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
     • U.S. GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7783
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Environmental Protection               Information
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