Sampling and Laboratory Analysis for Solvent Stabilizers - Environmental Investigation and Remediation - page 198

TABLE 4.3
Soil-Gas Sampling Tube Materials and 1,4-Dioxane Emissions and Recovery

1,4-Dioxane
Emissions

Frequency of
Detection (%)

1,4-Dioxane
Recovery (%)

RSD a
(%) Tubing Name Tubing Material

LM Nylal ow Nylon 0.068 ppbv 11 100 2

PEEK Polyetheretherketone <DL b 0 79 5

Tel on Fluoroethylene-propylene (FEP) <DL b 0 77 5

Polyethylene Low-density polyethylene

(LDPE)

<DL b 0 113 7

Source: Hayes, H.C., Benton, D.J., and Khan, N., 2006, In: Vapor Intrusion—The Next Great Environmental Challenge—An

Update . Los Angeles, CA: Air and Waste Management Association. With permission.

Relative standard deviation—all tests were highly reproducible.

a

Detection limit.

b

4.2.3 P ERSONNEL A IR M ONITORING
Personnel air monitoring has typically been performed by using battery-powered portable sampling
pumps and sorbent tubes. The National Institute for Occupational Safety and Health (NIOSH) pro-
mulgates methods for personnel monitoring, including Method 1602 for 1,4-dioxane. NIOSH Method
1602 uses a solid sorbent tube of coconut shell charcoal. A minimum of 0.5 L to a maximum of 15 L
of workplace air is drawn through the tube at a rate of 0.1-0.2 L/min. The sample is then desorbed
for 30 min with carbon disuli de as the solvent, and the sample is analyzed by GC with a l ame-
ionizing detector. The typical limit of detection is 0.010 mg per sample (Kurimo, 1994).
Field instruments for screening VOC vapors operate by using photo-ionization or l ame-
ionization detectors (FIDs). Photo-ionizing detectors (PIDs) can detect 1,4-dioxane, whose photo-
ionization potential is 9.13 electron volts (eV). PID instruments such as the HNU can be calibrated
to detect a particular compound when it is the sole compound present within a particular ionization
range; however, PIDs are not well suited for distinguishing between detectable compounds in a
mixture of gases. PID readings typically provide an integrated response to the gas mixture. Field
instruments based on l ame ionization can detect 1,4-dioxane. The l ame-ionization potential for
1,4-dioxane is 9.41 eV. Another alternative for screening 1,4-dioxane vapors is a portable gas
chromatograph (Photovac, 2006).

4.3 SAMPLE PREPARATION
Sample preparation is the i rst step performed on a sample delivered from the i eld. There are many
established methods for sample preparation, each dependent on the nature of the analyte and the
selection of analytical method. This section offers a brief review of the major sample extraction and
concentration methods that have been used for 1,4-dioxane in water and soil.

4.3.1 P URGE AND T RAP
EPA Method 5030B describes the most common protocol for the purge-and-trap (PT) technique.
The sample is purged by bubbling an inert gas, usually helium or nitrogen, through the aqueous
sample at ambient temperature. The volatile components are transferred from the aqueous phase to
the vapor phase. The contaminant vapor is introduced at a specii ed l ow rate to a sorbent column
where the volatile components are adsorbed. After purging is completed, the sorbent column is
heated and back-l ushed with inert gas to desorb the components onto a gas chromatographic column