EPA/600/A-97/072
Analysis of Method TO-14 Target Analytes Using a Cryofocusing High-
Speed Gas Chromatograph Interfaced to a High-Speed Time-of-FIight
Mass Spectrometer
Richard E. Berkley
US EPA, Research Triangle Park, NC 27711
Benjamin D. Gardner and John F. Holland
Michigan State University, East Lansing, MI 48824
ABSTRACT
A high-speed gas chromatograph coupled with a high-speed time-of-flight mass
spectrometer was used to gain a six-fold increase in overall rate of analytical throughput for
analysis of EPA Method TO-14 target compounds. Duration of chromatograms was 180 •.
seconds. One hundred mass spectra per second, ranging from 35 to 270 mass units, were
collected. Single ion chromatograms were searched at appropriate retention times for
chromatographic peaks, which were integrated. Thirty-eight of the forty-one TO-14 target
compounds were calibrated using standards at five concentrations from 2.5 to 40 ppb. Four grab
samples of ambient air were collected at four different locations at an automobile repair facility,
and two grab samples were collected less than one minute apart at a site near a chemical plant,
just before and just after passage of three large diesel trucks. All samples were analyzed on the
same day they were collected. Most of the duplicate analyses were in close agreement. Ability
of the high-speed TOF/GC/MS system to perform analyses of TO-14 target compounds rapidly
and precisely was demonstrated.
This paper has been reviewed according to US Environmental Protection Agency 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.
INTRODUCTION
Nonpolar and semipolar organic vapors in ambient air can be effectively analyzed by EPA
Method TO-14 (1). Whole air samples are collected in Summa-polished ™ canisters which are
taken to a laboratory where the contents are analyzed by gas chromatography using a variety of
nonspecific and specific detectors, including mass spectrometry. Typical analyses take an hour
to run, which limits sample throughput to at most eight per day. Fast gas chromatography
(FGC), using narrow injection bandwidth (<100 millisecond) and high carrier flow velocity (100
- 200 cm/sec), can increase the speed of analysis, but specially designed detectors must be used
to distinguish such narrow peaks from electrical noise. Mass spectrometers and mass selective
detectors, unless operated in single ion mode or over a narrow scan range, scarcely respond
quickly enough to serve as detectors for even a conventional capillary GC. Typically they can
achieve a maximum of perhaps three full scans per second, which is not enough to characterize
the one second wide peaks at the front end of a conventional capillary chromatogram. The
advent of high-speed time-of-flight mass spectrometry (TOFMS) offers a way to overcome the
limitations of conventional GC detectors, and it opens the possibility of much faster GC
analyses. Holland and coworkers have designed a high speed TOFMS that can acquire and
record up to a thousand full mass spectra per second (2). Use of prototype high-speed TOFMS
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instruments has been demonstrated for a variety of analytical applications (3,4,5). The following
is an account of the use of this method to analyze volatile organic compounds in whole air
samples by a procedure analogous to EPA Method TO-14.
EXPERIMENTAL
Calibration standards were prepared by dynamic mixing of humidified zero air with a
commercial mixture containing 10 ppm (nominal) in nitrogen of each compound on the TO-14
target list A metal bellows pump was used to divert part of the diluted stream from a flow
manifold into a Summa-polished™ canister in which it was stored. Pressure of the standard
mixture in the canister was up to 30 psig. Pumping rate was controlled by a mass flow controller
set low enough to preclude backflow of room air into the manifold. Calibration standards were
analyzed by a procedure identical to that used for samples. Calibration standards at five different
concentrations 2.5,7.5,15,25, and 40 ppb (nominal), were used. The analytical system was .
calibrated for thirty-eight of the forty-one TO-14 target compounds. Accurate analysis of
benzene was forestalled by background contamination, and 1,2,4-trichlorobenzene and
hexachlorobutadiene were not quantitatively eluted because the transfer line heater was not
properly regulated.
Samples were collected by opening cleaned and evacuated canisters in places where
significant concentrations of TO-14 target compounds were expected. The filled canisters were
returned to the laboratory where they were pressurized with ultrazero air to approximately 30
psig. Allowance was made for dilution of the sample by pressurization.
Samples were analyzed by connecting the canister to the Chromatofast Cryofocusing unit
and opening the valve to permit sample to flow past the inlet through a tee fitting. A flow from
the canister of about 30 ml/min was maintained for three minutes while sample was drawn into
the Chromatofast unit at a rate of one ml/min. Control of the injection unit and starting data
acquisition by the mass spectrometer were controlled by the microprocessor in the
chromatograph.
A Varian 3400 Star Fast GC™ equipped with a Chromatofast Cryointegrator™ injection
system was connected directly to a prototype Leco FCD-1000™ time-of-flight mass
spectrometer. The temperature of the methylsilicone-coated column was programmed from 60 to
180°C at a nominal rate of 357minute (32°/minute actual). Initial hold time was 0.2 min, and
duration of chromatograms was 180 seconds. One hundred mass spectra per second, ranging
from 35 to 270 mass units, were collected. The single ion chromatograms corresponding to the
base peaks of TO-14 target list compounds were searched for chromatographic peaks at
appropriate retention times. Peaks were integrated on-screen by hand, and peak areas and
heights were imported into a Lotus spreadsheet for tabulation and graphical representation. The
baseline of each ion chromatogram used in quantitation was sampled over a range of several
seconds in a region apparently free of peaks, and the minimum detectable peak height was taken
to be three times the standard deviation of the baseline for that chromatogram. Lesser peaks
were treated as "below detection limit". Detection limits ranged from 0.13 ppb for Freon 12 to
38.1 ppb for benzyl chloride. Most detection limits were below 5 ppb. Much higher detection
limits resulted when there was excessive scatter on the calibration plot. The average of all
detection limits was 4.3 ppb. By contrast, Method TO-14, using samples 100 times larger has
detection limits of about 0.2 ppb.
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RESULTS AND DISCUSSION
Four grab samples of ambient air were collected at different locations in an automobile
repair facility. Two samples were also collected less than one minute apart at a site near a
chemical plant just before and just after passage of three large diesel trucks. All samples were
analyzed the same day they were collected. Figure 1 shows data from a sample collected in the
parking lot of the auto repair shop. Four compounds were detected, all at low concentrations. In
the service writer's office (Figure 2) and in the shop behind the office (Figure 3) concentrations
were substantially higher. Duplicate analyses were run on these samples and good agreement
was observed. Concentrations inside the paint locker of the body repair shop where the stench
was virtually intolerable were highest of all, even with the exhaust fan in operation (Figure 4).
A sample was taken at the gate of a chemical plant and analyzed in duplicate, again
showing close agreement (Figure 5). Immediately after the fifth sample was taken, three large
diesel trucks passed the gate, whereupon a sixth sample (the second at the site) was collected i
within less than a minute. Concentrations of all compounds found in the first sample at that site
were larger in the second sample (Figure 6), which suggests that they probably originated from
heavy truck traffic in the area rather than from the chemical plant.
CONCLUSIONS
Ability of the high-speed TOF/GC/MS system to perform analyses of TO-14 target
compounds rapidly and precisely was demonstrated. Duplicate analyses were generally in close
agreement. Sensitivity was about 20 times less than for Method TO-14 using samples 100 times
smaller. Since column capacity decreases with increasing flow velocity, it is not possible to
increase sample size to that used in Method TO-14. On the other hand, narrow injection
bandwidth enhances sensitivity because peaks are taller. The optimum sensitivity of
FGC/TOFMS analysis has not yet been realized. Slightly larger sample size with improved
technique may result in sensitivity nearly equivalent to Method TO-14. In any case, a useful
method for rapid screening and preliminary evaluation of TO-14 samples has been demonstrated.
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REFERENCES
1. Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air.
Environmental Protection Agency, Atmospheric Research and Exposure Assessment Laboratory,
Research Triangle Park, NC 27711. EPA-600/4-84-017. June 1988.
2. Ben D. Gardner, John F. Holland. "High Speed. High Throughput GCMS Using Time-of-
Flight Mass Spectrometry with Time Array Detection." Proc. 44th ASMS Conf. on Mass
Spectrometry and Allied Topics, Portland, OR May 12-16,1996, Page 1119.
3. Ben D. Gardner, Richard E. Berkley, John F. Holland. "Rapid Analysis of TO-14 Airborne
Contaminants by Fast GC-TOFMS." Proc. 44th ASMS Conf. on Mass Spectrometry and Allied
Topics, Portland, OR May 12-16,1996, Page 513.
4. Jun Song, Ben D. Gardner, John F. Holland, Randolph M. Beaudry. "Rapid Analysis of
Volatile Flavor Compounds in Horticultural Produce Using SPME and GC/Time-of-Flight Mass
Spectrometry." Proc. 44th ASMS Conf. on Mass Spectrometry and Allied Topics, Portland, OR
May 12-16,1996, Page 547.
5. James Grainger, Vaughn Green, John Barr, Cheryl McClure, Zaiyou Liu, Donald G. Patterson,
Jr., John F. Holland, Ben D. Gardner. "Fast Gas Chromatography/High Resolution Mass
Spectrometry and Fast Gas Chromatography/Time-of-Flight Mass Spectrometry Analysis of
PCBs, PAAHs, CDDs and Threat Assessment Standards." Proc. 44th ASMS Conf. on Mass
Spectrometry and Allied Topics, Portland, OR May 12-16,1996, Page 860.
CAPTIONS FOR FIGURES
Figure 1. Analysis of a sample collected in the parking lot of an automobile repair shop.
Figure 2. Duplicate analyses of a sample collected in the office of an automobile repair shop.
Figure 3. Duplicate analyses of a sample collected inside an automobile repair shop.
Figure 4. Analysis of a sample collected inside the paint locker of an automobile body shop.
Figure 5. Duplicate analyses of a sample collected at the gate of a chemical plant.
Figure 6. Samples collected at the gate of a chemical plant just before and just after passage of
three diesel trucks.
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Sample 5 At Gate of Chemical Plant
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Samples 5 & 6 Before and After Trucks
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TECHNICAL REPORT DATA
1. REPORT NO. 2.
EPA/600/A-97/072
3- IIIIIUIIHIIIMIIIII
PB98-116262
4. TITLE AND SUBTITLE
Analysis of Method TO-14 Target Analytes Using a
Cryofocusing High-Speed Gas Chromatograph Interfaced
to a High-Speed Time-of-Flight Mass Spectrometer
5.REPORT DATE
6.PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Richard E, Berkley, U.S. EPA, Research Triangle Park, NC
Benjamin D. Gardner and John F. Holland, Michigan State University,
East Lansing, MI 48824
8.PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Michigan State University
East Lansing, MI 48824
10.PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
National Exposure Research Laboratory
Research Triangle Park, NC 27711
13.TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A high-speed gas chromatograph coupled with a high-speed time-of-flight mass spectrometer was used to gain a six-
fold increase in overall rate of analytical throughput for analysis of EPA Method TO-14 target compounds. Duration of
chromatograms was 180 seconds. One hundred mass spectra per second, ranging from 35 to 270 mass units, were
collected. Single ion chromatograms were searched at appropriate retention times for chromatographic peaks, which
were integrated. Thirty-eight of the forty-one TO-14 target compounds were calibrated using standards at five
concentrations from 2.5 to 40 ppb. Four grab samples of ambient air were collected at four different locations at an
automobile repair facility, and two grab samples were collected less than one minute apart at a site near a chemical plant,
just before and just after passage of three large diesel trucks. All samples were analyzed on the same day they were
collected. Most of the duplicate analyses were in close agreement. Ability of the high-speed TOF/GC/MS system to
perform analyses of TO-14 target compounds rapidly and precisely was demonstrated.
This paper has been reviewed according to US Environmental Protection Agency 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.
17. KEY WORDS AND DOCUMENT ANALYSIS
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b.IDENTIFIERS/ OPEN ENDED
TERMS
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RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
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