United States
               Environmental Protection
               Agency
 Atmospheric Research and
 Exposure Assessment Laboratory
 Research Triangle Park NC 27711
               Research and Development
 EPA/600/S3-90/091  Jan. 1991
EPA       Project Summary
               Evaluation  of  Particle  Beam
               Liquid Chromatography/Mass
               Spectrometry for the Analysis of
               Polar  Semivolatile  Organic
               Compounds  in Air Samples
              Robert S. Whiton
                 In the last few years, several Inter-
              faces have been developed for coupling
              high performance liquid chromatogra-
              phy (HPLC) and mass spectrometry
              (MS). Among the most recent is the
              particle beam interface. This report de-
              scribes the initial evaluation of a particle
              beam HPLC/MS system for the analysis
              of polar semivolatile organic com-
              pounds. The study focused on examin-
              ing and optimizing Instrumental operat-
              ing parameters, evaluating the ability of
              the Instrument to generate classical
              electron impact mass spectra of repre-
              sentative compounds, investigating the
              performance with chemical ionization,
              and evaluating the potential for quanti-
              tative analysis  with selected  com-
              pounds. Test compounds included hy-
              droxy-polycycltc aromatic hydrocarbons
              (PAH), nitro-PAH, amino-PAH, and hy-
              droxy-nltro-PAH. The report  describes
              the results  of these experiments and
              discusses several problems found in
              the current  particle beam Interface de-
              sign.
                 This Project Summary was devel-
              oped by EPA's Atmospheric Research
              and Exposure Assessment Laboratory,
              Research  Triangle Park, NC, to  an-
              nounce 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
                 Many current methods for the determi-
              nation of nonpolar organic compounds in
air are based on gas chromatography/mass
spectrometry (GC/MS), which utilizes the
high resolution achievable with chromato-
graphic separation and the sensitive, se-
lective detection and compound identifica-
tion of mass spectrometry. For analysis of
polar semivolatile organic compounds
(SVOCs), however, GC methods are limited
by the requirement that the analytes be
volatile and thermally stable. Compounds
that do not meet these requirements can
be analyzed by high performance  liquid
chromatography (HPLC), but standard de-
tectors for HPLC lack the sensitivity and
selectivity needed  for analysis of air
samples, and they do not provide the com-
pound identification  ability of the  mass
spectrometer.
   Efforts to couple HPLC and MS have
been  underway for more than 15 years.
The LC/MS interfaces that have seen sig^
nificant use  fall into several categories:
direct liquid introduction, liquid ion evapo-
ration, and solvent removal. Each of these
categories has its characteristic areas of
utility  and its particular deficiencies. The
particle beam interface introduced by
Browner and co-workers is one of the most
recent introductions.
  The particle beam  interface  uses a
nebulizer and momentum separator to re-
move the solvent vapor from the effluent
with little sample contact with heated sur-
faces. The analytes enter the MS ion source
as a  beam of dry particles and can be
ionized by a variety of conventional pro-
cesses, including electron impact  (El) and
chemical ionization (Cl) with any reagent
gas. Since commercial versions of the in-
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terfaca were introduced in 1988, the tech-
nique has been applied to a  variety  of
compounds of environmental interest, with
mixed results.  In analysis of diazo dyes,
the sensitivity was much worse than that
obtained with thermospray. Other classes
of compounds that have been analyzed by
particle beam LC/MS  include aromatic
sutfonic acids, phenylurea and carbamate
pesticides, and benzWines. Quantification
has been problematic, with  two groups
reporting concave calibration curves and
others reporting a carrier effect resulting in
response enhancement by coeluting com-
pounds.

Procedures
   The particle beam LC/MS interface is
optimized by adjusting the nebulizer posi-
tion and helium gas flow while repeating
injections of the compound of interest. The
MS Is tuned with the particle beam interface
inserted and solvent flowing. The tuning
compound (perfluorotributylamine) and/or
reagent gas are  introduced  through the
interface. Manual tuning generally produces
better results than the instrument  auto-
matic tuning procedure.

Results
   The particle beam LC/MS interface was
found to be reliable and relatively simple
and  straightforward to operate. Routine
optimization involves  only adjusting the
position of  the nebulizer capillary.  It was
beneficial to keep the ion source of the MS
slightly hotter than would be normal for the
corresponding GC/MS experiment. The
instrument  produces  good classical El
spectra for some classes of PAH deriva-
tives, although the quality of the  library
matches is variable. It produces unaccept-
able spectra for  nitro-PAH compounds,
which apparently are reduced to amines in
the ion source,J"his.may-result from pro^_
longed contact with the ion source walls
before the analytes are vaporized.
   The particle beam interface had diffi-
culties with phenolic compounds due to
adsorption in the interface. The adsorption
problem is manifested as tailing peaks,
carryover and reduced sensitivity for phe-
  Robert S. Wh'rton is with NSI Environmental Sciences, Research Triangle Park, NC
    27709.
  Nancy K. Wilson Is the EPA Project Officer (see below).
  The complete report, entitled "Evaluation of Particle Beam Liquid Chromatography/
    Mass Spectrometry for the Analysis of Polar Semivolatile Organic Compounds in
    Air Samples," (Order No. PB91-127746/AS; Cost: $15.00, 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:
          Atmospheric Research and Exposure Assessment Laboratory
          U.S. Environmental Protection Agency
          Research Triangle Park, NC 27711
 nolic  compounds. Hydroxy-nitro-PAHs
 could  not be detected at levels of approxi-
 mately 100 ng. The  adsorption problem
 was not  alleviated by use  of  an  acidic
 eiuent or the  addition of a deactivated
 glass  line to the desolvation chamber. The
 adsorption may be occurring in the overly
 long transfer line and the plastic cones of
 the momentum separator.
    The interface was  compatible with
 electron capture negative ionization (ECNI)
 for nitro-PAHs, with no apparent interfer-
 ence  from the solvent. Reduction  reac-
 tions on the walls of the ion  source are a
 problem when methane  is  used as the
 ECNI  moderating gas. With carbon dioxide
 as the moderating gas, the instrument pro-
 duces good ECNI spectra for nitro-PAHs,
^._^,,^
 but the  response is nonlinear.  Detection
 limits are approximately 1 ng by selected
 ion monitoring and 1 0 ng full scan.

 Conclusions and
 Recom mendations
    Overall, the performance of the particle
 beam interface has not lived up to expec-
 tations,  although  it is effective for certain
 compounds. Future modification  and
 evaluation pf the  system may make it a
 more reliable and versatile analytical tool.
 Some future activities to be carried out
 include: modification of the momentum
 separator to  replace the plastic cones and
 shorten the transfer line, testing of a quartz
 plate in the  ion source to minimize wall
 reactions,  testing with pesticides such as
 carbamates  and triazines, which are diffi-
 cult or impossible to analyze by GC, and
 testing of capillary column supercritical fluid
 chromatography/mass spectrometry as an
 alternative to LC/MS for hydroxy-PAH.
United States
Environmental Protection
Agency
       Center for Environmental Research
       Information
       Cincinnati, OH 45268
                 BULK RATE
           POSTAGE & FEES PAID
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Penalty for Private Use $300
EPA/600/S3-90/091

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