George C. Clark, Xenobiotic Detection Systems Inc., 1601 E. Geer St., Suite S, Durham, NC 27612, Tel: 919-688-4804, Fax: 919-688-4404, Email: georgeclark@dioxins.com
Andrew C. Chu, Xenobiotic Detection Systems Inc., 1601 E. Geer St., Suite S, Durham, NC 27612, Tel: 919-688-4804, Fax: 919-688-4404, Email: andrewchu@dioxins.com
John D. Gordon, Xenobiotic Detection Systems Inc., 1601 E. Geer St., Suite S, Durham, NC 27612, Tel: 919-688-4804, Fax: 919-688-4404, Email: johngordon@dioxins.com
David Brown, Xenobiotic Detection Systems Inc., 1601 E. Geer St., Suite S, Durham, NC 27612, Tel: 919-688-4804, Fax: 919-688-4404
Mick Chu, Xenobiotic Detection Systems Inc., 1601 E. Geer St., Suite S, Durham, NC 27612, Tel: 919-688-4804, Fax: 919-688-4404, Email: mickchu@dioxins.com
Masafum Nakamura, Hiyoshi Corporation, 908 Kitanoshocho, Omihachiman, Shiga 523-8555, Japan, Tel: +81- (0) 748-32-5001, Fax: +81- (0) 748-32-4192, Email: m.nakamura@hioyoshi-es.co.jp
Hiroshi Murata, Hiyoshi Corporation, 908 Kitanoshocho, Omihachiman, Shiga 523-8555, Japan, Tel: +81- (0) 748-32-5001, Fax: +81- (0) 748-32-4192, Email: LDY03416@niftyserve.or.jp
Michael S. Denison, University of California, Davis, Department of Environmental Toxicology, 4241 Meyer Hall, Davis, CA  95616, Tel: 530-752-3879, Fax: 530-752-3394, Email: msdenison@ucdavis.edu

 For quantitative methods such as high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) and bio-analytical methods such as CALUX^Ò, recovery determinations are very important for toxins such as dioxins. Recovery determinations in HRGC/HRMS are performed by spiking isotopically labeled congeners into the sample prior to extraction, with recovery based on the amount of labeled compound recovered.  Bioassays do not differentiate between isotopically labeled and unlabeled analytes. Recovery determinations in bioassays can be accomplished with a surrogate sample spiked with a radiolabeled congener of dioxin.  We demonstrate here that 1,2,3,4-TCDD, a biologically inactive congener of the dioxin family of chemicals, can be used as an internal spike to determine recoveries of dioxin-like chemicals.  Samples were spiked with ¹⁴C labeled 2,3,7,8-TCDD or 1,2,3,4-TCDD and submitted to extraction and clean up using Xenobiotic Detection Systems, Inc. patent pending XCARB sample clean up method (acid silica column in series with an XCARB column).  The XCARB column is differentially eluted to yield a PCB and PCDD/F fraction.  The 1,2,3,4-TCDD spiked samples were resuspended in toluene containing four PCB injection standards, and recoveries determined by gas chromatograph with electron capture detection or scintillation counter. Average recoveries determined by 1,2,3,4-TCDD with paired samples spiked with ¹⁴C- 2,3,7,8-TCDD indicated that the recoveries determined by the two methods were very similar, 88.5% (± 1.2%) and 87.2% (± 2.4%), respectively.  Recovery determinations were also verified by HRGC/HRMS. This procedure allows for quantitative determination of dioxin-like chemicals in various sample matrices.  Supported by SBIR Grant from NIEHS ES 08372-03. 

Ultra High Throughput Microwave Digestion: A novel Breakthrough Approach for Pressurized Dissolutions

David Barclay, PhD, CEM Corporation, 3100 Smith Farm Rd, PO Box 200, Matthews, NC 28106, Tel: 704-821-7015, Fax: 704-821-5185, Email: David.Barclay@cem.com
Elaine Hasty, CEM Corporation, 3100 Smith Farm Rd, PO Box 200, Matthews, NC 28106, Tel: 704-821-7015, Fax: 704-821-5185, Email: Elaine.Hasty@cem.com
Bill MacLuckie, CEM Corporation, 2679 Romig Road, Gilbertsville, PA 19525, Tel: 610-705-5830, Fax: 610-705-5831, Email: Bill.MacLuckie@cem.com

Microwave digestion over the last 15 years has become a well-accepted technique in use routinely in laboratories around the world. The savings in time and the improvement in digestion quality associated with the elevation of reagent temperature have assumed increasing importance as detection limits for measurement equipment such as ICP and ICP-MS have decreased. However, materials constraints in vessel technology have limited the throughput for pressurized digestions to between 10 and 15 samples per batch, which can offset the savings in digestion time by physically limiting the throughput.

In this paper, a breakthrough in vessel design will be demonstrated which allows a 3 to 4 times increase in throughput per batch for pressurized microwave digestion. Novel temperature sensing methodology will be discussed allowing a ‘connection free’ system with full temperature control of up to 40 pressurized digestions simultaneously.

Data will be presented for dissolutions at temperatures up to 200C of environmental reference materials, organic reference materials and ‘real world’ samples showing within and between batch variation for this novel approach. Particular attention will be given to recoveries of the traditionally ‘volatile’ elements such as As, Se and Hg.

Further results will be presented showing that optimization of an important design criteria – the ‘aspect ratio’ of the vessel - allows a full carousel of 40 samples to achieve regulatory methodologies such as EPA 3051 without requiring a significant increase in available energy.

Analysis of 1, 4-Dioxane – Technical Challenges and Observed Results

James F. Occhialini, James Todaro, Scott Enright, & Joseph Watkins, Alpha Analytical Labs, Eight Walkup Drive, Westborough, MA 01581, Tel: 508-898-9220

The compound 1, 4-Dioxane has been the subject of increasing concern regarding its potential presence as a groundwater contaminate.   Dioxane has many industrial uses, most notably as a stabilizer for chlorinated solvents, raising the specter that it may be present at chlorinated solvent sites.  The degree to which dioxane contamination is prevalent in the environment is unknown because historically, there has been very little monitoring for this compound.  The compound forms an azeotrope with water, making it a highly mobile contaminate that is also difficult to remediate.  The same physical characteristics that make it a threat to groundwater also present many analytical chemistry challenges, particularly concerning the analytical sensitivity required to address 1, 4-dioxane at risk-based concentration levels.  In this paper, the authors modified Methods 8260B and 8270C to maximize the analytical performance for this compound.  Accuracy, precision and sensitivity data is presented for each method with recommendations for obtaining the best performance from each method. 

A Revaluation of Antiquated Partitioning Coefficients and their Affect on Soil Clean-up Levels

Maryann H. Sapanara, GZA GeoEnvironmental, Inc., One Edgewater Dr., Norwood, MA 02062, Tel: 781-278-5836, Email: msapanara@gza.com
James J. Clark, P.E., GeoEnvironmental, Inc., One Edgewater Dr., Norwood, MA 02062, Tel: 860-875-7655, Email: jclark@gza.com
Albert J. Ricciardelli, P.E, LSP, GeoEnvironmental, Inc., One Edgewater Dr., Norwood, MA 02062, Tel: 781-278-3831, Email: aricciardelli@gza.com
Kathryn Walsh, GZA GeoEnvironmental, Inc., One Edgewater Dr., Norwood, MA 02062, Tel: 781-278-4700, Email: kwalsh@gza.com

Soil cleanup levels are often set using partitioning modeling to predict contaminant concentrations leaching into groundwater.  This modeling typically uses literature values for partitioning coefficients which are based on historic studies and theoretical relationships.  An indirect, though critical, parameter affecting the partitioning calculation is the efficiency of the soil sampling/analytical method used.  The more efficient the method, the lower the partitioning coefficient needs to be to accurately reflect the amount of contaminant that will actually leach.  A recently developed soil sampling method (Method 5035) dramatically improves the efficiency of soil analyses for VOCs (by as much as an order of magnitude).  This in turn has affected the development of soil cleanup levels. 

In 1994, at a Connecticut Superfund Site, soil cleanup levels were established via leach testing/partition modeling of samples collected using then current methodology.  GZA implemented SVE at the site; a few years later, the data indicated that we were approaching the cleanup objectives.  However, soil samples collected using Method 5035 indicated significant residual concentrations – greater than what was detected prior to remediation.  It was suspected that these increased concentrations were an artifact of the sampling methodologies employed.

To assess the effect of using Method 5035 on the detected soil concentrations and required cleanup levels at the site, we collected soil samples and analyzed them via a modified (to limit losses during sampling and analysis) Synthetic Precipitation Leaching Procedure (SPLP) and Method 5035/8260.  A soil-water partitioning coefficient (K_d) was then calculated for each set of samples.  Using a multivariate statistical analysis and a one dimensional steady state flow/finite difference transport model we were able to demonstrate that the leachable concentrations in soil were not significant (relative to groundwater goals).  These data were subsequently used to revise the site-specific goals for VOCs in soil by an order of magnitude.

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