United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S4-86/037 March 1987
SEPA Project Summary
Evaluation of an EPA
High-Volume Air Sampler for
Polychlorinated Dibenzo-p-
Dioxins and Polychlorinated
Dibenzofurans
F. L DeRoos, J. E. Tabor, S. E. Miller, S. C. Watson, and J. A. Hatchel
An EPA High-Volume air sampler was
evaluated for retention and migration
of polychlorinated dibenzo-p-dioxins
(PCDD) and polychlorinated dibenzo-
furans (PCDF) within the sampler. This
sampler, which is available from General
Metal Works (GMW) as the Model PS-1
Sampler, consists of a filter, polyure-
thane foam adsorbent cartridge, air
pump, and environmental housing. The
use of an alternative adsorbent, silica
gel, was also studied. Because of the
high toxicity of selected PCDD/PCDF
isomers and the limited availability of
pure isomers, the study was carried out
using 1,2,3,4-tetrachlorodibenzo-p-
dioxin, 1,2,4,8-tetrachlorodibenzo-
furan, 1,2,3,4,7,8-hexachlorodibenzo-
p-dioxin, 1,2,3,6,7,8-hexachlorodi-
benzofuran, octachlorodibenzo-p-
dioxin, and octachlorodibenzofuran.
The sampler retained the isomers with
approximately equal efficiencies when
either PUF or silica gel was used as the
adsorbent. The median retention effici-
encies for the PCDD/PCDF isomers
ranged from 67 to 124 percent when
PUF was used, and from 47 to 133
percent when silica gel was used. In
general, the lowest retention efficiencies
were observed for the PCDF isomers
and the highest retention efficiencies
for the PCDDs. The overall average
retention efficiency for all of the isomers
at two concentration levels was 99
percent for both the PUF and the silica
gel adsorbents.
Silica gel produced lower levels of
background interferences than did PUF.
The detection limits were therefore
about four times lower for the tetra-
chlorinated isomers and 10 times lower
for the hexachlorinated isomers when
silica gel was used as the adsorbent.
The difference in detection limit was
approximately a factor of two for the
octachlorinated isomers, which are of
higher molecular weight than are the
tetrachloro isomers, and consequently
are less susceptible to interference.
However, the silica gel was less con-
venient to work with and required more
steps to clean up.
The desorption efficiency of the
PCDD/PCDF isomers from spiked fil-
ters was evaluated to assess the extent
of migration of these compounds from
the filter to the adsorbent. Migration
was dependent upon the isomers'
chlorination level with the less chlori-
nated, more volatile isomers generally
desorbing more efficiently. Tetrachlori-
nated isomers desorbed almost com-
pletely from the filter and were col-
lected on the adsorbent, whereas the
octachlorinated isomers were retained
on the fitters. Hexachlorinated isomers
gave intermediate values of desorption
from the filters.
This Protect Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
-------
merited In a separate report of the same
title (see Project Report ordering In-
formation at back).
Introduction
Polychlorinated dibenzo-p-dioxins
(PCDD) and polychlorinated~dibenzo-
furans (PCDF) are classes of tricyclic
compounds that are extremely toxic and
are of major environmental concern.
Certain isomers, including 2,3,7,8-tetra-
chlorodibenzo-p-dioxin (2,3,7,8-TCDD)
and 2,3,7,8-tetrachlorodibenzofuran
(2,3,7,8-TCDF), have LD60 values in the
parts-per-triliion range for some animal
species. Major sources of these com-
pounds have been commercial processes
involving polychlorinated phenols and
polychlorinated biphenyls (PCB). Recent-
ly, however, combustion has been a
source of PCDD and PCDF. A particularly
significant source of these compounds is
burning transformers and/or capacitors
that contain PCBs and chlorobenzenes.
The objectives of this project were to
determine the retention efficiency of the
EPA High-Volume air sampler by measur-
ing the retention and migration of selected
PCDD and PCDF isomers within the
sampler and to evaluate the utility of
using silica gel as the adsorbent. Previous
studies involving the collection of pesti-
cides, PCBs, semivolatile industrial
organic compounds, 1,2,3,4-TCDD and
octachlorodibenzof uran (OCDF) have been
successful. However, it was anticipated
that silica gel would provide a lower
background interference level and thus
allow lower detection limits to be
achieved.
The study consisted of spiking the filters
or adsorbent cartridges of EPA High-
Volume air samplers with selected
PCDD/PCDF isomers. The PCDD/PCDF
levels that remained on the filter or the
adsorbent cartridge were then measured
after a volume of approximately 325 m3
of air had been pulled through each
sampler.
Procedure
Flow Rate Study
The air flow rates through various bed
heights of silica gel were measured to
determine if sufficient flow could be
achieved. The silica gel was packed into
glass cartridges and was held in place
using a copper screen and thin layers of
glass wool. The cartridge containing the
silica gel was placed into a standard
High-Volume sampler and flow was es-
tablished. The experimental setup con-
sisted of a High-Volume Sampler air
pump, a dry gas meter, an EPA gas flow
calibrator, a filter holder, and a test
cartridge containing the silica gel. The
system was allowed to equilibrate for 30
minutes prior to recording the dry gas
meter readings.
Retention Study
Known levels of PCDD/PCDF isomer
were spiked into the sampler, and the
levels of the PCDD/PCDF isomers re-
maining on the adsorbent cartridges and
glass fiber filters following the sampling
of approximately 325 m3 of clean air
were measured. Two PCDD/PCDF levels,
150 ng and 5 ng of each isomer, were
evaluated in triplicate. The PCDD/PCDF
isomers were spiked into the sampler as
n-decane solutions. For the experiment
in which the spike was placed on the
adsorbent cartridge, only the cartridge
was analyzed. When the spike was placed
on the filter, and filter and cartridge were
analyzed separately. Two additional spiked
cartridges, one each at the low and high
levels, were also prepared for each
adsorbent and held in the laboratory dur-
ing the sampling sessions. Air was not
pulled through these cartridges. These
were used as reference samples to in-
dicate if irreversible adsorption occurred
as a function of time.
The test setup consisted of two high-
volume sampler heads connected in
series. The first sampler contained a
microfiber glass filter and activated carbon
to purify the air going into the second
sampler, which contained the test filter
and adsorbent cartridge.
Following the sampling, each of the
cartridges and filters was spiked with
2,3,7,8-TCDD-13Ci2 and octachlorodi-
benzo-p-dioxin-'3C12 (OCDD-13C12) and
Soxhlet-extracted with benzene for 18
hours. The high level samples, e.g., those
spiked with 150 ng of the native isomers,
were spiked with 50 ng of the labelled
internal standards, while the low level
samples were spiked with 5 ng of each
internal standard. The benzene extracts
were concentrated using a 3-stage
Snyder column, diluted 1.1 with hexane,
and cleaned up using acid/basetreated
silica and alumina column chromato-
graphy. The final solutions were analyzed
by high resolution gas chromatography/
high resolution mass spectrometry. The
spiking solutions were used to prepare
response factor standards, thus eliminat-
ing the spiking solution concentration as
a variable in the retention efficiency
calculations.
Results
Flow Rate Study
Adequate flow air rates for sampling
( A150std. L/min) were achieved for both
meshes of silica gel and for all bed heights
evaluated. Although the 6-12 mesh silica
gel could be used with bed heights of up
to 7.6 cm, the finer 35-70 mesh material
was chosen to provide the greatest sur-
face area for collection of the test
PCDD/PCDF isomers. The results of the
flow rate study are summarized in Table
1
Retention Study
The average retention efficiency for
the PCDD/PCDF isomers spiked on filters
was dependent upon the volatility of the
particular isomer. In general, the tetra-
chlorinated isomers desorbed from the
filters and were collected on the adsor-
bent, while the octachlorinated isomers
remained on the filters. The hexachlori-
nated isomers exhibited intermediate
behavior. When the data from the PDF
and silica gel experiments are averaged
at the two spiking levels, approximately
1.8 percent of the tetrachlorinated isomer
spikes was retained on the filters, while
83 percent of the octachlorinated isomer
spikes was retained after sampling. The
hexachloro isomer spikes were retained
on the filters at approximately 10 percent.
The average performance of the sam-
pler for retention of PCDD/PCDF isomers
is summarized !:: Tables 2 ^nd 3. Table 2
summarizes the results for the sampler
when PUF is used as the adsorbent and
Table 3 the results when silica gel is
used. All of the retention efficiencies are
within ± 25 percent of quantitative, ex-
cept for the two hexachloro isomers which
vary by approximately ± 30 percent.
The adsorbent retention efficiencies for
the HxCDD and HxCDF isomers were the
lowest and the most variable of those
measured. Although it is possible that
these isomers were breaking through the
adsorbents, it is also possible that they
were lost during the sample workup.
Since an isotopically labelled hexachlori-
nated dioxin or furan was not available
for use as an internal standard, losses
due to extraction and cleanup were cor-
rected based on the recovery of the
labelled tetrachlorinated standards. It was
assumed that the volatility and extraction
efficiency of these standards were similar
to those of the hexachlorinated isomers,
however, the validity of these assump-.
tions has not been tested for all matrices.1
-------
Table 1. Flow Rates for Silica Gel Adsorbent
Experiment Weight fg) Mesh Bed Height (cm) Flow Rate (L/ mm)
1 30
2 60
3 30
4 60
5 90
6 120
7 150
35-70 25 190
35-70 45 160
6-12 1.9 230
6-12 3.2 220
6-12 5.1 220
6-12 6.4 215
6-12 7.6 215
Table 2. Retention Efficiency Performance of the PS- 7 Sampler for PCDFs and PCDDs
Using PUF as the Adsorbent
Average Percent Recovery
Spike Level, '
Medium ng/m3
Filter 0 5'
PUF
Total
Filter 0 02
PUF
Total
TCDF TCDD HxCDF HxCD OCDF
032 1.5 4.8 10 57
82 95 103 97 25
82 96 108 107 82
20 1 3 26
79 95 93 104 71
81 95 94 107 97
OCDD
86
13
99
41
67
108
' Spike levels based on total weight of PCDD/PCDF isomer spitted, assuming 325 m3 of air were
sampled.
! A verage for three experiments
'able 3. Retention Efficiency Performance of the PS- 7 Sampler for PCDFs and PCDDs
Using Silica Gel as the Adsorbent
Average Percent Recovery
Spike Level,
Medium ng/m3
Filter 0 5
Silica Gel
Total
Filter 0.02
Silica Gel
Total
TCDD HxCDF HxCDD OCDF
45 6.7 43 61
74 62 92 21
78 69 140 82
1.6 5.7 7.6 83
74 63 83 8.1
76 68 91 91
OCDD
94
2.6
97
110
6.8
120
the samples, the isomers desorbed and
were collected on the adsorbent. The
degree of desorption was dependent upon
the volatility of the isomer and tended to
follow the level of chlorination. The tetra-
chlorinated isomers were almost com-
pletely desorbed from the filter, while the
octachlorinated isomers showed only
minimal migration. The hexachlorinated
isomers desorbed at a degree inter-
mediate to the tetrachlorinated and
octachlorinated isomers.
The GMW PS-1 air sampler should be
a suitable sampler for collection of
PCDD/PCDF isomers from ambient air
when either PUF or silica gel is used as
the adsorbent. When PUF was used in
these studies, the analytical detection
limit was approximately 0.2 ng for TCDD
and TCDF, which would compare to a
theoretical ambient air detection limit of
about 0.6 pg/m3 for a 24-hour sample.
The use of chromatographic-grade silica
gel improved detection limits by a factor
of nearly four, to about 0. 1 5 pg/m3. The
silica gel, however, presented more dif-
ficulties in cleanup and use.
Due to the desorption of PCDD/PCDF
isomers from the filter, the sampler will
not provide samples that can be used to
determine the particulate matter/ vapor
concentration distribution of the PCDD/
CDF isomers. If the lowest possible
detection limits are needed, silica gel
should be used as the adsorbent, since it
is more stable than PUF and will, there-
fore, minimize interferences and provide
the lowest possible detection limits.
Conclusions and
Recommendations
The retention efficiencies for the
PCDD/PCDF isomers spiked into the
samplers were in general quantitative
agreement within experimental accuracy.
The median retention efficiencies ranged
from 67 to 124 percent when PUF was
used as the adsorbent and from 47 to
133 percent when silica gel was used.
The lowest retention efficiencies were
observed for the PCDF isomers, particu-
rly the tetrachlorinated and the hexa-
brinated isomers.
Silica gel was found to be suitable as a
replacement adsorbent for PUF. It can be
packed into the same cartridge as the
PUF and produces minimal resistance to
the air flow. It does not degrade like PUF,
and therefore produces lower levels of
interfering compounds. Thus, the detec-
tion limits for the PCDD/PCDF were
between two and ten times lower when
silica gel was used as the adsorbent than
when PUF was used.
When the PCDD/PCDF isomers were
spiked onto the filter and approximately
325 m3 of clean air was drawn through
-------
F. L DeFtoos, J. E. Tabor, S. E. Miller, S. C. Watson, and J. A. Hatchel are
with Battelle Columbus Division, Columbus, OH 432O1-2693.
Robert G. Lewis and Nancy K. Wilson are the EPA Project Officers (see below).
The complete report, entitled "Evaluation of an EPA High-Volume Air Sampler
for Polychlorinated Dibenzo-p-Dioxins and Polychlorinated Dibenzofurans,"
(Order No. PB 87-129 805/AS; Cost: $11.95, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officers can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Inform,ition
Cinrinn.ni OH 45268
U.a OFFICIAL MAIL
°ENALTY
JSE $300
U.S.POSTAGE
Official Business
Penalty for Private Use S300
EPA/600/S4-86/037
f8 METER
6250103
0000329 PS
U S ENVIR PROTECTION AGENCY
REGION 5 LI8RART
230 S DEARBORN STREET
CHICAGO IL 60604
4
------- |