TN-4120-85-02
October 1985
    AUTOMATED CRYOGENIC SAMPLING AND GAS
    CHROMATOGRAPHIC ANALYSIS OF AMBJENT
       jr.
       VAPOR-PHAS£ ORGANIC. COMPOUNDS:
       PROCEDURES AND COMPARISON TESTS
Submitted to
U.S Environmental Protection Agency
Environmental Monitoring Systems Laboratory
Research Triangle Park, NC 27711

Under Contract 68-02-4035
NORTHROP

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                                                            TN-4120-85-02
AUTOMATED CRYOGENIC SAMPLING AND GAS CHROMATOGRAPHIC ANALYSIS OF

              AMBIENT VAPOR-PHASE ORGANIC COMPOUNDS:
                   PROCEDURES AND COMPARISON TESTS
                                  by

                  Karen D. Oliver and Joachim D. Pleil
            Northrop Services, Inc. - Environmental Sciences
                   Research Triangle Park, NC 27709
Submitted to:
                         Dr. William A. McClenny
                   Advanced Analysis Techniques Branch
                Environmental Monitoring Systems Laboratory
                   U.S. Environmental Protection Agency
                     Research Triangle Park, NC 27711


                         Contract No. 68-02-4035
Reviewed and Approved by:
        e,
N.E. Short
Program Manager
                        NORTHROP SERVICES, INC.
                       ENVIRONMENTAL SCIENCES
                              P.O. Box12313
                       Research Triangle Park, NC 27709

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NORTHROP                                                           TN41208502
Environmental Sciences
                                       DISCLAIMER
      This report  has been reviewed  by  Northrop Services,  Inc.  -  Environmental Sciences and
approved for publication.  Mention of trade names or commercial products does  not constitute
endorsement or recommendation for use.

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NORTHROP                                                       ™4208502
Environmental Sciences

                                     FOREWORD
      This report presents the results of work performed by Northrop Services, Inc. - Environmental
Sciences  under  Contract Number 68-02-4035 for the Advanced  Analysis Techniques Branch,
Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina. This work was conducted in response to Technical Directives 1.0-7 and
1.0-13 during the period May 1984 through March 1986.

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NORTHROP
Environmental Sciences
TN-4120-85-02
                                 TABLE OF CONTENTS
  SECTION                                                                    PAGE

    1   INTRODUCTION	      1

    2  EXPERIMENTAL  	      2
       2.1   Equipment 	      2
       2.2   Standards	      2
       2.3   Techniques	      3
       2.4   System Precision and Reproducibility	      4
       2.5   Nonlinearity of the ECD	      4
       2.6   Intercomparison Tests  	      4

    3  RESULTS AND DISCUSSION	      7
       3.1   System Precision and Reproducibility	      7
       3.2   Nonlinearity of the ECD	      7
       3.3   Intercomparison Tests	      8

    4  CONCLUSIONS AND RECOMMENDATIONS	     22

    5  REFERENCES	     23
                                         IV

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Environmental Sciences
TN-4120-85-02
                                    LIST OF FIGURES
  FIGURE                                                                        PAGE

    1   Schematic of Calibration System and Manifold  	    6
    2   Nonlinear Response of Carbon Tetrachloride on the ECD  	   18
    3   Nonlinear Response of Tetrachloroethylene on the ECD   	   19
    4   Nonlinear Response of Hexachlorobutadiene on the ECD  	   20
    5   Linear Response of Chloroform on the ECD  	   21
                                    LIST OF TABLES
   TABLE                                                                        PAGE

    1   Statistical Evaluation of Instrument Response Factors   	    10
    2  Summary of Percent Differences in Area Counts for Daily Calibrations  	    11
    3  Results of Intercomparison Tests  	    12
    4  Summary of Intercomparison Tests	    17

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NORTHROP
Environmental Sciences
                                                                           TN-4120-85-02
                                       SECTION 1
                                     INTRODUCTION
      A large number of volatile organic compounds are present at low concentrations in ambient
air, often at less than one part per billion by volume per compound.  A current concern of the U.S.
Environmental Protection Agency is the quantitation of certain ambient volatile organic compounds
that may pose threats to human health.
      In this laboratory, volatile organic compounds are collected by pulling ambient air through a
reduced temperature trap, so that various compounds are concentrated on the trap, but the major
air components, nitrogen and oxygen, pass through.  These compounds are then thermally desorbed
onto a high-resolution capillary column,  where they are separated by  gas chromatography in
conjunction with oven-temperature programming and  then  detected simultaneously by electron
capture and flame ionization.  The system has been automated so that consecutive samples can  be
analyzed with  minimal operator intervention. System design provides for analysis of samples from a
manifold at a stationary site or from canisters from the field.
      The hardware  configuration and automation of  the cryogenic sampling and  gas  chromato-
graphic system has been  addressed elsewhere (1).  The purpose of this note is to present  the
methodology of calibration and sample analysis, system precision, and results of interlaboratory
comparisons.

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NORTHROP
Environmental Sciences
                                                                            TIM-4120-85-02
                                        SECTION 2
                                      EXPERIMENTAL
2.1  EQUIPMENT
      The automated cryogenic sampling and  gas chromatographic (GC) system consists of a
Hewlett-Packard 5880A Level 4 GC equipped with a 50-m by 0.31-mm-i.d. by 0.17-nm film thickness
OV-1 fused silica, high resolution capillary column  (Hewlett-Packard, Avondale, PA), an  electron
capture detector (ECD), a flame ionization detector  (FID), and a modified Nutech 320-01 cryogenic
preconcentration unit (Nutech Corp., Durham, NC). Analysis of each sample requires 64 min - 15 min
for  system initialization, 14 min for sample collection, 30 min for analysis, and 5 min for post time,
during which a report is printed.  A detailed discussion of the automated sampling and  analysis
system can be found elsewhere (1,2).
      A Model MD-125-48(T)  Perma-Pure dryer (Perma-Pure Products, Farmingdale, NJ) is used to
remove water vapor from the sample gas stream prior to analyte preconcentration.  To  prevent
excessive moisture buildup and any memory effects  in the dryer, an automated  cleanup procedure
has been devised  in which the dryer is periodically heated and purged with zero air. Experiments
have been conducted to ensure that this analytical procedure does not alter sample integrity (2,3).
      For the most recent comparison tests,  a Hewlett-Packard HP-1 fused silica capillary column
(30-m x 0.530-mm-i.d.  x  0.88-nm film thickness) was installed, and the dryer was not used.

2.2  STANDARDS
      Two  Scott Environmental Technology, Inc., pressurized  cylinders containing a  mixture of
volatile organic compounds (VOCs) at nominal concentrations of 10ppmv  in nitrogen are used as
working standards. These cylinders contain the following compounds:
      •  Cylinder 1
           benzene, toluene,  o-xylene
      •  Cylinder 2
            vinyl chloride            methyl chloroform           1,2-dibromoethane
            vinylidene chloride       carbon tetrachloride         tetrachloroethylene
            1,1,2-trichloro-1,2,2-      trichloroethylene            chlorobenzene
             trifluoroethane         c;s-1,3-dichloropropene      benzyl chloride
            chloroform              trans-1,3-dichloropropene    hexachloro-1,3-butadiene
            1,2-dichloroethane

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NORTHROP
Environmental Sciences
                                                                            TN-4120-85-02
2.3 TECHNIQUES
2.3.1 Calibration Procedure
      A 1.25-in. i.d. glass manifold  is used for sample handling and preparation.  As shown in
Figure 1, this manifold consists of three lengths of  glass tubing,  two of which are aligned
horizontally,  one above the other.  These attach at right angles to a third length of tubing which
extends through the roof of the mobile laboratory and  arches into a "candy-cane" designed for
sampling ambient air.  A blower attached to the end of the upper manifold pulls sample gas through
the tubing at a rate of 40 L/min. The upper manifold is  used for ambient  air samples and the lower
manifold for calibration gas. The calibration manifold is insulated and heated to 60°C.
      For calibrations, the Scott gas mixtures are each passed through 0- to 50-cm3/min mass flow
controllers (MFCs; Tylan Corp., Carson, CA) into  the calibration manifold at nominal flow rates of
2 cm3/min. Zero air is passed through a 0- to 5-L/min MFC at a rate of 2 L/min and is humidified with a
500-mL impinger flask containing deionized water.  The two gas streams from the Scott cylinders and
the humid dilution air meet in  0.25-in.-o.d. Teflon tubing before reaching the manifold.  To ensure
thorough equilibration, this dynamic mixture, now at nominal concentrations of 8 ppbv for each
compound in Cylinder 2 and 11 ppbv for each compound in Cylinder 1, is allowed to flow through
the manifold for a minimum of 6 h before sampling begins.
      The calibration  mixture is sampled from the manifold  by pullfng 34  mL/min through
0.25-in.-o.d. Teflon tubing into a Teflon particle filter, and then through  the Perma-Pure dryer and
into the analysis system using a 0- to 50-mL/min MFC. A total sample volume of 476 ml is collected
on the trap by sampling for 14 min.  Normally, two consecutive analyses are performed, and the area
counts for each compound are averaged.  The flow rates for the gas mixtures and zero air  are
audited daily using a  soap film bubble flow meter.  Finally, precise dilution ratios,  calibration
concentrations, and instrument response factors (ppbv/area) are calculated and entered into  the
calibration tables for both detectors.

2.3.2 Ambient Air Samples
      Ambient outdoor air is pulled  into the upper manifold at a rate of 40 L/min through, the glass
"candy-cane" inlet tube (Figure 1).  Ambient air is analyzed by attaching the sample tubing to the
upper manifold and pulling sample gas into the system, as described for calibration samples.

2.3.3 Canister Samples
      Field samples are often collected in stainless steel canisters for analysis in this laboratory (4). If
the pressure in the canister is less than 12 psig when received, the sample is pressurized to 15 or
20 psig with nitrogen or zero air to  ensure that enough gas is available to complete the run.   The

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NORTHROP                                                            TN 4120 85 02
Environmental Sciences

pressure both before and after adding nitrogen or zero air is recorded, and the dilution factor is
calculated. The canister samples are then analyzed by venting the sample past the inlet to the system
at a  known rate of about 70mL/min using a 0- to 500-mL/min MFC.  This oversupplies the system
inlet, since the sample is collected at a rate of 34 mL/min.

2.4 SYSTEM PRECISION AND REPRODUCIBIL1TY
      A statistical evaluation of calibration data collected during a six-week period was performed
to determine the combined inherent error in the system and the various calibration procedures. As a
test  of reproducibility, the two daily calibration runs were compared for the  data set discussed
above.  One set of afternoon calibrations was not included  in the calculations because of a
contaminant in  the first run.

2.5 NONLINEARITYOFTHEECD
      In the past, the concentrations of carbon tetrachloride, tetrachloroethylene, and hexachloro-
butadiene detected were frequently lower on the BCD than on the FID. FID concentrations were
generally  in the expected range. When these three compounds were present  at concentrations close
to calibration levels, both detectors  agreed on the reported concentration.  The problem appeared
to be nonlinearity of the ECD.
      To  confirm this theory, calibration gas samples which ranged  in concentration from  0.1 to
8 ppbv were analyzed. Samples were prepared by altering the flow rates of zero air and the working
standards into the manifold or by pressurizing evacuated canisters with calibration gas and diluting
the gas mixture with zero air to known concentrations.

2.6 INTERCOMPARISON TESTS
      A number of comparison tests have been conducted to determine how well analyses on this
system compare with analyses performed on systems in other laboratories. An explanation of each
test is presented below.
      1.   NBS (National  Bureau of Standards).  A certified gaseous mixture of five compounds
          was analyzed.
      2.   RTI (Research Triangle  Institute, Research Triangle Park, NC).  Cylinder AAL-11933
          was obtained  from RTI and analyzed. The gaseous mixture was  analyzed by  RTI
          before and after analysis in this laboratory (5).
      3.   GKPB (Gas Kinetics and Photochemistry Branch, EPA, Research Triangle Park, NC). A
          sample of benzene, toluene, and o-xylene was placed in a stainless steel  canister,
          diluted, and analyzed.  The sample was then analyzed in a GKPB laboratory by
          cryogenic preconcentration-direct FID  measurement of  non-methane  organic
          carbon (NMOC)(6).  Concentrations from that laboratory were  converted  from
          ppbCto ppbv for comparison.

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NORTHROP                                                           TN-412WS02
Environmental Sciences


      4.  Scott (Scott Specialty Gases,  Plumsteadville,  PA).  A cylinder containing six
         compounds was analyzed twice within 10 months.

      5.  NSI-ES (Northrop Services, Inc. - Environmental Sciences, Research Triangle Park,
         NC).  A gaseous mixture of many of the calibration compounds used in this
         laboratory was prepared in the NSI-ES Standards Laboratory (7).  A sample was
         injected  into an evacuated  canister and diluted  with nitrogen to  known
         concentrations for analysis in this laboratory.

      6.  Matheson (Morrow,  GA).  A cylinder containing a  gaseous mixture of four
         compounds was prepared and certified by Matheson  and analyzed  in this
         laboratory.

      7.  22-City Study.  Field samples from an EPA study were analyzed in this laboratory and
         in the GKPB of  EPA (6).  Concentrations of benzene, toluene,  and o-xylene were
         compared for those samples analyzed by both laboratories.

      8.   RTI.  Three additional audit cylinders from RTI  (AAL-11948, AAL-12427, and AAL-
          15182)  were obtained and analyzed- These analyses were performed using the HP-1
         capillary column without the Perma-Pure dryer.

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Calibration Gas
Cylinder 1
Calibration Gas
Cylinder 2
                                             Air Blower
                               r
                          Ambient Air
                 Zero Air
                 Cylinder
                                                               Perma-Pure
                                                                 Dryer
                                                                  Out
To Analytical System
              Teflon Filter

            ^•r  Dry Purge
            "^     Gas
             In
                                    Humidifier
                         Figure 1. Schematic of Calibration System and Manifold.
                                                                                                                       o
                                                                                                                         ro
                                                                                                                         o
                                                                                                                         oo

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NORTHROP
Environmental Sciences
TN-4120-85-02
                                       SECTION 3
                                RESULTS AND DISCUSSION
3.1  SYSTEM PRECISION AND REPRODUCIBILITY
      For calibration data collected over a  six-week period, the mean, standard deviation, and
percent relative standard deviation (RSD) of instrument response factors for each compound on each
detector were calculated and  are presented in Table 1.  The  experimental error in the system
averaged 3.5% RSD for compounds which respond on the BCD and 8.2% RSD for compounds which
respond on the FID. With the exception of benzyl chloride, o-xylene, and hexachlorobutadiene (FID),
the RSD for individual compounds on each of the detectors was less than 10.0%.
      To test run-to-run reproducibility, the percent difference in area counts for each compound in
the afternoon calibrations was calculated for each day. The mean and standard deviation of percent
differences for each compound were then calculated and are  presented in Table 2.  The  mean
difference for afternoon calibrations was between -0.20 and  + 6.0% for compounds detected on the
FID and between -1.0 and +2.0% for compounds detected on the ECD.  The standard deviation for
FID compounds was within ±7.0%.  For ECD  compounds, the standard deviation  was within ±3.0%,
with the exception of 1,2-dibromoethane, which was ±6.1%.

3.2 NONLINEARITY OF THE ECD
      Concentration versus area was plotted for the 0.1- to 8-ppbv calibration compound  mixtures.
The plots of concentration versus area for calibration compounds detected by  the ECD confirmed
that  the  curves are  nonlinear for  carbon  tetrachloride,  tetrachloroethylene,  and
hexachlorobutadiene, as shown in  Figures 2-4. The remaining six  ECD compounds and the  FID
compounds scale linearly for the range 0 to 8 ppbv, as shown for chloroform in Figure 5. For the
three  compounds that are not linear over the calibration range, area counts generally begin to roll
off between 3 and 4 ppbv.  To correct for the nonlinearity of these compounds, an additional
calibration step is necessary.  An evacuated stainless steel canister is pressurized with calibration gas
at a nominal concentration of 8 ppbv.  The  sample is then diluted to approximately 3.5 ppbv with
zero air and analyzed. The instrument response factor (ppbv/area) on the ECD for each of  the three
compounds is calculated for the 3.5-ppbv sample. Then, both the 3.5-ppbv and the 8-ppbv response
factors are entered into the ECD calibration table.  Since  software that runs the analysis system is
designed to accommodate  multilevel  calibration entries,  the correct response factors will  be
automatically selected for calculating  concentrations.

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NORTHROP                                                          TN 4120 85 02
Environmental Sciences
3.3  INTERCOMPARISON TESTS
      Table 3 contains the results of the interlaboratory comparison tests. Concentrations in ppbv
are  reported, along with the percent difference in the two values. The percent difference (A%) was
calculated as follows:

                                  Difference in concentration
                            A% =	x 100
                                  Average of concentrations
A negative A% indicates that the concentration reported by this laboratory was the lower of the two
concentrations.  The mean A% for individual compounds in the intercomparison tests are presented
in Table 4.
      The percent differences  in concentrations in Table 3 show that most results from  this
laboratory are in line with results reported by other laboratories.  Many of the concentrations were
within ±20% of each other. Also, concentrations from this laboratory were sometimes greater and
sometimes less than concentrations reported by other  laboratories, rather than being consistently
biased in one direction.
      The comparisons with NBS, GKPB,  NSI-ES, the  second Matheson  sample, and RTI  15182
revealed differences in concentrations  within ±21%.  The results from  the  first Matheson
comparisons showed differences between -6.0 and +24.0%.  The RTI 11933  comparisons showed
differences between  -3.0 and -21.0%, with the exception of  tetrachloroethylene.   For
tetrachloroethylene, the A% was lower for the second RTI 11933  comparison than for the first.  The
first Scott comparison showed differences in concentrations of -4.6 to +38.6%. The second test,
conducted 10  months later, showed greater agreement with the exception  of toluene,
chlorobenzene,  carbon tetrachloride (ECD), and tetrachloroethylene (BCD).  In  the second
comparison,  the effects of ECD roH-off  can  be  seen in  the carbon  tetrachloride  and
tetrachloroethylene concentrations, which were lower than the FID concentrations.  (ECD roll-off did
not affect the first comparison, which was performed in 1983 using a sample volume of less than
476mL)  The comparisons for the 10 22-city study samples were within  ± 22%, with the exception of
samples 2409 and 1033, for which the concentrations were between -33.0 and +40.0%. The RTI
11948 comparison test  resulted  in differences between -10.4 and  +3.8%, with the exception of
chloroform on the ECD, for which the values differed  by +41.4%. This high ECD concentration was
unexplained and out of line with the FID analysis in which a + 3.8 A% was observed.  FID results for
the RTI 12427 comparison showed differences between -12.7 and + 13.6%.  However, ECD  results
from this laboratory were much higher  than the RTI analyses ( + 24.3 to 108 A%).   High  ECD
concentrations were presumably due to a  change in the FID/ECD  split ratio between calibration and
analysis.  This has since been corrected.

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NORTHROP                                                       ™4208502
Environmental Sciences

     Table 4 summarizes the intercomparison results. The average percent differences ranged from
-14.1 to +12.3%, with the exceptions of methyl chloroform ( + 20.7%) and  1,2-dibromoethane
( + 59.5%), both on the ECD.  The high  value for  1,2-dibromoethane was the average of two
comparisons, one of which was completely out of line with the other results.

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Environmental Sciences
TN-4120-85-02
     TABLE 1. STATISTICAL EVALUATION OF INSTRUMENT RESPONSE FACTORS (ppbv/area)
Compound
FID
vinyl chloride
vinylidene chloride
trichlorotrifluoroethane
chloroform
1,2-dichloroethane
methyl chloroform
benzene
carbon tetrachloride
trichloroethylene
c/s-1 ,3-dichloropropene
trans-1,3-dichloropropene
toluene
1 ,2-dibromoethane
tetrachloroethylene
chlorobenzene
o-xylene
benzyl chloride
hexachlorobutadiene
ECO
trichlorotrifluoroethane
chloroform
methyl chloroform
carbon tetrachloride
trichloroethylene
1 ,2-dibromoethane
tetrachloroethylene
hexachlorobutadiene
Mean, N a 33

0.56
0.43
0.48
1.28
0.41
0.38
0.14
1.71
0.38
0.29
0.29
0.11
0.44
0.33
0.13
0.09
0.16
0.28

2.39
6.97
1.98
0.80
5.59
2.96
1.07
0.88
Std. Dev.

0.04
0.03
0.03
0.08
0.02
0.02
0.01
0.08
0.02
0.02
0.02
0.01
0.04
0.02
0.01
0.01
0.03
0.05

0.09
0.21
0.06
0.01
0.13
0.18
0.04
0.04
RSD, %*

7.14
6.98
6.25
6.25
4.88
5.26
7.14
4.68
5.26
6.90
6.90
9.09
9.09
6.06
7.69
11.1
18.8
17.9

3.77
3.01
3.03
1.25
2.33
6.08
3.74
4.55
*RSD = relative standard deviation.
                                    10

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NORTHROP
Environmental Sciences
TN-4120-85-02
   TABLE 2. SUMMARY OF PERCENT DIFFERENCES IN AREA COUNTS FOR DAILY CALIBRATIONS*
Compound
FID
vinyl chloride
vinylidene chloride
trichlorotrifluoroethane
chloroform
1,2-dichloroethane
methyl chloroform
benzene
carbon tetrachloride
trichloroethylene
c/s-1,3-dichloropropene
trans-1,3-dichloropropene
toluene
1,2-dibromoethane
tetrachloroethylene
chlorobenzene
o-xylene
benzyl chloride
hexachlorobutadiene
ECD
trichlorotrifluoroethane
chloroform
methyl chloroform
carbon tetrachloride
trichloroethylene
1,2-dibromoethane
tetrachloroethylene
hexachlorobutadiene

Mean
(N = 32)

0.36
1.12
0.05
0.88
0.51
0.17
-0.15
-0.98
0.77
1.28
1.82
-0.19
1.46
1.18
2.04
0.33
4.39
5.54

0.44
0.46
0.29
0.07
0.75
0.34
-0.91
1.79
% Difference
Std. Dev.

2.86
4.32
4.08
6.47
3.05
2.46
2.54
5.75
3.12
3.43
3.71
3.15
4.02
3.45
4.03
3.84
6.04
5.85

1.24
1.71
1.17
0.38
1.33
6.10
2.90
1.68
'Percent Difference = (difference in area counts -=- average of area counts) x 100.
                                        11

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                                                                                                                                                          §"<
§'0
i*
(» 	 .*
3 ""^
ES
fa
TABLE 3. RESULTS OF INTERCOMPARISON TESTS (in ppbv)* I !g
1. NBS
EMSL
Compound Standard (N = 4) A*/>
2. RTI (AAL-1 1933) 2. RTI (AAL-11933) 3. GKPB 4. Scott (AAL-1 1745)
EMSL,
RTI. EMSL RTI. EMSL EMSL initial
Initial (N = 2) A% Second (N-2) A% GKPB (N = 1) A% Scott (N = 8) A%
FID
   vinyl chloride
   vinylidene chloride
   (richlorotrifluoroethane
   chloroform
   1,2-dichloroethane
   methyl chloroform
   benzene
   carbon tetrachloride
   irichloroelhylene
   c is-1,3-dichloropropene
   trans-1,3-dichloropropene
   loluene
   1,2-dibromoethane
   lelrachloroethylene
   chlorobenzene
   o-xylene
   benzyl chloride
   hexachlorobutadiene
ECO
   I richlorotrifluoroethane
   chloroform
   melhyl chloroform
   carbon tetrachloride
   trichloroethylene
   1,2-dibromoethane
   letrachloroethylene
   hexachlorobutadiene
                             38
                             8.7
                             77
                             64
                                    382   +0.52
9.02   +3.6
783   +167
                                    7 57  + 168
                            124   138   +10.7
                             38
                             77
                                    4 59  + 18 8
                                    886  +140
                            124   1248   +064
                                                      403    331  -196      408    331   -208
                  128    105  -19.7      126    105   -182
379    330  -138
323    286  -12.2
368    330  -109
296    286   -344
                  119    79   -40.4      103     79   -264
                  128    118   -813     126    118    -656

                  323    284  -129      296    284    -414


                  119    87   -31.1      103     87   -168
                                                                                                      163    183  +116
                                                                                                      189    183    -323
                                                                                                      191    184    -373
18    21.1    +159
20    224    +113
16    207    +256
                                                                         14    207   +386

                                                                         16    203   +237
                                                                         18    229   +240
                                                                         20    19 1     -4 60
                                                                         16    207    +256

                                                                         16    213    +284
                                                                                                                                                              oo
                                                                                                                                                              en
                                                                                                                                                              •
                                                                                                                                                              o
                                                                                                                                                              to
A ilestnprion ol each test ii presented in Section 2 6
                                                                                                    (continued)

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TABLE 3. (Continued)
4. Scott (AAL-1 1745)
EMSL,
second
Compound Scott (N = 1) A%
FID
vinyl chloride
vinylidene chloride
trichlorotrifluoroelhane
chloroform
1 ,2-dichloroethane
methyl chloroform
benzene 18 1989 +9.98
carbon tetrachloride 20 19.02 -5.02
trichloroethylene 16 18.61 +15.1
cis- 1 ,3-dichloropropene
(fans 1 ,3-dichloropropene
toluene 14 9.10 -42.4
1 ,2-dibromoe thane
tetrachloroethylene 16 18.33 +13.6
chlorobenzene 18 8.13 -7.56
o-xylene
benzyl chloride
hexachlorobutadiene
ECO
trichlorolrifluoroethane
chloroform
methyl chloroform
carbon telrachloride 20 9.60f -70.3
trichloroethylene 16 1926 +185
1 ,2-dibromoethane
tetrachloroethylene 16 10.24t -43.9
hexachlorobutadiene
t ECD roll oil resulted in this low measurement, this comparison is not used
5
Calculated


11.79
7.91
1365
11.96
9.44
1060
9.75
10.51


1033
7.29
9.21
927
7.80



791
1365
944
975
1051
7 29
921

. NSI-ES 6. Matheson Cylinder
EMSL
(N = 3)


12.07
801
14.01
11 14
952
1099
1028
1000


973
6.47
866
792
627



828
15 10
11 01
891
11 92
8 14
972

EMSL.
first
A* Calculated (N = 1) A%


+ 235
+ 1 26
+ 260
-7.10
+ 084 677 812 +18.1
+ 361 6.98 6.61 -545
+ 529 705 7.29 +3.35
-497 719 682 -528


-598
-11.9
-6.16
-157
-21 8



+ 4.57
+ 10 1
+ 154 677 854 +231
-900 705 788 +111
+ 126 719 686 -470
+ 110
+ 5 39

in subsequent calculations
6. Matheson Cylinder
EMSL,
second
Calculated (N = 1) A%






713 8.05 +121
736 658 -112
7.43 800 +7.39
758 6.90 -939












713 8.71 +19.9
743 794 +664
758 713 -612



(continued)
                                                                             K)
                                                                             O

                                                                             do
                                                                             Ul

                                                                             O
                                                                             K)

-------
                                                           TABLE 3. (Continued)                                                                         J;
                               7. 22-City Study         7. 22-City Study          7. 22-City Study          7. 22-City Study          7. 22-City Study
                                   (230H)                  (2409)                  (1053)                  (1033)                  (1027)
                                     EMSL                    EMSL                    EMSL                    EMSL                    EMSL
         Compound           GKPB  (N = i)   A%       GKPB   (N = I)    AS      GKPB   (N = I)    A%       GKPB   (w = i)    A%       GKPB  (N = I)    A%
FID     ~~~~~                                                                                                                     ~~~~~
  vinyl chloride
  vinylidene chloride
  trichlorotrifluoroethane
  chloroform
   1,2-dichloroethane
  methyl chloroform
  benzene                     405    381   -611      4.10    296 -32.3       3.39   349   +291       1.27    1.64  +254      669   575 -15.1
  carbon tetrachloride
   trichloroethylene
   cis-1,3-dichloropropene
   trans-1,3-dichloropropene
   toluene                      741    680   -859      8.11    583-327       260   261   +038       421    539+246     15.35  1368-115
   1,2-dibromoethane
   tetrachloroethylene
   chlorobenzene
   o-xylene                     1.59    162   +187       1.53    121 -23.4                               071    1.06  +396      237   238  +042
   benzyl chloride
   hexachlorobutadiene
 ECD
   trichlorotrifluoroethane
   chloroform
   methyl chloroform
   carbon tetrachloride
   trichloroethylene
   1,2-dibromoethane
   tetrachloroethylene                                                                                                                                            _)
   hexachlorobutadiene	                 f-
  Sample identification number                                                                                                             (continued)                  KJ
                                                                                                                                                                 O
                                                                                                                                                                 oo
                                                                                                                                                                 Ul
                                                                                                                                                                 I
                                                                                                                                                                 o
                                                                                                                                                                 KJ

-------
                                                           TABLE 3. (Continued)
                               7. 22-City Study         7.  22-City Study          7. 22-City Study          7. 22-City Study         7. 22-City Study
                                    (2250)                  (1984)                  (1985)                  (2368)                   (2269)
                                     EMSL                   EMSL                    EMSl                    EMSL                    EMSL
	Compound	GKPB  (N=I)   A%	GKPB   (N = I)    A%	GKPB   (n-1)    A%	GKPB   (N = l)   A%	GKPB   (N = I)   A%
__

  vinyl chloride
  vinylidene chloride
  trichlorotri fluoroethane
  chloroform
   1,2-dichloroethane
  methyl chloroform
  benzene                     156    158  +127       1.29    1.26  -2.35      2.14   2.02   -577      464   4.74  +213      1.72   1.99 +146
  carbon tetrachloride
  trichloroethylene
  cis-1,3-dichloropropene
   trans-1,3-dichloropropene
  toluene                      333    329   -1.21       419    393  -6.40      552   5.21   -578      1478   14.35  -295      3.58   388 +804
   1,2-dibromoethane
  telrachloroethylene
  chlorobenzene
  o xylene                     060    073  +196       0.53    0.45-163        0.87   1.07  +206      219   267 +198      066   082 +216
  benzyl chloride
  hexachlorobutadiene
ECD
   Irichlorotri fluoroethane
  chloroform
  methyl chloroform
  carbon tetrachloride
  trichloroethylene                                                                                                                                        —(
   1  2-dibromoethane                                                                                                                                       '
                                                                                                                                                          &
  tetrachloroethylene                                                                                                                                     -•
                                                                                                                                                          KJ
  hexachlorobutadiene                                                                                                                                    O
	—	                                                                                                                            —	          oo
                                                                                                                                     (continued)           V1

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                                                                        M"

                                                                        fi
                                                                        i:
TABLE 3. (Continued)
8. RTI(AAL-11948)
EMSL
Compound RTI (N = 2) A%
FID
vinyl chloride 20 20.0 0
vinylidene chloride
trichlorotrifluoroethane
chloroform 37 38.4 +3.8
1 ,2-dichloroethane
methyl chloroform
benzene 19 197 +3.7
carbon tetrachloride 9.6 9.1 -5.2
trichloroethylene
c/'s- 1 ,3-dichloropropene
trans- 1 ,3-dichloropropene
toluene
1,2-dibromoethane
tetrachloroethylene 9.1 9.2 +1.1
chlorobenzene
o-xylene
benzyl chloride
hexachlorobuladiene
BCD
trichlorotrifluoroethane
chloroform 37 52.3 +41.4
methyl chloroform
carbon tetrachloride 9.6 8.6 -10.4
trichloroethylene
1 ,2-dibromoethane
tetrachloroethylene 9.1 8.4 -7.7
hexachlorobutadiene
8. RTI (AAL-1 2427) 8. RTI (AAL-15182)
EMSL EMSL
RTI 
-------
NORTHROP
Environmental Sciences
                                                             TN-4120-85-02
                  TABLE 4. SUMMARY OF INTERCOMPARISON TESTS
Compound
FID
vinyl chloride
vinylidene chloride
trichlorotrifluoroethane
chloroform
1,2-dichloroethane
methyl chloroform
benzene
carbon tetrachloride
trichloroethylene
c/s-1 ,3-dichloropropene
trans- 1 ,3-dichloropropene
toluene
1,2-dibromoethane
tetrachloroethylene
chlorobenzene
o-xylene
benzyl chloride
hexachlorobutadiene
ECD
trichlorotrifluoroethane
chloroform
methyl chloroform
carbon tetrachloride
trichloroethylene
1,2-dibromoethane
tetrachloroethylene
hexachlorobutadiene
N

3
2
2
5
2
4
20
9
6
-
-
16
2
7
4
11
-
-

2
5
4
8
6
2
6
-
Avq. A%

-13.5
+ 1.73
-t-4.53
-6.20
-9.90
+ 7.76
-0.41
+ 0.35
+ 1.86
-
-
-1.37
+ 0.85
-3.41
-14.1
+ 5.29
-
-

-0.67
+ 11.1
+ 20.7
-1.16
+ 12.3
+ 59.5
-3.53
-
                                   17

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NORTHROP
Environmental Sciences
                                                                        TN-4120-85-02
                                      4567


                                     Concentration (ppbv)
10
Figure 2. Nonlinear Response of Carbon Tetrachloride on the ECO. The solid lines approximate the

multi-level calibration used by system software for concentration calculations.
                                          18

-------
NORTHROP
Environmental Sciences
                                                                         TN-4120-85-02
   100,000
         0 >
                                       456


                                      Concentration (ppbv)
10
Figure 3. Nonlinear Response of Tetrachloroethylene on the ECD. The solid lines approximate the

multi-level calibration used by system software for concentration calculations.
                                          19

-------
NORTHROP
Environmental Sciences
                                                                        TN-4120-85-02
  100,000 -
         01       23456789

                                     Concentration (ppbv)



Figure 4. Nonlinear Response of Hexachlorobutadiene on the ECO. The solid lines approximate the

multi-level calibration used by system software for concentration calculations.
                                         20

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NORTHROP
Environmental Sciences
                                                                          TN-4120-85-02
160,000 T
140,000  •
120,000  •
100,000  •
c

3


U


-------
NORTHROP
Environmental Sciences
TN-4120-85-02
                                        SECTION 4
                          CONCLUSIONS AND RECOMMENDATIONS


      The automated cryogenic sampling and GC system has been used successfully for trapping a
number of VOCs. The  inherent error in the system and procedures has been demonstrated to
average 8.2% RSD for the FID and  3.5% RSD for the BCD.  Also, reproducibility when using this
system is good; the average percent difference in area counts of compounds varied between -1.0
and  +5.6%, as shown  in daily calibrations.  The intercomparison tests demonstrated that results
obtained with this system are generally within ±20% of results from other laboratories.   The
intercomparison tests also showed that historically the results from this laboratory  have improved
and have become more  internally consistent as the technique has been further refined.
      It is recommended that the  list of VOCs for which the system is calibrated be expanded. Also,
experiments should be  conducted with other types of capillary columns to develop procedures to
eliminate the Perma-Pure dryer and to add  polar compounds to the calibration list.  Since FID and
ECD results were occasionally inconsistent, the parallel FID/ECD split arrangement should be
eliminated. Instead, the ECD and FID should be arranged in series. This configuration has been used
in the-past with only minimal loss of resolution on the FID. Greater sensitivity also would be achieved
since the total sample volume would pass through both detectors rather than being split between
the two.
                                           22

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NORTHROP                                                            TN-4120-85-02
Environmental Sciences
                                        SECTION 5

                                       REFERENCES
1.  Pleil, J.D. 1982. Automated cryogenic sampling and gas chromatographic analysis of ambient
   vapor-phase organic compounds:  system design.   EPA Contract No. 68-02-2566.  Research
   Triangle Park, NC;  Northrop Services, Inc. - Environmental Sciences.

2.  McClenny, W.A.,  J.D.  Pleil, M.W.  Holdren, and R.N.  Smith.   1984.  Automated cryogenic
   preconcentration and gas chromatographic determination of volatile organic compounds. Anal.
   Chem. 56:2947.

3.  Pleil, J.D. and K.D. Oliver.  1985.  Evaluation of various configurations of Nafion dryers: water
   removal from air samples prior to gas chromatographic  analysis.  EPA Contract No.  68-02-4035.
   Research Triangle Park, NC: Northrop Services, Inc. - Environmental Sciences.

4.  Oliver, K.D., J.D. Pleil, and W.A. McClenny. In Press. Sample  integrity of trace level volatile
   organic compounds in ambient air stored in SUMMA® polished canisters. Atmos. Environ.

5.  Jayanty, R.K.M., W.F. Gutkrtecht, and  C.E. Decker. 1983. Status report #5: stability of organic
   audit materials and results of source test analysis audits.  EPA Contract No. 68-02-3431. Research
   Triangle Park, NC:  Research Triangle Institute.

6.  McElroy, F.F., V.L.  Thompson, D.M. Holland, W.A. Lonneman, and R.L. Seila.  In Press. Cryogenic
   preconcentration-direct FID method for  measurement of ambient  NMOC:  refinement and
   comparison with GCspeciation. JAPCA.

7.  U.S. Environmental Protection Agency. 1984.  Standard operating procedure: volatile organics
   standards laboratory - standards preparation. EMSL/RTP-SOP-QAD-528.  Research Triangle Park,
   NC: U.S. Environmental Protection Agency.
                                            23

-------
0
4567
Concentration (ppbv)
8
10

-------
 1,000,000  •
   900,000  •
c
u
ru
cu

<
   400,000 '





   300,000 •
           0
  456


Concentration (ppbv)
8
10

-------
200,000 • •





100,000 --


        i
        /
        Jr

        0
 456

Concentration (ppbv)
8
10

-------
 160,000 T
 140,000 •
 120,000 -
 100,000 ••
o

-------