United States Atmospheric Research and

Environmental Protection Exposure Assessment Laboratory

Agency Research Triangle Park, NC 27711

E AP Project Summary

Field Test of a Generic

Method for Halogenated

Hydrocarbons: A VOST Test at a

Chemical Manufacturing Facility

Using a Modified VOST

Sampling Method

Research and Development EPA/600/SR-94/130 May 1995

Because of the lack of commercial

availability of SKC Lot 104 petroleumbased charcoal, the lot of charcoal

specified for use in the Volatile Organic Sampling Train (VOST, SW-846

Method 0030), a laboratory study was

performed to select an appropriate substitute. On the basis of performance,

availability, and cost, Anasorb 747®*

was selected as the substitute for SKC

Lot 104, and a draft sampling protocol

for the modified VOST train was written. In the modified VOST sampling

train, the second tube containing sequential beds of Tenax® and charcoal

was replaced by a tube containing only

Anasorb®. This replacement necessitated the use of two Tenax® front tubes

in the train, for a total of three sorbent

tubes. A field evaluation study, using

dynamic spiking and quadruple sampling trains, was conducted to provide

a statistical comparison of the performance of the VOST and the modified

VOST methodologies for the volatile

halogenated organic compounds listed

in Title III of the Clean Air Act Amendments of 1990.

This Project Summary was developed

by EPA’s Atmospheric Research and

Exposure Assessment Laboratory, Research Triangle Park, NC, to announce

key findings of the research project

that is fully documented in a separate

report of the same title (see Project

Report ordering information at back).

Introduction

Validation of a method for a particular

analyte or group of analytes means that

the performance of the methodology for

these analytes has been established and

demonstrated through field tests at the

type of source category of interest: that is,

the precision and bias of the method have

been established experimentally. Field validation may be performed by performing

spiking operations in the field so that the

precision and bias of the method can be

demonstrated from sample collection

through analysis, using either static or dynamic spiking procedures as specified in

EPA Method 301, the Validation Protocol.

Another procedure for validation of a

method is a side-by-side comparison of a

candidate method to a validated method

to establish comparable performance for

the same analytes in the same matrix

(same source category).

James F. McGaughey, Joan T. Bursey, and Raymond G. Merrill

_________________________

* Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
2

Under Title III of the Clean Air Act

Amendments of 1990, identification and/

or validation of sampling and analytical

methods are required for the volatile halogenated organic compounds which are

listed (Table 1). The candidate test method

is the Volatile Organic Sampling Train

(VOST), which consists of SW-846 Sampling Method 0030 and SW-846 Analytical

Method 5040 or 5041. Method 0030, the

sampling protocol, requires the use of

Tenax® and a specific petroleum-based

charcoal (SKC Lot 104) or its equivalent.

Since SKC Lot 104 charcoal is no longer

commercially available and Method 0030

contains no performance specifications for

the charcoal, a laboratory study was performed to identify an acceptable equivalent. Several candidate sorbents were studied in the laboratory, and Anasorb 747®

was selected as a candidate sorbent for a

field test because of its performance, availability, and cost. In the course of the laboratory studies, the decision was made to

use only Anasorb® in the back tube rather

than the sequential beds of Tenax® and

charcoal which had been used previously.

Use of a back tube consisting of only

Anasorb® necessitated the use of two

Tenax® front tubes in a modified VOST

train. A new sampling protocol was written to incorporate the use of the modified

sorbent tube structure. The analytical procedures of Method 5041 were also modified to include individual analysis of each

of the three sorbent tubes to examine

compound distribution. In routine application, the analysis would be performed with

paired Tenax® tubes.

A presurvey conducted at a chemical

manufacturing facility established that no

compounds of interest were present above

a level of 5 times the Method Detection

Limit. Evaluation of the modified VOST

method was accomplished by performing

sampling and analysis following Draft

Method 0031 and Method 5041, using

Method 0030 as the reference method required by EPA Method 301. The bias of

the method can be evaluated by comparing the results obtained by one candidate

method to the results obtained by a validated method. To determine the precision

of the test method, multiple or collocated

Table 1. Volatile Halogenated Organic Compounds, Title III of the Clean Air Act Amendments, for Which Laboratory Testing has Determined the

Applicability of the VOST Method

Boiling

point

Compound (°C) Comments ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

allyl chloride (3-chloropropene) 44-46 Acceptable performance in laboratory

bis(chloromethyl) ether 1061 Decomposes in water; cannot be analyzed

carbon tetrachloride 77 Recovery too high in laboratory study

chlorobenzene 1321 Acceptable performance in laboratory

chloroform 60.5-61.5 Acceptable performance in laboratory

chloromethyl methyl ether 55-57 Decomposes in water; cannot be analyzed

chloroprene 59.4 Acceptable performance in laboratory

1,3-dichloropropylene 105-1062 Acceptable performance in laboratory

epichlorohydrin 115-117 1 Soluble in water; cannot be analyzed

ethyl chloride (chloroethane) 123 Acceptable performance in laboratory

ethylene dibromide (1,2-dibromoethane) 131-1321 Acceptable performance in laboratory

ethylene dichloride (1,2-dichloroethane) 83 Acceptable performance in laboratory

ethylidene dichloride (1,1-dichloroethylene) 57 Acceptable performance in laboratory

methyl bromide (bromomethane) 43 Recovery unacceptably high in laboratory

methyl chloride (chloromethane) -24.2 3 Erratic and unacceptably high recovery in laboratory

methyl chloroform (1,1,1-trichloroethane) 74-76 Recovery too high in laboratory study

methylene chloride 39.8-40 Recovery too high in laboratory study

methyl iodide (iodomethane) 41-43 Acceptable performance in laboratory

propylene dichloride (1,2-dichloropropane) 95-96 Acceptable performance in laboratory

tetrachloroethylene 1211 Acceptable performance in laboratory

1,1,2-trichloroethane 110-1151 Acceptable performance in laboratory

trichloroethylene 86.9 Acceptable performance in laboratory

vinyl chloride -13.43 Acceptable performance in laboratory

vinyl bromide (1,1-dichloroethene) 164 Acceptable performance in laboratory

vinylidene chloride 30-32 Acceptable performance in laboratory

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

1 Above the maximum VOST boiling point of 100°C; included in the testing because compounds in the range of 100-132°C are frequently tested by the VOST

method.

2 Boiling temperature at 730 mm Hg.

3 Below the common lower temperature limit of 30°C usually used for VOST. 4 Boiling temperature at 750 mm Hg.
3

simultaneous samples are taken and analyzed. In this field test, known concentrations of volatile halogenated analytes were

introduced into the VOST trains and into

the modified VOST trains, using the same

certified cylinder as a source of the compounds. Using the same dynamic spiking

procedures, multiple collocated simultaneous samples were taken using both

methods at the same source.

Bias is any systematic positive or negative difference between the measured values and the true value of a sample. Bias

may result from analytical interferences,

errors in calibration, or inefficiencies in

the collection of the analyte. When the

bias of the method is determined for a

given analyte, a correction for the bias

may be made. The EPA Method 301 allows for this correction within a range of

90-110% when a candidate method is being compared to a reference method. Bias

values outside this range may be grounds

for rejecting the candidate method.

Precision is the variability in the data

from the entire measurement system (both

sampling and analysis) as determined from

multiple or collocated sampling trains. Following the EPA Method 301 procedures,

two paired sampling trains are used to

determine the precision of the entire system. Use of quadruple (Quad) trains with

four collocated sampling probes allows

operation of two spiked trains and two

unspiked trains. The EPA Method 301 requires that the precision of the candidate

method not be significantly different from

the reference method in order for the candidate method to be considered acceptable. To determine bias and precision in

the field, a total of at least 16 samples

using quadruple collocated sampling trains

was collected using both VOST and modified VOST.

Statistical analysis of the results from

the field studies with dynamic spiking show

that the two methods are at least equivalent, with the modified VOST methodology frequently being somewhat superior

in compound recovery and precision.

Procedure

Sampling was performed by withdrawing stack gas from a single port in the

stack through a Quad probe, then directing the sampled gas simultaneously to

four similar VOST or modified VOST sampling trains. The Quad probe contains four

similar heated probes that can be inserted

into the stack as one unit. The front end

of the Quad probe was positioned in the

center of the stack and remained in that

location during each day of testing; no

traverse of the stack was performed with

the Quad probe. The true concentration

of the components of the stack gas was

of no interest to this program as long as

any quantities of the compounds of interest were equal for each train, so traversing was not required. For modified VOST

sampling, two of the trains of each Quad

run were dynamically spiked (Trains A

and B) and two were unspiked (Trains C

and D). The configuration of the modified

VOST sampling train is shown in Figure 1.

Dynamic spiking of candidate VOST

compounds into the modified VOST train

Stack

Dry gas

meter

To bubble

Spiking gas In flow meter

Condensers

Charcoal

trap

Heated glass

lined probe

Tenax

Condensate

trap

Silica

gel

Vacuum

gauge

Temperature

indicators

Pump Rotameter

Glass

wool

filter

Three way

glass/teflon

valve

1/8" O.D.

Teflon line

Anasorb

Sampling Module

Meter Box

Exhaust

Condenser

ice bath

1/4" Teflon

tube

Tenax

Three way

glass/teflon

valve

Figure 1. Modified VOST sampling train.

Spiking gas in

Meter box

Sampling module
4

was performed using a compressed gas

cylinder containing the volatile halogenated

organic compounds. The same cylinder

was used for spiking both the VOST train

and the modified VOST train, with the

composition and concentration of the volatile halogenated organic compounds in the

cylinder established by independent laboratory tests. The boiling point of 100°C

cited in Method 0030 was extended to

approximately 135°C to allow the inclusion of chlorobenzene, a compound frequently determined by the VOST methodology. The Modified VOST spiking apparatus shown in Figure 2, was used for

dynamic spiking. In the field, the spiking

gas was allowed to flow through the spiking apparatus for two hours before directing the flow to the sampling trains to minimize any adsorptive losses during actual

Quad sampling runs. A total of ten (10)

Quad sampling runs for both VOST and

modified VOST was performed in the field

to provide adequate samples for statistical comparison of the two methods and to

allow backup samples in the event that

any samples became invalid due to breakage or loss of data during analysis.

Analysis of field samples was performed

according to SW-846 Method 5041

(VOST), analyzing each tube individually

to establish distribution of compounds. The

three tubes associated with each modified

VOST sample set were analyzed in the

following order: Anasorb®, Tenax® #2,

Tenax® #1. No condensate was observed

in the collection of samples.

Results and Discussion

Mean recoveries of the volatile halogenated organic compounds using the modified VOST sampling method are shown in

Table 2. No background corrections were

made because background levels of the

analytes were less than 5 times the Method

Detection Limit. Methyl chloride exhibited

erratic recoveries, far above 100% in most

analyses. This erratic behavior upon analysis had been observed in laboratory studies, in the first field test of the VOST

method, and in this field test of both the

VOST and modified VOST methods. The

compound is apparently being formed during sampling and analysis.

Surrogate compound recoveries from

the Tenax® tubes were uniformly high, so

correction for surrogate recoveries was

not made. The same surrogate compounds

were used to spike the Anasorb® tubes

prior to analysis, and recovery of the less

volatile surrogate compounds from

Anasorb® is poor; correction of Anasorb®

results for surrogate recovery would distort the analytical results.

Examination of the observed distribution

of analytes among the three sorbent tubes

of the modified VOST sampling train demonstrates the necessity of a second Tenax®

tube in the sampling train. Methyl chloride,

vinyl chloride, and ethyl chloride are found

primarily on the back (Anasorb®) tube. The

following compounds are found primarily

(>90%) on the front Tenax® tube: ethylidene

dichloride, chlorobenzene, chloroform, propylene dichloride, methyl chloroform, carbon tetrachloride, ethylene dichloride, trichloroethene, cis-1,3-dichloropropene,

trans-1,3-dichloropropene, 1,1,2-trichloroFigure 2. Modified VOST spiking apparatus.

250°C

Temperature

display

Variable transformers Thermocouple selector (to provide temperature control)

Certified

standard

(spiking

compounds)

Regulator

(temperature controlled)

To Train A To Train B

Chassis (temperature controlled)

1/4" teflon line

(heat traced and

insulated)

Fine metering

valves

(flow control)
5

ethane, tetrachloroethene, methyl iodide,

allyl chloride, ethylene dibromide, and chloroprene. Other analytes were distributed

among the three tubes.

Comparative results for the VOST and

modified VOST are shown in Table 3. In

most instances, recovery for modified

VOST is equivalent to or better than recovery for VOST, and precision for modified VOST is equivalent to or better than

precision for VOST.

Conclusions and

Recommendations

Based on the field evaluation of the

modified VOST method as compared to

the VOST method, the following conclusions may be drawn:

• On the basis of a compound-by-compound comparison of recovery and

precision, the two methods are comparable and, where they differ, the

modified VOST usually shows better

performance with respect to both recovery and precision.

• The only compound which showed

acceptable performance in the VOST

but not in the modified VOST is methyl bromide. However, the range in

both the recovery and precision is

sufficiently large that the differences

between the results for the VOST and

the modified VOST cannot be considered statistically significant.

• Methyl chloride (chloromethane) has

shown erratic performance, with extremely high recoveries and poor precision in several laboratory studies, in

two field tests using VOST, and in

the field test using the modified VOST

methodology. Methyl chloride is not

an appropriate analyte for any form

of the VOST method because quantitative calculations are unreliable for

this analyte. Even qualitative information (i.e., presence or absence) is suspect because methyl chloride may be

formed on the sorbent tubes from decomposition of other halogenated compounds.

• The following compounds were not

sampled and analyzed successfully in

this field evaluation using either VOST

or modified VOST: methyl chloride

(chloromethane), vinyl chloride, ethyl

chloride (chloroethane), allyl chloride

(3-chloropropene), and vinyl bromide.

Other than methyl chloride, all of the

analytes which show poor performance contain a double bond. Application of VOST or modified VOST

methodology for accurate quantitative

determination of analytes containing

Table 2. Mean Recoveries of Volatile Halogenated Organic Compounds, Using the Modified VOST Method

Percent

Mean Relative

Recovery Standard

Compound (Percent)1 Deviation ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

methyl chloride (chloromethane) 167.5 56.4

1,2-dichloropropane (propylene chloride) 149.4 14.0

trichloroethene 148.7 3.4

methylene chloride 120.7 10.9

cis-1,3-dichloropropene 118.4 21.0

1,1,2-trichloroethane 117.3 20.5

ethylene dibromide (1,2-dibromoethane) 108.5 23.2

chloroform 98.4 20.4

vinylidene chloride (1,1-dichloroethene) 96.8 17.2

ethylidene chloride (1,1-dichloroethane) 96.2 12.6

chlorobenzene 91.6 13.0

carbon tetrachloride 89.3 12.5

methyl iodide (iodomethane) 89.0 11.9

methyl chloroform (1,1,1-trichloroethane) 87.1 12.1

chloroprene 85.8 15.3

ethylene dichloride (1,2-dichloroethane) 83.2 25.1

trans-1,3-dichloropropene 75.2 32.6

tetrachloroethene 61.8 8.9

methyl bromide (bromomethane) 45.7 46.7

ethyl chloride (chloroethane) 45.3 30.0

vinyl chloride 44.2 24.2

vinyl bromide 38.0 22.5

allyl chloride (3-chloropropene) 26.0 21.1

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

1 The shaded area indicates recoveries from 50 to 150 percent with percent relative standard deviation of 50 or less.
6

a double bond is questionable. Because recoveries of these analytes

tend to be low, there tends to be a

low bias in the quantitative determination.

On the basis of the laboratory and field

efforts conducted for the volatile halogenated organic compounds from Title III of

the Clean Air Act Amendments, the following recommendations are made:

• Careful consideration of the chemical

and physical properties of candidate

VOST or modified VOST analytes can

predict when successful performance

of the sampling or analytical methodology is unlikely. For example, analysis of water-soluble compounds will

either be completely unsuccessful

or show a low bias, because

water-soluble compounds cannot be

quantitatively purged from water in

the course of the analysis.

• Neither the VOST nor the Modified

VOST is recommended as a sampling or analytical method for methyl

chloride (chloromethane). Even the

accuracy of VOST or modified VOST

as a screening method to establish

the presence of methyl chloride in an

emissions matrix is questionable.

• Modification or replacement of the

VOST methodology should be investigated to provide a sampling and analytical method feasible for application

to volatile, polar, water-soluble analytes.

• If surrogate compound recoveries are

90% or above, no corrections for surrogate recoveries should be made in

either VOST or modified VOST.

Table 3. Results of VOST and Modified VOST: Recovery and Precision

Modified VOST VOST

Percent Percent

Mean Relative Mean Relative

Percent Standard Percent Standard

Compound Recovery1 Deviation Recovery1 Deviation ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

methyl chloride (chloromethane) 167.5 56.4 255.3 58.1

ethylidene dichloride (1,1-dichloroethane) 96.2 2 12.6 86.0 2 13.2

chlorobenzene 91.62 13.0 84.8 2 27.9

vinyl chloride 44.2 24.2 37.3 39.5

vinylidene chloride (1,1-dichloroethene) 96.8 2 17.2 77.8 2 25.1

chloroform 98.4 2 20.4 95.3 2 14.3

propylene dichloride (1,2-dichloropropane) 149.4 2 14.0 117.7 2 30.0

methyl bromide (bromomethane) 45.7 46.7 52.8 2 27.8

ethyl chloride (chloroethane) 45.3 30.0 31.4 37.6

methylene chloride 120.7 2 10.9 90.8 2 11.7

methyl chloroform (1,1,1-trichloroethane) 87.1 2 12.1 96.8 2 19.4

carbon tetrachloride 89.3 2 12.5 85.7 2 13.8

ethylene dichloride (1,2-dichloroethane) 83.2 2 25.1 78.6 2 27.7

trichloroethene 148.7 2 3.4 124.0 2 16.8

cis-1,3-dichloropropene 118.4 2 21.0 83.5 2 16.1

trans-1,3-dichloropropene 75.22 32.6 47.9 35.0

1,1,2-trichloroethane 117.3 2 20.5 81.4 2 14.4

tetrachloroethene 61.8 2 8.0 57.5 2 12.5

methyl iodide (iodomethane) 89.02 11.9 77.8 2 20.4

allyl chloride (3-chloropropene) 26.0 21.1 36.4 29.6

ethylene dibromide (1,2-dibromoethane) 108.5 2 23.2 81.6 2 31.0

chloroprene 85.8 2 15.3 76.4 2 12.3

vinyl bromide 38.0 22.5 28.4 30.9

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

1 Mean of 6 runs (12 sets of dynamically spiked tubes).

2 Indicates acceptable performance, using the criteria of recovery from 50 to 150 percent, with percent relative standard deviation of 50 or less.
7

• •

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

EPA/600/SR-94/130

Official Business

Penalty for Private Use $300

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

James F. McGaughey, Joan T. Bursey, and Raymond G. Merrill are with Radian

Corporation, Research Triangle Park, NC 27709.

Merrill D. Jackson is the EPA Project Officer (see below).

The complete report, entitled “Field Test of a Generic Method for Halogenated

Hydrocarbons: A VOST Test at a Chemical Manufacturing Facility Using a

Modified VOST Sampling Method,” (Order No. PB95-142055; Cost: $27.00;

subject to change) will be available only from

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Telephone: 703-487-4650

The EPA Project Officer can be contacted at

Atmospheric Research and Exposure Assessment Laboratory

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711