Supercritical fluid extraction and clean-up with temperature fractionation: Application to determination of polychlorinated dibenzo-ρ-dioxins
✍ Scribed by Zhuang Miao; Zhouyao Zhang; Janusz Pawliszyn
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- English
- Weight
- 499 KB
- Volume
- 6
- Category
- Article
- ISSN
- 1040-7685
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✦ Synopsis
Abstract
Supercritical fluid extraction (SFE) and clean‐up with neat carbon dioxide (CO~2~), selective sorbents and high extraction temperature was developed as a sample preparation method. The effects of temperature and pressure on SFE efficiencies were investigated by spiking a polychlorinated dibenzo‐ρ‐dioxin (PCDD)/polychlorinated biphenyl (PCB) standard mixture onto a Florisil™ adsorbent and extracting these compounds at different temperatures and pressures with neat CO~2~. High extraction temperatures and pressures were found to increase the extraction rate and efficiency. PCDDs were quantitatively extracted from Florisil™ only when the temperature was raised to 200°C and the pressure was 9000 psi. PCBs were efficiently extracted at low temperature and pressure, such as 50°C and 2000 psi. Fractionation of PCBs from PCDDs with Florisil™ using CO~2~ was accomplished by first quantitatively recovering all of the PCBs at 3500 psi and 80°C and then the dioxins at 9000 psi and 250°C.
The determination of PCDDs in fly ash was carried out by spiking the fly ash extract (obtained after 80 min extraction at 250°C and 9400 psi using neat CO~2~) onto Florisl^TM^, followed by the clean‐up step outlined above. This step produced much cleaner chromatograms compared to direct extraction. The modifier‐free high temperature SFE method produced comparable results to 20 h Soxhlet extraction of fly ash, but it was shorter by an order of magnitude.