Sampling and Laboratory Analysis for Solvent Stabilizers - Environmental Investigation and Remediation - page 200

28

100

1, 4-Dioxane
CASRN# 123-91-1
C4H8O2

O

88

50

O

58

31

43

15

0

10 20 30 40 50 60 70 80 90 100

Mass-to-charge ratio ( m / z )

FIGURE 4.3 Mass spectrum for 1,4-dioxane-d 8 and its ion fragments. (From Yoo, L., 2002. Simultaneous
determination of 1,2,3-TCP and 1,4-dioxane in drinking water by GC-MS/MS using purge/trap techniques.
Orange County Water District. With permission.)

compounds with sufi ciently high volatility to allow their transfer from soil samples under equilib-
rium headspace conditions (USEPA, 2006c). 1,4-Dioxane's hydrophilic nature and low air-water
partition coefi cient make headspace methods an unsuitable approach for its analysis; however, such
methods have been used with modii cations. A Danish study of 1,4-dioxane content in cosmetics
and sundries adapted the equilibrium headspace method by weighing a 1 g sample in a headspace
vial and adding it to 25 L 0.1% (V/V) 1,4-dioxane-d 8 . The headspace

vial was then heated for 16-18 h at 80°C, and the gas was routed to a GC-MS operated in selective ion
monitoring (SIM) mode for target masses 88 and 96 [for 1,4-dioxane and 1,4-dioxane-d 8 (Figure 4.3);
SIM is explained further in Section 4.5.5 ]. The limit of detection achieved was 300

μ L dichloromethane and 25 μ

μ g/L (0.3 ppm)

(Rastogi, 1990).
A Polish study also focused on the use of headspace methods for 1,4-dioxane analysis in sun-
dries. In this study, 1 g of sample was introduced to headspace vials together with a standard of
dioxane dissolved in a solvent; thereafter, the vials were heated to 130°C for 1 h. Careful analysis of
partition coefi cients of dioxane from the laboratory solvent allowed quantitation to 2 μ g/g (2 ppm)

for dioxane in shampoos (Wala-Jerzykiewicz and Szymanowski, 1998).

4.3.4 V ACUUM D ISTILLATION
Vacuum distillation is another means of transferring contaminants from samples to the carrier gas.
EPA Method 5032 uses vacuum distillation and a cryogenic trapping procedure followed by GC-MS.
The sample is introduced into a sample l ask, which is then depressurized to the vapor pressure of
water through the use of a vacuum pump. The vapor is passed over a condenser coil chilled to -10°C
or less to condense water. The uncondensed distillate is cryogenically trapped on stainless steel tub-
ing chilled with liquid nitrogen (-196°C). The condensate is then thermally desorbed and trans-
ferred to the GC by using helium carrier gas (USEPA, 2006b). The 1996 publication of EPA Method
5032 does not identify 1,4-dioxane as suitable for analysis using vacuum distillation; however, a
2004 improvement to the method includes 1,4-dioxane as a suitable analyte (Strout et al., 2004a).
EPA Method 8261A uses a vacuum distillation unit to extract volatile and semi-VOCs, including
1,4-dioxane. The lowest MDL obtained for 1,4-dioxane was 2.5

g/L for low-concentration water
samples, but recoveries were variable (Strout et al., 2004a). See Section 4.2.5.4 for more discussion
of vacuum distillation in EPA Method 8261A.

μ