Sampling and Laboratory Analysis for Solvent Stabilizers - Environmental Investigation and Remediation - page 192

Daughton (2003, p. 758) has offered several deceptively simple but profoundly important insights
into the limitations of environmental analyses:

• Not everything that can be measured is worth measuring, and not everything worth mea-

suring is measurable
What one i nds usually depends on what one aims to search for •

• Only those compounds targeted for monitoring have the potential for being identii ed and

quantii ed
Those compounds not targeted will elude detection •

• The spectrum of pollutants identii ed in a sample represents but a portion of those present

and they are of unknown overall risk signii cance

These axioms apply very well to solvent stabilizers and help to explain why after more than
20 years of cleanup at solvent-release sites, 1,4-dioxane is only now being discovered. Figure 4.1
summarizes the manner in which the universe of possible chemicals present in the environment is
narrowed to the target analyte list by USEPA methods.
The tendency for 1,4-dioxane to be overlooked by routine approaches for analyzing samples for
organic compounds was i rst noted in 1977. In a review article by William T. Donaldson of the
USEPA, the basis for establishing analyte lists was questioned. Donaldson noted that a list of 50
compounds expected to occur because of their known use in industry did not match well with a
survey of 5500 analyses of water samples. Whereas many of the compounds expected in water were
not found, 1,4-dioxane was observed in 15 analyses, and nitromethane was observed in 10 samples
(Donaldson, 1977).

4.2 SAMPLE COLLECTION, PRESERVATION, AND HANDLING FOR
ANALYSIS OF 1,4-DIOXANE
EPA methods that include 1,4-dioxane as an analyte include EPA Method 8260B, EPA Method
8270C, and EPA Method 1624. Sample-preservation requirements for these methods follow the
general protocol for all analytes obtained from those methods, as summarized in Table 4.1 .
To ensure data validity, it is best to follow the sample container, preservation, and holding time
protocols for the EPA method that will be used for 1,4-dioxane analysis or the EPA method upon
which the commercial laboratory's adaptation is based. Although acidic preservatives are required for
EPA methods for volatile organic compound (VOC) analysis, they are not necessary for 1,4-dioxane.
1,4-Dioxane extraction and recovery are independent of pH (Yoo et al., 2002). Biodegradation of
1,4-dioxane in samples is not likely to be a concern, given the absence of evidence for inherent bio-
degradation of 1,4-dioxane under ambient conditions (Vainberg et al., 2006).

4.2.1 S AMPLING FOR 1,4-D IOXANE IN W ATER
Conventional groundwater sampling approaches involve a one-stop visit to a well site for sample
retrieval with a bailer or a submersible sampling pump, after purging three to i ve well-casing vol-
umes or enough groundwater so that consecutive readings of pH and conductivity are constant.
Other systems include dedicated tubing that pulls samples directly from depth-discrete zones in a
monitoring well through the use of a peristaltic pump or a nitrogen lift bladder pump. Another
approach for sampling soluble organic compounds is the passive-diffusion concept, which provides
the basis for a variety of no-purge sampling devices (Parsons, 2005; O'Neill, 2006). These include
the polyethylene diffusion bag (PDB; also called passive-diffusion bag), rigid porous polyethylene
(RPP), polysulfone membrane, regenerated cellulose, Snap Sampler™, and Hydrasleeve™. All of