Optimizing the Analysis of Volatile Organic Compounds

EPA Method Definitions
Many EPA methods have been developed for the analysis of VOCs. Virtually all VOC methods
employ purge and trap techniques to concentrate the volatiles from the sample matrix. The
type of sample matrix being analyzed determines which method is used. We will discuss
drinking water methods (500 series), wastewater methods (600 series), hazardous waste
methods (8000 series), and Contract Laboratory Program (CLP) methods. In addition, we will
discuss state gasoline range organic (GRO) methods.
Drinking Water Methods (500 Series)
Proposed in 1973 by the EPA and passed by Congress a year later, the Safe Drinking Water
Act (SDWA) establishes national standards for drinking water from surface and ground water
sources. These methods regulate the analysis of trace-level organic pollutants in drinking
water. Enforcement of the SDWA provides that states shall have the primary authority, while
the EPA will oversee activities pertaining to the public water supply system. These methods
have evolved over the years, which has resulted in a growing list of compounds of interest in
the subsequent revisions.
Method 502.2: This capillary column GC method is used to monitor 60 regulated volatile
contaminants in drinking water. It employs a purge and trap concentrator, combined with a
photoionization detector (PID) and an electrolytic conductivity detector (ELCD) in series.
The PID detects aromatic and double-bond compounds, and the ELCD detects halogenated
compounds.
Method 504: This capillary column GC method is used to monitor ethylene dibromide
(EDB) and dibromochloropropane (DBCP) in drinking water. It employs microextraction,
using hexane, and analysis using an electron capture detector (ECD).
Method 524.2: This capillary column GC/mass spectroscopy (GC/MS) method is used to
monitor the same 60 drinking water contaminants listed in Method 502.2. It also employs
purge and trap concentration, but uses the MS to determine both aromatic and halogenated
compounds.
Method 524.2, Revision IV: This capillary column GC/MS method is used to monitor the
60 compounds listed in Methods 524.2 and 502.2, plus 24 additional compounds. As of
Fall 2001, revisions were proposed to replace hydrochloric acid sample preservation with
sodium thiosulfate. These revisions, however, were not promulgated at the time of this
printing.
Wastewater Methods (600 Series)
In 1977, President Carter signed the Clean Water Act (CWA) allowing the EPA to study and,
if necessary, regulate 65 priority wastewater pollutants. A cooperative effort between environmental
laboratories and the EPA resulted in the final version of what are now known as
the 600 series methods. These methods regulate the analysis of organic pollutants in industrial
and municipal wastewater discharges. They were written for packed GC columns, but
most environmental laboratories now use capillary column technology.
Method 601: This GC method was developed to monitor 29 halogenated volatile pollutants
in wastewater. It employs purge and trap concentration combined with an ELCD.
Method 602: This GC method was developed to monitor seven aromatic volatile pollutants
in wastewater. It employs purge and trap concentration combined with a PID. Many laboratories
combine Methods 601 and 602 by using a PID and an ELCD connected in series.
Method 624: This GC/MS method uses purge and trap concentration to monitor 35 halogenated
and aromatic volatile pollutants in wastewater.
Method 1624: This isotope dilution GC/MS method uses purge and trap concentration to
monitor 58 volatile pollutants in wastewater. Stable, isotopically labeled analogs of the target
compounds are added to correct for analyte recoveries that might vary due to matrix interference
in the analyzed samples.
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