Sampling and Laboratory Analysis for Solvent Stabilizers - Environmental Investigation and Remediation - page 214

because it is readily available and provides the desired high ionic strength. To obtain the preferred
“salting out” effect, sodium chloride and sodium or magnesium sulfate are used at concentrations
that attain 80% saturation at 65°C. 1,4-Dioxane recovery with heated PT increased 21% without salt
and as much as 56% with addition of sodium sulfate salt. The heated PT method provided a prelimi-
nary MDL of 4 ppb and limit of quantitation of 20 ppb (Lucas et al., 1988).
USEPA published CLP Method OLM03.1 for 1,4-dioxane in water by SIM GC-MS in 1994
(USEPA, 1994). The method uses a heated PT at 50°C, followed by GC-MS analysis using
SIM rather than full-scan analysis. The monitored ions have mass-to-charge ratios ( m / z ) of
88 0.5 for 1,4-dioxane-d 8 as an internal

standard. Method OLM03.1 could reportedly achieve a practical quantitation limit of 5

± 0.5 and 58 ± 0.5 for 1,4-dioxane and 96 ± 0.5 and 64 ±

μ g/L

(USEPA, 1994).
In 1997, USEPA's Central Regional Laboratory, operated by EPA Region V in Chicago, published
a method for measurement of purgeable 1,4-dioxane in water using wide-bore capillary column
GC-MS (Rudinsky et al., 1997). The method uses a heated PT with sodium sulfate and 1,4-dioxane-d 8
added as the internal standard. The method was accurate for samples with 1,4-dioxane concentra-
tions between 20 and 200 g/L. A summary of instrumentation and operating parameters for this

method is included in Appendix 3.
Researchers with the Shaw Group and USEPA in Las Vegas conducted a multilaboratory com-
parison study of purgeable versus extractable methods and conventional versus isotope-dilution
quantitation methods (Strout et al., 2004b). The results show that quantitation by isotope dilution
provides higher accuracy and precision than the conventional method of quantitation, regardless of
whether the method uses purgeable or extractable sample preparation.
Carryover contamination can occur with the 1,4-dioxane purgeable method, and method blank
contamination was observed in the study. High recoveries of low spiked concentrations, that is,
2

μ

g/L, indicate that carryover was occurring. Carryover contamination must be addressed by run-
ning an additional method or instrument blanks, which adds to the method cost and time of analysis.
The study concluded that analysis of 1,4-dioxane using a 5 mL heated purge, an accelerated sample
purge l ow, and SIM MS detection produces the most linear calibration for a concentration range
from 0.5 to 200

μ

g/L, as well as the highest signal-to-noise (S/N) ratio. Running a 25 mL purge
volume with the same analytical conditions provided a calibration over a narrower concentration
range (0.5-20

μ

g/L). The optimal sample temperature is approximately 50°C, and the optimal sam-
ple purge l ow is approximately 50 cm 3 /min for the analysis of 1,4-dioxane as a purgeable analyte
on the SIM MS system (Strout et al., 2004b).
USEPA's CLP developed a draft protocol for the analysis of trace 1,4-dioxane using the SIM
method. SIM requires method blanks at the beginning and end of the analytical sequence and con-
tinuing calibration verii cation (CCV) standards. Quantitation is performed by using the average
relative response factor (RRF) from the initial calibration. USEPA Method 8260 is often used with
SIM for analysis of 1,4-dioxane, as described in Section 4.5.2 .

μ

4.5.1 E NVIRONMENTAL P ROTECTION A GENCY M ETHOD 8015B
Method 8015 analyzes nonhalogenated volatile and semivolatile organic compounds by GC and
l ame-ionization detection. The recommended sample-preparation methods for analysis of 1,4-di-
oxane by EPA Method 8015B are direct injection and azeotropic microdistillation. Poor purging
efi ciency is noted for 1,4-dioxane sample preparation by PT, and solvent extraction is not recom-
mended for EPA Method 8015B analysis of 1,4-dioxane (USEPA, 1996a). Four GC columns are
recommended for EPA Method 8015B, including a DB-Wax column suitable for 1,4-dioxane reten-
tion. The recommended columns are summarized in Table 4.6 .
For reagent grade water, groundwater, and leachate, EPA Method 8015B can achieve MDLs of
12, 15, and 16 g/L, respectively (according to EPA's Toxicity Characteristic Leaching Procedure

test; USEPA, 1996c). Detection limits for other media are shown in Table 4.4 .

μ