Stack Sampling for Organic Emission

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Stack sampling for organicemissionsLarry D. Johnson a & Raymond G. Merrill aa Industrial Environmental Research Laboratory,U.S. Environmental Protection Agency, ResearchTriangle Park, North Carolina, 27711, U.S.A.Version of record first published: 19 Sep 2008.

To cite this article: Larry D. Johnson & Raymond G. Merrill (1983): Stacksampling for organic emissions, Toxicological & Environmental Chemistry, 6:2,109-126

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Toxicological and Environmental Chemistry, 1983, Vol. 6, pp. 109-1260277-2248/83/0602-0109 $18.50/0© Gordon and Breach Science Publishers Inc., 1983Printed in Great Britain

Stack Sampling for OrganicEmissions

LARRY D. JOHNSON and RAYMOND G. MERRILL

Industrial Environmental Research Laboratory, U.S. Environmental ProtectionAgency, Research Triangle Park, North Carolina 27711, U.S.A.

(Received 12 August, 1982)

Along with increased activity in source sampling for organics, there have been manyimprovements in the methods of acquiring samples. Much has been learned about how bestto proceed, and a number of potentially serious pitfalls have been discovered, characterized,and circumvented. Unfortunately, communication of all of this new technology has notalways been effective.

This paper reviews some of the more important fundamental principles involved in stacksampling for organics, briefly describes and discusses recently developed equipment, andpoints out a few of the more serious pitfalls to be avoided. Extensive references are provided,many of which are often overlooked by newcomers to the field. The conclusion is reachedthat it is possible to consistently obtain high-quality samples of organic materials fromstationary source stacks, even though knowledge and caution are necessary.

KEY WORDS: Organics, sampling, stacks, emissions.

INTRODUCTION

Although it is not difficult to point out examples of stationary sourcesampling projects for organic emissions during the mid-1960's or perhapseven earlier, there has been a dramatic increase in their number andsophistication in the last 5 to 10 years. This had been due to a number offactors including: increased awareness and concern with respect to organicpollutants, improved and more available sampling equipment, improvedmethods for analysis of the samples, and more general activity inenvironmentally related areas. A recent driving force for additionalsampling of organic emissions is the still formative trend towardincineration as a method of disposal of many hazardous wastes.

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110 L. D. JOHNSON AND R. G. MERRILL

Along with the increased activity in source sampling for organies, therehave been many improvements in the methods of acquiring samples.Much has been learned about how best to proceed, and a number ofpotentially serious pitfalls have been discovered, characterized, andcircumvented. Unfortunately, communication of all of this new technologyhas not always been effective. As a result, there are a number of commonmisconceptions and a great deal of ignorance concerning the use of sourcesampling equipment for organies. This is beginning to result in publicationof conclusions which are meaningless at best, and highly misleading to theuninitiated.

This paper reviews some of the more important fundamental principlesinvolved in sampling for organies, briefly describes and discusses recentlydeveloped equipment, and points out a few of the more serious pitfalls tobe avoided. No attempt has been made to discuss, or even list, allsignificant publications in this field. The reader interested in further detailwill find that the selected references will provide many hours of interestingreading as well as guidance to a more extensive literature base.

RECOMMENDED SAMPLING TRAINS

When faced with the task of sampling organic emissions from a stationarysource, the investigator must select from a relatively limited number ofapproaches. No approach known at present is without disadvantages andlimitations. The author of a successful sampling plan must know thelimitations inherent to each approach and be able to choose the mostappropriate procedures for the job at hand.

For general purpose flue gas sampling for organies, most experiencedinvestigators prefer a train utilizing a fiberglass filter for solids and a solidsorbent cartridge for vapors. Several reasons for this are: (1) fiberglassfilters have been used extensively; (2) their properties are known; and (3)the sorbent system is easy to apply, readily portable, safer than solventsystems (especially around incinerators and other combustion sources),produces a sample which is easy to handle and ship, and providesconsiderable sample concentrating action.

Two sampling trains are recommended for general purpose stacksampling of organic compounds with boiling points above 100°C: themodified Method 5 Train (MM5) and the source assessment samplingsystem (SASS). Figures 1 and 2 are schematic diagrams of these twodevices. It is important to realize that, from a conceptual standpoint, theseare really the same train except for size. The essential collection elementsof both trains are: a filter for removal of particulate matter, a cooledsorbent module, and a condensate collector. Other non-collection elements

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SAMPLING FOR ORGANIC EMISSIONS 111

HeatController

dotationBall Valve

Convection Oven | FilterGai

Cooler

Two 10-ft3/min (280-L/min)Vacuum Pumpi

FIGURE 1 SASS train.

Vacuum Line

Dry Gat Air-tightM4t*r Pump

FIGURE 2 Modified Method 5 train

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of the trains are, of course, essential to operation of the equipment andare shown in the diagrams. The SASS train was designed to collectorganics as well as inorganics and has built-in collection elements. TheMM5 train results from a very simple modification of any of thecommercial sampling trains available which conform to the requirementsof EPA Method 5. The sorbent module with cooling capability is simplyinserted between the filter and the first impinger. The first impinger thenfunctions as a condensate collector. Later impingers or bubblers on eithertrain may be filled with a variety of liquids for the purpose of trappingspecific organic or inorganic materials.

Even though the SASS and the MM5 trains are conceptually identical,differences in the two trains usually make one or the other the betterchoice for a particular job. The SASS is a high-volume train usuallyoperated at 110 to 1401pm (4 to 5cfm), while the MM5 samples 14 to28 lpm (0.5 to 1 cfm) under normal circumstances. Either train should givesatisfactory results when properly applied to an appropriate source. Theability of the SASS train to provide a large sample to the analyst willoften be critical, and will dictate use of that train. When a large sample isnot required, the smaller and more corrosion resistant MM5 train willusually be adequate.The MM5 train is constructed of glass, while the SASS is built of stainlesssteel. For most sources this has been found to make little difference. Forsources high in HC1, such as many incinerators, the stainless steel of theSASS may be severely attacked. Most of the corrosion occurs in thesorbent module at and beyond the point where the gases are cooled andwater condenses. A corrosion resistant sorbent module for the SASS iscurrently under development at Southern Research Institute, and at leasttwo similar devices have already been built and tested by Battelle-Columbus and PEDCo.

The MM5 train is generally operated just as it would be for compliancetesting, including a full-stack traverse and flow-rate adjustment tomaintain isokinetic sampling. The SASS is large enough that traversing isinconvenient, but not impossible unless precluded by physicalarrangements at the sampling site. The sizing cyclones on the front half ofthe SASS, however, require constant flow rate for consistent sizediscrimination. For environmental assessment, the sizing information isusually of great interest, so flow rate should not be varied duringsampling.

Therefore, the SASS is generally operated at a single point in the stackand under pseudoisokinetic conditions (with the train equipped with aprobe nozzle such that sampling is initially near isokinetic and the flowrate through the cyclones is that required for proper sizing). As sampling

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progresses, the flows are monitored but the sampling rate is not altered tomatch small changes in stack velocity. Major changes in stack velocity orpressure drop in the train are causes for shutdown and corrective action.1

Under most circumstances, this mode of operation results in samplesindistinguishable from those taken under full isokinetic conditions. Onestudy showed that two SASS trains operated in this manner producedparticulate loadings within 8 percent of those from a Method 5compliance test on three succeeding days.2 Sizing results and organicanalysis data from the two SASS trains were also remarkably consistent.

Although not the usual mode of operation, it is possible to operate aSASS train just like a Method 5 train, thereby sacrificing the sizinginformation. The cyclones are removed, or their catches are simplycombined after sampling is completed.

For the most part, isokinetic sampling is not nearly as critical as manybelieve. It is necessary for particulate compliance monitoring, but isgenerally overrated for most other projects. The discussion- betweenreviewers provided in Reference 3 is typical of disagreements relative tothe importance of isokinetic sampling.

Isokinetic sampling becomes less important as particle size decreases andis generally of marginal importance for particles less than 2/mi indiameter. Further discussions of inertial effects on particle sampling are inReferences 4 and 5.

SOLID SORBENTS FOR SAMPLING

As previously noted, each of the recommended trains is equipped with asorbent module for collecting vapor-phase organics. These modules arenormally loaded with porous polymer resins. XAD-2 is currentlyrecommended for all general stack sampling applications where the modeof recovery will be solvent extraction. If the job requires heat desorptioninto a gas chromatography/mass spectrometry (GC/MS) system, thenTenax GC is clearly superior because of its higher thermal resistance. Thesolvent for extraction of XAD-2 is methylene chloride for mostapplications. This solvent has been shown to cause no measurabledegradation of the resin or its properties.

In addition to porous resins, a number of other substances may be usedin sorbent traps: charcoal, silica gel, Florisil, molecular sieves, and othermaterials. For a specific application any one of these might be the correctchoice; however, each has major disadvantages. Charcoal often exhibitspoor recovery properties and has been indicted for catalyticdecomposition of sorbate.6 Silica gel and Florisil have low surface areaand poor moisture tolerance in many applications.7'8 Molecular sieves'

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performance may be sensitive to moisture levels in stack gases.9 A numberof porous polymer resins are commercially available and have been foundsatisfactory by many investigators including those in the reference list.Manufacturers and sources of these materials are well documented in thereferences and will not be repeated here. The most important properties ofthe resin related to sampling performance are temperature tolerance,particle size and distribution, pore size and distribution, surface area, andchemical properties such as acid and solvent resistance, polarity, andnature of chemical blank. These properties influence pressure drop acrossthe sorbent bed, tolerance to stack conditions, sorption behavior, andrecovery characteristics.

Table 1. Properties of Sorbents

Sorbent

Chromosorb 101Chromosorb 102XAD-2XAD-4XAD-7XAD-8Tenax-GCXE-340

Mesh

40-8020-5020-50

__

35-6020-50

Surfacearea, m2/g

3037435092545014025

400

Poresize, A

3,50085905090

235720

Temp.limit, °C

250250200200200200375

Table I lists some of these properties for selected sorbents. Note that thetemperature limits given in Table I are those usually quoted forcatastrophic destruction of the resins. The resins must be maintained attemperatures much lower than these during sampling to prevent anunacceptable rise in the resin blank. (This point will be discussed further,later in the paper.) Because of its low surface area, Chromosorb 101 is notattractive for sampling applications. Chromosorb 102 is similar to XAD-2,but is only available in fine mesh sizes which cause unacceptable pressuredrops in most sampling equipment. XAD-4 might appear the best choicebecause of its impressive surface area; however, difficulties have beenencountered in cleaning and in sample recovery.7 One possibleexplanation lies in the very small pore size which may cause masstransport problems. XAD-7 and XAD-8 are currently under evaluation forstack sampling applications, but some recovery problems have alreadybeen noted by water sampling investigators.10 Likewise, the AmbersorbXE series of resins shows promise, but has not yet been thoroughlyevaluated and should not be utilized without recovery information on thespecies of interest. For use as a general sorbent, this means that variouscompound classes should be investigated on the resin of interest. Extensivedata are not yet available for the XE series.

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Before setting out to evaluate the adequacy of a new or existing sorbentsampling system for a given pollutant or class of pollutants, it is crucial tounderstand the concepts of volumetric breakthrough and weight capacityand to have access to appropriate experimental data relevant to the task.Weight capacity is related to saturation of the resin with sorbed material,while volumetric breakthrough is related to the migration rate of sorbedmaterial through unsaturated sorbent beds. These concepts are thoroughlydiscussed and data are provided for a number of compound classes inReferences 7, 11, 12 and 13.

PITFALLS AND A FEW RECOMMENDATIONS

A few mistakes in train design and resin utilization are rapidly building afrequency record sufficient to qualify them as classic. Some of the moretroublesome ones are discussed.

There is a tendency to include a waterfilled impinger or similar deviceahead of the resin bed in organic sampling trains. This is highlyundesirable for general sampling and should only be used where heavy tarloadings or other special circumstances force the arrangement. Otherwisethe train should be arranged so that condensate percolates through theresin bed and accumulates in a subsequent condensate container. Theresin removes all but the most highly water soluble compounds from theliquid as well as the gaseous stream and thereby minimizes the potentialfor unwanted reactions. Jones13 describes situations where a five-folddecrease in polycyclic aromatic hydrocarbon (PAH) recoveries weredocumented when waterfilled impingers were inserted ahead of the resinmodule. The resin bed should be vertical so that the condensate percolatesdown through the sorbent to promote continuous even flow, and tominimize bed channeling.

Most resin sorbents require careful cleaning and storage before use andall require testing for pertinent levels of analytical interference. XAD-2 aspurchased from the manufacturer requires a multiple solvent clean-upprocedure such as that given in Reference 1. Precleaned resin fromcommercial sources is generally much improved and may be satisfactoryfor a given sampling task as received, or may require only a single solventfinal cleaning. The final solvent in the cleaning sequence should always bethe same as that used for extraction of the resin for analysis. It is essentialthat the cleaned resin be checked for interference level in the analysisscheme to be used. A material which causes unreasonable interference in aGC analysis may be of no consequence in a MS method. All of this isquite simple and basic, but omission and misunderstanding continue tocause major problems and invalid data.

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After cleaning, the sorbent resin should be handled and stored carefullyto avoid contamination. XAD-2 resin should never be subjected totemperatures above 100°C; and it is highly preferable not to heat thecleaned resin at all. Even though the catastrophic failure temperature ofthe resin is around 200°C, the resin analytical blank increases dramaticallyafter exposure to temperatures in the vicinity of 100°C.14 This seems to beparticularly troublesome, and it is not uncommon to see publishedexperimental data which have apparently been compromised by thiseffect.15 Two room temperature drying procedures for XAD-2 resin areincluded in Reference 1. Other acceptable methods are undoubtedlypossible.

Cleaned resin must be protected from external contamination. Theusual means is storage in airtight glass containers, but one school ofthought prefers storage under ethanol or methanol. There is some merit tothe latter approach, but it is not without pitfalls of its own and shouldonly be used after thorough investigation of its merits for a given project.Note that there is a major difference between storage procedures for resinto be used in stack sampling and those for water sampling: the latter isnever allowed to dry completely and is usually stored under alcohol.Whichever storage method is used, the shelf life of cleaned resin has thusfar been highly variable. Always be suspicious of resin stored more than afew months. A truly careful investigator will run resin analytical blanksjust before sending the sorbent to the field, regardless of storage time. Themechanism for the increase in resin blank when stored is not fullyunderstood, but appears more likely to be a migration phenomenon thanpolymer breakdown. A single extraction clean-up with the finish solventwill usually be sufficient to restore resin (which has excessive blank levels)to an acceptable state. It is also advisable to send a loaded resin cartridgeto the field and extract and analyze it upon return, for an indication ofartifacts or materials picked up in the field, but not in the stack sample.

After the sampling has been carried out, and the loaded resin isreturned to the field, it must be handled with care and common sense.Although it is unacceptable to heat the resin to remove moisture beforeextraction, this practice has been observed. Not only is there the risk ofheat desorbing many of the sampled organics, but an increase in sorbentblank is also likely. The resin also may pick up organics from thelaboratory atmosphere. Excessive exposure of the resin should beavoided.

During sampling with sorbent resins, the sorbent module must beadequately cooled. The ability of the sorbent to remove organics from thegas stream increases with decreasing temperature. In addition to thiseffect, the cooler temperature protects the resin from the "thermal blank"

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effects discussed previously, and helps to minimize chemical reactionsbetween the sample, the resin, and gas stream components. The sorbent inthe SASS is kept at 20°C, also the preferred temperature for the sorbentmodule in a MM5 train. Early MM5 projects were carried out at 90°Cusing Tenax GC as the sorbent.13 Performance was satisfactory on theseprojects since the investigators were only interested in PAH, which sorbreadily. The same investigators now recommend lower temperatures, andprefer XAD-2 over Tenax GC.16-17

Also note that organics with boiling points below about 100°C are notretained satisfactorily by either XAD-2 or Tenax GC under normalconditions in either train. If these materials are of interest, they should besampled separately by one of the methods discussed in thereferences.1'1^"21

Both XAD-2 and Tenax GC have been extensively characterized withrespect to their retention behavior toward many organic compounds, aswell as the nature of their analysis blanks, thermal resistance, and manyother important characteristics.7'11-12> 14'22> 23

It is imprudent to switch from one of these resins to another withoutvery convincing and compelling reasons. If such reasons exist with respectto a given project, then another sorbent should be utilized only aftercareful and thorough preparation, which may require generation of a greatdeal of experimental data. It is essential that retention and recovery databe available for the compounds or compound classes of interest. In thecase of comprehensive sampling and analysis projects, this means thatbehavior toward a number of compound classes must be characterized.For example, Florisil has been validated for use in sampling ofpolychlorinated biphenyls and is quite acceptable for that purpose.24 Atpresent, it has not been tested with enough different organic compoundclasses to warrant its use as a general sorbent.

The SASS train filter and cyclone oven were initially designed tooperate at 205°C to minimize sulfate artifacts on the filter. However, thistemperature has been found to benefit organic sampling. A very highproportion of the organics in the 100° to 300°C boiling range are collectedon the sorbent resin rather than the filter. For certain compounds, such ashigh molecular weight PAH, the analytical extraction efficiency from thesorbent is much higher than from flyash or a similar particulate material.It is therefore recommended that the MMF train filter be held as near205°C as possible without violating other restrictions such as compliancetesting requirements.

Another potential difficulty has been passed on from the days when thesampling trains were utilized only for total particulate measurements. It isgenerally easier to meet sampling train leak test requirements if ball joints,

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etc. are coated with silicone grease or similar material. The presence ofany kind of grease contamination anywhere in the sampling train is veryundesirable when organic analysis will be performed on the resultingsamples. It is quite possible to pass leak test requirements without thegrease, and the sampling crew should be trained to do so if they havedifficulty. If necessary, joints or seals on the sampling train should bereplaced with ones designed for greaseless operation.

OTHER SAMPLING DEVICES

The two trains previously recommended are general purpose trains forcomprehensive sampling within the limits discussed. For a given project ora special purpose, they may not be the best choice. A few of the moreprominent alternatives for stack sampling are discussed.

There is merit in the argument that estimates of potential health effectsor risk assessment modeling may be better accomplished with samples andanalyses of material in the form presented to receptors rather than in theconcentrations and form found in stacks. If this argument is translateddirectly into action by attempting studies of samples taken from theambient air, a number of difficulties often arise. Perhaps the mosttroublesome is that stationary sources are often near each other and theemissions become mixed, causing interpretation difficulties.

One solution to the problem is to draw a sample from the stack, butcause it to undergo dilution and cooling (to promote condensation) andpossibly other processes imitating occurrences in the environment. Adilution train that does this has been tested, and appears to performwell.25 Other less portable arrangements utilizing the same ideas havebeen reported, mostly for automotive exhaust studies.26"28

It is most important to understand that this type of sampling is veryuseful for obtaining an ambient-like sample, but is not adequate by itselffor characterization of organic emissions from a source. Most dilutionsamplers to date cannot capture organics in the 100°C to 300°C boilingrange, and most of this material will be lost. The dilution sampler inReference 27, however, does include an XAD-2 sorbent module, whichdemonstrated good recovery of PAH. It is not at all unusual to see tenfolddifferences in the organic catch from an SASS as opposed to a typicaldilution train without sorbent capability sampling the same stack. Table IIillustrates the difference using data from Reference 26. The total organiccatch from the SASS is from twofold to twenty-threefold higher than thatfrom the dilution tunnel on the same source stream.

To perform extensive chemical and biological characterization onparticulate samples taken from a stack, it is sometimes necessary to

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Table 2.

Fuel

PineOakOil, run 1.1Oil, run 1.2Oil, run 2.1Oil, run 2.2

SASS Versus Dilution Sampling

Total organics, mg/m3

SASS

1,450770

8.45.55.23.2

Dilutiontunnel

563322

0.360.360.320.17

Factor

2.62.4

23151619

acquire kilogram quantities of material. Although it is possible to do thiswith an SASS or even an MM5 train, it is seldom practical or costeffective. A device to fill this need was designed and successfully fieldtested for EPA by Southern Research Institute. This massive volumesource sampler (MVSS) utilizes a cyclone sizing device followed by afluorocarbon-coated fabric filter particle collection. It samples at a flowrate of 340 Nm3/hr and requires about 2.5 days of sampling to collect 1 kgof particulate matter from the outlet of an efficient control device with aparticulate mass concentration of 0.05 g/Nm3.29 '30 A somewhat similarhigh-volume device developed at Battelle-Columbus was designed and hasbeen utilized for ambient air sampling, but could presumably be appliedto the end of a dilution tunnel.31 '32

If large quantities of particulate material are needed for biologicaltesting or other purposes, and if a long-term integrated sample issatisfactory (or even preferable), a device such as that described byMcFarland33 is appropriate. Such devices are generally used for samplingperiods of around 30 days. Such long-term integration is an advantage ifan average sample is sought, but a disadvantage if knowledge ofvariations within that timeframe is needed. Long collection periods alsoincrease the chances of sample degradation. The system should bedesigned to isolate the collected sample from the flow stream to themaximum degree practical, and to keep it as cool as reasonable withinoperating constraints.

The MVSS, the Battelle massive volume sampler, and theMcFarland/Fisher train all share with the dilution trains and tunnels, aninability to collect and deliver organics in the 100°C and 300°C range.This limitation certainly does not negate the usefulness of these devices onappropriate projects, but must always be kept in mind when interpretinganalysis performed on the samples collected.

It is often quite useful, although expensive, to collect samples from agiven source using two or more of the train types mentioned. Forexample, the stack dilution sampling system (SDSS) could be used in

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conjunction with an SASS or MM5 train. The former would providesamples to be used to gain insight into the nature of ambient particulatematerial produced from the source, while the latter would provide samplesuseful for characterizing total emissions including medium volatilityorganics and organometallics.

A classic and deceptively simple appearing approach to samplingorganics is cold trapping. Although not used frequently since the advent ofsolid sorbent trains, cold trapping is encountered occasionally. The twoeffects which often prevent cold trapping from being a viable stacksampling approach are ice formation and microaerosol formation.Microaerosols may be prevented or counteracted if the problem isexpected,22 but ice development in sampling equipment is much moredifficult to deal with. Removal of moisture ahead of the cold trappotentially alters the chemical nature of the sample, and collection oforganics along with moisture in condensate vessels promotes unwantedreactions as well as wall losses. Improved versions of cold trapping, suchas the Kaiser Tube approach,22 may become practical field techniques, butfor now, this collection method is limited to special situations.

A classic, but basically obsolete, sampling device is the solvent filledimpinger or bubbler train. Solvents used in this type of train have variedwidely; some of the standbys have been benzene, toluene, and variousalcohols and glycols.17'34"37 Solvents with higher boiling points aremore resistant to being vaporized from the train by the gas stream, butcause more problems when concentrated during the analysis. Impurities inthe solvents may become a major problem after concentration, especially ifthe material of interest is present in very low concentrations. Thisproblem, in one form or another, is shared by most of the samplingtechniques, but is more severe in this case because of the relatively largeamounts of solvent necessary to adequately scrub even a modest gasstream. Shipping and handling organic solvents in the field areinconvenient and may even be dangerous around combustion sources.

The development of solid sorbent sampling trains has essentially causedthe demise of the organic solvent bubbler train as a popular tool.Nonetheless, this type of device may still produce good results inexperienced hands and should not be viewed completely with disdain.

ARTIFACTS AND INCOMPLETE RECOVERY

The two areas of knowledge related to sampling organics which are themost problematical at present are those of artifact formation andincomplete recovery. Incomplete recovery is often a matter of poortechnique or inadequate planning, but there is convincing evidence that

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certain compounds may be expremely difficult to extract once they havebeen sorbed by flyash or certain other particulate materials.38'39 Onepossible solution to this problem is to operate the filter and othercomponents at the front end of the sampling train at relatively hightemperatures so that high boiling materials are collected on the sorbentresin rather than the filter. The 205°C temperature of the filter andcyclones on the SASS appears to serve this purpose well.

Nothing is accomplished, of course,, by driving the organics onto aninappropriate sorbent from which recovery is unacceptable. Unfortunately,many investigators overlook the importance of knowing recoverycharacteristics of the sorbents they utilize. This type of information isgenerally scattered rather widely throughout the literature, but several ofthe references are quite helpful.7'8-13'17>23'40. Note that data generatedby water analysis investigators may be quite helpful also, especially inpointing out sorbents from which recovery of certain organics isdifficult.10'41-43

Artifact formation is the more difficult of the two problems mentionedearlier. The possibility of artifact formation during sampling has beenknown for at least several years, but has been the subject of a number ofprojects only within the last year or two. On the surface, much of the dataresulting from these studies appear to conflict: one investigator concludesthat a severe artifact problem exists with a given sampling approach, andanother concludes that no problem exists. It is very likely that one reasonfor much apparently conflicting data is the complexity of the problem andthe great number of variables at work in any given sampling situation.Gas stream composition (including moisture), sampling temperatures,collection media, shipping and storage procedures, particulatecomposition, sampling volumes and times, and clean-up procedures, arejust a few important factors, in addition to the chemical nature of theorganic compound of interest. Most of the projects dealing with artifactshave been fairly limited in scope and could not truly cope with all thesevariables. In addition, it is not difficult to find examples of poorly plannedexperiments and indefensible interpretation of data.

Virtually all of the artifacts related work has been carried out on othersampling systems, but has possible implications for users of both SASSand MM5 trains. There is enough evidence of sample reactions onfilters44"46 to draw attention to this possibility. From a purely logicalstandpoint it seems inevitable that certain sources contain highly reactivecomponents that continue to interact during (and perhaps after) samplecollection. To the extent that these reactions would have continued in thestack and the emission plume, the problem is not really serious from apollutant assessment standpoint. However, it is undesirable if the flue

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gases and entrained material either react with elements of the samplingtrain or with each other to produce products not actually emitted fromthe source. The inverse situation may also occur if pollutants actuallyemitted from the source are destroyed by the unwanted reactions and thusnot observed. Again, driving the organics onto the sorbent moduleremoves much of the potential for filter related problems. Fluorocarbonpolymer coated glass filters appear to be preferable for some samplingsystems to minimize reactions,44 but it is not yet clear if this is necessarywith the SASS and MM5 trains.

Although artifact reactions on the filter portion of a train appear to beprimarily between sample stream components, the sorbent portion of acollection system presents several possibilities. In theory, reactionsbetween stream components, and between the resin and streamcomponents, must be of concern. Each category also includes twosubcategories. Reactions may occur between two organic compounds inthe stream or on the resin. Since compounds sorbed on the resin must besomewhat immobilized, and at a lower energy state than if free, thisprobably is less likely than where an organic is attacked by a gaseouspollutant such as nitric oxide or by an acid formed by this substancereacting with condensed water vapor. Again, as with a filter, there must besome sources where some of the components will be reactive enough forthis problem to occur in the sampling train. It also is likely that suchreactive materials would interact in the environment also, although onemay speculate about dilution effects and various other transport and fatephenomena. Investigations are underway to better define the degree ofseverity with respect to certain sources and certain compounds. Atpresent, there is no truly convincing data to demonstrate this particulardifficulty with sorbent systems using XAD-2.

Reactions between the sorbent resin and sample streams have beensomewhat better explored. The first subcategory is that in which the resinpolymer itself is attacked. The work by Neher47 and by Dickson,48 whichdemonstrated oxidative attack on Tenax GC to produce 2,6-diphenyl-hydroquinone, illustrates an example of this artifact reaction. Although thepotential effect of such an artifact is greatly diminished once it isidentified, it may still interfere in a given analytical scheme. In this case,the extent of attack on the Tenax GC does not appear to be sufficient togreatly reduce sorbent efficiency, although it is not difficult to envisionsuch a problem as a worst case occurrence.

Lochmuller demonstrated that both XAD-2 and Tenax GC may besulfonated or nitrated if exposed to relatively severe conditions.14

Fortunately, the effect of either substitution on the sorbent properties ofthe bulk resin was minimal, although measurable.

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A second and somewhat more subtle subclass of reactions betweenstream components and the sorbent is also possible. As mentionedpreviously, the sorbent resin must be cleaned to lower the concentrationof resin blank materials to an acceptable level. Undue heating or othermishandling of the resin may dramatically increase these impurities in theresin. These materials may in turn react with sample stream componentsto produce artifacts not present in the original resin blank. This effect maybe responsible for the mutagenic interference reported by someinvestigators working with XAD-2.15

Because of the organic nature of the sorbent resins, and because theycontain a finite amount of resin blank no matter how well they arecleaned, it is important that the proper analysis blank determinations arealways performed. In this manner, the interference, whether towardchemical or biological analysis, may be controlled to an acceptable level.The worst case potential impact of resin blank transformation artifacts onbiotest systems may be estimated from the resin blank chemical analysis.For example, it might be assumed that all of the low molecular weightaromatics, such as naphthalene and biphenyl, were nitrated during a givensampling run. Utilizing published data on sensitivity of the biotest ofinterest toward the nitrated products,49 the test may be predicted toindicate a positive response because of these products, even in the absenceof sampled material.

SUMMARY AND FURTHER RECOMMENDATIONSPotential problems related to artifact formation, incomplete recovery, andother pitfalls have been discussed. A few suggestions have been made foravoiding some of these difficulties. In addition, the investigator planningstack sampling of organics and subsequent analysis should be sure tofollow several obvious, but often violated, principles:

• Decide in the planning stage what questions require answers. Thenchoose the best sampling system to acquire the necessary data, applyinga thorough understanding of the advantages and disadvantages of eachsystem.

• Choice of an established verified method relieves the investigator of theneed to perform extensive validation and avoids unexpected problemswhich may be worse than the expected disadvantages of existingmethods. When new approaches are required, they should be validatedunder sampling conditions as realistic as possible.

• Even with established methods, follow standard operating procedures.Evaluation of system blanks and quality control should be part ofevery sampling project.

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• It is essential that adequate time and personnel be allowed forplanning, execution, and interpretation of results. Many projects failbecause of the tendency to hurry with the planning, and to interpret theanalysis results perfunctorily when they are finally available. Not onlybe sure that the data from the sampling project answer the questionsoriginally posed, but also carefully extract and analyze any additionalfortuitous information. Point out and explain, if possible,inconsistencies, anomalies, and other problems with the data.

CONCLUSIONS

Sampling of organic materials from stacks is still a relatively new field ofactivity and is still evolving rapidly. There are many pitfalls, especially forthose who bring insufficient resources to bear on sampling tasks. In spiteof all of the potential problems discussed in this paper, however, it isquite possible to obtain high-quality samples of organic materials fromstationary source stacks.

1. D. E. Lentzen, D. E. Wagoner, E. D. Estes and W. F. Gutknecht, "IERL-RTPProcedures Manual: Level 1 Environmental Assessment (Second Edition)," EPA-600/7-78-201, PB 293-795, October 1978.

2. E. D. Estes, F. Smith and D. E. Wagoner, "Level 1 Environmental AssessmentPerformance Evaluation," EPA-600/7-79-032, PB 292-931, February 1979.

3. Arthur D. Little, Inc., "Study on State-of-the-Art of Dioxin from Combustion Sources,"pages A-11 and B-5, American Society of Mechanical Engineers, New York, NY 1981.

4. C. N. Davies and M. Subari, "Inertia Effects in Sampling Aerosols," In Proceedings:Advances in Particle Sampling and Measurement (Asheville, NC, May 1978), EPA-600/7-79-065, PB 293-363, February 1979.

5. R. D. Cadle, Particle Size, Theory and Industrial Applications (Reinhold, New York,1965), p. 103.

6. Energy Resources Corp., "A Review of Concentration Techniques for Trace Chemicals inthe Environment," EPA-560/7-75-002, PB 247-946.

7. J. Adams, D. Menzies and P. Levins, "Selection and Evaluation of Sorbent Resins for theCollection of Organic Compounds," EPA-600/7-77-044, PB 268-559, April 1977.

8. E. C. Gunderson and E. L. Fernandez, "Solid Sorbents for Workplace Sampling,"Chemical Hazards in the Workplace (American Chemical Society, Washington, DC, 1981),pp. 179-193.

9. A. Gold, C. E. Dube and R. B. Perni, Anal Chem. 50, 1839 (1978).10. P. Van Rossum and R. G. Webb, J. Chromatogr. 150, 381 (1978).11. R. F. Gallant, J. W. King, P. L. Levins and J. F. Piecewicz, "Characterization of Sorbent

Resins for Use in Environmental Sampling," EPA-600/7-78-054, PB 284-347, March1978.

12. J. F. Piecewicz, J. C. Harris and P. L. Levins, "Further Characterization of Sorbents forEnvironmental Sampling," EPA-600/7-79-216, PB 80-118763, September 1979.

Dow

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ded

by [

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] at

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13. P. W. Jones, R. D. Giammar, P. E. Strup and T. B. Stanford, Environ. Science Technology10, 80 (1976).

14. C. H. Lochmuller, M. W. Ewalt and E. C. Jensen, Intern. J. Environ. Anal. Chem. 8, pp.37-48 (1980).

15. R. L. Hanson, C. R. Clark, R. L. Carpenter and C. H. Hobbs, Environ. Sci. Technol 15,p. 6 (1981).

16. P. W. Jones and R. J. Jakobsen, "A Critique of Organic Level 1 Analysis," InSymposium Proceedings: Process Measurements for Environmental Assessment (Atlanta,February 1978), EPA-600/7-78-168, PB 290-331, August 1978.

17. P. W. Jones, J. E. Wilkinson and P. E. Strup, "Measurement of Polycyclic OrganicMaterials and Other Hazardous Organic Compounds in Stack Gases, State-of-the-Art,"EPA-600/2-77-202, PB 274-013/2ST, October 1977.

18. J. C. Harris, M. J. Hayes, P. L. Levins and D. B. Lindsay, "EPA/IERL-RTP Proceduresfor Level 2 Sampling and Analysis of Organic Materials," EPA-600/7-79-033, PB 293-800, February 1979.

19. J. E. Knoll, M. A. Smith and M. R. Midgett, "Evaluation of Emission Test Methods forHalogenated Hydrocarbons, Volume II," EPA-600/4-80-003, PB 80-145972, January1980.

20. J. E. Knoll, W. H. Penny and M. R. Midgett, "The Use of Tedlar Bags to ContainGaseous Benzene Samples at Source-Level Concentrations," EPA-600/4-78-057, PB 291-569, September 1978.

21. G. W. Scheil, "Standardization of Stationary Source Method for Vinyl Chloride," EPA-600/4-77-026, PB 271-513, May 1977.

22. A. D. Snyder, F. N. Hodgson, M. A. Kemmer and J. R. McKendree, "Utility of SolidSorbents for Sampling Organic Emissions from Stationary Sources," EPA-600/2-76-201,PB 257-131, July 1976.

23. M. B. Neher, P. W. Jones and P. J. Perry, "Performance Evaluation of Solid SorbentHydrocarbon Sampler," Final Report, EPRI EA-959, Electric Power Research Institute,Palo Alto, CA (1979).

24. C. L. Haile and E. Baladi, "Methods for Determining the Polychlorinated BiphenylEmissions from Incineration and Capacitor and Transformer Filling Plants," EPA-600/4-77-048, PB 276-745, November 1977.

25. W. B. Smith, K. M. Cushing, J. W. Johnson, C. T. Parsons, A. D. Williamson and R. R.Wilson, "Sampling and Data Handling Methods for Inhalable Paniculate Sampling,"EPA-600/7-82-036, May 1982.

26. R. G. Merrill, "SASS Versus Dilution Sampling," Presented at Third Symposium onAdvances in Particulate Sampling and Measurement (Daytona Beach, FL, October1981).

27. F. S. C. Lee, T. J. Prater and F. Ferris, "PAH Emissions from Stratified-Charge VehicleWith and Without Oxidation Catalyst: Sampling and Analysis Evaluation," inPolynuclear Aromatic Hydrocarbons. Edited by P. W. Jones and P. Leber, Ann ArborScience, Ann Arbor, MI, p. 83 (1979).

28. S. J. Swarin and R. I. Williams, "Liquid Chromatographic Determination ofBenzo(a)Pyrene in Diesel Exhaust Particulate: Verification of the Collection andAnalytical Methods," in Polynuclear Aromatic Hydrocarbons, Chemistry and BiologicalEffects. Edited by Alf Bjorseth and Anthony J. Dennis, Battelle Press, Columbus, OH, p.771 (1980).

29. P. R. Cavanaugh, EPA/IERL-RTP Process Measurements Review 1, 4, p. 5 (1979).

30. W. B. Kuykendal, EPA/IERL-RTP Process Measurements Review 2, 2 (1979).

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31. R. I. Mitchell, W. M. Henry and N. C. Henderson, "Fabrication, Optimization, andEvaluation of a Massive Volume Air Sampler of Sized Particulate Matter," EPA-600/4-78-031, June 1978.

32. R. I. Mitchell, W. M. Hardy, N. C. Henderson, R. J. Thompson and R. M. Burton,"Megavolume Respirable Particulate Samples (Mark II)," Presented at 70th AnnualMeeting of the Air Pollution Control Association, Toronto, Ontario, Canada, June 1977.

33. A. R. McFarland, R. W. Bertch, G. L. Fisher and B. A. Prentice, Environ. Sci. Technol.11, 8, 781 (1977).

34. T. S. Hermann, "Development of Sampling Procedures for Polycyclic OrganicMatter and Polychlorinated Biphenyls," EPA-650/2-75-007, PB 243-362, August 1974.

35. R. P. Hangebrauck, D. L. Von Lehmdetl and J. E. Meeker, "Source of PolynuclearHydrocarbons in the Atmosphere," U.S. Public Health Service (now EPA) PublicationNo. 999-AP-33, PB 174-706, 1967.

36. R. I. Stenberg, "Sample Collection Techniques for Combustion Sources—BenzpyreneDetermination," NTIS Publication PB 214-953, 1961.

37. T. L. Ferguson, F. J. Bergman, G. R. Cooper, R. T. Li and F. I. Honea, "Determinationof Incinerator Operating Conditions Necessary for Safe Disposal of Pesticides," EPA-600/2-75-041, PB 251-131, December 1975.

38. W. H. Griest, J. E. Caton, M. R. Guerin, L. B. Yeatts and C. E. Higgins, "Extraction andRecovery of Polycyclic Aromatic Hydrocarbons from Highly Sorptive Matrices Such asFlyash," in Polynuclear Aromatic Hydrocarbons, Chemistry and Biological Effects. Editedby Alf Bjorseth and Anthony J. Dennis, Battelle Press, Columbus, OH, p. 819 (1980).

39. W. H. Griest, L. B. Yeatts and J. E. Caton, Anal. Chem. 52, 199 (1980).40. J. W. Adams, T. E. Doerfler and C. H. Summers, "Effects of Handling Procedures on

Sample Quality," EPA-600/7-78-017, PB 279-910, February 1978.41. J. C. Harris, M. J. Cohen, Z. A. Grosser and M. J. Hayes, "Evaluation of Solid Sorbents

for Water Sampling," EPA-600/2-80-193, PB 81-1006585, October 1980.42. J. E. Wilkinson, P. E. Strup and P. W. Jones, "The Trace Analysis of Organics in

Aqueous Systems Using XAD-2 Resin and Capillary Column GC-MS Analysis," ThirdAnnual Conference of Treatment and Disposal of Industrial Wastewaters and Residues,Houston, TX, April 1978.

43. G. A. Junk, J. M. Richard, M. D. Greiser, D. Witiak, J. K. Witiak, M. D. Argnell, R.Vick, H. J. Svec, J. S. Fritz and G. V. Calder, J. Chromatogr. 99, 745 (1974).

44. F. S. C. Lee, W. R. Pierson and J. Ezike, "The Problems of PAH Degradation DuringFilter Collection of Airborne Particulates: An Evaluation of Several Commonly UsedFilter Media," in Polynuclear Aromatic Hydrocarbons, Chemistry and Biological Effects.Edited by Alf Bjorseth and Anthony J. Dennis, Battelle Press, Columbus, OH, p. 543(1980).

45. J. N. Pitts, K. A. Van Cauwenberghe, D. Grosjean, J. P. Schmid, D. Fitz, W. L. Belser,G. B. Knudson and P. M. Hyrds, Science 202, 515 (1978).

46. M. M. Hughes, D. F. S. Natusch, D. R. Taylor and M. V. Zeller, "ChemicalTransformation of Particulate Polycyclic Organic Matter," in Polynuclear AromaticHydrocarbons, Chemistry and Biological Effects. Edited by Alf Bjorseth and Anthony J.Dennis, Battelle Press, Columbus, OH, p. 1 (1980).

47. M. B. Neher and P. W. Jones, Anal. Chem. 49, 513 (1977).48. W. R. Dickson, H. C. Miller and W. J. Barrett, "High Molecular Weight Organic

Compounds in Coal Fired Power Plant Emissions," Draft Final Report, SouthernResearch Institute, US EPA, ESRL (first reported 1977, Final Draft 1982).

49. D. J. Brusick and R. R. Young, "Level 1 Bioassay Sensitivity," EPA-600/7-81-135, August1981.

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Documents

Stack Sampling for Organic Emission