vvEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S2-81-047 July 1981
Project Summary
XAD-2 Thermal Blank
Determination—June 1980
C. H. Lochmuller and Eric C. Jensen
Porous polymer adsorbents have
proven to be effective for collection
and preconcentration of organic ma-
terials in air streams. As part of the
Environmental Protection Agency,
Industrial Environmental Research
Laboratory-RTP Level 1 Procedure (1)
for environmental assessment, XAD-
2 resin, a polystyrene-divinylbenzene
porous polymer, is used in an adsorb-
ent trap for the collection of volatile
organic species. This resin trap is part
of the Source Assessment Sampling
System (SASS) which was designed
specifically for environmental sam-
pling of gaseous streams. One of the
prerequisities for the selection of a
material used for trapping species
from such a stream is that the material
introduce as small a blank value as
possible in relation to the sample
collected. If this blank is of sufficient
size, both qualitative and quantitative
determination of the materials trapped
by the resin becomes difficult.
This Project Summary was devel-
oped by EPA's Industrial Environ-
mental Research Laboratory, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The primary objective of this study
was to achieve a qualitative and quanti-
tative determination of the thermal
blank produced by XAD-2 resin as used
in the Level 1 Environmental Assess-
ment Procedure. Simulated-use condi-
tions were utilized to evaluate this
blank. While the bulkthermalstabilityof
the resin may be good, introduction of
contaminants on the milligram scale
can be sufficient to give a large blank
value in relation to total collected
material.
Consequently, in this study the mag-
nitude of the thermally-induced blank
was assessed primarily by measure-
ment of the Total Chromatographable
Organic (TCO) fraction of the resin
extract using Level 1 procedures. Also, a
gas chromatography/mass spectros-
copy (GC/MS) study of several of the
extracts was performed to identify
components of the blank.
In addition to the thermal blank
studies, the nature of the material
extracted upon cleaning of the resin
was studied, and a brief examination of
the stability of the resin with respect to
abrasion and tumbling was made to
determine whether physical handling
could contribute to an increase in the
overall blank.
Conclusions and
Recommendations
Resultant conclusions and recom-
mendations about the stability of XAD-2
resin for use in SASS trains are listed as
follows:
1.) Extensive cleaning is apparently
necessary just prior to use if one is to
avoid a large residual blank. Thiscan
be monitored by examining the TCO
material remaining in the cleaning
extraction solvent. Care must be
taken to ensure that what appears to
1 US GOVERNMENT PRINTING OFPICE 1961 -757-012/7171
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be a baseline signal from each of
these extracts is, in fact, baseline
and not a broad signal due to un-
resolved material.
2) Long-term storage of clean XAD-2
resin does not appear to be viable.
Measurable amounts of TCO material
either desorb from the resin or are
formed in a process involving slow
polymer degradation.
3) Storage up to several months maybe
feasible, but the Level 1 quality
control test should always precede
use. Physical handling appears not
to be a major source of blank material.
4) The thermal stability of XAD-2 with
regard to use for trace analysis is
especially poor above 70°C. Special
precautions should be taken to en-
sure that the resin is not heated
much beyond ambient temperature
(25°C) if a significant blank is to be
avoided.
5) Should the resin be heated inadver-
tently during the sampling procedure,
the components which may be ex-
pected in the TCO fraction are various
alkyl benzenes. The concentration of
these will depend on the length of
time the resin was heated, the actual
temperature of the resin, and possibly
the nature of the gas stream being
sampled.
C. H. Lochmiiller and Eric C. Jensen are with P.M. Gross Chemical Laboratories.
Duke University, Durham, NC 27706.
Larry D. Johnson is the EPA Project Officer (see below).
The complete report, entitled "XAD-2 Thermal Blank Determination," (Order No.
PB 81-172 264; Cost: $6.50, 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 Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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