Grantee Research Project Results
1997 Progress Report: Field Determination of Organics from Soil and Sludge using Sub-critical Water Extraction Coupled with Solid Phase Extraction
EPA Grant Number: R825368Title: 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: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 1999
Project Period Covered by this Report: October 1, 1996 through September 30, 1997
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
Objective:
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 (SWE) of soils and sludges to allow field-portable water methods to be applied to contaminated solids.Progress Summary:
Primary efforts in Year 1 were to couple SPME with subcritical water extraction of soils and sediments. Methods were developed which utilize a very simple subcritical water extraction cell (no pump required) which costs $6. SPME analysis was performed on the resultant water sample to determine the concentration of the pollutants in the original soil. Subcritical water extraction conditions and calibration methods were developed which allowed quantitative and/or semi-quantitative determinations of polar organics (e.g., aromatic amines), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) without the use of any organic solvents.Initial efforts in Year 1 to couple solid phase extraction discs with a simple subcritical water extraction cell have demonstrated that this approach is also feasible. Finally, the use of hydrolysis/derivatization reactions during subcritical water extraction coupled with SPME and/or SPE discs to determine ionic organics (e.g., acid herbicides) was also demonstrated to be feasible.
Accomplishments and Research Results:
A. Coupled Subcritical Water Extraction with SPME (Primary Emphasis for Year 1):A general approach for determining the concentration of moderately- and non-polar organics on solid samples was developed which uses a stainless steel extraction cell loaded with the sample, a few mL of water, and a small gas headspace. Extraction of the organics was performed by simply placing the loaded cell in an oven and heating (e.g., to 250?C) for 15 to 60 minutes. The cell was then cooled and the extracted organics were determined by exposing the extractant water to a SPME needle for 15 minutes followed by GC analysis.
The subcritical water extraction step effectively transfered the analytes to the water phase, but non-polar organics (e.g., PAHs and PCBs) repartitioned to the solid sample after the extraction cell was cooled. For more polar compounds (e.g., aromatic amines), the analytes remained in the water after extraction. Therefore, calibration was performed as for normal SPME analysis; i.e., using water-based standards. For PAHS, quantitative calibration was performed by spiking the sample with deuterated PAH internal standards to account for the sample/water and water/SPME partitioning. For PCBs, congeners 103 and 169 (which do not occur in PCB-contaminated samples) were added to the sample prior to subcritical water extraction and SPME analysis. The coupled subcritical water/SPME method gave good agreement with conventional organic solvent extraction methods for alkyl benzenes, aromatic amines, and PAHs from soil samples. However, the method for PCBs was not as accurate, and typically gave results for each PCB congener within 2x of the concentration determined with conventional methods. These results occured because the two PCB internal standards did not precisely mimic the soil/water and water/SPME equilibria for all PCB congeners. However, the subcritical water extraction/SPME procedure gave very good agreement for total PCBs with conventional extraction methods.
It should be noted that the apparatus used for the subcritical water/SPME determinations of alkyl benzenes, aromatic amines, PAHs, and PCBs was very simple, small, and field-portable. All determinations were performed with no organic solvents and with extraction times of 15 to 60 minutes.
B. Coupled Subcritical Water Extraction with SPE Discs:
Coupled subcritical water extraction/SPME (discussed above) depends on being able to calibrate for the soil/water and water/SPME equilibria which occur. In contrast, we hope to develop methods which quantitatively collect analytes from the water during the subcritical water extraction step. As with the water/SPME method, a major goal is to keep any methods very simple and field-portable. In Year 1, we have developed an initial approach which simply places the soil and an SPE disc in a stainless steel cell (like that used above). Preliminary results demonstrate that (1) Empore Teflon-based discs are stable under the 250?C subcritical water conditions, and (2) PAHs efficiently transfer ( 90%) to the disc from soil samples.
C. Incorporating Derivatization Reactions:
Subcritical water extraction can be used to aid in hydrolysis or other useful analytical reactions. (Of course, analytes sensitive to hydrolysis may also be destroyed during subcritical water extraction.) Initial investigations have been successful using the ability of subcritical water to hydrolyze natural pyrethrins (widely-used natural insecticides) to pyrethric acid, which can then be determined using SPME and GC. We have demonstrated that acid herbicide esters (e.g., 2,4-D) on soil can be converted to their free acid forms (a step required by conventional analysis methods) during subcritical water extraction, then collected on anion-exchange sorbent discs for derivatization and subsequent GC analysis.
Future Activities:
During Year 2, the primary emphasis will be placed on coupling subcritical water extraction with SPE sorbents as described above. In addition, the initial derivatization approaches (discussed above) with both SPME and SPE discs will be further developed and evaluated.Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 15 publications | 6 publications in selected types | All 6 journal articles |
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Hageman KJ, Mazeas L, Grabanski CB, Miller DJ, Hawthorne SB. Coupled subcritical water extraction with solid-phase microextraction for determining semivolatile organics in environmental solids. Analytical Chemistry 1996;68(22):3892-3898. |
R825368 (1997) R825368 (Final) |
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Hawthorne SB, Grabanski CB, Hageman KJ, Miller DJ. Simple method for estimating polychlorinated biphenyl concentrations on soils and sediments using subcritical water extraction coupled with solid-phase microextraction. Journal of Chromatography A 1998;814(1-2):151-160. |
R825368 (1997) R825368 (Final) |
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Supplemental Keywords:
organic analysis, field methods., Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, Physics, Environmental Chemistry, Chemistry, Monitoring/Modeling, water extraction, field portable monitoring, contaminated sediment, gas chromatography, PAH, organics, soil, hydrocarbons, sludge, solid phase microextraction, sucritical waterProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.