United States Atmospheric Research and

Environmental Protection Exposure Assessment Laboratory

Agency Research Triangle Park, NC 27711

W.C. Eaton, L.B. Jaffe, E.E. Rickman, Jr., and R.K.M. Jayanty

E AP Project Summary

Field Tests of Chloroform

Collection/Analysis Methods

Research and Development EPA/600/SR-94/082 August 1993

The Clean Air Act Amendments of

1990 call for the regulation of numerous 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 dioxide bleaching process. Two candidate

methods were selected and field tested

for the collection and analysis of chloroform. 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 compared using the statistical procedures

listed in EPA Method 301, Field Validation of Emission Concentrations from

Stationary Sources. Based upon the

comparison, the charcoal tube method

was selected; revision and further testing 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 methods demonstrated acceptable precision.

The bias and precision of the revised

charcoal tube method were found to be

acceptable per EPA Method 301 specifications. The revised charcoal tube

method is recommended for use in the

collection and measurement of chloroform emissions from stationary

sources.

This Project Summary was developed

by 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).

Introduction

The Clean Air Act Amendments of 1990

call for regulation of toxic chemical species emitted from stationary sources. One

of the toxic species is chloroform, an organic 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 collection and analysis of chloroform and validate the method according to EPA Method

301, Field Validation of Emission Concentrations from Stationary Sources.

A review of source-level methods for

chloroform yielded two candidates for consideration. The first method (based on work

by the National Council of the Paper Industry for Air and Stream Improvement,

NCASI) uses activated charcoal to adsorb

chloroform, a 9:1 solution of hexane:methanol for desorption, and gas chromatography with electron-capture detection (GC/ECD) for quantification. The second method employs a collapsed Tedlar

plastic bag mounted inside a rigid container 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
2

chromatography with flame ionization detection (GC/FID). Both these methods were

studied in the laboratory prior to and following the first field evaluation.

The first field evaluation of the methods

took place at a paper mill hypochlorite

tower vent where the chloroform concentration was about 300 ppm. Results

showed that both methods met the EPA

Method 301 precision criterion but only

the charcoal tube method met the sampling bias criterion. Studies of the Tedlar

bag method were discontinued. Prior to

the second stage of field evaluation, improvements 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 chloroform concentration was about 220 ppm.

In these tests the revised charcoal 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 crystals on chloroform concentration, optimize

spiking and recovery procedures, and assess 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 studies of the charcoal tube method. The GC/

FID was calibrated with standards prepared using a pressure dilution technique

in which liquid chloroform is diluted with

nitrogen in a Summa stainless steel canister 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 prepared 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-scrubbing 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

cm3/min. 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 scrubber. 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 laboratory. The first system employed a precision needle valve to control flow from a

gas cylinder. It was used for the laboratory spike recovery study and for spiking

during the collection of presurvey samples.

The second system employed mass flow

controllers and was used for spiking charcoal 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 sampling line at a flow rate of 26 cm3/min.

Sampling continued for 20 min, and spiking occurred continuously during the first

18 min. Six samples were taken and four

extraction procedures were tried to determine 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 charcoal was not evaluated.

Field Testing and Methods

Validation

Field testing was conducted at two different sites. The primary objective of the

tests at the first location (Site A) was to

obtain and compare estimates of the precision and accuracy of the Tedlar bag and

charcoal tube methods under field conditions. The objective of studies at the second location (Site B) was to obtain precision 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 chloroform spike level for the validation study

could be set.

In accordance with the validation process 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 together, 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 sampling bias; and the bias difference between 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 systems as used at Site A is shown in Figure

1. On the first day of sampling, eight sets

of quadruplicate samples were taken using 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 schematic 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, replacement of the stainless steel spike injection

tee with Teflon, use of a mass flow controlled 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.
3

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 icebath temperature conditions, the recovery

of 242 ppm chloroform, passed over sodium 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 chloroform from five different spiked Tedlar bags

was 95 ± 3 percent. The average recovery of six spikes onto charcoal tubes was

90 ± 1 percent. The charcoal tube recoveries were essentially the same whether

the desorbing solution volume was 15 or

20 mL and whether the amount of methanol in hexane was 1 or 2 percent. No

chloroform was found on the backup section of the tube or on a second tube placed

downstream as a precaution against breakthrough.

Sample Stability

The stability of chloroform samples in

Tedlar bags was determined. Samples

were stored at room temperature and protected from light. Recovery of laboratorysupplied 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 charcoal tube methods. Source chloroform concentrations were approximately 230 ppm

by either method. No breakthrough of chloroform onto the backup section of the

charcoal sorbent tube occurred. Isothermal and temperature-programmed GC

analysis revealed no peaks other than

chloroform in the region of interest.

The charcoal tube and Teflon bag methods 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

Stainless steel

vent from

bleach

plant

0.25-in. OD Teflon tubing

(~10-ft. length, unheated)

A

B

C

D

100-cm3 glass/Teflon

syringe

Stainless steel injection tee

with silicone septum

Teflon fitting and Teflon "U" tube

packed with coarse crystals of

sodium thiosulfate pentahydrate

Ice bath (0° C)

Jumbo

charcoal

tubes

Charcoal Tube Method

Vent

Dry gas meter

Pump

Plastic lid with two

"quick-connect" fittings

2-gallon

glass pickle jar Tedlar Bag Method

0.25-in OD

Teflon tubing
4

charcoal tube method was revised to improve 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 concentrations of about 120 ppm at the vent.

Temperature-programmed GC/ECD analysis showed no peaks near that of chloroform. 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 operating just as it would have been used in

sampling from a vent. At site A, two charcoal tube samples showed an average

recovery of 90 percent of the designated

audit value. The Tedlar bag method’s recovery 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 indicated that the charcoal tube method performed better than the Tedlar bag method.

All further studies were made with the

charcoal tube method. A number of revisions 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

Figure 2. Diagram of revised sampling system for chloroform emissions.

Pump

Pressure regulator

Gas

cylinder

0 to 100-cm3/min

mass flow controller

A

B

Vent from

bleach plant

scrubber

Teflon fitting and

Teflon "U" tube

packed with

coarse crystals

of sodium

thiosulfate

pentahydrate

Water bath (~28° C)

Water

knockout

trap

Teflon

injection

tee

0.25-in. OD Teflon

tubing (~5-ft. length)

Heated stainless

steel probe with

Teflon or glass

liner

0.25-in. OD Teflon tubing

Jumbo

charcoal

tubes

0.125-in OD Teflon

tubing (~8-ft. length)

Charcoal Tube Method

Dry gas

meter

Vent

Pump

Drying tube
5

stainless steel spiking tee with a Teflon

tee; using mass-flow-controlled dynamic

spiking rather than syringe injection spiking; thermostatting the sodium thiosulfate

scrubber tube at approximately 28 °C instead of ice water temperature; and analyzing 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 performance of the methods are as follows.

Studies under isothermal and temperature-programmed conditions showed that

no interfering compounds were present in

the chromatographic region where chloroform appears. The two methods, as initially evaluated at the Site A mill, were

similarly precise (RSD of less than 5 percent 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 unacceptable for the Tedlar bag method (-59

ppm) and marginally acceptable (-43 ppm)

for the charcoal tube method. The sampling bias for the revised charcoal tube

method as employed at Site B was acceptable (-8 ppm) and significantly improved 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. Average 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 knockout trap be placed between the probe and

the sodium thiosulfate scrubber tube whenever water-saturated source gases are

expected or encountered. This will prevent water droplets from reaching the charcoal sampling tube and compromising its

collection efficiency.

Mention of trade names and commercial products does not constitute endorsement or recommendation for use.
6

W.C. Eaton, L.B. Jaffe, 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 Methods,” (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

EPA/600/SR-94/082

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