United States
                   Environmental Protection
                   Agency
 Environmental Monitoring Systems,
 Laboratory
 Research Triangle Park NC 27711
                   Research and Development
 EPA-600/S4-82-067  Jan. 1983
SEPA         Project  Summary

                   Development of a  Tunable
                   Zeeman  Spectrometer  for
                   Analysis  of  Toxic Organic
                   Compounds
                   T. Hadeishi, R. McLaughlin, and J. Millaud
                    This  program was undertaken to
                   investigate the application of a new
                   analytical technique called tunable
                   atomic line molecular spectroscopy
                   (TALMS) to the detection of a variety
                   of  volatile organic molecules of
                   concern to the Environmental Protec-
                   tion Agency. During the first phase of
                   the study a prototype instrument was
                   built and tested to demonstrate the
                   detection of both small (i.e., less than
                   four atoms) and complex molecules.
                   During the second phase a more
                   compact instrument was constructed
                   for delivery to EPA, Research Triangle
                   Park, NC before January, 1982. This
                   second instrument was optimized for
                   the detection of the more complex
                   organic molecules benzene and chloro-
                   benzene.

                    TALMS is a high resolution, molec-
                   ular differential absorption technique
                   used in the ultraviolet-visible spectral
                   region.  It utilizes the splitting of an
                   atomic  emission spectral line from a
                   lamp in a magnetic field (the Zeeman
                   effect).  One split line (Zeeman com-
                   ponent) is made to overlap a rotational
                   line associated with an electronic
                   transition of the analyte molecule by
                   proper  adjustment of the  magnetic
                   field. Other Zeeman components of
                   this same  atomic  line that do not
                   overlap the absorption feature are
                   used as reference lines. The concen-
tration of the molecule is then deter-
mined by differential intensity mea-
surements of these two Zeeman
components. TALMS was first devel-
oped to detect inorganic diatomic and
triatomic molecules which  exhibit
well defined rotational spectra in the
visible and ultraviolet spectral regions,
e.g.,  NO,  SO2,  NO2.  Rationale for
expected high specificity and  high
sensitivity with the TALMS instrument
for large complex, organic molecules
are discussed. Estimates of detection
limits, resolution, selectivity, and
linear range of the TALMS technique
are also given.
  TALMS data on nitric oxide and
formaldehyde are presented as a part
of this study. The TALMS spectrum of
formaldehyde near 3390 A is discussed
since this data is the highest resolution
data yet obtained on this compound
and illustrates the selectivity attain-
able with the technique. During the
second phase of this work, the line
shapes of the absorption features
responsible for the benzene  and
chlorobenzene TALMS signals  near
2537 A were obtained. Line shape
information can be used to optimize
the sensitivity of the instrument for a
given compound. Using this informa-
tion, it was possible to build a second
instrument  with a  magnetic field
strength that was optimum  for the
detection of benzene at 2537 A. Both

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benzene  and chlorobenzene give
TALMS signals with the same mercury
line at 2537 A. The line shape informa-
tion for the compounds allowed a field
strength  and configuration to be
chosen that effectively eliminated the
interference of chlorobenzene on  the
benzene TALMS signal.  Block dia-
grams, photographs of the prototype
instrument, and descriptions of its
components are included.
  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
documented in a separate report of the
same title (see Project Report ordering
information at back).

Introduction
  Increased utilization  of advanced
technologies has led  to the  need to
monitor a  large variety of toxic organic
and  inorganic  species. The identifica-
tion and  quantification of  almost all
organic compounds are presently ac-
complished using some type  of chro-
matographic technique,  e.g., GC, GC/MS,
HPLC, etc. These methods are time
consuming, frequently not very selective,
and, in the case of the GC-MS, require
expensive equipment. A highly selective
technique that depends  on  high
resolution spectrometric  principles
would be faster and reducethe likelihood
of incorrect qualitative analysis.  The
goal of this study, which was performed
at the Lawrence Berkeley Laboratory, is
to develop an instrument to be used for
highly  selective and sensitive  organic
analysis. This instrument should ideally
be compact, relatively  inexpensive, and
easy to operate.
  Those methods that depend only upon
the  interaction of radiation with  the
sample most closely approach the ideal
case. Contamination and loss problems
are greatly reduced when the sample is
only moved into a light beam.  The
technique whose development is de-
scribed in this report represents a step
in this direction for the determination of
both organic  and inorganic  species.
Although non-gaseous samples must be
volatilized to use this technique,  this
alteration is common  in other types of
organic analysis, e.g.,  GC,  GC-MS, LC-
MS.
  An analytical technique called Tunable
Atomic Line Molecular Spectroscopy
(TALMS) has recently been developed at
the Lawrence  Berkeley Laboratory. It is
capable of the detection and measure-
ment of a large number of both organic
and  inorganic  molecules with  high
sensitivity. The selectivity of TALMS is
such that  molecules can be identified
and quantified even in the presence of a
large amount and number of interfering
substances. The number  of compounds
that can be detected is almost unlimited,
depending only upon the presence of
narrow, line-like features in the ultra-
violet-visible absorption spectrum of the
compound in the gas  phase.  This
technique also requires minimal sample
handling.
  TALM spectroscopy consists of splitting
a source atomic emission spectral line
by means  of a magnetic  field (Zeeman
effect) and making a differential absorp-
tion measurement between one Zeeman
component that has been magnetically
tuned to match an analyte absorption
line and an unmatched Zeeman reference
component. The difference in polariza-
tion between the Zeeman components
permits the matching and nonmatching
wavelengths to be alternately selected
and the absorption measured  very
rapidly with an electrooptical  device
called a Current Controlled Retardation
plate (CCR).  The TALM  spectrometer
detects the  difference  in absorption
between the Zeeman components. The
differential absorption  is then propor-
tional to the amount of molecular species
whose  absorption line is matched  by
one of the components  of the  source
lamp.
  One remarkable feature of TALMS is
its essential  freedom from background
interference   Since  the  difference  in
wavelength between the  Zeeman com-
ponents of the source  emission line is
typically 0.04 nm, any particle scattering
or semi-continuous absorption will
affect both components equally. There-
fore, the differential absorption mea-
surement will remove this interference
from the total signal. Hence, this type of
interference, which is a problem in most
spectroscopic methods, does not affect
TALMS measurements.

Conclusions and
Recommendations
  Tests with the TALMS system on
diatomic,  triatomic, and tetratomic
molecules  indicate that these molecules
contain rotational features similar in
sharpness to that of atomic lines Larger
molecules, e.g., benzene at certain
wavelengths, also show  large changes
in absorption intensity within a small 60
GHz (2 cm ') spectral interval. TALMS
data, limited available  data from ultra-
high resolution absorption experiments,
and theoretical considerations make it
evident  that sharp line-like rotational
structure and/or very sharp changes in
the slope of absorption features are
present  in  larger organic  compounds
and can be detected by  TALMS.  To
demonstrate this detection  capability, a
benzene and chlorobenzene detecting
instrument has been constructed and
will be  delivered  to  EPA, Research
Triangle Park, NC,  before  January,
1982
  The TALMS technique has a number
of features that  are  useful for  deter-
mining toxic organic substances. It has
an inherent resolution exceeding 500,000
It utilizes a principle of operation  that is
totally different from the currently used
chromatographic methods  Therefore it
provides an independent  confirming
analysis. The sample pretreatment
required for the TALMS method is much
less than that required for chromato-
graphic procedures. It should be possible
to volatilize low boiling components
from a solid or liquid sample directly into
the light path of the instrument and
perform  the analysis  with no further
sample treatment Because the applica-
tion of TALMS analysis is simpler than
chromatographic procedures, it should
be possible  to develop an instrument
that requires less skill and experience
on the part of the analyst Samples may
be sealed in previously evacuated cells
and stored in the event another deter-
mination is required at a later date.
  In order to utilize the TALMS tech-
nique effectively, a data base of atomic
emission lines which match molecular
absorption features must be constructed.
The most logical way to do this is  simply
to make magnetic scans using emission
lines from atoms that have the highest
possible density of spectral lines in  the
region  where  molecular absorption is
intense  Future efforts  should  be
directed toward fabricating high inten-
sity light sources that produce as many
emission lines  as possible, toward
production of the data base required for
qualitative and quantitative analysis;
and  toward analysis  of complex en-
vironmental air samples

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      T. Hadeishi, R. McLaughlin, and J. Millaud are with the University of California.
        Berkeley. CA 94720.
      D. R. Scott is the EPA Project Officer (see below).
      The complete report, entitled "Development of a Tunable Zeeman Spectrometer
        for Analysis of Toxic Organic  Compounds," (Order No. PB 83-139 535; 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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