Environmental Engineering Reference
In-Depth Information
4 Sampling and Laboratory
Analysis for Solvent Stabilizers
Thomas K.G. Mohr
Investigators characterizing solvent-release sites may overlook 1,4-dioxane because (1) they are not
required to look for it and (2) they do not i nd a compelling reason to sample for chemical com-
pounds that are not among the known or regulated threats to drinking water and human health.
Awareness of the widespread occurrence of 1,4-dioxane as a co-contaminant of methyl chloroform
is still growing, but is not yet widespread; consequently, most site investigators do not direct the
laboratory to analyze for 1,4-dioxane. A sensitive and reliable laboratory analytical method was not
available until 1997, when the California Department of Health Services developed a method for
low-level detection of 1,4-dioxane (Draper et al., 2000). Other solvent-stabilizer compounds may
also be overlooked because (1) most investigations of solvent-release sites focus on analyzing for
familiar chlorinated aliphatic hydrocarbon compounds and (2) the methods used are unsuitable for
trace detection and quantii cation of ethers, alcohols, and other highly soluble compounds that have
been used as solvent stabilizers.
The challenge to analyze for 1,4-dioxane in water is a direct consequence of its miscibility with
water, its low water-air partition coefi cient, and its low afi nity to organic carbon. Understanding the
challenges faced by laboratory chemists helps remedial project managers make better use of avail-
able laboratory analytical methods. This chapter is written for the “layperson,” that is, engineers,
geologists, and other people interested in contaminated site remediation who are laboratory clients
but who have relatively limited familiarity with the subtleties of laboratory analysis. This chapter
also includes detailed information on 1,4-dioxane analysis for the benei t of laboratory chemists.
Sampling methods can make an important difference in the results of analyzing for hydrophilic
compounds. The requirements of sampling for 1,4-dioxane by routine or innovative methods are sum-
marized here. By way of review, the basic principles of gas chromatography (GC), mass spectrometry
(MS), and sample preparation are briel y discussed here in the context of 1,4-dioxane analysis.
This chapter demonstrates that in laboratory analysis of environmental samples, the chemist is
faced with myriad considerations for how the many available combinations of different options in
each analytical step best serve to isolate and quantify the contaminants of interest. This universe of
possibilities makes analytical chemistry a fascinating science; indeed, its skillful execution deserves
the same appreciation as i ne art!
4.1 THE FLAWED PARADIGM OF ANALYTE LISTS
To satisfy regulatory requirements and generate comparable results, project managers often require
the use of standard methods for analysis of samples from sites contaminated by hazardous wastes.
These methods are usually selected from the U.S. Environmental Protection Agency (USEPA) Test
Methods for Evaluating Solid Waste [SW-846 (see USEPA, 2006a, and earlier editions)]. These
methods are designed to reliably report accurate results for a limited list of compounds that behave
similarly and that can be analyzed by using the same general approach and instrument parameters.
Analyzing for solvents from standard lists of priority pollutants will overlook important com-
pounds that may be equally or more toxic and mobile than those that the site investigator seeks.
Therefore, more information could be obtained by focusing the laboratory phase of an investigation
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