United States
Environmental Protection
Agency
Atmospheric Research and Exposure
Assesment Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-90/055 Aug. 1990
EPA Project Summary
Evaluation of an Anion Exchange
Resin for Sampling Ambient
Level Phenolic Compounds
Marcia Nishioka and Hazel Burkholder
The determination of human expo-
sure to polar volatile and semivolatile
organic compounds Is an area of in-
creasing importance to EPA. Since the
bioavailability of many polar compounds
is greater than for relatively non-polar
compounds, methods are needed for
the selective sampling and analysis of
these types of compounds. The sorbent
sampler described in this report pro-
vides a new capability of sampling for
acidic and phenolic vapor phase or-
ganic compounds.
The currently available method for
collection of vapor phase phenol and
methyl-phenols, as described in EPA's
Ambient Air Method TO-8, involves
aqueous sodium hydroxide impinger
collection. Solution sampling is, in gen-
eral, not practical for field sampling at
remote sites; in addition, this impinger
method has not been evaluated for col-
lection of chemically diverse and more
toxic phenolic species such as the
chloro- and nitro-phenols nor has it
been shown sensitive enough for deter-
minations at trace ambient levels.
Based upon these considerations, the
alternative method developed here uti-
lizing solid sorbent based sampling
may prove preferable to liquid based
Impinger methods.
The program described herฎ was
designed for evaluation of a solid sor-
bent, the an ion exchange resin AG MP-
1, for selective collection and retention
of vapor phase phenolic compounds.
The primary goal of the program was
development of sampling and analysis
conditions which would permit detec-
tion and quantification of diverse phe-
nolic and hydroxylated species at am-
bient levels of 1 ppbv. Phenols (and
other acid ic compounds) are retained on
AG MP-1 by formation of a chemical
bond; the reaction Is reversed to liberate
the phenols from the sorbent prior to
analysis. Because of the dominant con-
cern about collection and recovery, in-
vestigations here centered upon those
parameters which affect the formation of
the initial chemical bond between phe-
nolic analyte and sorbent and those
procedures that allow subsequent re-
versal of these reactions for quantitative
recovery of analytes.
Average recoveries of 89% (82-101 %)
were measured for 1 jig quantities of 13
chemically-diverse phenolic com-
pounds that were spiked into a heated
gas stream, sampled at 100 mL/min
through AG MP-1, extracted from the AG
MP-1, and concentrated prior to analy-
sis. Recovery of a solution spike of
these analytes to AG MP-1 without sub-
sequent gas sampling averaged 85% (76-
104%). Because recoveries from the two
spiking experiments were comparable,
it was concluded that vapor phase col-
lection was essentially quantitative.
This Project Summary was prepared
by the EPA's Atmospheric Research
and Exposure Assessment 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).
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Introduction
The currently available method for col-
loclion of vapor phase phenol and methyl-
phenols involves aqueous sodium hydrox-
ide imptnger collection. Solution sampling
is, In general, not practical forfield sampling
at remote sites; in addition, this impinger
method has not been evaluated for collec-
tion of chemically diverse and more toxic
phenolic species such as the chloro- and
nitro-phenols. Sorbent based sampling
methods are preferable to impinger meth-
ods. As an alternative to the impinger
method, PUF (polyurethane foam)-Tenax-
PUFsandwtch sorbent cartridges have been
evaluated recently for the collection of va-
porphase chforo-phenols. Whilethis method
provides high collection efficiencies for the
tetra- and pentachlorophenols, mono-
chtoro-phenols are not retained. These
collection differences suggest that phenol
and mono-functional phenols (e.g. methyl-
phenols, nitro-phenols) also will not be re-
tained by this sorbent.
The program described here was de-
signed for evaluation of a solid sorbent, the
anion exchange resin AG MP-1, for selec-
tive collection and retentbn of vapor phase
phenolic compounds. The primary goal of
the program was development of sampling
and analysis conditions which would permit
detection and quantification of diverse phe-
nolic and hydroxylated species at ambient
levels of 1 ppbv. The program also included
1) the development of methods for remov-
ing potential neutralinterferencecompounds
whteh could be retained by adsorption to the
sorbent polymer backbone, 2) evaluation of
stability of sorbent-bound analytes during
prolonged storage, and 3) stability of sor-
benl-bound analytes toward nitration by
ambient HNO3. In addition, the program
included preliminary field sampling evalua-
tion of the sorbent. Field collection was
carried out attwo sites in northern Delaware;
three additional samples were collected in
the Columbus, Ohio area.
Anton exchange resins/sorbents are
typically suspended in aqueous or organic
mediaforchromatographicseparations. For
the strongly basic anion exchange resins,
such as AG MP-1, the charge isfixed by the
structure of the resin; positively charged
quaternary amine groups are chemically
bound to a styrene divinylbenzene lattice;
the negatively charged counterion to the
amlne can be exchanged. The quaternary
amlne retains its charge whether or not the
resin is suspended in solution. AG MP-1,
available from Bfo-Rad Laboratories, is a
macroporous strong anion exchange resin.
Because of the highly crosslinked and rela-
tively rigid styrene divinylbenzene back-
bone, AG MP-1 does not shrink or swell
excessively during extraction of analytes
with solvents and is not crushed easily
during sampling and handling. The high
degree of porosity allows retention of larger,
less polar organic acids and phenols so as
to increase contact time for formation of the
chemical bond between analyte and qua-
ternary amine. AG MP-1 is similar to the
XAD-2 resins in physical properties such as
ease of handling, mechanical strength, and
color.
For sorbent sampling based upon ad-
sorption, as with XAD-2, collection and re-
tention are both described by chromato-
graphic theory, the dominant factor being
partition of analyte between gas and solid
phase. Forthe anion exchange resin evalu-
ated here, collection and retention are two
separate issues. Phenols (and other acidic
compounds) are retained on AG MP-1 by
formation of achemical bond;the reaction is
reversed to liberate the phenols from the
sorbent prior to analysis. Schematic rep-
resentation of these steps is shown in Fig-
ure 1.
Experimental
For experiments conducted on this
program, AG MP-1 was converted from the
manufacturer-supplied CI" form to the OH'
form to obtain the strongest possible aque-
ous base (OH-) for exchange. The OH" on
the resin will readily abstract a proton from
phenolic and acidic organic analytes and
thus effect attachment of an analyte anion
to the quaternary amine exchange site.
Analyte anions are displaced from the resin
later by application of an acid of greater
strength than the analytes, in this case 2%
cone. HCI in 15:85 (v:v) methanolrmethyl-
t-buty I ether. Under these conditions the Cr
form of the resin is generated and the or-
ganic analyte is regenerated as a neutral
molecule. Because formation of the
chemical bond ensures retention of analytes,
retention is the lesser important of the two
considerations. Phenols will be retained
unless sampling occurs in atmospheres of
very high HNO, concentrations (or other
acid whose pKa is less than that of the
phenols of interest) where HNO3 may ei-
ther displace phenols from the sorbent or
nitrate the phenols and, thus, form artifacts.
Because of the dominant concern about
collection, investigations here have cen-
tered upon those parameters which affect
the formation of the initial chemical bond
between phenolic analyte and sorbent.
The target level for phenols in these
laboratory experiments was 1 u.g for each
analyte. The 1 _u.g level represents the
average quantityforphenols which, if present
at 1 ppbv in the atmosphere, would be
collected during a 24 hr period when sam-
pling at 100 mL/min with 100% collection
efficiency at ambienttemperature and pres-
sure. For phenols of interest, the quantity
collected covers a range from 0.5 \ig for
phenol to 1.5 u.g for pentachlorophenol.
The target level for analysis in these labora-
tory experiments has been 1 ng/u.L. This
quantification level is required for the analy-
sis of the 1 u,g spike quantities when fully
recovered and concentrated to a 1 mL vol-
ume.
After collection and prior to analysis,
phenols are subjected to two extraction
procedures: extraction from AG MP-1 with
an acidified solvent (HCI in methanol/methy I-
t-butyl ether) and then extraction from that
acidified sorbent eluate into a neutral sol-
vent. The experimental plan for the pro-
gram involved, in sequence: (1) develop-
ment and evaluation of GC and GC/MS
analysis conditions; (2) evaluation of
methods to extract phenols from acidified
sorbent eluate; (3) evaluation of methods to
extract phenols (and neutral compounds)
from sorbent; (4) evaluation of parameters
which affect collection of vapor phase
phenols, and finally; (5) analysis of field-
collected samples.
Thefollowing experimental procedures
for (both laboratory and field work) were
developed in this program:
Preparation and storage of standard
analyte mixtures
Activation and storage of resin
Analysis methods
a. GC/FID for laboratory tests at high
levels
b. GC/ECD for laboratory tests for low
levels of nitro- and chloro-phenols
c. GC/FID for neutral interference
compounds
d. GC/MS for field collected samples
Extraction of phenols from acidic
methanol:methyl-t-butyl ether
Extraction of phenols from AG MP-1
Extraction of neutral interference com
pounds from AG MP-1
Method for vapor spike and
simulatedsampling of phenols
Method for evaluating stability of sor-
bent bound phenols
a. Stability during one-month storage
b. Stability toward HNO3
Collection of field samples
a. preparation of sorbent tubes
b. collection of field samples
c. extraction and analysis
The many and varied exploratory ex-
periments performed to develop this new
methodology cannot be discussed in detail
in this summary; procedures are presented
in detail in the complete report.
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Retention and Elution of Phenols from AG MP-1
Initial Conditions:
AG MP-1 Suspended in
Solvent in Open
Chromatography Column
or Dry in Sorbent
Sampling Tube
\
N+ OH-
N + OH"
N+ OH-
Attach Phenol
to AG MP-1
OH
Eluted Material:
HaO
Neutral Molecules
Basic Molecules
Remove Phenol
From AG MP-1
HCI/Methanol
\/
N+ cr
\
N+ cr
N+ cr
\
Eluted material:
HO
Excess HCI
Methanol
Figure 1. Schematic representation of collection of phenols with AG MP-1 and subsequent elution.
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Results and Discussions
Detailed presentations of results and
relevant discussion are given in the full
report for each laboratory and field experi-
ment. Forthis summary, only highlights are
presented for selected collection/recovery
experiments; these are representative of
the overall effort.
The parameter tests resulted in a
nominally optimized procedure forsampling
vapor phase phenolic compounds and
subsequently extracting them quantita-
tively. This is a laboratory experiment per-
formed under the best conditions using a
clean helium carrier gas. To control for any
matrix effects during subsequent experi-
ments with ambient airrnatrices, this method
was used for pre-spiking sorbent tubes
with deuterated phenolic compounds to
further test recoveries. The optimized con-
figuration of mesh size (200-400), flow rate
(100 ml/min), and linear velocity (1.75 cm/
sec) resulted in the recovery data presented
In Table 1 for 13 phenolic compounds rep-
resenting phenol and methyl phenols, chlo-
rophenols, nitrophenols and related com-
pounds.
Table 2 presents recovery data for
deuterated compounds after real field
sampling, both for compounds spiked prior
to Jieldsampllng and forlaboratory recovery
standards. These representative results
indicate that overall recoveries are more
scattered than for the laboratory tests and
that some of this scatter could be caused
by the laboratory recovery procedure.
Based upon results from all of the labo-
ratory tests, sorbent mesh size and super-
ficial linear sampling velocity were those
parameters which affected collection effi-
ciency most dramatically. Sampling was
most efficient with the 200-400 mesh AG
MP-1 (particle diameter range of 38-75 u.m)
at a linear velocity of 1.75 cm/sec. Field-
collected samples showed that neutral
species such as aliphatic and aromatic hy-
drocarbons were retained by this sorbent in
addition to the phenolic and acidic species.
For this reason, extraction methods were
developed forselective extraction of neutral
species priorto extraction of phenols. These
methods were developed for neutral specie
levels 1000 times greater than anticipated
phenol levels and resulted in greater than
90% recovery of spiked neutral species.
Recommendations
Based on the results of this study,
sampling at 100 mL/min for vapor phase
phenols may be applied best to air heavily
impacted by specific emission/pollution
sources. The method evaluated here may
not provide sufficient sensitivity for ambient
levels less than 1 ppbv. Therefore, the
recommendations listed here are divided
into two categories, those specific to the
further evaluation and development of the
sorbent sampler described here and those
specif ic to development of a similar AG MP-
1 based sampler compatible with higher
sampling rates. It is recommended that
further study of the following areas be per-
formed:
Existing Method:
- Evaluation of the retention of vapor
phase phenols by acid-washed glass
fiber and quartz fiber filters.
- Evaluation of the components of labo-
ratory AG MP-1 method blanks, with
particular emphasis on phenolic and
acidic species.
- Evaluation of extraction procedures
which ensure complete recovery of
phenolic/acidic analytes following ex-
tended (12-24 hr) sampling periods at
100 mL/min.
- Evaluation of the collection efficiency
of AG MP-1 sorbent for phenols from
very dilute gas streams.
- Further evaluation of stability of
phenols and extraction efficiency from
AG MP-1 following storage.
- Furtherevaluationofstabilityofphenols
toward ambient levels of nitrating gases.
New Sampler (higher sampling
rates):
- Development of an AG MP-1 based
sorbent sampler for operation at 1 -2 L/
min and at 10-100 L/min to increase
sensitivity.
- Development of an AG MP-1 based
passive sampler with nominal sam-
pling rate of 80-100 mL/min for fast
sampling without electrical require-
ments.
- Evaluation of the anion exchange
membrane AG 1-X8 (available from
Bio-Rad; 90% AG 1, chemically similar
Table 1, Recovery of Phenols after Vapor Spike: 200-400 Mesh AG MP-1; 1 u.g Phenol
100 mL/min Sampling Hate; 11 mm I.D. Sorbent Tuba.
Analyte
Phenol
2-CH3-phenol
4-CH,-phenol
2,3-diCrVphenol
2-CI-phenol
4-CI-pheno!
2,4-diCI-phenol
Pentad-phenol
2-NO2-phenol
3-NO,-phenol
6-CH3-2-NO-phenol
2-OH-benzafdehyde
2-OH-biphenyl
% Recovery
91
87
92
82
85
89
92
82
82
99
92
101
86
DM)(a)
1
1
8
2
5
2
2
(b)
(b)
5
2
7
2
(a) n - 2; % deviation from the mean.
(b) Single analysis; analyte recoveries were 33% and 6% in 2nd sorbent extract for 2-NO2-phenol and pentad-phenol, respectively.
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Table 2. Recovery ofDeuterated Compounds from Columbus, Ohio Collected Samples.
Sample Designation % Recovery
Municipal Bus Garage
Municipal Compost Facility
Lab Blank
Phenol-
103
98
69
Field Recovery Standard
20 ng
4-NO.,
80
39
47
Lab Recovery Standard
5 ua
2,4-diCI-
phenol-d 4 phenol-d.
100
68
89
4-CH3-
phenol-d
108
104
90
2-N02-
phenol-d
120
42
66
2-CI-
phenol-d 4
106
91
62
to AG MP-1, incorporated into a
polytetrafluoroethylene matrix) as an
inlet filter on canisters or Tenax sam-
plers.
Evaluation of the anion exchange
membrane AG 1-X8 as the inner sur-
face of an anular denuder sampling
system for determining phase distribu-
tion for the less volatile phenolic com-
pounds.
Conclusions
The newly developed method for the
determination of ambient phenolic com-
pounds was successfully optimized and
laboratory tested. Representative com-
pounds exhibit an average collection/re-
covery of 89% for 1 |j.g quantities sampled at
100 ml/min through the anion exchange
sorbent AG MP-1. The method is a viable
approach for trace-level determination of
ambient phenolic compounds. Parameter
testing and use of deuterated recovery
standards indicate that further work is, nec-
essary to optimize sensitivity via sampler
development (sorbent tube and pump-
systems), and to further develop and opti-
mize laboratory extraction procedures.
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Ware/a Nishhka and Hazel Burkholder are with Battelle Columbus Laboratories,
Columbus, OH 43201.
Joachim D. Ptell is the EPA Project Officer (see below).
Tha complete report, entitled "Evaluation of an Anion Exchange Resin for Sampling
Ambient Level Phenolic Compounds," (Order no. PB90 246 091 AS; Cost:
$23.00 cost 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:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-90/055
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