EPA/600/A-95/086
Analysis of Modified Method Five Train Samples
for Multiple Pollutant Classes
Larry D. Johnson
National Exposure Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
ABSTRACT
The steadily increasing need for more complete characterization of stationary source emissions
has placed more demands on stack sampling organizations and on associated analytical laboratories to
operate as efficiently as possible. One way of increasing efficiency is to maximize the amount of
analysis on each sample collected, and thereby to minimize the number of samples taken. The
Modified Method 5 (MM5) sampling method produces samples which are particularly amenable to
analysis for multiple organic pollutants. Success in executing a combination of two or more methods
requires a thorough knowledge of the sampling method as well as the analysis procedures. It is
possible to produce excellent results with increased efficiency, but it is also not unusual to see data
produced that is invalid for one or more of the compounds of interest. Although verbal direction has
been offered to individuals, no published technical guidance has been available. This paper discusses
basic principles of planning analysis of MM5 samples for more than one class of pollutants. Benefits
and liabilities of combinations of this nature are examined. An example case involving analysis of
dioxins and polycyclic aromatic hydrocarbons is presented.
INTRODUCTION
Risk assessments and other comprehensive characterization projects are providing more
information about the chemical nature of stationary source emissions than ever before. Stack sampling
and analysis associated with these ambitious projects is usually quite expensive, so the incentive to
operate efficiently is considerable. Fortunately, most of the standard source methods yield samples that
are amenable to analysis for a number of pollutants. Perhaps the most ambitious effort to sample "all
things" at once was the Source Assessment Sampling System (SASS), Method 00201,2. This method
sampled semi-volatile and non-volatile organics along with gas-phase and particulate metals and salts.
Particulate samples were collected in four size fractions. The SASS worked well for preliminary
screening studies, but was not quantitative enough for many applications. This limitation was a direct
result of the many design and operation compromises that had to be made in order to maximize the
scope of pollutants sampled.
The most versatile quantitative organic sampling method is EPA Method 001G3. The sampling
train in Method 0010 is also known as the Modified Method 5 Train (MM5) or the Semivolatile Organic
Sampling Train (Semi-VOST). This sampling method is the most nearly universal of the quantitative
organic methods available, in that it performs adequately on the largest assortment of organic
compounds and operates under the widest variety of adverse conditions and potentially interfering
materials and situations. The MM5 sampling method produces samples which are particularly suited
for analysis of multiple organic pollutants or pollutant classes, such as dioxins, polycyclic aromatic
hydrocarbons (PAH), or polychlorinated biphenyls (PCB). It is often possible to analyze samples from
a single MM5 ran for several different pollutant classes, rather than acquiring a separate sample for each
analysis. However, there are many hazards in planning and executing combined analysis schemes, and
thorough knowledge of the methods is required along with careful attention to detail. This paper
provides written technical assistance to individuals attempting to plan, execute, or evaluate analysis
schemes involving multiple pollutant classes and MM5 sampling.

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BENEFITS AND LIABILITIES
There are liabilities which may be incurred when methods are combined. In each unique case it
is necessary that the planner be aware of the liabilities as well as the benefits, and that they be carefully
weighed against each other before final decisions about the approach are made.
Benefits
When the required analyses can be performed on fewer samples a number of benefits may occur,
some obvious and others more subtle. Fewer sampling trains on the stack sampling platform not only
results in decreased personnel and equipment costs, but less crowding may result in a safer working
environment. Less sampling equipment results in lower costs for shipping, cleaning, packing and other
preparation. Fewer samples usually require less demand on extraction equipment, less solvent use, and
perhaps less analysis instrument time. The analysis time saving is only achieved when the analysis for
two or more of the pollutant classes can be performed simultaneously.
Liabilities
A higher detection limit is frequently the price one pays for multiple pollutant analysis. It is
often necessary to split the sample for separate processing through two different preparatory analysis
procedures. If the sample is split into two equal parts, each will have its detection limit doubled. If the
sample can be processed through most of the analysis scheme without being split, it may be possible to
avoid a detection limit increase. The potentially most damaging of the liabilities sometimes incurred
with combined methods is the danger of compromised results. Compromised data often is the result of
combining analysis methods with incompatible sample preparation procedures, such as extractions or
sample cleanup. A major portion of this paper will discuss in detail many of the possible causes of
compromised results and ways to avoid them. Another possible disadvantage of hybrid methods is the
danger of non-acceptance, especially by Federal, State or local regulatory personnel. Use of a merged
method to provide data for regulatory compliance must always be negotiated with the proper regulatory
authorities, and should always be proposed well in advance of the field testing. The amount of
flexibility available to regulators in acceptance of hybrid or modified methods varies greatly from
agency to agency and even from regulation to regulation, and is best established early in the planning
process. Another hindrance to the planner or the reviewer of combined methods has been the lack of any
published material dealing with the subject.
CRITICAL ELEMENTS
Although each attempt to combine two or more analysis procedures may have its own unique
pitfalls, familiarity with basic principles and recurring difficulties should be helpful to the reader.
Several of the more important issues are discussed in this section.
Sampling Method
It is necessary to exercise discretion in the planning process to make sure that analytes
inappropriate for collection by Method 0010 are not added to the target list. For example, carbon
tetrachloride is entirely unsuitable for sampling by Method 0010. Carbon tetrachloride has a boiling
point of 78° C, well below the minimum of 100°C required for adequate Method 0010 collection. In the
usual 2 hr. sampling run, carbon tetrachloride would exceed its volumetric breakthrough limit and begin
to "leak" through the XAD-2 sorbent cartridge. The breakthrough effect alone would cause a low bias in
the results, but as will be discussed later, the sample preparation procedure would be even more
damaging. Another compound which shouldn't be sampled by Method 0010 is 2-4 toluene diisocyanate
(TDI). Although the 251°C boiling point of TDI is well within the acceptable range, the reactivity of the
compound makes quantitative recovery from Method 0010 very unlikely.
The sorbent of choice for use with Method 0010 is almost always XAD-2. XAD-2 is relatively
non-specific in its sorption behavior, and has been well characterized with respect to its physical
properties as well as breakthrough and recovery performance4,5. Selection of an alternative sorbent is

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seldom necessary, and serious consequences may result from a poor choice. Nonetheless, sorbent
substitution may sometimes be necessary, and suitability of the new sorbent for all target compounds
must be ensured. In such cases a literature search will be mandatory, and laboratory research may be
needed.
As mentioned previously, the typical length of a Method 0010 sampling run is 1-2 hr. This run
time may sometimes be extended to 4 hr. or even more, in order to maximize the amount of analyte
collected. More analyte in the same volume of extract ultimately results in lowered stack gas detection
limits. Extended sampling times and the associated higher gas volumes sampled may cause volumetric
breakthrough of lower boiling analytes through the XAD-2 sorbent. When combining methods where
extended sampling times are involved, care must be taken that the lowest breakthrough volume of any of
the target compounds is not exceeded. For example, if one were sampling for 6 hr. in order to decrease
the detection limit for dioxin, analysis of the same extract might be possible for benzo[a]pyrene ( b.p.
311° C) but would not be quantitative for toluene (b.p. 111° C).
Standards
Several kinds of standard compounds are typically added, in known amounts, to the samples at
various stages of analysis. The two most common reasons for the use of these standards are to measure
or compensate for analyte recovery losses or to compensate for instrument response changes between the
times of calibration and analysis. Frequently seen names for three types of standards are internal
standards, recovery standards, and surrogates. Unfortunately, these names are not applied consistently
throughout all methods. What one method calls an internal standard is known as a recovery standard in
another. The following is a traditional, but certainly not universal, explanation of the types of
standards. Recovery standards are added to the samples after receipt in the laboratory and before
preparatory analysis steps such as extraction and sample concentration. Since the best recovery standard
is one that acts most like the target compound itself, addition of an isotopically labeled analog of each
target compound would be ideal and would allow accurate calculation of recovery of the target
compound. When only a few compounds are on the target list, this procedure may be followed, but it
may become expensive if large numbers of analytes are involved. Surrogates are usually a group of 4 to
10 compounds serving as recovery standards for an entire target list of perhaps a hundred compounds.
Surrogates must be compounds not expected to occur in the sample, or must be isotopically labeled so
they can be distinguished from the native target compounds. Internal standards are usually added to
sample extracts just before analysis and are used primarily to compensate for instrument response
changes. Isotope dilution analysis uses isotopically labeled analogues of the target compounds as
recovery standards or internal standards or to serve both functions. In isotope dilution analysis
automatic correction for recovery and instrument response is usually an integral part of the concentration
calculations. In reality, the situation is often even more complicated than it seems here.
Fortunately, the planner or the reviewer of combined analysis methods does not necessarily have
to understand all the fine details of standards and isotope dilution schemes. He or she does need to know
three things concerning the area of standards technology. The first is that the standards can be a source
of incompatibility between methods which are candidates for combination. The second is that the
incompatibility usually occurs when a standard from one method interferes in the analysis of the other
method, when a surrogate is used to represent a compound for which it is unsuited, or when the systems
of additions corrections and other calculations of the two methods are carelessly combined. The third,
and probably most important, thing that the reviewer or planner needs to know is to get assistance in this
area from a well qualified analytical chemist who understands the intricacies of the methods and the
standards and calculations that are involved.
Sample Preparation
Choice of solvent for extraction of the samples is very important. The solvent selected must
extract all target analytes well without chemically altering them, must not interfere in the analysis,
should be subject to concentration, and must be chemically compatible with the sampling sorbent.

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Dichloromethane is by far the most popular solvent for recovery of Method 0010 samples, and toluene
holds second place. If the two methods to be combined both utilize dichloromethane, there is obviously
no extraction solvent problem. If the planner combines a dichloromethane based procedure with one
using toluene or any other higher boiling solvent, it may become difficult to concentrate the resulting
extract without loss of more volatile target compounds. In the example discussed earlier, even if carbon
tetrachloride had been collected quantitatively, it would be lost in either the extraction step or the later
extract concentration.
Sample recovery from the MM5 train yields three subsamples, one from the combination of
probe rinse and particulate filter, one from the sorbent module and associated rinses, and one from the
condensate. In some MM5 based methods, such as Method 236, the three subsamples are combined and
extracted as a single sample. In others, the subsamples are extracted and analyzed separately. There are
advantages and disadvantages to each approach, but one or the other strategy must be chosen when
combining methods.
Many analytical methods include cleanup procedures, such as column chromatography or gel-
permeation chromatography, designed to remove interfering organics but to have minimal effect on the
target analyte. When two of these analysis schemes are combined, care must be taken that the target
analytes are not removed along with the unwanted compounds. The author reviewed a paper where the
investigators processed samples for dioxin analysis through an extensive cleanup scheme designed to
remove virtually all other organics and then proceeded to analyze for other combustion products. Most
mistakes of this nature are considerably more subtle, but can be equally devastating to the accuracy of
the results. With care, hybrid cleanup schemes can be designed that can remove interferences without
removal of the compounds of interest. In some cases the cleanup procedures can be dropped entirely. In
some cases the only viable solution is to split the extract, clean up and analyze the fractions separately,
and to accept the resultant increase in detection limit. In general, the more compounds are analyzed, the
more difficult it becomes to design an effective cleanup scheme that does not degrade accuracy of
quantitation or detection limit.
Sample extracts are usually concentrated to a total volume of either 5 ml or 1 ml, depending upon
the detection limit required, the volatility of the analytes, and sometimes other factors. Dioxin samples
are often taken completely to dryness during processing. The more volatile analytes will be lost if
concentrated too far, and most analytes should not be taken to dryness.
Analysis Methods
Simultaneous analysis of a single extract for all target analytes is the ideal strategy. Often, this is
possible, especially when using gas chromatography with mass spectrometric detection (GC/MS). In
some cases, two or more separate determinative analyses are needed, sometimes requiring extra sample
splitting.
PAH & DIOXINS
Two groups of pollutants frequently tested in combustion source emissions are dioxins and
polycyclic aromatic hydrocarbons (PAH). Several methods applicable to these classes of compounds
have been published. USEPA Method 0010 is appropriate to both classes; USEPA Method 23 is
specifically for collection and analysis of dioxins and fiirans. CARB Method 4297 is for collection and
analysis of PAH, while CARB Method 428s collects and quantitates dioxins, fiirans, and polychlorinated
biphenyls. All of these methods are very closely related, and all use MM5 sampling technology. An
example trial method merge of Method 23 and CARB 429 will be discussed.
Compatibilities
In a merge of the two methods under consideration, there are far more features that are congruous
than not. This is partly because of the similarity of the methods and partly due to the somewhat similar
nature of the target analytes. The sampling hardware and procedures are the same for the two methods,
and the sorbent utilized is XAD-2. In some instances, Method 429 has an XAD-2 related problem.

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When a very low detection limit for naphthalene is needed, it may be difficult to clean the sorbent
adequately of naturally occurring naphthalene. If the blank level of naphthalene in the cleaned sorbent is
low enough or if the concentration at which naphthalene is of concern is high enough, no problem exists.
In extreme cases of blank interference, an alternate sorbent might be necessary. As previously discussed
sorbent substitution is not a step to be undertaken lightly. Extraction procedures and subsample
combination schemes for the two methods are compatible. Extraction solvents are different, and will be
dealt with in the next section. The determinative analytical procedure for both is GC/MS. Method 23
requires high resolution GC/MS, while Method 429 gives the user the option of low resolution or high
resolution instrumentation. The obvious solution is that the merged method would be analyzed by high
resolution GC/MS. Further investigation would be necessary to determine whether the analysis for both
compound classes could be performed with a single injection on a single GC column or whether
different columns or temperature programs would be needed.
The addition and choice of standards appears to be compatible, but would need closer study by a
specialist. Both methods use a number of isotopically labeled standards, which probably don't interfere
with each other analytically, but would need to be scrutinized more closely. Method 23 has isotope
dilution recovery corrections hidden in the concentration calculations, a complication which would have
to be dealt with carefully in constructing the calculations for the merged method.
Problem Areas
Method 429 uses dichloromethane as the extraction solvent, while Method 23 requires toluene.
Although dichloromethane is an inadequate extractant for dioxins from particulate matter, toluene is an
acceptable alternative extractant for PAH. The obvious answer is to use toluene in the merged method.
If, however, other target analytes were to be added to the method the adequacy of toluene for extraction
of each would need to be closely considered. Toluene is not as universally effective as dichloromethane;
it just happens to be a good solvent for both dioxins and PAH.
The liquid chromatography cleanup procedures for the two methods are incompatible. If low
detection limits are not needed, the simplest approach would be to split the sample extract before
cleanup. It might be possible to recombine the split sample after clean up, thus avoiding the degradation
of detection limit. Design of a new cleanup procedure in which the two classes of compounds were
recovered in separate fractions would also be a definite possibility.
At one point in Method 23, the sample extract is taken to dryness. For PAH analysis, and that of
most other organic compounds, this procedure is unacceptable. Even though most PAH are relatively
high boilers, their vapor pressures are sufficient to cause significant losses upon complete evaporation of
solvent. One could take the extract from the merged method to dryness and rely upon the recovery
standards to correct for volatility losses. The magnitude of the losses would determine whether that
approach was feasible. Another approach would be to split the sample before the concentration step.
Further consideration of the need for taking the dioxin extract to dryness might reveal that the drying
step could be omitted altogether.
SUMMARY
It is often possible to increase efficiency of sampling and analysis of stationary source emissions
by combining analysis schemes for multiple pollutant classes collected with the modified method five
train. Creation of merged methods must be done with care and a great deal of knowledge. It is hoped
that this paper will prove useful instruction, especially to those readers responsible for planning or
review of combined analysis schemes.
NOTICE
The information in this document has been wholly funded by the United States Environmental
Protection Agency. It has been subjected to Agency review and approved for publication. Mention of
trade names or commercial products does not constitute endorsement or recommendation for use.

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REFERENCES
1	D.B. Harris, W.B. Kuykendal and L.D. Johnson, "Development of a Source Assessment Sampling
System," presented at Fourth National Conference on Energy and the Environment, Cincinnati, OH,
October 1976.
2	U.S. Environmental Protection Agency, Method 0020, in Test Methods for Evaluating Solid Waste,
Physical/Chemical Methods, SW-846 Manual, 3rd ed. Document No. 955-001-0000001. Available
from Superintendent of Documents, U.S. Government Printing Office, Washington, DC, November
1986.
3.	U.S. Environmental Protection Agency, Method 0010, in Test Methods for Evaluating Solid Waste,
Physical/Chemical Methods, SW-846 Manual, 3rd ed. Document No. 955-001-0000001. Available
from Superintendent of Documents, U.S. Government Printing Office, Washington, DC, November
1986.
4.	J. Adams, K. Menzies and P.L. Levins, Selection and Evaluation of Sorbent Resins for Use in
Environmental Sampling, EPA-600/7-77-044, PB268-559, U.S. Environmental Protection Agency:
Research Triangle Park, NC, April 1977.
5.	R.F. Gallant, J.W. King, P.W. Levins and J.F. Piecewicz, Characterization of Sorbent Resins for Use
in Environmental Sampling, EPA-600/7-78-054, PB284-347, U.S. Environmental Protection
Agency: Research Triangle Park, NC, March 1978.
6.	Method 23, Code of Federal Regulations, Title 40, Part 60, Appendix A, pp 827-839, U.S.
Government Printing Office, Washington, DC, 1993.
7.	California Environmental Protection Agency, Air Resources Board, CARB Method 429, Sacramento,
CA, 1989.
8.	California Environmental Protection Agency, Air Resources Board, CARB Method 428, Sacramento,
CA.

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TECHNICAL REPORT DATA
1. REPORT NO.
EPA/600/A-95/086
2 .
3
4, TITLE AND SUBTITLE
Analysis of Modified Method Five Train Samples for Multiple Pollutant
Classes
5.REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR (S)
Larry D. Johnson
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
National Exposure Research Lab
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
N.A.
12. SPONSORING AGENCY NAME AND ADDRESS
National Exposure Research Lab
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 277X1
13.TYPE OF REPORT AND PERIOD COVERED
Symposium Proceedings
Measurement of Toxic and
Related Air Pollutants, RTP
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The steadily increasing need for more complete characterization of stationary source emissions
has placed more demands on stack sampling organizations and on associated analytical laboratories to
operate as efficiently as possible. One way of increasing efficiency is to maximize the amount of
analysis on each sample collected, and thereby to minimize the number of samples taken. The
Modified Method 5 (MM5) sampling method produces samples which are particularly amenable to
analysis for multiple organic pollutants. Success in executing a combination of two or more methods
requires a thorough knowledge of the sampling method as well as the analysis procedures. Although
verbal direction has been offered to individuals, no published technical guidance has been available.
This paper discusses basic principles of planning analysis of MM5 samples for more than one class of
pollutants. Benefits and liabilities of combinations of this nature are examined. An example case
involving analysis of dioxins and polycyclic aromatic hydrocarbons is presented.
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