**SW-846 Update V 5021A - 1 Revision 2 July 2014**  **METHOD 5021A**

**VOLATILE ORGANIC COMPOUNDS IN VARIOUS SAMPLE MATRI CES** 

**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 chemica l 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 guida nce methods which contain general**  **information on how to perform an analytical procedu re or technique which a laboratory can use**  **as a basic starting point for generating its own de tailed standard operating procedure (SOP),**  **either for its own general use or for a specific pr oject 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 purpo se of laboratory accreditation.** 

**1.0 SCOPE AND APPLICATION**

**Please see Appendix A at the end of this document f or 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 wa ste, 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 fo r solid samples containing high concentrations**  **of VOCs or for oily materials that may not be appro priate 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 appr opriate 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** **SW-846 Update V 5021A - 2 Revision 2 July 2014**  **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** **SW-846 Update V 5021A - 3 Revision 2 July 2014**  **c = Response in reagent water is acceptable ; similar response expected in matrix modifier solu**  **tion (< 50%**

**improvement). p = Response in matrix modifier solution ex**  **pected to improve >50% compared to reagent water; U se of** 

**matrix modifier is recommended. ws = Highly water soluble analyte. Method sen**  **sitivity expected to be poorer than for other analy tes due to poor** 

**partitioning into headspace; matrix modifier expect ed to be critical for acceptable method performance** 

**. nd = Not determined**  **hs = High stability in preserved water samples (> 6 0 days). Longer holding times may be appropriate, s**  **ee**

**Method 5035, Appendix A, Table A.1 footnote and Ref . 47 for additional information**  **ms = Medium stability in preserved water samples (1 5 - 60 days). Longer holding times may be appropria**  **te,**

**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 pos**  **sible.**

**May be degraded if acid preserved. hvs = Highly variable stability depending on the sa**  **mple matrix. Longer holding times may be appropriat e, 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 minim al calibration and quality control, such as a**  **reagent blank and a single calibration standard.**

**As with any preparative method for volatiles, scree ning samples prior to low level analysis**  **may help minimize problems associated with carryove r contamination from samples that contain**  **very high concentrations of volatiles above the cal ibration 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 coll ected to allow for screening and re-analysis.** **SW-846 Update V 5021A - 4 Revision 2 July 2014**  **1.4 In order to accommodate analysis of a variety o f 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 a dded to each sample and standard vial prior to**  **analysis. The matrix modifier solution acts to incr ease the VOCs mass transfer into the**  **headspace of the vial. The principal benefits of us ing 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 pha se (identified with ‘p’ or ‘ws’ in the**  **response column in the table in Sec. 1.1); and**

**2) less potential for measurement bias resulting fr om aqueous activity differences between**  **standards and samples.**

**Measurement bias results from VOCs partitioning int o the vial headspace differently in a**  **sample than in the calibration standards. Some pote ntial 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 dissol ved solute concentrations:** 

**At higher solute concentrations substantially large r fractions of some VOCs partition**  **into the headspace leading to high bias in the dete rmined concentration. The VOCs most**  **prone to high bias measurement at higher dissolved solute concentrations are also the**  **VOCs whose responses are most substantially improve d 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 resp onse column in the analytes table in Secs.**  **1.1 and 1.2 are not as subject to this source of me asurement 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 misci ble organic component:** 

**The presence of a water miscible organic component (e.g., cosolvent or surfactant)**  **may result in low bias measurement of VOCs with hig h octanol-water partitioning**  **coefficients (e.g., C3 and C4 alkylbenzenes, trichl orobenzenes and naphthalene), while**  **recovery of the lighter and more highly water solub le VOCs is unlikely to be strongly**  **affected unless the proportion of the water miscibl e organic component in the sample is**  **high. The matrix modifier helps improve the recover y 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 im miscible phase(s) (e.g., soils with >1%**  **organic matter, oily materials), potentially exagge rating matrix effects relative to the**  **calibration standards. This matrix effect is more p ronounced for VOCs with higher**  **octanol-water partitioning coefficients when the ma trix 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 o f matrix effects may be relevant, and**  **a compromise may have to be made for data quality o f some analytes in order to obtain reliable**  **data for the analytes deemed most critical for the project. For simple sample matrices and VOCs** **SW-846 Update V 5021A - 5 Revision 2 July 2014**  **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 frac tion in the light ends of petroleum**  **hydrocarbons,** e.g. **, gasoline. For the aromatic fraction (BTEX), use t his method and Method**  **8021 (GC/PID). A total determinative analysis of ga soline 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, Met hod 8260 (Volatile Organic Chemicals by**  **GC/MS) may be used.**

**1.6 Measurements of VOCs using this method may be s ubject to bias from several**  **sources, including differences in partitioning of V OCs between the aqueous phase and**  **headspace in samples relative to standards, differe nces in headspace volume in samples**  **relative to standards, and adsorption of VOCs to su rfaces or absorption into compatible phases**  **(** e.g. **, soil organic matter). Measurement bias is monitor ed 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 measu rement bias resulting from differences in**  **partitioning behavior of VOCs in samples relative t o standards. Measurement bias resulting from**  **adding solid material to the vial, which changes th e headspace volume in the sample relative to**  **the calibration standards, is expected to be neglig ible 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 materi al to calibration standards as the volume of the**  **bulk material being tested. Measurement bias relate d 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 ad vised 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 quali**  **ty control procedures, development of QC acceptance criteria, calculations, and general guid**  **ance. 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 method s, apparatus, materials, reagents, and supplies,**  **and on the responsibilities of the analyst for demo nstrating that the techniques employed are**  **appropriate for the analytes of interest, in the ma trix of interest, and at the levels of concern.** 

**In addition, analysts and data users are advised th at, 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 met**  **hod 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 s upervision of, appropriately**  **experienced and trained analysts for volatile organ ic 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 genera te acceptable results with this method.** 

**2.0 SUMMARY OF METHOD**

**2.1 Sample collection and headspace vial preparatio n** **SW-846 Update V 5021A - 6 Revision 2 July 2014**  **2.1.1 Water samples – A 40-mL volatile organic anal yte (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 tris odium phosphate) to the vial. At the**  **laboratory, that vial is sub-sampled into a headspa ce 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 t he analysis.** 

**2.1.2 Low concentration soil samples -- Approximate ly 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 mo difying chemical preservative (**  e.g., **sodium bisulfate, trisodium phosphate) prior to sea ling 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 se alable coring device as an alternative**  **sampling technique, which may simplify collection a nd handling of soils in the field.** 

**Surrogates and internal standards may be added to t he vials during sampling or at the**  **laboratory. If the matrix modifying solution is use d 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 modi fying 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. Ad ding the matrix modifying solution (Sec.**  **7.7) to the vial prior to adding the sample and sea ling quickly will help to limit loss of VOCs**  **from the sample container and maintain sample repre sentativeness.** 

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

**measured in the samples and to some extent on the s ample matrix. The matrix**  **modifying solution acts as a chemical preservative, but it does not otherwise alter**  **the sample pH and may not protect against degradati on of some classes of VOCs,**  **including hydrolysis of ethers or dehydrohalogenati on of chlorinated aliphatics**  **(Sec. 4.7). Sodium bisulfate has also been identifi ed as inappropriate for use as a**  **preservative for calcareous soils, which may off-ga s CO**  **2 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 co ntainer is sealed, potentially**  **leading to rupture.**

**2.1.3 High concentration soils or other solid mat erials – A representative portion**  **of soil is collected with an appropriately sized co ring tool and placed in a pre-weighed glass**  **VOA vial, and then the vial is sealed. The soil sam ple may be preserved by addition of**  **extraction solvent (** e.g., **methanol) at the time of sampling or upon receipt b y the laboratory.**  **At the laboratory, the methanol extract is then dil uted with the matrix used for the**  **calibration standards (organic-free reagent water o r the matrix modifying solution) and**  **analyzed as an aqueous sample. Sec. 8.3.3 also desc ribes the use of an air-tight sealable**  **coring device as an alternative sample collection t echnique that may be useful, and Sec.**  **A.6 of SW-846 method 5035A provides additional info rmation pertaining to methanol** 

**extraction of soils.**



### NOTE **: Surrogate compounds may either be spiked into th e solvent at the time of**  **extraction or into reagent water containing an aliq uot of the extract prior to**  **analysis. Since the surrogate recovery data from th ese two options provides**  **assurances of either extraction or analytical effic iencies, the decision as to** **SW-846 Update V 5021A - 7 Revision 2 July 2014**  

### when the surrogates are added depends on what quest **ions 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 col lected in VOA vials for dry weight** 

**determination.**

**2.3 In the laboratory, the vials are rotated to all ow for diffusion of internal standards**  **and surrogates throughout the matrix. The vials are pla**  **ced in the autosampler carousel of the headspace analyzer and maintained at room temperatu**  **re. 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 equ ilibrate 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 th rough 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 a ppropriate 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 instr uctions 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 glassw are. Also refer to the determinative methods**  **to be used for information regarding potential inte rferences.** 

**4.2 Volatile organic analyses are subject to major interference problems because of the**  **prevalence of volatile organics in a laboratory. Se e Method 5000 for common problems and**  **precautions to be followed.**

**4.3 Samples can be contaminated by diffusion of vol atile organics (particularly**  **methylene chloride and fluorocarbons) through the s eptum seal of the sample vial during**  **shipment and storage. A trip blank, prepared from a n 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 inter ferences by one of several**  **processes or a combination of these processes. Thes e include, but are not necessarily limited to,**  **the absorption potential of the soil, the biologica l activity of the soil, and the actual composition**  **of the soil. Soils high in organic matter or oily mate**  **rial and organic sludge wastes inhibit the SW-846 Update V 5021A - 8 Revision 2**  **July 2014 partitioning of the volatile target analytes into t**  **he headspace. Therefore, analyte recovery by direct vapor partitioning may be low and will depen**  **d on the properties of the particular chemical. This matrix effect can be difficult, if not impossi**  **ble, 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-concentr**  **ation procedure in this method should minimize the problem with oily waste and other organic sludg**  **e wastes.**

**4.5 Contamination by carryover can occur whenever h igh concentration and low**  **concentration samples are analyzed sequentially. Wh ere 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 affecte d 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 perf ormed should be free of any solvents**  **that may interfere with the analysis. Special preca utions must be taken when analyzing for**  **methylene chloride. The analytical and sample stora ge areas should be isolated from all**  **atmospheric sources of methylene chloride. Otherwis e, random background levels can result.**  **Since methylene chloride can permeate through polyt etrafluoroethylene (PTFE) tubing, all GC**  **carrier gas lines and purge gas plumbing should be constructed of stainless steel or copper**  **tubing. Laboratory workers' clothing previously exp osed to methylene chloride fumes during**  **common liquid/liquid extraction procedures can cont ribute to sample contamination. The**  **presence of other organic solvents in the laborator y 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 highe r**  **temperatures used in this method. As such, basic pr eservatives should be used if the target**  **analytes are ethers or the alcohols that those ethe rs would form if hydrolyzed. Strong bases may**  **catalyze substitution and elimination reactions tha t can occur if halogenated compounds are**  **present. Halogenated aliphatic VOCs are particularl y susceptible to dehydrohalogenation** 

**reactions in neutral to basic conditions at elevate d temperature such as with a heated sample**  **preparation procedure as is described here. Accordi ngly, acidic preservatives may be necessary**  **to prevent dehydrohalogenation if halogenated aliph atic VOCs are analytes of interest or their**  **presence is suspected and their transformation prod ucts are of interest. Acetone has also been**  **observed to form in high organic content soils pres erved 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 anal ytes which the client intends to monitor.** 

**5.0 SAFETY**

**This method does not address all safety issues asso ciated 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 chem icals included in this method. A reference file**  **of material safety data sheets (MSDSs) should be av ailable to all personnel involved in these**  **analyses. SW-846 Update V 5021A - 9 Revision 2**  **July 2014 6.0 EQUIPMENT AND SUPPLIES** 

**The mention of trade names or commercial products i n this manual is for illustrative**  **purposes only, and does not constitute an EPA endor sement 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 subs equently evaluated by the Agency.**  **Glassware, reagents, supplies, equipment, and setti ngs other than those listed in this manual**  **may be employed provided that method performance ap propriate for the intended application** 

**has been demonstrated and documented.**

**This section does not list all common laboratory gl assware (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. Via ls of other sizes may be employed, provided**  **that they can be hermetically sealed and equipped w ith 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 pretreatm ent provided they are demonstrated to be**  **clean through method blank analysis. Store the vial s in an area free of organic solvents. If vials**  **are suspected of being a source of contamination, f irst wash the vials in a detergent solution,**  **then thoroughly rinse with tap water followed by di stilled 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 lis ted in Sec. 11.0 are those selected**  **for the equipment used in developing this method. S ee Reference #1 in Sec. 16 for more detail.**  **Other equipment and conditions may be employed, pro vided 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 t ransferring a representative**  **portion of the headspace into a gas chromatograph f itted with a capillary column without**  **adversely affecting the chromatography or the detec tor.** 

**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 (Associ ated Design and**  **Manufacturing Company, 814 North Henry Street, Alex andria, VA 22314), or**  **equivalent.**

**6.3.2.2 An automatic syringe or bottle top dispense r calibrated to**  **deliver a 10.0 mL liquid volume. SW-846 Update V 5021A - 10 Revision 2**  **July 2014 6.3.2.3 Crimping tool for headspace vials - If usin**  **g 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 wil l be used for sample screening,**  **high concentration analysis (if needed) and dry wei ght determination.** 

**6.3.2.5 Sealable, air-tight coring device – A soil coring device with an**  **internal volume appropriate for approximately 2 g o f 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 ta rget 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 preparat ion and for addition of**  **internal standard and surrogate spiking solutions.**

**6.4.3 5-mL glass hypodermic syringes with Luer-Lok** 

### TM **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 tes ts. Unless otherwise indicated, it is**  **intended that all reagents conform to the specifica tions of the Committee on Analytical Reagents**  **of the American Chemical Society, where such specif ications are available. Other grades may be**  **used, provided it is first ascertained that the rea gent is of sufficiently high purity to permit its u**  **se without lessening the accuracy of the determination**  **. Reagents should be stored in glass to prevent the leaching of contaminants from plastic c**  **ontainers.**

**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. Sto re 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 fo r guidance on the preparation of**  **stock standards and a secondary standard for intern al 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 analy tes. The concentrations of the calibration** 

**solutions should be such that the addition of 1.0** μ **L of each to the headspace vials will bracket the analytical range of the detector. Alter**  **natively, calibration standards may be prepared by adding different volumes of one or more**  **stock solutions provided that the SW-846 Update V 5021A - 11 Revision 2**  **July 2014 linearity of the calibration is not affected by the**  **methanol content. For analysis of methanol extracts, it may be appropriate to calibrate surrog**  **ates at multiple concentration levels as well to demonstrate calibration linearity at the su**  **rrogate 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 meani ngful 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 th e determinative method. If determination is**  **by GC, external standard calibration may be preferr ed 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 necessar y amounts of internal standards and surrogate**  **compounds under the surface of the water in the hea dspace vial, and seal the vial. Place in the**  **autosampler and analyze in the same manner as an un known sample. Any chemical**  **preservative and/or matrix modifier added to the fi eld 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 sp iking solution(s) prepared in Sec. 7.4.1 in**  **the same manner that internal standards and surroga tes are added. Any chemical preservative**  **and/or matrix modifier added to the field samples s hould 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 modifi er solution should not affect the pH of the**  **sample to the extent that preservation or analyte s tability is compromised** 

**. Analyze a 10.0-mL**  **portion from each batch according to Sec. 7.5 to ve rify that the solution is free of contaminants.**  **Store the prepared matrix-modifying solution in a s ealed bottle in an area free of organic** 

**chemicals at** ≤ **6** ° **C.**

**CAUTION : The matrix modifying solution may not be appropri**  **ate for analysis of some VOCs in**

**soil samples having high organic matter content.**

**7.8 Preparation of chemical preservative for low le vel (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; Na 3**  **PO 4**  **•12H 2**  **O) should be added to either a 22-mL headspace vial or a 40-mL water sample vial to rais**  **e the pH above 10.**

**7.8.2 If an acidic preservative is chosen, 2-3 drop s of 6N hydrochloric acid (HCl)**  **should be added to a 40-mL water sample vial. The H Cl 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 (NaHSO 4**  **) should be added to each 22-mL vial.**

**CAUTION : If samples containing MTBE, TAME, ETBE or other f**  **uel ethers have been**

**acid preserved with either sodium bisulfate or hydr ochloric acid, these**  **samples must be adjusted to pH >10 with trisodium p hosphate** **SW-846 Update V 5021A - 12 Revision 2 July 2014**  **dodecahydrate (TSP) (Sec. 7.8.1) prior to initiatio n of the headspace**  **analysis.**

**8.0 SAMPLE COLLECTION, PRESERVATION, AND STORAGE**

**Sample collection, preservation and storage require ments may vary by EPA program and**  **may be specified in a regulation or project plannin g document that requires compliance**  **monitoring for a given contaminant. Where such requ irements are specified in the regulation,**  **follow those requirements. In the absence of specif ic regulatory requirements, use the following**  **information as guidance in determining an appropria te plan for sample collection, preservation**  **and storage prior to sample collection and analysis**

**.**

**8.1 Refer to Chapter Four and Method 5035A or gener al 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 con**  **sidered corrupted and should be discarded.**

**Pre-testing of a representative soil or aqueous sam ple, prior to collection, with acid or**  **bisulfate may show effervescence if carbonaceous ma terials are present. If bubbling occurs**  **during chemical preservation, an increased potentia l for loss of volatile constituents exists and**  **samples should therefore be collected without prese rving with acid or bisulfate.** 

**8.2 Water samples - Fill the 40-mL vial and, accord ing to the analyte list to be analyzed,**  **chemically preserve the sample (Sec. 7.8) as necess ary. 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. Tran sfer of the sample into a headspace vial and** 

**the addition of the matrix modifier and standards s hould be performed at the laboratory.** 

**In general, liquid samples should be poured into th e 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 fi tted and sealed, and the vial inverted, no**  **headspace is visible. The sample should be hermetic ally sealed in the vial at the time of**  **sampling, and not opened prior to analysis to prese rve its integrity.** 

**Due to differing solubility and diffusion propertie s of gases in liquid matrices at different**  **temperatures, it is possible for the sample to gene rate 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 caus ed by degassing upon cooling the sample**  **should not exceed 5 - 6 mm. When a bubble is presen t, also inspect the cap and septum to**  **ensure that a proper seal was made at the time of s ampling. The presence of a macro bubble in**  **a sample vial generally indicates either improper s ampling technique or a source of gas evolution**  **within the sample. The latter case is usually accom panied by a buildup of pressure within the vial,**  **(e.g. carbonate-containing samples preserved with a cid). Studies conducted by the USEPA**  **(EMSL-Ci, unpublished data) indicate that "pea-size d" 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 s usceptible 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 appro priate. The choice between these**  **alternatives should be based on knowledge of the fi eld conditions, the organic carbon content of** **SW-846 Update V 5021A - 13 Revision 2 July 2014**  **the soil, the specific volatile analytes and concen tration levels of interest, and the intended use of**  **the analytical results. For low level analysis by d irect vapor partitioning, 3 or 4 replicate samples**  **should be collected from each sampling point to all ow for reanalysis, while duplicate samples**  **may be sufficient for high level analysis because t he solvent extract can be diluted and**  **reanalyzed. Additional sample replicates should als o be collected for duplicate and MS/MSD**  **analyses, as well as separate portions for dry weig ht determination. If samples will be analyzed**  **by the low level method but have the potential to c ontain high levels of VOCs, samples may be**  **collected for both low level and high level analysi s. This is due to the difficulty of diluting sample**  **s prepared for low level analysis once they are seale**  **d in the vials.**

**8.3.1 Sampling directly into prepared headspace via ls 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 al tering 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 additi onal benefits of reducing the**  **biodegradation potential of the sample matrix and i ncreasing 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 measure ment and transfer into the sample vials**  **can be minimized by adding it to the vials at the l aboratory and sealing them prior to**  **sending them to the field. Samples should be obtain ed and transferred to a vial rapidly after**  **sampling (<10 seconds) to minimize volatilization l osses. In order to estimate the sample** 

**mass added, t** 

### he v **ial, cap and any added solutions should be tared an d 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 lab oratory must be made aware of the**  **identities and amounts of any reagents added to eac h vial in the field.** 

**8.3.1.1 Use standard glass headspace vials with PTF E 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 h eadspace vial containing 10.0 mL**  **of matrix modifier or reagent water and any pH modi fying chemical preservative**  **used. The samples should be introduced into the via ls gently to reduce agitation**  **which might drive off volatile compounds. Seal imme diately with the PTFE side of**  **the septum facing toward the sample.**

**8.3.2 Sampling directly into empty or prepared head space vials for high level**  **analysis:**

**If high concentrations of VOCs are expected (great er than 200**  μ **g/kg), collection of the sample in an empty headspace vial or a vial con**  **taining 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 g lass headspace**  **vials with PTFE faced septa (other vials may be use d, 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 headspa ce 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 sa mpling (<10 seconds) to minimize**  **volatilization losses, and they should be introduce d into the vials gently to reduce**  **agitation which might drive off volatile compounds. If methanol is added to the vial** **SW-846 Update V 5021A - 14 Revision 2 July 2014**  **prior to the sample, t** 

### he v **ial, cap and methanol should be tared and the masse s**  **recorded prior to and after adding a soil sample to the vial. The recorded mass**  **should be checked by the analyzing laboratory to ve rify that solvent was not lost**  **during shipping and/or storage.**

**8.3.3 Sampling with a sealable, air-tight coring de vice for low or high level**  **analysis:**

**For cohesive soils, soil samples can be taken in ap propriately sized air-tight**  **sealable coring devices for refrigeration and shipp ing to the laboratory, where the samples**  **are further preserved or immediately prepared for a nalysis.** 

**8.3.3.1 Insert a clean coring device into a fresh s urface for sample**  **collection and ensure that no air is trapped betwee n 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 ves sel should be made and any**  **foreign debris should be wiped clean, allowing an a irtight 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 rea gent water for low level analysis,**  **with pH modifying preservative as appropriate, or m ethanol for high level**  **analysis). The coring device must fit into the mout h of the headspace vial or other**  **VOA vial into which the sample is extruded, or loss es of VOCs will result. In order** 

**to estimate the sample mass added, t** 

### he v **ial, cap and any added solutions should be tared and the mass recorded prior to and after a**  **dding 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 t he field (**  e.g. **, 10.0 mL of organic-free reagent water, methanol, or matrix modifying soluti**  **on, 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 abilit y 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 integri ty of the container seal is maintained.**  **Freezing of soil samples is also appropriate provid ed the storage temperature is not lower**  **than the minimum temperature recommended by the man ufacturer 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 an d in sealed headspace vials with reagent**  **water, even if no other chemical preservative is ad ded. 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 cauti onary notes in Table 4-1 of Chapter**  **Four, Method 5035, Appendix A, Table A-1, and the l ist of analytes in Sec. 1.1 of this**  **method pertaining to certain compound classes and a pplicable preservation options that** **SW-846 Update V 5021A - 15 Revision 2 July 2014**  **may affect target analyte stability and analytical holding times. Samples not analyzed within**  **this period should be identified to the data user a nd the results considered minimum values**  **unless it can be demonstrated that the reported VOC concentrations are not adversely**  **affected by preservation, storage and analyses perf ormed outside the recommended**  **holding times.**

**9.0 QUALITY CONTROL**

**9.1 Refer to Chapter One for guidance on quality as surance (QA) and quality control**  **(QC) protocols. It should be noted that several met hods (e.g., Method 8000) also contain general**  **QC criteria and guidance that pertain to the indivi dual 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 ge neral method QC criteria.** 

**Any effort involving the collection of analytical d ata should include development of a**  **structured and systematic planning document, such a s a Quality Assurance Project Plan (QAPP)**  **or a Sampling and Analysis Plan (SAP), which transl ates project objectives and specifications**  **into directions for those that will implement the p roject 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 generat ed. 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 proficienc y with each sample preparation and**  **determinative method combination it utilizes by gen erating data of acceptable accuracy and**  **precision for target analytes in a clean matrix. Th e laboratory must also repeat the demonstration**  **of proficiency whenever new staff members are train ed or significant changes in instrumentation** 

**are made. See Method 8000D, Sec. 9.3 for informatio n on how to accomplish a demonstration of**  **proficiency.**

**9.3 Lower Limit of Quantitation (LLOQ) check standa rd** 

**The laboratory shall establish the LLOQ as the lowe st point of quantitation, which in most** 

**cases, is the lowest concentration in the calibrati on curve. LLOQ verification is recommended for**  **each project application to validate quantitation c apability at low analyte concentration levels.**  **This verification may be accomplished with either c lean 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 les s than the desired regulatory action levels** 

**based on the stated DQOs.**

**In order to demonstrate the entire sample preparati on 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 analyt e(s) of interest at the predicted LLOQ**  **concentration level(s). Alternatively, a representa tive sample matrix may be spiked with the**  **analytes of interest at the predicted LLOQ concentr ation levels. The LLOQ check is carried**  **through the same preparation procedures as environm ental samples and other QC samples.** 

**Recovery of target analytes in the LLOQ check stand ard should be within established**  **in-house limits, or other such project-specific acc eptance limits, to demonstrate acceptable**  **method performance at the LLOQ. Until the laborator y has sufficient data to determine** **SW-846 Update V 5021A - 16 Revision 2 July 2014**  **acceptance limits, the LCS criteria ± 20% may be us ed 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. Addition al information on LLOQ can be found in** 

**8000D, Sec. 9.7.**

**9.4 Initially, before processing any samples, the a nalyst should demonstrate that all**  **parts of the equipment in contact with the sample a nd 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 t here is a change in reagents, a method**  **blank should be prepared and analyzed for the compo unds of interest as a safeguard against**  **chronic laboratory contamination. If a peak is obse rved within the retention time window of any**  **analyte that would interfere with measurement of th at analyte, determine the source and**  **eliminate it, if possible, before analyzing the sam ples. 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 t he method blank from those of any**  **associated samples. Such "blank subtraction" may le ad to negative sample results. If the method**  **blank results do not meet the project-specific acce ptance criteria and reanalysis is not practical,**  **then the data user should be provided with the samp le results, the method blank results, and a**  **discussion of the corrective actions undertaken by the laboratory.** 

**9.5 Sample quality control for preparation and anal ysis** 

**The laboratory must also have procedures for docume nting the effect of the matrix on**  **method performance (precision, bias, method sensiti vity). At a minimum, each batch of 20 or**  **fewer field samples should include at least one met hod blank, a laboratory control sample (LCS),**  **and either a matrix spike/matrix spike duplicate (M S/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 samp les 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 add itional quality assurance practices**  **for use with this method. The specific practices th at are most productive depend upon the needs**  **of the laboratory and the nature of the samples. Wh enever possible, the laboratory should**  **analyze standard reference materials and participat e in relevant performance evaluation studies.** 

**9.7 The laboratory should have quality control proc edures to make sure that sample**  **integrity is not compromised during the sample coll ection 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) ar ea counts for all samples; leaks attributed to a**  **poor seal with the vial caps and septa will be evid ent by low IS area counts. Sample containers** 

**and data results for instances where low IS area co unts are observed and leaks are suspected** 

**should be discarded. Low area counts of the less vo latile internal standards may also be** 

**attributed to matrix effects and should not be conf used with a leaking vial.** **SW-846 Update V 5021A - 17 Revision 2 July 2014**  **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 on ly be monitored through a matrix spike of a**  **sample from every project analytical batch. The spi king solution should be the same as that used**  **to prepare the calibration standards in order to mi nimize sources of variability in evaluating spike**  **recovery. The acceptance criteria shall be those re commended in the determinative method or**  **specified by a properly executed systematic plannin g document. If these criteria cannot be met,**  **the analyst may adjust the pH of the mixture throug h the addition of solid NaHSO**  **4 to excessively** 

**basic mixtures or solid Na 3**  **PO 4**  **•12H 2**  **O to excessively acidic mixtures. After this is don e, the**  **matrix spike analysis should be repeated with an un analyzed 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, th e data user must be made aware that the**  **initial matrix spike failed and the pH adjustment w as 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 st andardization and refer to the**  **appropriate determinative method for additional cal ibration 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 s creening purposes. The procedure for sample**  **preparation depends upon the matrix of the sample a nd the target analyte concentration range.**  **To minimize loss of VOCs from the samples or exchan ge 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 th e gas phase contents of the**  **vial to the silicone material backing the septum. T his material may absorb some of**  **the gas phase VOCs in the vial, causing problems wi th calibration, measurement in**  **samples, spike recovery,** etc. **, as a function of exposure time. This problem is**  **generally worse for the higher molecular weight VOC s 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 aft er spiking if these VOCs are**  **analytes of interest.**

**11.1.1 Water samples - The preparation of water sam ples inevitably involves**  **some sample manipulation and exposure to the labora tory atmosphere. Extreme caution**  **should be exercised to minimize any volatilization of analytes out of the sample contents**  **and into the laboratory atmosphere. The first preca ution is to prepare the water samples**  **immediately after removal from cold storage. The de creased temperature reduces analyte**  **volatility, and the benefits of this are substantia lly greater than the inaccuracies introduced**  **by measuring sample volume at lower temperatures. SW-846 Update V 5021A - 18 Revision 2**  **July 2014 11.1.1.1 Add 5 mL of the matrix modifier solution t**  **o a headspace vial (Sec. 6.0), if used. Otherwise, add 5 mL reagent wa**  **ter. Set the septum and crimp top onto the vial and move the crimping tool to a r**  **eadily 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 rem ove 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 stand ard and/or surrogate standard**  **solution, if used, and immediately seal the vial. T his process of taking an aliquot**  **destroys the validity of the liquid sample for futu re analysis. Therefore, if there is**  **only one VOA vial, the analyst should prepare a sec ond 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 anal yst has determined that the first**  **sample has been analyzed properly. If a second anal ysis is needed, it should be**  **completed within 24 hr.**

**11.1.2 Soil samples - If the sample will be analyze d 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 anal ysis, proceed to Sec.11.4.** 

**11.1.2.1 If the soil sample was placed into a heads pace vial with neither**  **water nor matrix modifier and the sample mass was n ot 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 displ acing 10 mL of headspace.** 

**CAUTION : Only open and prepare one vial at a time to mini**  **mize loss of volatile**

**organics.**

**11.1.2.2 If the soil sample was placed into a heads pace vial with**  **reagent water or the matrix modifier solution at th e time of sampling, first weigh the**  **sealed vial and its contents to 0.01 g. If the matr ix 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 blan**  **k 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 modi**  **fying solution in the samples. (Although this approach may introduce some error in**  **to the sample results, that error should be much less than the changes that will occu**  **r 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, t**  **hey should be added at this**

**time.**

**11.2 The low-concentration method utilizing an equi librium headspace technique is**  **found in Sec. 11.3 and sample preparation for the h igh-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). Se e Method 8000 for guidance on the selection** 

**of a GC or GC/MS determinative method. For the anal ysis of gasoline, use Method 8021 with**  **GC/PID (photoionization detector) for BTEX (benzene, toluene, ethylbenzene, and xylen**  **es) in**  **series with Method 8015 with the GC/FID (flame ioni zation detector) detector for other gasoline**  **components. If GC/MS analysis is preferred, follow Method 8260. For the analysis of MTBE and** **SW-846 Update V 5021A - 19 Revision 2 July 2014**  **the other fuel oxygenates, use either Method 8015 w ith 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 m ethod.** 

**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 s pecific information on calibration**  **and preparation of standards. Normally, external st andard calibration is preferred for the**  **GC methods because of possible interference problem s with internal standards. If**  **interferences are not a problem, based on historica l data, internal standard calibration is**  **acceptable. The GC/MS methods normally utilize inte rnal standard calibration. The GC/MS**  **methods require instrument tuning prior to proceedi ng with calibration.** 

**11.3.1.1 GC/MS tuning**

**If a GC/MS determinative method is employed, prepar e a headspace vial**  **containing reagent water and the amount of 4-bromof luorobenzene (BFB) listed in** 

**the determinative method.**

**11.3.1.2 Initial calibration**

**Prepare a minimum of five headspace vials for calib ration 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 m ixing 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 acc ording 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, prepar e a second headspace vial**  **containing reagent water and the amount of BFB list ed 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 Se c. 16 and employing Method 8260 as**  **the determinative method. If other headspace system s and determinative methods are**  **utilized, it is recommended that the manufacturer's headspace operating conditions be**  **followed, provided that they are appropriate for th e determinative method to be employed.** 

**11.3.2.1 Mix the samples (on a rotator or shaker) f or at least 2 min.**  **For samples that contain water insoluble materials, care must be exercised during**  **mixing to prevent this material from adhering to th e inner surface of the vial seal;**  **otherwise the sampling needle can become contaminat ed 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 sampl e.** **SW-846 Update V 5021A - 20 Revision 2 July 2014**  **Place the vials in the autosampler carrousel at roo m 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 pr**  **essure of 10 psi.**

**11.3.2.2 A representative and reproducible sample o f 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 deter minative method of** 

**choice.**

**NOTE : If maintaining a specified pH is critical to qua**  **lity assured measurement of**

**the analyte(s) of concern (Sec. 4.7), the pH of eac h sample should be**  **verified. If basic preservation is necessary, the p H 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 provid e 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 t he nearest 0.01 g. Add twice the volume**  **of methanol as the nominal sample mass to a tared V OA 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 obta in 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-fre e reagent water was added to the sample**  **vials, subsamples for high concentration analysis s hould be taken from the separate VOA**  **vials collected without matrix modifying solution o r reagent water as described in Sec. 8.3.2**  **or from the vials collected for dry solids determin ation. Transfer approximately 5 g of**  **sample from the 40 or 60 mL VOA vial into a tared V OA vial containing 10.0 mL of**  **methanol, seal the vial, and reweigh to estimate th e 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 mo re details.** 

**11.4.3 Mix by shaking for 10 min at room temperatur e. Decant 2 mL of the**  **methanol extract to a screw-top vial with PTFE-face d septa and seal. Withdraw 10**  μ **Land 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 a**  **dded provided the methanol content does not adversely affect the analyte responses (re**  **fer to Sec. 7.4.1). Add internal standards and/or surrogates as appropriate, and ana**  **lyze by the headspace procedure by placing the vial into the autosampler and proceedin**  **g with Sec. 11.3.2.1. SW-846 Update V 5021A - 21 Revision 2**  **July 2014 12.0 DATA ANALYSIS AND CALCULATIONS** 

**There are no data analysis and calculation steps d irectly associated with this procedure.**  **Follow the directions given in the determinative me thod.** 

**13.0 METHOD PERFORMANCE**

**13.1 Performance data and related information are p rovided in SW-846 methods only as**  **examples and guidance. The data do not represent re quired performance goals for users of the**  **methods. Instead, performance goals should be devel oped 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 gro undwater 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, mult iple groundwater vials were collected at**  **each sampling point. The samples were analyzed by t hree independent laboratories. All of the**  **laboratories used this method for sample preparatio n, and each laboratory used a different**  **determinative method. One laboratory used a GC/MS t echnique with a quadrupole mass**  **spectrometer (Method 8260), another used a GC/MS te chnique 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 Figure s 1 through 6. Since all three laboratories**  **followed the same project plan and the same data qu ality objectives, the data generated by the**  **three laboratories is mutually comparable, even tho ugh 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 Fig ure 7, while those from site B are shown in**  **Figure 8. Figure 8 shows that one of the labs had p oor recovery for MTBE. However, the**  **recovery of the other ethers was acceptable, indica ting 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 an d 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 g eneration. Numerous opportunities for pollution**  **prevention exist in laboratory operation. The EPA h as established a preferred hierarchy of**  **environmental management techniques that places pol lution prevention as the management**  **option of first choice. Whenever feasible, laborato ry 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 tha t 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 Ch emical Society (ACS), Committee**  **on Chemical Safety, http://portal.acs.org/portal/fileFetch/C/WPCP_01229**  **0/pdf/WPCP_012290.pdf. SW-846 Update V 5021A - 22 Revision 2**  **July 2014 15.0 WASTE MANAGEMENT** 

**The Environmental Protection Agency requires that l aboratory waste management**  **practices be conducted consistent with all applicab le 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 lett er and spirit of any sewer discharge permits**  **and regulations, and by complying with all solid an d hazardous waste regulations, particularly the**  **hazardous waste identification rules and land dispo sal 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 Vola tile 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 Labor atory, Cincinnati, OH, December,** 

**1992.**

**2. B. V. Loffe, and A. G. Vitenberg, "Headspace Ana lysis 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 Fu el 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 presentat ion describing changes to**  **method 5021, “Proposed Changes to SW-846 method 502 1A, VOCs by Static**  **Headspace** ” **, March 1, 2012. SW-846 Update V 5021A - 23 Revision 2**  **July 2014 17.0 TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION D**  **ATA**

**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**SW-846 Update V 5021A - 24 Revision 2 July 2014**  **FIGURE 2**

**EXAMPLE RESULTS FROM SITE A STUDY FOR** TERT **AMYL METHYL ETHER**



## Sample**SW-846 Update V 5021A - 25 Revision 2 July 2014**  **FIGURE 3**

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



## Sample**SW-846 Update V 5021A - 26 Revision 2 July 2014**  **FIGURE 4**

**EXAMPLE RESULTS FROM SITE B STUDY FOR BENZENE**



## Sample**SW-846 Update V 5021A - 27 Revision 2 July 2014**  **FIGURE 5**

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



## Sample**SW-846 Update V 5021A - 28 Revision 2 July 2014**  **FIGURE 6**

**EXAMPLE RESULTS FROM SITE B STUDY FOR** TERT **-BUTYL ALCOHOL**



## Sample**SW-846 Update V 5021A - 29 Revision 2 July 2014**  **FIGURE 7**

**EXAMPLE PERCENT RECOVERIES FROM THE MATRIX SPIKE ST UDIES OF SITE A** **SW-846 Update V 5021A - 30 Revision 2 July 2014**  **FIGURE 8**

**EXAMPLE PERCENT RECOVERIES FROM THE MATRIX SPIKE ST UDIES OF SITE B** **SW-846 Update V 5021A - 31 Revision 2 July 2014**  **Appendix A:**

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

**1. Improved overall method formatting for consisten cy with new SW-846 methods style guidance.**  **The format was updated to Microsoft Word .docx.**

**2. Minor editorial and technical revisions were mad e throughout to improve method clarity.**  **3. The revision number was changed to 2 and the dat e 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 sy**  **stem for analytes in Secs. 1.1 and 1.2 to provide an indication of which VOC responses were i**  **mproved 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 pr**  **eparation to Sec. 7.4.1 that allowed for multiple calibration levels prepared by adding different vol**  **umes of one or more stock solutions. 9. Clarified in Sec. 1.4 the major sources of measu**  **rement bias expected for sample analysis using this method, as well as which sources of meas**  **urement bias the matrix modifier may improve, which sources of measurement bias may be m**  **ade worse by the matrix modifier, and under what other circumstances not adding the matri**  **x modifier may be appropriate. 10. Added a caution after Sec. 11.1 regarding the e**  **xpected effect of compromising the PTFE face of a vial seal on recovery of oil soluble target an**  **alytes.**