United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S4-84-073 Aug. 1984
EPA Project Summary
Development of a Portable
Monitor for Detection of
Toxic Organic Compounds
T. Hadeishi, R. Mclaughlin, J. Millaud, and M. Pollard
The objectives of this study were: (a)
to design, construct, and deliverto EPA
a prototype portable tunable atomic line
molecular spectrometer (TALMS) ben-
, zene monitor, and (b) to locate matches
of atomic lines and sharp molecular
absorption features in other toxic or-
ganic compounds. TALMS is a newly
developed, high resolution molecular
absorption technique that is used in the
ultraviolet-visible region of the optical
spectrum to detect molecules in the gas
phase. The dual beam prototype instru-
ment was designed, constructed, tested
and delivered to the Environmental
Monitoring Systems Laboratory, Re-
search Triangle Park, North Carolina, in .
December, 1983. It was designed for
monitoring benzene with the Hg 253.7
nm line using the TALMS technique.
The instrument consisted of three units:
the optical unit (weight: 52 Ibs, dimen-
sions: 28 x 9 x 9"); the electronics unit
(weight: 16 Ibs, dimensions: 19 x 12.5
x 5.25"); and a power supply (weight:
14 Ibs, dimensions: 12 x 8 x 8"). The
total weight was 82 Ibs. Tests of the
performance of the benzene monitor
showed linear response from the detec-
tion limit of approximately 40 ppm-v to
3000 ppm-v. Limited laboratory tests
of a cryogenic concentration system for
the unit were carried out.
Lamps for the volatile elements (As,
Pb, Zn) that can be used with the TALMS
technique are now available commerci-
ally from Heraeus, Hanau, West
Germany. The magneticajly contained
lamps used with the TALMS technique
were improved so that they are more
stable, intense and have longer service
lives.
Searches for locations of potential
TALMS signals in o-, m-, p-xylenes,
bromobenzene, benzene, and aniline
were carried out using high and medium
resolution absorption spectra as guides.
TALMS signals were found f or p-xylene
with Si, Co, and Sb lines at 252.9 nm.
No signals were found at this wave-
length for o- or m-xylenes. TALMS
signals were also found for bromoben-
zene at 270.2 nm (Pt) and 266.5 nm
(Fe) and for aniline at 293.8 nm (Bi).
It is recommended that further
searches for potential TALMS signals
be carried out to extend the potential of
the technique to other organic com-
pounds and to decrease the detection
limit for benzene. The investigation of a
new related technique. Atomic Line
Molecular Spectroscopy (ALMS) is rec-
ommended. It does not use the Zeeman
effect, requires lighter equipment, and
should have much lower detection
limits. However, its selectivity would
not be as great as that for TALMS.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Research Triangle
Park. NC. to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
An analytical technique calledTunable
Atomic Line Molecular Spectroscopy
(TALMS) has been recently developed at
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Lawrence Berkeley Laboratory. TALMS is
essentially a high resolution, differential
absorption spectroscopic technique. It is
performed by splitting a source atomic
emission spectral line into components
with a magnetic field (Zeeman effect). A
differential measurement is made be-
tween the absorption of a Zeeman com-
ponent (or components) magnetically
tuned to match a sharp analyte absorp-
tion feature and an unmatched Zeeman
reference component(s). The sharp fea-
tures in the absorption spectra of the
organic compounds are due to rotational-
vibrational fine structure in the electronic
transitions. The difference in polarization
between the split Zeeman components
permits the matching and nonmatching
wavelengths to be alternately selected
and the absorption measured very rapidly
with an electro-optical device called a
Current Controlled Retardation Plate. The
differential absorption is proportional to
the amount of molecular species whose
absorption line is matched by Zeeman
component(s) of the source lamp. There-
fore, calibration curves can be established
following Beer's law.
TALMS is a high resolution (high selec-
tivity) absorption spectroscopic technique.
The high resolution is due to the narrow
width of the atomic probe line, ca. 0.1
cm"1, the location of which can be shifted
by changing the magnetic field strength.
The number of compounds that can be
detected with TALMS is limited only by
the presence of narrow, pseudo line
structure in the absorption spectrum of
the compound in the gas phase and the
matching of an appropriate atomic emis-
sion line to this feature.
TALMS has a number of advantages as
an analytical technique. It is a direct
analysis ^technique requiring very little
sample handling or preparation. Another
feature of TALMS is its essential freedom
from background interference. Since the
difference in wavelength between the
Zeeman components of the source emis-
sion line is typically 0.04 nm, any particle
scattering or semi-continuous absorption
will affect both components equally.
Therefore, the differential absorption
measurement will remove this interfer-
ence from the total signal. The high
resolution attainable with TALMS should
result in high selectivity and unambig-
uous qualitative identification of com-
pounds.
As a result of previous Interagency
Agreements EPA-80-D-X1014 and AD-
89-F-2A008 with Lawrence Berkeley
Laboratory, TALMS instruments Were
designed, constructed, and delivered to
the Environmental Monitoring Systems
Laboratory at Research Triangle Park,
North Carolina. Two prototype instru-
ments were delivered—a large laboratory
instrument and a benzene monitor.
The goals of the present study were to:
(a) design, construct, and deliver to the
Environmental Monitoring Systems Lab-
oratory, Research Triangle Park, North
Carolina, a portable TALMS benzene
monitor, and (b) to determine the spectral
location of potential TALMS features in
toxic organic compounds other than
benzene. A portable TALMS instrument
would be useful in field detection and
monitoring for benzene and other toxic
compounds. Determination of spectral
locations of potential TALMS signals is
necessary to optimize instrument per-
formance and to extend the technique to
other organic compounds.
The instrument design, construction,
and testing are described in the report.
The procedures and results of TALMS
molecularabsorption—atomic line match-
es and developments in lamp design and
construction are also given. Appendices
of the report include operating instruc-
tions for the TALMS portable monitor and
detailed descriptions of the optical, me-
chanical, and electronic components.
Conclusions and
Recommendations
Design and construction of a prototype
transportable TALMS instrument for ben-
zene detection was completed on sched-
ule and delivered to the Environmental
Monitoring Systems Laboratory at Re-
search Triangle Park, North Carolina in
December, 1983. It consisted of three
modules: a sensing module, an electron-
ics module and a power supply. The
sensing module weighed 52 Ibs (24 kg)
and the electronics module and power
supply weighed 16 Ibs (7.3 kg) each. The
electronics module is connected to the
other units by an extension cord for
convenient field use. The electronics
module was designed to be powered by a
100-watt motor generator in the field.
Instrument performance tests show that
the instrument has a linear response over
the range from the detection limit of 40
ppm-v up to 3000 ppm-v. This detection
limit is too high for direct ambient air
detection of benzene and some form of
concentration technique will be required.
A new commercially available source
(W. C. Heraeus GmbH, PEW, Hanau,
West Germany) is available that allows
As, Pb, and Zn lines to be used in this
instrument in addition to the Hg lines for
which it was designed. However, different
interference filters or a monochromator
would be required if these lamps were
used. While this instrument was under
construction, major advances were made
in the assembly and operation of the
magnetically confined atomic discharge
lamps leading to more stable and intense
emission.
Searches for TALMS signals in organic
molecules were found to be slow and
tedious due to lack of high resolution
absorption spectra in the literature for
most compounds. After considerable ex-
perimentation with a variety of lamps and
medium resoltuion absorption spectra,
TALMS signals were found for p-xylene
(Si: 252.85 nm; Co: 252.9 nm; Sb: 252.85
nm; Pt: 273.4 nm; Pt: 248.7 nm); for
bromobenzene (Pt: 270.2 nm; Fe: 266.5
nm); aniline (Bi: 293.8 nm); and for
benzene (Si: 252.85 nm; Sb: 252.85 nm).
No signals were found for o- or m-xylene.
TALMS signals have now been found for
benzene, bromobenzene, chlorobenzene,
toluene, p-xylene, aniline, phenol, pyri-
dine, and formaldehyde.
Since major decreases in detection
limits are dependent upon the location of
more intense analysis lines, it is recom-
mended that more studies be carried out
to locate new analysis lines for com-
pounds of interest.
It is also recommended that the investi-
gation of a new, related analytical tech-
niquecalled Atomic Line Molecular Spec-
troscopy (ALMS) be initiated. This tech-
nique involves absorption near the in-
tense absorption bands of the vacuum
ultraviolet region (180 to 220 nm) using
one or more atomic lines. The advantages
over the TALMS technique are much
lower detection limits and a lighter instru-
ment since only a small magnet and no
squeezer are required. Selectivity will be
decreased, but it may be adequate if
absorption by several atomic lines is
utilized.
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T. Hadeishi, R. Mclaughlin, J. Mi/laud, andM. Pollard are with Lawrence Berkeley
Laboratory. University of California. Berkeley, CA 94720.
D. R. Scott is the EPA Project Officer (see below).
The complete report, entitled"Development of a Portable Monitor for Detection of
Toxic Organic Compounds. "(Order No. PB 84-229 673; Cost: $ 10.00, 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:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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