EPA/600/R-08/101
METHOD 522 DETERMINATION OF 1,4-DIOXANE IN DRINKING 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 45268
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METHOD 522
DETERMINATION OF 1,4-DIOXANE IN DRINKING WATER BY SOLID PHASE
EXTRACTION (SPE) AND GAS CHROMATOGRAPHY/MASS SPECTROMETRY
(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 drinking water. Accuracy and
precision data have been generated in reagent water, finished ground and surface
waters. Although this method was developed and demonstrated 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 based on the intended use of this
method. Two single laboratory Lowest Concentration Minimum Reporting Levels
(LCMRLs) of 0.036 and 0.047 ug/L have been determined in reagent water. The
single laboratory LCMRL is the lowest true concentration for which the future
recovery is predicted to fall, with high confidence (99%), between 50 and 150%
recovery. The procedure used to determine the LCMRLs 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 laboratory MRL for this method meets
the requirements described in Section 9.2.4.
1.4 Determining the Detection Limit (DL) for analytes in this method is optional (Sect.
9.2.6). Detection limit is defined as the statistically calculated minimum concentration
that can be measured with 99% confidence that the reported value is greater than zero.2
The DL is compound dependent and is dependent on extraction efficiency, sample
matrix, fortification concentration, and instrument performance.
1.5 This method is intended for use only by analysts skilled 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 technological 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). Method modifications should be
considered only to improve method performance. Modifications 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, modifications should not sacrifice
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chromatographic separations in the interest of method turnaround time. Because the
method analyte, surrogate analyte (SUR) and internal standard (IS) have only very low
mass ions in their mass spectra, and SIM is being used, it is important to strive for
chromatographic separation from potential interferences. In all cases where method
modifications are proposed, the analyst must perform 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 demonstrate that method performance can
be verified in a real sample matrix (Sect. 9.3.7 and 9.4).
NOTE: The above method flexibility section is intended as an abbreviated summation
of method flexibility. Method Sections 4-12 provide detailed information of specific
portions of the method that may be modified. If there is any perceived conflict
between the general method flexibility statement in this section and specific
information in Sections 4-12, Sections 4-12 supersede 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-dioxane-t/g. The sample is extracted
by one of two SPE options. In option 1, a 500-mL sample is passed through an SPE
cartridge containing 2 g of coconut charcoal to extract the method analyte and SUR.
In option 2, a 100-mL sample is extracted on a Waters AC-2 Sep-Pak or Supelco
Supelclean ENVI-Carb Plus cartridge. In either option, the compounds are eluted
from the solid phase with a small amount of dichloromethane (DCM), approximately
9 mL or 1.5 mL, respectively. The extract volume is adjusted, and the IS,
tetrahydrofuran-J8 (THF-J8), is added. Finally, the extract is dried with anhydrous
sodium sulfate. Analysis of the extract is performed by GC/MS. The data provided in
this method were collected using splitless injection with a high-resolution fused silica
capillary GC column that was interfaced to an MS operated 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 and 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 sensitivity, 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 analyzed on the same instrument
during a 24-hour period that begins and ends with the analysis of the appropriate
Continuing Calibration Check (CCC) Standards. Additional CCCs may be required
depending on the length of the analysis batch and/or the number of Field Samples.
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3.2 CALIBRATION STANDARD (CAL) - A solution prepared from stock standard
solution(s) and the ISs and SURs. The CAL solutions are used to calibrate the
instrument response with respect to analyte concentration.
3.3 CONTINUING CALIBRATION CHECK (CCC) STANDARD - A calibration
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% confidence that the analyte concentration
is greater than zero. This is a statistical determination (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 Samples (not including QC
samples) extracted together by the same person(s) during a work day using the same
lot of SPE devices, solvents, SUR solution, and fortifying solutions. Required QC
samples include Laboratory Reagent Blank (LRB), Laboratory Fortified Blank (LFB),
Laboratory Fortified Sample Matrix (LFSM), and either a Field Duplicate (FD1 and
FD2) or Laboratory Fortified Sample Matrix Duplicate (LFSMD).
3.6 FIELD DUPLICATES (FD1 and FD2) - Two separate samples collected at the same
time and place under identical circumstances, and treated exactly the same throughout
field and laboratory procedures. Analyses of FD1 and FD2 give a measure of the
precision associated with sample collection, preservation, 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 or standard solution in a known
amount and used to measure the relative responses of the method analyte and SUR.
The IS must be an analyte that is not a sample component.
3.8 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water or other
blank matrix to which known quantities of the method analyte and all the preservation
compounds are added. The LFB is processed and analyzed 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 precise measurements.
3.9 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) - An aliquot of a Field
Sample to which known quantities of the method analyte and all the preservation
compounds are added. The LFSM is processed and analyzed 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 duplicate 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 prepare the LFSM, which is fortified,
extracted and analyzed identically to the LFSM. The LFSMD is used instead of the
Field Duplicate to access method precision and accuracy 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 including 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 environment, the reagents, or the apparatus.
3.12 LOWEST CONCENTRATION MINIMUM REPORTING LEVEL (LCMRL) - The
single-laboratory LCMRL is the lowest true concentration 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 information provided by
vendors concerning a chemical's toxicity, health hazards, physical properties, fire, and
reactivity data including storage, spill, and handling precautions.
3.14 MINIMUM REPORTING LEVEL (MRL) - The minimum concentration that can be
reported by a laboratory as a quantitated value for a target analyte in a sample
following analysis. This defined concentration must meet the criteria defined in
Section 9.2.4 and must not be any lower than the concentration of the lowest
calibration standard for that analyte. A laboratory 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 standard 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 source of calibration standards. The
second source SSS is used to fortify the QCS at a known concentration. The QCS is
used to check calibration standard integrity.
3.16 SELECTED ION MONITORING (SIM) - A GC/MS technique where only one or a
few ions are monitored. When used with gas chromatography, the set of ions
monitored is usually changed periodically throughout the chromatographic run, to
correlate with the characteristic ions of the analyte, 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 assayed reference materials or
purchased from a reputable commercial source.
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3.18 SURROGATE ANALYTE (SUR) - A pure analyte, which 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 measured 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. Wash glassware with detergent and tap
water, rinse with tap water, followed by reagent water. 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 air dried.
4.2 Method interferences may be caused by contaminants in solvents, reagents (including
reagent water), sample bottles and caps, and other sample processing hardware that
lead to discrete artifacts and/or elevated baselines in the chromatograms. All items
such as these must be routinely demonstrated to be free from interferences (less than
*/3 the MRL for the method analyte) under the conditions 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 numerous low molecular
weight compounds that contain interfering ions which may prohibit accurate
identification and quantitation of the analyte, SUR and IS.
4.4 Matrix interferences may be caused by contaminants that are co-extracted from the
sample. The extent of matrix interferences will vary 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 potential 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 source of interferences. The analysis of
field and laboratory reagent blanks can provide important information regarding the
presence or absence of such interferences. Brands and lots of SPE devices should be
tested to ensure that contamination does not preclude analyte identification and
quantitation.
4.7 Analyte carry-over may occur when a relatively "clean" sample is analyzed
immediately after a sample containing relatively high concentrations of compounds.
Syringes and splitless injection port liners must be cleaned carefully or replaced as
needed. After analysis of a sample containing high concentrations of compounds, a
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LRB should be analyzed to ensure that accurate values are obtained for the next
sample. During automated GC/MS analyses, extracts with positive results that were
analyzed immediately following a sample with high concentrations of the analyte,
should be reanalyzed after analyzing an acceptable LRB. If the analyte is not detected
in extracts analyzed immediately after a high concentration extract, no reanalysis is
necessary.
4.8 Silicone compounds may be leached from punctured autosampler 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 regularly spaced chromatographic
peaks with similar fragmentation patterns. They can unnecessarily complicate the
total ion chromatogram and may cause interferences at high levels.
4.9 High laboratory background levels of 1,4-dioxane 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. Each laboratory is responsible for maintaining an
awareness of OSHA regulations regarding safe handling of chemicals used in this
method. A reference file of MSDSs should be made available to all personnel
involved in the chemical analysis. Additional references on laboratory safety are
available.6"8
5.2 Pure standard materials and stock standard solutions 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 preservative to inhibit microbial growth and
potential decay of 1,4-dioxane. Sodium bisulfate is 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 endorsement of the product.)
6.1 SAMPLE CONTAINERS - Glass bottles fitted with polytetrafluoroethylene (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.
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6.2 VIALS - Various sizes of glass vials with PTFE-lined screw caps for storing standard
solutions and extracts, including glass 2-mL autosampler vials with PTFE-faced septa.
6.3 VOLUMETRIC FLASKS - Class A, various sizes, including 1, 5, and 10 mL for
preparation of standards. A 2-mL volumetric collection 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, including 100 and 500 mL for
measurement of sample volumes.
6.5 MICRO SYRINGES - Suggested sizes include 10, 25, 50, 100, 250, 500, and
1000 uL.
6.6 CONICAL CENTRIFUGE TUBES - 15 mL, glass, with graduations at 0.1 mL and
PTFE-lined screw caps (KEVIAX #45166 or equivalent), suitable for collection of the
eluent from the 2-g solid phase cartridge after extraction.
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 acceptable for use in this method
are made of either coconut charcoal or synthetic carbon 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 um). At the time of method development, pre-packed cartridges were
obtained from Restek Corporation (cat. # 26032) and United Chemical
Technologies (UCT; cat. # EU52112M6). Equivalent brands 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 Sep-
Pak 400-mg activated carbon SPE cartridge (cat. # JJAN20229; 85 um
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 flow/vacuum control
(Supelco cat. # 57250-U or equivalent).
6.8.3 SAMPLE DELIVERY SYSTEM - Use of a transfer tube system (Supelco
"Visiprep", cat. # 57275 or equivalent), which transfers the sample directly from
the sample container to the SPE cartridge, is recommended. Sample reservoirs
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(Varian, cat. #12131012 or equivalent), which attach to the cartridge, may be
used, although they hold only a limited volume of sample.
6.8.4 An automatic or robotic system designed for use with SPE cartridges may be used
if all QC requirements discussed in Section 9 are met. Automated systems may
use either vacuum or positive pressure to process samples and solvents through
the cartridge 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 accommodate the use of an automated system.
6.9 LABORATORY OR ASPIRATOR VACUUM SYSTEM - Sufficient capacity to
maintain a vacuum of approximately 15 to 25 inches of mercury.
6.10 GAS CHROMATOGRAPH/MASS SPECTROMETER (GC/MS) SYSTEM
6.10.1 FUSED SILICA CAPILLARY GC COLUMN - Data presented in this method
were obtained with a column typically used for volatiles analysis: Varian CP
Select 624, 30 m x 0.25-mm i.d. with a 1.4 um film thickness, or equivalent.
Other types of columns may be used. However, use of shorter or thinner film
columns is not recommended because this will result in loss of resolution and
very short retention times. Because the method analyte, SUR and IS have only
very low mass ions in their spectra, and SIM is being used, it is important to strive
for chromatographic separation from any potential interferences. See Section 9.4
regarding the use of alternate GC columns.
CAUTION: If a GC column and/or temperature program different than that
described in this method is used, the analyst must verify that the temperature
program and subsequent column bake-out is sufficient to remove all injected
material from the column. Although the retention times of the method analyte,
IS and SUR are short, many chemicals may be co-extracted by carbon SPE and
these need to be eluted from the GC column to prevent 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 techniques such as temperature
programmed injections, cold on-column injections and large volume injections
may be used if the QC criteria in Section 9 are met. Equipment designed
appropriately for these alternate types of injections 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 millimeters 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.
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6.10.4 MASS SPECTROMETER (MS) - Any type of mass spectrometer 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 option on all instruments. The
spectrometer must produce a mass spectrum that meets all criteria in Table 1
when a solution containing approximately one to two nanograms of bromo-
fluorobenzene (BFB) is injected into the GC/MS. This test must be performed in
the full scan mode. Use a single spectrum at the apex 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 peak. Ten scans across
chromatographic peaks are recommended.
6.10.5 DATA SYSTEM - An interfaced data system is required 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 received 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 intended that all reagents will conform to
the specifications of the Committee on Analytical Reagents of the American Chemical
Society (ACS), where such specifications are available. 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 determination. During method development,
only purge and trap grade methanol was found to be sufficiently free from low
molecular weight interferences (as described in Sect. 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 compounds at or above l/3 the
MRL for 1,4-dioxane. In addition, there must be no interferences with the SUR
or IS.
713 METHANOL (CASRN 67-56-1) - Purge and trap grade only (see Section 4.3V
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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 GC2, 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 400 °C for two hours in a
muffle furnace. An "ACS grade, suitable for pesticide residue analysis", or
equivalent, of anhydrous sodium sulfate is recommended.
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) - Anhydrous, 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 concentrations may be used as
necessary depending on instrument sensitivity and the calibration range used.
Standards for sample fortification generally should be prepared in the smallest volume
that can be accurately measured to minimize the addition of excess organic solvent to
aqueous samples. During method development, standard 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 method is solvent evaporation.
Therefore, it is recommended that standard solutions be stored at 0 °C or less, with
minimal headspace. Laboratories should use standard QC practices to determine when
standards need to be replaced. Standard QC practices, such as monitoring area counts
and recovery percentages of CCCs, would help to determine if a standard requires
replacement. As mentioned above, the major form of "standard deterioration" is
solvent evaporation, which would result in a continuous increase in area counts, and in
some cases, target and SUR recoveries. During method development, SSSs and
dilutions of SSSs of 1,4-dioxane, THF-Jg, 1,4-dioxane-dg, and BFB were valid for at
least 6 months after opening/preparation. Expiration dates provided by the vendor
should be used as an indicator of SSS shelf life prior to opening.
NOTE: Only purge and trap grade methanol may be used in the preparation of
standards and sample fortification solutions.
7.2.1 STOCK STANDARD SOLUTIONS (SSS) - Stock standard solutions of the
method analyte, SUR and IS are commercially available from multiple
commercial sources. It is recommended that these solutions be purchased from
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commercial sources. However, they may be prepared from neat materials.
Utilizing stock standards prepared in methanol allows the same stock standard to
be used to prepare both calibration standards and sample fortification solutions.
The concentrations of the stock standard solutions used during method
development were 1000-2000 ug/mL.
7.2.1.1 PREPARATION OF STOCK STANDARD SOLUTIONS (SSS) 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 or until all alcohol
wetted surfaces have dried. Weigh to the nearest 0.1 mg.
7.2.1.1.2 Using a 100 uL-syringe, quickly add two or more drops of the neat
standard material to the flask. Be sure that the standard falls directly
into the alcohol, without contacting the neck of the flask.
7.2.1.1.3 Quickly reweigh, dilute to volume and mix by inverting the flask
several times. Calculate the concentration in ug/uL from the net gain
in weight.
7.2.1.1.4 Store SSS in 12-15 mL glass vials with PTFE lined screw caps.
7.2.2 CALIBRATION STANDARD SOLUTIONS (CAL) - Prepare a series of
calibration standards to encompass the desired calibration range. Calibration
standards must contain varying amounts of 1,4-dioxane, and a fixed amount of
both the SUR and the IS, and be prepared in DCM. The number of standards
required is determined by the calibration range. Three standards are required for
one order of magnitude, six standards for two orders of magnitude and nine
standards for three orders of magnitude. The calibration curve associated with the
demonstration data in Section 17 contained nine standards with concentrations of
1,4-dioxane ranging from 0.002 ug/mL to 1.0 ug/mL. (This corresponds to a
concentration range of 0.04-20 ug/L in the drinking water samples.) The
concentrations of both l,4-dioxane-t/8 (SUR) and the THF-J8 (IS) were
0.500 ug/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 (Sect. 11.3.5). The
number of solutions needed depends upon the calibration range and/or
sample volume. During method development, two solutions at
concentrations of 20 ug/mL and 200 ug/mL were used to fortify 100-mL
and 500-mL samples, respectively.
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7.2.3 .2 SURROGATE ANALYTE (SUR) FORTIFICATION SOLUTION -
Prepare one or more solutions of l,4-dioxane-6?8 in methanol to be used for
fortification of the SUR into samples, LFBs, LRBs and LFSMs
(Sect. 11.3.4). The concentrations used during method development were
200 ug/mL and 2000 ug/mL (STOCK) to fortify 100-mL and 500-mL
samples, respectively.
7.2.3 .3 INTERNAL STANDARD (IS) FORTIFICATION SOLUTION - Prepare
one or more solutions of THF-Jg 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 ug/mL and 1000 ug/mL
(STOCK), used to fortify 2-mL and 10-mL extracts, respectively.
7.2.4 GC/MS TUNE CHECK SOLUTION - Stock standard solutions of BFB (CASRN
460-00-4) are available commercially. Prepare a BFB solution at a concentration
of 1-2 ug/mL in DCM by dilution of the stock standard. Store this solution in an
amber glass screw cap vial at 0 °C or less. To prepare 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, listed in the table below, are
added to each sample at the time of sample collection. Sodium sulfite must be added
first and may be placed as a dry material in the sample 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 solutions 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
Sodium sulfite
Sodium bisulfate
Amount
50mg/L
1 g/L (approx)
Purpose
Reduce chlorine/chloramine residual
Microbial inhibitor
8.2 SAMPLE COLLECTION
8.2.1 Open the tap and allow the system to flush until the water temperature has
stabilized (approximately three to five min). Collect 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 and agitate by hand until the sodium
sulfite is dissolved. Add enough sodium bisulfate such that the final
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concentration will be 1 g/L. Cap the bottle and mix until dissolved. Unless field
verification of pH is to be performed, keep the sample sealed until just prior to
extraction.
8.2.4 Field verification of pH 4 (optional). It is anticipated that 1 g/L of sodium
bisulfate will be sufficient to acidify most samples to < pH 4. If there is reason to
suspect that more may be needed, the pH can be verified with narrow range pH
paper at the time of sample collection. After acidification 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 paper package. If the pH is > 4,
add additional sodium bisulfate until pH < 4 is obtained. Seal the bottle, and keep
the sample sealed until extraction.
8.3 SAMPLE SHIPMENT AND STORAGE - Samples must be chilled 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 at the time of collection, samples
may need to be refrigerated to reduce their temperature before being packed on ice for
shipment. Samples stored in the lab must be held at or below 6 °C until extraction, but
should not be frozen. Freezing samples may compromise the sealed cap or result in
sample bottle breakage.
8.3.1 Verification of sample dechlorination - Upon the receipt of samples at the
laboratory, verify that Field Samples were dechlorinated 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 samples 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 from light for an additional 28 days.
9. QUALITY CONTROL
9.1 QC requirements include the Initial Demonstration of Capability (IDC) and ongoing
QC requirements that must be met when preparing and analyzing Field Samples. This
section describes each QC parameter, its required frequency, and the performance
criteria that must be met in order to meet USEPA quality 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 acceptable QC criteria.
Laboratories are encouraged to institute additional QC practices to meet their specific
needs. If method modifications are under consideration 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 the
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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 - Before 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 that a LRB is reasonably free of
any contamination that would prevent the identification 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 contaminants that could
interfere with the determination of the method analyte, SUR or IS.
Although extraction media are generally made of inert materials, they may
still contain extractable organic material. If the background contamination
is sufficient to prevent accurate and precise measurements, the condition
must be corrected before proceeding with the IDP (Sect. 9.2.2).
9.2.1.2 Other sources of background contamination are solvents, reagents (including
reagent water), room air and glassware. Background contamination must be
reduced to an acceptable level before proceeding with 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 intermittent issue, the analyst
must not attempt to verify an MRL less than the mean LRB concentration
+ 3o, or three times the mean LRB concentration, whichever is greater.
NOTE: Although quantitative data below the MRL may not be reliably
accurate enough for data reporting, such data are useful in determining an
MRL cut off for the method analyte if it is found in the LRB. Therefore,
blank contamination levels may be estimated by extrapolation, when the
concentration is below the lowest calibration standard. This also applies to
estimating LRB concentrations for daily low background verification.
9.2.2 INITIAL DEMONSTRATION OF PRECISION (IDP) - Prepare, extract, and
analyze four to seven replicate LFBs fortified near the midrange of the initial
calibration curve according to the procedure described in Section 11. Sample
preservatives as described in Section 8.1 must be added 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) - Using the same set of
replicate data generated for Section 9.2.2, calculate average recovery. The
average recovery of the replicate values must be within ± 20% of the true value.
9.2.4 MINIMUM REPORTING LEVEL (MRL) CONFIRMATION - Establish 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 another
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regulatory body. Establish an Initial Calibration following the procedure outlined
in Section 10.2. The lowest calibration standard used 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 MRL 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 prediction interval of results
(HRpiR) using the equation below
HRpm = 3.963S
where S is the standard deviation, and 3.963 is the constant 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 identification criteria in Sections 12.1
and 12.2, i.e., the MRL verification may not be performed on LFBs where
only the base peak is observed. If during MRL confirmation all
identification ions are not observed, the MRL selected is too low.
9.2.4.2 Confirm that the upper and lower limits for the Prediction Interval of Result
(PIR = Mean +_ HRpjR) meet the upper and lower recovery limits as shown
below.
The Upper PIR Limit must be < 150% recovery.
Mean + HRpm
^ xlOO% <150%
FortifiedConcentration
The Lower PIR Limit must be > 50% recovery.
Mean-HRpm
^ xlOO% > 50%
FortifiedConcentration
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 these criteria are not met, the
MRL for 1,4-dioxane has been set too low and must be re-evaluated at a
higher concentration.
9.2.5 CALIBRATION CONFIRMATION - Analyze a QCS as described in Section
9.3.9 to confirm the accuracy of the standards and calibration curve.
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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 compliance monitoring. It is the
responsibility of the laboratory to determine ifDL determination is required
based upon the intended use of the data.
Replicate analyses for this procedure should be done over at least three days (i.e.,
both the sample extraction and the GC analyses should be done over at least three
days). Prepare at least seven replicate LFBs containing 1,4-dioxane at a
concentration estimated to be near the DL. This concentration may be estimated
by selecting a concentration at two to five times the noise level. The appropriate
fortification concentrations will be dependent upon the sensitivity of the GC/MS
system used. All preservation reagents listed in Section 8.1 must also be added to
these samples. Analyze the seven replicates through all steps of Section 11.
NOTE: If an MRL confirmation data set meets these requirements, a DL may be
calculated from the MRL confirmation data, and no additional analyses are
necessary.
Calculate the DL using the equation
l—sl—i — *J <"* / / -11 r\ r\r\\
(n-\ l-ctr=0.99)
where:
s = standard deviation of replicate analyses
t («-i, i-a=o.99) = Student's t value for the 99% confidence level with n-\
degrees of freedom
n = number of replicates.
NOTE: There are no precision and accuracy requirements for the DL replicates.
Do not subtract blank values when performing DL calculations.
9.3 ONGOING QC REQUIREMENTS - This section summarizes the ongoing QC
criteria that must be followed when processing and analyzing Field Samples.
9.3.1 LABORATORY REAGENT BLANK (LRB) - An LRB is required with each
extraction batch to confirm that potential background contaminants are not
interfering with the identification or quantitation of the method analyte, SUR or
IS. If the LRB produces a peak within the retention time window of any analyte
that would prevent the identification or quantitation of that analyte, determine the
source of contamination and eliminate the interference before processing samples.
Background contamination must be reduced to an acceptable level before
proceeding.
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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 measurement of 1,4-dioxane must be
below */3 of the MRL. Blank contamination may be estimated by extrapolation, if
the concentration is below the lowest calibration standard. 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 concentrations equal to or greater than
this level, then all data for the analyte must be considered invalid for all samples
in the extraction batch.
9.3.2 CONTINUING CALIBRATION CHECK (CCC) - CCC Standards are analyzed
at the beginning of each analysis batch, after every ten Field Samples, and at the
end of the analysis batch. See Section 10.3 for concentration requirements and
acceptance criteria.
9.3.3 LABORATORY FORTIFIED BLANK (LFB) - An LFB is required with each
extraction batch. The fortified concentration of the 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 calibration (Sect. 10.2). Results of
the low-level LFB analyses must be 50-150% of the true 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-dioxane, then all data must be
considered invalid for all samples in the extraction 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 Tune Check are summarized in
Section 17, Table 1. The MS Tune Check must be performed each time a major
change is made to the mass spectrometer, and prior to establishing and/or re-
establishing an initial calibration (Sect. 10.2). In this method, daily BFB analysis
is not required.
9.3.5 INTERNAL STANDARDS (IS) - The analyst must monitor 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 response in the most recent CCC
by more than 30%, and must not deviate by more than 50% from the mean area
measured during initial analyte calibration. If the IS area in a chromatographic
run does not meet these criteria, inject a second aliquot of that extract.
9.3.5.1 If the reinjected aliquot produces an acceptable 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 calibration standard. If the
calibration standard fails the criteria of Section 10.3, recalibration is in order
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per Section 10.2. If the calibration standard is acceptable, extraction of the
sample may need to be repeated provided the sample is still within the
holding time. Otherwise, report results obtained from the reinjected extract,
but annotate as "suspect/IS recovery." Alternatively, collect a new sample
and re-analyze.
9.3.6 SURROGATE (SUR) RECOVERY - The SUR standard is fortified into the
aqueous portion of all samples, LRBs, LFBs, CCCs, LFSMs 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 final chromatographic
measurement. Calculate the percent recovery (%R) for the SUR using the
equation
( A\
%R = — xlOO
UJ
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. Correct the problem and
reanalyze the extract.
9.3.6.2 If the extract reanalysis meets the SUR recovery 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, recalibration is in order per Section
10.2. If the calibration standard is acceptable, extraction of the sample
should be repeated provided the sample is still within the holding time. If
the re-extracted sample also fails the recovery criterion, report all data for
that sample as "suspect/SUR recovery" to inform the data user that the
results are suspect due to SUR recovery. Alternatively, 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 used to determine that the
sample matrix does not adversely affect method accuracy. If the occurrence of
1,4-dioxane in the samples is infrequent, or if historical trends are unavailable, a
LFSMD must be prepared, extracted, and analyzed from a duplicate Field Sample
to assess method precision (Sect. 9.3.8). Extraction batches that contain LFSMDs
do not require the analysis of a Field Duplicate. If a variety of different sample
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matrices are analyzed regularly, for example, drinking water from groundwater
and surface water sources, method performance should be established for each.
Over time, LFSM data should be documented by the laboratory 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 is prepared by spiking
a sample with an appropriate amount of the Analyte Fortification Solution
(Sect. 7.2.3.1). Select a spiking concentration that 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
C
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 concentrations above the
DL but below the MRL, and are fortified at concentrations at or near the
MRL, should be corrected for the native levels in order to obtain
meaningful %R values. This example and the LRB (Sect. 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 MRL (within a factor of two
times the MRL concentration) where 50-150% recoveries are acceptable. If
the accuracy of any analyte falls outside the designated 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/matrix" 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 batch, a minimum of
one Field Duplicate (FD) or Laboratory Fortified Sample Matrix Duplicate
(LFSMD) must be analyzed. Duplicates check the precision associated with
sample collection, preservation, storage, and laboratory procedures. If method
analytes are not routinely observed in Field Samples, an LFSMD should be
analyzed rather than an FD.
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9.3.8.1 Calculate the relative percent difference (RPD) for duplicate FD
measurements (FD1 and FD2) using the equation
FDI-FD2
RPD=-, :—xlOO
(FD\ + FD2}/2
9.3.8.2 RPDs for FDs should be < 30%. Greater variability may be observed when
FDs have analyte concentrations that are within a factor 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 control 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 inform the data user that
the results are suspect due to matrix effects. Failure to meet the FD criteria
is a reflection of the performance of the method for that individual sample,
and does not constitute analysis or extraction batch failure.
9.3.8.3 If an LFSMD is analyzed instead of a FD, calculate the relative percent
difference (RPD) for duplicate LFSMs (LFSM and LFSMD) using the
equation
LFSM-LFSMD
RPD=- :—XlOO
(LFSM+LFSMD} 12
9.3.8.4 RPDs for duplicate LFSMs should be < 30% for samples fortified at or
above their native concentration. Greater variability may be observed when
LFSMs are fortified at analyte concentrations that are within a factor of two
of the MRL. LFSMs fortified at these concentrations should have RPDs
that are < 50% for samples fortified at or above their native concentration.
If the RPD of the analyte falls outside the designated 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 result for that analyte in the
unfortified sample is labeled "suspect/matrix" to inform the data user that
the results are suspect due to matrix effects. Failure to meet the
LFSM/LFSMD criteria is a reflection of the performance of the method for
that individual sample, and does not constitute analysis or extraction batch
failure.
9.3.9 QUALITY CONTROL SAMPLES (QCS) - As part of the 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 the 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 be ± 20% of the expected
value. If measured analyte concentrations are not of acceptable accuracy, check
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the entire analytical procedure to locate and correct the problem, or obtain another
QCS.
9.4 METHOD MODIFICATION QC REQUIREMENTS - The analyst is permitted to
modify the GC injection technique, GC column and conditions, and MS conditions.
9.4.1 Each time method modifications are made, the analyst must repeat the procedures
of the IDC (Sect. 9.2) and verify that all QC criteria can be met in ongoing QC
samples (Sect. 9.3).
9.4.2 The analyst is also required to evaluate and document method performance for the
proposed method modifications in real matrices that span the range of waters that
the laboratory analyzes. This additional step is required because modifications
that perform acceptably in the IDC, which is conducted in reagent water, can fail
ongoing method QC requirements in real matrices. This is particularly important
for methods subject to matrix effects. If, for example, the laboratory analyzes
finished waters from both surface and groundwater municipalities, this
requirement can be accomplished by assessing precision and accuracy (Sects.
9.2.2 and 9.2.3) in a surface water with moderate to high Total Organic Carbon
(TOC) (e.g., 2 mg/L or greater) and a hard groundwater (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 appropriately documented by the
analyst and should be independently assessed by the laboratory's Quality
Assurance (QA) officer prior to analyzing Field Samples.
9.4.3.1 When implementing method modifications, it is the responsibility of the
laboratory to closely review the results of ongoing QC, and in particular, the
results associated with the LFBs (Sect. 9.3.3), LFSMs (Sect. 9.3.7), FDs or
LFSMDs (Sect. 9.3.8), CCCs (Sect. 9.3.2), and the IS area counts (Sect.
9.3.5). If repeated failures are noted, the modification 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 establishing or re-establishing an
initial calibration.
10.2 INITIAL CALIBRATION
10.2.1 MS TUNE/MS TUNE CHECK - Operate the MS in the electron ionization (El)
mode. Calibrate the mass and abundance scales of the MS with calibration
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compounds and procedures prescribed by the manufacturer 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 such that
a minimum of five scans (10 scans are recommended) are obtained during the
elution of the BFB chromatographic peak Use a single spectrum 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. If 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 calibration.
10.2.2 ANALYTE CALIBRATION - Operating conditions used during method
development are described below. Data were obtained using SIM on a
quadrupole MS system using the GC column described in Section 6.10.1.
Conditions different from those described may be used if QC criteria in Section 9
are met. Different conditions include alternate GC columns, temperature
programs, MS conditions, and injection techniques and volume, such as cold on-
column and direct injection port liners and/or large 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 l-|iL aliquot of
each CAL prepared as in Section 7.2.2 into a hot, splitless injection port
held at 200 °C with a split delay of 0.5 min. Temperature program the GC
as follows: initial oven temperature of 30 °C, hold for 1.0 min, ramp at
7 °C/min to 90 °C, ramp at 20 °C/min to a final temperature of 200 °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 operated 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 °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 type of MS may be
used as detailed in Sect. 6.10.4. Data shown in Section 17 (Tables 2-5) were
obtained in the SEVI mode. Operation of the MS in this mode enhances
sensitivity. However, less mass spectral data are obtained for all peaks
including the method analyte, SUR, IS and any potential interferences.
Because of this, and because the selected ions for the compounds of interest
are very low masses that are likely to occur more frequently in interferences
than most higher mass ions, the analyst should also rely on chromatography
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to reduce the possibility of false positives. It is highly recommended that a
GC column at least 30 m in length with a film thickness of at least 1.4 um
be used to provide adequate separation of the compounds 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 Segment 1
(6 to 8 min). Segment 2 (8 to 18 min) was set to scan 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 required. 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 chromatogram obtained
during method development using the instrumental conditions described in
this section is shown in Figure 1.
10.2.3 CALIBRATION CURVE - Use the GC/MS software to create a calibration curve
for 1,4-dioxane using the IS technique. Concentrations 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 quantitated using the
calibration curve, each calibration point, except the lowest point, should calculate
to be within 80-120% of its true value. The lowest point should calculate to be
within 60-140% of its true value. If these criteria 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 the range of calibration, or select
an alternate method of calibration.
10.3 CONTINUING CALIBRATION CHECK (CCC) - The CCC verifies 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 CCCs 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 CALs.
10.3.1 Inject an aliquot of the appropriate concentration CAL solution and analyze with
the same conditions used during the initial calibration.
10.3.2 Determine that the absolute area of the QI of 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 this
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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 and the SUR in the check standard.
The calculated amount for 1,4-dioxane for medium and 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 less than or equal to the MRL,
must be within ± 50% of the true value. If these criteria 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 recalibration. Any Field Sample
extracts that have been analyzed since the last acceptable calibration verification
should be re-analyzed after adequate calibration has 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 extracts show no detection for
the target compound, non-detects may be reported without re-analysis.
10.3.4 REMEDIAL ACTION - Failure to meet CCC QC performance criteria may
require remedial action. Major maintenance such as cleaning the ion source,
cleaning the mass analyzer, replacing filament assemblies, replacing the GC
column, etc., require returning to the initial calibration 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 device. If an automatic system is used
to prepare samples, follow the manufacturer's operating 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 accommodate 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 well 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 described in Sect. 6.8.1, and extract
analysis.
NOTE: The SPE cartridges and sodium sulfate drying materials described in this
section are designed as single use items and must be discarded after use. They may
not be refurbished for re-use in subsequent analyses.
NOTE: Only purge and trap grade methanol may be used in this extraction (see
Sect. 4.3).
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11.3 SAMPLE PREPARATION
11.3.1 All Field and QC samples (LRBs and LFBs) must contain the dechlorinating
agent, sodium sulfite. Verify that Field Samples were 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 according 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), must 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 laboratory). 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 volume by filling the bottle to the
mark with water and transferring to an appropriately 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 collected 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 sample volume will depend upon
the SPE being used (Sects. 11.4, 11.5).
Alternatively, the sample volume may be calculated by weighing the sample
bottle before and after extraction (or sample transfer) and using a density of
l.Og/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 uL of a 2000-ug/mL solution to a 500-mL
sample will result in a concentration of 10 ug/L. Addition of 5 uL of a
200-ug/mL solution to a 100-mL sample will also result in a concentration of
10 ug/L.
11.3.5 FORTIFICATION WITH METHOD ANALYTE - If the sample 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 components are properly mixed.
Addition of 2.5 uL of a 200-ug/mL solution to a 500-mL sample will result in a
concentration of 1 ug/L. Addition of 5 uL of a 20-ug/mL solution to a 100-mL
sample will also result in a concentration of 1 ug/L.
11.3.6 Proceed with sample extraction Option 1 (Sect. 11.4) or Option 2 (Sect. 11.5).
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11.4 SPE PROCEDURE OPTION 1; EXTRACTION OF 500-ML SAMPLES - Proper
conditioning of the solid phase sorbent can have a marked effect on method precision
and accuracy. This section describes the SPE procedure using 2-g coconut charcoal
cartridges and the transfer tube system and SPE manifold 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 the cartridge to go dry at the
end. From this point forward, do not allow the cartridge 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 times, without allowing the
cartridge to go dry in between washes or at the end.
11.4.2 SAMPLE EXTRACTION - Attach a transfer tube from 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 draw air through the cartridge for
10 min at full vacuum. Turn off and release the vacuum. Proceed immediately
with cartridge elution.
11.4.3 CARTRIDGE ELUTION - Lift the extraction manifold top and insert a rack with
collection tubes into the vacuum manifold tank to collect the extracts as they are
eluted from the cartridges. Fill each cartridge with DCM. Pull enough of the
solvent into the cartridge at low vacuum to soak the 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 cartridge 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 10 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 5 uL of a
1000-ug/mL IS solution to a 10-mL extract will result in an IS concentration of
500 ng/mL. Mix well. A vortex mixer is recommended. To eliminate residual
water, add approximately 2 g of anhydrous sodium sulfate. Mix well. Transfer
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aliquots of the extract to autosampler vials, or other glass vials, for storage until
analysis.
NOTE: Experiments during method development indicated that this extract
cannot be reliably concentrated by nitrogen evaporation because of the volatility
of the method analyte. Therefore, extract concentration to enhance sensitivity is
not permitted.
11.5 SPE PROCEDURE OPTION 2; EXTRACTION OF 100-ML SAMPLES - Proper
conditioning of the solid phase sorbent can have a marked effect on method precision
and accuracy. This section describes the SPE procedure using Waters AC-2 Sep-Pak
or Supelco Supelclean ENVI-Carb Plus cartridges with 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 allowing 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 all the sample has passed
through each SPE cartridge, detach the reservoir and 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 manifold top and insert a rack with
2-mL volumetric collection tubes into the extraction tank to collect the extracts as
they are eluted from the cartridges. (It is not necessary to reverse the ENVI-Carb
Plus cartridge as described in the manufacturer's literature.) Fill each cartridge
with DCM. Pull enough of the solvent into the cartridge at low vacuum to soak
the 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
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through the cartridge 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 1.5 mL, estimated by the volumetric mark on the side of the collection
tube.
11.5.4 Remove collection tubes containing the extracts 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 uL of a 100-ug/mL IS
solution to a 2-mL extract will result in an IS concentration 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 minimum of 0.4 g of dry
anhydrous sodium sulfate. A fritted 3-mL polypropylene column or a 5-8 mm
diameter disposable pipette with a small piece of glass wool may be used. Collect
the extracts from the drying column directly in 2-mL autosampler vials for storage
until analysis.
NOTE: Experiments during method development indicated that this extract
cannot be reliably concentrated by nitrogen evaporation because of the volatility
of the method analyte. Therefore, extract concentration to enhance sensitivity is
not permitted.
11.6 Analyze an aliquot of the sample extract prepared 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 data acquisition, use the
same software that was used in the calibration procedure to identify peaks in
predetermined retention time windows of interest. Use the data system software to
examine the ion abundances of components of the chromatogram. Identify a sample
component by comparison of its SIM (or full scan) mass spectrum to a SIM (or full
scan) reference spectrum in the user-created database. The GC retention time of a
method analyte should be within one to two sec of the retention time observed for that
same compound in the most recently analyzed CCC standard. Ideally, the width of the
retention time window should be based upon measurements 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 suggested 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 SEVI mode, verification of
retention times is particularly important because less mass spectral information is
being collected.
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12.2 IDENTIFICATION VERIFICATION USING ION RATIOS - When the QI of
1,4-dioxane (m/z 88) is observed at the correct retention time, verify that it is truly
present by verifying that the ratio of the confirmation 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 areas for the QI
and confirmation ion from their respective mass chromatograms. Using relative
abundances obtained directly from the mass spectrum, whether or not it has undergone
background subtraction, is not acceptable. Variations in system software and analyst
subjectivity in selecting background spectra for subtraction can affect the validity of
the ratio calculation when the relative abundance from the spectrum is used. Using a
raw spectrum (not corrected for background) can also affect the validity of the ratio
calculation.
Use similar procedures for identification of the IS 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 quantitate 1,4-dioxane or the SUR in
samples. The integrated abundances of the QIs of the analyte, SUR and IS should be
used for all calculations. Adjust the final analyte 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 result 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, and the diluted extract injected.
Acceptable SUR performance (Sect. 9.3.6.1) should be determined from the undiluted
sample extract. Incorporate the dilution factor into final concentration calculations.
The resulting sample should be documented as a dilution, 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 reported with more than two
significant figures. This is done to better illustrate the method performance data.
13. METHOD PERFORMANCE
13.1 Method performance data presented in Section 17 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.
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13.2 PRECISION, ACCURACY, AND MINIMUM REPORTING LEVELS - Single
laboratory DLs and LCMRLs are presented in Table 3. Single laboratory accuracy
and precision data from both fortified reagent water and fortified drinking water
matrices are presented in Tables 4 and 5, respectively. Two of the matrices tested
were selected specifically as potentially difficult matrices because of either their
relatively high TOC or high mineral content (hardness). 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 CONCENTRATIONS OF
1,1,1-TRICHLORETHANE - Because of its widespread use as a chlorinated solvent
stabilizer, 1,4-dioxane may be found in the presence of high concentrations of
1,1,1-trichloroethane. The method was tested in a high TOC water matrix with up to
500 ug/L of 1,1,1-trichloroethane added as a co-contaminant. No adverse affect was
observed, and the method performed well within QC limits (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 preserved 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 beyond 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 performance of this method
was demonstrated in two additional laboratories, with 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 in 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 the USEPA Region 10 Laboratory,
Port Orchard, WA.
14. POLLUTION PREVENTION
14.1 This method utilizes SPE to extract the analyte from water. It requires the use of very
small volumes of organic solvent and very small quantities of pure analyte, thereby
minimizing the potential hazards to both the analyst and the environment as compared
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to the use of large volumes of organic solvents in conventional liquid-liquid
extractions.
14.2 For information about pollution prevention that may be applicable to laboratory
operations, consult "Less is Better: Laboratory Chemical Management for Waste
Reduction" available from the American Chemical Society'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 method generate relatively small amounts
of waste since only small amounts of reagents and solvents are used. The matrices of
concern are finished drinking water or source water. Waste management practices
must be conducted consistent with all applicable rules and regulations, and
laboratories must protect the air, water, and land by minimizing and controlling all
releases from fume hoods and bench operations. Compliance is required with any
sewage discharge permits and regulations, particularly 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, EJ. and R.A. Krop, Statistical Procedures for Determination and Verification 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 ofHydrophilic 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 Extraction GC/MS/MS. Environ. Sci.
Technol.. 40, (2006) 7305-7311.
5. USEPA, 2006 Edition of the Drinking Water Standards and Health Advisories. APA #822-R-
06-013.
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.
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7. OSHA Safety and Health Standards, General Industry. (29CFR1910), Occupational Safety
and Health Administration, OSHA 2206, (Revised, July 1, 2001).
8. Safety in Academic Chemistry Laboratories. American Chemical Society Publication,
Committee on Chemical Safety, 7th Edition. Information on obtaining a copy is available at
http://membership.acs.org/C/CCS/pub_3.htm. (accessed September 2008). Also available by
request at OSS@acs.org
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17.TABLES, DIAGRAMS, FLOWCHARTS AND DEMONSTRATION DATA
Table 1. Bromofluorobenzene (BFB) Tune Verification Criteria
Mass (m/z)
50
75
95
96
173
174
175
176
177
Relative Abundance Criteria
15-40% of mass 95
3 0-80% of mass 95
Base peak, 100% relative abundance
5-9% of mass 95
<2%ofmass 174
>50%ofmass95
5-9% of mass 174
>95% but <101% of mass 174
5-9% of mass 176
Table 2. Retention Times and Quantitation Ions (QIs)
Compound
1,4-dioxane
l,4-dioxane-J8(SUR)
THF-J8 (IS)
Retention Time (min)
8.85
8.77
6.68
SIM Ions (m/z)
58a, 88
62, 64, 96
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 libraries. If the instrument has been
calibrated and passes bromofluorobenzene (BFB) criteria, then m/z 57 may be used as the
confirmation ion on ion trap instruments.
Table 3. Lowest Concentration Minimum Reporting Level (LCMRL) and Detection
Limit (DL) Calculated for Each Extraction Option
Compound/Extraction Option
1,4-dioxane (500 ml w/2-g Coconut charcoal)
1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridge)
LCMRL
(HS/L)
0.047
0.036
DL (ug/L)
0.026a
0.0206
a. Calculated from replicates fortified at 0.040 ug/L, n=7.
b. Calculated from replicates fortified at 0.030 ug/L, n=8.
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Table 4. Demonstration of Method Performance in Reagent Water Fortified with
1,4-Dioxane at Three Concentrations
Compound/Extraction Option
1,4-dioxane (500 ml w/2-g Coconut charcoal)
l,4-dioxane-J8 (SUR) (500 ml w/2-g Coconut charcoal)
1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridge)
l,4-dioxane-J8(SUR) (100 ml w/Waters AC-2 Sep-Pak
cartridge)
1,4-dioxane (500 ml w/2-g Coconut charcoal)
l,4-dioxane-J8 (SUR) (500 ml w/2-g Coconut charcoal)
1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridge)
l,4-dioxane-6?8 (SUR) (100 ml w/Waters AC-2 Sep-Pak
cartridge)
1,4-dioxane (500 ml w/2-g Coconut charcoal)
l,4-dioxane-J8 (SUR) (500 ml w/2-g Coconut charcoal)
1,4-dioxane (100 ml w/Waters AC-2 Sep-Pak cartridge)
l,4-dioxane-6?8 (SUR) (100 ml w/Waters AC-2 Sep-Pak
cartridge)
Reagent Water Fortified at
0.030 or 0.040 ug/L
(n=7 or 8) a
Mean %
recovery
110
92
110
102
RSD (%)
19
3.5
20
3.8
Reagent Water Fortified at
1.0 ug/L (n=6)
Mean %
recovery
98.0
97.1
101
105
RSD (%)
6.2
5.2
4.2
4.8
Reagent Water Fortified at
10.0 ng/L (n=7)
Mean %
recovery
93.9
90.1
95.2
99.3
RSD (%)
2.8
2.8
2.9
3.0
a. Samples (500 mL) extracted on 2-g Coconut charcoal cartridges were fortified at 0.040 ug/L,
n=7. Samples (100 mL) extracted on Waters AC-2 Sep-Pak cartridges were fortified at 0.030
ug/L, n=8.
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Table 5. Demonstration of Method Performance in Drinking Water Matrices Using Each
of the Solid Phase Extraction (SPE) Options; Matrix Samples Fortified at 1.0
ug/L (n=7 for each matrix)
Compound/Extraction Option
1,4-dioxane (500 ml w/2-g Coconut charcoal)
l,4-dioxane-J8 (SUR) (500 ml w/2-g Coconut charcoal)
1,4-dioxane (100 ml w/Waters AC -2 Sep-Pak cartridge)
1,4-dioxane-dg (SUR) (100 ml w/Waters AC -2 Sep-Pak
cartridge)
1,4-dioxane (500 ml w/2-g Coconut charcoal)
l,4-dioxane-J8 (SUR) (500 ml w/2-g Coconut charcoal)
1,4-dioxane (100 ml w/Waters AC -2 Sep-Pak cartridge)
1,4-dioxane-dg (SUR) (100 ml w/Waters AC -2 Sep-Pak
cartridge)
1,4-dioxane (500 ml w/2-g Coconut charcoal)
l,4-dioxane-J8 (SUR) (500 ml w/2-g Coconut charcoal)
1,4-dioxane (100 ml w/Waters AC -2 Sep-Pak cartridge)
1,4-dioxane-dg (SUR) (100 ml w/Waters AC -2 Sep-Pak
cartridge)
Surface Water
Mean %
recovery
99.0a
100
97.0b
98.5
RSD (%)
4.9
2.5
4.6
2.5
Surface Water (high in
TOC)C
Mean %
recovery
102
99.8
98.5
101
RSD (%)
3.5
2.4
5.6
4.2
Groundwater (high in
mineral content) d
Mean %
recovery
95. 9e
98.2
1011
104
RSD (%)
2.1
2.5
3.3
5.9
a. Percent recovery after correction for matrix background of 0.66 ug/L.
b. Percent recovery after correction for matrix background of 0.42 ug/L.
Note: Groundwater used for these Laboratory Fortified Blanks (LFBs) was collected from the
same source as the 500 mL LFBs using coconut charcoal, but was collected on different days,
thus the difference in matrix background concentration.
c. TOC measured at 4.950 mg/L.
d. Hardness measured at 289 mg/L as calcium carbonate.
e. Percent recovery after correction for matrix background of 0.070 ug/L.
f. Percent recovery after correction for matrix background of 0.080 ug/L.
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Table 6. Initial Demonstration of Capability (IDC) and Quality Control (QC) Requirements (Summary)
Method
Reference
Sect. 9.2.1
Sect. 9.2.2
Sect. 9.2.3
Sect. 9.2.4
Sect. 9.2.5
& 9.3.9
Requirement
Initial Demonstration of
Low Background
Initial Demonstration of
Precision (IDP)
Initial Demonstration of
Accuracy (IDA)
Minimum Reporting
Limit (MRL)
Confirmation
Calibration Confirmation,
Quality Control Sample
(QCS)
Specification and Frequency
Analyze LRB prior to any other IDC steps. When a new
lot of SPE media is obtained, verify that background is
at acceptable limits.
Analyze 4-7 replicate LFBs fortified near the midrange
calibration concentration.
Calculate average recovery for replicates used in IDP.
Fortify, extract and analyze 7 replicates at the proposed
MRL concentration. Calculate the mean, standard
deviation and HRpiR. Confirm that the upper and lower
limits for the Prediction Interval of Result (Upper PIR,
and Lower PIR, Sect. 9.2.4.2) meet the recovery criteria.
Analyze a standard from a second source (QCS) to
verify the initial calibration curve.
Acceptance Criteria
Demonstrate that the method analyte is < 1/3 the
MRL, and that possible interferences from
extraction media do not prevent the identification
and/or quantification of the method analyte, SUR
or IS.
Note: This includes the absence of interferences at
both the QIs and confirmation ions at the RTs of
interest.
%RSDmustbe<20%
Mean recovery + 20% of true value
Upper PIR < 150%
Lower PIR > 50%
± 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 been
abbreviated to fit the table format, there may be issues that need additional clarification, or areas where important additional information from the method text
is needed. In all cases, the full text of the QC in Section 9 supersedes any missing or conflicting information in this table.
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Table 7. Ongoing Quality Control (QC) Requirements (Summary)
Method
Reference
Requirement
Specification and Frequency
Acceptance Criteria
Sect. 8.3
Sample Holding Time
28 days with appropriate preservation and storage as
described in Sections 8.1-8.3.
Sample results are valid only if samples are
extracted within sample hold time.
Sect. 8.4
Extract Holding Time
28 days stored at -5 °C and protected from light
Sample results are valid only if extracts are
analyzed within extract hold time.
Sect. 9.3.1
Laboratory Reagent Blank
(LRB)
One LRB with each extraction batch of up to 20 Field
Samples.
Demonstrate that the method analyte concentration
is < V3 the MRL, and confirm that possible
interferences do not prevent quantification. If the
background concentration exceeds V3 the MRL,
results for the extraction batch are invalid.
Sect. 9.3.3
Laboratory Fortified
Blank (LFB)
One LFB is required for each extraction batch of up to
20 Field Samples. Rotate the fortified concentrations
between low, medium, and high amounts.
Results of LFB analyses at medium and high
fortifications must be 70-130% of the true value for
the analyte and SUR. Results of the low-level LFB
must be 50-150% of the true value.
Sect. 9.3.5
Internal Standard (IS)
Compare IS area to the average IS area in the initial
calibration and the most recent CCC.
Peak area counts for all injections must be within
+ 50% of the average peak area calculated during
the initial calibration and + 30% from the most
recent CCC. If the IS does not meet this criterion,
target analyte results are invalid. Consult Sect.
9.3.5 for further information.
Sect. 9.3.6
Surrogate(SUR)
Standards
The SUR standard added to all calibration standards and
samples, including QC samples. Calculate SUR
recoveries.
SUR recovery must be 70-130% of the true value.
If a SUR fails this criterion, report all results for
sample as suspect/SUR recovery.
Sect. 9.3.7
Laboratory Fortified
Sample Matrix (LFSM)
Analyze one LFSM per extraction batch (of up to 20
Field Samples) fortified with the method analyte at a
concentration close to but greater than the native
concentration. Calculate LFSM recoveries.
See Sect. 9.3.7.3 for instructions on the
interpretation of LFSM results.
522-38
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Table 7. Ongoing Quality Control (QC) Requirements (Summary) (Continued)
Sect. 9.3.8
Laboratory Fortified
Sample Matrix Duplicate
(LFSMD) or Field
Duplicates (FD)
Extract and analyze at least one FD or LFSMD with
each extraction batch of up to 20 Field Samples. A
LFSMD may be substituted for a FD when the
frequency of detects for 1,4-dioxane are low. Calculate
RPDs.
Method analyte RPDs for the LFSMD or FD should
be < 30% at mid and high levels of fortification and
< 50% near the MRL. Failure to meet this criterion
may indicate a matrix effect.
Sect. 9.3.9
Quality Control Sample
(QCS)
Analyze QCS during the IDC, each time CAL solutions
are prepared. A QCS must be analyzed at least
quarterly.
Results must be 80-120% of the expected value.
Sect. 10.2
Initial Calibration
Use IS calibration technique to generate a linear or
quadratic calibration curve. The number of standards
required is determined by the calibration range (Sect.
7.2.2). Check the calibration curve as described in
Section 10.2.4.
When each calibration standard is calculated as an
unknown using the calibration curve, the result
should be 80-120% of the true value for all except
the lowest standard, which should be 60-140% of
the true value. If this criterion is not met, reanalyze
CALs, select a different method of calibration or
recalibrate over a shorter range.
Sects. 10.1
and 10.2.1
MS Tune Check
Analyze BFB to verify MS tune each time the
instrument is calibrated.
Criteria are given in Table 1.
Sect. 10.3
Continuing Calibration
Check (CCC)
Verify initial calibration by analyzing a calibration
standard at the beginning of each analysis batch prior to
analyzing samples, after every 10 samples, and after the
last sample. The first CCC daily must be at or below the
MRL. Subsequent CCCs alternate between medium and
high concentrations.
Low CCC - at or below the MRL concentration
Mid CCC - near midpoint in initial calibration curve
High CCC - near the highest calibration standard.
Low: + 50% of true value
Mid: +30% of true value
High: +30% of true value
Note: Table 7 is intended as an abbreviated summary of QC requirements provided as a convenience to the method user. Because the information has been
abbreviated to fit the table format, there may be issues that need additional clarification, or areas where important additional information from the method text
is needed. In all cases, the full text of Sections 8-10 in the method supersedes any missing or conflicting information in this table.
522-39
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RT: 5.84-9.32
100000-
50000-
—
c
0-
m/z88
1,4-dioxane
8.864
150000-
100000r
50000-
I
m/z96
1,4-diox-d8
8.786
200000^
150000!
100000!
50000|
6.
m/z 46 THF-d8 ^J
6.722
Jy
845*
6.722
300000-E
200000!
100000!
ru
UJMR* 8-786
ft A ^ 8.864
I II /111
J \J L ~A~ _ „ rJ " V „
6.0 6.5 7.0 7.5 8.0
Time(min)
8.5
9.0
Figure 1. Reconstructed total ion current chromatogram and mass chromatograms for THF-J8 (IS),
l,4-dioxane-J8 (SUR), and 1,4-dioxane at 0.5 ug/mL each (the standard is equivalent to an extract of
a 10 jig/L aqueous sample). * Peak at 6.845 min is chloroform, a chemical present in DCM.
522-40
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Stability of 1,4-Dioxane in Drinking Water
120.0%
100.0%
80.0%
§ 60.0% H
a:
40.0%
20.0%
0.0%
99.2%
95.3%
103.2%
f
99.4%
n
98.9%
14
days
21
28
Figure 2. Stability of 1,4-dioxane in preserved drinking 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 ug/L 1,4-dioxane.
Matrix blank data were used to correct for native analyte concentrations.
120.0% -,
100.0% -
. 80.0% -
2"
0
8 60.0% -
cc
S.O
° 40.0% -
20.0%
0.0% -
Stability of 1 ,4-Dioxane in Extracts
93.9%
92.0%
91.2%
0 14 28
days
Figure 3. Stability of 1,4-dioxane in sample extracts stored at -5°C, in the dark, over a 42-day time
period. Replicate samples (n = 7) were fortified to a concentration of 10 jig/L 1,4-dioxane.
522-41
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