Methodology and Quality Assurance/Quality Control of Environmental Analysis - Fundamentals of Environmental Sampling and Analysis - page 113

of VOCs using GC-MS. These compounds are purgeable with an inert gas bubbling
through a 5-mL sample so that the volatile organics are transferred from the water
phase to the vapor phase. Due to their volatile nature, VOCs cannot be analyzed by
high performance liquid chromatography (HPLC). Operational principles of GC
with various detectors will be discussed in Chapter 10.

5.2.4 Methods for Semivolatile Organic
Compounds (SVOCs)

Like VOCs, methods for SVOCs can also be found in EPA 500, 600, and 8000 as
well as APHA 6000 or USGS O-xxxx-xx methods. Unlike VOCs, however, many
SVOCs (e.g., PCB, PAHs, pesticides) can be analyzed by either GC or HPLC. The
counterpart of Method 624 is Method 625 for nonpurgeable but extractable
semivolatile organic compounds (SVOCs). To begin SVOC analysis using Method
625, the pH of a 1-L sample is adjusted to a pH greater than 11. The sample is then
extracted with methylene chloride to obtain a base/neutral fraction. The pH of the
sample is then adjusted to less than 2 and is again extracted with methylene chloride
to form the acid fraction. Each fraction is chemically dried to remove the water and
concentrated by distillation to 1 mL. The fractions are then analyzed by GC/MS.
Note that the acid fraction compounds are mostly phenolic compounds such as
phenol, halogenated phenols, and nitrophenols. The base/neutral compounds include
PAHs, ethers, di- and tri- halobenzene, and phthalates.

5.2.5 Methods for Other Pollutants and Compounds
of Emerging Environmental Concerns

What we have described so far are the standard analytical methods for contaminants
regulated by the U.S. EPA. Many contaminants have not been regulated by the U.S.
EPA. As concern for these contaminants emerge, testing methods will have to be
developed. The EPA has not established analytical methods for these contaminants
so the responsibility rests within the research community.
Under the Safe Drinking Water Act, the EPA has initiated a process to
periodically propose a contaminant candidate list (CCL) to include those chemicals
that may require regulation in the future. The EPA uses this list of unregulated
contaminants to prioritize research and data collection efforts to help to determine
whether it should regulate a specific contaminant. As of February 2005, EPA has
published the second CCL of 51 contaminants (http://www.epa.gov/ogwdw/ccl/
cclfs.html). For example, algal toxins, organotins, and methyl tert-butyl ether
(MTBE) are among these chemicals, any of which may enter into drinking water
through various sources. Table 5.5 is a list of selected chemicals from the CCL along
with several other emerging contaminants to illustrate the analytical complexity of
these compounds.
It is apparent from Table 5.5 that testing for these compounds requires state-
of-the-art

instrumentation that many labs cannot afford to purchase. We will