United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-94/082 August 1993
EPA Project Summary
Field Tests of Chloroform
Collection/Analysis Methods
W.C. Eaton, LB. Jaffe, E.E. Rickman, Jr., and R.K.M. Jayanty
The Clean Air Act Amendments of
1990 call for the regulation of numer-
ous toxic chemical species emitted
from stationary sources. One of the
toxic species is chloroform, an organic
compound emitted from paper mills
employing the chlorine/chlorine diox-
ide bleaching process. Two candidate
methods were selected and field tested
for the collection and analysis of chlo-
roform. Collection efficiencies of a
Tedlar bag/glass lung method and a
charcoal adsorbent tube method were
compared. Samples from each method
were collected from the hypochlorite
tower vent (300 ppm chloroform source)
of a paper mill bleach plant in South
Carolina. The two methods were com-
pared using the statistical procedures
listed in EPA Method 301, Field Valida-
tion of Emission Concentrations from
Stationary Sources. Based upon the
comparison, the charcoal tube method
was selected; revision and further test-
ing of that method was performed at a
second paper mill bleach plant in North
Carolina.
Results from a number of laboratory
studies of the methods, as well as from
the presurvey and field sampling, are
presented and discussed. Both meth-
ods demonstrated acceptable precision.
The bias and precision of the revised
charcoal tube method were found to be
acceptable per EPA Method 301 speci-
fications. The revised charcoal tube
method is recommended for use in the
collection and measurement of chloro-
form emissions from stationary
sources.
This Project Summary was developed
by EPA's Atmospheric Research and
Exposure Assessment Laboratory, Re-
search 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 Clean Air Act Amendments of 1990
call for regulation of toxic chemical spe-
cies emitted from stationary sources. One
of the toxic species is chloroform, an or-
ganic compound emitted from paper mills
that employ the chlorine/chlorine dioxide
bleaching process. The objective of this
work was to conduct laboratory and field
studies to select a method for the collec-
tion and analysis of chloroform and vali-
date the method according to EPA Method
301, Field Validation of Emission Concen-
trations from Stationary Sources.
A review of source-level methods for
chloroform yielded two candidates for con-
sideration. The first method (based on work
by the National Council of the Paper In-
dustry for Air and Stream Improvement,
NCASI) uses activated charcoal to adsorb
chloroform, a 9:1 solution of hex-
ane:methanol for desorption, and gas chro-
matography with electron-capture detec-
tion (GC/ECD) for quantification. The sec-
ond method employs a collapsed Tedlar
plastic bag mounted inside a rigid con-
tainer and connected to the exterior via a
quick-connect fitting. As the container's
interior is evacuated, the bag expands
and draws in a sample. Analysis is by gas
Printed on Recycled Paper
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chromatography with flame ionization de-
tectfon (GC/FID). Both these methods were
studied in the laboratory prior to and fol-
lowing the first field evaluation.
The first field evaluation of the methods
took place at a paper mill hypochlorite
tower vent where the chloroform concen-
tration was about 300 ppm. Results
showed that both methods met the EPA
Method 301 precision criterion but only
the charcoal tube method met the sam-
pling bias criterion. Studies of the Tedlar
bag method were discontinued. Prior to
the second stage of field evaluation, im-
provements were made in the sampling,
spiking, and analysis procedures for the
charcoal tube method. The method was
then tested at another paper mill at a
chlorine scrubber vent where the chloro-
form concentration was about 220 ppm.
In these tests the revised charpoal tube
method met all validation criteria specified
by EPA Method 301.
Experimental Approach
Laboratory Evaluations
Laboratory studies were conducted to
test the effects of sodium thiosulfate crys-
tals on chloroform concentration, optimize
spiking and recovery procedures, and as-
sess sample stability. GC/FID with a
packed column (1% SP-1000 on Carbopak
B 60/80, 1/8 in. x 8 ft. SS) was used in
studies of the Tedlar bag method; GC/
ECD with a capillary column (DB-624, 30-
m, 0.53-mm diameter) was used in stud-
ies of the charcoal tube method. The GC/
FID was calibrated with standards pre-
pared using a pressure dilution technique
in which liquid chloroform is diluted with
nitrogen in a Summa stainless steel can-
ister to produce known concentrations. The
FID response was linear (r2 - 0.99992)
over the range of 0 to 597 ppm. The GC/
ECD was calibrated with standards pre-
pared by diluting liquid chloroform in
hexane:methanol desorbing solution. The
ECD response was linear (r2 = 0.998)
over the range of 0 to 10,500 ng/mL
To test the effect of a chlorine-scrub-
bing material (sodium thiosulfate crystals)
on chloroform, a Teflon U-tube containing
either dry or wet crystals was assembled
and 242 ppm chloroform in nitrogen was
passed through the tube at 400 cm3/min.
The gas entering and exiting the tube was
analyzed by GC/FID to determine changes.
The spiking procedure and equipment
used in the first field test was studied in
the laboratory. Cylinder gas containing 242
ppm chloroform in nitrogen was passed
through a manifold from which the Tedlar
bag method train sampled at about 350
cmVmin. While the sampling train was in
operation, a 100 cm3 volume syringe was
used to slowly introduce spiking gas (4490
ppm chloroform in N2) through a septum
in a stainless steel tee mounted in the
sampling line just upstream of the scrub-
ber. The concentrations of spiked and
unspiked samples were then compared.
For the second field test, two types of
dynamic, flow-controlled spiking systems
were calibrated and tested in the labora-
tory. The first system employed a preci-
sion needle valve to control flow from a
gas cylinder. It was used for the labora-
tory spike recovery study and for spiking
during the collection of presurvey samples.
The second system employed mass flow
controllers and was used for spiking char-
coal tubes during the second field test.
For the charcoal tube spiking recovery
study, the sampling train was set up as it
was in the field except that the sodium
thiosulfate tube was omitted. A heated
manifold and humidifier system supplied
"source gas" as dry or humidified house
nitrogen at 58 °C. The sample was pulled
into a jumbo-size charcoal tube (1800 mg
in the front section; 200 mg in the back
section) at a flow rate of 286 cm3/min;
chloroform from a 4376 ppm cylinder was
added through a Teflon tee in the sam-
pling line at a flow rate of 26 crrvVmin.
Sampling continued for 20 min, and spik-
ing occurred continuously during the first
18 min. Six samples were taken and four
extraction procedures were tried to deter-
mine which produced the best recovery.
Sample stability of chloroform in Tedlar
bags was studied for laboratory-generated
samples and actual source samples by
analysis of bag contents several times
during an 18-day period. The stability of
chloroform adsorbed onto activated char-
coal was not evaluated.
Field Testing and Methods
Validation
Field testing was conducted at two dif-
ferent sites. The primary objective of the
tests at the first location (Site A) was to
obtain and compare estimates of the pre-
cision and accuracy of the Tedlar bag and
charcoal tube methods under field condi-
tions. The objective of studies at the sec-
ond location (Site B) was to obtain preci-
sion and accuracy estimates of a revised
version of the charcoal tube method and
check their acceptability per EPA Method
301 criteria. A pre-survey visit was made
to each site to determine the suitability of
the site for testing and to collect several
samples for analysis so that the chloro-
form spike level for the validation study
could be set.
In accordance with the validation pro-
cess of Method 301, the field test of the
method consisted of four sampling trains
run in parallel for six runs (24 samples
total). The four probes were bound to-
gether, inserted into a single port, and
placed perpendicularly to the flow of gas
in the center of the vent. During each
run, two of the four trains were spiked
with chloroform. The precision of the
method was estimated using the standard
deviation of the difference between the
spiked or unspiked pairs; the accuracy of
the method was estimated as the sam-
pling bias; and the bias difference be-
tween two methods was calculated by use
of the t-statistic.
Field Site A: Hypochlorite Tower
Vent
The sample collection site was a small
port in the 19.25-in. diameter stainless
steel vent of a hypochlorite tower of a
bleach plant. The vent gas temperature
was 57 °C. Four unheated, 0.25-in.-OD
Teflon tube probes were inserted through
a thick rubber sheet that was taped across
the vent port. The probe inlets extended
to the center of the vent pipe and were
separated from each other by about 3
inches. A schematic of the sampling sys-
tems as used at Site A is shown in Figure
1. On the first day of sampling, eight sets
of quadruplicate samples were taken us-
ing the charcoal tube method. Two runs
were discarded due to insufficient flow or
leaks. On the second day, seven sets of
samples were taken using the Tedlar bag
method. One run was discarded due to a
leak.
Field Site B: Chlorine Scrubber
Vent
The sample collection site was a port in
a 30-in.-diameter fiberglass vent from a
bleach plant chlorine scrubber. The vent
gas temperature was approximately 61
°C. Four heated stainless steel probes,
each containing a 3/8-in. OD liner of Teflon
or glass tubing were bound together and
inserted into a single port of the vent and
positioned so that the inlets were in the
approximate center of the vent. A sche-
matic of the sampling system used at Site
B is shown in Figure 2. A revised version
of the charcoal tube method was used at
Site B. Significant revisions in the method
were: use of a heated probe, replace-
ment of the stainless steel spike injection
tee with Teflon, use of a mass flow con-
trolled dynamic spiking system rather than
a gas syringe, thermostatting the sodium
thiosulfate scrubber tube to ~28 °C rather
than 0 °C, and analysis by automated,
rather than manual, injection to the GC/
ECD. On the first day of sampling, five
sets of quadruplicate samples were taken.
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Charcoal Tube Method
Stainless steel
vent from
bleach
plant
0.25-in. OD Teflon tubing
(~10-ft length, unheated)
Jumbo
charcoal
tubes
100-cm3glassAeflon
syringe
Stainless steel injection tee
with silicone septum
Teflon fitting and Teflon "U" tube
packed with coarse crystals of
sodium thiosulfate pentahydrate
Vent
u Dry gas meter
Tedlar Bag Method
Plastic lid with two
"quick-connect" fittings
2-gallon
glass pickle jar
Figure 1. Diagram of initial sampling system for chloroform emissions.
Two additional sets were taken the next
day. However, data from these two sets
could not be used due to excess water
flooding into the charcoal tube, limiting its
collection efficiency.
Results
Laboratory Evaluations
Effects of Sodium Thiosulfate on
Chloroform Concentrations
Under dry or moist and room or ice-
bath temperature conditions, the recovery
of 242 ppm chloroform, passed over so-
dium thiosulfate crystals at 400 cm3/min,
was always better than 95 percent. It is
concluded that the crystals did not affect
chloroform concentration appreciably.
Spiking and Recovery Studies
The average recovery of chloro-
form from five different spiked Tedlar bags
was 95 + 3 percent. The average recov-
ery of six spikes onto charcoal tubes was
90 ± 1 percent. The charcoal tube recov-
eries were essentially the same whether
the desorbing solution volume was 15 or
20 mL and whether the amount of metha-
nol in hexane was 1 or 2 percent. No
chloroform was found on the backup sec-
tion of the tube or on a second tube placed
downstream as a precaution against break-
through.
Sample Stability
The stability of chloroform samples in
Tedlar bags was determined. Samples
were stored at room temperature and pro-
tected from light. Recovery of laboratory-
supplied chloroform (250 ppm) was 96
percent six days after filling the bag. For
field samples that measured 334 and 540
ppm two days after collection, recoveries
18 days later were 91 and 90 percent,
respectively. To achieve better than 90
percent recovery, analysis of chloroform
collected in Tedlar bags should occur
within 10 days after collection. Although
no stability studies of chloroform adsorbed
onto charcoal or desorbed into solvent
were performed in this study, previous
studies indicate that ice-cooled charcoal
tubes should be extracted and promptly
analyzed within two weeks after sample
collection (2). Analysis of the Tedlar bag
or charcoal tube field samples in this study
occurred within two to seven days after
collection.
Field Testing and Methods
Evaluations
Field Site A: Hypochlorite Tower
Vent
The presurvey results from Site A were
similar for both the Tedlar bag and char-
coal tube methods. Source chloroform con-
centrations were approximately 230 ppm
by either method. No breakthrough of chlo-
roform onto the backup section of the
charcoal sorbent tube occurred. Isother-
mal and temperature-programmed GC
analysis revealed no peaks other than
chloroform in the region of interest.
The charcoal tube_and Teflon bag meth-
ods showed very good precision (less than
5 percent RSD for spiked samples) during
field validation testing where the vent's
chloroform concentration was about 300
ppm. The average recovery of the spike
was 82 ± 13 percent for the charcoal tube
method and 74 +10 percent for the Tedlar
bag method. A statistical analysis per
Method 301 showed the bias of -43 ppm
was acceptable for the charcoal tube
method but the Tedlar bag method's bias
of -59 ppm was unacceptable. As noted in
the Experimental Approach section, the
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charcoal tube method was revised to im-
prove its performance before use at field
site B and plans to further develop the
Tedlar bag method were discontinued.
Field Site B: Chlorine Scrubber
Vent
A revised charcoal tube method was
used for testing at Site B. The presurvey
sample results indicated chloroform con-
centrations of about 120 ppm at the vent.
Temperature-programmed GC/ECD analy-
sis showed no peaks near that of chloro-
form. In the field validation study at the
same vent, this time at about 220 ppm
chloroform, the paired trains of the method
showed precision to be within 5 percent
RSD. The average recovery of the spiked
samples was 95 ± 7 percent. The bias of -
8 ppm was much improved and well within
the acceptable limits of Method 301.
Quality Assurance
A cylinder containing chloroform at 334
ppm in dry nitrogen was used to provide
performance audit samples at field test
Sites A and B. The audit gas was sampled
from a glass manifold using the charcoal
tube or Tedlar bag sampling train operat-
ing just as it would have been used in
sampling from a vent. At site A, two char-
coal tube samples showed an average
recovery of 90 percent of the designated
audit value. The Tedlar bag method's re-
covery was 84 percent based on a single
sample. At Site B the charcoal tube
method's average recovery of audit gas
for four samples was 90 ± 0.7 percent.
Conclusions and
Recommendations
The data from site A field tests indi-
cated that the charcoal tube method per-
formed better than the Tedlar bag method.
All further studies were made with the
charcoal tube method. A number of revi-
sions to the sample collection and spiking
procedure for the charcoal tube method
were made, based on the results of the
first field study. These revisions included:
heating the sample probe; replacing the
Pressure regulator
Vent from
bleach plant
scrubber
Gas
cylinder
Oto 100-cm3/min
mass flow controller
Heated stainless
steel probe with
Teflon or glass
liner
- 0.125-inOD Teflon
tubing (~8-ft. length)
Charcoal Tube Method
Dry gas
meter
Vent
0.25-in. OD Teflon
tubing (~5-ft. length)
Teflon fitting and
Teflon "U" tube
packed with
coarse crystals
of sodium
thiosulfate
pentahydrata
Water bath (-28° C)
Figuro 2. Diagram of revised sampling system for chloroform emissions.
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stainless steel spiking tee with a Teflon
tee; using mass-flow-controlled dynamic
spiking rather than syringe injection spik-
ing; thermostatting the sodium thiosulfate
scrubber tube at approximately 28 °C in-
stead of ice water temperature; and ana-
lyzing the extracts of the charcoal tubes
with an automated gas chromatograph
sample injection system. A validation study
of the revised charcoal tube method was
conducted at the bleach plant scrubber of
a paper mill identified as site B. Results of
the latter study were much improved over
those of the former study and met the
requirements of EPA Method 301.
Conclusions concerning the perfor-
mance of the methods are as follows.
Studies under isothermal and tempera-
ture-programmed conditions showed that
no interfering compounds were present in
the chromatographic region where chloro-
form appears. The two methods, as ini-
tially evaluated at the Site A mill, were
similarly precise (RSD of less than 5 per-
cent for unspiked or spiked samples) and
well within the acceptable limits specified
by Method 301. Precision estimates for
the charcoal tube method at Site B were
also less than five percent. The sampling
bias for the site A study results was unac-
ceptable for the Tedlar bag method (-59
ppm) and marginally acceptable (-43 ppm)
for the charcoal tube method. The sam-
pling bias for the revised charcoal tube
method as employed at Site B was ac-
ceptable (-8 ppm) and significantly im-
proved over results from Site A. Average
spike recovery at Site A was 74 percent
for the Tedlar bag method and 82 percent
for the initial charcoal tube method. Aver-
age spike recovery at Site B, using the
revised charcoal tube technique, was 95
percent.
It is recommended that the charcoal
adsorption tube method, as revised, be
accepted for use in field sampling studies
of chloroform. The precision of the method
is quite good and the bias is reasonable.
It is also recommended that a water knock-
out trap be placed between the probe and
the sodium thiosulfate scrubber tube when-
ever water-saturated source gases are
expected or encountered. This will pre-
vent water droplets from reaching the char-
coal sampling tube and compromising its
collection efficiency.
Mention of trade names and commer-
cial products does not constitute endorse-
ment or recommendation for use.
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W.C, Eaton, LB. Jaffa, E.E. Rickman, and R.K.M. Jayanty are with Research
Triangle Institute, Research Triangle Park, NC 27709. L Grosshandler and N.
Harden are with Entropy Inc., Research Triangle Park, NC 27709.
Frank W. Wilshire is the EPA Project Officer (see below)
The complete report, entitled "Field Tests of Chloroform Collection/Analysis Meth-
ods, " (Order No. PB94-176948/AS; Cost: $17.50; 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:
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
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