United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S8-84-007 Apr. 1984
SEPA Project Summary
Protocol for the Collection and
Analysis of Volatile POHCs
Using VOST
Earl M. Hansen
This document provides a state-of-
the-art operating protocol for sampling
and analysis of volatile organic constit-
uents of flue gas from hazardous waste
incinerators or other similar combustor
systems using the Volatile Organic
Sampling Train (VOST). It is intended to
be used for guidance by personnel of
the regulatory groups, personnel asso-
ciated with engineering R&D. and the
regulated community.
The VOST is designed to extract and
concentrate volatile organic com-
pounds (boiling point < 100°C) from
stack gas effluents. The concentrated
organics are analyzed by procedures
chosen to be compatible with the VOST
in order to obtain flue gas concentration
levels. This information is necessary to
perform destruction and removal effi-
ciency (ORE) calculations for incin-
erator operations. The results of labo-
ratory evaluation and field use of the
VOST have shown that the VOST pro-
vides sufficient sensitivity to permit
calculation of a DRE equal to or greater
than 99.99 percent for volatile organics
present in the waste feed at 100/u g/g.
The VOST is directly applicable to
organic compounds with boiling points
of 30°C to 100°C. Many organic com-
pounds with boiling points less than
30°C or with boiling points in the
100°C to 150°C range may also be
collected and analyzed by this method.
Field application of the VOST for com-
pounds with boiling points outside the
30°C-100°C range should be attempt-
ed only after laboratory evaluation of
the collection and recovery efficiencies
of the specific compounds.
The document is presented in two
parts. Part A describes the key compo-
nents of the train, the procedures for
preparation of the sorbent materials,
and procedures for sample collection
using the VOST. Part B describes the
procedures for analysis of VOST sorbent
cartridges for volatile principal organic
hazardous constituents (POHCs) using
purge-trap-desorb gas chromatogra-
phy/mass spectrometry (P-T-D GC/
MS). Quality control procedures are
presented in both Sections A and B.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Summary
The Resource Conservation and Re-
covery Act (RCRA) requires that own-
ers/operators of facilities which treat
hazardous waste by incineration ensure
that the incinerators are operated in a
manner which does not endanger human
health or the environment. The Code of
Federal Regulations, Title 40, Part 264,
requires that a destruction and removal
efficiency of 99.99 percent be achieved
for each POHC designated in the Trial
Burn Permit. The DRE standard implicitly
requires sampling and analysis to quanti-
fy POHCs in the waste feed material and
stack gas effluent. The "Sampling and
Analysis Methods for Hazardous Waste
Combustion" manual (methods manual)
provides information on methods that are
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applicable for collection and analysis of
POHCs in process streams of hazardous
waste incinerator units.
The methods manual identifies three
possible methods for the collection of
volatile organics (those with boiling points
of <100°C). The methods include bag,
glass bulb, and the VOST. Evaluation of
the bags and bulbs indicates that these
sampling systems are subject to a number
of technical problems. The most important
of these problems is the inadequate
sensitivity for POHCs present in low
concentrations.
The VOST provides increased sensitiv-
ity to low-level concentrations of volatile
POHCs due to its ability to concentrate
the gaseous effluent. The results of
laboratory evaluation and field application
of the VOST have shown that it provides
sufficient sensitivity to permit calculation
of a ORE equal to or greater than 99.99
percent for volatile POHCs which are
present in the waste feed at 10O^i g/g.
The methods manual identifies the
VOST as a suitable sampling system for
volatile organics and includes a paper
describing the VOST. A detailed protocol
was not included in the methods manual
due to the fact that this is outside the
scope of the document.
The purpose of this protocol is to
provide a standard operating procedure to
users of the VOST in the collection and
analysis of samples for volatile POHCs in
the gaseous effluents of hazardous waste
incinerators or gaseous effluents of haz-
ardous waste co-fired combustion proc-
esses. The protocol is presented in two
parts. Part A describes the key compo-
nents of the VOST train, and the pro-
cedures for sample collection using VOST.
Part B describes the procedures for
analysis of VOST sorbent cartridges for
volatile POHCs using purge-trap-desorb
gas chromatography/mass spectrometry
(P-T-D GC/MS).
Part A—Sampling
The VOST is directly applicable to
organic compounds with boiling points of
30°Cto 100°C. Many organic compounds
with boiling points below 30°C and
between 100°C and 150°C may also be
effectively collected and analyzed using
the method However, laboratory evalua-
tion of the collection and recovery efficien-
cies for compounds with boiling points
outside the 30°C to 100°C range is
required prior to field sampling.
A schematic diagram of the principal
components of the VOST is shown in
Figure 1 The gas stream is filtered
through a glass wool plug in a quartz or
2
Glass Wool
Paniculate
Filter*
• Heated Probe
-Isolation Valves
.Carbon Filter
Vacuum
Indicator
Thermocouple
Sorbent
Cartridge
Exhaust
Stack
(or Test System)
Dry Gas
Meter
Silica Gel
Condensate
Trap Impinger
Figure 1. Schematic of Volatile Organic Sampling Train (VOST).
glass lined probe. The gas is then cooled
to 20°C by passage through a water
cooled condenser to facilitate collection
of volatile organic POHCs on a pair of
sorbent cartridges. Liquid condensate is
collected in an impmger placed between
the two sorbent cartridges. The first
sorbent cartridge contains approximately
1,6 g of Tenax, and the second cartridge
contains approximately 1 g of Tenax
followed by 1 g of petroleum based
charcoal, 3:1 by volume. Isolation valves
provide for purging the probe with stack
gas prior to sampling and for leak check-
ing the VOST
Laboratory data have been developed
for a concentration range of 0.1 to 100
/ug/m3 (0.1 to 100 ng/L) for selected
volatile POHCs. The concentration range
of 100/ug/m3 to 500/ug/m3 (100 ng/L to
500 ng/L) is not expected to pose prob-
lems. Although the upper end of the
range of applicability is limited by break-
through of volatile POHCs through the
sorbent cartridges used to collect the
sample, the range is also limited by
analytical constraints. Caution should be
exercised in using the VOST to collect
samples from a stack gas stream present
at high concentrations, 500^g/m3 (500
ng/L) or greater. The analytical detector
may overload during analysis resulting in
invalid data. It would be appropriate to
collect a reduced sample volume to
alleviate the problem. Analytical prob-
lems such as peak interferences due to
peak tailing or instrument overloading
need to be evaluated prior to field sam-
pling.
The VOST is designed to provide six
stack gas samples over a 2-hour sampling
period. The samples are collected at a
sampling flow rate of 1 L/min, using a
VOST equipped with a temperature con-
trolled quartz or glass-lined probe.
An alternate set of operating conditions
allows for reduced sample flow rate.
Operation of the VOST under these
conditions has been referred to as SLOW-
VOST. This method is used to collect 5 L
of sample (0.25 L/min for 20 minutes) or
20 L of sample (0.5 L/min for 40 minutes)
on each pair of sorbent cartridges. The
SLOW-VOST should be considered for
sampling organic compounds with boiling
points below 30°C. Fewer pairs of car-
tridge samples may be required for the
SLOW-VOST with a minimum of three
sorbent cartridges samples collected.
Part B—Analysis
The method of analysis for volatile
POHCs collected on VOST sorbent car-
tridges is thermal desorption followed by
purge-trap-desorb gas chromatography/
mass spectrometry (P-T-D GC/MS). Much
of the analytical method is described in
EPA Method 624. Since the majority of
gas streams sampled using the VOST will
contain a high concentration of water, the
P-T-D analytical method was chosen to
minimize the effect of water on the
analytical system.
A schematic diagram of the analytical
system is shown in Figure 2. Sorbenl
cartridges are spiked with internal stand-
ards and thermally desorbed into the P-T-
D system by heating to 180°C for 1C
minutes. Sample cartridges may be de-
sorbed in pairs. However, if the analyte
concentrations are anticipated to be
sufficiently high to saturate the GC/MS
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Flow During
Flow to
GC/MS
A/2
CD
Desorption
Flow During
He or A/a
Analytical Trap
with Heating Coil
(0.3 cm diameter
by 25 cm long)
Purge
Column
Thermal
Desorption
Chamber
f
Heated
Line
Vent
r) 3%SP-2100(1 cm)
( 2) Tenax (7.7 cm)
(!}} Silica Gel(7.7 cm)
Cty Charcoal (7 7 cm)
Figure 2. Schematic diagram of trap desorption/analysis system.
detector, when desorbed in pairs, con-
sideration should be given to individual
analysis of cartridges. The desorbed
components pass into the bottom of the
water column, and are purged from the
analytical trap into the GC/MS. The
volatile POHCs are separated by temper-
ature programmed gas chromatography
and detected by low resolution mass
spectrometry. The quantities of volatile
POHCs collected on the sorbent cartridges
are calculated using the internal standard
technique.
The sensitivity of the analytical method
for a particular POHC depends on the •
level of interferences, the level of back-
ground contamination on blank sorbent
cartridges, and the purgeability of the
POHCs from water. The target detection
limit for the method is 0.1/ug/m3 in stack
gas. This corresponds to 2 ng adsorbed on
a single pair of Tenax and Tenax/charcoal
cartridges. The desorption of multiple
pairs of cartridges onto a single pair for
subsequent analysis may be required to
achieve the detection goal of 0.1/u g/m3.
Most uses of the VOST have not required
this level of detection.
F. M. Hansen is with Envirodyne Engineers. Inc., St. Louis, MO 63146.
Robin M. Anderson is the EPA Project Officer (see below).
The complete report, entitled "Protocol for the Collection and Analysis of Volatile
POHCs Using VOST." (Order No. PB 84-170 042; Cost: $10.00, 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
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