**SW-846 Update V 3572 - 1 Revision 1 October 2012**  **METHOD 3572**

**EXTRACTION OF CHEMICAL AGENTS FROM WIPE SAMPLES USI NG** 

**MICROEXTRACTION**

**SW-846 is not intended to be an analytical trainin g 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 o f 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 gu idance 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 o nly, and are not intended to be and must not**  **be used as absolute QC acceptance criteria for the purposes of laboratory accreditation.** 

**1.0 SCOPE AND APPLICATION**

**1.1 This method describes the extraction of chemic al agents from wipe samples using**  **a microextraction technique. The following compoun ds have been determined by this method:** 

**Compound Name CAS No. a** 

**GB (** o **-Isopropyl methylphosphonofluoridate) 107-44-8 VX (O-Ethyl S-2-diisopropylaminoethyl methyl phosph**  **onothiolate) 50782-69-9 HD [Bis(2-chloroethyl)sulfide]**  **505-60-2**

**a Chemical Abstracts Service Registry Number**  **Additionally, this method may be applicable to othe r chemically similar compounds and**  **chemical agent degradation products. For a summary of changes in this version, please see**  **Appendix A at the end of this document. 1.2 Other solvent systems may be employed in place**  **of those described here. For any solvent system used, including those mentioned in t**  **he method, one needs to demonstrate adequate performance for the analytes of interest.**  **1.3 There is a risk to the analyst of exposure to chemical agents. The analyst should**  **pay special attention to the safety information in Sec. 5.0.** **SW-846 Update V 3572 - 2 Revision 1 October 2012**  **1.4 Prior to employing this method, analysts are a dvised 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 g uidance. 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 analys t for demonstrating that the techniques**  **employed are appropriate for the analytes of intere st, in the matrix of interest, and at the levels**  **of concern. In addition, analysts and data users are advised t**  **hat, 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 me**  **thod 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 for t**  **he intended application. 1.5 This method is restricted to use by, or under**  **supervision of, appropriately experienced and trained personnel. Each analyst mu**  **st demonstrate the ability to generate acceptable results with this method.** 

**1.6 WARNING: The toxicity of these chemical warfare agents pre**  **sents the worker with hazards unfamiliar to most experienced laboratory p**  **ersonnel. Special techniques and precautions must be used even for the simplest proc**  **edures involving these agents (see Ref. 1 for additional guidance).** 

**2.0 SUMMARY OF METHOD 2.1 This method provides the procedures for sample**  **collection and extraction of the referenced compounds from wipe samples. A separate**  **extract will be required for each agent to be analyzed.**  **2.2 Materials are surface wiped using a gauze pad (2” x 2” pad). After wiping a**  **surface area, usually 10 cm x 10 cm, the pad is pla ced into a labeled vial.**  **2.3 Samples are extracted with 4 mL of 10% 2-propa nol (IPA) in dichloromethane by**  **vortex mixing and filtered, if necessary. 2.4 An optional water wash is included for VX that**  **back-extracts the compound from heavy organics that would interfere with the assay.**  **An optional column cleanup procedure utilizes a Carboprep90 column and a silica column t**  **o separate GB from heavy organics, if needed. Suitable solvents are used to elute the ex**  **tract first through the Carboprep90 column, then the silica column.** 

**3.0 DEFINITIONS Refer to Chapter One and the manufacturer's instru**  **ctions for definitions that may be relevant to this procedure.** **SW-846 Update V 3572 - 3 Revision 1 October 2012**  **4.0 INTERFERENCES 4.1 Solvents, reagents, glassware, and other sampl**  **e 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 in all-glass systems 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 informa**  **tion regarding potential interferences. 4.2 Other phosphorous- and sulfur-containing compo**  **unds can interfere with the method performance and affect the result.**  **4.3 Interferences that can cause the chemical agen ts to decompose include moisture,**  **light, elevated temperatures, and an improper extra ction solvent pH range. The stability of the**  **chemical agents noted in this method is contingent on maintaining the pH ranges as indicated in**  **Sec. 8.2. 4.4 Samples with high organic loading can mask or**  **elute with the agent analyte.**

**5.0 SAFETY**

**WARNING : The toxicity of these chemical warfare agents pr**  **esents the worker with hazards unfamiliar to most experienced laboratory personnel**  **. Special techniques and precautions must be used even for the simplest procedures involving**  **these agents. 5.1 This method does not address all safety issues**  **associated with its use. The laboratory is responsible for maintaining a safe wo**  **rk environment and a current awareness file of OSHA regulations regarding the safe handling of**  **the chemicals listed in this method. A reference file of material safety data sheets (MSDS**  **s) should be available to all personnel involved in these analyses.**  **5.2 Personal protective equipment (PPE) requiremen ts include safety glasses, lab**  **coat, and protective gloves. The availability of e mergency response equipment and support**  **personnel should be as indicated in a laboratory ch emical hygiene plan.**  **5.3 Exposure to chemical agent material is possibl e from contact. Respiratory**  **exposure can result from spills or improper use of ventilation control.**  **5.4 Risk is primarily associated with compromise o f protective gloves. Compromise is**  **most likely to occur as agent vials are opened.**

**6.0 EQUIPMENT AND SUPPLIES 6.1 The mention of trade names or commercial produ**  **cts in this manual is for illustrative purposes only, and does not constitute an EPA endor**  **sement or exclusive recommendation for SW-846 Update V 3572 - 4 Revision 1**  **October 2012 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 of the common labor atory glassware (e.g., beakers and**  **flasks) that might be used. 6.2 Personal protective equipment** 

**6.3 Vials, 1-, 3-, and 6-dram for sample collectio n**  **6.4 Vials, 1-dram for extracts 6.5 Gauze pads, non sterile, 100% cotton, approxim**  **ately 2” x 2” or 4” x 4” squares available Edwards Medical Supply, or a suitable equ**  **ivalent. For each sampling event or a specific project application gauze pads from the sa**  **me manufacturing lot should be used. 6.6 Analytical balance, capable of measuring to th**  **e nearest mg 6.7 Pasteur pipettes, 5 3⁄4,” Fisherbrand, or equiva**  **lent 6.8 Syringes, 10-μl and 50-μl used for preparing s**  **pikes and surrogates 6.9 Volumetric glassware, 2-, 5-, and 10-mL used f**  **or preparing spikes and surrogates 6.10 BD syringe filter (10-mL Luer-Lok)**  **6.11 Whatman nylon syringe filter, 0.45-μm pore si ze, or equivalent**  **6.12 Vortex mixer, benchtop, or as noted in Sec. 6 .13**  **6.13 Centrifuge, benchtop 6.14 pH test strips** 

**7.0 REAGENTS AND STANDARDS 7.1 Reagent-grade chemicals must be used in all te**  **sts. Unless otherwise indicated, it is intended that all reagents conform to the specif**  **ications of the committee on Analytical Reagents of the American Chemical Society, where su**  **ch specifications are available. Other grades may be used, provided it is first ascertaine**  **d that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of**  **the determination. 7.2 Dichloromethane (DCM), CH**  **2 Cl**  **2 , optima grade or equivalent**  **7.3 2-Propanol (IPA), (CH 3**  **) 2**  **CHOH, optima grade or equivalent 7.4 1 N Sodium hydroxide, NaOH** **SW-846 Update V 3572 - 5 Revision 1 October 2012**  **7.5 Sodium chloride, NaCl**

**7.6 Saturated Glacial Acetic Acid/NaCl solution. D issolve 7 g of NaCl in 35 mL of glacial** 

**acetic acid in a 40-mL vial 7.7 Isopropyl methylphosphonofluoridate; Sarin (GB**  **)**

**7.8 O-ethyl S-(2-diisopropylaminoethyl)methylphosp honothioate (VX)** 

**7.9 Bis(2-chloroethyl)sulfide (HD) 7.10 Diisopropyl fluorophosphonate (DFP), C**  **6 -H**  **14 -F-O**  **3 -P**  **7.11 2-Chloroethyl ethyl sulfide (CEES), C 4**  **-H 9**  **-Cl-S 7.12 Diethyl ethylthiophosphonate (DEETP)** 

**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 req**  **uirements are specified in the regulation, follow those requirements. In the absence of speci**  **fic regulatory requirements, use the following information as guidance in determining the sample c**  **ollection, preservation and storage requirements.**  **8.1 This method is a microextraction technique in which a particular surface area is**  **wiped with either a 2” x 2” or 4” x 4” gauze pad an d extracted with 4.0 mL of 10% IPA in DCM.**  **Because of this, sample collection plans should con sider sufficient replicates.**  **8.2 Holding times 8.2.1 Samples for GB, HD and VX assay must be ext**  **racted within 7 days of collection. Extraction times of less than 3 da**  **ys are preferred. Extracts must be analyzed within 14 days of extraction.**  **8.2.2 GB undergoes rapid hydrolysis to form hydro gen fluoride, isopropyl**  **methyl phosphonic acid and other compounds. Condi tions of pH within a range of 3.5 to**  **5 will slow this decomposition rate. Stability in organic extracts exceeds 28 days.**  **8.2.3 HD undergoes hydrolysis to form thiodiglyco l and other compounds.**  **Conditions of pH within a range of 3.5 to 5 will s low decomposition rate. Chloride ion**  **can be added to reduce the effects of metal cation s. Stability in organic extracts**  **exceeds 28 days. 8.2.4 VX undergoes very rapid hydrolysis under ex**  **tremely basic conditions, with a half-life of 16 minutes at pH 13 and 1.3 min**  **utes at pH 14. Optimal pH for VX stability (for a half-life of approximately 350 day**  **s) was determined to be within a range of 8 to 9. Stability in organic extracts exceeds 28 day**  **s. Partitioning is present with non-polar SW-846 Update V 3572 - 6 Revision 1**  **October 2012 solvents (hexane).**  **8.3 Sample collection The exact number of samples that may be necessary**  **for a particular sampling event, such as possibly collecting samples in duplicate, should**  **be documented in the appropriate project planning documents. It is also important to unders**  **tand that duplicate wipe samples may not always yield consistent results for precision purpo**  **ses. 8.3.1 Place 1 mL of IPA onto gauze pad.**  **8.3.2 Wipe a surface area of 10 cm x 10 cm. 8.3.3 Place the gauze pad into a labeled vial.** 

**8.3.4 Record the vial identification number on th e chain of custody and the** 

**sample label. 8.3.5 One additional sample from the same general**  **location should be**

**designated as a duplicate for each group of twenty or fewer samples. Two empty**  **vials designated as a blank and LCS, both containin g a clean IPA-soaked gauze**  **pad added at the time of sample collection, should be returned with each group of**  **twenty or fewer samples.**

**9.0 QUALITY CONTROL 9.1 Refer to Chapter One for guidance on quality a**  **ssurance (QA) and quality control (QC) protocols. When inconsistencies exist between**  **QC guidelines, method-specific QC criteria take precedence over both technique-specif**  **ic criteria and those criteria given in Chapter One and technique-specific QC criteria take precede**  **nce over the criteria in Chapter One. Any effort involving the collection of analytical data**  **should include development of a structured and systematic planning document, such as a Laboratory/**  **Monitoring Quality Assurance Plan (LMQAP) or a Sampling and Analysis Plan (SAP), whic**  **h 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 as**  **surance program. The laboratory should also maintain records to document the quality of th**  **e data generated. All data sheets and quality control data should be maintained for reference or**  **inspection.**

**9.2 Initial demonstration of proficiency and lower limit of quantitation (LLOQ)**  **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. T he laboratory must also repeat the**  **demonstration of proficiency whenever new staff mem bers 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. SW-846 Update V 3572 - 7 Revision 1**  **October 2012 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 quantitati**  **on capability at low analyte concentration levels. An LLOQ check standard (not part of an initial cali**  **bration) is prepared by spiking a clean control material with the analyte(s) of interest at the pre**  **dicted LLOQ concentration level(s). The LLOQ check is carried through the same preparation proce**  **dures as environmental samples and other QC samples. Recovery of target analytes in the LLO**  **Q 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 t**  **he laboratory has sufficient data to determine acceptance limits, the LCS criteria ± 20%**  **may be used for the LLOQ acceptance criteria. Additional information on LLOQ can be fo**  **und in 8000D, Section 9.7. 9.3 Initially, before processing any samples, the**  **analyst 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, an**  **d when there is a change in reagents, a method blank should be prepared and analyzed for th**  **e compounds of interest as a safeguard against chronic laboratory contamination.**  **9.4 Any method blanks, matrix spike samples, or re plicate samples should be**  **subjected to the same analytical procedures (Sec. 1 1.0) as those used on actual samples.**  **9.5 Standard quality assurance practices should be used with this method as included**  **in appropriate systematic planning documents and la boratory SOPs. All instrument operating**  **conditions should be recorded. 9.6 Also see Method 3500 for QC procedures related**  **to extraction and sample preparation procedures and refer to the determinati**  **ve methods to be used for determinative QC procedures.**  **9.7 As noted earlier, use of any extraction techni que, including solvent extraction,**  **should be supported by data that demonstrate the pe rformance of the specific solvent system**  **and operating conditions for the analytes of intere st, at the levels of interest, in the sample**  **matrix. 9.8 All field and QC samples should be spiked with**  **an appropriate mix of surrogate compounds, if available, in order to track extracti**  **on efficiency. 9.9 Any reagent blanks, matrix spike, and replicat**  **e samples should be subjected to exactly the same analytical procedures as those use**  **d on field samples.**

**10.0 CALIBRATION AND STANDARDIZATION Calibration is not required for this method.** 

**11.0 PROCEDURE 11.1 Spike the matrix spike, matrix spike dup**  **licate or laboratory control spike (LCS) SW-846 Update V 3572 - 8 Revision 1**  **October 2012 with agent. Record spike amounts into controlled n**  **otebook. 11.1.1 Suggested GB spike is 40 ng.**  **11.1.2 Suggested VX spike is 40 ng. 11.1.3 Suggested HD spike for FPD is 120 ng and f**  **or GC/MS is 40 ng. 11.2 Spike all samples with appropriate surrogates** 

**. 11.2.1 Suggested 40 ng of DFP for GB samples.**  **11.2.2 Suggested 40 ng of DEETP for VX samples. 11.2.3 Suggested 120 ng of CEES for HD FPD and 40**  **ng for GC/MS.**

**11.3 Add 4.0 mL of 10% IPA in dichloromethane to a ll samples. For VX samples, add**  **200 μL of 1N sodium hydroxide solution to ensure th at the extract is basic, taking care not to**  **overshoot desired pH. More sodium hydroxide may be used if needed. The pH range for VX**  **should be between 8-10. 11.3.1 Check pH with pH paper.** 

**11.3.2 Mix on a vortex mixer for 30 seconds. 11.3.3 Centrifuge the sample for 1 minute at 2000**  **rpm, if necessary. 11.3.4 If filtration is necessary, filter the sol**  **vent extract into another vial. 11.3.5 Store the extract in a refrigerator at <6**  **°C until analysis.**

**12.0 DATA ANALYSIS AND CALCULATIONS There are no determinative data analysis and calcu**  **lation steps directly associated with this procedure. Follow the directions in the deter**  **minative 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 r equired performance criteria for users of**  **the methods. Instead, performance criteria should be developed on a project-specific basis,**  **and the laboratory should establish in-house QC per formance criteria for the application of this**  **method. These performance data are not intended to be and must not be used as absolute QC**  **acceptance criteria for the purposes of laboratory accreditation.**  **13.2 Refer to the appropriate determinative method for performance data examples and**  **guidance. SW-846 Update V 3572 - 9 Revision 1**  **October 2012 14.0 POLLUTION PREVENTION**  **14.1 Pollution prevention encompasses any techniqu e 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 operations. The EPA has established a preferred hierarchy of**  **environmental management techniques that places pol lution prevention as the management**  **option of first choice. Whenever feasible, laborat ory 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 th at 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.**

**15.0 WASTE MANAGEMENT The Environmental Protection Agency requires that**  **laboratory 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 d**  **isposal restrictions. For further information on waste management, consult the ACS publication li**  **sted in Sec. 14.2.**

**16.0 REFERENCES 1. Applicable documents to support the occupational**  **health program when dealing with chemical agents include AR11-34 (The Army Respirat**  **ory Protection Program; AR 40-5 (Preventive Medicine); DA Pam 40-8 (Occupational H**  **ealth guidelines for the evaluation and Control of Occupational Exposure to Nerve Agen**  **ts GA, GB, GC, and VX.) and DA Pam 40-173 (Occupational Health Guidelines for the**  **Evaluation and Control of Occupational Exposure to Mustard Agents H, HD, and**  **HT). 2. Development and Evaluation of an Analytical Meth**  **od for Determination of GB, VX, and HD in Concrete, SwRI Final Report to PM-ECW, Willi**  **am S. Williamson, Jr. Joseph H. Brewer.**  **3. Development and Evaluation of an Analytical Meth od for Determination of GB, VX, and**  **HD in Coral, SwRI Final Report to PM-ECW, William S. Williamson, Jr., Joseph H.**  **Brewer. 4. Development and Evaluation of an Analytical Meth**  **od for Determination of GB, VX, and HD in Charcoal, SwRI Final Report to PM-ECW, Micha**  **el G. MacNaughton, Ph.D., P.E., William S. Williamson, Jr., Joseph H. Brewer.** **SW-846 Update V 3572 - 10 Revision 1 October 2012**  **5. Development and Evaluation of an Analytical Meth od for Determination of GB, VX, and**  **HD on Surfaces, SwRI Final Report to PM-ECW, Carte r Crigler.**  **6. Laboratory Monitoring and Quality Assurance Plan dated June 2004, Department of**  **Army, Chemical Material Agency.**

**17.0 TABLES, DIAGRAMS, FLOW CHARTS, AND VALIDATION DATA**  **There are no tables or figures associated with thi s method.** **SW-846 Update V 3572 - 11 Revision 1 October 2012**  **Appendix A:**

**Summary of Revisions to Method 3572 (as compared to previous Revision 0, July, 2007)**  **1. Improved overall method formatting for consisten cy with new SW-846 methods style**  **guidance. The format was updated to Microsoft Word 2007.docx.**  **2. Sections 7.2 and 7.3, added the words “or equiva lent” to Optima grade description as**  **that is a trademarked term of Thermo/Fisher Scienti fic. Optima grade is a high purity**  **gas chromatography grade of solvent. 3. Updated VX stability information has been added**  **to Sec. 8.2.4. 4. LLOQ language added to Section 9.2.** 

**5. Minor editorial and technical revisions were mad e throughout to improve method clarity.**