Journal of Environmental Protection, 2013, 4, 99-105
http://dx.doi.org/10.4236/jep.2013.48A1012 Published Online August 2013 (http://www.scirp.org/journal/jep)
99
Real-Time Air Monitoring of Trichloroethylene and
Tetrachloroethylene Using Mobile TAGA Mass
Spectrometry
Nicholas S. Karellas*, Qingfeng Chen
Air Quality Monitoring Unit, Air Monitoring and Transboundary Air Sciences Section, Environmental Monitoring and Reporting
Branch, Ontario Ministry of the Environment, Toronto, Canada.
Received May 18th, 2013; revised June 27th, 2013; accepted July 30th, 2013
Copyright © 2013 Nicholas S. Karellas, Qingfeng Chen. This is an open access article distributed under the Creative Commons At-
tribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is prop-
erly cited.
ABSTRACT
Trichloroethylene (TCE) is a chlorinated liquid that is commonly used for metal degreasing, household and industrial
dry cleaning, and in paints and glues. Tetrachloroethylene, also known as perchloroethylene (PCE), is an excellent sol-
vent for organic materials. PCE is volatile, highly stable, non-flammable and widely used in dry cleaning. A new
method has been developed for measuring TCE and PCE in ambient air in real-time. Based upon the chemical finger-
printing and concentration levels, the method was able to isolate the source of the emissions to the responsible facility.
Real-time monitoring was accomplished by utilizing a low pressure chemical ionization source (LPCI) interfaced to a
tandem mass spectrometer (TAGA). Monitoring the response of specific parent/daughter ion pairs, the TAGA was used
to measure concentrations of TCE and PCE. By optimizing various TAGA parameters, detection limits (DL) as low as
0.5 μg/m3 was achieved for TCE and PCE. Unlike methods using cartridge sampling and GC/MS analysis, this new
method provides a real time measurement for a wide range of TCE and PCE concentrations. This unique method was
applied in 2000 and 2002 to measure TCE emitted from a manufacturer of stainless steel tubing in Eastern Ontario. The
maximum half-hour average concentration of TCE measured downwind of the facility was 1300 μg/m3 and the maxi-
mum instantaneous level was measured at 115,000 μg/m3. The information collected by the TAGA unit was used by the
Standard Development Branch of Ontario Ministry of the Environment to adopt the half-hour Point of Impingement
(POI) standard of TCE to be 36 μg/m3 in 2010. This method successfully identified and simultaneously measured TCE
and PCE during a 2011 air monitoring survey of a hazardous waste disposal and treatment facility in Southern Ontario.
Keywords: Environmental; Real-Time Monitoring; Mobile TAGA; TCE and PCE; Ambient Air
1. Introduction
Trichloroethylene (TCE) is a chlorinated liquid that is
commonly used for the extraction of solvents in many
industrial processes and in the manufacturing of phar-
maceuticals. Its use as a solvent in metal degreasing ac-
counts for over 90% of the TCE use in Canada. As a re-
sult, metal degreasing is the main source of TCE’s re-
lease to the atmosphere [1]. TCE is a colourless and non-
flammable chemical with a sweetish and chloroform-like
odour [2], with an odour detection limit reported at 440
μg/m3 [3]. It is a central nervous system depressant and
has been used as an anaesthetic. Occupational exposure
to TCE has resulted in nausea, headache, loss of appetite,
weakness, dizziness, and tremors. Acute exposures to
high concentrations have caused irreversible nerve dam-
age and death. Long term exposures to TCE have re-
sulted in liver and kidney damage [4]. TCE is classified
as a possible human carcinogen by the International
Agency for Research on Cancer (IARC) [5]. In 1982, the
Ontario Ministry of the Environment (OMOE) set a half-
hour Point of Impingement (POI) standard in Regulation
346 for TCE of 85,000 μg/m3. In 1999, the OMOE set a
POI interim standard for TCE to 3500 μg/m3 [1]. On
February 1, 2010, the OMOE adopted a new POI stan-
dard of 36 μg/m3 for TCE based on health impacts [6].
Tetrachloroethylene, also known as perchloroethylene
(PCE), is an excellent solvent. It is volatile, highly stable
and non-flammable. It is widely used in dry cleaning,
*Corresponding author.

Real-Time Air Monitoring of Trichloroethylene and Tetrachloroethylene Using Mobile TAGA Mass Spectrometry
100
usually as a mixture with other chlorinated hydrocarbons
[7]. It is also used to degrease metal parts in the
automobile and other metalworking industries. It has a
sweet odour detectable at 8300 μg/m3 [8]. PCE is a cen-
tral nervous system depressant and can enter the body
through respiration [9]. On February 1, 2010, the OMOE
adopted a POI half-hour standard of 1080 μg/m3 for PCE
[6].
In this paper, we describe how a mobile Trace At-
mospheric Gas Analyzer (TAGA) has been used to
monitor the TCE and PCE at a steel manufacture facility
and a hazardous waste disposal and treatment company.
The steel manufacture facility is located in Eastern On-
tario. It manufactures stainless steel tubing primary for
the oil and gas industries. It uses TCE to remove lubri-
cants and greases from metal tubes. The company typi-
cally operates 24 hours per day, 7 days per week. Ac-
cording to the Environment Canada National Pollutant
Release Inventory (NPRI) [10], this company was one of
the largest TCE emission sources in Ontario when the
TAGA conducted the air quality surveys in the vicinity
of this company in 2000 and 2002. The hazardous waste
disposal and treatment company is located in Southern
Ontario. It collects, recycles and disposes dry cleaning
waste solvents. This company was surveyed in 2011.
2. Experimental
2.1. The Mobile TAGA
The TAGA is a triple quadrupole mass spectrometer
(MS). It is a real-time, direct-air sampling analytical in-
strument [11] mounted in a 10-meter Orion coach as
shown in Figure 1. The coach accommodates two com-
puters for automated control of the TAGA including data
acquisition and analysis. A third computer records mete-
orological data such as ambient air temperature, wind
direction and wind speed every minute.
The mobile TAGA technology is an excellent tool that
has been used extensively by the OMOE from early
1980s to present for continuous monitoring of hazardous
volatile organic compounds (VOCs) in ambient air in
several situations such as remedial clean-up [12], emis-
sion abatement [13] and chemical spills and fires [14].
Ambient airborne levels of up to one thousand unknown
chemicals can be identified and quantified using this type
of technology.
“TAGA survey” means that this self-contained mobile
laboratory conducts an investigation, evaluating POI lev-
els of air pollutants around a particular facility. Upon
arrival at a survey site, the TAGA is used to determine
background levels and calibration for target chemicals (if
they are known) upwind of the emission source. Then
“plume tracking” is conducted by driving the mobile unit
downwind of the source while monitoring for selected
Meteorological Tower
Sampling
air inlet
Engine Generator
A/C units
Wind direction
Wind speed
Temperature
Figure 1. External view of the mobile TAGA unit.
target compounds to determine the location of the maxi-
mum instantaneous levels (POI of pollutants at the
ground level). Monitoring includes “chemically finger-
printing” the air to identify as many chemicals as possi-
ble and determine the airborne levels.
The mobile TAGA scientific team uses computers to
control and continually retrieve, evaluate and store col-
lected data, enabling specific reports to be produced at
the end of the monitoring period. Monitoring results can
then be transferred to OMOE offices in a matter of min-
utes with an on-board digital communication package. A
routine field survey lasts about two weeks. The mobile
lab can be sent to carry out surveys around industries in
the province, such as pulp and paper mills, painting op-
erations, oil refineries, and petrochemical plants. Data is
then turned over to the OMOE’s regional offices for fol-
low-up action. TAGA data have been used in abatement
programs, air standards development, judicial proceed-
ings and health-risk assessments.
Over 350 TAGA surveys have been conducted since
1982 in more than 50 towns and cities across Ontario
from Windsor east to Cornwall and from Toronto north
to Fort Francis. The mobile TAGA has been incorporated
into the OMOE’s emergency response program. Its
unique ability to provide on-site data of chemicals in the
air has proven to be very useful in over 50 emergency
responses. Some of the major emergencies include Sarnia
benzene spill in 2008, Hamilton Plastimet fire in 1997,
Hagersville tire fire in 1990, PCB fire in St.Basile-le-
Grand in Quebec in 1988 and Mississauga train derail-
ment in 1979. In emergencies, TAGA quickly provides
important information in order to protect public health.
In 2001, the TAGA units of the United States Envi-
ronmental Protection Agency (US EPA) have responded
to the World Trade Center disaster, took air samples
throughout the ground zero area and analyzed for VOCs
[15]. In 2005, US EPA also mobilized TAGA to collect
air screening samples across the New Orleans area during

Real-Time Air Monitoring of Trichloroethylene and Tetrachloroethylene Using Mobile TAGA Mass Spectrometry 101
the Hurricane Katrina response [16]. In 2010, US EPA
TAGA units monitored the BP oil spill in the Gulf of
Mexico along the Gulf Coast [17].
2.2. Real-Time On-Site Air Monitoring
Traditional analytical methods for measuring VOCs in
ambient air involve the collection of samples with ad-
sorbent cartridges or canisters, which are then trans-
ported to a laboratory and analyzed at a later time using
the gas chromatograph (GC), or the combination of MS
in single mode (GC/MS), or in tandem mode (GC/MS/
MS) [18]. While these methods are particularly useful for
low levels (μg/m3) [13], they are quite time consuming
due to sample transportation, VOCs thermal desorption,
GC column separation and analyte detection. The con-
centrations obtained using these methods are time aver-
aged response and no instantaneous levels are provided
during sampling. In addition, these off-site analysis tech-
niques are usually not useful during emergency situations
(e.g., at the site of chemical fire, chemical spill, and
chemical train derailment) when minute by minute deci-
sions are critical especially fast assessment to determine
the evacuation zones or whether affected areas are safe
for residents. TAGA provides unique approach to per-
form real-time on-site continuous monitoring of airborne
VOCs, allowing rapid and reliable evaluation during
emergency situations as well as routine field surveys.
A low pressure chemical ionization source (LPCI)
source has been developed for the TAGA to measure
ambient chlorinated hydrocarbons in real-time yielding
reliable quantitative results with a low detection limit yet
a wide range (i.e. 0 - 3000 μg/m3). The LPCI source,
normally operated at a pressure of 3.5 Torr and 55 μA, is
based on a glow discharge in the ionization region using
ambient air as the support gas [12,13]. It is interfaced to
the TAGA triple quadrupole (Q1, Q2, Q3) MS. Airborne
chemicals undergo charge transfer reactions with reagent
ions (typically NO+, 2 and 2
O) to yield parent ions
which are mass analyzed in the quadrupole Q1 region,
dissociated in the Q2 region and, the daughter ions are
identified in the Q3 region. The monitoring of parent/
daughter (P/D) ions is used to identify airborne chemi-
cals and determine their concentrations.
N 
2.3. Identification
The single MS spectrum obtained downwind of a steel
manufacturing company is shown in Figure 2. The major
parent ions observed downwind were at 130, 132, 134
and 136 atomic mass units (amu) corresponding to chlo-
rine 35Cl and 37Cl isotopes. The two most abundant Q1
parent ions at 130 and 132 amu were then subjected to
collision activated dissociation (CAD) with an inert gas,
nitrogen, to produce fragment ions called “daughter ions”
0
20
40
60
80
100
1030507090110 130 150 170
Atomic Ma s s Unit (m/z)
Relative Ion Intensities (%)
0
20
40
60
80
100
130 132 134 136
Relative Ion Intensities (100%)
amu (m/z)
C2H35Cl237Cl
C2H35Cl3
C2H35Cl37Cl2
C2H37Cl
Figure 2. TAGA single MS spectrum obtained downwind of
a steel manufacture company in Eastern Ontario.
in the second quadrupole region (Q2). By comparing the
parent/daughter (P/D) ion fragmentation pattern with the
TAGA library of known chemicals it is possible to posi-
tively identify such unknowns.
A standard CAD library containing close to one thou-
sand chemicals has been created using 20 eV of collision
ion energy and nitrogen as collision gas. The CAD frag-
mentation patterns of the “unknown” parent ions at 130
and 132 amu are shown in Fi gure 3.
The spectrum of the “unknown” is compared with the
standard CAD library spectra; agreement between the
“reverse” and “forward” library search results and their
closeness to unity indicates the degree of certainty for
compound identification. In this case, the best search
results matched with TCE.
2.4. Quantitation
The quantitation is accomplished by multiple reaction
monitoring (MRM) of selected P/D pairs. The 130/95,
132/95 and 132/97 ion pairs are used to monitor ambient
TCE levels. A gaseous standard is introduced at various
concentrations into the air flow pathway to generate cali-
bration curves daily five-point calibrations were devel-
oped by simultaneously recording the response of the
three P/D ion pairs. A TCE calibration using a certified
gas cylinder of 50 ppm TCE in N2 over the concentration
range of 0 - 3000 μg/m3 is shown in Fi gure 4.
Calibrations are performed in-situ upwind of the
known sources, where ambient air is used as the carrier
gas to automatically account for any matrix effects. The
slopes of the response curves are a measure of the sensi-
tivity of the LPCI-MS/MS method. A linear response for
TCE was observed up to 3000 μg/m3. During the 2000
and 2002 TAGA surveys, the calibration response factors
and detection limits of TCE were determined at least
twice daily at various upwind locations. The detection
limit (DL) is defined as three tmes the standard deviation i

Real-Time Air Monitoring of Trichloroethylene and Tetrachloroethylene Using Mobile TAGA Mass Spectrometry
102
0
20
40
60
80
100
406384104 124
130
95
C
2
H
35
Cl
3
Forward F i t = 9 5. 2%
Reverse Fit=99.3%
0
20
40
60
80
100
406384104 124
132
95 97
C
2
H
35
Cl
237
Cl
Forward F i t=94. 9%
Reverse F i t=98. 4%
CAD spec t rum of TCE
CA D spectrum of TCE
0
20
40
60
80
100
406384104 124
Relative Ion Intensity (100%)
CAD spect rum of parent i on 132 amu
obt ai ne d downwi nd of a ste el company
132
95 97
0
20
40
60
80
100
406384104124
Relative Ion Intensity (100%)
95
130
CAD spect rum of parent i o n 130 amu
obt ai ned downwi nd of a steel company
Figure 3. TAGA MS/MS library search of molecular ion at 130 and 132 amu.
Tr ichloroethylen e calibration
0
25000
50000
75000
100000
125000
050010001500 20002500 3000
Concentration (g/m
3
)
Intensity (cps
)
P/D 130/95
slope=48
r
2
=0.998
P/D 132/97
slope=34
r
2
= 0.996
P/D 132/95
slope=18
r
2
= 0.997
Figure 4. TAGA calibration plots of TCE using three P/D ion pairs: 130/95, 132/97 and 132/95.
0
100
200
0510 15 20
Time (minutes)
Concentration (g/m
3
)
upwind site
of the background signal (upwind of the site) divided by
the slope of the calibration curve. Variations of ± 20%
for the DL from day to day are normal due to TAGA
sensitivity of ambient temperature and relative humidity.
The average DL for TCE during 2000 and 2002 survey
period was 0.5 μg/m3.
3. Results and Discussion
This method was applied in August 2000 and September
2002 to measure TCE of a company that manufactures
stainless steel tubing in Eastern Ontario. TAGA used
“chemical fingerprinting” and successfully identified
TCE downwind of this facility. Background levels of
TCE measured upwind of this company were below 0.5
μg/m3. An example of plume tracking for TCE is shown
in Figure 5. With the wind from the northeast the mobile
downwind site
wind directio
n
upwind
steel
company
downwind
Figure 5. Real-time plume trucking for TCE from upwind
to downwind by the TAGA in the vicinity of a steel company
in Eastern Ontario, September 2002.

Real-Time Air Monitoring of Trichloroethylene and Tetrachloroethylene Using Mobile TAGA Mass Spectrometry 103
unit began tracking from an upwind site 100 meters
northeast of the company. As the mobile unit proceeded
eastward along the road south of the company TCE lev-
els rose to 100 - 150 μg/m3. The mobile unit then started
to sample the plume from the target company at this lo-
cation and took half-hour measurements for comparison
to the OMOE POI standard.
An example of a real time 30-minute measurement is
shown in Figure 6. Readings were recorded every five
seconds for thirty minutes at a fixed location to obtain a
half-hour average concentration.
Rapid changes in TCE levels were primarily due to
local air turbulence, as well as changes in the wind direc-
tion. During this monitoring period for TCE the half-hour
average concentration was 100 μg/m3, which was below
the 2002 OMOE POI interim standard of 3500 μg/m3 for
TCE. At one point during the half-hour sampling period,
instantaneous levels of TCE peaked to 580 μg/m3, higher
than the odour threshold of 440 μg/m3.
A summary of the half-hour average concentrations
measured by TAGA during 2000 and 2002, while down-
wind of the company is shown in Figure 7. A total of 88
half-hour average concentrations were obtained at seven
different downwind locations with the highest measure-
ment of TCE being 1300 μg/m3. This value was below
the half-hour OMOE POI interim standard of 3500 μg/m3
for TCE at that time. In 78 out of the 88 (89%) half-hour
samples for TCE, maximum instantaneous levels were
higher than the minimum odour threshold. The maximum
instantaneous level of TCE was measured at 115,000
μg/m3, 260 times higher than the minimum odour thresh-
old of 440 μg/m3.
Following the 2000 and 2002 TAGA surveys, OMOE
Standards Development Branch adopted a new standard
of TCE effective February 1 2010. The company gradu-
ally phased out TCE as the degreaser solvent. Current
NPRI data indicate that TCE annual emissions from this
facility dropped from 185 tones in 2002 to 0.029 tones in
0
200
400
600
010203
0
Concentration (g/m
3
)
Half-hour average
concentration
100 g/m
3
Minimum
odour threshold
440 g/m
3
Highest
instantanous level
580 g/m
3
OMOE
2002 interim standard
3500 g/m
3
Time (minutes)
Figure 6. A real-time measurement of TCE using the P/D
ion pair 130/95 obtained by the TAGA downwind of a steel
company in Eastern Ontario in September 2002.
0
500
1000
1500
Concentration (g/m
3
)
/
Au
OMOE 2002
interim standard
3500 g/m
3
Highest
half-hour conc.
1300 g/m
3
Survey
ave rage
150 g/m
3
t11 Se / t12 Se /
g
25 Se
/
p
t10 Se
/
p
p
p
t17 Se /
p
t18 Se /
p
t1 9 /
Figure 7. A survey summary of the TCE half-hour average
concentrations measured by the TAGA at several sites
downwind of a steel company in Eastern Ontario in August
2000 and September 2002.
2009.
The ability to identify specific airborne chemicals in a
complex matrix became evident when in June 2011,
TAGA detected PCE and TCE in a concentrated Indus-
trial area with multiple emission sources during a general
air quality assessment of a region in Southern Ontario. A
hazardous waste disposal and treatment company is situ-
ated within 500 meters of a water treatment plant and an
oil refinery. While downwind of this company the TAGA
identified seven airborne chemicals: propanol, methylene
chloride, toluene, xylenes, trimethyl benzene, TCE and
PCE, as shown in Figure 8.
The chemical fingerprints of TCE and PCE obtained
downwind of the hazardous waste disposal facility were
unique and permitted the mobile TAGA unit to isolate
the company’s air emissions. The presence of the TCE
and PCE downwind of this facility was also verified by a
portable Inficon Hapsite GC/MS instrument (Hapsite ER)
[19] on-board the mobile TAGA unit.
In order to track down and differentiate the suspected
source, TAGA modified the survey strategy by plume
tracking (driving upwind and downwind of the company)
at particular times so that the TAGA unit could be lo-
cated precisely downwind of the target company thus
avoiding any impact of emissions from other companies
nearby. TAGA was able to plan the route to eliminate
inference sources using the meteorological data on-board.
As shown in Figure 9, with the wind from the east, the
mobile unit began plume tracking for TCE and PCE from
an upwind site just east of the oil refinery plant.
As the mobile unit drove eastward and then northward,
the background levels of TCE and PCE indicated that
there was no TCE or PCE from either the oil refinery
facility or the water treatment plant. As the TAGA unit
briefly crossed the plume of the target company, the lev-
els of TCE and PCE spiked. As the unit continued going
north and going out of the plume, TCE and PCE dropped
to background levels. The TAGA turned around heading

Real-Time Air Monitoring of Trichloroethylene and Tetrachloroethylene Using Mobile TAGA Mass Spectrometry
104
0
20
40
60
80
100
507090110 130150 170
Atomic Mass Unit
(
m/z
)
Relative Ion Intensities (%)
Trichloroethylene
Tetrachloroeth
Xylenes
Toluene
Propanol
Methylene chloride
Trimethyl Benzene
y
lene
Figure 8. Single MS spectrum obtained by the TAGA
downwind of a hazardous waste disposal facility in South-
ern Ontario in June 2011.
0
50
100
150
200
0713 20
Concentration (g/m
3
)
upwind siteout of plume
in plume
wind directiondownwind site
hazard ous
disposal
facility
oil
refinery
water
treatment
p
lant
PCE
TCE
Time
(
minutes
)
TAGA route
Figure 9. Real-time plume tracking for PCE and TCE ob-
tained by the TAGA in the vicinity of a hazardous waste
disposal facility in Southern Ontario in June 2011.
south and was positioned downwind of the target com-
pany. PCE dramatically increased to nearly 200 μg/m3
and TCE to10 μg/m3. By driving through and out of the
plume twice, the TAGA verified the emission source and
eliminated any possibilities of memory affects of PCE
and TCE on sample inlets.
The mobile TAGA then started to sample the plume
from the target company at this location and took meas-
urements of PCE and TCE for comparison to the OMOE
POI standard, as shown in Figure 10.
During the 2011 survey, the highest half-hour concen-
tration of PCE and TCE measured by the TAGA were
300 μg/m3 and 23 μg/m3, respectively, both below the
OMOE POI standards. The 2011 survey data for PCE
and TCE was related to appropriate OMOE staff for air
quality impact assessments.
4. Conclusion
The mobile TAGA unit used a real-time LPCI-MS/MS
method to monitor TCE and PCE emitted from two fa-
cilities in Ontario. The results illustrated fast response
and negligible memory effects of pollutants on the TAGA
sampling system. This rugged and relatively maintenance-
free technique proved very useful to measure TCE and
PCE levels in the ambient air on-site. TAGA calibrations
0
50
100
0102030
Half-hour average concentration of Tri choloet hylene (TCE)
Highest level
98 g/m3
Half-hour conc.
19 g/m3
Minimum odour threshold
440 g/m3
OMOE standard
36 g/m3
Concentration (g/m
3
)
Time (minutes)
0
650
1300
0 102030
Concentration (

g/m
3
)
Half-hour average concentration of
Half-hour conc.
280 g/m3
Tetrachloroethylene (PCE)
OMOE standard
1080 g/m 3
Minimum odour threshold
8300 g/m3
Highest level
1300 g/m 3
Time (minutes)
Figure 10. Half-hour samples of PCE and TCE obtained by
the TAGA downwind of a hazardous waste disposal facility
in Southern Ontario in June 2011.
resulted in reliable and reproducible curves up to 3000
μg/m3 for TCE and 1500 μg/m3 for PCE. The data ob-
tained from the TAGA surveys using this method were
relayed to the other OMOE branches to help revise a new
POI standard of TCE.
5. Acknowledgements
The authors would like to express their appreciation to
the OMOE Air Monitoring staff: George Rioual, Natalie
Stacey, Clarissa Whitelaw, and Al Melanson, Zachary
Ramwa from the OMOE Geomatics Centre.
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