dynamic mode followed by a second cycle (10 min static mode and 20 min dynamic mode) at 65�C. The correlation between temperature and extraction efficiency was observed for all target chemicals. In contrast, the effect of pressures on extraction efficiency was not observed. Overall average recoveries of the 3 target chemicals were greater than 88%, and the overall average relative standard deviation (RSD) was 9.04%. Secondly, a uniform spiked soil was used to compare the extraction amount of target chemicals between SFE (n=5) and Soxhlet extraction (n=3). It was found that the quantity of DDT was extracted more by Soxhlet extraction and DDD was extracted more by SFE. DDE was extracted almost the same amount by both extraction methods. Lastly, real soils were repetitively extracted by SFE and Soxhlet extraction. Soils were obtained from Barber Orchard in Waynesville, North Carolina, which was contaminated with six different pesticides (lead arsenate, DDT, lindane, DDD, endrin, and dieldrin). To quantitate the target chemicals levels, a high-performance liquid chromatographic (HPLC) system was used. The soil was collected as core soil samples and separated into 3-cm depth soil fractions. The cost, total analysis time, and efficiency of the SFE and Soxhlet extraction methods have been compared. For a single extraction, SFE required $0.46 and 80 minutes, while Soxhlet extraction required $3.26 and 22 hours. Statistical comparisons of results from the two methods were performed.

2014-04-28

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