SW-846 Update V 5021A - 1 Revision 2 

July 2014

METHOD 5021A 

 VOLATILE ORGANIC COMPOUNDS IN VARIOUS SAMPLE MATRICES

 USING EQUILIBRIUM HEADSPACE ANALYSIS

SW-846 is not intended to be an analytical training manual. Therefore, method procedures 

are written based on the assumption that they will be performed by analysts who are formally 

trained in at least the basic principles of chemical analysis and in the use of the subject 

technology. 

In addition, SW-846 methods, with the exception of required method use for the analysis of 

method-defined parameters, are intended to be guidance methods which contain general 

information on how to perform an analytical procedure or technique which a laboratory can use 

as a basic starting point for generating its own detailed standard operating procedure (SOP), 

either for its own general use or for a specific project application. The performance data included 

in this method are for guidance purposes only, and are not intended to be and must not be used 

as absolute QC acceptance criteria or for the purpose of laboratory accreditation. 

1.0 SCOPE AND APPLICATION 

Please see Appendix A at the end of this document for a summary of changes from the 

previous version. 

1.1 This method describes equilibrium-based static headspace preparation of volatile 

organic compounds (VOCs) in soil/sediment, solid waste, aqueous and water-miscible liquid 

samples for determination by gas chromatography (GC) or gas chromatography/mass 

spectrometry (GC/MS). This method is applicable to a wide range of organic compounds that 

have sufficiently high volatility to be effectively removed from samples using the described 

conditions. While the method is designed for use on samples containing low levels of VOCs or 

aqueous dilutions thereof to be analyzed by direct vapor partitioning, a solvent extraction and 

extract introduction procedure is also described for solid samples containing high concentrations 

of VOCs or for oily materials that may not be appropriate for the low level technique. This 

preparation method is intended to be combined with a determinative method such as Methods 

8015, 8021 or 8260. This preparation method is appropriate for the compounds listed below, and 

it may also be appropriate for other VOCs included in the determinative method (e.g., Sec. 1.1 of 

8260), provided method performance is demonstrated to be acceptable for the intended use of 

the data. 

Compound CAS No.a Response Stability

Acetone 67-64-1 ws hs

t-Amyl alcohol (TAA) 75-85-4 nd hs

t-Amyl ethyl ether (TAEE) 919-94-8 nd nd

t-Amyl methyl ether (TAME) 994-05-8 nd hs

Benzene 71-43-2 c hs

Bromochloromethane 74-97-5 p hs

Bromodichloromethane 75-27-4 c ms

Bromoform 75-25-2 p hs

Bromomethane 74-83-9 c hvs
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Compound CAS No.a Response Stability

t-Butyl alcohol (TBA) 75-65-0 ws nd

Carbon tetrachloride 56-23-5 c hvs

Chlorobenzene 108-90-7 c hvs

Chloroethane 75-00-3

c

c ms

Chloroform 67-66-3 c hs

Chloromethane 74-87-3 c hvs

Dibromochloromethane 124-48-1 p nd

1,2-Dibromo-3-chloropropane 96-12-8 p ms

1,2-Dibromoethane 106-93-4 p hs

Dibromomethane 74-95-3 p hs

1,2-Dichlorobenzene 95-50-1 c hs

1,3-Dichlorobenzene 541-73-1 c ms

1,4-Dichlorobenzene 106-46-7 c ms

Dichlorodifluoromethane 75-71-8 c hs

1,1-Dichloroethane 75-34-3 c hs

1,2-Dichloroethane 107-06-2 p hs

1,1-Dichloroethene 75-35-4 c hvs

trans-1,2-Dichloroethene 156-60-5 c ms

1,2-Dichloropropane 78-87-5 c hs

Diisopropyl ether (DIPE) 108-20-3 c hs

Ethanol 64-17-5 p nd

Ethylbenzene 100-41-4 c hvs

Ethyl tert-butyl ether (ETBE) 637-92-3 c hs

Hexachlorobutadiene 87-68-3

c

c ms

Isopropanol 67-63-0 ws nd

Methyl tert-butyl ether (MTBE) 1634-04-4 c hs

Methylene chloride 75-09-2 c hs

Naphthalene 91-20-3 p ms

Styrene 100-42-5 c hvs

1,1,1,2-Tetrachloroethane 630-20-6 c hs

1,1,2,2-Tetrachloroethane 79-34-5 p nd

Tetrachloroethene 127-18-4 c ms

Toluene 108-88-3 c hs

1,2,4-Trichlorobenzene 120-82-1 c hs

1,1,1-Trichloroethane 71-55-6 c ms

1,1,2-Trichloroethane 79-00-5 p hs

Trichloroethene 79-01-6 c ms

Trichlorofluoromethane 75-69-4 c ls

1,2,3-Trichloropropane 96-18-4 p ls

Vinyl chloride 75-01-4 c hvs

o-Xylene 95-47-6 c hvs

m-Xylene 108-38-3 c hvs

p-Xylene 106-42-3 c hvs

Gasoline range organics

a

 Chemical Abstracts Service Registry Number 

 
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c = Response in reagent water is acceptable; similar response expected in matrix modifier solution (< 50% 

improvement). 

p = Response in matrix modifier solution expected to improve >50% compared to reagent water; Use of 

matrix modifier is recommended. 

ws = Highly water soluble analyte. Method sensitivity expected to be poorer than for other analytes due to poor 

partitioning into headspace; matrix modifier expected to be critical for acceptable method performance. 

nd = Not determined 

hs = High stability in preserved water samples (> 60 days). Longer holding times may be appropriate, see 

Method 5035, Appendix A, Table A.1 footnote and Ref. 47 for additional information 

ms = Medium stability in preserved water samples (15 - 60 days). Longer holding times may be appropriate, 

see Method 5035, Appendix A, Table A.1 footnote and Ref. 47 for additional information 

ls = Low stability in preserved water samples (< 14 days), analyses should be performed as soon as possible. 

May be degraded if acid preserved. 

hvs = Highly variable stability depending on the sample matrix. Longer holding times may be appropriate, see 

Method 5035, Appendix A, Table A.1 footnote and Ref. 47 for additional information.

1.2 The following compounds may also be analyzed by this procedure or may be used 

as surrogates: 

Compound CAS No.a Response Stability

Bromobenzene 108-86-1 c nd

n-Butylbenzene 104-51-8 c nd

sec-Butylbenzene 135-98-8 c nd

tert-Butylbenzene 98-06-6 c nd

2-Chlorotoluene 95-49-8 c nd

4-Chlorotoluene 106-43-4 c nd

cis-1,2-Dichloroethene 156-59-4 c hs

1,3-Dichloropropane 142-28-9 c nd

2,2-Dichloropropane 590-20-7 c nd

1,1-Dichloropropene 563-58-6 c nd

Isopropylbenzene 98-82-8 c nd

4-Isopropyltoluene 99-87-6 c nd

n-Propylbenzene 103-65-1 c nd

1,2,3-Trichlorobenzene 87-61-6 c nd

α,α,α-Trifluorotoluene 98-08-8 nd nd

1,2,4-Trimethylbenzene 95-63-6 c nd

1,3,5-Trimethylbenzene 108-67-8 c nd

a

 Chemical Abstracts Service Registry Number 

1.3 In order to produce quantitative data with this technique, all of the quality control 

criteria described in the determinative method and/or Method 8000 should be met. Alternatively, 

this method may be utilized as a screening protocol. If used for screening, semi-quantitative or 

estimated sample results may be obtained with minimal calibration and quality control, such as a 

reagent blank and a single calibration standard. 

As with any preparative method for volatiles, screening samples prior to low level analysis 

may help minimize problems associated with carryover contamination from samples that contain 

very high concentrations of volatiles above the calibration range of the determinative method. In 

addition, because removing a sample aliquot from a container may compromise the integrity of 

the sample, multiple sample aliquots should be collected to allow for screening and re-analysis. 
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1.4 In order to accommodate analysis of a variety of sample matrices and VOCs, a 

matrix modifier (Sec. 7.7) is generally recommended to be used with this method. The matrix 

modifier is a water soluble salt solution that is added to each sample and standard vial prior to 

analysis. The matrix modifier solution acts to increase the VOCs mass transfer into the 

headspace of the vial. The principal benefits of using the matrix modifier are: 

1) better response and reproducibility of the VOCs that do not otherwise partition efficiently 

into the headspace of the vial from the aqueous phase (identified with ‘p’ or ‘ws’ in the 

response column in the table in Sec. 1.1); and 

2) less potential for measurement bias resulting from aqueous activity differences between 

standards and samples. 

Measurement bias results from VOCs partitioning into the vial headspace differently in a 

sample than in the calibration standards. Some potential sources of measurement bias and the 

anticipated effects of the matrix modifier on these sources of bias are described below. 

1.4.1 Aqueous field samples containing high dissolved solute concentrations: 

At higher solute concentrations substantially larger fractions of some VOCs partition 

into the headspace leading to high bias in the determined concentration. The VOCs most 

prone to high bias measurement at higher dissolved solute concentrations are also the 

VOCs whose responses are most substantially improved in the matrix modifier solution 

relative to reagent water (identified with ‘p’ or ‘ws’ in the response column in the tables in 

Sec. 1.1). The VOCs identified with ‘c’ in the response column in the analytes table in Secs. 

1.1 and 1.2 are not as subject to this source of measurement bias. The matrix modifier is 

used to normalize the solute concentration between samples and calibration standards, 

thereby minimizing this source of bias. 

1.4.2 Aqueous field samples containing water miscible organic component: 

The presence of a water miscible organic component (e.g., cosolvent or surfactant) 

may result in low bias measurement of VOCs with high octanol-water partitioning 

coefficients (e.g., C3 and C4 alkylbenzenes, trichlorobenzenes and naphthalene), while 

recovery of the lighter and more highly water soluble VOCs is unlikely to be strongly 

affected unless the proportion of the water miscible organic component in the sample is 

high. The matrix modifier helps improve the recovery of VOCs whose partitioning into the 

headspace is most strongly affected by this source of measurement bias. 

1.4.3 Field samples containing a water immiscible component: 

For samples with a separate water immiscible phase, partitioning of VOCs into the 

headspace competes with the water immiscible phase. While addition of the matrix modifier 

has a favorable effect on partitioning of VOCs into the headspace from the aqueous phase, 

it may also increase partitioning into the water immiscible phase(s) (e.g., soils with >1% 

organic matter, oily materials), potentially exaggerating matrix effects relative to the 

calibration standards. This matrix effect is more pronounced for VOCs with higher 

octanol-water partitioning coefficients when the matrix modifier is used for the analysis. 

Recovery of the lighter and more water soluble VOCs is expected to be less affected. 

For complex samples, more than one of these types of matrix effects may be relevant, and 

a compromise may have to be made for data quality of some analytes in order to obtain reliable 

data for the analytes deemed most critical for the project. For simple sample matrices and VOCs 
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not expected to subject to measurement bias (e.g., analysis of BTEX and other alkylbenzenes in 

surface water samples) the matrix modifier solution may be omitted. 

1.5 This method, in conjunction with determinative Method 8015 (GC/FID), may be 

used for analysis of the aliphatic hydrocarbon fraction in the light ends of petroleum 

hydrocarbons, e.g., gasoline. For the aromatic fraction (BTEX), use this method and Method 

8021 (GC/PID). A total determinative analysis of gasoline and other volatile petroleum 

hydrocarbon fractions may be obtained using Method 8021 in series with Method 8015. If MS 

detection is desired for these target analytes, Method 8260 (Volatile Organic Chemicals by 

GC/MS) may be used. 

1.6 Measurements of VOCs using this method may be subject to bias from several 

sources, including differences in partitioning of VOCs between the aqueous phase and 

headspace in samples relative to standards, differences in headspace volume in samples 

relative to standards, and adsorption of VOCs to surfaces or absorption into compatible phases 

(e.g., soil organic matter). Measurement bias is monitored through internal standard, surrogate, 

and matrix spike recovery when appropriate for the project and determinative method. Use of the 

matrix modifier (Sec. 7.7) will help minimize measurement bias resulting from differences in 

partitioning behavior of VOCs in samples relative to standards. Measurement bias resulting from 

adding solid material to the vial, which changes the headspace volume in the sample relative to 

the calibration standards, is expected to be negligible as long as the volume of material is small 

relative to the headspace volume. The magnitude of this bias may be reduced by adding a 

similar volume of solid organic-free control material to calibration standards as the volume of the 

bulk material being tested. Measurement bias related to sorption of VOCs to solid samples with 

fine particle size distributions and/or significant organic content may be substantial. The 

magnitude of this bias may be reduced by analyzing a smaller amount of material or by solvent 

extraction (Sec. 11.4). 

1.7 Prior to employing this method, analysts are advised to consult the base method for 

each type of procedure that may be employed in the overall analysis (e.g., Methods 3500, 3600, 

5000, and 8000) for additional information on quality control procedures, development of QC 

acceptance criteria, calculations, and general guidance. Analysts also should consult the 

disclaimer statement at the front of the manual and the information in Chapter Two for guidance 

on the intended flexibility in the choice of methods, apparatus, materials, reagents, and supplies, 

and on the responsibilities of the analyst for demonstrating that the techniques employed are 

appropriate for the analytes of interest, in the matrix of interest, and at the levels of concern. 

 

In addition, analysts and data users are advised that, except where explicitly specified in a 

regulation, the use of SW-846 methods is not mandatory in response to Federal testing 

requirements. The information contained in this method is provided by EPA as guidance to be 

used by the analyst and the regulated community in making judgments necessary to generate 

results that meet the data quality objectives (DQOs) for the intended application. 

1.8 This method is restricted to use by, or under supervision of, appropriately 

experienced and trained analysts for volatile organic analysis in general and specifically the use 

of equilibrium headspace devices interfaced to the determinative method selected by the analyst. 

Each analyst must demonstrate the ability to generate acceptable results with this method. 

2.0 SUMMARY OF METHOD 

2.1 Sample collection and headspace vial preparation 
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2.1.1 Water samples – A 40-mL volatile organic analyte (VOA) vial is filled to 

capacity and capped so no headspace remains in the vial. The water sample may be 

preserved at the time of sampling by addition of a chemical preservative (e.g., hydrochloric 

acid solution, solid sodium bisulfate or solid trisodium phosphate) to the vial. At the 

laboratory, that vial is sub-sampled into a headspace vial, and internal standards and 

surrogates are added, if used. The matrix modifying solution (Sec. 7.7) should be added to 

the headspace vial during subsampling if used for the analysis. 

2.1.2 Low concentration soil samples -- Approximately 2 g of soil is collected 

with an appropriately sized coring tool and placed in a pre-weighed crimp seal or screw top 

glass headspace vial, and then the vial is sealed. Depending on the analytes of interest, the 

soil sample may be preserved by addition of a pH modifying chemical preservative (e.g., 

sodium bisulfate, trisodium phosphate) prior to sealing the sample vial, and the matrix 

modifying solution (Sec. 7.7) should also be added prior to capping the vial if used for the 

analysis. Sec. 8.3.3 also describes the use of a sealable coring device as an alternative 

sampling technique, which may simplify collection and handling of soils in the field. 

Surrogates and internal standards may be added to the vials during sampling or at the 

laboratory. If the matrix modifying solution is used for the analysis and was not added to 

sample vials in the field, it should be added when any surrogates and internal standards 

are added at the laboratory. Adding the matrix modifying solution or reagent water to a vial 

after adding the sample may cause loss of gas phase VOCs from the container due to 

displacement of a portion of the vial headspace. Adding the matrix modifying solution (Sec. 

7.7) to the vial prior to adding the sample and sealing quickly will help to limit loss of VOCs 

from the sample container and maintain sample representativeness. 

NOTE: The choice of chemical preservative(s) will depend on the VOCs that will be 

measured in the samples and to some extent on the sample matrix. The matrix 

modifying solution acts as a chemical preservative, but it does not otherwise alter 

the sample pH and may not protect against degradation of some classes of VOCs, 

including hydrolysis of ethers or dehydrohalogenation of chlorinated aliphatics 

(Sec. 4.7). Sodium bisulfate has also been identified as inappropriate for use as a 

preservative for calcareous soils, which may off-gas CO2 when exposed to acid 

due to chemical reaction with any carbonate salts, which may cause loss of VOCs 

from the container or build up pressure once the container is sealed, potentially 

leading to rupture. 

 2.1.3 High concentration soils or other solid materials – A representative portion 

of soil is collected with an appropriately sized coring tool and placed in a pre-weighed glass 

VOA vial, and then the vial is sealed. The soil sample may be preserved by addition of 

extraction solvent (e.g., methanol) at the time of sampling or upon receipt by the laboratory. 

At the laboratory, the methanol extract is then diluted with the matrix used for the 

calibration standards (organic-free reagent water or the matrix modifying solution) and 

analyzed as an aqueous sample. Sec. 8.3.3 also describes the use of an air-tight sealable 

coring device as an alternative sample collection technique that may be useful, and Sec. 

A.6 of SW-846 method 5035A provides additional information pertaining to methanol 

extraction of soils. 

NOTE: Surrogate compounds may either be spiked into the solvent at the time of 

extraction or into reagent water containing an aliquot of the extract prior to 

analysis. Since the surrogate recovery data from these two options provides 

assurances of either extraction or analytical efficiencies, the decision as to 
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when the surrogates are added depends on what questions need to be 

answered for a given sample matrix and the intended uses of the data.

2.2 For soil samples, additional aliquot(s) are collected in VOA vials for dry weight 

determination.

2.3 In the laboratory, the vials are rotated to allow for diffusion of internal standards and 

surrogates throughout the matrix. The vials are placed in the autosampler carousel of the 

headspace analyzer and maintained at room temperature. Approximately 1 hr prior to analysis, 

the individual vials are moved to a heated zone and mechanically agitated while the elevated 

temperature is maintained, allowing the VOCs to equilibrate between the headspace, liquid and 

any solid phases in the vial. 

2.4 The autosampler then pressurizes the vial with helium and forces a portion of the 

headspace gas mixture into the gas chromatograph through a heated transfer line, either 

passing through the GC inlet or directly connected to the analytical column via an inert, low dead 

volume connector. 

2.5 Determinative analysis is performed using the appropriate GC or GC/MS method. 

Any chemical preservative and matrix modifier added to the field samples should also be added 

to the calibration standards and other QC samples. 

3.0 DEFINITIONS 

 Refer to Chapter One and the manufacturer's instructions for definitions that may be 

relevant to this procedure. 

4.0 INTERFERENCES 

4.1 Solvents, reagents, glassware, and other sample processing hardware may yield 

artifacts and/or interferences to sample analysis. All of these materials must be demonstrated to 

be free from interferences under the conditions of the analysis by analyzing method blanks. 

Specific selection of reagents and purification of solvents by distillation may be necessary. Refer 

to each method to be used for specific guidance on quality control procedures and to Chapter 

Four for general guidance on the cleaning of glassware. Also refer to the determinative methods 

to be used for information regarding potential interferences. 

4.2 Volatile organic analyses are subject to major interference problems because of the 

prevalence of volatile organics in a laboratory. See Method 5000 for common problems and 

precautions to be followed. 

4.3 Samples can be contaminated by diffusion of volatile organics (particularly 

methylene chloride and fluorocarbons) through the septum seal of the sample vial during 

shipment and storage. A trip blank, prepared from an appropriate organic-free matrix and sample 

container and carried through sampling and handling protocols, serves as a check on such 

contamination. 

4.4 The sample matrix itself can cause severe interferences by one of several 

processes or a combination of these processes. These include, but are not necessarily limited to, 

the absorption potential of the soil, the biological activity of the soil, and the actual composition of 

the soil. Soils high in organic matter or oily material and organic sludge wastes inhibit the 
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partitioning of the volatile target analytes into the headspace. Therefore, analyte recovery by 

direct vapor partitioning may be low and will depend on the properties of the particular chemical. 

This matrix effect can be difficult, if not impossible, to overcome. It is recommended that 

surrogates or additional deuterated compounds (for GC/MS methods) be added to a matrix and 

analyzed to determine the percent recovery of these compounds. The calculated percent 

recovery can give some indication of the degree of the matrix effect, but not necessarily correct 

for it. Alternatively, the use of the high-concentration procedure in this method should minimize 

the problem with oily waste and other organic sludge wastes.

4.5 Contamination by carryover can occur whenever high concentration and low 

concentration samples are analyzed sequentially. Where practical, samples with unusually high 

concentrations of analytes should be followed by an analysis of one or more method blanks or 

instrument blanks to check for cross-contamination. If the target compounds present in an 

unusually concentrated sample are also found to be present in subsequent samples, the analyst 

must demonstrate that the compounds are not affected by carryover contamination. 

Conversely, if those target compounds are not present in the subsequent sample, then the 

analysis of a blank is not necessary.

4.6 The laboratory where volatiles analysis is performed should be free of any solvents 

that may interfere with the analysis. Special precautions must be taken when analyzing for 

methylene chloride. The analytical and sample storage areas should be isolated from all 

atmospheric sources of methylene chloride. Otherwise, random background levels can result. 

Since methylene chloride can permeate through polytetrafluoroethylene (PTFE) tubing, all GC 

carrier gas lines and purge gas plumbing should be constructed of stainless steel or copper 

tubing. Laboratory workers' clothing previously exposed to methylene chloride fumes during 

common liquid/liquid extraction procedures can contribute to sample contamination. The 

presence of other organic solvents in the laboratory where volatile organics are analyzed can 

also lead to random background levels, and the same precautions must be taken.

4.7 Ethers in acidic samples (i.e., samples with a pH < 7) will hydrolyze at the higher 

temperatures used in this method. As such, basic preservatives should be used if the target 

analytes are ethers or the alcohols that those ethers would form if hydrolyzed. Strong bases may 

catalyze substitution and elimination reactions that can occur if halogenated compounds are 

present. Halogenated aliphatic VOCs are particularly susceptible to dehydrohalogenation 

reactions in neutral to basic conditions at elevated temperature such as with a heated sample 

preparation procedure as is described here. Accordingly, acidic preservatives may be necessary 

to prevent dehydrohalogenation if halogenated aliphatic VOCs are analytes of interest or their 

presence is suspected and their transformation products are of interest. Acetone has also been 

observed to form in high organic content soils preserved with sodium bisulfate (Sec. A.8 in the 

Appendix of method 5035A provides more information). The chemical reactivity introduced by 

the preservative should be monitored by analyzing a matrix spike of a field sample with each 

batch. The spiking solution should contain all analytes which the client intends to monitor. 

5.0 SAFETY 

This method does not address all safety issues associated with its use. The laboratory is 

responsible for maintaining a safe work environment and a current awareness file of OSHA 

regulations regarding the safe handling of the chemicals included in this method. A reference file 

of material safety data sheets (MSDSs) should be available to all personnel involved in these 

analyses. 
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6.0 EQUIPMENT AND SUPPLIES 

The mention of trade names or commercial products in this manual is for illustrative 

purposes only, and does not constitute an EPA endorsement or exclusive recommendation for 

use. The products and instrument settings cited in SW-846 methods represent those products 

and settings used during method development or subsequently evaluated by the Agency. 

Glassware, reagents, supplies, equipment, and settings other than those listed in this manual 

may be employed provided that method performance appropriate for the intended application 

has been demonstrated and documented. 

This section does not list all common laboratory glassware (e.g., beakers and flasks) that 

might be used. 

6.1 Headspace containers - Clear glass, 22-mL vials equipped with PTFE-lined septa 

that are compatible with the analytical system. Vials of other sizes may be employed, provided 

that they can be hermetically sealed and equipped with suitable septa. Ideally, the vials and 

septa should have a uniform tare weight. The septa should be unpunctured, as piercing the 

PTFE face may allow target analytes to diffuse into and adsorb to the silicone backing material. 

New, disposable vials may be used without pretreatment provided they are demonstrated to be 

clean through method blank analysis. Store the vials in an area free of organic solvents. If vials 

are suspected of being a source of contamination, first wash the vials in a detergent solution, 

then thoroughly rinse with tap water followed by distilled water, and finally dry the vials in an oven

at 105 °C for 1 hour. Allow vials to cool prior to use. 

6.2 Headspace system - The operating conditions listed in Sec. 11.0 are those selected 

for the equipment used in developing this method. See Reference #1 in Sec. 16 for more detail. 

Other equipment and conditions may be employed, provided that the laboratory demonstrates 

performance for the analytes of interest using the determinative method appropriate for the 

intended application. The system used must meet the following specifications: 

6.2.1 The system must be capable of holding samples at elevated temperatures 

and establishing a reproducible equilibrium between a wide variety of sample types and the 

headspace. 

 6.2.2 The system must be capable of accurately transferring a representative 

portion of the headspace into a gas chromatograph fitted with a capillary column without 

adversely affecting the chromatography or the detector. 

6.3 Field sampling equipment 

6.3.1 Water samples - Clear or amber 40 mL volatile organic analysis (VOA) 

vials with screw-cap PTFE lined vials. 

6.3.2 Soil samples 

6.3.2.1 A soil sampler which delivers at least 2 g of soil is necessary, 

e.g., Purge and Trap Soil Sampler Model 3780SPT (Associated Design and 

Manufacturing Company, 814 North Henry Street, Alexandria, VA 22314), or 

equivalent. 

6.3.2.2 An automatic syringe or bottle top dispenser calibrated to 

deliver a 10.0 mL liquid volume. 
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6.3.2.3 Crimping tool for headspace vials - If using screw-top vials, this 

is not needed. 

6.3.2.4 VOA vials (22, 40 or 60 mL) with PTFE faced septa and 

crimp-seal caps or screw-top caps. These vials will be used for sample screening, 

high concentration analysis (if needed) and dry weight determination. 

6.3.2.5 Sealable, air-tight coring device – A soil coring device with an 

internal volume appropriate for approximately 2 g of sample for direct vapor 

partitioning analysis, or other size as appropriate for high level analysis, equipped 

with an o-ring seal or equivalent air-tight sealing mechanism, constructed of 

materials that will not absorb or react with the target chemicals of interest and with a 

cross-sectional diameter appropriate for a VOA vial compatible with the headspace 

analyzer or for use with methanol extraction. 

6.4 Miscellaneous equipment 

6.4.1 For the preparation of blanks, standards and water samples, it is 

necessary to have the crimping tool addressed in 6.3.2.3 available in the laboratory. 

6.4.2 Graduated microsyringes for standard preparation and for addition of 

internal standard and surrogate spiking solutions. 

6.4.3 5-mL glass hypodermic syringes with Luer-LokTM tip (other sizes are 

acceptable depending on sample volume used). 

7.0 REAGENTS AND STANDARDS 

7.1 Reagent-grade chemicals must be used in all tests. Unless otherwise indicated, it is 

intended that all reagents conform to the specifications of the Committee on Analytical Reagents 

of the American Chemical Society, where such specifications are available. Other grades may be 

used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use 

without lessening the accuracy of the determination. Reagents should be stored in glass to 

prevent the leaching of contaminants from plastic containers. 

7.2 Organic-free reagent water - Reagent water must be interference free. All 

references to water in this method refer to organic-free reagent water, unless otherwise 

specified. 

7.3 Methanol - Pesticide quality or equivalent. Store away from other solvents. 

Purchase in small quantities (1 Liter size or less) to minimize shelf life to reduce potential for 

contamination. 

7.4 See the determinative method and Method 5000 for guidance on the preparation of 

stock standards and a secondary standard for internal standards, calibration standards, and 

surrogates. 

7.4.1 Calibration spiking solutions - Prepare five or more spiking solutions in 

methanol or water that contain all the target analytes. The concentrations of the calibration 

solutions should be such that the addition of 1.0 μL of each to the headspace vials will 

bracket the analytical range of the detector. Alternatively, calibration standards may be 

prepared by adding different volumes of one or more stock solutions provided that the 
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linearity of the calibration is not affected by the methanol content. For analysis of methanol 

extracts, it may be appropriate to calibrate surrogates at multiple concentration levels as 

well to demonstrate calibration linearity at the surrogate level measured in diluted extracts. 

7.4.2 Internal and surrogate standards – Follow the recommendations of the 

determinative method for the selection of internal and surrogate standards. Selection and 

use of surrogates with physical properties similar to the classes of target analytes that are 

of interest for the project will provide more meaningful sample-specific quality assurance 

information. A concentration of 20 mg/L in methanol for both internal and surrogate 

standards may be used for spiking each sample. The concentration may vary depending on 

the relative sensitivity of the detector used in the determinative method. If determination is 

by GC, external standard calibration may be preferred and the internal standard omitted. 

7.5 Blank preparation - Transfer 10.0 mL of matrix modifying solution (Sec. 7.7) or 

reagent water to a sample vial. Inject the necessary amounts of internal standards and surrogate 

compounds under the surface of the water in the headspace vial, and seal the vial. Place in the 

autosampler and analyze in the same manner as an unknown sample. Any chemical 

preservative and/or matrix modifier added to the field samples must also be included in the 

blank(s). 

7.6 Preparation of calibration standards - Prepare calibration standards in the same 

manner as blanks (Sec. 7.5), adding the standard spiking solution(s) prepared in Sec. 7.4.1 in 

the same manner that internal standards and surrogates are added. Any chemical preservative 

and/or matrix modifier added to the field samples should also be included in the calibration 

standards. 

7.7 Preparation of matrix-modifying solution - Add 180 g of ACS-grade sodium chloride 

(NaCl) to 500 mL of reagent water. Mix well until all components are dissolved. Other water 

soluble salts may be appropriate. The matrix modifier solution should not affect the pH of the 

sample to the extent that preservation or analyte stability is compromised. Analyze a 10.0-mL 

portion from each batch according to Sec. 7.5 to verify that the solution is free of contaminants. 

Store the prepared matrix-modifying solution in a sealed bottle in an area free of organic 

chemicals at ≤6 °C. 

CAUTION: The matrix modifying solution may not be appropriate for analysis of some VOCs in 

soil samples having high organic matter content. 

7.8 Preparation of chemical preservative for low level (vapor partitioning) analysis - The 

preservative should be chosen based on the analytes of interest and should be mixed with the 

sample at the time of sampling. 

7.8.1 If a basic preservative is chosen, 100 mg of ACS-grade trisodium 

phosphate dodecahydrate (TSP; Na3PO4•12H2O) should be added to either a 22-mL 

headspace vial or a 40-mL water sample vial to raise the pH above 10. 

7.8.2 If an acidic preservative is chosen, 2-3 drops of 6N hydrochloric acid (HCl) 

should be added to a 40-mL water sample vial. The HCl solution should be prepared by 

the 1:1 dilution of ACS-grade concentrated HCl. For acid preservation of a soil sample, 1 g 

of solid, ACS-grade sodium bisulfate (NaHSO4) should be added to each 22-mL vial. 

CAUTION: If samples containing MTBE, TAME, ETBE or other fuel ethers have been 

acid preserved with either sodium bisulfate or hydrochloric acid, these 

samples must be adjusted to pH >10 with trisodium phosphate 
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dodecahydrate (TSP) (Sec. 7.8.1) prior to initiation of the headspace 

analysis. 

8.0 SAMPLE COLLECTION, PRESERVATION, AND STORAGE 

Sample collection, preservation and storage requirements may vary by EPA program and 

may be specified in a regulation or project planning document that requires compliance 

monitoring for a given contaminant. Where such requirements are specified in the regulation, 

follow those requirements. In the absence of specific regulatory requirements, use the following 

information as guidance in determining an appropriate plan for sample collection, preservation 

and storage prior to sample collection and analysis. 

8.1 Refer to Chapter Four and Method 5035A or general sample collection information. 

All samples should be stored in capped vials at ≤6 °C in an area free of solvent fumes If any 

evidence of leakage is found, the sample can be considered corrupted and should be discarded. 

Pre-testing of a representative soil or aqueous sample, prior to collection, with acid or 

bisulfate may show effervescence if carbonaceous materials are present. If bubbling occurs 

during chemical preservation, an increased potential for loss of volatile constituents exists and 

samples should therefore be collected without preserving with acid or bisulfate. 

8.2 Water samples - Fill the 40-mL vial and, according to the analyte list to be analyzed, 

chemically preserve the sample (Sec. 7.8) as necessary. Ensure that there is no headspace in 

the vial and seal it. At least two vials should be collected per sample and more may be necessary 

for duplicate and MS/MSD analyses, if desired. Transfer of the sample into a headspace vial and 

the addition of the matrix modifier and standards should be performed at the laboratory. 

In general, liquid samples should be poured into the vial without introducing any air bubbles 

into the sample as the vial is being filled. Should bubbling occur as a result of violent pouring, the

sample should be poured out and the vial refilled. The vials should be completely filled at the 

time of sampling, so that when the septum cap is fitted and sealed, and the vial inverted, no 

headspace is visible. The sample should be hermetically sealed in the vial at the time of 

sampling, and not opened prior to analysis to preserve its integrity. 

Due to differing solubility and diffusion properties of gases in liquid matrices at different 

temperatures, it is possible for the sample to generate some headspace during storage. This 

headspace will appear in the form of micro bubbles and should not invalidate a sample for 

volatiles analysis. The diameter of any bubble caused by degassing upon cooling the sample 

should not exceed 5 - 6 mm. When a bubble is present, also inspect the cap and septum to 

ensure that a proper seal was made at the time of sampling. The presence of a macro bubble in 

a sample vial generally indicates either improper sampling technique or a source of gas evolution 

within the sample. The latter case is usually accompanied by a buildup of pressure within the vial, 

(e.g. carbonate-containing samples preserved with acid). Studies conducted by the USEPA 

(EMSL-Ci, unpublished data) indicate that "pea-sized" bubbles (i.e., bubbles not exceeding 1/4 

inch or 6 mm in diameter) did not adversely affect volatiles data. These bubbles were generally 

encountered in wastewater samples, which are more susceptible to variations in gas solubility 

than are groundwater samples. 

8.3 Soil samples - Three alternative procedures are presented below for collection of 

soil samples in headspace sample vials. Sec. A.7 in the appendix of method 5035A describes 

some additional alternatives that may also be appropriate. The choice between these 

alternatives should be based on knowledge of the field conditions, the organic carbon content of 
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the soil, the specific volatile analytes and concentration levels of interest, and the intended use of

the analytical results. For low level analysis by direct vapor partitioning, 3 or 4 replicate samples 

should be collected from each sampling point to allow for reanalysis, while duplicate samples 

may be sufficient for high level analysis because the solvent extract can be diluted and 

reanalyzed. Additional sample replicates should also be collected for duplicate and MS/MSD 

analyses, as well as separate portions for dry weight determination. If samples will be analyzed 

by the low level method but have the potential to contain high levels of VOCs, samples may be 

collected for both low level and high level analysis. This is due to the difficulty of diluting samples 

prepared for low level analysis once they are sealed in the vials. 

8.3.1 Sampling directly into prepared headspace vials for low level analysis: 

Soil may be sampled by addition to a prepared vial that contains 10.0 mL of matrix 

modifier or reagent water, plus any necessary pH altering chemical preservative. The 

preservative and matrix modifier or water are added to the vial prior to sampling in order to 

prevent displacing a portion of the headspace from the vial, along with any associated 

VOCs . The matrix modifying solution has the additional benefits of reducing the 

biodegradation potential of the sample matrix and increasing partitioning of the VOCs into 

the vial headspace from water. Problems related to contamination of the aqueous solution 

in a field sampling situation and incorrect measurement and transfer into the sample vials 

can be minimized by adding it to the vials at the laboratory and sealing them prior to 

sending them to the field. Samples should be obtained and transferred to a vial rapidly after 

sampling (<10 seconds) to minimize volatilization losses. In order to estimate the sample 

mass added, the vial, cap and any added solutions should be tared and the masses 

recorded prior to and after adding a soil sample to the vial. If the vials were not prepared in 

the laboratory prior to sampling, the analyzing laboratory must be made aware of the 

identities and amounts of any reagents added to each vial in the field. 

8.3.1.1 Use standard glass headspace vials with PTFE faced septa. 

 8.3.1.2 Using the soil sampler (Sec. 6.3.2.1), add 2-3 cm 

(approximately 2 g) of the soil sample to a tared headspace vial containing 10.0 mL 

of matrix modifier or reagent water and any pH modifying chemical preservative 

used. The samples should be introduced into the vials gently to reduce agitation 

which might drive off volatile compounds. Seal immediately with the PTFE side of 

the septum facing toward the sample. 

8.3.2 Sampling directly into empty or prepared headspace vials for high level 

analysis: 

 If high concentrations of VOCs are expected (greater than 200 μg/kg), collection of 

the sample in an empty headspace vial or a vial containing methanol is appropriate for use 

with the high concentration procedure described in Sec. 11.4.

8.3.2.1 Use standard 22-mL crimp-cap or screw-top glass headspace 

vials with PTFE faced septa (other vials may be used, as described in Sec. 6.1). 

8.3.2.2 Using the soil sampler (Sec. 6.3.2.1), add 2-3 cm 

(approximately 2 g) of the soil sample to a headspace vial and seal immediately 

with the PTFE side of the septum facing toward the sample. The samples should be 

obtained and transferred to a vial rapidly after sampling (<10 seconds) to minimize 

volatilization losses, and they should be introduced into the vials gently to reduce 

agitation which might drive off volatile compounds. If methanol is added to the vial 
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prior to the sample, the vial, cap and methanol should be tared and the masses 

recorded prior to and after adding a soil sample to the vial. The recorded mass 

should be checked by the analyzing laboratory to verify that solvent was not lost 

during shipping and/or storage. 

8.3.3 Sampling with a sealable, air-tight coring device for low or high level 

analysis: 

For cohesive soils, soil samples can be taken in appropriately sized air-tight 

sealable coring devices for refrigeration and shipping to the laboratory, where the samples 

are further preserved or immediately prepared for analysis. 

8.3.3.1 Insert a clean coring device into a fresh surface for sample 

collection and ensure that no air is trapped between the coring tool and the 

sample. The volume of material collected should not cause excessive stress on 

the coring tool during intrusion into the material. Just before capping, a visual 

inspection of the lip and threads of the sample vessel should be made and any 

foreign debris should be wiped clean, allowing an airtight seal to form. 

 8.3.3.2 Upon laboratory receipt, the soil plug in each sealable coring 

device is extruded into individual tared headspace VOA vials containing the 

appropriate solution (either matrix modifier or reagent water for low level analysis, 

with pH modifying preservative as appropriate, or methanol for high level 

analysis). The coring device must fit into the mouth of the headspace vial or other 

VOA vial into which the sample is extruded, or losses of VOCs will result. In order 

to estimate the sample mass added, the vial, cap and any added solutions should 

be tared and the mass recorded prior to and after adding a soil sample to the vial. 

8.4 Field blanks should be prepared, regardless of which alternative is employed for soil 

sample collection. If the matrix modifying solution is not added in the field, then the field blank(s)

should be prepared by adding any reagents used in the field (e.g., 10.0 mL of organic-free 

reagent water, methanol, or matrix modifying solution, plus any other chemical preservatives) to 

a clean vial and immediately sealing the vial. 

8.5 Sample storage 

8.5.1 Samples should be stored at ≤6 °C until analysis in order to limit diffusion 

of the analytes out of the water, reduce the ability of the analytes to react with the glass 

walls of the sampling container and further hinder sample biodegradation. Water samples 

in VOA vials with no headspace should not be frozen, but subsamples added to prepared 

headspace vials may be frozen, provided the integrity of the container seal is maintained. 

Freezing of soil samples is also appropriate provided the storage temperature is not lower 

than the minimum temperature recommended by the manufacturer for maintaining integrity 

of the container seal. Freezing in this temperature range may be used to extend the holding 

time of soils in sealed air-tight coring devices and in sealed headspace vials with reagent 

water, even if no other chemical preservative is added. See Table A1 in the Appendix of 

method 5035A for more details. The sample storage area should be free of organic 

solvent vapors. 

8.5.2 All samples should be analyzed within 14 days of collection or sooner if 

labile compounds are target analytes. See the cautionary notes in Table 4-1 of Chapter 

Four, Method 5035, Appendix A, Table A-1, and the list of analytes in Sec. 1.1 of this 

method pertaining to certain compound classes and applicable preservation options that 
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may affect target analyte stability and analytical holding times. Samples not analyzed within 

this period should be identified to the data user and the results considered minimum values 

unless it can be demonstrated that the reported VOC concentrations are not adversely 

affected by preservation, storage and analyses performed outside the recommended 

holding times. 

9.0 QUALITY CONTROL 

9.1 Refer to Chapter One for guidance on quality assurance (QA) and quality control 

(QC) protocols. It should be noted that several methods (e.g., Method 8000) also contain general 

QC criteria and guidance that pertain to the individual methods referenced therein (e.g., Methods 

8081, 8082, 8260 and 8270). Individual methods may also contain QC criteria specific only to 

that method. The QC criteria in the general methods take precedence over chapter QC criteria. 

Method-specific QC criteria take precedence over general method QC criteria. 

Any effort involving the collection of analytical data should include development of a 

structured and systematic planning document, such as a Quality Assurance Project Plan (QAPP) 

or a Sampling and Analysis Plan (SAP), which translates project objectives and specifications 

into directions for those that will implement the project and assess the results. Each laboratory 

should maintain a formal quality assurance program. The laboratory should also maintain 

records to document the quality of the data generated. All data sheets and quality control data 

should be maintained for reference or inspection. 

9.2 Initial Demonstration of Proficiency (IDP) 

Each laboratory must demonstrate initial proficiency with each sample preparation and 

determinative method combination it utilizes by generating data of acceptable accuracy and 

precision for target analytes in a clean matrix. The laboratory must also repeat the demonstration 

of proficiency whenever new staff members are trained or significant changes in instrumentation 

are made. See Method 8000D, Sec. 9.3 for information on how to accomplish a demonstration of 

proficiency. 

9.3 Lower Limit of Quantitation (LLOQ) check standard 

The laboratory shall establish the LLOQ as the lowest point of quantitation, which in most 

cases, is the lowest concentration in the calibration curve. LLOQ verification is recommended for 

each project application to validate quantitation capability at low analyte concentration levels. 

This verification may be accomplished with either clean control material (e.g., reagent water, 

solvent blank, Ottawa sand, diatomaceous earth, etc.) or a representative sample matrix, free of 

target compounds. Optimally, the LLOQ should be less than the desired regulatory action levels 

based on the stated DQOs. 

In order to demonstrate the entire sample preparation and analysis process at the lower 

limit of quantitation (LLOQ), a LLOQ check standard (not part of an initial calibration) is prepared 

by spiking a clean control material with the analyte(s) of interest at the predicted LLOQ 

concentration level(s). Alternatively, a representative sample matrix may be spiked with the 

analytes of interest at the predicted LLOQ concentration levels. The LLOQ check is carried 

through the same preparation procedures as environmental samples and other QC samples. 

Recovery of target analytes in the LLOQ check standard should be within established 

in-house limits, or other such project-specific acceptance limits, to demonstrate acceptable 

method performance at the LLOQ. Until the laboratory has sufficient data to determine 
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acceptance limits, the LCS criteria ± 20% may be used for the LLOQ acceptance criteria. This 

acknowledges the poorer overall response at the low end of the calibration curve. 

Historically-based LLOQ acceptance criteria should be determined as soon as practical once 

sufficient data points have been acquired. Additional information on LLOQ can be found in 

8000D, Sec. 9.7. 

9.4 Initially, before processing any samples, the analyst should demonstrate that all 

parts of the equipment in contact with the sample and reagents are interference-free. This is 

accomplished through the analysis of a method blank. As a continuing check, each time samples 

are extracted, cleaned up, and analyzed, and when there is a change in reagents, a method 

blank should be prepared and analyzed for the compounds of interest as a safeguard against 

chronic laboratory contamination. If a peak is observed within the retention time window of any 

analyte that would interfere with measurement of that analyte, determine the source and 

eliminate it, if possible, before analyzing the samples. The blanks should be carried through all 

stages of sample preparation and analysis. When new reagents or chemicals are received, the 

laboratory should monitor method and/or instrument blanks associated with samples for any 

signs of contamination. It is not necessary to test every new batch of reagents or chemicals prior 

to sample preparation if the source shows no prior problems. However, if reagents are changed 

during a preparation batch, separate blanks must be prepared for each set of reagents. 

The laboratory should not subtract the results of the method blank from those of any 

associated samples. Such "blank subtraction" may lead to negative sample results. If the method 

blank results do not meet the project-specific acceptance criteria and reanalysis is not practical, 

then the data user should be provided with the sample results, the method blank results, and a 

discussion of the corrective actions undertaken by the laboratory. 

9.5 Sample quality control for preparation and analysis 

The laboratory must also have procedures for documenting the effect of the matrix on 

method performance (precision, bias, method sensitivity). At a minimum, each batch of 20 or 

fewer field samples should include at least one method blank, a laboratory control sample (LCS), 

and either a matrix spike/matrix spike duplicate (MS/MSD) pair or a matrix spike and duplicate 

analysis of one field sample. When used, surrogates may be added to each field sample and QC 

sample and their recovery monitored to evaluate the effect of the sample matrix. Any method 

blanks, matrix spike samples, and duplicate QC samples should be subjected to the same 

analytical procedures (Sec. 11.0) as those used on actual samples. 

See Methods 5000 and 8000 for procedures to follow to demonstrate acceptable continuing 

performance on each set of samples to be analyzed. 

9.6 It is recommended that the laboratory adopt additional quality assurance practices 

for use with this method. The specific practices that are most productive depend upon the needs 

of the laboratory and the nature of the samples. Whenever possible, the laboratory should 

analyze standard reference materials and participate in relevant performance evaluation studies. 

9.7 The laboratory should have quality control procedures to make sure that sample 

integrity is not compromised during the sample collection and sample handling process, e.g., 

through analysis of trip blanks, method blanks, etc. In addition, it would be advisable for the 

laboratory to monitor the internal standard (IS) area counts for all samples; leaks attributed to a 

poor seal with the vial caps and septa will be evident by low IS area counts. Sample containers 

and data results for instances where low IS area counts are observed and leaks are suspected 

should be discarded. Low area counts of the less volatile internal standards may also be 

attributed to matrix effects and should not be confused with a leaking vial. 
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9.8 Heating the sample/chemical preservative/matrix modifier mixture can exacerbate 

chemical interferences such as those introduced by acid catalyzed hydrolysis or base catalyzed 

substitution and elimination reactions. This can only be monitored through a matrix spike of a 

sample from every project analytical batch. The spiking solution should be the same as that used 

to prepare the calibration standards in order to minimize sources of variability in evaluating spike 

recovery. The acceptance criteria shall be those recommended in the determinative method or 

specified by a properly executed systematic planning document. If these criteria cannot be met, 

the analyst may adjust the pH of the mixture through the addition of solid NaHSO4 to excessively 

basic mixtures or solid Na3PO4•12H2O to excessively acidic mixtures. After this is done, the 

matrix spike analysis should be repeated with an unanalyzed vial. If the results are acceptable, 

this pH adjustment should be made to all samples in the appropriate analytical batch. Even if the 

pH-adjusted matrix spike analysis is acceptable, the data user must be made aware that the 

initial matrix spike failed and the pH adjustment was necessary. The results from the pH adjusted 

samples should be reported, and the data user must be made aware that the results for the 

analytes for which the initial matrix spike failed are questionable. 

10.0 CALIBRATION AND STANDARDIZATION 

See Sec. 11.0 for information on calibration and standardization and refer to the 

appropriate determinative method for additional calibration and standardization procedures. 

11.0 PROCEDURE 

11.1 Sample preparation - Sample preparation in the laboratory will be necessary except 

when a soil sample is collected and used only for screening purposes. The procedure for sample 

preparation depends upon the matrix of the sample and the target analyte concentration range. 

To minimize loss of VOCs from the samples or exchange of the vial headspace with the room air, 

add spiking solutions quickly to cold sample vials soon after removing from refrigerated storage 

and either reseal or place a new cap on top of the vial and apply slight pressure in between 

preparation steps. 

CAUTION: Adding standard solutions (e.g., internal standards) to a sealed vial by puncturing 

the PTFE septum face with a microsyringe exposes the gas phase contents of the 

vial to the silicone material backing the septum. This material may absorb some of 

the gas phase VOCs in the vial, causing problems with calibration, measurement in 

samples, spike recovery, etc., as a function of exposure time. This problem is 

generally worse for the higher molecular weight VOCs with high octanol-water 

partition coefficients, and this practice should be avoided or the vial caps should be 

exchanged for caps with un-punctured septa soon after spiking if these VOCs are 

analytes of interest. 

11.1.1 Water samples - The preparation of water samples inevitably involves 

some sample manipulation and exposure to the laboratory atmosphere. Extreme caution 

should be exercised to minimize any volatilization of analytes out of the sample contents 

and into the laboratory atmosphere. The first precaution is to prepare the water samples 

immediately after removal from cold storage. The decreased temperature reduces analyte 

volatility, and the benefits of this are substantially greater than the inaccuracies introduced 

by measuring sample volume at lower temperatures. 
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11.1.1.1 Add 5 mL of the matrix modifier solution to a headspace vial 

(Sec. 6.0), if used. Otherwise, add 5 mL reagent water. Set the septum and crimp 

top onto the vial and move the crimping tool to a readily available position. 

11.1.1.2 Insert the tip of a 5-mL gas tight syringe through the septum of 

the vial to withdraw the sample. Fill the syringe, taking care to prevent air from 

leaking into the syringe while filling it, then remove the syringe from the sample and 

place it in the liquid phase in the headspace vial. Inject the entire aliquot into the 

headspace vial, then quickly add the internal standard and/or surrogate standard 

solution, if used, and immediately seal the vial. This process of taking an aliquot 

destroys the validity of the liquid sample for future analysis. Therefore, if there is 

only one VOA vial, the analyst should prepare a second sample in the same 

manner as the first at this time to protect against possible loss of sample integrity. 

This second sample is stored at <6°C until the analyst has determined that the first 

sample has been analyzed properly. If a second analysis is needed, it should be 

completed within 24 hr. 

 

11.1.2 Soil samples - If the sample will be analyzed by direct vapor partitioning for 

low level analysis, follow the instructions in this section. If the sample will be extracted with 

solvent and the extract diluted for high level analysis, proceed to Sec.11.4. 

11.1.2.1 If the soil sample was placed into a headspace vial with neither 

water nor matrix modifier and the sample mass was not recorded in the field, 

estimate the sample mass by weighing the vial plus soil and subtract the mass of an 

empty vial and cap. Then, unseal the vial, add 10.0 mL of matrix modifying solution, 

if used, or reagent water, along with any internal standard and/or surrogate 

standard used, and immediately reseal the vial. As noted in Sec. 8.0, VOC losses 

may occur as a result of opening the vial and displacing 10 mL of headspace. 

CAUTION: Only open and prepare one vial at a time to minimize loss of volatile 

organics. 

11.1.2.2 If the soil sample was placed into a headspace vial with 

reagent water or the matrix modifier solution at the time of sampling, first weigh the 

sealed vial and its contents to 0.01 g. If the matrix modifying solution was added at 

the time of sampling (Sec. 8.3.1), the tare weight does not include 10 mL of matrix 

modifying solution. Therefore, weigh the field blank associated with those samples 

and subtract from it the tare weight of the vial in which the field blank was prepared. 

Use the difference as the weight of the matrix modifying solution in the samples. 

(Although this approach may introduce some error into the sample results, that error 

should be much less than the changes that will occur in an unpreserved sample 

shipped to the laboratory without the modifier). If surrogates and/or internal 

standards were not added at the time of sampling, they should be added at this 

time. 

11.2 The low-concentration method utilizing an equilibrium headspace technique is 

found in Sec. 11.3 and sample preparation for the high-concentration method is found in Sec. 

11.4. The high-concentration method is recommended for samples that obviously contain oily 

material or organic sludge waste (see Sec. 4.4). See Method 8000 for guidance on the selection 

of a GC or GC/MS determinative method. For the analysis of gasoline, use Method 8021 with 

GC/PID (photoionization detector) for BTEX (benzene, toluene, ethylbenzene, and xylenes) in 

series with Method 8015 with the GC/FID (flame ionization detector) detector for other gasoline 

components. If GC/MS analysis is preferred, follow Method 8260. For the analysis of MTBE and 
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the other fuel oxygenates, use either Method 8015 with the GC/FID detector or Method 8260 

using GC/MS. 

11.3 Low-concentration (direct vapor partitioning) method for water, soil/sediment and 

solid waste amenable to the equilibrium headspace method. 

 11.3.1 Calibration 

Prior to using this introduction technique for any GC or GC/MS method, the system 

must be calibrated. General calibration procedures are discussed in Method 8000, while 

the determinative methods and Method 5000 provide specific information on calibration 

and preparation of standards. Normally, external standard calibration is preferred for the 

GC methods because of possible interference problems with internal standards. If 

interferences are not a problem, based on historical data, internal standard calibration is 

acceptable. The GC/MS methods normally utilize internal standard calibration. The GC/MS 

methods require instrument tuning prior to proceeding with calibration. 

11.3.1.1 GC/MS tuning 

If a GC/MS determinative method is employed, prepare a headspace vial 

containing reagent water and the amount of 4-bromofluorobenzene (BFB) listed in 

the determinative method. 

11.3.1.2 Initial calibration 

Prepare a minimum of five headspace vials for calibration standards, as 

described in Sec. 7.6, and a reagent blank (Sec. 7.5), and proceed according to Sec. 

11.3.2 and the determinative method selected. The mixing step is unnecessary, 

because no soil is present in the vial. See method 8000D for the minimum number 

of calibration standards recommended for each type of calibration model. 

11.3.1.3 Calibration verification 

Prepare a headspace vial, as described in Sec. 7.6, by spiking with the 

mid-concentration calibration standard. Proceed according to Sec. 11.3.2.1 

(beginning by placing the vial into the autosampler) and the determinative method. 

If a GC/MS determinative method is employed, prepare a second headspace vial 

containing reagent water and the amount of BFB listed in the determinative method. 

11.3.2 Headspace analyzer operating conditions 

The conditions described throughout Sec. 11.3 were experimentally optimized 

using the equipment described in Reference #1 in Sec. 16 and employing Method 8260 as 

the determinative method. If other headspace systems and determinative methods are 

utilized, it is recommended that the manufacturer's headspace operating conditions be 

followed, provided that they are appropriate for the determinative method to be employed. 

11.3.2.1 Mix the samples (on a rotator or shaker) for at least 2 min. 

For samples that contain water insoluble materials, care must be exercised during 

mixing to prevent this material from adhering to the inner surface of the vial seal; 

otherwise the sampling needle can become contaminated with this material upon 

puncturing the seal. Care must also be exercised to avoid over filling the vial to 

prevent contaminating the needle with aqueous sample. 
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Place the vials in the autosampler carrousel at room temperature. The 

individual vials are heated to 85 °C and allowed to equilibrate for 50 min. Each 

sample is mixed by mechanical agitation during this equilibrium period. Each vial is 

pressurized with helium carrier gas to a minimum pressure of 10 psi. 

11.3.2.2 A representative and reproducible sample of the pressurized 

headspace is transferred to the GC column through a heated transfer line according 

to the manufacturer's instructions. 

11.3.2.3 Proceed with the analysis as per the determinative method of 

choice. 

NOTE: If maintaining a specified pH is critical to quality assured measurement of 

the analyte(s) of concern (Sec. 4.7), the pH of each sample should be 

verified. If basic preservation is necessary, the pH of the sample should be 

verified to be ≥10 (see Sec. 7.8.1). If acid preservation is necessary, the 

pH should be verified to be ≤ 2, (see Sec. 7.8.2). This check may be 

performed after analysis of the sample in order to avoid compromising 

sample integrity. Wide-range pH paper should provide sufficient 

information to verify efficacy of the preservative.

11.4 High-concentration soil method 

11.4.1 If the sample was collected as described in Sec. 8.3.2 without the addition 

of methanol to the vial, then weigh the sample to the nearest 0.01 g. Add twice the volume 

of methanol as the nominal sample mass to a tared VOA vial and immediately reseal the 

vial. Open only one vial at a time to minimize loss of VOCs. If the sample was collected in a 

sealable coring device as described in Sec. 8.3.3, add the methanol to a vial first, weigh the 

vial with the methanol and the cap together to obtain the tare mass, and then add the soil 

plug, seal immediately, reweigh, and calculate the sample mass. 

11.4.2 If the procedure in Sec. 8.3.1 was employed for sample collection and 

either the matrix modifying solution or organic-free reagent water was added to the sample 

vials, subsamples for high concentration analysis should be taken from the separate VOA 

vials collected without matrix modifying solution or reagent water as described in Sec. 8.3.2 

or from the vials collected for dry solids determination. Transfer approximately 5 g of 

sample from the 40 or 60 mL VOA vial into a tared VOA vial containing 10.0 mL of 

methanol, seal the vial, and reweigh to estimate the mass of sample transferred. Open only 

one vial at a time to minimize the loss of volatile organics. Substantial VOC losses may 

occur as a result of transferring a subsample from one vial to another using this procedure. 

See Sec. A.5 in the Appendix of Method 5035A for more details. 

11.4.3 Mix by shaking for 10 min at room temperature. Decant 2 mL of the 

methanol extract to a screw-top vial with PTFE-faced septa and seal. Withdraw 10 μLand 

inject into a headspace vial containing 10.0 mL of matrix modifying solution or organic free 

reagent water. A larger volume of methanol may be added provided the methanol content 

does not adversely affect the analyte responses (refer to Sec. 7.4.1). Add internal 

standards and/or surrogates as appropriate, and analyze by the headspace procedure by 

placing the vial into the autosampler and proceeding with Sec. 11.3.2.1. 
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12.0 DATA ANALYSIS AND CALCULATIONS 

 There are no data analysis and calculation steps directly associated with this procedure. 

Follow the directions given in the determinative method. 

13.0 METHOD PERFORMANCE 

13.1 Performance data and related information are provided in SW-846 methods only as 

examples and guidance. The data do not represent required performance goals for users of the 

methods. Instead, performance goals should be developed on a project-specific basis, and the 

laboratory should establish in-house QC performance criteria for the application of this method. 

13.2 Water samples 

This method was used to measure several VOCs in groundwater samples. The samples 

were collected from two sites: twenty-four samples were collected from the first site (site A) and 

twenty-three samples were collected from the second site (site B). Using a basic preservative to 

prevent the hydrolysis of ethers such as MTBE, multiple groundwater vials were collected at 

each sampling point. The samples were analyzed by three independent laboratories. All of the 

laboratories used this method for sample preparation, and each laboratory used a different 

determinative method. One laboratory used a GC/MS technique with a quadrupole mass 

spectrometer (Method 8260), another used a GC/MS technique with an ion-trap mass 

spectrometer (Method 8260), and the third used a GC/FID technique (Method 8015). The 

example results of the analyses are shown in Figures 1 through 6. Since all three laboratories 

followed the same project plan and the same data quality objectives, the data generated by the 

three laboratories is mutually comparable, even though they used different techniques. As 

recommended in Sec. 9.8, matrix spike studies were done at each site. The example percent 

recoveries from the site A studies are shown in Figure 7, while those from site B are shown in 

Figure 8. Figure 8 shows that one of the labs had poor recovery for MTBE. However, the 

recovery of the other ethers was acceptable, indicating that hydrolysis was unlikely to be the 

source of the problem. The effect was attributed to sample matrix interference. 

13.3 Soil samples - Single-laboratory accuracy and precision data were obtained for the 

method analytes in two soil matrices, i.e., sand and garden soil. These data are found in Tables 

26-28 of Method 8260C. 

14.0 POLLUTION PREVENTION 

14.1 Pollution prevention encompasses any technique that reduces or eliminates the 

quantity and/or toxicity of waste at the point of generation. Numerous opportunities for pollution 

prevention exist in laboratory operation. The EPA has established a preferred hierarchy of 

environmental management techniques that places pollution prevention as the management 

option of first choice. Whenever feasible, laboratory personnel should use pollution prevention 

techniques to address their waste generation. When wastes cannot be feasibly reduced at the 

source, the Agency recommends recycling as the next best option. 

14.2 For information about pollution prevention that may be applicable to laboratories 

and research institutions consult Less is Better: Laboratory Chemical Management for Waste 

Reduction, a free publication available from the American Chemical Society (ACS), Committee 

on Chemical Safety, 

http://portal.acs.org/portal/fileFetch/C/WPCP_012290/pdf/WPCP_012290.pdf. 
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15.0 WASTE MANAGEMENT 

The Environmental Protection Agency requires that laboratory waste management 

practices be conducted consistent with all applicable rules and regulations. The Agency urges 

laboratories to protect the air, water, and land by minimizing and controlling all releases from 

hoods and bench operations, complying with the letter and spirit of any sewer discharge permits 

and regulations, and by complying with all solid and hazardous waste regulations, particularly the 

hazardous waste identification rules and land disposal restrictions. For further information on 

waste management, consult the ACS publication listed in Sec. 14.2. 

16.0 REFERENCES 

1. P. Flores, and T. Bellar, "Determination of Volatile Organic Compounds in Soils using 

Equilibrium Headspace Analysis and Capillary Column Gas Chromatography/Mass 

Spectrometry," U.S. Environmental Protection Agency, Office of Research and 

Development, Environmental Monitoring Systems Laboratory, Cincinnati, OH, December, 

1992.

2. B. V. Loffe, and A. G. Vitenberg, "Headspace Analysis and Related Methods in Gas 

Chromatography," John Wiley and Sons, 1984. 

3. R. J. Pirkle, and R. P. McLoughlin,“The Analysis of Selected Components of 

Reformulated Gasoline in Environmental Samples”from MTBE Handbook, ed. Kostecki, P. 

and Moyer, E. Amherst Scientific Publishers, 2002. 

4. USEPA OUST, Environmental Fact Sheet: Analytical Methods for Fuel Oxygenates, EPA 

510-F-03-001, April, 2003. 

5. H. White, B. Lesnik, and J. T. Wilson,“Analytical Methods for Fuel Oxygenates”, 

LUSTLine (Bulletin #42), October, 2002, 

http://www.epa.gov/oust/mtbe/LL42Analytical.pdf.

6. RCRA Organic Methods Workgroup Meeting Minutes, March 20, 2012. 

7. RCRA Organic Methods Workgroup Meeting Minutes, March 22, 2012. 

8. RCRA Organic Methods Workgroup Meeting presentation describing changes to 

method 5021, “Proposed Changes to SW-846 method 5021A, VOCs by Static 

Headspace”, March 1, 2012. 
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17.0 TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA 

The following pages contain the tables and figures referenced by this method. 

FIGURE 1 

 EXAMPLE RESULTS FOR SITE A STUDY OF ETHYL TERT-BUTYL ETHER 

Sample 
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FIGURE 2 

EXAMPLE RESULTS FROM SITE A STUDY FOR TERT AMYL METHYL ETHER 

Sample 
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FIGURE 3 

EXAMPLE RESULTS FROM SITE A STUDY FOR METHYL TERT-BUTYL ETHER 

Sample 
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FIGURE 4 

EXAMPLE RESULTS FROM SITE B STUDY FOR BENZENE 

Sample
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FIGURE 5 

EXAMPLE RESULTS FROM SITE B STUDY FOR METHYL TERT-BUTYL ETHER 

Sample
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FIGURE 6 

EXAMPLE RESULTS FROM SITE B STUDY FOR TERT-BUTYL ALCOHOL 

Sample
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FIGURE 7 

EXAMPLE PERCENT RECOVERIES FROM THE MATRIX SPIKE STUDIES OF SITE A 
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FIGURE 8 

EXAMPLE PERCENT RECOVERIES FROM THE MATRIX SPIKE STUDIES OF SITE B 
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Appendix A: 

Summary of Revisions to Method 5021A (as compared to previous Revision 1, June 2003)

1. Improved overall method formatting for consistency with new SW-846 methods style guidance. 

The format was updated to Microsoft Word .docx. 

2. Minor editorial and technical revisions were made throughout to improve method clarity. 

3. The revision number was changed to 2 and the date published was changed to July 2014. 

4. This appendix was added showing changes from the previous revision. 

5. Added updated IDP language and LLOQ verification standard language to Sections 9.2 and 

9.3. 

6. Included response column and a classification system for analytes in Secs. 1.1 and 1.2 to 

provide an indication of which VOC responses were improved by the matrix modifier. 

7. Added a sealable, air-tight coring device as an alternative sample collection option for soils to 

Sec. 8.3.3. 

8. Added an alternative for calibration standard preparation to Sec. 7.4.1 that allowed for multiple 

calibration levels prepared by adding different volumes of one or more stock solutions. 

9. Clarified in Sec. 1.4 the major sources of measurement bias expected for sample analysis 

using this method, as well as which sources of measurement bias the matrix modifier may 

improve, which sources of measurement bias may be made worse by the matrix modifier, and 

under what other circumstances not adding the matrix modifier may be appropriate. 

10. Added a caution after Sec. 11.1 regarding the expected effect of compromising the PTFE face 

of a vial seal on recovery of oil soluble target analytes.