Real-Time Air Monitoring of Trichloroethylene and Tetrachloroethylene Using Mobile TAGA Mass Spectrometry

doi:10.4236/jep.2013.48A1012

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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)

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.

Email: *[email protected]

Received May 18th, 2013; revised June 27th, 2013; accepted July 30th, 2013

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”

100

1030507090110 130 150 170

Atomic Ma s s Unit (m/z)

Relative Ion Intensities (%)

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

100

406384104 124

130

Forward F i t = 9 5. 2%

Reverse Fit=99.3%

100

406384104 124

132

95 97

237

Forward F i t=94. 9%

Reverse F i t=98. 4%

CAD spec t rum of TCE

CA D spectrum of TCE

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

100

406384104124

Relative Ion Intensity (100%)

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

25000

50000

75000

100000

125000

050010001500 20002500 3000

Concentration (g/m

)

Intensity (cps

)

P/D 130/95

slope=48

=0.998

P/D 132/97

slope=34

= 0.996

P/D 132/95

slope=18

= 0.997

Figure 4. TAGA calibration plots of TCE using three P/D ion pairs: 130/95, 132/97 and 132/95.

100

200

0510 15 20

Time (minutes)

Concentration (g/m

)

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

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

200

400

600

010203

Concentration (g/m

)

Half-hour average

concentration

100 g/m

Minimum

odour threshold

440 g/m

Highest

instantanous level

580 g/m

OMOE

2002 interim standard

3500 g/m

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.

500

1000

1500

Concentration (g/m

)

OMOE 2002

interim standard

3500 g/m

Highest

half-hour conc.

1300 g/m

Survey

ave rage

150 g/m

t11 Se

t12 Se

25 Se

t10 Se

t17 Se

t18 Se

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

100

507090110 130150 170

Atomic Mass Unit

(

m/z

)

Relative Ion Intensities (%)

Trichloroethylene

Tetrachloroeth

Xylenes

Toluene

Propanol

Methylene chloride

Trimethyl Benzene

lene

Figure 8. Single MS spectrum obtained by the TAGA

downwind of a hazardous waste disposal facility in South-

ern Ontario in June 2011.

100

150

200

0713 20

Concentration (g/m

)

upwind siteout of plume

in plume

wind directiondownwind site

hazard ous

disposal

facility

oil

refinery

water

treatment

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

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

)

Time (minutes)

650

1300

0 102030

Concentration (



g/m

)

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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