EPA/600/A-93/124
Development and Validation of a Source Test Method for
2,4-Toluene Diisocyanate
S.C. Foster and J.F. McGaughey
Radian Corporation
Research Triangle Park, NC 27709
and
F.W. Wilshire and J.E. Knoll
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
ABSTRACT
Four isocyanates are listed for regulation in the Clean Air
Act Amendments of 1990: hexamethylene-1,6 diisocyanate, methylene
diphenyl diisocyanate, and 2,4-toluene diisocyanate, each of which
is used in the production of polymers, and methyl isocyanate which
is an intermediate in the manufacture of the insecticide carbaryl
(i.e., Sevin®dust).
To support projected regulations, a study is under way to
produce a source sampling and analysis method for the four
pollutants cited above. In the procedure under development, the
isocyanates are collected in an absorbing solution and derivatized
with l-(2-pyridyl)piperazine and analyzed by HPLC with UV
detection. A system was developed in the laboratory to generate
isocyanate atmospheres for optimization of sampling parameters and
chromatographic conditions. The accuracy and precision of the
method is determined in the field using train spiking and
multiprobe sampling following the procedures outlined in EPA Method
301.
A field test of the isocyanate method, following EPA Method
301 procedures, was performed at a flexible foam manufacturer in
the Greensboro-High Point, North Carolina area. Results were
excellent, with analyte spike recoveries of 91% ± 6%. The method's
limit of quantitation (LOQ) was determined to be 351 ng of TDI/M3.
INTRODUCTION
A class of compounds identified as isocyanates are contained
in the list of 189 pollutants to be regulated by the Environmental
Protection Agency under Title III of the Clean Air Act Amendments1
(CAAA) of 1990. There are four isocyanates of interest in the
CAAA; methyl isocyanate (MI), hexamethylene 1,6- diisocyanate
(HDI), methylene diphenyl diisocyanate (MDI), and 2,4-toluene
diisocyanate (TDI).
Isocyanates are used extensively throughout industry. A few
examples of their use are the production of flexible foam products,
synthetic rubber products, insecticides, enamel wire coatings, and
in the pressed board industry. Foam materials alone are widely
used for such diverse items as toys, bedding, seat cushions,
packing material, flotation devices, and as sorbents in the
environmental field. Because of their widespread use, isocyanates

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possess the potential to affect many who are sensitive to this
class of chemical compounds. Some of the adverse physiological
effects associated with exposure to isocyanates are severe skin and
eye irritations, eczema, nausea, and bronchial asthma.2 An example
of the concerns expressed about human exposure to the isocyanates
is demonstrated by the NIOSH IDLH level (concentration considered
Immediately Dangerous to Life or Health) for 2,4-toluene
diisocyanate, which is listed at 10 ppm.3
Several critical problems exist when sampling for isocyanates.
They polymerize in the presence of concentrated alkaline compounds,
decompose upon exposure to water and alcohols, discolor upon
exposure to sunlight, and form toxic gases, such as carbon monoxide
and hydrogen cyanide, upon decomposition.	Consequently,
isocyanates must be collected rapidly and stabilized immediately
with a derivatizing reagent to insure sample integrity.
The EPA's Source Methods Research Branch, in the Atmospheric
Research and Exposure Assessment Laboratory, Research Triangle
Park, North Carolina through a contract with Radian Corporation,
Research Triangle Park, NC, has developed a method for the
collection, identification, and measurement of one of the
isocyanates of interest; 2,4-toluene diisocyanate. In this method,
samples are collected at the source using a modified EPA Method 5
sampling train. Stack gas is withdrawn at a flow rate of 0.5
ft3/min. for approximately sixty minutes through a heated, glass-
lined probe and into two impingers containing a solution of the
derivatizing reagent, l-(2-pyridyl)piperazine in toluene. The
first impinger is fitted with a water-cooled condenser, on the
outlet of the impinger, to minimize carryover of the organic
solvent into the second impinger. The 2,4-toluene diisocyanate
reacts with the derivatizing reagent to form a stable TDI/urea
derivative. When sampling is completed, the probe and connecting
glassware are rinsed with toluene and acetonitrile and the rinses
are saved for laboratory analysis. Each impinger solution
(TDI/urea derivative) is recovered separately and saved for
laboratory analysis. All samples are stored in a cooler at 0 to 4°
C until returned to the laboratory for analysis by High-Performance
Liquid Chromatography (HPLC with UV detection). Quantitation is by
a standards/retention time comparison procedure.
EXPERIMENTAL
Laboratory Evaluation
The laboratory study was initially set up to meet seven
objectives for the four isocyanates of interest. However, midway
through the laboratory study, budget constraints required the focus
to be shifted to only one of the isocyanates of interest. After
discussions with personnel in the EPA's Office of Air Quality
Planning and Standards, it was decided to focus our efforts on 2,4-
toluene diisocyanate. The seven objectives originally planned for
all of the isocyanates were followed for TDI and are listed in
Table 1. Some of the objectives were also met for the other
isocyanates of interest and are also listed in Table 1.
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Derivative Formation
Efforts to form a stable isocyanate/urea derivative for all
four isocyanates, using ethanol as the derivatizing reagent were
only marginally successful. An absorption solution was prepared by
adding 1 gram of KOH to 500 mL of 99.9% ethanol. Standard
solutions of each of the isocyanates were prepared by adding the
isocyanate directly to 5 mL each of the ethanol/KOH solution as
follows: 30 mg of MDI? 10 uL of MI, HDI, and TDI. Solid
derivatives for MDI, HDI, and TDI were obtained, but formation of
a derivative for MI was unsuccessful. Chromatograms for the
derivatized and underivatized isocyanates were compared. No
chromatographic peaks were observed for MI or HDI either
derivatized or underivatized, however, peaks were detected for TDI
and MDI.
Previous work by Goldberg, et al.4, using l-(2-
pyridyl)piperazine as the derivatizing agent, investigated
collecting ambient air samples in midget impingers. Since no
current source method for isocyanates exists, the secondary amine,
1-(2-pyridyl)piperazine [1,2PP] was investigated as a possible
alternative derivatizing reagent for ethanol. Using the 1,2PP as
the derivatizing reagent resulted in the formation of solid
derivatives for all of the isocyanates of interest. Each
isocyanate was prepared in a separate 200 mL flask. Approximately
0.2 grams of TDI, HDI, MDI was added to separate solutions of
0.3 mL of 1,2PP and 10 mL of acetonitrile (ACN). The solutions
were allowed to stand for 24 hours to insure enough time for the
reaction to take place. Each derivative was then rinsed with 150
mL of distilled water and allowed to air dry before being
redissolved with acetonitrile and brought to a standardized volume
prior to analysis by HPLC. A derivative for the MI was prepared by
transferring 100 uL of MI to 1 mL of ACN and adding 300 uL of
1,2PP. The solution was shaken for five minutes and then diluted
1:1000 for analysis by HPLC. A 1,2-PP solution was prepared as
previously mentioned for blank analysis on the HPLC. Also, a
solution of the 1,2-PP with MI, HDI, MDI, and TDI was prepared to
determine the retention time of each derivative. The results were
excellent, demonstrating that a mixture of the four isocyanates
could be analyzed with good chromatographic separation and
quantitation.
Isocyanate Generator
An isocyanate atmosphere generator was constructed to provide
a source of isocyanates as a simulated source, for testing within
the laboratory. It is expected that this generator will be
applicable to all four of the isocyanates listed in the CAAA, but
for the reasons explained earlier the generator was tested only for
TDI.
A modified Method 5 sampling train (without the in-line
filter) was set up in the laboratory. Attached to the end of the
probe was a piece of heated 0.5 inch quartz tubing with a stainless
3

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steel tee and septum (for introduction of the isocyanate(s)
standard). The temperature of the probe and quartz tubing were
maintained at 120° C. Five impingers were connected in series for
this study. The first impinger was a Greenberg-Smith impinger and
the four following impingers were modified Greenberg-Smith
impingers (straight stem- no tip). Room air was pulled through a
charcoal scrubber into the heated quartz tubing and subsequently
into two impingers containing the 1,2-PP absorbing solution.
Following the two impingers containing the absorbing solution were
one empty impinger (trap), a silica gel impinger, and an impinger
containing charcoal (scrubber). A TDI standard in methylene
chloride (MeCl2) , prepared as described earlier, was introduced by
a motor driven syringe pump, through the septum and into a heated
air stream. Room air was sampled at a rate of 0.5 ft3/min for 40
minutes. This flow rate was chosen to test collection efficiencies
at a flow rate expected to be used during the field testing.
Cleanup and analysis procedures were as previously described, using
toluene and ACN rinses and HPLC-UV analysis. Sample breakthrough,
as measured by the recovery in the second impinger, was less than
8 percent. Mean recoveries for seven sample runs were 77 percent
(see Table 2).
When the data in Table 2 was reevaluated, by eliminating the
obvious outliers (Grubbs t-test for multiple outliers)5, the mean
recovery is 98 +/- 15%. An obvious cause for the two outliers was
not determined, since all operating parameters were standardized
for the seven sample runs. As stated by Snedecor and Cochran in
their chapter on regression analysis and outliers6, " when no
explanation is found [for the outliers] the situation is
perplexing. It is usually best to examine the conclusions obtained
with the suspect (i) included, (ii) excluded. If these conclusions
differ materially, as they sometimes do, it is well to note that
either may be correct." Even though the Grubbs test for multiple
outliers indicates that both of the outliers are suspect it is
important to note that should one choose to include the suspect
outliers, the recovery data would still be acceptable according to
EPA Method 301 criteria.7
Method Validation
A field test of the method was performed in February, 1993, at
a flexible foam manufacturer in the High Point, North Carolina
area. A modified Method 5 sampling train (with a water-cooled
condenser on the outlet of the first impinger) was used to collect
source gas from the plant's process vent (see Figure 1). The
sample gas stream was passed through a heated glass-lined/stainless
steel probe and through two impingers containing the 1,2-PP
absorbing solution, one empty impinger (carryover trap), one silica
gel impinger, and one impinger containing charcoal (to trap any
toluene vapors before they could enter the meter box). Sampling
was non-isokinetic at 0.5 ft3/min for 60 minutes. Non-isokinetic
sampling was performed since a presurvey indicated the analyte of
4

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interest was present in the gas phase. Two of the quad trains for
each sample run were spiked with a TDI derivatized standard (22.5
mg TDI/urea derivative in 15 mL of ACN). This standard spike was
the equivalent of 8 mg of underivatized TDI, which was the amount
indicated by the presurvey that we could expect to collect in sixty
minutes of sampling. Impingers and other glassware used in the
sampling train were rinsed first with toluene and then with ACN.
Probe rinse and associated glassware rinses were combined with the
contents of the first impinger for subsequent analysis by HPLC-UV.
Toluene/acetonitrile rinses from the condenser and second and third
impingers were also combined for HPLC analysis. Samples were kept
on ice at 0 to 4° C until returned to the laboratory.
Operating parameters for the HPLC were as follows:
Instrument: Rainin HPXL delivery system with Waters
710B WISP autosampler.
Data System: Nelson 2600 (1 volt)
Column: Zorbax ODS (4.6 mm ID x 25 cm)
Mobile Phase: ACN/0.1M ammonium acetate buffer
Gradient: 25:75 ACN/0.1M ammonium acetate buffer,
pH 6.2, hold 2 min, then to 60:40 ACN/0.1M
ammonium acetate buffer for 19.5 min.
Detector Wavelength: 254 nm
Flow Rate: 2 mL/min.
Results from the field test were excellent (see Table 3). The
mean recovery of the spikes was 91 +/- 6%. Breakthrough, as
measured by the recoveries in the second impingers, were all less
than 2 percent, indicating near complete recovery in the first
impinger. Background or emissions concentrations (as determined by
analysis of the unspiked trains) ranged from 2000 ug/M3 to 7700
ug/M . The method's Limit of Quantitation (LQ) for TDI, calculated
as outlined in EPA Method 3017, was determined to be 351 ng/M3. The
Lq of the method is defined as ten times the standard deviation of
the mean of the data set whereas the method Limit of Detection (LD)
would be calculated as 3.3 times the standard deviation of the mean
of the data set.
CONCLUSIONS
A method has been developed for the collection and analysis of
TDI. Method validation procedures are still underway, but
preliminary results from the first field test indicate that the
method can be applied with a great degree of confidence to source
emissions for TDI. Other isocyanate compounds (MI, MDI, HDI) have
been or are being studied, and it is hoped that this method can be
successfully applied to them as well. Current plans are for
another field test in the near future, at another flexible foam
manufacturer or other end user. Conditions not experienced in the
sampling of source emissions during the first field test (i.e.,
higher humidity, particulate loadings, and/or warmer stack gas
temperatures) will be investigated in the next field test.
5

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REFERENCES
1.	Clean Air Act Amendments of 1990, Public Law 101-549, U.S.
Congress, November 15, 1990, 104 STAT., pp. 2533-2535.
2.	Material Safety Data Sheet, No. 331, Geniura Publishing
Corporation, Schenectady, NY, Nov. 1978.
3.	IDLH Levels, National Institute for Occupational Safety and
Health (NIOSH), Publication No. 78-210, 5h Printing.
4.	Goldberg, P.A., R.F. Walker, P.A. Ellwood, and H.L. Hardy,
" Determination of Trace Atmospheric Isocyanate Concentrations
by Reversed-Phase High-Performance Liquid Chromatography Using
l-(2-pyridyl)piperazine Reagent", Journal of Chromatographyf
212, 1981, pp 93-104.
5.	Grubbs, F.E., "Sample Criteria for Testing Outlying
Observations", Annals of Mathematical Statistics. Vol. 21,
1950, pp. 27-58.
6.	Snedecor, G.W. and W.G. Cochran, Statistical Methods. Sixth
Edition, Iowa State University Press, 9 Printing, p. 158.
7.	"Field Validation of Emission Concentrations from Stationary
Sources," Method 301 Federal Register, U.S. Government
Printing Office, Washington, D.C., December 1992.
6

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DISCLAIMER
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administrative review
policies and approved for presentation and publication. Mention of
trade names or commercial products does not constitute endorsement
or recommendation for use.
7

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Table l. Isocyanate Project Objectives
No.
Objective Description
MI
MDI
HDI
TDI
1
Find one derivatizing
reagent to react rapidly
with all four isocyanates
yes1
yes
yes
yes
2
Set up analytical HPLC
method (for a single
chromatographic run)
yes
yes
yes
yes
3
Develop instrument and
method detection limits
no
yes
yes
yes
4
Determine spike recovery
from derivatizing reagent
no
no
no
yes
5
construct an isocyanate
generator
no
no
no
yes
6
Determine recoveries from
spiked Method 5 train
no
no
no
yes
7
Field test of method and
validation
no
no
no
yes
Yes indicates that objectives have been met. No indicates
that an attempt has not been made to meet the objectives.
Table 2. Recoveries of Isocyanate (TDI) Spikes
Run No.
Spike Amount
(ug)
Spike Recovery
(ug)
Recovery
(%)
1
2.5
3.05
122
2
2.5
0.60
24
3
2.5
2.30
92
4
2.5
0.65
26
5
2.5
2.13
85
6
2.5
2.53
101
7
2.5
2.23
89
Mean w/outliers


77 +/- 38
Mean wo/outliers


98 +/- 15
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Table 3. Field Test Spike Recoveries
Sample Train
Identification1
Spike Amount
(ug)
Spike Recovery
(ug)
Recovery
(%)
1A
7828
7436
95
IB
7828
6654
85
2C
7828
6732
86
2D
7828
7280
93
3A
7828
6810
87
3B
7828
7280
93
4C
7828
7436
95
4D
7828
7593
97
5A
7828
6888
88
5B
7828
7436
95
6C
7828
7515
96
6D
7828
7671
98
7A
7828
7826
100
7B
7828
6575
84
8C
7828
6732
86
8D
7828
6419
82
Mean


91 +/- 6
Sample trains A&B are paired trains, as are sample trains C&D.
9

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Slack
Wall
Heal Traced
Quartz Probe
Uner
Temperature Sensor
S-Type Pilot Tube
Manometer
Ico Bath
Abeortong Solution
Toluene/Pipe raane
Empty
Silica Gel
Charcoal
Orifice
Pump
Figure 1. Isocyanate Sampling Train Configuration
10

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TECHNICAL REPORT DATA
(rleate read Initructiont on the reverie before corr
1. REPORT NO.
EPA/600/A-93/124
4. TITLE AND SUBTITLE
6. REPORT DATE
Development and Validation of a Source Test Method for
2,4-Toluene Diisocyanate
. PERFORMING ORGANIZATION CODE
. AUTHORIS)
F. Wilsh^re and J. Knoll, EPA/AREAL/MRDD, RTP, NC 27711
and S. Foster and J. McGaughey, Radian Corp., RTP, NC
PERFORMING ORGANIZATION REPORT NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
U.S. Environmental Protection Agency
Atmospheric Research and Exposure Assessment Laboratory
MRDD/SMRB (MD-77A)
Research Triangle Park, NC 27711	
11. CONTRACT/GRANT NO
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
AREAL/MRDD/SMRB (MD-7 7A)
Research Triangle Park, NC 27711
13 TYPE OF REPORT AND PERIOD COVERED
14 SPONSORING AGENCY CODE
EPA/600/09-
is supplementary notes
16. abstract
Four isocyanates are listed for regulation in the Clean Air Act Amendments of
1990: hexamethylene-1,6 diisocyanate, methylene diphenyl diisocyanate, and 2,4-toluene
diisocyanate, each of which is used in the production of polymers, and methyl
isocyanate which is an intermediate in the manufacture of the insecticide carbaryl
(i-e., SevinR dust).
To support projected regulations, a study is under way to produce a source
sampling and analysis method for the four pollutants cited above. In the procedure
under development, the isocyanates are collected in an absorbing solution and
derivatized with l-(2-pyridyl)piperazine and analyzed by HPLC with UV detection. A
system was developed in the laboratory to generate isocyanate atmospheres for
optimization of sampling parameters and chromatographic conditions. The accuracy and
precision of the method is determined in the field using train spiking and multiprobe
sampling following the procedures outlined in EPA Method 301.
A field test of the isocyanate method, following EPA Method 301 procedures was
performed at a flexible foam manufacturer in the Greensboro-High Point, NC area.
Results were excellent, with analyte spike recoveries of 91% ± 6%. The method's limit
of quantitation (LOQ) was determined to be 351 ng of TDI/M3.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c COSATi Field,Croup
16 DISTRIBUTION STATEMENT
19 SECURITY CLASS (Thu Report/
20 SECURITY CLASS tTlmpafe)
21. NO. Of PAGES
11
22 PRICE
EPA F»fo> J220-1(R«».4-77) previous [Dition h oooliu

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