Sampling and Laboratory Analysis for Solvent Stabilizers - Environmental Investigation and Remediation - page 216

TABLE 4.8
Method 8260C Accuracy and Precision for 1,4-Dioxane by Mean Percent Recovery ( R )
and Percent Relative Standard Deviation (RSD)

25 ppb Spike 100 ppb Spike 500 ppb Spike

R RSD R RSD R RSD

1,4-Dioxane-d 8 63 25 55 16 54 13

Source: U.S. Environmental Protection Agency (USEPA), 2006c, Method 8260C: Volatile organic compounds by gas
chromatography/mass spectrometry (GC/MS). U.S. Environmental Protection Agency.
Notes: Sample preparation by Method 5031—the microdistillation technique (single laboratory and single operator). Lower
RSD values rel ect increased precision. Data from analysis of seven aliquots of reagent water spiked at each concen-
tration, using a quadrupole mass spectrometer in the selected-ion monitoring mode.

4.5.3 E NVIRONMENTAL P ROTECTION A GENCY M ETHOD 8260C
EPA Method 8260C is a heated PT method that uses a 1,4-dioxane-d 8 standard. The sample is
heated to 90°C, which produces an approximately i vefold increase in 1,4-dioxane recovery over
conventional analysis; however, the 1,4-dioxane recovery can nevertheless be as low as 1%. Using
heated PT requires careful control on temperature to generate reproducible results. Because the
majority of the 1,4-dioxane remains in the sparger, thorough rinsing and bake-out must be per-
formed to prevent carryover (Fitzpatrick and Tate, 2006). The description for EPA Method 8260C
requires that the sample be heated to at least 80°C before 1,4-dioxane can be considered a viable
analyte by PT. Sample preparation may also include Method 5031, azeotropic distillation, and
Method 5032, closed-system vacuum distillation (USEPA, 2006c). The recovery of 1,4-dioxane
described in Method 8260C is low, but the recovery is indexed to the isotope standard, allowing
quantitation of 1,4-dioxane. Recoveries and RSDs for 1,4-dioxane analyses by Method 8260C at a
single laboratory by a single operator are listed in Table 4.8. Method 8260C does not list a lower
limit of quantitation for 1,4-dioxane.

4.5.4 E NVIRONMENTAL P ROTECTION A GENCY M ETHOD 8261A
EPA Method 8261A uses vacuum distillation to vaporize compounds and separate VOCs, some low-
boiling-point semivolatile organic compounds, and polar nonpurgeable or low-purging compounds
from soil, water, and other environmental sample matrices. The volatilized material passes over a
chilled condenser coil to condense and remove water. The analytes are condensed by using liquid
nitrogen to obtain cryogenic temperatures (down to -196°C). Volatile organic analytes are then intro-
duced by a vacuum distiller into the gas chromatograph, which is interfaced with a mass spectrometer.
The combination of cryogenic trapping and vacuum distillation is described by EPA Method 5032.
EPA Method 8261A uses internal standards to measure matrix effects and to compensate analyte
responses for matrix effects. This method should be considered for samples in which matrix effects
are anticipated to severely affect analytical results (USEPA, 2006d). The inventor of the vacuum
distillation technique, Michael Hiatt, is a USEPA scientist; EPA was granted a patent for the method
(Hiatt, 1995).
The EPA vacuum distillation method accounts for the physical chemistry of analytes in mea-
suring matrix effects, yielding method performance data by analyte. Results for analyses by EPA
Method 8261A are reported with coni dence intervals. EPA Method 8261A eliminates the need
for matrix spike-matrix spike duplicates as well as calibration of instrumentation by matrix type
(Hiatt, 2007).