Field Determination of Organics from Soil and Sludge using Sub-critical Water Extraction Coupled with Solid Phase ExtractionEPA Grant Number: R825368
Title: Field Determination of Organics from Soil and Sludge using Sub-critical Water Extraction Coupled with Solid Phase Extraction
Investigators: Hawthorne, Steven B.
Institution: University of North Dakota
EPA Project Officer: Hiscock, Michael
Project Period: October 1, 1996 through September 30, 1999
Project Amount: $279,935
RFA: Analytical and Monitoring Methods (1996) RFA Text | Recipients Lists
Research Category: Environmental Statistics , Water , Land and Waste Management , Air , Ecological Indicators/Assessment/Restoration
Description:The primary purpose of the proposed investigations is to couple well-known extraction methods for water, solid phase extraction (SPE) and solid phase microextraction (SPME), with subcritical water extraction of soils and sludges to allow field-portable water methods to be applied to contaminated solids.
For water samples, both SPE and SPME can be used to extract and concentrate organics in the field for subsequent analysis (e.g., field-portable GC), but are not applicable to extracting organic pollutants from solid samples. If organic pollutants on soils and sludges could be efficiently transferred to water, both SPE and SPME could be very useful for field determinations of organic pollutants from solids. We have demonstrated that subcritical water (hot water maintained as a liquid by a few bar pressure) is an excellent solvent to quantitatively extract polar and non-polar organics from soils and sludges. Subcritical water extractions can be highly selective; polar organics extract at lower temperatures (e.g., phenols and amines extract at 50 to 100oC), and non-polar organics extract at high temperatures (e.g., 200 to 250?C). By simply heating water under low pressure, solubilities of polar organics increase dramatically, and even non-polar organics such as PAHs can increase solubilities by >106-fold. Preliminary experiments have demonstrated that coupling subcritical water extraction with SPE and SPME can provide an extremely simple, rapid, and inexpensive method to determine organic pollutants found on soils, sediments, and sludges. Quantitative results have been obtained with total sample preparation (including extraction from the solid and SPE or SPME sorption) of ca. 30 minutes. Detection limits of <ppb are easily obtained. Based on these initial results, the proposed investigations will: 1) develop the use of subcritical water coupled to SPE (exhaustive extraction) for the quantitative determination of polar and non-polar organics from soils and sludges; 2) develop the use of subcritical water extraction coupled with SPME (equilibrium extraction) for the rapid and quantitative determination of polar and non-polar organics from soils and sludges; 3) optimize the selectivity of the extractions based on water extraction temperature and on SPE and SPME sorbent selectivity; and 4) demonstrate the best approaches in the field and compare results to conventional EPA extraction and analysis methods.
Based on preliminary studies, it is expected that the proposed investigations will yield an extremely simple (requiring only an extraction cell and oven), inexpensive, and field-portable approach to utilizing SPE and SPME with subcritical water for the extraction and quantitative determination of polar and non-polar organics from contaminated solids and semi-solids.