EPA 600/4-81-057
United States
Environmental Protection
Agency
&EPA Research and
Development
The Analysis of Aromatic Chemicals ,
In Water by the Purge and Trap Method
Method 503.1
Prepared for
Joseph A. Cotruvo
Director
Criteria and Standards Division
Office of Drinking Water
Prepared by
Thomas A. Bellar
James J. Lichtenberg
Physical and Chemical Methods Branch
Environmental Monitoring and Support Laboratory
Cincinnati, Ohio 45268
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The Analysis of Aromatic Chemicals
in Water by the Purge and Trap Method
Method 503.1
1. Scope
1.1 This method is applicable in the determination of those compounds,
listed in Table I, contained in finished drinking water, raw source
water, or drinking water in any stage of treatment.
1.2 The actual detection limits are highly dependent upon the ability
of the analyst to properly maintain the entire analytical system.
Using carefully optimized equipment, the method has been proven to
be useful for the detection and measurement of multicomponent mix-
tures spiked into finished water, carbon-filtered finished water,
and raw source water at concentrations between 0.05 and 0.5 ug/1.
The method as described is capable of accurately measuring those
compounds listed in Table I over a concentration range of 0.05 to
5.0 ug/1. In addition, it is possible to measure individual com-
pounds up to 1500 ug/1. However the ability to measure complex
mixtures containing co-eluting or partially resolved compounds with
concentration differences larger than a factor of 10 is hampered.
U. S. Environmental Protection Agency, Environmental Monitoring and
Support Laboratory, Physical and Chemical Methods Branch, Organic Analyses
Section, Cincinnati, Ohio 45268, May 1980.
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1.3 This method is recommended for use only by analysts experienced in
the measurement of purgeable organics at the low yg/1 level or by
experienced technicians under the close supervision of a qualified
analyst.
2. Summary
2.1 An extraction/concentration technique is incorporated within the
method which enhances the quantities of certain compounds injected
into the gas chromatograph by a factor of 1000 over direct injec-
tion gas chromatography.
2.2 Aromatics are extracted by an inert gas which is bubbled through
the aqueous sample. The compounds, noted in Table I along with
other organic constituents which exhibit low water solubility and
boil less than 200°C, are efficiently transferred from the
aqueous phase to the gaseous phase. These compounds are swept from
the purging device and are trapped in a short column containing a
carefully selected mixture of sorbent materials. After a pre-
determined period of time, the trapped components are dried then
thermally desorbed and backflushed onto the head of a gas
chromatographic column where they are separated under programmed
temperature conditions.
2.3 Measurement is accomplished with a photoionization detector which
minimizes interference and baseline instability problems commonly
encountered with flame ionization detectors.
2.4 If sufficient material is present, confirmatory analyses are or may
be performed by gas chromatography-mass spectrometry.
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2.5 Aqueous standards and samples are extracted and analyzed under
identical conditions to compensate for extraction losses.
2.6 The total analysis time is approximately 1 hour per sample for all
of the compounds listed in Table 1.
Interferences
3.1 Impurities contained in the purge gas and organic compounds out-
gasing from the plumbing ahead of the trap usually account for the
majority of contamination problems. The presence of such inter-
ferences is easily monitored using the quality control program
described herein. Sample blanks are normally run between each set
of samples. When a positive response is noted in the sample blank,
the analyst should analyze a method blank in order to identify the
source of contamination. Method blanks are run by charging the
purging device with reagent water and analyzing it in the normal
manner.
Whenever potential interfering peaks are noted in the method blank,
the analyst should change the purge gas source and regenerate the
molecular sieve purge gas filter. Subtracting blank values from
sample results is not recommended. The use of non-TFE plastic
tubing, non-TFE thread sealants, or flow controllers with rubber
components in the purging device should be avoided since such
materials out-gas organic compounds which will be concentrated in
the trap during the purge operation. Such out-gasing problems are
common whenever new equipment is put into service. With use, minor
out-gasing problems generally cure themselves.
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3.2 Several instances of accidental sample contamination have been
noted and attributed to diffusion of volatile organics through the
septum seal and into the sample during shipment and storage. The
sample blank is used as a monitor for this problem.
3.3 For compounds that are not efficiently purged, such as naphthalene,
small variations in sample volume, purge time, purge flow rate,
purging device geometry, or purge temperature can affect the
analytical result. Therefore, samples and standards must be
analyzed under identical conditions.
3.4 Cross-contamination can occur whenever high level and low level
samples are sequentially analyzed. To reduce the likelihood of
this, the purging device and sample syringe should be rinsed out
twice between samples with reagent water. Whenever an unusually
concentrated sample is encountered, it is necessary that it be
*
followed by a sample blank analysis to check for sample cross-
contamination. For samples containing large amounts of water
soluble materials, suspended solids, high boiling compounds or high
levels of compounds being determined, it may be necessary to wash
out the purging device with a soap solution, rinse with distilled
water, and then dry in an oven at 105°C between analyses.
3.5 Qualitative misidentifications are a potential problem in gas
chromatographic analysis. Whenever samples whose qualitative
nature is unknown are analyzed, the following precautionary
measures should be incorporated into the analysis.
3.5.1 Perform duplicate analyses using columns with dissimilar
polarities.
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3.5.2 Select a lamp for the photo ionization detector that provides
the minimum ionization potential required to ionize the
compounds of interest. (See photoionization detector
operators manual.)
3.5.3 Whenever possible, use GC/MS techniques which provide
unequivocal qualitative identifications.
4. Apparatus
4.1 The purge and trap equipment consists of three separate pieces of
apparatus: the purging device, trap, and desorber. Construction
details for a purging device and an easily automated trap-desorber
hybrid which has proven to be exceptionally efficient and repro-
ducible are shown in Figures 1 through 6 and described in 4.1.1
through 4.1.3. All of the single lab data supplied in this method
were obtained from an instrument of this design.
4.1.1 Purging Device - Construction details are given in Figure 1
for an all-glass 5 ml purging device. The glass frit
installed at the base of the sample chamber allows finely
divided gas bubbles to pass through the sample while the
sample is restrained above the frit. Gaseous volumes above
the sample are kept to a minimum to eliminate dead volume
effects, yet allowing sufficient space for most foams to
disperse. The inlet and exit ports are constructed from
heavy wall 1/4 inch glass tubing so that leak-free removable
connections can be made using "finger-tight" compression
fittings containing Teflon ferrules. The removable foam
trap is used to control samples that foam.
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4.1.2 Trapping Device - The trap (Figure 2) is a short gas chro-
matographic column which at ambient temperature (22°C)
retards the flow of the compounds of interest while venting
the purge gas. The trap is constructed with a low thermal
mass so that it can be rapidly heated for efficient desorp-
tion, then rapidly cooled to room temperature for recycling.
Variations in the trap ID, wall thickness, sorbents, sorbent
packing order, and sorbent mass can adversely affect the
trapping and desorption efficiencies for certain compounds
shown in Table I. Pack the trap according to Figure 2.
4.1.3 Desorber assembly - Details for the desorber are shown in
Figures 3 through 6. With valve 1 in the Purge-Sorb
position (See Figure 3), the effluent from the purging
device passes through the trap where the movement of the
organics is retarded. The GC carrier gas also passes
through valve 1 and is returned to the GC. With valve 1 in
the Purge-Sorb position, the operation of the GC is in no
way impaired; therefore, routine liquid injection analyses
can be performed using the gas chromatograph in this mode.
After the sample is purged, residual water is removed from
the trap by turning valve 2 to the "trap dry position" (See
Figure 4). The purge gas is rerouted so that it does not
pass through the purging device. At a flow rate of 40
ml/minute the retention time for water and methanol on the
23 cm Tenax trap is less than 3 minutes; therefore, with
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valve 2 in the "trap dry position" for four minutes most of
the residual water is removed from the trap by the anhydrous
purge gas. (Both water and methanol cause a large negative
response early in the analysis. This can cause measurement
errors unless this drying procedure is used.) After the
trapped sample has been dried, valve 1 is turned to the
desorb position (See Figure 5). In this configuration, the
trap is coupled in series with the gas chromatographic
column, allowing the carrier gas to backflush the trapped
materials onto the analytical column. Just as valve 1 is
turned, the power is turned on to the resistance wire wrapped
around the trap. The power is supplied by an electronic
temperature controller. Using this device, the trap is
rapidly heated to 180°C with minimal temperature overshoot
and then maintained at 180°C. The trapped compounds are
released as a "slug" to the gas chromatograph by this heat
and backflush step. Normally, packed columns with theoreti-
cal efficiencies near 500 plates/foot under programmed
temperature conditions can accept such desorb injections
without altering peak geometry.
Substituting a non-controlled power supply, such as a
manually-operated variable transformer, will provide
non-reproducible retention times and poor quantitative data
unless the Injection Procedure in Section 8.4.2 is used.
After each sample has been injected into the gas chromato-
graph, the trap should be reconditioned. Condition the
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trap by turning valve 1 to the purge-sorb position and valve
2 to the dry position. Heat the trap to 180°C for 7
minutes (See Figure 6). Cool the trap to room temperature
and turn valve 2 to the purge position before analyzing the
next sample.
4.1.4 Several Purge and Trap devices are now commercially avail-
able. It is recommended that the following be taken into
consideration when purchasing a unit:
a. Compatibility with the gas chromatograph to be used for
the analysis.
b. Includes a 5-ml purging device similar to that shown in
Figure 1.
c. The Tenax portion of the trap must meet or exceed the
dimensions shown in Figure 2.
d. Except for sample introduction, select a unit that has as
many of the purge-trap functions automated as possible.
e. The trap-dry mode (valve 2) will likely need to be added
to commercial units.
4.2 Gas chromatograph - The gas chromatograph must be programmable and
capable of operating at 40°C ± 1°C. The gas chromatograph must
be equipped with automatic flow controllers so that the column flow
rate will remain constant throughout the program. It may be neces-
sary to cool the column oven to < 30°C. (See Section 8.4.2.)
Therefore, a subambient column controller may be required.
4.3 Gas chromatograph detector - A high temperature photoionization
detector of new design equipped with a 10.2 eV lamp is used as a
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semi-specific detector for those compounds described in Table 1.
The unit is operated with an electrometer/lamp power supply. The
electrometer must be capable of stable, noise-free operation at
-12
1 x 10 amps with a full scale response time of < 1 second.
The HNU Systems Inc., Model PI-52 photoionization and PI-52
electrometer/Iamp power supply equipped with a 10.2 eV lamp has
been found satisfactory for this purpose.
4.4 Gas Chromatographic Columns - Column 1 provides outstanding
separations for a wide variety of aromatic hydrocarbons. Column 1
should be used as the primary analytical column because of its
unique ability to resolve para, meta, and ortho aromatic isomers.
Column 2, an extremely high polarity column, has been used a number
of years for resolving aromatic hydrocarbons from alkanes in
complex samples. However, since the resolution between some of the
aromatics is not as efficient as Column 1, it is recommended that
Column 2 be used as a confirmatory column.
4.4.1 Column 1 - Six feet long x 0.082 inch ID #304 stainless
steel or glass tubing. Packed with 5% SP-1200 + 1.75%
Bentone 34 on 100/120 mesh Supelcoport. The carrier gas is
helium at a flow rate of 30 ml/minute. The temperature
program sequences are as follows: For lower boiling
compounds, operate at 50°C isothermal for 2 minutes then
program at 6°/minute to 90°C and hold until all
compounds have eluted. For a higher boiling range of
compounds, operate at 50°c isothermal for 2 minutes, then
program at 3°/minute to 110°C and hold until all
compounds have eluted.
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NOTE: In order to provide adequate resolution between the
aromatic hydrocarbons at a flow rate compatible with the
photoionization detector, it has been found that the 0.082
ID column is necessary. Variations in column ID and flow
rate will sacrifice resolution or sensitivity.
NOTE: Whenever column 1 is not being used, maintain it at
the upper temperature of the program, i.e. 90°C or
110°C. Condition new Bentone/SP-1200 columns at 120°C
for several days with flow before connecting to the detec-
tor. See Figures 7 and 8 for sample chromatograms.
4.4.2 Column 2 - Six feet long x 0.1 inch ID #304 stainless steel
or glass tubing packed with 5% 1,2,3-tris (2-cyanoethoxy)
propane on 60/80 mesh Chromosorb W-AW. The carrier gas is
helium at a flow rate of 30 ml/minute. The temperature
program sequence is as follows: 40°C isothermal for 2
minutes then 2°/minute to 100°C and hold until all
compounds have eluted. See Figure 9 for an example
chromatogram.
4.5 Sample containers - 40 ml screw-cap vials sealed with Teflon-faced
silicone septa.
Vials and caps - Pierce #13075 or equivalent
Septa - Pierce #12722 or equivalent
4.6 Syringes - 5-ml glass hypodermic with Luer-lok tip (2 each).
4.7 Micro syringes - 10, 100 ul.
4.8 Micro syringe - 25 yl with a 2" by 0.006 inch I.D. needle (Hamilton
#702N or equivalent).
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4.9 2-way syringe valve with Luer ends (3 each).
4.10 Modified 500 and 1000 ml volumetric flasks. See Figure 10.
5. Reagents and Materials
5.1 Trap Materials
5.1.1 Porous polymer packing 60/80 mesh chromatographic grade
Tenax GC (2,6-diphenylene oxide).
5.1.2 OV-1 (3%) on Chromosorb-W 60/80 mesh.
5.2 5% SP-1200/1.75% Bentone 34 on 100/120 mesh Supelcoport.
5.3 5% 1,2,3-tris (2-cyanoethoxy) propane on 60/80 mesh Chromosorb W-AW.
5.4 Dechlorinating compound-crystalline sodium thiosulfate, A.C.S.
Reagent Grade.
5.5 1:1 Hydrochloric Acid Solution in reagent water (must be shown to
be interference-free).
5.6 Activated carbon (for preparation of reagent water) - Filtrasorb-
200, available from Calgon Corp., Pittsburgh, PA, or equivalent.
5.7 Reagent water
5.7.1 Reagent water is defined as water free of interference when
employed in the purge and trap procedure described herein.
It is generated by passing tap water through a carbon filter
bed containing about 1 Ib. of activated carbon.
5.7.2 A Millipore Super-Q Water System or its equivalent may be
used to generate deionized reagent water.
5.7.3 Reagent water may also be prepared by boiling water for 15
minutes. Subsequently, while maintaining the temperture at
90°C, bubble a contaminant-free inert gas through the water
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for one hour. While still hot, transfer the water to a
narrow-mouth screw-cap bottle with a Teflon seal.
NOTE: Test reagent water daily by analyzing according to
paragraph 8.
5.8 Standards
5.8.1 Obtain 97% pure reagent grade reference standards.
5.9 Standard Stock Solutions.
NOTE: Because of the toxicity of some of the reference compounds,
it is necessary to prepare primary dilutions in a hood. It is
further recommended that a NIOSH/MESA approved toxic gas respirator
be used when the analyst handles high concentrations of such
materials.
5.9.1 Place about 9.8 ml of methyl alcohol into a 10 ml ground-
glass stoppered volumetric flask. Allow the flask to stand,
unstoppered, for about 10 minutes or until all alcohol-
wetted surfaces have dried and weigh to the nearest 0.1 mg.
5.9.2 Using a 100 yl syringe, immediately add 2 drops of the
reference standard to the flask, then reweigh. Be sure that
the 2 drops fall directly into the alcohol without contact-
ing the neck of the flask. Dilute to volume, stopper, then
mix by inverting the flask several times.
5.9.3 Calculate the concentration in micrograms per micro!iter
from the net gain in weight.
5.9.4 Transfer the standard solution to a 15 ml screw-cap bottle
with a Teflon cap liner.
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5.9.5 Store the solution at 4°C.
NOTE: Standard solutions prepared in methyl alcohol are
stable up to 4 weeks when stored under these conditions.
They should be discarded after that time has elapsed.
5.10 Calibration Standards
5.10.1 In order to prepare accurate aqueous standard solutions, the
following precautions must be observed.
a. Do not inject more than 20 ul of alcoholic standards into
100 ml of reagent water.
b. Use a 25 ul Hamilton 702N microsyringe or equivalent.
(Variations in needle geometry will adversely affect the
ability to deliver reproducible volumes of methanolic
standards into water.)
c. Rapidly inject the alcoholic standard into the expanded
area of the filled volumetric flask. See Figure 10.
Remove the needle as fast as possible after injection.
d. Mix aqueous standards by inverting the flask three times
only.
e. Discard the contents contained in the neck of the flask.
Fill the sample syringe from the standard solution con-
tained in the expanded area of the flask as directed in
Section 8.3.
f. Never use pipets to dilute or transfer samples or aqueous
standards.
g. Aqueous standards are not stable and should be discarded
after one hour unless preserved, stored, and sealed
according to 6.3 and 6.4.
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5.10.2 Prepare, from the standard stock solutions, secondary
dilution mixtures in methyl alcohol so that a 20 ul injec-
tion into 100, 500, or 1000 ml of reagent water will
generate a calibration standard which produces a response
close (±10%) to that of the unknowns.
5.10.3 Purge and analyze the aqueous calibration standards in the
same manner as the unknowns.
5.11 Quality Control Check Standard (0.40 ug/1)
5.11.1 From the standard stock solutions, prepare a secondary
dilution in methyl alcohol containing 10 ng/ul of each
compound normally monitored. NOTE: It may be necessary to
prepare two or more quality control check standards so that
all of the compounds in each mixture are adequately resolved
for quantitative measurement.
5.11.2 Daily, inject 20.0 yl of this mixture into 500 ml of reagent
water and analyze according to the Procedure Section 8.
6. Sample Collection and Handling
6.1 The sample containers should have a total volume in excess of 40 ml.
6.1.1 Narrow-mouth screw-cap bottles with the TFE fluorocarbon-
faced silicone septa cap liners are strongly recommended.
Crimp-seal serum vials with TFE fluorocarbon-faced septa are
acceptable if the seal is properly made and maintained
during shipment.
6.2 Sample Bottle Preparation
6.2.1 Wash all sample bottles and TFE seals in detergent. Rinse
with tap water and, finally, with distilled water.
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6.2.2 Allow the bottles and seals to air dry at room temperature,
place in a 105°C oven for one hour, then remove and allow
to cool in an area known to be free of organics.
NOTE: Do not heat the TFE seals for extended periods of
time (i.e., more than 1 hour) because the silicone layer
slowly degrades at 105°C.
6,2.3 When cool, seal the bottles with the TFE seals that will be
used for sealing the samples.
6.3 Sample Preservation - It has been found that non-sterile samples
containing aromatic hydrocarbons cannot be stored longer than 4
hours because of biological degradation. See Table 3. Samples can
be stabilized by adding free chlorine or by adjusting the pH to < 2
with 1:1 hydrochloric acid. See Table 4. Free chlorine will react
with styrene, and 2,3-benzofuran. Therefore, if these compounds
are to be determined in chlorinated water, it will be necessary to
dechlorinate the sample with sodium thiosulfate at the rate of 1
mg/ppm of free chlorine. Once dechlorinated, the sample pH must be
adjusted to < 2 with 1:1 hydrochloric acid. If chemical preserva-
tion is employed, the preservative is also added to the blanks.
See Tables 2, 3, and 4 for recommended maximum holding times.
6.4 Sample Collection
6.4.1 Collect a minimum of two replicates from each sample
source. Fill the sample bottles in such a manner that no
air bubbles pass through the sample as the bottle is being
filled. Seal the bottles so that no air bubbles are
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entrapped in it. Maintain the hermetic seal on the sample
bottle until time of analysis.
6.4.2 Sampling from a water tap.
6.4.2.1 Turn on water and allow the system to flush. When
the temperature of the water has stabilized, adjust
the flow to about 500 ml/minute and collect
duplicate samples from the flowing stream.
6.4.3 Sampling from an open body of water.
6.4.3.1 Fill a 1-quart wide-mouth bottle or 1-liter beaker
with sample from a representative area. Carefully
fill a minimum of two sample bottles from the
sampling container as noted in 6.4.1.
6.4.4 If sodium thiosulfate preservative has been added to the
sample bottles, then fill with sample just to overflowing,
add two drops of 1:1 HC1 then seal the bottle, and shake
vigorously for 1 minute.
6.4.5 Sealing practice for septum-seal screw-cap bottles.
6.4.5.1 Open the bottle and fill to overflowing, place on a
level surface, add 2 drops of 1:1 hydrochloric acid,
position the TFE side of the septum seal upon the
convex sample meniscus and seal the bottle by screw-
ing the cap on tightly.
6.4.5.2 Invert the sample and lightly tap the cap on a solid
surface. The absence of entrapped air indicates a
successful seal. If bubbles are present, open the
bottle, add a few additional drops of sample and
reseal bottle as above.
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NOTE: If the septum seals are inverted (ie. the
silicone side against the sample) then significant
losses will occur.
NOTE: Be sure that the addition of 2 drops of 1:1
HC1 will adjust the sample pH between 1 and 2.
Check all new sample sources by adding 2 drops of
1:1 HC1 to 40 ml of sample in a beaker. Measure the
pH with narrow range, (1.4 to 2.8), pH paper.
6.4.6 Blanks
6.4.6.1 Sample blanks must be prepared and accompany the
samples wherever the samples are shipped or stored.
If the samples are immediately analyzed near the
sampling site, blanks are not required. Prepare
blanks in replicate at the laboratory by filling and
sealing a minimum of two sample bottles with pre-
tested reagent water just prior to shipping the
sample bottles to the sampling site.
6.4.6.2 If the sample is to be preserved with sodium thio-
sulfate, add an identical amount of preservative to
the blanks. Ship the blanks to and from the
sampling site along with the sample bottles. Open
the blanks at the sample site, add 2 drops of 1:1
HC1, then reseal.
6.4.6.3 Store the blanks and the samples, collected from a
given source (sample set), together. A sample set
is defined as all the samples collected from a given
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source (i.e., at a water treatment plant, the repli-
cate raw source waters, the replicate finished
waters, and the replicate blank samples comprise the
sample set). Store the sample set in an area known
to be free of organic vapors. See Table 2 for
maximum storage time.
7. Conditioning Traps
7.1 Condition newly packed traps overnight at 200°C by backflushing
with an inert gas flow of at least 20 ml/min. Vent the trap
effluent to the room, not to the analytical column.
7.2 Prior to daily use, condition traps 10 minutes while backflushing
at 180°C. The trap may be vented to the analytical column;
however, after conditioning, the column must be programmed prior to
use.
8. Extraction and Analysis
8.1 Adjust the purge gas (nitrogen or helium) flow rate to 40 ml/min.
Attach the trap inlet to the purging device by turning valve 1 to
the purge-sorb position (Figure 3).
8.2 Open the syringe valve located on the purging device sample intro-
duction needle (Figure 1). Remove the plungers from two 5-ml
syringes and attach a closed syringe valve to each.
8.3 Open the sample bottle (or standard) and carefully pour the sample
into one of the syringe barrels until it overflows. Replace the
syringe plunger and compress the sample. Open the syringe valve
and vent any residual air while adjusting the sample volume to 5.0
ml. Close the valve. Fill the second syringe in an identical
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manner from the same sample bottle. This second syringe is
reserved for a replicate analysis, if necessary.
8.4 Attach the syringe-valve assembly to the syringe valve on the
purging device. Open the syringe valve and inject the sample into
the purging chamber. Close both valves. Purge the sample for 12.0
± .05 minutes. After the 12-minute purge time, turn valve 2
(Figure 4) to the dry position for 4 minutes. Empty the purging
device using the sample introduction syringe, follow with two 5-ml
flushes of reagent water. Leave the syringe valve open. After the
4-minute dry purge time, attach the trap to the chromatograph (turn
valve 1 to the desorb position, Figure 5) and introduce the trapped
materials to the GC column by rapidly heating the trap to 180°C
while backflushing the trap with an inert gas between 20 and 60
ml/min for 4 minutes.
8.4.1 If the trap can be rapidly heated to 180°C and maintained
at this temperature, the GC analysis can begin as the sample
is desorbed, i.e., the column is at the initial 50°C
operating temperature. Start the temperature program and
collect retention data just after valve 1 is turned. The
equipment described in Figures 3 through 6 will perform
accordingly.
8.4.2 With other types of equipment (see 4.1.4) where the trap is
not rapidly heated or is not heated in a reproducible
manner, it is necessary to transfer the contents of the trap
into the analytical column at 30°C where it is once again
trapped. Once the transfer is complete (4 minutes), the
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column is rapidly heated to the initial operating tempera-
ture for analysis. Start to collect retention data just as
the column is heated.
NOTE: In severe cases, it may be necessary to cool the
column down to 0°C.
8.4.3 If injection procedure 8.4.1 is used and the early eluting
peaks in the resulting chromatogram have poor geometry or
variable retention times, then method 8.4.2 should be used.
8.5 After desorbing the sample for four minutes, recondition the trap
by returning valve 1 to the sorb position. See Figure 6. Maintain
the trap temperature at 180°C. After approximately seven
minutes, return valve 2 to the purge position and turn off the trap
power. Leave the syringe valve open.
8.6 Treat and analyze each sample and sample blank from the sample set
in an identical manner (see 6.4.6.2) on the same day.
8.7 Prepare single point standards from the standard stock solutions
(5.11) in reagent water that are close to the unknown in composi-
tion and concentration (9.1). The concentrations should be such
that no more than 20 pi of the secondary dilution need be added to
100 to 1000 ml of reagent water to produce a standard at the same
level as the unknown.
8.8 As an alternative to single point calibration, Section 8.7, once
the stability of the entire system is established, construct a
calibration curve for each compound normally monitored over a
concentration range that will bracket each sample. Daily check the
validity of this calibration curve using the 0.4 ug/1 quality
control check sample. The value obtained must be within ± 0.08
ug/1. If it is not, generate a new calibration curve or use 8.7.
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9. Analytical Quality Control
9.1 Analyze the 0.40 ug/1 quality control check sample daily before any
samples are analyzed. Instrument status checks and lower limit of
detection estimations, based upon response factor calculations at
five times the noise level, are obtained from these data. In
addition, response factor data obtained from the 0.40 ug/1 quality
control check standard can be used to estimate the concentration of
the unknowns. From this information, the appropriate standard
dilutions can be determined.
9.2 Analyze the EMSL-Cincinnati volatile organics quality control
samples or their equivalent on a quarterly basis. The values must
be within 20% of the true value.
9.3 Analyze the sample blank or a method blank to monitor for potential
interferences as described in Sections 3.1, 3.2 and 3.4.
9.4 Daily perform the following instrument status checks, using the
data gathered from blanks, duplicate analyses, and the quality
check sample.
9.4.1 Peak Geometry Check
9.4.1.1 All of the peaks contained in the quality control
sample chromatogram must be sharp and symmetrical.
Peak tailing in excess of that shown in the method
chromatograms must be corrected. If only the com-
pounds eluting before ethylbenzene give random
responses, unusually wide peak widths, unstable
retention times, poor resolution, or are missing,
the problem is usually traceable to the trap/
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desorber. See Sections 4.1.4 and 8.4.2. If
negative peaks appear early in the chromatogram,
increase the dry purge time to 5 minutes. Retention
times for the compounds should remain constant (less
than 10% variance) throughout the day.
9.4.2 Check the precision between replicate analyses. A properly
operating instrument should perform with an average relative
standard deviation of less than 6% over a concentration
range of 0.1 to 100 ug/1. Poor precision is generally
traceable to:
a. Pneumatic leaks especially around the purging device,
trap, and column.
b. Too high lamp intensity power. Should adjust to about 50
to 60% for the 10.2 eV lamp.
9.4.3 The method blank analysis should represent less than a 0.1
ug/1 response or less than a 10% interference for those
compounds that occur routinely.
9.5 Any instrument not performing according to 9.4 specifications
should be considered "out of control." The system must be "in
control" before acceptable data can be generated.
10. Calculations
10.1 Determine the concentration of the unknowns by comparing the peak
height (area) of the unknowns to that of the standard peak height
(area) (8.7). Round off the result to the nearest .01 yg/1 or two
significant figures.
-------
peak height sample
= peak height standard x (concn' std>
10.2 Report the results obtained from the EMSL Quality Control
Sample and the lower limit of detection estimates along with
the data for the unknown samples.
10.3 Calculate the limit of detection (LOO) for each compound not
detected using the following criteria:
(A x ATT)
LOD(ug/D=0.4 (F77fF)
where: A = 5 times the noise level in (mm) at the exact
retention time of the compound or the baseline
displacement in (mm) from the theoretical zero at
the exact retention time of the compound.
11. Accuracy and Precision
11.1 Precision and Accuracy for Purge and Trap Method Using the Photo-
ionization Detector under the conditions described in Section 4.3.
11.1.1 Both Ohio River water and carbon-filtered tap water were
spiked with known amounts of selected compounds. The
spiked solutions were then sealed in septum-seal vials then
stored on the bench top for up to four weeks. Samples were
randomly analyzed on several occasions. Tables 2, 3, and 4
show the accuracy, precision, and maximum holding time data
obtained from this study.
-------
TABLE 1. RETENTION DATA
Column 1
Column 2 Lower Limit
Compound
Benzene
1,1,2-Trichloroethylene
a,-Trifluorotoluene
Toluene
1,1,2,2-Tetrachloroethylene
Ethyl benzene
1-Chlorocyclohexene-l
p-Xylene
Chlorobenzene
m-Xylene
o-Xylene
Iso-propylbenzene
Styrene
p-Bromofluorobenzene
n-Propyl benzene
tert-Buty 1 benzene
o-Chlorotoluene
p-Chlorotoluene
Bromobenzene
sec-Butyl benzene
1, 3, 5-Trimethyl benzene
p-Cymene
1,2,4-Trimethylbenzene
p-Di ch 1 orobenzene
m-Di Chlorobenzene
Cyclopropyl benzene
n-Butyl benzene
2,3-Benzofuran
o-D ichl orobenzene
Hexachlorobutadiene
1, 2, 4-Trichl orobenzene
Naphthalene
1,2,3-Trichlorobenzene
Program
A
199
223
275
340
360
491
518
518
542
542
574
595
544
664
681
786
804
804
804
829
851
909
909
999
1082
1082
1082
1283
1528
2035
2690
4280
4526
Program
B
199
231
296
384
406
606
637
653
689
689
738
768
834
852
879
975
985
990
999
1027
1043
1090
1090
1152
1211
1211
1211
1320
1425
1650
1928
2545
2631
165
142
168
255
168
375
345
403
481
403
518
455
690
740
518
595
681
—
807
595
612
681
750
975
901
...
765
1460
1161
1011
1535
2298
1820
of Detection
ug/l*
0.02
0.01
0.02
0.02
0.01
0.002
0.008
0.002
0.004
0.004
0.004
0.005
0.008
0.009
0.006
0.008
_ —
0.002
0.02
0.003
0.009
0.006
0.006
0.006
0.02
0.03
0.02
0.02
0.03
0.04
0.03
Column 1-6 Teet long x 3.082 ID stainless steel packed with 5%
SP-1200/1.75% Bentone 34 on 100/120 mesh Supelcoport.
Program A: 50° C hold 2 minutes, 6°/min to 90° C
Program B: 50° C hold 2 minutes, 3°/min to 110° C
Column 2-8 feet long x 0.10 inch ID stainless steel packed with 5%
1,2,3-Tris (2-Cyanoethoxy) propane on Chromosorb-W AW.
Program: 40° C hold 2 minutes, 2°/minute to 100° C.
*Lower limit of detection - 99% confidence that the value is not zero
calculated from 7 runs at 0.04 ug/l.
-------
Single Laboratory Accuracy and Precision for Aged Samples Containing Aromatic Compounds
and Selected Organohalides Spiked Into Chlorinated Drinking Water
Compound
Benzene
Trichloroethylene
a-Trichlorotoluene
Toluene
Tetrachloroethylene
Ethylbenzene
1-Chlorocyclohexene-l
p-Xylene
Chlorobenzene
m-Xylene
o-Xylene
iso-Propylbenzene
Styrene
p-Bromof luorobenzene
m-Propyl benzene
t-Butylbenzene
o-Chlorotoluene
p-Chlorotoluene
Bromobenzene
sec-Butylbenzene
1,3,5-Trimethylbenzene
p-Cymene
1,2,4-Trimethylbenzene
p-Dichlorobenzene
m-Di chlorobenzene
Cycloprepyl benzene
m-Butylbenzene
2,3-Dibenzofuran
o-Di chlorobenzene
Hexachlorobutadiene-1 ,
1 ,2,4-Trichlorobenzene
Naphthalene
1 ,2,3-Trichlorobenzene
Spike
Level
(yg/D
0.40
0.50
0.50
0.40
0.50
0.40
0.50
0.40
0.50
0.40
0.40
0.40
0.40
No data
0.40
0.40
No data
0.50
0.50
0.40
0.50
0.80
0.40
0.50
0.50
No data
0.40
0.40
0.50
3 0.50
0.50
0.50
0.50
Day 1
Recovery
~T£)
100
103
100
100
108
103
96
95
96
95
93
93
0.00
90
95
94
96
85
96
92
83
106
96
90
14
102
88
94
108
100
Samples
Analyzed3
7
10
9
7
10
7
10
7
10
7
7
7
7
7
7
8
10
7
10
5
7
10
10
7
7
9
10
10
8
10
-- ,- . .. y ,,.„-,— ..
Mean
Recovery
r£7~
100
104
89
93
104
93
91
85
96
90
90
88
0.00
83
88
93
93
80
92
88
75
100
92
78
0.0
92
74
88
96
85
Standard
Deviation
0.082
0.037
0.048
0.022
0.040
0.032
0.029
0.029
0.029
0.028
0.026
0.030
0.030
0.030
.022
.030
0.034
0.040
0.012
0.029
0.029
0.040
0.049
-
0.033
0.062
0.047
0.062
0.046
Relative
Standard
Deviation
(%)
2.1
7.0
11.0
5.7
7.7
8.5
6.4
8.7
6.1
7.7
7.2
8.7
9.3
8.7
4.9
6.4
11. 0
8.7
2.8
8.7
8.7
8.7
16
-
7.1
17
11
13
11
Length
of
Study
T3ays)
15
28
28
15
28
15
28
15
28
15
15
15
0*
15
15
13*
28
15
28
6*
15
28
28
15
0*
28
28
28
20*
28
^f UMII1-' | *•> .J I MlfVJVSIIICr V*liV»l^fc*-»« w » « • -w M j . • •
*Maximum recommended holding time.
-------
TABLE 3
Single Laboratory Accuracy and Precision for Aged Samples Containing Aromatic Compounds
and Selected Organohalides Spiked Into Ohio River Water
Compound
Benzene
Trichloroethylene
a-Trichlorotoluene
Toluene
Tetrachloroethylene
Ethylbenzene
1-Chlorocyclohexene-l
p-Xylene
Chlorobenzene
m-Xylene
o-Xylene
iso-Propylbenzene
Styrene
p-Bromof luorobenzene No
m-Propylbenzene
t-Butylbenzene
o-Chlorotoluene No
p-Chlorotoluene
Bromobenzene
sec-Butylbenzene
1 ,3,5-Trimethylbenzene
p-Cyrnene
1,2,4-Trimethylbenzene
p-Di chlorobenzene
m-Dichlorobenzene
Cyclopropy Ibenzene No
n-Butylbenzene
2,3-Dibenzofuran
o-Dichlorobenzene
Hexachlorobutadiene-1,3
1,2,4-Trichlorobenzene
Naphthalene
1 ,2,3-Trichlorobenzene
Spike
Level
(ygTTT
0.40
0.50
0.50
0.40
0.50
0.40
0.50
0.40
0.50
0.40
0.40
0.40
0.40
data
0.40
0.40
data
0.50
0.50
0.40
0.50
0.50
0.40
0.50
0.50
data
0.40
0.40
0.50
0.50
0.50
0.50
0.50
Day 1
Recovery
~T*1
12
86
74
8
85
10
86
12
23
17
12
0.0
0.0
15
43
45
17
10
16
34
5
90
96
3
0.0
.85
84
88
38
97
Samples
Analyzed3
6
6
6
6
6
6
5
6
6
6
5
Mean
Recovery
(%)
87
87
83
86
87
88
88
77
88
42
91
Standard
Deviation
0.015
0.081
0.014
0.034
0.048
0.036
0.53
0.099
0.072
.20
.070
Relative
Standard
Deviation
(%)
3.5
23.
3.3
7.8
10.9
8.3
12
26
16
98
15
Length
of
Study
(days)
18
18
18
18
18
18
18
18
18
18
4
randomTv analyzed tnrouonout tne studv oeriod.
-------
Single Laboratory Accuracy and Precision for Aged Samples Containing Aromatic Compounds
and Selected Organohalides Spiked Into Ohio River Water
Compound
Benzene
Trichloroethylene
a-Trichlorotoluene
Toluene
Tetrachloroethylene
Ethylbenzene
1-Chlorocyclohexene-l
p-Xylene
Chlorobenzene
m-Xylene
o-Xylene
iso-Propyl benzene
Styrene
p-Bromof luorobenzene
m-Propylbenzene
t-Butylbenzene
o-Chlorotoluene
p-Chlorotoluene
Bromobenzene
sec-Butylbenzene
1,3,5-Trimethylbenzene
p-Cymene
1,2,4-Trimethylbenzene
p-Di chlorobenzene
m-Di chlorobenzene
Cycloprepyl benzene
n-Butylbenzene
2,3-Dibenzofuran
o-Dichlorobenzene
Hexachlorobutadiene-1,3
1,2,4-Trichlorobenzene
Naphthalene
1,2,3-Trichlorobenzene
Spike
Level
WT)
0.40
0.50
0.50
0.40
0.50
0.40
0.50
0.40
0.50
0.40
0.40
0.40
0.40
No data
0.40
0.40
No data
0.50
0.50
0.40
0.50
0.50
0.40
0.50
0.50
No data
0.40
0.40
0.50
0.50
0.50
0.50
0.50
Day 1
Recovery
"OH
100
104
84
98
100
95a
82
88 a
90
93a
95a
93a
83a
88a
90a
90
90
88 a
88
88
85a
94
96
85a
95a
96
82
88
82
86
Samples
Analyzed**
6
9
9
6
9
9
9
9
9
9
9
9
8
8
8
Mean
Recovery
~W
100
89
86
95
90
86
95
90
92
90
89
92
83
87
85
Standard
Deviation
0.014
0.028
0.037
0.028
0.035
0.034
0.027
0.023
0.027
0.032
0.037
0.033
0.038
0.075
0.042
Relative
Standard
Deviation
(%)
3.5
5.8
8.2
7.6
7.6
7.9
5.8
5.1
5.8
7.2
8.4
7.1
9.1
17.
10.
Length
of
Study
(days)
14
26
26
14
26
14
26
26
14
14
14
14
14
14
26
26
14
14
14
14
26
26
14
14
26
26
26
26
26
Average
Decay Rate
(%/day)
1.4
2.3
1.6
1.6
1.5
4.2
2.2
10
2.2
2.1
2.3
3.0
3.2
2.4
3.2
aSample 2 days old.
bSamples randomly analyzed throughout the study period.
-------
OPTIONAL
FOAM TRAP
1 4 IN. O.O. EXIT
10MM. GLASS FRIT
MEDIUM POROSITY
- EXIT 1/4
IN. O.D.
— I4MM. O.D.
INLET 1/4
IN. O.D.
SAMPLE INLET
2-WAY SYRINGE VALVE
• 17CM. 20 GAUGE SYRINGE NEEDLE
6MM.O.O. RUBBER SEPTUM
10MM. O.O.
INLET
1/4 IN. O.D.
1/16 IN. O.D.
STAINLESS STEEL
Tf
13X MOLECULAR
SIEVE PURGE
GAS RLTER
PURGE GAS
FLOW CONTROL
FIGURE 1. PURGING DEVICE
-------
PACKING PROCEDURE
CONSTRUCTION
GLASS WOOL 5MM
TENAX
23CM
3% OV-1 KM
GLASS WOOL
5MM
COMPRESSION FITTING NUT
AND FERRULES
MFT. 7-VFOOT RESISTANCE
WIRE WRAPPED SOLID
THERMOCOUPLE/CONTROLLER
SENSOR
ELECTRONIC
TEMPERATURE
CONTROL
AND
PYROMETER
TUBING 25CM 0.105 IN. I.D.
0.175 IK O.D. STAINLESS STEEL
TRAP INLET
FIGURE 2 TRAP
-------
CARRIER GAS FLOW CONTROL
PRESSURE REGULATOR
LIQUID INJECTION PORTS
PURGE GAS
FLOW CONTROL \
13X MOLECULAR
SIEVE FILTER
VALVE-3
OPTIONAL 4-PORT COLUMN
SELECTION VALVE
TRAP INLET(TENAX END)
VALVE-1 / RESISTANCE WIRE
TRAP
22°C
COLUMN OVEN
CONFIRMATORY COLUMN
TO DETECTOR
ANALYTICAL COLUMN
HEATER CONTROL
VALVE-2
NOTE: ALL LINES BETWEEN
TRAP AND GC
SHOULD BE HEATED
TO 80°C
FIGURE 3 PURGE-TRAP SYSTEM (PURGE-SORB MODE)
-------
CARRIER GAS FLOW CONTROL
PRESSURE REGULATOR
LIQUID INJECTION PORTS
PURGE GAS
FLOW CONTROL \
13X MOLECULAR
SIEVE FILTER
COLUMN OVEN
CONFIRMATORY COLUMN
TO DETECTOR
ANALYTICAL COLUMN
VALVE-3
OPTIONAL 4-PORT COLUMN
SELECTION VALVE
TRAP INLET (TENAX END)
VALVE-1 / x RESISTANCE WIRE
HEATER CONTROL
NOTE: ALL LINES BETWEEN
TRAP AND GC
SHOULD BE HEATED
TO 80°C
I
•i
VALVE-2
FIGURE 4 PURGE-TRAP SYSTEM (TRAP-DRY MODE)
-------
CARRIER GAS FLOW CONTROL
PRESSURE REGULATOR
LIQUID INJECTION PORTS
PURGE GAS
FLOW CONTROL
13X MOLECULAR
SIEVE FILTER
COLUMN OVEN
CONFIRMATORY COLUMN
TO DETECTOR
ANALYTICAL COLUMN
VALVE-3
OPTIONAL 4-PORT COLUMN
SELECTION VALVE
TRAP INLET (TENAX END)
RESISTANCE WIRE
HEATER CONTROL
NOTE: ALL LINES BETWEEN
TRAP AND GC
SHOULD BE HEATED
TO 80° C
VALVE-2
FIGURE 5 PURGE-TRAP SYSTEM (DESORB MODE)
-------
CARRIER GAS FLOW CONTROL
PRESSURE REGULATOR
LIQUID INJECTION PORTS
PURGE GAS
FLOW CONTROL \
13X MOLECULAR
SIEVE FILTER
VALVE-3
OPTIONAL 4-PORT COLUMN
SELECTION VALVE
TRAP INLET (TENAX END)
VALVE-1 / RESISTANCE WIRE
PURGING
DEVICE
TRAP
FLOW
TRAP
180°C
COLUMN OVEN
CONFIRMATORY COLUMN
TO DETECTOR
ANALYTICAL COLUMN
HEATER CONTROL
VALVE-2
NOTE: ALL LINES BETWEEN
TRAP AND GC
SHOULD BE HEATED
TO 80°C
FIGURE 6 PURGE-TRAP SYSTEM (TRAP-CONDITION MODE)
-------
_- fc -.tfc—,
FULL SCALE RESPONSE 16*10^ AMPS
C
3J
m
O
z
a
o
2
>
o
o
O
•n
m
tn
X
H
as
m
1.1,2-TRICHLOROETHYLENE
o-TRIFLUOROTOLUENE
1,1,2,2-TETR ACHLOROETHYLENE
CHLOROBEN2ENE
o^CHLORQTOLUENE
BROMOBENZENE
1,3,5-TRIMETHYLBENZENE
P-DICHLOROBEN2ENE
m-DICHLOROBENZENE
o-DICHLOROBENZENE
1 -CHLOROCYCLOHEXENE
HEXACHLOROBUTADIENE-i ,3
1,2.4-TRICHLOROBENZENE
NAPHTHALENE
1.2.3-TRICHLOROBEN2ENE
ISIS
3) S
m e
s*
0
n
-------
COLUMN: 5% SP-1200/1.76% BENTONE 34
PROGRAM: 60°C - 2 MINUTES 6°C/min. to 90°C
DETECTOR: PHOTOIONIZATION
SAMPLE: 0.40/ig/l STANDARD MIXTURE
(A
Z
8i|
Si
«0
D
u.
20
22
RETENTION TIME, minutes
FIGURE 8. CHROMATOGRAM OF TEST MIXTURE
•i
-------
COLUMN: 5% 1.2.3-TRIS (2-CYANOETHOXY)
PROPANE ON CHROMOSORB—W
PROGRAM: 40°C-2minutes 2°C/min. to 100°C
DETECTOR: PHOTOIONIZATION
SAMPLE: 2.0 Mg/l STANDARD MIXTURE
8 12
RENTENTION TIME,minutes
FIGURE 9. CHROMATOGRAM OF TEST MIXTURE
-------
6MM O.D HALF-HOLE
CYLINDRICAL SEPTUM
8MM O.D TUBING
9MM. LONG
FIGURE 10. MODIFIED VOLUMETRIC FLASK
«-. —it,-?! Protection Agency
------- |