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New Method for Analyzing Organic Chemicals in a Wide Array of Samples
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Introduction
This field is an area that has been studied as a means to extract volatile
chemicals from most media. This approach was initially investigated for
a group of analytes that are commonly known as volatile organic compounds
(VOCs) or sometimes as volatile organic analytes (VOAs). The VOCs include
some of the most common organic compounds that are used by industry and
include common solvents and petroleum constituents.
Vacuum distillation is a technique that uses a vacuum to extract analytes from a sample. A condensing column is used in the technique to condense water that may also be present in the sample. A cryogenically cooled trap (cryotrap) is used to condense the compounds of interest. During a vacuum distillation procedure a sample is evacuated to a low pressure vaporizing volatile compounds, including water. The condenser column retains vaporized water and those vaporized compounds that are not condensed in the column are frozen in the cryotrap. The extract retained in the cryotrap are then transferred (sweeping the cryotrap with a carrier gas while heating the cryotrap) to another instrument for detection and quantification of the components in the extract. An overview of the vacuum distillation chemistry is in the training presentation, An Overview of SW-846 Method 8261 Chemistry , and more elaborate explanation of the technique is available in publications.
Apparatus
Vacuum distillation uses a specialized apparatus. This apparatus has been
developed and patented by the EPA. Through
the Federal Technology Transfer Act this invention has been made available
for commercialization. Available
vendors 
for this instrumentation are being evaluated.
Application of vacuum distillation
The use of vacuum distillation as a tool to extract analytes from a sample
requires a protocol. This protocol describes conditions of its use and
an evaluation of results. Two methods of operation have been devised for
inclusion in RCRA's methods manual, SW-846. The first method (5032) describes
the conditions to extract volatile organic compounds and analyze the extract
according to a determination method, such as method 8260. Method 8261
combines methods 5032 with a determination routine that allows for a wider
suite of analytes with quality controls consistent with vacuum distillation.
Superfund investigates vacuum distillation
analytical method for use at Superfund sites
Superfund is currently conducting a study of method 8261 for use as a
contract method to support site investigations. Four Superfund facilities
are involved in an inter-laboratory evaluation which is nearing completion.
Preliminary results were presented by Superfund at the 20th National Environmental
Monitoring Conference (NEMC 2004) in Washington, D.C. Based upon these
preliminary results Superfund intends to include the method as a non-RAS
Contract Laboratory Program option in the near future. View
the NEMC presentation .