522-1 EPA/600/R-08/101

METHOD 522 DETERMINATION OF 1,4-DIOXANE IN DRINKIN G WATER BY

SOLID PHASE EXTRACTION (SPE) AND GAS CHROMATOGRAPHY / MASS SPECTROMETRY (GC/MS) WITH SELECTED ION MONITORING (SIM)

Version 1.0

September, 2008

Jean W. Munch and Paul E. Grimmett

NATIONAL EXPOSURE RESEARCH LABORATORY

OFFICE OF RESEARCH AND DEVELOPMENT

U. S. ENVIRONMENTAL PROTECTION AGENCY

CINCINNATI, OHIO 45268522-2 METHOD 522

DETERMINATION OF 1,4-DIOXANE IN DRINKING WATER BY S OLID PHASE EXTRACTION (SPE) AND GAS CHROMATOGRAPHY/MASS SPECTR OMETRY

(GC/MS) WITH SELECTED ION MONITORING (SIM)

1. SCOPE AND APPLICATION

1.1 This is a gas chromatography/mass spectrometry (GC/MS) method for the determination of 1,4-dioxane (CASRN 123-91-1) in dr inking water. Accuracy and precision data have been generated in reagent water , finished ground and surface waters. Although this method was developed and dem onstrated using selected ion monitoring (SIM) GC/MS for maximum sensitivity, it can also be used with full scan GC/MS if the sensitivity achieved meets the user’s data requirements.

1.2 The Minimum Reporting Level (MRL) is the lowest analyte concentration that meets Data Quality Objectives (DQOs) that are developed b ased on the intended use of this method. Two single laboratory Lowest Concentration Minimum Reporting Levels (LCMRLs) of 0.036 and 0.047 μ g/L have been determined in reagent water. The single laboratory LCMRL is the lowest true concentr ation for which the future recovery is predicted to fall, with high confidence (99%), between 50 and 150% recovery. The procedure used to determine the LCMR Ls is described elsewhere. 1

1.3 Laboratories using this method will not be required to determine the LCMRL for this method, but will need to demonstrate that their lab oratory MRL for this method meets the requirements described in Section 9.2.4.

1.4 Determining the Detection Limit (DL) for analytes i n this method is optional (Sect. 9.2.6). Detection limit is defined as the statisti cally calculated minimum concentration

that can be measured with 99% confidence that the r eported value is greater than zero. 2
The DL is compound dependent and is dependent on ex traction efficiency, sample matrix, fortification concentration, and instrument performance.

1.5 This method is intended for use only by analysts sk illed in solid phase extraction (SPE), the operation of GC/MS instruments, and the interpretation of the associated

data.

1.6 METHOD FLEXIBILITY – In recognition of technolo gical advances in analytical systems and techniques, the laboratory is permitted to modify the GC column, GC conditions and MS conditions (Sect. 9.4). Changes may not be made to sample collection and preservation (Sect. 8), the quality control (QC) requirements (Sect. 9), or to the sample extraction steps (Sect. 11). Meth od modifications should be considered only to improve method performance. Mod ifications that are introduced in the interest of reducing cost or sample processing time, but result in poorer method performance, should not be used. For example, modi fications should not sacrifice522-3 chromatographic separations in the interest of meth od turnaround time. Because the method analyte, surrogate analyte (SUR) and interna l standard (IS) have only very low mass ions in their mass spectra, and SIM is being u sed, it is important to strive for chromatographic separation from potential interfere nces. In all cases where method modifications are proposed, the analyst must perfor m the procedures outlined in the initial demonstration of capability (IDC; Sect. 9.2 ), verify that all QC acceptance criteria in this method (Sect. 9) are met, and demo nstrate that method performance can be verified in a real sample matrix (Sect. 9.3.7 an d 9.4).

NOTE: The above method flexibility section is intended as an abbreviated summation of method flexibility. Method Sections 4-12 provid e detailed information of specific portions of the method that may be modified. If th ere is any perceived conflict between the general method flexibility statement in this section and specific information in Sections 4-12, Sections 4-12 superse de Section 1.6.

2. SUMMARY OF METHOD

2.1 A water sample that has been dechlorinated and preserved with a microbial inhibitor is fortified with the isotopically labeled SUR, 1,4-di oxane- d 8 . The sample is extracted by one of two SPE options. In option 1, a 500-mL s ample is passed through an SPE cartridge containing 2 g of coconut charcoal to ext ract the method analyte and SUR. In option 2, a 100-mL sample is extracted on a Wate rs AC-2 Sep-Pak or Supelco Supelclean ENVI-Carb Plus cartridge. In either opt ion, the compounds are eluted from the solid phase with a small amount of dichlor omethane (DCM), approximately 9 mL or 1.5 mL, respectively. The extract volume i s adjusted, and the IS, tetrahydrofuran- d 8 (THF- d 8 ), is added. Finally, the extract is dried with an hydrous sodium sulfate. Analysis of the extract is perform ed by GC/MS. The data provided in this method were collected using splitless injectio n with a high-resolution fused silica capillary GC column that was interfaced to an MS op erated in the SIM mode. The analyte, SUR and IS are separated and identified by comparing the acquired mass spectra and retention times to reference spectra an d retention times for calibration standards acquired under identical GC/MS conditions . The concentration of the analyte is determined by comparison to its response in calibration standards relative to the IS. Although the performance data presented in Section 17 of this method were

obtained in the SIM mode for maximum method sensiti vity, the sample extract analysis may also be performed in full scan mode if the sensitivity achieved meets the data user’s requirements.

3. DEFINITIONS

3.1 ANALYSIS BATCH – A set of samples that is analy zed on the same instrument during a 24-hour period that begins and ends with t he analysis of the appropriate Continuing Calibration Check (CCC) Standards. Addi tional CCCs may be required depending on the length of the analysis batch and/o r the number of Field Samples.522-4

3.2 CALIBRATION STANDARD (CAL) – A solution prepare d from stock standard solution(s) and the ISs and SURs. The CAL solution s are used to calibrate the instrument response with respect to analyte concent ration.

3.3 CONTINUING CALIBRATION CHECK (CCC) STANDARD – A cal ibration standard containing the method analyte, IS and SUR which is analyzed periodically to verify the accuracy of the existing calibration for those analytes.

3.4 DETECTION LIMIT (DL) – The minimum concentration of an analyte that can be identified, measured and reported with 99% confiden ce that the analyte concentration is greater than zero. This is a statistical determ ination (Sect. 9.2.6), and accurate quantitation is not expected at this level. 2

3.5 EXTRACTION BATCH – A set of up to 20 Field Samp les (not including QC samples) extracted together by the same person(s) d uring a work day using the same lot of SPE devices, solvents, SUR solution, and for tifying solutions. Required QC samples include Laboratory Reagent Blank (LRB), Lab oratory Fortified Blank (LFB), Laboratory Fortified Sample Matrix (LFSM), and eith er a Field Duplicate (FD1 and FD2) or Laboratory Fortified Sample Matrix Duplicat e (LFSMD).

3.6 FIELD DUPLICATES (FD1 and FD2) – Two separate s amples collected at the same time and place under identical circumstances, and t reated exactly the same throughout field and laboratory procedures. Analyses of FD1 a nd FD2 give a measure of the precision associated with sample collection, preser vation, and storage, as well as with laboratory procedures.

3.7 INTERNAL STANDARD (IS) – A pure analyte, which is extremely unlikely to be found in any sample, which is added to an extract o r standard solution in a known amount and used to measure the relative responses o f the method analyte and SUR. The IS must be an analyte that is not a sample comp onent.

3.8 LABORATORY FORTIFIED BLANK (LFB) – An aliquot o f reagent water or other blank matrix to which known quantities of the metho d analyte and all the preservation compounds are added. The LFB is processed and anal yzed exactly like a sample, and its purpose is to determine whether the methodology is in control, and whether the laboratory is capable of making accurate and precis e measurements.

3.9 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – An aliquot of a Field Sample to which known quantities of the method anal yte and all the preservation compounds are added. The LFSM is processed and ana lyzed exactly like a sample, and its purpose is to determine whether the sample matrix contributes bias to the analytical results. The background concentrations of the analyte in the sample matrix must be determined in a separate aliquot or duplica te sample and the measured values in the LFSM corrected for background concentrations

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3.10 LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE ( LFSMD) – A Field Sample Duplicate of the Field Sample used to prepar e the LFSM, which is fortified, extracted and analyzed identically to the LFSM. Th e LFSMD is used instead of the Field Duplicate to access method precision and accu racy when the occurrence of the method analyte at a concentration greater than the MRL is infrequent.

3.11 LABORATORY REAGENT BLANK (LRB) – An aliquot of reagent water or other blank matrix that is treated exactly as a sample in cluding exposure to all glassware, equipment, solvents, reagents, sample preservatives , ISs, and SURs that are used in the

extraction batch. The LRB is used to determine if the method analyte or other interferences are present in the laboratory environ ment, the reagents, or the apparatus.

3.12 LOWEST CONCENTRATION MINIMUM REPORTING LEVEL ( LCMRL) – The single-laboratory LCMRL is the lowest true concentr ation for which the future recovery is predicted to fall, with high confidence (99%), between 50 and 150%

recovery. 1

3.13 MATERIAL SAFETY DATA SHEET (MSDS) – Written in formation provided by vendors concerning a chemical’s toxicity, health ha zards, physical properties, fire, and reactivity data including storage, spill, and handl ing precautions.

3.14 MINIMUM REPORTING LEVEL (MRL) – The minimum co ncentration that can be reported by a laboratory as a quantitated value for a target analyte in a sample following analysis. This defined concentration mus t meet the criteria defined in Section 9.2.4 and must not be any lower than the co ncentration of the lowest calibration standard for that analyte. A laborator y may be required to demonstrate a specific MRL by a regulatory body if this method is being performed for compliance

purposes.

3.15 QUALITY CONTROL SAMPLE (QCS) – A sample or sta ndard prepared using a Stock Standard Solution (SSS) of the method analyte that is obtained from a source external to the laboratory and different from the s ource of calibration standards. The second source SSS is used to fortify the QCS at a k nown concentration. The QCS is used to check calibration standard integrity.

3.16 SELECTED ION MONITORING (SIM) – A GC/MS techni que where only one or a few ions are monitored. When used with gas chromat ography, the set of ions monitored is usually changed periodically throughou t the chromatographic run, to correlate with the characteristic ions of the analy te, SUR and IS as they elute from the chromatographic column.

3.17 STOCK STANDARD SOLUTION (SSS) – A concentrated solution containing the method analyte prepared in the laboratory using ass ayed reference materials or purchased from a reputable commercial source.522-6

3.18 SURROGATE ANALYTE (SUR) – A pure analyte, whic h is extremely unlikely to be found in any sample, and which is added to a sample aliquot in a known amount before extraction or other processing, and is measu red with the same procedures used to measure other sample components. The purpose of the SUR is to monitor method performance with each sample.

4. INTERFERENCES

4.1 All glassware must be meticulously cleaned. Wa sh glassware with detergent and tap water, rinse with tap water, followed by reagent wa ter. Non-volumetric glassware

should be heated in a muffle furnace at 400 °C for 2 hours. Volumetric glassware should be solvent rinsed with DCM or purge and trap grade methanol after washing, and dried in a low temperature oven (<120 °C) or ai r dried.

4.2 Method interferences may be caused by contamina nts in solvents, reagents (including reagent water), sample bottles and caps, and other sample processing hardware that

lead to discrete artifacts and/or elevated baseline s in the chromatograms. All items such as these must be routinely demonstrated to be free from interferences (less than

1 / 3 the MRL for the method analyte) under the conditio ns of the analysis by analyzing

LRBs as described in Sections 9.2.1 and 9.3.1. Subtracting blank values from sample results is not permitted.

4.3 Purge and trap grade methanol must be used for all steps where methanol is used in this method. Other grades of methanol contain n umerous low molecular weight compounds that contain interfering ions whic h may prohibit accurate identification and quantitation of the analyte, SUR and IS.

4.4 Matrix interferences may be caused by contamina nts that are co-extracted from the sample. The extent of matrix interferences will va ry considerably from source to source, depending upon the nature of the water.

4.5 Preservatives (Sect. 8.1) are added to samples to ensure sample stability during shipping and storage prior to analysis. The potent ial exists for trace-level organic contaminants in these reagents. Interferences from these sources should be monitored by analysis of LRBs, particularly when new lots of reagents are acquired.

4.6 Solid phase extraction cartridges may be a sour ce of interferences. The analysis of field and laboratory reagent blanks can provide imp ortant information regarding the presence or absence of such interferences. Brands and lots of SPE devices should be tested to ensure that contamination does not preclu de analyte identification and quantitation.

4.7 Analyte carry-over may occur when a relatively “clean” sample is analyzed immediately after a sample containing relatively hi gh concentrations of compounds. Syringes and splitless injection port liners must b e cleaned carefully or replaced as needed. After analysis of a sample containing high concentrations of compounds, a522-7 LRB should be analyzed to ensure that accurate valu es are obtained for the next sample. During automated GC/MS analyses, extracts with positive results that were analyzed immediately following a sample with high c oncentrations of the analyte, should be reanalyzed after analyzing an acceptable LRB. If the analyte is not detected in extracts analyzed immediately after a high conce ntration extract, no reanalysis is

necessary.

4.8 Silicone compounds may be leached from punctured au tosampler vial septa, particularly when particles of the septa sit in the vial. This can occur after repeated injections from the same autosampler vial. If this method is performed in full scan mode, these silicone compounds may appear as regula rly spaced chromatographic peaks with similar fragmentation patterns. They ca n unnecessarily complicate the total ion chromatogram and may cause interferences at high levels.

4.9 High laboratory background levels of 1,4-dioxan e have been reported to be associated with air contamination. If 1,4-dioxane is detected in LRBs, room air should be considered as a possible source. 3,4

5. SAFETY

5.1 The toxicity or carcinogenicity of each reagent used in this method has not been precisely defined. Each chemical should be treated as a potential health hazard, and exposure to these chemicals should be minimized. 1 ,4-Dioxane is classified as a class B2 or probable human carcinogen. 5 Each laboratory is responsible for maintaining an awareness of OSHA regulations regarding safe handli ng of chemicals used in this

method. A reference file of MSDSs should be made a vailable to all personnel involved in the chemical analysis. Additional refe rences on laboratory safety are

available. 6-8

5.2 Pure standard materials and stock standard solu tions of these compounds should be handled with suitable protection to skin and eyes, and care should be taken not to breathe the vapors or ingest the materials.

5.3 Sodium bisulfate is used as a sample preservati ve to inhibit microbial growth and potential decay of 1,4-dioxane. Sodium bisulfate i s highly acidic and should be used with appropriate caution.

6. EQUIPMENT AND SUPPLIES (References to specific brands or catalog numbers are included for illustration only, and do not imply en dorsement of the product.)

6.1 SAMPLE CONTAINERS – Glass bottles fitted with p olytetrafluoroethylene (PTFE) lined screw caps. Although samples do not need to be collected headspace free, the size of the sample bottle should be selected based upon the sample volume to be

extracted.522-8

6.2 VIALS – Various sizes of glass vials with PTFE- lined screw caps for storing standard solutions and extracts, including glass 2-mL autosa mpler vials with PTFE-faced septa.

6.3 VOLUMETRIC FLASKS – Class A, various sizes, inc luding 1, 5, and 10 mL for preparation of standards. A 2-mL volumetric collec tion tube may also be used for the collection of the extract when SPE Option 2 is used (Sect. 11.5.3).

6.4 GRADUATED CYLINDERS – Glass, various sizes, inc luding 100 and 500 mL for measurement of sample volumes.

6.5 MICRO SYRINGES – Suggested sizes include 10, 25, 5 0, 100, 250, 500, and

1000 μ L.

6.6 CONICAL CENTRIFUGE TUBES – 15 mL, glass, with g raduations at 0.1 mL and PTFE-lined screw caps (KIMAX #45166 or equivalent), suitable for collection of the eluent from the 2-g solid phase cartridge after ext raction.

6.7 ANALYTICAL BALANCE – Capable of weighing to the nearest 0.0001 g.

6.8 SOLID PHASE EXTRACTION (SPE) APPARATUS

6.8.1 SPE CARTRIDGES – SPE carbon cartridges accept able for use in this method are made of either coconut charcoal or synthetic ca rbon as described in Sections 6.8.1.1 and 6.8.1.2 below. Graphitized carbon does not retain 1,4-dioxane and may not be used in this method.

6.8.1.1 Option 1 (for use with sample volumes of ≤ 500 mL) – 6-mL polypropylene tubes packed with 2 g coconut charcoal (80-120 mesh , approximately

150 μ m). At the time of method development, pre-packed cartridges were obtained from Restek Corporation (cat. # 26032) and United Chemical Technologies (UCT; cat. # EU52112M6). Equivalent b rands of coconut charcoal SPE cartridges with the specified particle size and whose performance meets all QC criteria in Section 9 may be used.

6.8.1.2 Option 2 (for use with samples volumes of ≤ 100 mL) – Waters AC-2 SepPak 400-mg activated carbon SPE cartridge (cat. # J JAN20229; 85 μ m particle size) or Supelco Supelclean ENVI-Carb Plus 400-mg synthetic carbon SPE cartridge (cat. # 54812-U).

6.8.2 VACUUM EXTRACTION MANIFOLD – Equipped with fl ow/vacuum control (Supelco cat. # 57250-U or equivalent).

6.8.3 SAMPLE DELIVERY SYSTEM – Use of a transfer tu be system (Supelco “Visiprep”, cat. # 57275 or equivalent), which tran sfers the sample directly from the sample container to the SPE cartridge, is recom mended. Sample reservoirs522-9 (Varian, cat. #12131012 or equivalent), which attac h to the cartridge, may be used, although they hold only a limited volume of s ample.

6.8.4 An automatic or robotic system designed for u se with SPE cartridges may be used if all QC requirements discussed in Section 9 are m et. Automated systems may use either vacuum or positive pressure to process s amples and solvents through the cartridge. All extraction and elution steps must be the same a s in the manual procedure. Extraction and/or elution steps may not be changed or omitted to accommodate the use of an automated syst em

.

6.9 LABORATORY OR ASPIRATOR VACUUM SYSTEM – Suffici ent capacity to maintain a vacuum of approximately 15 to 25 inches of mercury.

6.10 GAS CHROMATOGRAPH/MASS SPECTROMETER (GC/MS) SY STEM

6.10.1 FUSED SILICA CAPILLARY GC COLUMN – Data pres ented in this method were obtained with a column typically used for vola tiles analysis: Varian CP Select 624, 30 m x 0.25-mm i.d. with a 1.4 μ m film thickness, or equivalent. Other types of columns may be used. However, use o f shorter or thinner film

columns is not recommended because this will result in loss of resolution and very short retention times. Because the method ana lyte, SUR and IS have only very low mass ions in their spectra, and SIM is bei ng used, it is important to strive for chromatographic separation from any potential i nterferences. See Section 9.4 regarding the use of alternate GC columns.

CAUTION: If a GC column and/or temperature program differen t than that described in this method is used, the analyst must verify that the temperature program and subsequent column bake-out is sufficien t to remove all injected

material from the column. Although the retention times of the method analyt e, IS and SUR are short, many chemicals may be co-extr acted by carbon SPE and these need to be eluted from the GC column to preve nt them from appearing as interferences in subsequent analyses.

6.10.2 GC INJECTOR AND OVEN – The performance data in Section 17 were obtained using hot, splitless injection. Other injection te chniques such as temperature programmed injections, cold on-column injections an d large volume injections may be used if the QC criteria in Section 9 are met . Equipment designed appropriately for these alternate types of injectio ns must be used if these options

are selected.

6.10.3 GC/MS INTERFACE – The interface should allow the capillary column or transfer line exit to be placed within a few millim eters of the ion source. Other interfaces, such as jet separators, are acceptable as long as the system has adequate sensitivity and QC performance criteria in Section 9 are met.522-10

6.10.4 MASS SPECTROMETER (MS) – Any type of mass sp ectrometer may be used (i.e., quadrupole, ion trap, time of flight, etc.), although the SIM option may not provide enhanced sensitivity, or be an available op tion on all instruments. The spectrometer must produce a mass spectrum that meet s all criteria in Table 1 when a solution containing approximately one to two nanograms of bromofluorobenzene (BFB) is injected into the GC/MS. Th is test must be performed in the full scan mode. Use a single spectrum at the a pex of the BFB peak, an average spectrum of the three highest points of the peak, or an average spectrum across the entire peak to evaluate the performance of the system. Appropriate background subtraction is permitted. The scan time should be set so that there is a minimum of five scans across the chromatographic pe ak. Ten scans across chromatographic peaks are recommended.

6.10.5 DATA SYSTEM – An interfaced data system is r equired to acquire, store, and output MS data. The computer software should have the capability of processing stored GC/MS data by recognizing a GC peak within a given retention time window. The software must allow integration of the ion abundance of any specific ion between specified times or scan number limits. The software must be able to construct linear regressions and quadratic calibration curves, and calculate analyte concentrations.

6.11 N, N-DIETHYL-P-PHENYLENEDIAMINE (DPD) CHLORINE TEST KIT – Used to verify sample dechlorination when samples are re ceived at the analytical laboratory (Hach model CN-66; cat. # 2231-01 or equivalent).

7. REAGENTS AND STANDARDS

7.1 REAGENTS AND SOLVENTS – Reagent grade or better chemicals should be used in all steps. Unless otherwise indicated, it is inten ded that all reagents will conform to the specifications of the Committee on Analytical R eagents of the American Chemical Society (ACS), where such specifications are availa ble. Other grades may be used, provided it is first determined that the reagent is of sufficiently high purity to permit its use without lessening the quality of the determinat ion. During method development, only purge and trap grade methanol was found to be sufficiently free from low molecular weight interferences (as described in Sec t. 4.3). Therefore that grade must

be used.

7.1.1 HELIUM – 99.999 % or better, GC carrier gas.

7.1.2 REAGENT WATER – Purified water which does not contain any measurable quantities of the method analyte or interfering com pounds at or above 1 / 3 the MRL for 1,4-dioxane. In addition, there must be no interferences with the SUR

or IS.

7.1.3 METHANOL (CASRN 67-56-1) – Purge and trap grade only (see Section 4.3)

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7.1.4 DICHLOROMETHANE (DCM) (CASRN 75-09-02) – High purity, demonstrated to be free of analytes and interferences (B&J Brand GC 2 , Capillary GC or GC/MS Grade or equivalent).

7.1.5 SODIUM SULFATE, ANHYDROUS (CASRN 7757-82-6) – Soxhlet extracted

with DCM for a minimum of four hours or heated to 4 00 °C for two hours in a muffle furnace. An “ACS grade, suitable for pestic ide residue analysis”, or equivalent, of anhydrous sodium sulfate is recommen ded.

7.1.6 SAMPLE PRESERVATION REAGENTS

7.1.6.1 SODIUM SULFITE (CASRN 7757-83-7) – Reduces free and combined chlorine in samples that have been disinfected with chlorine and/or

chloramine.

7.1.6.2 SODIUM BISULFATE (CASRN 7681-38-1) – Anhydr ous, technical grade. It is added to acidify the samples to pH < 4 to act as a microbial inhibitor during sample shipping and storage.

7.2 STANDARD SOLUTIONS – When a compound purity is assayed to be 96% or greater, the weight can be used without correction to calculate the concentration of the

stock standard. Solution concentrations listed in this section were used to develop this method and are included as examples. Alternate con centrations may be used as necessary depending on instrument sensitivity and t he calibration range used. Standards for sample fortification generally should be prepared in the smallest volume that can be accurately measured to minimize the add ition of excess organic solvent to aqueous samples. During method development, standa rd solutions were stored in a

freezer at about -15 to -20 °C for several months. Experience indicates that the most likely cause of standard deterioration for this met hod is solvent evaporation. Therefore, it is recommended that standard solution s be stored at 0 °C or less, with minimal headspace. Laboratories should use standar d QC practices to determine when standards need to be replaced. Standard QC practic es, such as monitoring area counts and recovery percentages of CCCs, would help to det ermine if a standard requires replacement. As mentioned above, the major form of “standard deterioration” is solvent evaporation, which would result in a contin uous increase in area counts, and in some cases, target and SUR recoveries. During meth od development, SSSs and dilutions of SSSs of 1,4-dioxane, THF- d 8 , 1,4-dioxane- d 8 , and BFB were valid for at least 6 months after opening/preparation. Expirati on dates provided by the vendor should be used as an indicator of SSS shelf life pr ior to opening.

NOTE: Only purge and trap grade methanol may be use d in the preparation of standards and sample fortification solutions.

7.2.1 STOCK STANDARD SOLUTIONS (SSS) – Stock standa rd solutions of the method analyte, SUR and IS are commercially availab le from multiple

commercial sources. It is recommended that these s olutions be purchased from522-12 commercial sources. However, they may be prepared from neat materials. Utilizing stock standards prepared in methanol allo ws the same stock standard to be used to prepare both calibration standards and s ample fortification solutions.

The concentrations of the stock standard solutions used during method development were 1000-2000 μ g/mL.

7.2.1.1 PREPARATION OF STOCK STANDARD SOLUTIONS (SS S) FROM

NEAT MATERIALS

7.2.1.1.1 Place about 9.8 mL of methanol in a 10-mL volumetric flask. Allow

the flask to stand, unstoppered, for about 10 min o r until all alcohol wetted surfaces have dried. Weigh to the nearest 0 .1 mg.

7.2.1.1.2 Using a 100 μ L-syringe, quickly add two or more drops of the nea t

standard material to the flask. Be sure that the s tandard falls directly into the alcohol, without contacting the neck of th e flask.

7.2.1.1.3 Quickly reweigh, dilute to volume and mix by inverting the flask

several times. Calculate the concentration in μ g/ μ L from the net gain in weight.

7.2.1.1.4 Store SSS in 12-15 mL glass vials with PT FE lined screw caps.

7.2.2 CALIBRATION STANDARD SOLUTIONS (CAL) – Prepar e a series of calibration standards to encompass the desired cali bration range. Calibration standards must contain varying amounts of 1,4-dioxa ne, and a fixed amount of both the SUR and the IS, and be prepared in DCM. T he number of standards required is determined by the calibration range. T hree standards are required for one order of magnitude, six standards for two order s of magnitude and nine standards for three orders of magnitude. The calib ration curve associated with the

demonstration data in Section 17 contained nine sta ndards with concentrations of 1,4-dioxane ranging from 0.002 μ g/mL to 1.0 μ g/mL. (This corresponds to a concentration range of 0.04-20 μ g/L in the drinking water samples.) The concentrations of both 1,4-dioxane- d 8 (SUR) and the THF- d 8 (IS) were

0.500 μ g/mL in each standard.

7.2.3 SAMPLE FORTIFICATION SOLUTIONS

7.2.3.1 ANALYTE FORTIFICATON SOLUTION – Prepare one or more solutions in methanol for use in preparing LFBs and LFSMs (Se ct. 11.3.5). The number of solutions needed depends upon the calibra tion range and/or sample volume. During method development, two solu tions at

concentrations of 20 μ g/mL and 200 μ g/mL were used to fortify 100-mL and 500-mL samples, respectively.522-13 7.2.3.2 SURROGATE ANALYTE (SUR) FORTIFICATION SOLUT ION – Prepare one or more solutions of 1,4-dioxane- d 8 in methanol to be used for fortification of the SUR into samples, LFBs, LRBs a nd LFSMs (Sect.11.3.4). The concentrations used during meth od development were

200 μ g/mL and 2000 μ g/mL (STOCK) to fortify 100-mL and 500-mL samples, respectively.

7.2.3.3 INTERNAL STANDARD (IS) FORTIFICATION SOLUTI ON – Prepare

one or more solutions of THF- d 8 in DCM to be used to add the IS to all extracts (Sect. 11.4.4 and 11.5.4). During method development, the

concentrations of these solutions were 100 μ g/mL and 1000 μ g/mL (STOCK), used to fortify 2-mL and 10-mL extracts, r espectively.

7.2.4 GC/MS TUNE CHECK SOLUTION – Stock standard so lutions of BFB (CASRN 460-00-4) are available commercially. Prepare a BF B solution at a concentration

of 1-2 μ g/mL in DCM by dilution of the stock standard. Sto re this solution in an amber glass screw cap vial at 0 °C or less. To pre pare a SSS of BFB from neat material, see Section 7.2.1.1.

8. SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1 SAMPLE PRESERVATIVES – Preservation reagents, l isted in the table below, are added to each sample at the time of sample collecti on. Sodium sulfite must be added first and may be placed as a dry material in the sa mple bottles prior to shipment to the field. Aqueous solutions of sodium sulfite may not be added to sample bottles prior to shipment to the collection site because these solut ions are unstable and cannot be relied upon to completely dechlorinate the samples. Sodium bisulfate is added only

after the sodium sulfite has been dissolved in the aqueous sample. See Section 8.2.2 and 8.2.3 for complete instructions.

Compound Amount Purpose

Sodium sulfite 50 mg/L Reduce chlorine/chloramine r esidual

Sodium bisulfate 1 g/L (approx) Microbial inhibitor

8.2 SAMPLE COLLECTION

8.2.1 Open the tap and allow the system to flush un til the water temperature has stabilized (approximately three to five min). Coll ect samples from the flowing

system.

8.2.2 Fill sample bottles, taking care not to flush out the sample dechlorination reagent. Samples do not need to be collected headspace free.

8.2.3 After collecting the sample, cap the bottle a nd agitate by hand until the sodium sulfite is dissolved. Add enough sodium bisulfate such that the final522-14 concentration will be 1 g/L. Cap the bottle and mi x until dissolved. Unless field verification of pH is to be performed, keep the sam ple sealed until just prior to

extraction.

8.2.4 Field verification of pH 4 (optional). It i s anticipated that 1 g/L of sodium bisulfate will be sufficient to acidify most sample s to < pH 4. If there is reason to suspect that more may be needed, the pH can be veri fied with narrow range pH paper at the time of sample collection. After acid ification and mixing, pour a small amount of sample over a strip of the pH paper (do not dip the strip in the sample). Read the result as instructed on the pH p aper package. If the pH is ≥ 4, add additional sodium bisulfate until pH < 4 is obt ained. Seal the bottle, and keep the sample sealed until extraction.

8.3 SAMPLE SHIPMENT AND STORAGE – Samples must be c hilled during shipment and must not exceed 10 °C during the first 48 hours after collection. Sample temperature must be confirmed to be at or below 10 °C when they are received at the laboratory. Depending upon the water temperature a t the time of collection, samples may need to be refrigerated to reduce their tempera ture before being packed on ice for shipment. Samples stored in the lab must be held a t or below 6 °C until extraction, but should not be frozen. Freezing samples may comprom ise the sealed cap or result in sample bottle breakage.

8.3.1 Verification of sample dechlorination – Up on the receipt of samples at the laboratory, verify that Field Samples were dechlori nated at the time of collection.

The absence of total chlorine can be verified with a DPD chlorine test kit (Sect. 6.11).

8.4 SAMPLE AND EXTRACT HOLDING TIMES – Aqueous samp les may be stored as described above for up to 28 days from collection. Sample extracts, as prepared in Section 11, may be stored at -5 °C and protected fr om light for an additional 28 days.

9. QUALITY CONTROL

9.1 QC requirements include the Initial Demonstration o f Capability (IDC) and ongoing QC requirements that must be met when preparing and analyzing Field Samples. This section describes each QC parameter, its required f requency, and the performance criteria that must be met in order to meet USEPA qu ality objectives. The QC criteria discussed in the following sections are summarized in Section 17, Tables 6 and 7. These QC requirements are considered the minimum ac ceptable QC criteria. Laboratories are encouraged to institute additional QC practices to meet their specific

needs. If method modifications are under considera tion by the laboratory, refer to Sect. 9.4 for detailed requirements.

9.2 INITIAL DEMONSTRATION OF CAPABILITY (IDC) – The IDC must be successfully performed prior to analyzing any Field Samples. Prior to conducting the522-15 IDC, the analyst must first generate an acceptable Initial Calibration following the procedure outlined in Section 10.2.

9.2.1 INITIAL DEMONSTRATION OF LOW BACKGROUND – Be fore any samples are analyzed, or any time a new lot or brand of SPE materials or solvents are received from a supplier, it must be demonstrated t hat a LRB is reasonably free of any contamination that would prevent the identifica tion or quantitation of 1,4-dioxane, the IS or SUR.

9.2.1.1 A source of potential contamination is the SPE materials which may contain phthalate esters, silicon compounds, and other cont aminants that could

interfere with the determination of the method anal yte, SUR or IS. Although extraction media are generally made of ine rt materials, they may still contain extractable organic material. If the background contamination is sufficient to prevent accurate and precise measu rements, the condition must be corrected before proceeding with the IDP (S ect. 9.2.2).

9.2.1.2 Other sources of background contamination a re solvents, reagents (including reagent water), room air and glassware. Background contamination must be reduced to an acceptable level before proceeding wi th the IDP (Sect. 9.2.2). Background from 1,4-dioxane and interferences must be ≤ 1/3 the MRL. If background contamination is an on-going or intermit tent issue, the analyst must not attempt to verify an MRL less than the mea n LRB concentration

+ 3 σ , or three times the mean LRB concentration, whiche ver is greater.

NOTE: Although quantitative data below the MRL may not b e reliably accurate enough for data reporting, such data are u seful in determining an MRL cut off for the method analyte if it is found i n the LRB. Therefore, blank contamination levels may be estimated by extr apolation, when the

concentration is below the lowest calibration stand ard. This also applies to estimating LRB concentrations for daily low backgro und verification.

9.2.2 INITIAL DEMONSTRATION OF PRECISION (IDP) – Pr epare, extract, and analyze four to seven replicate LFBs fortified near the midrange of the initial calibration curve according to the procedure descri bed in Section 11. Sample preservatives as described in Section 8.1 must be a dded to these samples. The relative standard deviation (RSD) of the results of the replicate analyses must be

less than 20%.

9.2.3 INITIAL DEMONSTRATION OF ACCURACY (IDA) – Usi ng the same set of replicate data generated for Section 9.2.2, calcula te average recovery. The average recovery of the replicate values must be wi thin ± 20% of the true value.

9.2.4 MINIMUM REPORTING LEVEL (MRL) CONFIRMATION – Establ ish a target concentration for the MRL for 1,4-dioxane based on the intended use of the method. In some cases, the MRL may be dictated by USEPA or another522-16 regulatory body. Establish an Initial Calibration following the procedure outlined

in Section 10.2. The lowest calibration standard u sed to establish the Initial Calibration (as well as the low-level CCC) must be at or below the concentration of the MRL. Establishing the MRL concentration too low may cause repeated failure of ongoing QC requirements. Validate the M RL following the procedure

outlined below.

9.2.4.1 Fortify, extract, and analyze seven replicate LFBs at the proposed MRL

concentration. These LFBs must contain all method preservatives described in Section 8.1. Calculate the mean ( Mean ) and standard deviation for these replicates. Determine the Half Range for the predi ction interval of results ( HR PIR ) using the equation below

HR S PIR = 3963

.

where S is the standard deviation, and 3.963 is the consta nt value for seven replicates. 1

NOTE: The mass spectrum (either SIM or full scan) for the method analyte in the LFBs must meet all the analyte identificatio n criteria in Sections 12.1 and 12.2, i.e., the MRL verification may not be per formed on LFBs where only the base peak is observed. If during MRL conf irmation all identification ions are not observed, the MRL selec ted is too low.

9.2.4.2 Confirm that the upper and lower limits for the Prediction Interval of Result ( PIR = Mean + HR PIR ) meet the upper and lower recovery limits as shown

below.

The Upper PIR Limit must be ≤ 150% recovery.

50% 1 % 100 ≤ × +

on oncentrati FortifiedC HR Mean PIR

The Lower PIR Limit must be ≥ 50% recovery.

0% 5 % 100 ≥ × −

on oncentrati FortifiedC HR Mean PIR

9.2.4.3 The MRL is validated if both the Upper and Lower PIR Limits meet the criteria described above (Sects. 9.2.4.2). If thes e criteria are not met, the MRL for 1,4-dioxane has been set too low and must b e re-evaluated at a higher concentration.

9.2.5 CALIBRATION CONFIRMATION – Analyze a QCS as describ ed in Section 9.3.9 to confirm the accuracy of the standards and calibration curve.522-17

9.2.6 DETECTION LIMIT (DL) DETERMINATION (optional)

– While DL determination is not a specific requirement of this method, it may be required by various regulatory bodies associated with complianc e monitoring. It is the responsibility of the laboratory to determine if DL determination is required based upon the intended use of the data.

Replicate analyses for this procedure should be don e over at least three days (i.e., both the sample extraction and the GC analyses shou ld be done over at least three days). Prepare at least seven replicate LFBs conta ining 1,4-dioxane at a

concentration estimated to be near the DL. This co ncentration may be estimated by selecting a concentration at two to five times t he noise level. The appropriate fortification concentrations will be dependent upon the sensitivity of the GC/MS system used. All preservation reagents listed in S ection 8.1 must also be added to these samples. Analyze the seven replicates throug h all steps of Section 11.

NOTE: If an MRL confirmation data set meets these requir ements, a DL may be calculated from the MRL confirmation data, and no a dditional analyses are

necessary.

Calculate the DL using the equation

) 99.0 1 ,1 ( =

− − × = α n t s DL

where:

s = standard deviation of replicate analyses

t ( n -1, 1- α =0.99) = Student's t value for the 99% confidence level w ith n -1 degrees of freedom

n = number of replicates.

NOTE: There are no precision and accuracy requirements f or the DL replicates. Do not subtract blank values when performing DL cal culations.

9.3 ONGOING QC REQUIREMENTS – This section summariz es the ongoing QC criteria that must be followed when processing and analyzing Field Samples.

9.3.1 LABORATORY REAGENT BLANK (LRB) – An LRB is re quired with each extraction batch to confirm that potential backgrou nd contaminants are not interfering with the identification or quantitation of the method analyte, SUR or IS. If the LRB produces a peak within the retentio n time window of any analyte that would prevent the identification or quantitati on of that analyte, determine the

source of contamination and eliminate the interfere nce before processing samples. Background contamination must be reduced to an acce ptable level before proceeding.522-18 NOTE: Absence of interferences must be verified for 1,4 -dioxane at both the quantitation ion (QI) ( m/z 88) and the confirmation ion ( m/z 58). Background

from contaminants that interfere with the measureme nt of 1,4-dioxane must be

below 1 / 3 of the MRL. Blank contamination may be estimated by extrapolation, if

the concentration is below the lowest calibration s tandard. This procedure is not allowed for sample results as it may not meet data quality objectives. If the method analyte is detected in the LRB at concentrat ions equal to or greater than this level, then all data for the analyte must be c onsidered invalid for all samples

in the extraction batch.

9.3.2 CONTINUING CALIBRATION CHECK (CCC) – CCC Stan dards are analyzed at the beginning of each analysis batch, after ever y ten Field Samples, and at the end of the analysis batch. See Section 10.3 for co ncentration requirements and acceptance criteria.

9.3.3 LABORATORY FORTIFIED BLANK (LFB) – An LFB is required with each

extraction batch. The fortified concentration of t he LFB must be rotated between low, medium, and high concentrations from batch to batch. The low concentration LFB must be as near as practical to, but no more than two times the MRL. Similarly, the high concentration LFB should be near the high end of the calibration range established during the initial ca libration (Sect. 10.2). Results of the low-level LFB analyses must be 50-150% of the t rue value. Results of the medium and high-level LFB analyses must be 70-130% of the true value. If the LFB results do not meet these criteria for 1,4-diox ane, then all data must be considered invalid for all samples in the extractio n batch.

9.3.4 MS TUNE CHECK – A complete description of the MS Tune Check is found in Section 10.2.1. Acceptance criteria for the MS Tun e Check are summarized in Section 17, Table 1. The MS Tune Check must be per formed each time a major change is made to the mass spectrometer, and prior to establishing and/or reestablishing an initial calibration (Sect.10.2). I n this method, daily BFB analysis is not required.

9.3.5 INTERNAL STANDARDS (IS) – The analyst must mo nitor the peak area of the IS in all injections during each analysis day. The IS response (peak area) in any chromatographic run must not deviate from the respo nse in the most recent CCC by more than 30%, and must not deviate by more than 50% from the mean ar ea measured during initial analyte calibration. If th e IS area in a chromatographic run does not meet these criteria, inject a second a liquot of that extract.

9.3.5.1 If the reinjected aliquot produces an accep table IS response, report results for that aliquot.

9.3.5.2 If the reinjected extract fails again, the analyst should check the calibration by reanalyzing the most recently acceptable calibra tion standard. If the

calibration standard fails the criteria of Section 10.3, recalibration is in order522-19 per Section 10.2. If the calibration standard is a cceptable, extraction of the sample may need to be repeated provided the sample is still within the holding time. Otherwise, report results obtained f rom the reinjected extract, but annotate as “suspect/IS recovery.” Alternative ly, collect a new sample and re-analyze.

9.3.6 SURROGATE (SUR) RECOVERY – The SUR standard is fort ified into the aqueous portion of all samples, LRBs, LFBs, CCCs, L FSMs and LFSMDs prior

to extraction. It is also added to the calibration standards. The SUR is a means of assessing method performance from extraction to fin al chromatographic measurement. Calculate the percent recovery (%R) f or the SUR using the equation

100 % ×

     

= B A R

where:

A = calculated SUR concentration for the QC or Field Sample

B = fortified concentration of the SUR.

9.3.6.1 SUR recovery must be in the range of 70-130 % of the true value. When SUR recovery is less than 70% or greater than 130%, check the 1) calculations to locate possible errors, 2) standard solutions for degradation, 3) contamination, and 4) instrument performance. C orrect the problem and reanalyze the extract.

9.3.6.2 If the extract reanalysis meets the SUR rec overy criterion, report only data for the reanalyzed extract.

9.3.6.3 If the extract reanalysis fails the 70-130% recovery criterion, the analyst should check the calibration by injecting the last CCC that passed. If the CCC fails the criteria of Section 9.3.6.1, recalibr ation is in order per Section 10.2. If the calibration standard is acceptable, e xtraction of the sample should be repeated provided the sample is still wit hin the holding time. If the re-extracted sample also fails the recovery cri terion, report all data for that sample as “suspect/SUR recovery” to inform the data user that the results are suspect due to SUR recovery. Alternati vely, collect a new sample and re-analyze.

9.3.7 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – Analysis of an LFSM is required in each extraction batch and is us ed to determine that the sample matrix does not adversely affect method accu racy. If the occurrence of 1,4-dioxane in the samples is infrequent, or if his torical trends are unavailable, a LFSMD must be prepared, extracted, and analyzed fro m a duplicate Field Sample to assess method precision (Sect. 9.3.8). Extracti on batches that contain LFSMDs do not require the analysis of a Field Duplicate. If a variety of different sample522-20 matrices are analyzed regularly, for example, drink ing water from groundwater and surface water sources, method performance shoul d be established for each. Over time, LFSM data should be documented by the la boratory for all routine sample sources analyzed.

9.3.7.1 Within each extraction batch, a minimum of one Field Sample is fortified as an LFSM for every 20 samples extracted. The LFSM i s prepared by spiking a sample with an appropriate amount of the Analyte Fortification Solution (Sect. 7.2.3.1). Select a spiking concentration th at is greater than or equal to the matrix background concentration, if known. Use historical data and rotate through low, medium and high concentrations when selecting a fortifying concentration.

9.3.7.2 Calculate the percent recovery (% R ) for the analyte using the equation



## ( ) 100 % × −

= C B A R

where:

A = measured concentration in the fortified sample

B = measured concentration in the unfortified sample

C = fortification concentration.

NOTE: Field Samples that have native analyte concentrat ions above the DL but below the MRL, and are fortified at concentr ations at or near the MRL, should be corrected for the native levels in o rder to obtain meaningful %R values. This example and the LRB (Sec t. 9.3.1) are the only permitted use of analyte results below the MRL.

9.3.7.3 Analyte recoveries may exhibit matrix bias. For samples fortified at or above their native concentration, recoveries should range between 70-130%, except for low-level fortification near or at the M RL (within a factor of two times the MRL concentration) where 50-150% recoveri es are acceptable. If the accuracy of any analyte falls outside the desig nated range, and the laboratory performance for that analyte is shown to be in control in the CCCs, the recovery is judged to be matrix biased. The result for that analyte in the unfortified sample is labeled “suspect/matri x” to inform the data user that the results are suspect due to matrix effects.

9.3.8 FIELD DUPLICATE (FD) OR LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE (LFSMD) – Within each extraction b atch, a minimum of one Field Duplicate (FD) or Laboratory Fortified Sa mple Matrix Duplicate (LFSMD) must be analyzed. Duplicates check the pre cision associated with sample collection, preservation, storage, and labor atory procedures. If method analytes are not routinely observed in Field Sample s, an LFSMD should be analyzed rather than an FD.522-21 9.3.8.1 Calculate the relative percent difference ( RPD ) for duplicate FD measurements ( FD1 and FD2 ) using the equation



## ( ) 100

2/ 2 1 2 1

×
+ −

= FD FD FD FD RPD

9.3.8.2 RPDs for FDs should be ≤ 30%. Greater variability may be observed when FDs have analyte concentrations that are within a f actor of two of the MRL. At these concentrations, FDs should have RPDs that are ≤ 50%. If the RPD of the analyte falls outside the designated range, and the laboratory performance for the analyte is shown to be in contr ol in the CCC, the recovery is judged to be matrix biased. The result for that analyte in the unfortified sample is labeled “suspect/matrix” to i nform the data user that the results are suspect due to matrix effects. Fai lure to meet the FD criteria is a reflection of the performance of the method fo r that individual sample, and does not constitute analysis or extraction batc h failure.

9.3.8.3 If an LFSMD is analyzed instead of a FD, ca lculate the relative percent difference (RPD) for duplicate LFSMs (LFSM and LFSM D) using the equation



## ( ) 100 2/ ×
+ −

= LFSMD LFSM LFSMD LFSM RPD

9.3.8.4 RPDs for duplicate LFSMs should be ≤ 30% for samples fortified at or

above their native concentration. Greater variabil ity may be observed when LFSMs are fortified at analyte concentrations that are within a factor of two

of the MRL. LFSMs fortified at these concentration s should have RPDs

that are ≤ 50% for samples fortified at or above their native concentration. If the RPD of the analyte falls outside the designa ted range, and the laboratory performance for the analyte is shown to be in control in the CCC, the recovery is judged to be matrix biased. The re sult for that analyte in the unfortified sample is labeled “suspect/matrix” to i nform the data user that the results are suspect due to matrix effects. Fai lure to meet the LFSM/LFSMD criteria is a reflection of the performa nce of the method for that individual sample, and does not constitute ana lysis or extraction batch

failure.

9.3.9 QUALITY CONTROL SAMPLES (QCS) – As part of th e IDC (Sect. 9.2), each time new calibration standards are prepared, and at least quarterly, analyze a QCS sample from a source different from the source of t he calibration standards. The QCS should be prepared and analyzed just like a CCC (Sect. 10.3). The calculated amount for the analyte in the QCS must b e ± 20% of the expected value. If measured analyte concentrations are not of acceptable accuracy, check522-22 the entire analytical procedure to locate and corre ct the problem, or obtain another QCS.

9.4 METHOD MODIFICATION QC REQUIREMENTS – The analyst i s permitted to modify the GC injection technique, GC column and co nditions, and MS conditions.

9.4.1 Each time method modifications are made, the analys t must repeat the procedures of the IDC (Sect. 9.2) and verify that all QC crite ria can be met in ongoing QC samples (Sect. 9.3).

9.4.2 The analyst is also required to evaluate and docume nt method performance for the proposed method modifications in real matrices that span the range of waters that the laboratory analyzes. This additional step is r equired because modifications that perform acceptably in the IDC, which is conduc ted in reagent water, can fail ongoing method QC requirements in real matrices. T his is particularly important for methods subject to matrix effects. If, for exa mple, the laboratory analyzes finished waters from both surface and groundwater m unicipalities, this requirement can be accomplished by assessing precis ion and accuracy (Sects. 9.2.2 and 9.2.3) in a surface water with moderate t o high Total Organic Carbon (TOC) (e.g., 2 mg/L or greater) and a hard groundwa ter (e.g., 250 mg/L or greater as calcium carbonate).

9.4.3 The results of Sections 9.4.1 and 9.4.2 must be app ropriately documented by the analyst and should be independently assessed by the laboratory’s Quality Assurance (QA) officer prior to analyzing Field Sam ples.

9.4.3.1 When implementing method modifications, it is the r esponsibility of the laboratory to closely review the results of ongoing QC, and in particular, the results associated with the LFBs (Sect. 9.3.3), LFS Ms (Sect. 9.3.7), FDs or LFSMDs (Sect. 9.3.8), CCCs (Sect. 9.3.2), and the I S area counts (Sect. 9.3.5). If repeated failures are noted, the modifi cation must be abandoned.

10. CALIBRATION AND STANDARDIZATION

10.1 Demonstration and documentation of acceptable mass spectrometer (MS) tune and initial calibration is required before any samples are analyzed. After the initial calibration is successful, a CCC is required at the beginning and end of each period in which analyses are performed, and after every tenth Field Sample. Verification of mass spectrometer tune must be repeated each time a major instrument modification is made or maintenance is performed, and prior to esta blishing or re-establishing an

initial calibration.

10.2 INITIAL CALIBRATION

10.2.1 MS TUNE/MS TUNE CHECK – Operate the MS in th e electron ionization (EI)

mode. Calibrate the mass and abundance scales of t he MS with calibration522-23 compounds and procedures prescribed by the manufact urer with any modifications necessary to meet tuning requirements . Inject 2 ng or less of the BFB solution (Sect. 7.2.4) into the GC/MS system. Acquire a mass spectrum that

includes data for m/z 45 to 180. The GC and MS parameters must be set s uch that a minimum of five scans (10 scans are recommended) are obtained during the elution of the BFB chromatographic peak Use a sin gle spectrum of the BFB peak, an average spectrum of the three highest poin ts of the peak, or an average spectrum across the entire peak to evaluate the per formance of the system. Appropriate background subtraction is permitted. I f the BFB mass spectrum does not meet all criteria in Table 1, the MS must be re -tuned and adjusted to meet all criteria before proceeding with the initial calibra tion.

10.2.2 ANALYTE CALIBRATION – Operating conditions u sed during method development are described below. Data were obtaine d using SIM on a quadrupole MS system using the GC column described in Section 6.10.1. Conditions different from those described may be us ed if QC criteria in Section 9

are met. Different conditions include alternate GC columns, temperature programs, MS conditions, and injection techniques a nd volume, such as cold oncolumn and direct injection port liners and/or larg e volume injection techniques. Equipment specifically designed for alternate types of injections must be used if these options are selected. Full scan MS data may be used if the sensitivity

achieved meets the data user’s needs.

10.2.2.1 GAS CHROMATOGRAPH (GC) CONDITIONS – Inject a 1-μL aliquot of each CAL prepared as in Section 7.2.2 into a hot, s plitless injection port

held at 200 E C with a split delay of 0.5 min. Temperature progra m the GC as follows: initial oven temperature of 30 E C, hold for 1.0 min, ramp at

7 E C/min to 90 E C, ramp at 20 E C/min to a final temperature of 200 E C and hold for 3.0 min, for a total run time of 18.07 min . Begin data acquisition at 6.0 min. During method development, the GC was ope rated in a constant flow rate mode at a rate of 1.0 mL per min. The MS ion source and the GC injector were both maintained at 200 E C.

NOTE: Using these conditions, all compounds of interest eluted before 9 min. However, it is important to complete the GC temperature program to
ensure that co-extracted materials have eluted from the GC column prior to initiating the next analysis.

10.2.2.2 MASS SPECTROMETER (MS) CONDITIONS – Any ty pe of MS may be

used as detailed in Sect. 6.10.4. Data shown in Se ction 17 (Tables 2-5) were obtained in the SIM mode. Operation of the MS in t his mode enhances sensitivity. However, less mass spectral data are obtained for all peaks including the method analyte, SUR, IS and any poten tial interferences. Because of this, and because the selected ions for the compounds of interest are very low masses that are likely to occur more f requently in interferences than most higher mass ions, the analyst should also rely on chromatography522-24 to reduce the possibility of false positives. It i s highly recommended that a GC column at least 30 m in length with a film thick ness of at least 1.4 μ m be used to provide adequate separation of the compo unds of interest from possible interferences. During method development, the MS was scanned in

SIM mode for m/z 46, 78, and 80 (IS) at a rate of 0.36 s/scan in Se gment 1 (6 to 8 min). Segment 2 (8 to 18 min) was set to s can for m/z 58 and 88 (TARGET), as well as 62, 64, and 96 (SUR) at 0.60 s /scan, resulting in at least nine scans across each chromatographic peak. A minimum of five scans during the elution of each GC peak are requir ed. Ten scans across each GC peak are recommended. This requirement is applicable to both full scan and SIM analysis. Timing of the SIM segments must be set such that no chromatographic peak of interest begins or ends within 5 s of the beginning or end of the segment. An example chroma togram obtained during method development using the instrumental co nditions described in this section is shown in Figure 1.

10.2.3 CALIBRATION CURVE – Use the GC/MS software t o create a calibration curve for 1,4-dioxane using the IS technique. Concentrat ions may be calculated through the use of a linear or quadratic calibration curve. A weighted curve is permitted at the discretion of the analyst. Because the SUR is added to all samples and standards at a single concentration, calibrate for the SUR using the average response factor.

10.2.4 CALIBRATION ACCEPTANCE CRITERIA – When quant itated using the calibration curve, each calibration point, except t he lowest point, should calculate

to be within 80-120% of its true value. The lowes t point should calculate to be

within 60-140% of its true value. If these criteri a cannot be met, the analyst will have difficulty meeting ongoing QC criteria. It is recommended that corrective action be taken to re-analyze the CALs, restrict th e range of calibration, or select

an alternate method of calibration.

10.3 CONTINUING CALIBRATION CHECK (CCC) – The CCC v erifies the initial calibration at the beginning and end of each group of analyses, and after every tenth sample during analyses. In this context, a “sample ” is considered to be a Field Sample. The LRBs, LFBs, LFSMs, LFSMDs, FDs and CCC s are not counted as samples. The beginning CCC for each analysis batch must be at or below the MRL in order to verify instrument sensitivity prior to any analyses. Subsequent CCCs must alternate between medium and high concentration CAL s.

10.3.1 Inject an aliquot of the appropriate concent ration CAL solution and analyze with the same conditions used during the initial calibra tion.

10.3.2 Determine that the absolute area of the QI o f the IS has not changed by more than ± 50% from the average area measured during initial calibration, or more than

± 30% from the most recent CCC. If the IS area has changed by more than this522-25 amount, remedial action must be taken (Sect. 10.3.4 ). Control charts are useful aids in documenting system sensitivity changes.

10.3.3 Calculate the concentration of 1,4-dioxane a nd the SUR in the check standard. The calculated amount for 1,4-dioxane for medium an d high level CCCs must be

± 30% of the true value. The calculated amount for the lowest calibration level for 1,4-dioxane, which must be at a concentration l ess than or equal to the MRL,

must be within ± 50% of the true value. If these c riteria are not met, then all data for the problem analyte must be considered invalid, and remedial action (Sect. 10.3.4) should be taken. This may require r ecalibration. Any Field Sample extracts that have been analyzed since the last acc eptable calibration verification should be re-analyzed after adequate calibration ha s been restored, with the following exception: if the CCC fails at the end of an analytical sequence because the calculated concentration of the target compound or SUR is greater than 130% (150% for the low-level CCC), and Field Sample extr acts show no detection for the target compound, non-detects may be reported wi thout re-analysis.

10.3.4 REMEDIAL ACTION – Failure to meet CCC QC per formance criteria may require remedial action. Major maintenance such as cleaning the ion source, cleaning the mass analyzer, replacing filament asse mblies, replacing the GC column, etc., require returning to the initial cali bration step (Sect. 10.2).

11. PROCEDURE

11.1 This procedure may be performed manually or in an automated mode (Sect. 6.8.4) using a robotic or automatic sample preparation dev ice. If an automatic system is used to prepare samples, follow the manufacturer's opera ting instructions, but all extraction and elution steps must be the same as in the manual procedure. Extraction and/or elution steps may not be changed or omitted to acco mmodate the use of an automated system.

11.2 Important aspects of this analytical procedure include proper preparation of laboratory glassware and sample containers (Sect. 4.1), as wel l as sample collection and storage (Sect. 8). This section details the procedures for sample preparation, SPE using 2-g coconut charcoal or 0.4-g carbon cartridges as desc ribed in Sect. 6.8.1, and extract analysis.

NOTE: The SPE cartridges and sodium sulfate drying mater ials described in this section are designed as single use items and must b e discarded after use. They may not be refurbished for re-use in subsequent analyse s.

NOTE: Only purge and trap grade methanol may be used in t his extraction (see Sect. 4.3).522-26

11.3 SAMPLE PREPARATION

11.3.1 All Field and QC samples (LRBs and LFBs) mus t contain the dechlorinating agent, sodium sulfite. Verify that Field Samples w ere checked for total chlorine upon sample receipt at the laboratory, and that no chlorine was present (Sect. 8.3.1). Add sodium sulfite to all LRBs and LFBs ac cording to the instructions in Section 8, prior to fortification with the SUR and analyte.

11.3.2 All Field and QC samples (LRBs and LFBs), m ust contain the anti-microbial

agent sodium bisulfate. Verify that Field Samples were acidified to < pH 4 at the time of collection by checking with narrow range pH paper (this verification may take place at sample receipt if preferred by the la boratory). Add sodium bisulfate to all LRBs and LFBs according to the instructions in Section 8, prior to fortification with the SUR and analyte.

11.3.3 If the sample bottles used contain a sample volume close to the sample volume to

be extracted (± 10%), mark the sample level on the outside of the sample container for subsequent measurement of the sample volume. After the sample has been extracted, determine the exact sample volu me by filling the bottle to the mark with water and transferring to an appropriatel y sized graduated cylinder. Measure to within ± 5 mL for 100 mL samples, and to within ± 25 mL for 500-mL samples. If a much larger sample has been c ollected than will be extracted, transfer either 100 mL or 500 mL of the sample to a clean glass container with a clean graduated cylinder. The sam ple volume will depend upon the SPE being used (Sects. 11.4, 11.5).

Alternatively, the sample volume may be calculate d by weighing the sample

bottle before and after extraction (or sample trans fer) and using a density of 1.0 g/mL.

11.3.4 ADDITION OF SURROGATE (SUR) ANALYTE – Add an aliquot of the Surrogate Analyte Fortification Solution (Sect. 7.2 .3.2) to all samples and mix by swirling the sample. Addition of 2.5 μ L of a 2000- μ g/mL solution to a 500-mL sample will result in a concentration of 10 μ g/L. Addition of 5 μ L of a

200- μ g/mL solution to a 100-mL sample will also result i n a concentration of

10 μ g/L.

11.3.5 FORTIFICATION WITH METHOD ANALYTE – If the s ample is an LFB, LFSM, or LFSMD, add the necessary amount of Analyte Fortification Solution (Sect. 7.2.3.1). Swirl each sample to ensure all c omponents are properly mixed.

Addition of 2.5 μ L of a 200- μ g/mL solution to a 500-mL sample will result in a

concentration of 1 μ g/L. Addition of 5 μ L of a 20- μ g/mL solution to a 100-mL sample will also result in a concentration of 1 μ g/L.

11.3.6 Proceed with sample extraction Option 1 (Sec t. 11.4) or Option 2 (Sect. 11.5).522-27

11.4 SPE PROCEDURE OPTION 1; EXTRACTION OF 500-ML S AMPLES – Proper conditioning of the solid phase sorbent can have a marked effect on method precision and accuracy. This section describes the SPE proce dure using 2-g coconut charcoal cartridges and the transfer tube system and SPE man ifold as described in Section 6.8.

11.4.1 CARTRIDGE CONDITIONING

11.4.1.1 Fill the cartridge with approximately 3 mL of DCM, turn on the vacuum, and pull the solvent through, aspirating completely

.

11.4.1.2 Fill the cartridge with approximately 3 mL of methanol, turn on the vacuum, and pull the solvent through, aspirating completely

.

11.4.1.3 Fill the cartridge with approximately 3 mL of methanol and elute with vacuum to just above the top frit - not allowing th e cartridge to go dry at the end. From this point forward, do not allow the car tridge to go dry.

11.4.1.4 Fill the cartridge with approximately 3 mL of reagent water, turn on the vacuum, and pull the water through, repeat five tim es, without allowing the cartridge to go dry in between washes or at the end

.

11.4.2 SAMPLE EXTRACTION – Attach a transfer tube f rom each sample bottle to each cartridge and then turn on the vacuum. Adjust the vacuum so that the approximate flow rate is 10 mL/min. After all the sample has passed through each SPE cartridge, detach the transfer tube and dr aw air through the cartridge for

10 min at full vacuum. Turn off and release the va cuum. Proceed immediately with cartridge elution.

11.4.3 CARTRIDGE ELUTION – Lift the extraction mani fold top and insert a rack with

collection tubes into the vacuum manifold tank to c ollect the extracts as they are eluted from the cartridges. Fill each cartridge wi th DCM. Pull enough of the solvent into the cartridge at low vacuum to soak th e sorbent. Turn off the vacuum and vent the system. Allow the sorbent to soak in DCM for approximately 1 min. Apply a low vacuum and pull the DCM through the car tridge in a dropwise

fashion into the collection tube. Continue to add DCM to the cartridge as it is being drawn through until the volume of extract is about 9 mL, determined by the markings on the side of the collection tube.

11.4.4 Remove collection tubes containing the extract from the vacuum manifold. Adjust the final volume as closely as possible to 1 0 mL with DCM. Small amounts of residual water from the sample container and the SPE cartridge may form a small immiscible layer with the extract. Re ad the volume on the collection tube at the level of the DCM layer. Add the IS. A ddition of 5 μ L of a

1000- μ g/mL IS solution to a 10-mL extract will result in an IS concentration of 500 ng/mL. Mix well. A vortex mixer is recommende d. To eliminate residual water, add approximately 2 g of anhydrous sodium su lfate. Mix well. Transfer522-28 aliquots of the extract to autosampler vials, or ot her glass vials, for storage until analysis.

NOTE: Experiments during method development indicated th at this extract cannot be reliably concentrated by nitrogen evapora tion because of the volatility of the method analyte. Therefore, extract concentr ation to enhance sensitivity is not permitted.

11.5 SPE PROCEDURE OPTION 2; EXTRACTION OF 100-ML S AMPLES – Proper conditioning of the solid phase sorbent can have a marked effect on method precision and accuracy. This section describes the SPE proce dure using Waters AC-2 Sep-Pak or Supelco Supelclean ENVI-Carb Plus cartridges wit h 60-mL reservoirs and the SPE

manifold as described in Sect. 6.8.

11.5.1 CARTRIDGE CONDITIONING

11.5.1.1 Fill the cartridge with approximately 1 mL of DCM, turn on the vacuum, and pull the solvent through, aspirating completely

.

11.5.1.2 Place a reservoir over each cartridge and fill the cartridge with approximately 2 mL of methanol, turn on the vacuum, and pull the solvent through, aspirating completely.

11.5.1.3 Fill the cartridge with approximately 2 mL of methanol and elute with vacuum to just above the top of the cartridge - not allowing the cartridge to go dry at the end. From this point forward, do not allow the cartridge to go dry.

11.5.1.4 Fill the cartridge with approximately 3 mL of reagent water, turn on the vacuum, and pull the water through, without allowin g the cartridge to go dry.

11.5.2 SAMPLE EXTRACTION – Fill each reservoir with sample. Adjust the vacuum so that the approximate flow rate is 10 mL/min. A 60-mL reservoir will require a second filling to complete sample loading. After al l the sample has passed through each SPE cartridge, detach the reservoir an d draw air through the cartridge for 10 min at full vacuum. Turn off and release the vacuum. Proceed immediately with cartridge elution.

11.5.3 CARTRIDGE ELUTION – Lift the extraction mani fold top and insert a rack with

2-mL volumetric collection tubes into the extractio n tank to collect the extracts as they are eluted from the cartridges. (It is not ne cessary to reverse the ENVI-Carb Plus cartridge as described in the manufacturer’s l iterature.) Fill each cartridge with DCM. Pull enough of the solvent into the cart ridge at low vacuum to soak the sorbent. Turn off the vacuum and vent the syst em. Allow the sorbent to soak in DCM for approximately 1 min. Apply a low vacuum and pull the DCM522-29 through the cartridge in a dropwise fashion into th e collection tube. Continue to add DCM to the cartridge as it is being drawn throu gh until the volume of extract is about 1.5 mL, estimated by the volumetric mark o n the side of the collection

tube.

11.5.4 Remove collection tubes containing the extra cts from the vacuum manifold. Adjust the final volume as closely as possible to 2 mL with DCM. Small amounts of residual water from the sample container and the SPE cartridge may form a small immiscible layer with the extract. Read the volume on the collection tube at the level of the DCM layer. Add the IS. Addition of 10 μ L of a 100- μ g/mL IS

solution to a 2-mL extract will result in an IS con centration of 500 ng/mL. Mix

well. A vortex mixer is recommended. To eliminate residual water, pass the 2-mL extracts through a small column containing a m inimum of 0.4 g of dry anhydrous sodium sulfate. A fritted 3-mL polypropy lene column or a 5-8 mm diameter disposable pipette with a small piece of g lass wool may be used. Collect the extracts from the drying column directly in 2-m L autosampler vials for storage until analysis.

NOTE: Experiments during method development indicated th at this extract cannot be reliably concentrated by nitrogen evapora tion because of the volatility of the method analyte. Therefore, extract concentr ation to enhance sensitivity is not permitted.

11.6 Analyze an aliquot of the sample extract prepa red using Option 1 or 2, with the GC/MS system under the same conditions used for the initial and continuing calibrations (Sect. 10).

12. DATA ANALYSIS AND CALCULATIONS

12.1 IDENTIFICATION OF ANALYTES – At the conclusion of d ata acquisition, use the same software that was used in the calibration proc edure to identify peaks in predetermined retention time windows of interest. Use the data system software to examine the ion abundances of components of the chr omatogram. Identify a sample component by comparison of its SIM (or full scan) m ass spectrum to a SIM (or full scan) reference spectrum in the user-created databa se. The GC retention time of a method analyte should be within one to two sec of t he retention time observed for that same compound in the most recently analyzed CCC sta ndard. Ideally, the width of the retention time window should be based upon measurem ents of actual retention time variations of standards over the course of a day. Three times the standard deviation of a retention time can be used to calculate a suggest ed window size for an analyte. However, the experience of the analyst should weigh heavily in the interpretation of the chromatogram. When this method is performed in the SIM mode, verification of retention times is particularly important because l ess mass spectral information is being collected.522-30

12.2 IDENTIFICATION VERIFICATION USING ION RATIOS – When the QI of 1,4-dioxane ( m/z 88) is observed at the correct retention time, ver ify that it is truly present by verifying that the ratio of the confirma tion ion ( m/z 58) to the QI ( m/z 88) is

within an absolute ±20% of the ratio observed in a mid-range calibration standard. For example, if the ratio in the standard is 70%, then the ratio in a Field Sample must be

within 50-90%. Ratios must be determined using the integrated area s for the QI and confirmation ion from their respective mass chr omatograms. Using relative abundances obtained directly from the mass spectrum , whether or not it has undergone background subtraction, is not acceptable. Variati ons in system software and analyst subjectivity in selecting background spectra for su btraction can affect the validity of

the ratio calculation when the relative abundance f rom the spectrum is used. Using a raw spectrum (not corrected for background) can als o affect the validity of the ratio

calculation.

Use similar procedures for identification of the I S and SUR. Suggested QIs and confirmation ions for these compounds may be found in Table 2 (Sect. 17).

12.3 Calculate analyte and SUR concentrations using the multi-point calibration established in Section 10.2. Do not use daily CCC data to quan titate 1,4-dioxane or the SUR in samples. The integrated abundances of the QIs of t he analyte, SUR and IS should be used for all calculations. Adjust the final analyt e concentrations to reflect the actual sample volume as determined in Sect.11.3.3. Field Sample extracts that require

dilution should be treated as described in Section 12.4.

12.4 EXCEEDING CALIBRATION RANGE – An analyst must not extrapolate beyond the established calibration range. If an analyte resul t exceeds the range of the initial calibration curve, the extract may be diluted with DCM, with the appropriate amount of IS added to match the original concentration, an d the diluted extract injected. Acceptable SUR performance (Sect. 9.3.6.1) should b e determined from the undiluted sample extract. Incorporate the dilution factor in to final concentration calculations. The resulting sample should be documented as a dilu tion, and the MRL adjusted accordingly.

12.5 Calculations must utilize all available digits of precision, but final reported concentrations should be rounded to an appropriate number of significant figures (one digit of uncertainty), typically two, and not more than three significant figures.

NOTE: Some data in Section 17 of this method are reporte d with more than two significant figures. This is done to better illust rate the method performance data.

13. METHOD PERFORMANCE

13.1 Method performance data presented in Section 1 7 were obtained with a Thermo Finnigan Trace DSQ GC/MS system. Any GC/MS system that meets all of the QC requirements of the method may be used.522-31

13.2 PRECISION, ACCURACY, AND MINIMUM REPORTING LEV ELS – Single laboratory DLs and LCMRLs are presented in Table 3. Single laboratory accuracy and precision data from both fortified reagent wate r and fortified drinking water matrices are presented in Tables 4 and 5, respectiv ely. Two of the matrices tested were selected specifically as potentially difficult matrices because of either their relatively high TOC or high mineral content (hardne ss). There was no apparent difference in method performance when results from reagent water studies were compared to these drinking water matrices.

13.3 METHOD PERFORMANCE IN SAMPLES WITH HIGH CONCEN TRATIONS OF 1,1,1-TRICHLORETHANE – Because of its widespread us e as a chlorinated solvent stabilizer, 1,4-dioxane may be found in the presenc e of high concentrations of 1,1,1-trichloroethane. The method was tested in a high TOC water matrix with up to

500 μ g/L of 1,1,1-trichloroethane added as a co-contamin ant. No adverse affect was observed, and the method performed well within QC l imits (data not shown).

13.4 SAMPLE STORAGE STABILITY STUDIES

13.4.1 AQUEOUS SAMPLES – Chlorinated drinking water samples from a surface water source were fortified with 1,4-dioxane and pr eserved and stored as required in Section 8. Samples were extracted and analyzed in replicate (n=7) on day 0, and at five additional times points up to and beyon d 28 days. Data from these analyses validate the 28 day holding time, and are presented in Figure 2.

13.4.2 EXTRACTS – Sample extracts stored at -5 °C and protected from light were analyzed in replicate (n=7) on day 0, and at three additional time points up to and beyond 28 days. Data from these analyses validate the 28 day holding time, and are presented in Figure 3.

13.5 MULTIPLE LABORATORY DEMONSTRATION – The perfor mance of this method was demonstrated in two additional laboratories, wi th results similar to those reported in Section 17. The authors wish to acknowledge the assistance of the analysts and laboratories listed below for their participation i n the multi-lab demonstration.

13.5.1 Mr. Alan Zaffiro of Shaw Environmental and Infrastructure, Inc. under contract to the USEPA Office of Ground Water and Drinking Water Technical Support Center, Cincinnati, OH.

13.5.2 Dr. Peggy Knight and Ms. Megan Pickett of t he USEPA Region 10 Laboratory, Port Orchard, WA.

14. POLLUTION PREVENTION

14.1 This method utilizes SPE to extract the analyt e from water. It requires the use of very small volumes of organic solvent and very small qua ntities of pure analyte, thereby minimizing the potential hazards to both the analys t and the environment as compared522-32 to the use of large volumes of organic solvents in conventional liquid-liquid

extractions.

14.2 For information about pollution prevention tha t may be applicable to laboratory operations, consult “Less is Better: Laboratory Che mical Management for Waste

Reduction” available from the American Chemical Soc iety’s Department of Government Relations and Science Policy, 1155 16th Street N.W., Washington, D.C., 20036 or on-line at http://membership.acs.org/c/ccs /pub_9.htm. (accessed September 2008).

15. WASTE MANAGEMENT

15.1 The analytical procedures described in this me thod generate relatively small amounts of waste since only small amounts of reagents and s olvents are used. The matrices of concern are finished drinking water or source water . Waste management practices must be conducted consistent with all applicable ru les and regulations, and laboratories must protect the air, water, and land by minimizing and controlling all releases from fume hoods and bench operations. Com pliance is required with any sewage discharge permits and regulations, particula rly the hazardous waste identification rules and land disposal restrictions

.

16. REFERENCES

1. Winslow, S.D., Pepich, B.V., Martin, J.J., Hallberg , G.R., Munch, D.J., Frebis, C.P., Hedrick, E.J. and R.A. Krop, Statistical Procedures for Determination and Verifi cation of Minimum Reporting Levels for Drinking Water Methods

. Environ. Sci. Technol

., 40 , (2006)

281-288.

2. Glaser, J.A., Foerst, D.L., McKee, G.D., Quave, S.A . and W.L. Budde, Trace Analyses for

Wastewaters. Environ. Sci. Technol

., 15

, (1981) 1426-1435.

3. Kadokami, K., Koga, M. and Otsuki, Gas Chromatography/Mass Spectrometric Determination of Traces of Hydrophilic and Volatile Organic Compounds in Water after

Preconcentration with Activated Carbon. Analytical Sciences

, 6 , (1990) 843-849.

4. Isaacson, C., Mohr, T.K.G. and J.A. Field, Quantitative Determination of 1,4-Dioxane and Tetrahydrofuran in Groundwater by Solid Phase Extra ction GC/MS/MS. Environ. Sci.

Technol

., 40 , (2006) 7305-7311.

5. USEPA, 2006 Edition of the Drinking Water Standards and He alth Advisories. APA #822-R06-013.

6. Carcinogens - Working With Carcinogens. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Publication No. 77-206, Aug. 1977.522-33

7. OSHA Safety and Health Standards, General Industry. (29CFR1910), Occupational Safety and Health Administration, OSHA 2206, (Revised, Jul y 1, 2001).

8. Safety in Academic Chemistry Laboratories. American Chemical Society Publication, Committee on Chemical Safety, 7th Edition. Informa tion on obtaining a copy is available at http://membership.acs.org/C/CCS/pub_3.htm. (accesse d September 2008). Also available by request at OSS@acs.org522-34

17. TABLES, DIAGRAMS, FLOWCHARTS AND DEMONSTRATION DATA

Table 1. Bromofluorobenzene (BFB) Tune Verificatio n Criteria

Mass ( m/z ) Relative Abundance Criteria

50 15-40% of mass 95

75 30-80% of mass 95 95 Base peak, 100% relative abundance

96 5-9% of mass 95

173 <2% of mass 174

174 >50% of mass 95

175 5-9% of mass 174

176 >95% but <101% of mass 174

177 5-9% of mass 176

Table 2. Retention Times and Quantitation Ions (QIs )

Compound Retention Time (min) SIM Ions ( m/z )
1,4-dioxane 8.85 58 a

, 88
1,4-dioxane- d 8 (SUR) 8.77 62, 64, 96

THF- d 8 (IS) 6.68 46 , 78, 80

Note: Suggested quantitation ion in bold. a. Ion traps may give a confirmation ion of m/z 57 for 1,4-dioxane instead of the typical m/z 58 in quadrupole spectra and in many mass spectral lib raries. If the instrument has been calibrated and passes bromofluorobenzene (BFB) crit eria, then m/z 57 may be used as the confirmation ion on ion trap instruments.

Table 3. Lowest Concentration Minimum Reporting Lev el (LCMRL) and Detection

Limit (DL) Calculated for Each Extraction Option

Compound/Extraction Option LCMRL ( μ g/L) DL ( μ g/L)

1,4-dioxane (500 ml w/2-g Coconut charcoal) 0.047 0 .026 a
1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridge ) 0.036 0.020 b

a. Calculated from replicates fortified at 0.040 μ g/L, n=7. b. Calculated from replicates fortified at 0.030 μ g/L, n=8.522-35

Table 4. Demonstration of Method Performance in Rea gent Water Fortified with 1,4-Dioxane at Three Concentrations

Reagent Water Fortified at

0.030 or 0.040 μ g/L (n=7 or 8) a Compound/Extraction Option

Mean %

recovery RSD (%)

1,4-dioxane (500 ml w/2-g Coconut charcoal) 110 19
1,4-dioxane- d 8 (SUR) (500 ml w/2-g Coconut charcoal) 92 3.5 1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridge ) 110 20
1,4-dioxane- d 8 (SUR) (100 ml w/Waters AC-2 Sep-Pak cartridge) 102 3.8

Reagent Water Fortified at

1.0 μ g/L (n=6)

Mean %

recovery RSD (%)

1,4-dioxane (500 ml w/2-g Coconut charcoal) 98.0 6. 2
1,4-dioxane- d 8 (SUR) (500 ml w/2-g Coconut charcoal) 97.1 5.2 1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridg e) 101 4.2
1,4-dioxane- d 8 (SUR) (100 ml w/Waters AC-2 Sep-Pak cartridge) 105 4.8

Reagent Water Fortified at

10.0 μ g/L (n=7)

Mean %

recovery RSD (%)

1,4-dioxane (500 ml w/2-g Coconut charcoal) 93.9 2. 8
1,4-dioxane- d 8 (SUR) (500 ml w/2-g Coconut charcoal) 90.1 2.8 1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridg e) 95.2 2.9
1,4-dioxane- d 8 (SUR) (100 ml w/Waters AC-2 Sep-Pak cartridge) 99.3 3.0

a. Samples (500 mL) extracted on 2-g Coconut charco al cartridges were fortified at 0.040 μ g/L, n=7. Samples (100 mL) extracted on Waters AC-2 Sep -Pak cartridges were fortified at 0.030

μ g/L, n=8.522-36

Table 5. Demonstration of Method Performance in Dri nking Water Matrices Using Each

of the Solid Phase Extraction (SPE) Options; Matrix Samples Fortified at 1.0

μ g/L (n=7 for each matrix)

Surface Water Compound/Extraction Option

Mean %

recovery RSD (%)

1,4-dioxane (500 ml w/2-g Coconut charcoal) 99.0 a 4.9
1,4-dioxane- d 8 (SUR) (500 ml w/2-g Coconut charcoal) 100 2.5 1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridg e) 97.0 b 4.6
1,4-dioxane- d 8 (SUR) (100 ml w/Waters AC-2 Sep-Pak cartridge) 98.5 2.5

Surface Water (high in TOC) c

Mean %

recovery RSD (%)

1,4-dioxane (500 ml w/2-g Coconut charcoal) 102 3.5
1,4-dioxane- d 8 (SUR) (500 ml w/2-g Coconut charcoal) 99.8 2.4 1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridg e) 98.5 5.6
1,4-dioxane- d 8 (SUR) (100 ml w/Waters AC-2 Sep-Pak cartridge) 101 4.2

Groundwater (high in mineral content) d

Mean %

recovery RSD (%)

1,4-dioxane (500 ml w/2-g Coconut charcoal) 95.9 e 2.1
1,4-dioxane- d 8 (SUR) (500 ml w/2-g Coconut charcoal) 98.2 2.5 1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridg e) 101 f 3.3
1,4-dioxane- d 8 (SUR) (100 ml w/Waters AC-2 Sep-Pak cartridge) 104 5.9

a. Percent recovery after correction for matrix bac kground of 0.66 μ g/L. b. Percent recovery after correction for matrix bac kground of 0.42 μ g/L.

Note: Groundwater used for these Laboratory Fortified Bl anks (LFBs) was collected from the same source as the 500 mL LFBs using coconut charco al, but was collected on different days, thus the difference in matrix background concentrat ion. c. TOC measured at 4.950 mg/L. d. Hardness measured at 289 mg/L as calcium carbona te. e. Percent recovery after correction for matrix bac kground of 0.070 μ g/L. f. Percent recovery after correction for matrix bac kground of 0.080 μ g/L.522-37Table 6.Initial Demonstration of Capability (IDC) and Quality Control (QC) Requirements (Summary)MethodReferenceRequirementSpecification and FrequencyAcceptance CriteriaSect. 9.2.1Initial Demonstration ofLow BackgroundAnalyze LRB prior to any other IDC steps. When a newlot of SPE media is obtained, verify that background isat acceptable limits.Demonstrate that the method analyte is≤1/3 theMRL, and that possible interferences fromextraction media do not prevent the identificationand/or quantification of the method analyte, SURor IS.Note:This includes the absence of interferences atboth the QIs and confirmation ions at the RTs ofinterest.Sect. 9.2.2Initial Demonstration ofPrecision (IDP)Analyze 4-7 replicate LFBs fortified near the midrangecalibration concentration.%RSD must be≤20%Sect. 9.2.3Initial Demonstration ofAccuracy (IDA)Calculate average recovery for replicates used in IDP.Mean recovery±20% of true valueSect. 9.2.4Minimum ReportingLimit (MRL)ConfirmationFortify, extract and analyze 7 replicates at the proposedMRL concentration. Calculate the mean, standarddeviation and HRPIR. Confirm that the upper and lowerlimits for the Prediction Interval of Result (UpperPIR,and Lower PIR, Sect. 9.2.4.2) meet the recovery criteria.Upper PIR≤150%Lower PIR≥50%Sect. 9.2.5& 9.3.9Calibration Confirmation,Quality Control Sample(QCS)Analyze a standard from a second source (QCS) toverify the initial calibration curve.± 20% of the expected value.NOTE:Table 6 is intended as an abbreviated summary of QC requirements provided as a convenience to the method user. Because the information has beenabbreviated to fit the table format, there may be issues that need additional clarification, or areaswhere important additional information from the method textis needed. In all cases, the full text of the QC in Section 9 supersedes any missing or conflicting information in this table.522-38Table 7.Ongoing Quality Control (QC) Requirements (Summary)MethodReferenceRequirementSpecification and FrequencyAcceptance CriteriaSect. 8.3Sample Holding Time 28 days with appropriate preservation and storage asdescribed in Sections 8.1-8.3.Sample results are valid only if samples areextracted within sample hold time.Sect. 8.4Extract Holding Time28 days stored at -5 °C and protected from lightSample results are valid only if extracts areanalyzed within extract hold time.Sect. 9.3.1Laboratory Reagent Blank(LRB)One LRB with each extraction batch of up to 20 FieldSamples.Demonstrate that the method analyte concentrationis≤1/3the MRL, and confirm that possibleinterferences do not prevent quantification. If thebackground concentration exceeds1/3the MRL,results for the extraction batch are invalid.Sect. 9.3.3Laboratory FortifiedBlank (LFB)One LFB is required for each extraction batch of upto20 Field Samples. Rotate the fortified concentrationsbetween low, medium, and high amounts.Results of LFB analyses at medium and highfortifications must be 70-130% of the true value forthe analyte and SUR. Results of the low-level LFBmust be 50-150% of the true value.Sect. 9.3.5Internal Standard (IS)Compare IS area to the average IS area in the initialcalibration and the most recent CCC.Peak area counts for all injections must be within±50% of the average peak area calculated duringthe initial calibration and±30% from the mostrecent CCC. If the IS does not meet this criterion,target analyte results are invalid. Consult Sect.9.3.5 for further information.Sect. 9.3.6Surrogate(SUR)StandardsThe SUR standard added to all calibration standardsandsamples, including QC samples. Calculate SURrecoveries.SUR recovery must be 70-130% of the true value.If a SUR fails this criterion, report all results forsample as suspect/SUR recovery.Sect. 9.3.7Laboratory FortifiedSample Matrix (LFSM)Analyze one LFSM per extraction batch (of up to 20Field Samples) fortified with the method analyte ataconcentration close to but greater than the nativeconcentration. Calculate LFSM recoveries.See Sect. 9.3.7.3 for instructions on theinterpretation of LFSM results.522-39Table 7.Ongoing Quality Control (QC) Requirements (Summary)(Continued)Sect. 9.3.8Laboratory FortifiedSample Matrix Duplicate(LFSMD) or FieldDuplicates (FD)Extract and analyze at least one FD or LFSMD witheach extraction batch of up to 20 Field Samples. ALFSMD may be substituted for a FD when thefrequency of detects for 1,4-dioxane are low. CalculateRPDs.Method analyte RPDs for the LFSMD or FD shouldbe≤30% at mid and high levels of fortification and≤50% near the MRL. Failure to meet this criterionmay indicate a matrix effect.Sect. 9.3.9 Quality Control Sample(QCS)Analyze QCS during the IDC, each time CAL solutionsare prepared. A QCS must be analyzed at leastquarterly.Results must be 80-120% of the expected value.Sect. 10.2Initial CalibrationUse IS calibration technique to generate a linear orquadratic calibration curve. The number of standardsrequired is determined by the calibration range (Sect.7.2.2). Check the calibration curve as described inSection 10.2.4.When each calibration standard is calculated as anunknown using the calibration curve, the resultshould be 80-120% of the true value for all exceptthe lowest standard, which should be 60-140% ofthe true value. If this criterion is not met, reanalyzeCALs, select a different method of calibration orrecalibrate over a shorter range.Sects. 10.1and 10.2.1MS Tune Check Analyze BFB to verify MS tune each time theinstrument is calibrated.Criteria are given in Table 1.Sect. 10.3Continuing CalibrationCheck (CCC)Verify initial calibration by analyzing a calibrationstandard at the beginning of each analysis batch prior toanalyzing samples, after every 10 samples, and after thelast sample. The first CCC daily must be at or below theMRL. Subsequent CCCs alternate between medium andhigh concentrations.Low CCC – at or below the MRL concentrationMid CCC – near midpoint in initial calibration curveHigh CCC – near the highest calibration standard.Low:±50% of true valueMid:±30% of true valueHigh:±30% of true valueNote:Table 7 is intended as an abbreviated summary of QC requirements provided as a convenience to the method user. Because the information has beenabbreviated to fit the table format, there may be issues that need additional clarification, or areaswhere important additional information from the method textis needed. In all cases, the full text of Sections8-10 in the method supersedes any missing or conflicting information in this table.522-40

Figure 1. Reconstructed total ion current chromatog ram and mass chromatograms for THF- d 8 (IS), 1,4-dioxane- d 8 (SUR), and 1,4-dioxane at 0.5 μ g/mL each (the standard is equivalent to an extract of

a 10 μ g/L aqueous sample). * Peak at 6.845 min is chloro form, a chemical present in DCM.522-41 Stability of 1,4-Dioxane in Drinking Water

99.2% 95.3% 103.2% 99.4% 98.9%

0.0% 20.0% 40.0% 60.0% 80.0% 100.0% 120.0%

0 7 14 21 28

days% Recovery

Figure 2. Stability of 1,4-dioxane in preserved dr inking water stored at 4°C in the dark, over a 35- day time period. Replicate samples ( n = 7) were fortified to a concentration of 1 μ g/L 1,4-dioxane.

Matrix blank data were used to correct for native a nalyte concentrations.

Stability of 1,4-Dioxane in Extracts

93.9% 92.0% 91.2%

0.0% 20.0% 40.0% 60.0% 80.0% 100.0% 120.0%

0 14 28

days% Recovery

Figure 3. Stability of 1,4-dioxane in sample extra cts stored at -5°C, in the dark, over a 42-day time period. Replicate samples ( n = 7) were fortified to a concentration of 10 μ g/L 1,4-dioxane.