United States
                  Environmental Protection
                  Agency
 Environmental Monitoring Systems
 Laboratory
 Research Triangle Park NC 27711
                  Research and Development
 EPA/600/S4-85/032  June 1985
&EPA        Project Summary
                  Stability of  Parts-Per-Billion
                  Hazardous  Organic Cylinder
                  Gases  and  Performance Audit
                  Results  of Source Test and
                  Ambient Air Measurement
                  Systems:  Status  Report #1

                  R. K. M. Jayanty, S. W. Cooper, J. Sokash, C. E. Decker, and D. J. von Lehmden
                   A repository of 14 gaseous organic
                  compounds at  parts-per-billion (ppb)
                  levels in compressed gas cylinders has
                  been  established under the contract
                  with the Environmental Protection Agen-
                  cy (EPA), the primary objectives of this
                  on-going project are: (1) to provide
                  accurate gas mixtures to EPA, state/
                  local agencies, or their contractors for
                  performance audits to assess the rel-
                  ative accuracy of source measurement
                  systems during hazardous waste trial
                  burn tests and ambient air monitoring
                  programs; (2) to verify the manufactur-
                  er's certified analysis of the multi-com-
                  ponent gas mixtures with time; (3) to
                  determine the stability of the gas mix-'
                  tures with time; and (4) to develop new
                  audit materials as requested by EPA.
                   The repository consists of two mix-
                  tures of five and nine organic compounds
                  each. These mixtures were blended in
                  aluminum cylinders in a balance gas of
                  nitrogen. The five component mixture
                  (Group I) contains carbon tetrachloride,
                  chloroform, perchloroethylene, vinyl
                  chloride, and benzene. The nine com-
                  ponent mixture  (Group II)  includes
                  trichloroethylene, 1,2-dichloroethane,
                  1,2-dibromethane, acetonitrile, trichlo-
                  rofluoromethane, dichlorodifluorome-
                  thane, bromomethane,  methyl ethyl
                  ketone, and 1,1,1-trichloroethane. To
                  date, 20 performance audits have been
initiated and 12 are complete. The results
of these audits and a description of the
experimental procedures used for anal-
yses  and available stability data are
presented in this status report. General-
ly, the results of the audits show close
agreement (plus or minus 50 percent)
with the audit material concentrations
measured by Research Triangle Institute.
  Limited stability studies of  all 14
gaseous organic compounds have been
performed. Results indicate that all the
compounds tested are adequately stable
for use as reliable audit materials.
Detailed  statistical analyses  which
would separate statistical deviations
from true concentration changes with
time are in progress and will be pre-
sented in a future report.
  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
  The application of Quality assurance
practices is important to the generation of
high-quality environmental data. The
Quality Assurance  Division  of  EPA's

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Environmental Monitoring Systems Lab-
oratory has initiated a program to supply
audit materials for use during hazardous
waste trial burn tests and  ambient air
measurements. The  Research  Triangle
Institute (RTI), under contract to the U.S.
Environmental  Protection  Agency
(USEPA), has  responded to this  need
through development of a repository of 14
gaseous organic compounds at parts-per-
billion (ppb) levels in compressed gas
cylinders. The gaseous compounds  are to
be used in performance audits as desig-
nated by the EPA Project Officer. These
performance  audits are to  assess  the
relative accuracy of source measurement
systems during  hazardous  waste trial
burn tests  and ambient air monitoring
programs.
  The repository currently contains 14
compounds selected  on the  basis  of
anticipated needs of EPA's Office of Solid
Waste. Table 1 lists the  14 compounds,
the concentration ranges, andthe number
of cylinders for each group in the repos-
itory. The balance gas for all gas mixtures
is nitrogen  and the cylinder construction
material is aluminum.
  The gaseous compounds are  acquired
from commercial suppliers in compressed
gas cylinders; these same cylinders,  along
with an appropriate delivery system,  are
used directly as sources of the gaseous
compounds during performance audits.
The accuracy  of  the supplier-reported
levels of these compounds  are verified
through measurement using commercial
permeation tubes. The permeation rates
of the commercially available tubes  are
verified gravimetrically by RTI before use.
  The accuracy of the "known" cylinder
concentrations  and the  stability of  the
compounds in the cylinders are important.
Along with acquisition of new compounds
and verification of their  concentrations,
an  extensive  stability study  is  being
performed. This study involves periodic
analyses of the contents of each of the
cylinders in the repository.


Procedure
  Once a mixture of compounds is  chos-
en, a commercial supplier is contacted to
determine if a cylinder containing  those
compounds can be  prepared. If so,  the
manufacturer prepares the cylinder  gases
and determines the concentration  of the
analytes in the cylinder  by at least two
times. The cylinder is sent to RTI where its
contents are analyzed usually within ten
days of its arrival. If the RTI  value varies
from the manufacturer's value by  more
than 25 percent, an analysis is usually
Table  1.   PPB Level Organic Gases in
          Repository
Group
Group 1*

Group II"*

No. of
Cylinders
20
12
13
3
Concentration
Range of
Each Compound
(ppb)
7-90
90-430
7-90
90-430
 "Group I Compounds—carbon tetrachloride,
  chloroform, perchloroethylene, vinyl chlo-
  ride, and benzene.
""Group II  Compounds—trichloroethylene,
  1,2, -dichloroethane,  1,2-dibromoethane,
  acetonitrile, trichlorofluoromethane (Freon-
  111, dichlorodifluoromethane (Freon-12),
  bromoethane, methylethylketone, and
  1,1,1 -trichloroethane.
performed by a third party (EPA or NBS).
The gas mixtures are again analyzed at 2
months,  6 months,  and  at  one year
following the initial analysis to determine
the stability of the gas mixtures.
  All  analyses are performend using a
Hewlett-Packard 5880A gas chromato-
graph equipped with flame ionization and
electron capture detectors. The electron
capture detector (ECD) has  been used
principally  for measurement of all the
chlorinated hydrocarbons  except vinyl
chloride. Vinyl chloride, benzene, methyl
ethyl ketone, and acetonitrile are analyzed
with flame ionization detector (FID). The
gaseous samples are  injected onto the
columns by  means of  a  six-port gas
sampling valve constructed of Hastalloy C
(high  nickel content and low adsorption
properties) mounted near  the injection
port. The valve is equipped  with  inter-
changeable sampling loops (1 cc and 10
cc) to allow the injection of variable but
known volumes of gas. The gas chromato-
graphic parameters used in the measure-
ment of individual compounds are des-
cribed in the status report.
  Permeation tubes purchased from Met-
ronics are generally used as calibration
standards for all 14 organic compounds
unless otherwise specified. The permea-
tion  rate  of  each permeation tube  is
determined every 15  to  30  days  by
weight-loss determination of each tube.
  The RTI supplies repository cylinders
for audits upon request from the EPA,
state, or local agencies or their contrac-
tors. When a request  is  received, the
cylinder  is then  shipped  by a  freight
carrier to the laboratory being audited. A
letter is also  included with the cylinder
which provides general instructions for
performance of the  audit. The audi
concentrations are provided to the re
questing agency Audit Coordinator. Aftei
the laboratory being audited has analyzec
the contents of the cylinder, the Audi'
Coordinator reports the value(s) to RTI
which in turn reports both the measurec
and accepted values to the Project Officer
There is no charge for the audit except the
cost of returning the audit cylinder.


Results and Discussion
  To date, 20  performance audits have
been initiated; 15 are complete. All audits
initiated  have  been  for  Group I com-
pounds, since Group II compounds have
only recently been verified and approved
for  performance audits. The results ob-
tained for  a few  typical performance
audits are shown in Table 1  and the rest
are given in  the status report. Generally,
the audit results are within ± 50 percent
of the audit concentrations measured by
RTI.
  Most of the cylinders in the repository
are analyzed two to three times to deter-
mine the stability of the compounds.
  Relative accuracies of the cylinder gas
analyses for Group I compounds have
been determined using the NBS primary
standards. However, relative accuracies
of  cylinder  gas analyses for  Group  II
compounds  will not be established until
NBS primary standards are analyzed in
conjunction with these gas cylinders. This
will be done during the third RTI analyses
of group II cylinder gases. An examination
of stability data in the status report shows
values for Group I individual cylinder gas
analyses usually  vary by less than  10
percent for 3 analyses over an 8-month
period. Since only 3 months of stability
analyses are currently available in Group
II cylinders, a statement of the variability
will be  made  in  a future  report. This
variation indicates changes in  cylinder
contents (i.e., instability) and the impreci-
sion of  the  measurement process. The
possible sources  of experimental error
that could result in apparent changes in
concentrations include: (1) the variability
of  the  analytical  technique used for
analyses; (2) stability of and/or accuracy
of  calibration  standards; and  (3)  the
accuracy of reproducing standards. Each
of these sources of variability contributes
to the net uncertainty of the  resulting
stability  data.  Estimates of day-to-day
measurement uncertainty (repeatability)
for  Group I and Group II compounds have
not been performed at the present time.
However, the repeatability  measure-^
ments to determine the total uncertainty^

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will be performed in the near future. The
repeatability measurement results will be
included in a future report. The uncertain-
ty for the gas chromatographic measure-
ment has been determinedto be less than
3 percent by multiple injections of the gas
during same-day analysis.

Conclusions
  A  repository of  14 gaseous organic
compounds at parts-per-billion levels in
compressed gas cylinders has been used
successfully  in  audits  to  assess the
relative accuracy and precision of anal-
ytical  systems,  especially  those used
during hazardous waste trial burn tests
and ambient air  monitoring. To date, 20
performance audits have been  initiated
and 15 are complete. Generally the audit
results are within  ± 50 percent of the
audit concentrations measured  by RTI.
  Limited stability studies of all 14 gas-
eous  organic compounds  have  been
performed to determine the feasibility of
using them  as audit materials. Results
indicate that all of the organics tested are
adequately stable to be used as reliable
audit materials. Detailed statistical anal-
yses which would  separate statistical
deviations from true concentration chang-
es with time are in progress and will be
presented in a future report.
R. K. M. Jayanty, S. W. Cooper. J. Sokash. and C. £. Decker are with Research
  Triangle Institute, Research Triangle Park. NC 27709.
DarrylJ. von Lehmden is the EPA Project Officer (see below}.
The complete report, entitled "Stability of Parts-Per-Bil/ion Hazardous Organic
  Cylinder Gases and Performance Audit Results of Source Test and Ambient Air
  Measurment Systems. "(Order No. PB85-188 860/AS; Cost: $11.50. 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: 1965-559-01027080

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