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Last Update: 01/31/00

Identification and Quantification of Semi-Volatiles In Soil Using Direct Thermal Desorption

INTRODUCTION

New methods are needed for the analyses of semi-volatile organic compounds from complex matrices such as: soils and sludge from hazardous dump sites and environmental spills. Conventional methods incorporate solvent extraction, which is both time-consuming and requires the use of large quantities of organic solvents. Not only is there concern over the safe handling of these toxic and carcinogenic solvents, but their safe disposal is becoming increasingly expensive and troublesome. In addition, during the extraction process, the solvent extractions must be concentrated. In this concentration process, the solvent is usually evaporated and exhausted in a laboratory fume hood, thereby contributing to an additional environmental problem. Other techniques, as Super Critical Fluid Extraction (SFE) and Thermal Desorption, have recently become acceptable for the extraction of semi-volatiles from soil and other solid matrices (1,2 & 3). SFE still requires a small amount of solvent and about 1 hour for sample preparation. In this article, a new technique encompassing the Short Path Thermal Desorption System interfaced to a GC/MS and using the Direct Thermal Desorption Technique is used to identify and quantify the semi-volatile organic compounds in solid soil matrices. The Polynuclear Aromatic (PNA) and Polychlorinated Biphenyl (PCB) semi-volatiles are studied in this article to determine the feasibility of using this method for the direct thermal extraction and analyses of these compounds from solid soil matrices. Solid soil samples between 1 and 100 milligrams are placed directly into the glass lined stainless steel desorption tube on top of a glass wool plug; the semi-volatiles are thermally extracted directly into the GC injection port. No solvent extraction or other sample preparation is required. Deuterated internal standards are added to each soil sample for the quantification of the sixteen standard polynuclear aromatic (PNA) compounds specified by EPA method 8275, the polychlorinated biphenyl's (PCB) as well as other semi-volatiles. Accurate identification and quantification of these semi-volatile organic compounds down to the part per billion (ppb) level in less than 100 milligrams of soil are achievable with this technique.

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