Method 541: Determination of 1-Butanol, 1,4-Dioxane, 

2-Methoxyethanol and 2-Propen-1-ol in Drinking Water 

by Solid Phase Extraction and Gas Chromatography/Mass 

Spectrometry
i

Questions concerning this document should be addressed to:

Steven C. Wendelken, PhD

U.S. EPA, Office of Ground Water and Drinking Water, Standards and Risk Management Division, 

Technical Support Center, 26 W. Martin Luther King Dr. Cincinnati, OH 45268

Phone: (513) 569-7491

wendelken.steve@epa.gov

Office of Water (MS-140) 

EPA 815-R-15-011

EPA contract EP-C-12-013 

November, 2015

Acknowledgements

Don Shelly and Xiaoyan Wang, Ph.D., UCT, Inc. (Bristol, PA)

Michael S. Young, Ph.D., Mark Capparella, and Jeremy Shia, Waters Corporation (Milford, MA)

Paul Grimmett, U.S. EPA Office of Research and Development (Cincinnati, OH)
ii

Table of Contents

1 Scope and application...........................................................................................................................1

1.1 Analyte List....................................................................................................................................1

1.2 Supporting Data ............................................................................................................................1

1.3 Method Flexibility .........................................................................................................................1

2 Summary of the Method.......................................................................................................................1

3 Definitions.............................................................................................................................................2

3.1 Analysis Batch ...............................................................................................................................2

3.2 Calibration Standard .....................................................................................................................2

3.3 Continuing Calibration Check (CCC)..............................................................................................2

3.4 Extraction Batch............................................................................................................................2

3.5 Field Duplicates (FD) .....................................................................................................................2

3.6 Internal Standard (IS)....................................................................................................................2

3.7 Laboratory Fortified Blank (LFB) ...................................................................................................2

3.8 Laboratory Fortified Sample Matrix (LFSM)..................................................................................2

3.9 Laboratory Fortified Sample Matrix Duplicate (LFSMD)...............................................................3

3.10 Laboratory Reagent Blank (LRB) ...................................................................................................3

3.11 Lowest Concentration Minimum Reporting Level (LCMRL)..........................................................3

3.12 Minimum Reporting Level (MRL)..................................................................................................3

3.13 Primary Dilution Standard (PDS)...................................................................................................3

3.14 Quality Control Sample (QCS).......................................................................................................3

3.15 Reagent Water..............................................................................................................................3

3.16 Safety Data Sheets........................................................................................................................3

3.17 Selected Ion Monitoring (SIM)......................................................................................................3

3.18 Stock Standard Solution................................................................................................................3

3.19 Surrogate Analyte .........................................................................................................................4

4 Interferences.........................................................................................................................................4

4.1 Glassware, Reagents and Equipment ...........................................................................................4

4.2 Matrix Interferences.....................................................................................................................4

4.3 Extraction Cartridges.....................................................................................................................4

4.4 Matrix Effects in the Presence of Water.......................................................................................4

4.4.1 Nitrogen-drying Manifold .....................................................................................................4

4.4.2 Optimizing the Cartridge Drying Step ...................................................................................5
iii

4.5 Analyte Extraction Efficiency ........................................................................................................5

4.6 Extraction Flow Rate .....................................................................................................................5

4.7 QC Compounds .............................................................................................................................5

5 Safety ....................................................................................................................................................5

5.1 Chemicals......................................................................................................................................5

5.2 Sodium Bisulfate ...........................................................................................................................5

5.3 Dichloromethane ..........................................................................................................................5

6 Equipment and Supplies .......................................................................................................................5

6.1 Sample Containers........................................................................................................................5

6.2 Vials...............................................................................................................................................6

6.3 Micro Syringes...............................................................................................................................6

6.4 Volumetric Pipettes ......................................................................................................................6

6.5 Analytical Balance .........................................................................................................................6

6.6 Compressed Gas: Helium..............................................................................................................6

6.7 Compressed Gas: Nitrogen ...........................................................................................................6

6.8 Compressed Gas: Air.....................................................................................................................6

6.9 Disposable Pasteur Pipettes .........................................................................................................6

6.10 Volumetric Flasks..........................................................................................................................6

6.11 Solid Phase Extraction Apparatus for Cartridges..........................................................................6

6.11.1 UCT EU-541 SPE Cartridge.....................................................................................................6

6.11.2 Waters AC-2 SPE Cartridge....................................................................................................6

6.11.3 Vacuum Extraction Manifold ................................................................................................6

6.11.4 Sample Delivery System........................................................................................................7

6.11.5 Extract Collection Tubes........................................................................................................7

6.12 Laboratory Vacuum System..........................................................................................................7

6.13 Drying Manifold for SPE Cartridges...............................................................................................7

6.14 Flow Meter for Drying Manifold ...................................................................................................7

6.15 Gas Chromatograph/Mass Spectrometer (GC/MS)......................................................................7

6.15.1 Column..................................................................................................................................7

6.15.2 GC Inlet..................................................................................................................................7

6.15.3 Inlet Liner for Split/Splitless Inlet..........................................................................................7

6.15.4 GC/MS Interface....................................................................................................................7

6.15.5 Mass Spectrometer (MS) ......................................................................................................7
iv

6.15.6 Data System ..........................................................................................................................8

7 Reagents and Standards .......................................................................................................................8

7.1 Methanol.......................................................................................................................................8

7.2 Dichloromethane ..........................................................................................................................8

7.3 Sodium Sulfate, Anhydrous...........................................................................................................8

7.4 Sample Preservation Reagents .....................................................................................................8

7.4.1 Sodium Sulfite .......................................................................................................................8

7.4.2 Sodium Bisulfate ...................................................................................................................8

7.5 Stock Standard Solutions..............................................................................................................8

7.5.1 Internal Standard Stocks.......................................................................................................8

7.5.2 Surrogate Analyte Stock Standards.......................................................................................8

7.5.3 Method Analyte Stock Standard Solutions...........................................................................9

7.5.4 Preparation Instructions for Analytes Obtained as Neat Compounds .................................9

7.5.5 Storage of Stock Standards...................................................................................................9

7.6 Primary Dilution Standards (PDS) .................................................................................................9

7.6.1 Internal Standard Primary Dilution Standard .......................................................................9

7.6.2 Surrogate Analyte Primary Dilution Standard.......................................................................9

7.6.3 Method Analyte Primary Dilution Standard .........................................................................9

7.7 Calibration Standards..................................................................................................................10

7.7.1 Example Calibration Scheme ..............................................................................................10

7.7.2 Dilution Scheme for Calibration Standards.........................................................................10

7.7.3 Storage of Calibration Standards........................................................................................11

7.7.4 GC/MS Tune Check Solution ...............................................................................................11

8 Sample Collection, Preservation, and Storage....................................................................................11

8.1 Sample Bottles............................................................................................................................11

8.2 Sample Collection .......................................................................................................................11

8.3 QC Samples.................................................................................................................................11

8.4 Sample Shipment and Storage....................................................................................................11

8.5 Verification upon Receipt ...........................................................................................................11

8.6 Sample Holding Time ..................................................................................................................11

8.7 Storage of Extracts......................................................................................................................11

8.8 Extract Holding Time...................................................................................................................11

9 Quality Control....................................................................................................................................12
v

9.1 Optimizing SPE Cartridge Drying Parameters.............................................................................12

9.1.1 Prepare for the Test............................................................................................................12

9.1.2 Condition SPE Test Cartridges.............................................................................................12

9.1.3 Dry the Cartridges...............................................................................................................12

9.1.4 Flow Rate and Volumes used during Method Development..............................................12

9.1.5 Elute the Test Cartridges.....................................................................................................13

9.1.6 Estimate the Minimum Required Nitrogen Volume ...........................................................13

9.1.7 Analyze and Evaluate the Extracts......................................................................................13

9.1.8 Select a Volume above the Minimum.................................................................................13

9.2 Initial Demonstration of Capability (IDC)....................................................................................13

9.2.1 Demonstration of Low System Background........................................................................13

9.2.2 Demonstration of Precision ................................................................................................13

9.2.3 Demonstration of Accuracy ................................................................................................14

9.2.4 Minimum Reporting Level (MRL) Confirmation..................................................................14

9.2.5 Quality Control Sample (QCS) .............................................................................................14

9.3 Ongoing QC Requirements .........................................................................................................15

9.3.1 Laboratory Reagent Blank (LRB) .........................................................................................15

9.3.2 Continuing Calibration Check (CCC)....................................................................................15

9.3.3 Laboratory Fortified Blank ..................................................................................................15

9.3.4 BFB MS Tune Check.............................................................................................................15

9.3.5 Internal Standards (IS).........................................................................................................16

9.3.6 Surrogate Recovery.............................................................................................................16

9.3.7 Laboratory Fortified Sample Matrix (LFSM)........................................................................16

9.3.8 Field Duplicate or Laboratory Fortified Sample Matrix Duplicate (FD or LFSMD)..............17

9.3.9 Retention Time Shifts..........................................................................................................18

9.3.10 Quality Control Sample (QCS) .............................................................................................18

9.4 Method Modification QC Requirements ....................................................................................18

9.4.1 Repeat the IDC ....................................................................................................................18

9.4.2 Document Performance in Representative Sample Matrixes ............................................18

9.4.3 Monitor Performance of the Modified Method .................................................................19

10 Calibration and Standardization .....................................................................................................19

10.1 GC/MS Optimization ...................................................................................................................19

10.1.1 MS Tune and MS Tune Check..............................................................................................19
vi

10.1.2 GC Conditions......................................................................................................................19

10.1.3 SIM MS Conditions..............................................................................................................20

10.1.4 Suggested Ions and Dwell Times.........................................................................................20

10.2 Initial Calibration.........................................................................................................................20

10.2.1 Calibration Standards..........................................................................................................20

10.2.2 Calibration Curve.................................................................................................................20

10.2.3 Calibration Acceptance Criteria ..........................................................................................20

10.3 Continuing Calibration Checks (CCCs).........................................................................................21

10.3.1 Internal Standard Responses..............................................................................................21

10.3.2 Surrogate Analytes..............................................................................................................21

10.3.3 Method Analytes.................................................................................................................21

10.4 Corrective Action ........................................................................................................................21

11 Procedure........................................................................................................................................21

11.1 Sample Preparation ....................................................................................................................21

11.1.1 QC Samples .........................................................................................................................22

11.1.2 Surrogate Analytes..............................................................................................................22

11.2 Extraction Procedure Using Waters AC-2 SPE Format................................................................22

11.2.1 Set up the Extraction Manifold...........................................................................................22

11.2.2 Cartridge Cleaning...............................................................................................................22

11.2.3 Cartridge Conditioning........................................................................................................22

11.2.4 Sample Loading...................................................................................................................22

11.2.5 Cartridge Drying ..................................................................................................................22

11.3 Extraction Procedure using UCT EU-541 SPE Format .................................................................23

11.3.1 Set Up the Extraction Manifold...........................................................................................23

11.3.2 Cartridge Cleaning...............................................................................................................23

11.3.3 Cartridge Conditioning........................................................................................................23

11.3.4 Sample Loading...................................................................................................................23

11.3.5 Cartridge Drying ..................................................................................................................23

11.4 Cartridge Elution .........................................................................................................................24

11.5 Internal Standard Addition .........................................................................................................24

11.6 Extract Drying..............................................................................................................................24

11.7 Analysis of Sample Extracts.........................................................................................................24

11.8 The Analysis Batch ......................................................................................................................24
vii

11.8.1 Initial CCC ............................................................................................................................25

11.8.2 Field and QC Samples..........................................................................................................25

11.8.3 CCC Frequency ....................................................................................................................25

11.8.4 Final CCC..............................................................................................................................25

11.8.5 Initial Calibration Frequency ...............................................................................................25

12 Data Analysis and Calculations .......................................................................................................25

12.1 Establish Retention Time Windows............................................................................................25

12.2 Identify Analytes by Retention Time...........................................................................................25

12.3 Confirm Analyte Identifications..................................................................................................25

12.4 Compound Quantitation.............................................................................................................26

12.5 Data Review ................................................................................................................................26

12.6 Exceeding the Calibration Range ................................................................................................26

13 Method Performance......................................................................................................................26

13.1 Precision, Accuracy, and LCMRL Results.....................................................................................26

13.2 Analyte Stability Study ................................................................................................................26

13.3 Extract Storage Stability..............................................................................................................27

14 Pollution Prevention .......................................................................................................................27

15 Waste Management .......................................................................................................................27

16 References ......................................................................................................................................27

17 Tables, Figures, and Method performance Data ............................................................................28

Table 1. 4-Bromofluorobenzene (BFB) Mass Intensity Criteria........................................................28

Table 2. Gas Chromatography/Mass Spectrometry (GC/MS) Conditions........................................28

Table 3. Retention Times, Quantitation Ions, and Internal Standard Assignmentsa ........................29

Table 4. LCMRL Results for the Waters AC-2 SPE Format ................................................................29

Table 5. Precision and Accuracy Data for Reagent Water: Waters AC-2 SPE Format ......................29

Table 6. Precision and Accuracy Data for Ground Water: Waters AC-2 SPE Format .......................30

Table 7. Precision and Accuracy Data for Surface Water: Waters AC-2 SPE Format........................30

Table 8. LCMRL Results for the UCT EU-541 SPE Format .................................................................30

Table 9. Precision and Accuracy Data for Reagent Water: UCT EU-541 SPE Format .......................31

Table 10. Precision and Accuracy Data for Ground Water: UCT EU-541 SPE Format ........................31

Table 11. Precision and Accuracy Data for Surface Water: UCT EU-541 SPE Format.........................32

Table 12. Aqueous Sample Holding Time Data (n=4) .........................................................................33

Table 13. Holding Time Data for Sample Extracts (n=4).....................................................................33
viii

Table 14. Initial Demonstration of Capability (IDC) Quality Control Requirements...........................34

Table 15. Ongoing Quality Control Requirements..............................................................................34

Figure 1. Drying apparatus and proper placement of rotameter in flow path..................................36

Figure 2. Reconstructed ion chromatogram (RIC), SIM mode, for calibration standard...................37

Figure 3. Extracted ion current profiles for calibration standard; concentrations as listed..............38

Figure 4. RIC, SIM mode, for unfortified drinking water from a surface water source .....................39

Figure 5. RIC, SIM mode, for unfortified drinking water from a ground water source .....................40
1

1 Scope and application

Method 541 is a gas chromatography (GC) method for the determination of 1-butanol, 1,4-dioxane, 

2-methoxyethanol, and 2-propen-1-ol in finished drinking water. Method 541 requires detection using 

mass spectrometry (MS) in selected ion monitoring (SIM) to provide selectivity for the method analytes. 

This method is intended for use by analysts skilled in the performance of solid phase extractions, the 

operation of GC/MS instrumentation and in the interpretation of the associated data.

1.1 Analyte List

Analyte Chemical Abstracts Services 

Registry Number (CASRN)

1-butanol 71-36-3

1,4-dioxane 123-91-1

2-methoxyethanol 109-86-4

2-propen-1-ol (allyl alcohol) 107-18-6

1.2 Supporting Data

Precision and accuracy data have been generated for the detection of the method analytes in reagent 

water and finished drinking water from both ground water and surface water sources (Sect. 17, 

Tables 5–7 and Sect. 17, Tables 9–11). Single-laboratory Lowest Concentration Minimum Reporting 

Levels (LCMRL) (Sect. 3.11) for the analytes in this method are presented in Section 17, Table 4 and 

Table 8. Laboratories using this method are not required to determine LCMRLs, but they must 

demonstrate that the Minimum Reporting Level (MRL) (Sect. 3.12) for each analyte meets the 

requirements described in Section 9.2.4.

1.3 Method Flexibility

The laboratory is permitted to select GC columns, inlets, and GC conditions different from those utilized 

to develop the method. However, the basic chromatographic elements of the method must be retained. 

At a minimum, the internal standards and surrogate analytes specified in the method must be used. 

Changes may not be made to sample collection and preservation (Sect. 8), the quality control (QC) 

requirements (Sect. 9), or the extraction procedure (Sect. 11). Method modifications should be 

considered only to improve method performance. 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. 9.3) are met, and verify 

method performance in representative sample matrixes (Sect. 9.4).

2 Summary of the Method

Samples (0.05 L) are collected in amber, glass bottles containing the method preservatives, sodium 

sulfite (dechlorination) and sodium bisulfate (pH adjustment). In the laboratory, two surrogate analytes 

are added. The method and surrogate analytes are isolated from water using solid phase extraction 

(SPE). The SPE cartridges are dried to remove adsorbed water and eluted with 2 mL of 5% methanol in 

dichloromethane. Extracts are analyzed, without further concentration, by GC/MS in the SIM mode of 

detection. The method analytes are identified by comparing the retention times and ion abundance 

ratios to reference retention times and ion abundance ratios obtained from calibration standards 

acquired under identical GC/MS conditions. The concentrations of 1-butanol, 1,4-dioxane, 
2

2-methoxyethanol, and 2-propen-1-ol are calculated using the integrated peak area and the internal 

standard technique.

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 the number of field samples.

3.2 Calibration Standard

A solution of the method analytes, surrogate analytes, and internal standards prepared from the 

Primary Dilution Standards. The calibration standards are used to calibrate the instrument response with 

respect to analyte concentration.

3.3 Continuing Calibration Check (CCC)

A calibration standard that is analyzed periodically to verify the accuracy of the existing calibration.

3.4 Extraction Batch 

A set of up to 20 field samples (not including QC samples) extracted together using the same lot of solid 

phase extraction devices, solvents, surrogate solution, and fortifying solutions.

3.5 Field Duplicates (FD)

Separate samples collected at the same time, shipped and stored under identical conditions. Method 

precision, including the contribution from sample collection procedures, is estimated from the analysis 

of Field Duplicates. Field Duplicates are used to prepare Laboratory Fortified Sample Matrix and 

Laboratory Fortified Sample Matrix Duplicate QC samples. For the purposes of this method, Field 

Duplicates are necessary to conduct repeat analyses if the original field sample is lost, or to conduct 

repeat analyses in the case of QC failures associated with the analysis of the original field sample.

3.6 Internal Standard (IS)

A pure compound that is added to all standard solutions and extracts in a known amount and used to 

measure the relative response of method analytes that are components of the same solution. The IS 

should respond to instrument conditions and sample matrix in a similar manner as the method analytes,

and have no potential to be present in the samples.

3.7 Laboratory Fortified Blank (LFB)

An aliquot of reagent water, containing method preservatives, to which known quantities of the method 

analytes are added. The LFB is used during the IDC to verify method performance for precision and 

accuracy. The LFB is also a required QC element with each Extraction Batch. The results of the LFB verify 

method performance in the absence of sample matrix.

3.8 Laboratory Fortified Sample Matrix (LFSM)

An aliquot of a field sample to which known quantities of the method analytes are added. The purpose 

of the LSFM is to determine whether the sample matrix contributes bias to the analytical results. For this 

method, separate field samples are required for preparing fortified matrix so that sampling error is 

included in the accuracy estimate.
3

3.9 Laboratory Fortified Sample Matrix Duplicate (LFSMD)

A Field Duplicate of the sample used to prepare the LFSM that is fortified and analyzed identically to the 

LFSM. The LFSMD is used instead of the Field Duplicate to assess method precision when the method 

analytes are rarely found at concentrations greater than the MRL.

3.10 Laboratory Reagent Blank (LRB)

An aliquot of reagent water that contains the preservatives and surrogate analytes. An LRB is included in 

each Extraction Batch to determine if the method analytes or other interferences are introduced from 

the laboratory environment, the reagents, glassware, or extraction apparatus.

3.11 Lowest Concentration Minimum Reporting Level (LCMRL)

The single-laboratory LCMRL is the lowest spiking concentration such that the probability of spike 

recovery in the 50% to 150% range is at least 99%.1,2

3.12 Minimum Reporting Level (MRL)

The minimum concentration that can be reported by a laboratory as a quantified value for a method 

analyte following analysis. For each method analyte, this concentration must meet the criteria defined in 

Section 9.2.4 and must be greater than or equal to the concentration of the lowest calibration standard.

3.13 Primary Dilution Standard (PDS)

A solution that contains compounds prepared from stock standards. PDS solutions are diluted to 

prepare calibration standards and sample fortification solutions, and are used to fortify QC samples.

3.14 Quality Control Sample (QCS)

A solution containing the method analytes at a known concentration that is obtained from a source 

external to the laboratory and different from the source of calibration standards. The purpose of the 

QCS is to verify the accuracy of the primary calibration standards.

3.15 Reagent Water

Purified water that does not contain any measurable quantity of the method analytes or interfering 

compounds at, or above, one-third of the MRL.

3.16 Safety Data Sheets

Written information provided by vendors concerning a chemical’s toxicity, health hazards, physical 

properties, fire and reactivity data, storage instructions, spill response procedures, and handling 

precautions.

3.17 Selected Ion Monitoring (SIM)

A GC/MS technique where only one or a few ions are monitored instead of scanning over a selected 

mass range. 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, 

surrogates, and internal standards as they elute from the chromatographic column.

3.18 Stock Standard Solution

A concentrated standard solution that is prepared in the laboratory using assayed reference materials or 

that is purchased from a commercial source with a certificate of analysis.
4

3.19 Surrogate Analyte

A pure compound, chemically similar to the method analytes, that is unlikely to be found in any sample.

The surrogate is added to each sample in a known amount before extraction. Surrogates are quantitated 

using the same procedures as other sample components. Because surrogates are present in every 

sample, they provide a means of assessing method performance for each sample extraction.

4 Interferences

4.1 Glassware, Reagents and Equipment

Method interferences may be caused by contaminants in solvents, reagents (including reagent water), 

sample bottles and caps, and other sample processing hardware. All laboratory reagents and equipment 

must be routinely demonstrated to be free from interferences under the conditions of the analysis. This 

may be accomplished by analyzing LRBs as described in Section 9.3.1.

4.2 Matrix Interferences

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. Matrix components may directly interfere by producing a signal at or near the retention time of 

an analyte peak. Matrix components may also suppress or enhance the signal of the method analytes. 

(Suppression and enhancement effects occur within the GC inlet when co-eluting contaminants 

influence the transmission efficiency of an analyte to the column.) Humic and fulvic material in 

environmental samples may be co-extracted during SPE and can cause enhancement and suppression. 

Total organic carbon (TOC) is an indicator of the humic content of a sample if such information is 

available. The analysis of Laboratory Fortified Sample Matrix provides evidence for the presence (or 

absence) of matrix effects.

4.3 Extraction Cartridges

Solid phase extraction cartridges may be a source of interferences. The analysis of LRBs provides 

important information regarding the presence or absence of such interferences. Each brand and lot of 

SPE devices should be monitored to ensure that contamination does not preclude analyte identification 

and quantitation. It is recommended to keep SPE cartridges sealed while in storage in order to prevent 

contamination of SPE sorbent.

4.4 Matrix Effects in the Presence of Water

During method development studies, matrix enhancement, matrix suppression, and retention time 

shifts were observed when analyzing extracts containing residual water from the extraction procedure. 

These effects are eliminated by drying SPE cartridges prior to solvent elution and by adding a desiccant 

to the organic extract. It is important to follow all of the steps in the extraction procedure (Sect. 11) 

related to water management.

4.4.1 Nitrogen-drying Manifold

A drying manifold designed for SPE cartridges is required for this method. A rotameter or other 

appropriate flow measurement device must be placed in the delivery line to the nitrogen-drying 

manifold to ensure that the volume of gas passing through the SPE cartridges is consistent for each 

Extraction Batch.
5

4.4.2 Optimizing the Cartridge Drying Step

The laboratory is required to optimize the nitrogen volume for each SPE format prior to conducting the 

method (during the IDC). The gas volumes recommended in Section 9.1.4 are good starting parameters. 

The authors verified these values for each extraction format across multiple lots of cartridges.

4.5 Analyte Extraction Efficiency

Overall extraction efficiency for 2-propen-1-ol is lower than the other analytes. Typical recovery for 

2-propen-1-ol can be expected to fall in the 80 to 90% range. Typical recovery for 1-butanol and 

2-methoxyethanol can be expected to fall in the 80 to 100% range. 1,4-Dioxane is routinely recovered 

near 100%.

4.6 Extraction Flow Rate

During method development, the authors observed low analyte recovery for some extractions when the 

flow rate during loading of the SPE cartridges exceeded 10 mL/min. For this reason, a loading rate of 

5 mL/min is recommended for this method.

4.7 QC Compounds

Depending on the source and purity, labeled analogs used as internal standards and surrogates may 

contain a small percentage of the corresponding native analyte. Such a contribution may be significant 

when attempting to determine MRLs.

5 Safety

5.1 Chemicals

Each chemical should be treated as a potential health hazard and exposure to these chemicals should be 

minimized. Each laboratory is responsible for maintaining an awareness of OSHA regulations regarding 

safe handling of chemicals used in this method. A reference file of safety data sheets should be made 

available to all personnel involved in the chemical analysis.

5.2 Sodium Bisulfate

Sodium bisulfate is used as a sample preservative to inhibit microbial growth. Sodium bisulfate is highly 

acidic and should be used with appropriate caution.

5.3 Dichloromethane

The primary hazard when conducting the procedures in this method is exposure to dichloromethane. 

This solvent is a possible human carcinogen, volatilizes readily with vapors heavier than air, and quickly 

permeates many types of common laboratory gloves. Handle this material with appropriate protection 

for the eyes, skin, and respiratory system. Always perform extractions and prepare standard solutions in 

a laboratory fume hood.

6 Equipment and Supplies

References to specific brands and catalog numbers are included as examples only and do not imply 

endorsement of the products. Such reference does not preclude the use of other vendors or suppliers.

6.1 Sample Containers

Amber glass bottles or vials fitted with polytetrafluoroethylene (PTFE) lined screw caps.
6

6.2 Vials

Various sizes of amber glass vials with PTFE-lined screw caps for storing standard solutions. Amber or 

clear glass, 2 mL autosampler vials with PTFE-faced septa.

6.3 Micro Syringes

Suggested sizes include 5, 10, 25, 50, 100, 250 and 1000 microliters.

6.4 Volumetric Pipettes

Class A.

6.5 Analytical Balance

Capable of weighing to the nearest 0.0001 gram.

6.6 Compressed Gas: Helium

Ultra-high-purity; for use as the GC carrier. Alternate carrier gases, such as hydrogen (99.999% or better) 

may be used if the QC criteria in Sect. 9 are met. Instrument manufacturers should be consulted prior to 

any GC carrier gas conversion.

6.7 Compressed Gas: Nitrogen

Ultra-high-purity; for drying SPE cartridges.

6.8 Compressed Gas: Air

Ultra-high-purity; for drying SPE cartridges.

6.9 Disposable Pasteur Pipettes

Five and three-fourths inch borosilicate glass, used to transfer samples to autosampler vials (Fisher Cat. 

No. 13-678-20B or equivalent).

6.10 Volumetric Flasks

Class A, suggested sizes include 2, 5, and 10 mL for preparation of primary dilution standards and 

calibration standards [Pyrex Brand Cat. No. 5640-2 (2 mL), 5640-5 (5 mL), and 5640-10 (10 mL)]. The 

2 mL size is used to receive the sample eluate during the elution step in the extraction procedure. 

6.11 Solid Phase Extraction Apparatus for Cartridges 

6.11.1 UCT EU-541 SPE Cartridge

UCT, Inc., (Bristol, PA) EU-541 activated carbon (Cat. No. EU541163), 600 mg, 3 mL cartridge; requires 

tube adaptor (Supelco Cat. No. 57020-U, UCT Cat. No. AD0000AS, or equivalent) to attach sample 

reservoir to cartridge and to attach cartridge to the drying manifold.

6.11.2 Waters AC-2 SPE Cartridge

Waters Corporation (Milford, MA) AC-2 activated carbon (Cat. No. JJAN20229), 400 mg, reversible 

cartridge; requires 3 mL solvent reservoir (Supelco Cat. No. 57241 or equivalent).

6.11.3 Vacuum Extraction Manifold

Equipped with flow and vacuum control [Supelco Cat. No. 57030-U, UCT Cat. No. VMF016GL (the later 

requires UCT Cat. No. VMF02116 control valves), or equivalent systems]. Automated devices designed 

for use with SPE cartridges may be used; however, all extraction and elution steps must be the same as 

in the manual procedure. Extraction and elution steps may not be changed or omitted to accommodate 

the use of an automated system.
7

6.11.4 Sample Delivery System

Polypropylene sample reservoirs (60 mL Restek Cat. No. 26015, 75 mL UCT Cat. No. RFV0075P, or 

equivalent) which attach to the cartridge, are recommended.

6.11.5 Extract Collection Tubes

Two mL volumetric flasks (Pyrex Brand Cat. No. 5640-2 or equivalent) suitable for collection of eluate 

from the SPE cartridges.

6.12 Laboratory Vacuum System

Sufficient capacity to maintain a vacuum of approximately 20 inches of mercury.

6.13 Drying Manifold for SPE Cartridges

Manifold with flow control valve (Supelco VisidryTM Drying Attachment, Cat. No. 57100-U, or equivalent).

6.14 Flow Meter for Drying Manifold

Rotameter, 0–30 liters/min [Organomation Associates, Inc., (Berlin, MA) Cat. No. NA-1421 or 

equivalent]. Install the rotameter between the gas supply and the drying manifold. See Section 17, 

Figure 1, for additional guidance.

6.15 Gas Chromatograph/Mass Spectrometer (GC/MS)

Analytical system complete with temperature programmable GC suitable for use with capillary columns 

and all required accessories including gas supply, liquid autosampler and data system. Table 3 in 

Section 17 lists retention times observed for method analytes using the column and analytical conditions 

described below.

6.15.1 Column

30 m x 0.25 mm i.d. polyethylene glycol (PEG; commonly called WAX), bonded-phase fused silica 

column, 0.50 μm film thickness. Helium carrier gas: 0.9 mL/min in constant flow mode. Oven 

temperature program: 30 °C (5 min), 10 °C/min to 110 °C (0 min), 25 °C/min to 200 °C (6 min hold).

6.15.2 GC Inlet

Split/splitless injector operated in pulsed splitless mode (200 °C; 10-psig pulse pressure) with a 

30 second split delay. The injection volume was one microliter.

6.15.3 Inlet Liner for Split/Splitless Inlet

Single-gooseneck splitless liner, 4 mm deactivated glass with deactivated glass wool.

6.15.4 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 are acceptable as long as the system has adequate sensitivity and QC 

performance criteria are met.

6.15.5 Mass Spectrometer (MS)

Any type of MS may be used that is capable of SIM or selected ion storage (SIS) mode (i.e., quadrupole 

and ion trap) with electron impact ionization at 70 eV. The instrument must be operated in SIM mode 

(or SIS) for enhanced sensitivity and selectivity. The minimum scan range capability of the MS must be 

m/z 35 to 260, and it must produce a full scan mass spectrum that meets all criteria in Table 1 when a 

solution containing one ng, or less, of bromofluorobenzene (BFB) is injected into the GC/MS.
8

6.15.6 Data System

An interfaced data system is required to acquire, store and output GC/MS data. The computer software 

must have the capability of processing stored data by recognizing a chromatographic peak within a given 

retention time window. The software must be able to construct a linear regression or quadratic 

regression calibration curve and calculate analyte concentrations using the internal standard technique.

7 Reagents and Standards

Reagent grade or better chemicals must be used. Unless otherwise indicated, all reagents must 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 if the reagent is demonstrated to be 

free of analytes and interferences and all requirements of the IDC are met when using these reagents.

7.1 Methanol

CH3OH, CASRN 67-56-1, purge-and-trap-grade (Honeywell, Burdick & Jackson brand, Cat. No. 232 or 

equivalent). No other grades of methanol are permitted for this method.

7.2 Dichloromethane

DCM, CASRN 75-09-02, pesticide residue grade or equivalent. Use DCM to prepare the elution solvent: 

5% methanol in DCM.

7.3 Sodium Sulfate, Anhydrous

Na2SO4, CASRN 7757-82-6, conditioned at 400 °C for at least four hours in a muffle furnace. An “ACS 

grade, suitable for pesticide residue analysis” of granular, 10–60 mesh, anhydrous Na2SO4 is 

recommended (Fisher Scientific Cat. No. S415 or equivalent).

7.4 Sample Preservation Reagents

These preservatives are solids and may be added to the sample bottle before shipment to the field.

7.4.1 Sodium Sulfite

Na2SO3, CASRN 7757-83-7, reduces residual chlorine at the time of sample collection.

7.4.2 Sodium Bisulfate

NaHSO4, CASRN 7681-38-1, reduces sample pH to inhibit microbial growth and prevent analyte 

degradation.

7.5 Stock Standard Solutions

Vendor certified solutions of the method analytes, the internal standards, and the surrogate analytes

are recommended. Users may prepare stock standards starting with the neat liquid if not available as 

certified solutions or sufficient concentration, following the guidance provided in this section. Useful 

concentrations for stock standards are typically in the range of 1000–2000 μg/mL.

7.5.1 Internal Standard Stocks

This method requires two internal standards: 1,4-dioxane-d8 (CASRN 17647-74-4) and chlorobenzene-d5

(CASRN 3114-55-4). Obtain the internal standards as certified mixtures in methanol.

7.5.2 Surrogate Analyte Stock Standards

This method requires two surrogate standards: 1-butanol-d10 (CASRN 34193-38-9) and 2-propen-1-ol-d6

(CASRN 1173018-56-8). Prepare a mixture of 1-butanol-d10 and 2-propen-1-ol-d6 in purge-and-trapgrade methanol. During method development, 1-butanol-d10 was obtained as the neat compound from
9

CDN Isotopes (Pointe-Claire, Quebec, Canada, Cat. No. D-1181). During method development, 

2-propen-1-ol-d6 was obtained as the neat compound from Sigma-Aldrich (Cat. No. 614629).

7.5.3 Method Analyte Stock Standard Solutions

Obtain the analytes listed in Section 1.1 as certified mixes in methanol, or as neat standards if desired.

7.5.4 Preparation Instructions for Analytes Obtained as Neat Compounds

Prepare the stock standards individually at 2000 μg/mL. Using an analytical balance, obtain a tare weight 

for a vial containing 20 mL of purge-and-trap-grade methanol. To achieve 2.0 mg/L nominal 

concentrations, calculate the volume of the liquid analyte corresponding to 40 mg. Measure this volume 

with a 100 μL syringe and inject the entire quantity under the surface of the methanol. Subtract the tare 

weight from the final weight to calculate the exact solution concentration. When a compound’s purity is 

assayed to be 96 percent or greater, the weight can be used without correction to calculate the 

concentration of the stock standard.

7.5.5 Storage of Stock Standards

Experience indicates that the most likely cause of standard deterioration for this method is solvent 

evaporation. After opening sealed ampoules, store commercial mixes in glass vials with Teflon closures 

at –10 °C or lower temperature. Stock standard solutions prepared in-house are estimated to be stable 

for at least one year if stored at –10 °C. Store these stocks in the vials in which they were prepared.

Laboratories should use appropriate QC practices to determine when stock standards need to be 

replaced. Expiration dates of commercially available mixtures provided by the vendor can be used to 

estimate shelf life of stock solutions if evaporation of the solvent is prevented.

7.6 Primary Dilution Standards (PDS)

Prepare Primary Dilution Standards by combining and diluting appropriate volumes of the stock 

standards with purge-and-trap-grade methanol. Store the PDS solutions in glass vials with Teflon-lined 

septa at –10 °C or lower temperature. During method development, PDS solutions were demonstrated 

to be stable for at least one year; however, laboratories should use appropriate QC practices to 

determine when PDS standards need to be replaced. The PDS concentrations appearing in this section 

were used during method development, and are intended to be examples only.

7.6.1 Internal Standard Primary Dilution Standard

Prepare the internal standard PDS at 50 μg/mL in methanol from the internal standard stock. The 

authors added 10 μL to each 2 mL extract and calibration standard to achieve a concentration of 0.25 

μg/mL.

7.6.2 Surrogate Analyte Primary Dilution Standard

Prepare the surrogate standard PDS at 50 μg/mL in methanol from the surrogate standard stock. The 

authors added 10 μL to each 0.050 L sample to achieve a concentration of 10 μg/L.

7.6.3 Method Analyte Primary Dilution Standard

The analyte PDS is used to prepare the calibration standards and to fortify LFB, LFSM and LFSMD QC 

samples with the method analytes. Select nominal analyte concentrations for the PDS such that 

between 5 and 25 μL of the PDS is used to fortify samples and prepare standard solutions. More than 

one PDS concentration may be necessary to meet this requirement. The analyte PDS is prepared by 

combining appropriate volumes of the analyte stock standard solutions in purge-and-trap-grade 

methanol. During method development, three PDS solutions were used. The concentrations of these 

solutions are listed in the table in Section 7.7.2.
10

7.7 Calibration Standards

Prepare a series of calibration standards of at least six levels by diluting the analyte PDS into 5% 

methanol in DCM. The lowest calibration standard must be at, or below, the concentration representing 

the MRL in the aqueous sample for each analyte. Using the internal standard and surrogate PDS 

solutions, add a constant amount of each internal standard and surrogate to each calibration standard. 

The concentration of the surrogate analytes should match the concentration of the surrogates in sample 

extracts, assuming 100% recovery through the extraction process. The calibration standards may also be 

used as CCCs.

7.7.1 Example Calibration Scheme

The dilution scheme for calibration standards used to collect method performance data (Section 13) is 

presented in Section 7.7.2. The right-most column gives the aqueous concentration of method analytes 

achieved by fortifying the same quantity of PDS solution into a 0.050 L aqueous sample, e.g., when 

preparing fortified field samples. Ten microliters of the internal standard PDS (50 μg/mL) were added to 

each calibration standard resulting in a concentration of 0.25 μg/mL. Ten microliters of the surrogate 

PDS (50 μg/mL) were added to each calibration standard resulting in a concentration of 0.25 μg/mL in 

the calibration standard (10 μg/L aqueous sample equivalent).

7.7.2 Dilution Scheme for Calibration Standards

CALa Level Analyte PDS (μg/mL) PDS

Volume 

(μL)

Final Std. Volume

5% methanol:DCM

(mL)

CAL 

Std.c,d

(μg/mL)

Aqueous 

Equivalent

0.050 L Sample

(μg/L)

0.5 x MRL 1,4-dioxane (0.40)

Alcohols, 2-MEa (2.0)

25 2.0 0.0050

0.025

0.20

1.0

Std. #1, MRLb 1,4-dioxane (4.0)

Alcohols, 2-ME (20)

5.0 2.0 0.010

0.050

0.40

2.0

2 1,4-dioxane (4.0)

Alcohols, 2-ME (20)

10 2.0 0.020

0.10

0.80

4.0

3 1,4-dioxane (4.0)

Alcohols, 2-ME (20)

20 2.0 0.040

0.20

1.6

8.0

4 1,4-dioxane (40)

Alcohols, 2-ME (200)

5.0 2.0 0.10

0.50

4.0

20

5 1,4-dioxane (40)

Alcohols, 2-ME (200)

10 2.0 0.20

1.0

8.0

40

6 1,4-dioxane (40) 20 2.0 0.40 16

a. CAL = calibration standard; alcohols = 1-butanol, 2-propen-1-ol; 2-ME = 2-methoxyethanol.

b. During method development, the MRL was confirmed at this level.

c. Ten μL internal standard PDS (50 μg/mL) added to each calibration standard results in a 

concentration of 0.25 μg/mL.

d. Ten μL surrogate PDS (50 μg/mL) added to each calibration standard results in a concentration of 

0.25 μg/mL in the CAL standard (10 μg/L aqueous sample equivalent).
11

7.7.3 Storage of Calibration Standards

The stability of calibration standards was evaluated during method development at concentrations

within the calibration range. The calibration standards are stable for at least 6 months when stored in 

autosampler vials with PTFE-faced silicone septa at –10 °C.

7.7.4 GC/MS Tune Check Solution

BFB, 1 μg/mL, CASRN 460-00-4. Prepare in a solvent mixture identical to the extract solvent 

composition.

8 Sample Collection, Preservation, and Storage

8.1 Sample Bottles

Prior to shipment to the field, add sodium sulfite and sodium bisulfate to each sample bottle: 2.5 mg of 

sodium sulfite and 50 mg of sodium bisulfate. Cap the vials tightly to avoid spillage of the preservation 

reagents. The final concentrations of sodium sulfite and sodium bisulfate in the sample are 50 mg/L and 

1000 mg/L, respectively, for a 50 mL sample. Do not dilute these salts in water. The preservatives must 

be added in the solid form.

8.2 Sample Collection

Open the tap and allow the system to flush for approximately 5 minutes. Using a graduated cylinder, fill 

each bottle with exactly 50 mL of sample. Invert the bottle several times to mix the sample with the 

preservatives. Rinse the graduated cylinder several times with the subsequent sample before filling the 

next bottle.

8.3 QC Samples

Collect additional field samples to fulfill QC requirements for Field Duplicates, LFSMs, and LFSMDs. For 

this method, all QC samples are prepared using duplicate samples collected in the field, i.e., not split 

samples prepared in the laboratory.

8.4 Sample Shipment and Storage

Samples must be chilled during shipment and must not exceed 10 °C during the first 48 hours after 

collection. In the laboratory, samples must be stored at, or below, 6 °C and protected from light.

8.5 Verification upon Receipt

Samples must be confirmed to be at, or below, 10 °C when they are received at the laboratory. When 

samples are returned to the laboratory, use a pH meter to periodically verify that sample pH is less than 

3 for each drinking water source. For each water source, analyze one sample using common assays for 

residual chlorine, e.g., N,N diethyl-p-phenylenediamine (DPD)-colorimetric technique. Residual chlorine 

should not be present in preserved water samples.

8.6 Sample Holding Time

Analyze samples as soon as possible. Samples must be analyzed within 28 days of collection.

8.7 Storage of Extracts

Store the 2 mL extracts obtained from the SPE procedure in a freezer at, or below, –10 °C.

8.8 Extract Holding Time

Extracts must be analyzed within 28 days after sample extraction.
12

9 Quality Control

QC requirements include the IDC and ongoing QC requirements. This section describes each QC 

parameter, its required frequency, and the performance criteria that must be met in order to satisfy EPA 

quality objectives. The QC criteria discussed in the following sections are summarized in Section 17, 

Table 14 and Table 15. These QC requirements are considered the minimum acceptable QC program. 

Laboratories are encouraged to institute additional QC practices to meet their specific needs. Calibrate 

the GC/MS system following the steps in Section 10 prior to optimizing the SPE cartridge drying 

parameters and conducting the IDC.

9.1 Optimizing SPE Cartridge Drying Parameters

For this method, the SPE cartridge drying parameters must be optimized for each extraction format. The 

goal is to produce dry extracts for GC analysis and to conserve compressed gas required by this method. 

The WAX column is very sensitive to water in the extracts and retention time shifts will occur if residual 

water is not completely removed. In addition, the authors observed suppression and enhancement of 

analyte response when residual water was present in the extracts.

9.1.1 Prepare for the Test

Review the extraction procedure in Section 11. Pay particular attention to the steps for drying the AC-2 

cartridges (Sect. 11.2.5) and the UCT EU-541 cartridges (Sect. 11.3.5) after sample loading. Proper drying 

technique results in a clear, single-layer extract after elution: no cloudiness or separate water layer. In 

addition, retention times observed during extract analysis should match those observed for calibration 

standards. Perform the following experiment to identify the optimum volume for nitrogen drying. 

Purified air (zero air) may be used in place of nitrogen; however, vacuum drying is not permitted.

9.1.2 Condition SPE Test Cartridges

Load two SPE cartridges onto the extraction manifold and condition with the following exception: 

aspirate the reagent water in the final conditioning step for ~30 seconds and then close the manifold 

valve. [For the Waters AC-2 format, remove the wet 3 mL reservoirs and replace them with dry 

reservoirs.] Add 150 μL of methanol (Waters AC-2) or 200 μL of methanol (UCT EU-541) to each 

reservoir and aspirate at full vacuum for ~30 seconds.

9.1.3 Dry the Cartridges

Set up the drying manifold, but do not attach it to the extraction lid. Install the rotameter between the 

nitrogen regulator and the control valve on the drying manifold (Figure 1). Place the cartridges on the 

drying manifold in the load direction. Start the nitrogen flow at between 2 and 5 L/min per cartridge 

(total flow measured on the rotameter divided by the number of cartridges); start a timer and dry for 

5 minutes. For the first one to two minutes, water is expelled from the bottom of the cartridges. With 

continued flow, the sorbent visibly lightens in shade. While the cartridges are drying, dry the manifold 

valves used during the conditioning step with methanol followed by vacuum aspiration (Sect. 11.2.5.3). 

Do not omit this step: the valves hold a significant quantity of water.

9.1.4 Flow Rate and Volumes used during Method Development

A rotameter is sensitive to pressure drop across the device and the flow rate observed may not be 

accurate. The authors recorded a true flow rate of 5.0 liters/min per cartridge as measured by a mass 

flow meter when the rotameter indicated a flow rate of 2 L/min (nitrogen delivery pressure of 80 psig). 

For example, when drying five cartridges, the mass flow meter read 25 liters/min while the rotameter 

read 10 liters/min. As measured with a mass flow meter, the optimized nitrogen volumes were as 
13

follows: Waters AC-2 (5 L/min x 5 minutes = 25 liters per sample) and UCT EU-541 (5 L/min x 8 minutes = 

40 liters per sample. Because the rotameter is used to repeat the total flow optimized in these steps, 

accuracy is not required.

9.1.5 Elute the Test Cartridges

Replace the cartridges on the manifold in their original positions and elute with 2 mL of 5% methanol in 

DCM following the procedure in Sect. 11.4. The extracts should be clear without a discernible water 

layer. If the extracts are wet, repeat the experiment and incrementally increase the nitrogen flow or 

time until a volume is reached that results in a clear, single-layer extract. Save these extracts for 

Step 9.1.7.

9.1.6 Estimate the Minimum Required Nitrogen Volume

If the extracts contain no visible water after the first trial, repeat the experiment and incrementally 

decrease the nitrogen volume. Determine the minimum volume of nitrogen that results in single-layer 

extracts. Save these extracts for Step 9.1.7.

9.1.7 Analyze and Evaluate the Extracts

Fortify the extracts with analytes, internal standards, and surrogates and bring to volume (2 mL) with 

elution solvent. Ensure that the sodium sulfate desiccant is properly conditioned. Dry the extracts with 

sodium sulfate per Section 11.6. Analyze the extracts. The retention times should match those observed 

for calibration standards. If retention time shifts occur, increase the nitrogen volume and repeat the 

experiment until the problem is resolved.

9.1.8 Select a Volume above the Minimum

The authors determined empirically that up to six times the minimum volume necessary to eliminate 

retention time shifts could be applied without adverse effects on method performance. However, 

excessive drying (beyond this limit) decreased analyte recovery during the solvent elution step. 

2-Propen-1-ol is the most sensitive analyte to over drying. The authors recommend adding a few 

minutes to the drying time representing the optimized nitrogen volume to ensure retention time shifts 

do not occur if operating conditions vary slightly, e.g., different lots of SPE media. Use the rotameter to 

ensure that the optimized nitrogen volume is applied to all subsequent sample extractions.

9.2 Initial Demonstration of Capability (IDC)

The IDC must be successfully performed prior to analyzing field samples. The IDC must be repeated if 

changes are made to analytical parameters not previously validated during the IDC, for example, 

selection of alternate quantitation ions, extending the calibration range, or changing the internal 

standard assignment of an analyte. Prior to conducting the IDC, the analyst must meet the calibration 

requirements outlined in Section 10. The same calibration range used during the IDC must be used for

the analysis of field samples.

9.2.1 Demonstration of Low System Background

Analyze an LRB immediately after injecting the highest calibration standard in the selected calibration 

range. Confirm that the blank is free from contamination as defined in Section 9.3.1.

9.2.2 Demonstration of Precision

Prepare, extract and analyze five replicate LFBs in a valid Extraction Batch (five replicate LFBs and an 

LRB). Fortify the LFBs near the midpoint of the initial calibration curve. The method preservatives must 

be added to the samples as described in Section 8.1. The percent relative standard deviation (%RSD) of 

the concentrations of the replicate analyses must be less than, or equal to, 20% for all method analytes.
14

%RRRRRR = SSSSSSSSSSSSSS DDDDDD DDDD oo MM MMMM CC CC

MM CC CC

× 100

9.2.3 Demonstration of Accuracy

Using the same set of replicate data generated for Section 9.2.2, calculate the average percent recovery. 

The average percent recovery for each analyte must be within plus or minus 30% of the true value.

AA AA % RR RR = AA AA MM MMMM CC CC

FF CC CC

× 100

9.2.4 Minimum Reporting Level (MRL) Confirmation

Establish a target concentration for the MRL based on the intended use of the method. Analyze an initial 

calibration following the procedures in Section 10. The lowest calibration standard used to establish the 

initial calibration (as well as the low-level CCC) must be at, or below, the concentration representing the 

MRL. Establishing the MRL concentration too low may cause repeated failure of ongoing QC 

requirements. Confirm the MRL following the procedure outlined below.

9.2.4.1 Prepare and Analyze MRL Samples

Fortify, extract and analyze seven replicate LFBs at, or below, the proposed MRL concentration. The LFBs 

must contain the method preservatives as specified in Section 8.1.

9.2.4.2 Calculate MRL Statistics

Calculate the mean and standard deviation for each analyte in these replicates. Determine the Half 

Range for the Prediction Interval of Results (HRPIR) using the following equation:

HH PPPPPP = 3.963

Where,

S is the standard deviation and 3.963 is a constant value for seven replicates.1

Calculate the Upper and Lower Limits for the Prediction Interval of Results (PIR = Mean ± HRPIR) as shown

below.

UUpppp PPPP LL LL = MM + HH PPPPPP

FF CC CC

× 100

LL LL PPPP LL LL = MM − HH PPPPPP

FF CC CC

× 100

9.2.4.3 MRL Acceptance Criteria

The MRL is confirmed if the Upper PIR Limit is less than, or equal to, 150%; and the Lower PIR Limit is 

greater than, or equal to, 50%. If these criteria are not met, the MRL has been set too low and must be 

confirmed again at a higher concentration.

NOTE: These equations are only valid for seven replicate samples.

9.2.5 Quality Control Sample (QCS)

Analyze a Quality Control Sample (Sect. 9.3.10) to confirm the accuracy of the primary calibration 

standards.
15

9.3 Ongoing QC Requirements

This section describes the ongoing QC elements that must be included when processing and analyzing 

field samples.

9.3.1 Laboratory Reagent Blank (LRB)

Analyze an LRB with each Extraction Batch. The LRB must contain the method preservatives and the 

surrogate analytes at the same concentration used to fortify field samples. Background from method 

analytes or contaminants that interfere with the measurement of method analytes must be less than 

one-third the MRL. If method analytes are detected in the LRB at concentrations equal to, or greater 

than this level, then all data for the problem analyte(s) must be considered invalid for all samples that 

yielded a positive result. Subtracting blank values from sample results is not permitted.

9.3.1.1 Estimating Background Concentrations

Although quantitative data below the MRL may not be accurate enough for data reporting, such data 

are useful in determining the magnitude of background interference. Therefore, the analyte 

concentrations in the LRB may be estimated by extrapolation when results are below the MRL.

9.3.1.2 Influence of Background on Selection of MRLs

It is important to evaluate background values of analytes that commonly occur in LRBs. The MRL should 

be set at a value greater than three times the mean concentration observed in replicate LRBs. If LRB 

values are highly variable, setting the MRL to a value greater than the mean LRB concentration plus 

three times the standard deviation may provide a more realistic MRL.

9.3.1.3 Evaluation of Background when Analytes Exceed the Calibration Range

After analysis of a sample in which method analytes exceed the calibration range, one or more LRBs 

must be analyzed (to detect potential carryover) until the system meets the LRB acceptance criteria. If 

this occurs during an automated sequence, examine the results of samples analyzed following the 

sample that exceeded the calibration range. If the analytes that exceeded the calibration range in the 

previous sample are detected at, or above, the MRL, these samples are invalid. If the affected analytes 

do not exceed the MRL, these subsequent samples may be reported.

9.3.2 Continuing Calibration Check (CCC)

Analyze CCC standards at the beginning of each Analysis Batch, after every tenth field sample, and at the 

end of the Analysis Batch. See Section 10.3 for concentration requirements and acceptance criteria for 

CCCs.

9.3.3 Laboratory Fortified Blank

An LFB is required with each Extraction Batch. The concentration of the LFB must be rotated between 

low, medium, and high concentrations from batch to batch. The low concentration LFB must be within a 

factor of two times the MRL. The high concentration LFB must be near the high end of the calibration 

range established during the initial calibration. Results of the low-level LFB analyses must be within 50% 

of the true value for each analyte. Results of the medium and high-level LFB analyses must be within 

plus or minus 30% of the true value for each analyte. If the LFB results do not meet these criteria, then 

all data for the problem analytes must be considered invalid for all samples in the Extraction Batch.

9.3.4 BFB MS Tune Check

A complete description of the MS Tune Check is found in Sect. 10.1.1. Perform the MS Tune Check in full 

scan mode. The acceptance criteria for the MS Tune Check are summarized in Section 17, Table 1. The 
16

MS Tune Check must be performed each time a major change is made to the mass spectrometer and 

prior to establishing or re-establishing an initial calibration. Daily BFB analysis is not required.

9.3.5 Internal Standards (IS)

The analyst must monitor the peak areas of the internal standards (1,4-dioxane-d8 and 

chlorobenzene-d5) in all injections of the Analysis Batch. The internal standard responses (as indicated 

by peak areas) in any chromatographic run must not deviate by more than plus or minus 50% from the 

average areas measured during the initial calibration. In addition, the peak areas must not deviate by 

more than plus or minus 30% from the responses in the most recent CCC. If an IS area for a sample does 

not meet these criteria, check the corresponding IS area of the most recent CCC and proceed as follows.

9.3.5.1 Corrective Action for Failed Internal Standards in Samples

If the IS criterion is met in the CCC but not the sample, reanalyze the extract in a subsequent Analysis 

Batch. If the IS area fails to meet the acceptance criteria in the repeat analysis, but passes in the most 

recent CCC, extraction of the sample may need to be repeated provided the sample is still within the 

holding time. If re-extraction is not possible, qualify the original sample results as “suspect–IS response.” 

Qualify only those analytes referenced to the failed internal standard.

9.3.5.2 Corrective Action for Failed Internal Standards in CCCs

If both the original field sample and the CCC fail the IS area criterion, take corrective action (e.g., 

Sect. 10.4). After servicing the instrument, re-inject the extract in a subsequent Analysis Batch. If the IS 

area fails to meet the acceptance criteria in the repeat analysis, but passes in the most recent CCC, 

extraction of the sample may need to be repeated provided the sample is still within the holding time. If 

re-extraction is not possible, qualify the original sample results as “suspect–IS response.” Qualify only 

those analytes referenced to the failed internal standard.

9.3.6 Surrogate Recovery

The surrogate analytes are fortified into the aqueous portion of field samples and QC samples prior to 

extraction. Calculate the percent recovery for each surrogate. Recovery must be in the range of 70 to 

130%.

% RR RR = (

CC CCCC CC SSSS SSSS CC CC

FF CC CC oo SSSS ) × 100

9.3.6.1 Corrective Action for Failed Surrogates

If a surrogate fails to meet the recovery criterion, evaluate the recovery of the surrogate in the CCCs, the 

integrity of the calibration solutions, and take corrective action such as recalibration and servicing the 

GC/MS system. Analyze the failed extract in a subsequent Analysis Batch. If the repeat analysis meets 

the surrogate recovery criterion, report only data for the reanalyzed extract. If the repeat analysis fails 

the 70 to 130% recovery criterion after corrective action, extraction of the sample must be repeated 

provided a sample is available and still within the holding time. If the re-extracted sample also fails the 

recovery criterion, or if a duplicate field sample is not available, qualify all data for that sample as 

“suspect–surrogate recovery.”

9.3.7 Laboratory Fortified Sample Matrix (LFSM)

Within each Extraction Batch, analyze a minimum of one LFSM. The background concentrations of the 

analytes in the sample matrix must be determined in a separate field sample and subtracted from the 

measured values in the LFSM. If various sample matrixes are analyzed regularly, for example, drinking 
17

water processed from ground water and surface water sources; collect performance data for each 

source.

9.3.7.1 Prepare the LFSM

Prepare the LFSM by fortifying a Field Duplicate with an appropriate amount of the analyte PDS 

(Sect. 7.6.3) and surrogate PDS (Sect. 7.6.2). Generally, select a spiking concentration that is greater than 

or equal to the native concentration for most analytes. Selecting a duplicate aliquot of a sample that has 

already been analyzed aids in the selection of an appropriate spiking level. If this is not possible, use 

historical data when selecting a fortifying concentration.

9.3.7.2 Calculate the Percent Recovery

Calculate the percent recovery (%R) using the equation:

%RR = (AA − BB)

CC

× 100

Where,

A = measured concentration in the fortified sample,

B = measured concentration in the unfortified sample, and

C = fortification concentration.

In order to obtain meaningful percent recovery results, correct the measured values in the LFSM and 

LFSMD for the native levels in the unfortified samples, even if the native values are less than the MRL.

9.3.7.3 Evaluate Analyte Recovery

Recoveries for analytes fortified at concentrations near or at the MRL (within a factor of two times the 

MRL concentration) must be within plus or minus 50% of the true value. Recoveries for analytes fortified 

at all other concentrations must be within plus or minus 30% of the true value. If the accuracy for any 

analyte falls outside the designated range, and the laboratory performance for that analyte is shown to 

be in control in the CCCs and in the LFB, the recovery is judged matrix biased. Report the result for the 

corresponding analyte in the unfortified sample as “suspect–matrix.”

9.3.8 Field Duplicate or Laboratory Fortified Sample Matrix Duplicate (FD or LFSMD)

Within each Extraction Batch, analyze a minimum of one Field Duplicate or one Laboratory Fortified 

Sample Matrix Duplicate. If the method analytes are not routinely observed in field samples, analyze an 

LFSMD rather than an FD.

9.3.8.1 Calculate the RPD for Field Duplicates

Calculate the relative percent difference (RPD) for duplicate measurements (FD1 and FD2) using the 

equation:

RR RR = |FD1 − FD2|

(FD1 + FD2)⁄2

× 100

9.3.8.2 Acceptance Criterion for Field Duplicates

RPDs for Field Duplicates must be plus or minus 30% for each analyte. Greater variability may be 

observed when Field Duplicates have analyte concentrations that are near or at the MRL (within a factor 

of two times the MRL concentration). At these concentrations, Field Duplicates must have RPDs that are 

plus or minus 50%. If the RPD of an analyte falls outside the designated range, and the laboratory 

performance for the analyte is shown to be in control in the CCC and in the LFB, the precision is judged 
18

matrix influenced. Report the result for the corresponding analyte in the unfortified sample as “suspect–

matrix.”

9.3.8.3 Calculate the RPD for the LFSM and LFSMD

If an LFSMD is analyzed instead of a Field Duplicate, calculate the RPD using the equation:

RR RR = |LL − LL |

(LL + LL )⁄2

× 100

9.3.8.4 Acceptance Criterion for Fortified Matrix

RPDs for duplicate LFSMs must be plus or minus 30% for each analyte. Greater variability may be 

observed when the matrix is fortified at analyte concentrations near or at the MRL (within a factor of 

two times the MRL concentration). LFSMs at these concentrations must have RPDs that are plus or 

minus 50%. If the RPD of an analyte falls outside the designated range, and the laboratory performance 

for the analyte is shown to be in control in the CCC and in the LFB, the precision is judged matrix 

influenced. Report the result for the corresponding analyte in the unfortified sample as “suspect–

matrix.”

9.3.9 Retention Time Shifts

If QC failures are associated with retention time shifts in a sample, residual water in the extract may be 

the cause of the failed QC. In this case, re-extract the sample and increase the time devoted to drying 

the SPE cartridge with nitrogen.

9.3.10 Quality Control Sample (QCS)

A QCS (as defined in Sect. 3.14) must be analyzed during the IDC, and then at least quarterly thereafter. 

Prepare the QCS in the elution solvent near the midpoint of the calibration range. The acceptance 

criterion for the QCS is plus or minus 20% of the true value. If the accuracy for any analyte fails the 

recovery criterion, prepare fresh standard dilutions and repeat the QCS evaluation.

9.4 Method Modification QC Requirements

The analyst is permitted to modify the GC injection technique, GC column and conditions, and MS 

conditions. Any proposed method modifications must retain the basic chromatographic elements of this 

method (Sect. 2). Examples of method modifications include alternate GC column phases, MS 

conditions, quantitation ions, and additional QC analytes proposed for use with the method. The 

following are required after a method modification.

9.4.1 Repeat the IDC

Establish an acceptable initial calibration (Sect. 10.2) using the modified conditions. Repeat the 

procedures of the IDC (Sect. 9.2).

9.4.2 Document Performance in Representative Sample Matrixes

The analyst is also required to evaluate and document method performance for the proposed 

modifications in real matrixes 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, could fail ongoing method QC requirements in real matrixes. This is particularly important for 

methods subject to matrix effects, such as GC/MS-based methods. For example, a laboratory may 

routinely analyze drinking water from municipal treatment plants that process ground water, surface 

water, or a blend of surface and ground water. In this case, the method modification requirement could 

be accomplished by assessing precision (Sect. 9.2.2) and accuracy (Sect. 9.2.3) in a surface water with 
19

moderate to high total organic carbon (e.g., 2 mg/L or greater) and a hard ground water (e.g., 250 mg/L 

as calcium carbonate (CaCO3) equivalent, or greater).

9.4.3 Monitor Performance of the Modified Method

The results of Section 9.4.1 and Section 9.4.2 must be appropriately documented by the analyst and 

independently assessed by the laboratory’s QA officer prior to analyzing field samples. When 

implementing method modifications, it is the responsibility of the laboratory to review the results of 

ongoing QC, and in particular, the results associated with LFSM, duplicate samples, CCCs, and the 

internal standard area counts. If repeated failures are noted, the modification must be abandoned.

10 Calibration and Standardization

Demonstration and documentation of acceptable mass spectrometer tune and initial calibration is 

required before performing the IDC and prior to analyzing field samples. The MS Tune Check and initial 

calibration must be repeated each time a major instrument modification is made, or maintenance is 

performed.

10.1 GC/MS Optimization

Any type of MS may be used as described in Sect. 6.15.5. Data presented in Section 17 were obtained in 

the SIM mode using a quadrupole mass analyzer. Operation of the MS in selected ion monitoring mode

enhances sensitivity; however, less qualitative data are obtained for the method analytes and any 

potential interferences. Because of this, and because the selected ions for the compounds of interest 

are low masses that are likely to occur more frequently in interferences than most higher mass ions, the 

analyst should also rely on chromatographic resolution to reduce the possibility of false positives. It is 

recommended to use a GC column that is at least 30 m in length, with sufficient capacity to separate the 

least retained analytes from the extraction solvent, and that provides adequate separation of the 

compounds of interest from possible interferences.

10.1.1 MS Tune and MS Tune Check

Calibrate the mass and abundance scales of the MS using calibration compounds and procedures 

recommended by the manufacturer with any modifications necessary to meet tuning requirements. 

Introduce BFB (Sect. 7.7.4) into the GC/MS system. Acquire a mass spectrum using a scan range of 

m/z 35–260. 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 allowed; however, the background scans must be 

chosen from the baseline prior to, or after, elution of the BFB peak. If the BFB mass spectrum does not 

meet all criteria in Section 17, Table 1, the MS must be re-tuned to meet these criteria before 

proceeding with the initial calibration.

10.1.2 GC Conditions

Establish GC operating conditions appropriate for the GC column dimensions by optimizing the inlet 

conditions and temperature program. GC conditions used during method development are summarized 

in Section 17, Table 2. Tailing peak profiles are expected for 1-butanol, 2-propen-1-ol and, especially, 

2-methoxyethanol. However, the column and inlet conditions chosen should not cause peaks to split or 

broaden. The authors obtained acceptable results for this method as illustrated by the profiles in the 

reconstructed ion chromatogram (Sect. 17, Figure 2) and in the extracted ion current profiles (EICPs) 

(Sect. 17, Figure 3). Optimize chromatographic resolution such that a unique quantitation ion is available 
20

for each analyte that is free from interference due to an identical fragment ion in any co-eluting (or 

overlapping) peaks.

10.1.3 SIM MS Conditions

Choose one primary quantitation ion and at least one confirmation ion. If possible, select a second 

confirmation ion. Additional ions may be monitored that demonstrate a unique fragment in the mass 

spectrum. Verify that the primary ion is free from interference due to an identical fragment ion in any 

overlapping peaks. If the chromatogram is divided into SIM windows (also termed segments or periods), 

the laboratory must ensure that each method analyte elutes entirely within the assigned window during 

each Analysis Batch. Make this observation by viewing the mass chromatogram of the quantitation ion 

for each analyte in the CCCs analyzed during an Analysis Batch. The entire Analysis Batch is invalid if one 

or more analyte peaks drift outside of designated SIM windows in any CCC.

10.1.4 Suggested Ions and Dwell Times

Section 17, Table 3 lists ions used for quantitation and confirmation during method development. Set 

the dwell time for each ion to acquire at least seven to 10 scans across each chromatographic peak. SIM 

windows and dwell times used to collect method performance data are included in Table 3.

10.2 Initial Calibration

An initial calibration requires optimizing GC/MS conditions and confirming that the instrument meets 

the BFB tune check criteria (Section 10.1.1). Calibration must be performed using peak areas and the 

internal standard technique. Calibration using peak heights and external standard calibration are not 

permitted.

10.2.1 Calibration Standards

Prepare a set of at least six calibration standards as described in Section 7.7. The lowest concentration 

of the calibration standards must be at, or below, the MRL. The MRL must be confirmed using the 

procedure outlined in Section 9.2.4 after establishing the initial calibration. Additionally, field samples 

must be quantified using a calibration curve that spans the same concentration range used to collect the 

IDC data, e.g., analysts are not permitted to use a restricted calibration range to meet the IDC criteria 

and then use a larger dynamic range during analysis of field samples.

10.2.2 Calibration Curve

Calibrate the GC/MS system using peak areas and the internal standard technique. Fit the calibration 

points with either a linear or a quadratic regression (response vs. concentration). Weighting may be 

used. The GC/MS instrument used during method development was calibrated using quadratic curves 

with no weighting. Because the surrogate analytes are added at a single concentration level to the 

calibration standards, calibrate for each surrogate using an average response factor. Suggested internal 

standard assignments and quantitation ions for each method analyte are presented in Section 17, 

Table 3.

10.2.3 Calibration Acceptance Criteria

Evaluate the initial calibration by calculating the concentration of each analyte as an unknown against its 

regression equation. For calibration levels that are less than or equal to the MRL, the result for each 

analyte should be within plus or minus 50% of the true value. All other calibration points should 

calculate to be within plus or minus 30% of their true value. If these criteria cannot be met, the analyst 

could have difficulty meeting ongoing QC criteria. In this case, corrective action is recommended such as 

reanalyzing the calibration standards, restricting the range of calibration, or performing instrument 
21

maintenance. If the cause for failure to meet the criteria is due to contamination or standard 

degradation, prepare fresh calibration standards and repeat the initial calibration.

10.3 Continuing Calibration Checks (CCCs)

Analyze a CCC to verify the initial calibration at the beginning of each Analysis Batch, after every tenth 

field sample, and at the end of each Analysis Batch. The beginning CCC for each Analysis Batch must be 

at, or below, the MRL. This CCC verifies instrument sensitivity prior to the analysis of samples. Alternate 

subsequent CCCs between the remaining calibration levels. Verify that the CCC meets the following 

criteria.

10.3.1 Internal Standard Responses

The absolute area of the quantitation ion for each internal standard (1,4-dioxane-d8 and chlorobenzened5) must be within plus or minus 50% from the average area measured during the initial calibration. If 

these limits are exceeded, corrective action is necessary (Sect. 10.4).

10.3.2 Surrogate Analytes

The calculated concentration of the surrogate analytes must be within plus or minus 30% of the true 

value. If the surrogate analytes fail this criterion, corrective action is necessary (Sect. 10.4).

10.3.3 Method Analytes

Calculate the concentration of each method analyte in the CCC. Each analyte fortified at a level less than 

or equal to the MRL must calculate to be within plus or minus 50% of the true value. The calculated 

concentration of the method analytes in CCCs fortified at all other levels must be within plus or minus 

30%. If these limits are exceeded, then all data for the failed analytes must be considered invalid. Any 

field samples analyzed since the last acceptable CCC that are still within holding time must be reanalyzed 

after an acceptable calibration has been restored.

10.4 Corrective Action

Failure to meet calibration performance criteria requires corrective action. Acceptable method 

performance may be restored simply by servicing the GC injection port and clipping the column. 

Following this and other minor corrective action, check the calibration with a mid-level CCC and a CCC at 

the MRL, or recalibrate according to Section 10.2. If internal standard and calibration failures persist, 

maintenance may be required, such as servicing the MS system and replacing the GC column. These 

latter measures constitute major maintenance, and the analyst must return to the initial calibration step 

(Sect. 10.2) and verify sensitivity by analyzing a CCC at, or below, the MRL.

11 Procedure

This section describes the procedures for sample preparation and analysis. Important aspects of this 

analytical procedure include proper sample collection and storage (Sect. 8), ensuring that the 

instrument is properly calibrated (Sect. 10), and that all required QC elements are included (Sect. 9.3). 

For this method, the volume of nitrogen required to dry SPE cartridges must be determined prior to 

conducting this procedure. Refer to Section 9.1 for guidance on determining this volume.

11.1 Sample Preparation 

All field and QC samples must contain the preservatives listed in Section 8.1, including the LRB and LFB.
22

11.1.1 QC Samples

With each Extraction Batch (Sect. 3.4), include one LRB, one LFB, and one LFSM. One FD, or one LFSMD,

is required. Refer to Section 9.3 for the frequency of QC elements. Fortify the LFB, LFSM, and LFSMD, 

with an appropriate volume of analyte PDS (Sect. 7.6.3).

11.1.2 Surrogate Analytes

Add an aliquot of the surrogate PDS (Sect. 7.6.2) to each sample. Cap and mix the samples. For method 

development work, a 10 μL aliquot of the 50 μg/mL surrogate PDS was added to 0.050 L in the original 

sample bottle for a final concentration of 10 μg/L.

11.2 Extraction Procedure Using Waters AC-2 SPE Format

11.2.1 Set up the Extraction Manifold

Place extraction cartridges on the SPE vacuum manifold and attach 3 mL polypropylene reservoirs.

Establish a vacuum between –8 and –5 psig.

11.2.2 Cartridge Cleaning

Add 3 mL of 5% methanol in DCM to each reservoir and draw enough solvent through the cartridge to 

soak the sorbent. Allow the sorbent to soak for approximately one minute. Draw the remaining solvent 

to waste until the cartridge is dry. Repeat this step with 2 mL of purge-and-trap-grade methanol.

11.2.3 Cartridge Conditioning

11.2.3.1 Condition with Methanol

Add approximately 2 mL of methanol to the reservoir and draw enough solvent through the cartridge to 

soak the sorbent. Allow the sorbent to soak for approximately one minute. Draw the solvent through 

the cartridge; aspirate, but do not allow the sorbent to dry completely. It is not necessary to leave a 

solvent layer above the sorbent bed.

11.2.3.2 Condition with Water

Fill the 3 mL reservoir completely with reagent water. Draw the water through the cartridge, but do not 

allow the sorbent to dry completely. It is not necessary to leave a water layer above the sorbent bed. 

Remove the 3 mL reservoir. The AC-2 cartridges are now ready for sample loading.

11.2.4 Sample Loading

Attach 60 mL reservoirs to the SPE cartridges. Load samples at a flow rate of 5 mL/min or less using a 

vacuum between –8 and –5 psig. Approximate this rate by ensuring that individual drops are observed 

exiting the delivery tubes and by timing this step. Rinse the empty sample bottles with 5 mL of reagent 

water and add the rinse to the reservoir. After the sample passes completely through the cartridge, 

aspirate for approximately 30 seconds; close the manifold valve. After all samples are loaded, remove 

the 60 mL reservoirs and increase the vacuum to approximately 20 psig in preparation for the drying 

steps.

11.2.5 Cartridge Drying

The drying steps are very important. Precisely repeat the procedure optimized during the IDC.

11.2.5.1 Methanol Rinse Step

Attach a clean, dry 3 mL reservoir to each cartridge. Add 150 μL of methanol to each reservoir. Aspirate 

at full vacuum for approximately 30 seconds. Remove the reservoirs and set aside for later use during 

the elution step.
23

11.2.5.2 Nitrogen Purge Step

Transfer the cartridges to the drying manifold. Do not attach the drying manifold to the lid of the 

extraction manifold. Dry with high-purity nitrogen or zero air using the flow rate and duration optimized 

during the IDC. Use the rotameter to monitor the flow rate.

11.2.5.3 Drying Manifold Valves

Remove residual water from the manifold valves while the cartridges are drying. Open the valves and 

transfer a few milliliters of methanol to the top of each valve. Pull air through the valves under full 

vacuum. Do not omit this step. The manifold valves and delivery tubes hold enough water to cause 

retention time shifts when analyzing the final extract.

11.3 Extraction Procedure using UCT EU-541 SPE Format

11.3.1 Set Up the Extraction Manifold

Place extraction cartridges on the SPE vacuum manifold. Establish a vacuum between –8 and –5 psig.

11.3.2 Cartridge Cleaning

Fill each cartridge with 5% methanol in DCM and draw enough solvent through the cartridge to soak the 

sorbent. Allow the sorbent to soak for approximately one minute. Draw the remaining solvent to waste 

until the cartridge is dry. Repeat this step with 2 mL of purge-and-trap-grade methanol.

11.3.3 Cartridge Conditioning

11.3.3.1 Condition with Methanol

Add approximately 2 mL of methanol to each SPE cartridge and draw enough solvent through to soak 

the sorbent. Allow the sorbent to soak for approximately one minute. Draw the solvent through the 

cartridge; aspirate, but do not allow the sorbent to dry completely. It is not necessary to leave a solvent 

layer above the sorbent bed.

11.3.3.2 Condition with Water

Fill each cartridge completely with reagent water. Draw the water through the cartridge, but do not 

allow the sorbent to dry completely. Repeat this step a second time, but leave one to two mL of water 

above the sorbent bed.

11.3.4 Sample Loading

Attach 60 mL reservoirs to the SPE cartridges using a tube adaptor (Sect. 6.11.1). Load samples at a flow 

rate of 5 mL/min or less using a vacuum between –8 and –5 psig. Approximate this rate by ensuring that 

individual drops are observed exiting the delivery tubes and by timing this step. Rinse the empty sample 

bottles with 5 mL of reagent water and add the rinse to the reservoir. After the sample passes 

completely through the cartridge, aspirate for approximately 30 seconds; close the manifold valve. After 

all samples are loaded, remove the 60 mL reservoirs and increase the vacuum to approximately 20 psig 

in preparation for the drying steps.

11.3.5 Cartridge Drying

The drying steps are very important. Precisely repeat the procedure optimized during the IDC.

11.3.5.1 Methanol Rinse Step

Add 200 μL of methanol to the SPE cartridge with intent to rinse residual water droplets from the walls 

of the cartridge. Any remaining water on the walls will be eliminated during the nitrogen-drying step. 

Aspirate at full vacuum for approximately 30 seconds.
24

11.3.5.2 Nitrogen Purge Step

Transfer the cartridges to the drying manifold. Do not attach the drying manifold to the lid of the 

extraction manifold. Dry with high-purity nitrogen or zero air using the flow rate and duration optimized 

during the IDC. Use the rotameter to monitor the flow rate.

11.3.5.3 Drying Manifold Valves

Remove residual water from the manifold valves while the cartridges are drying. Open the valves and 

transfer a few milliliters of methanol to the top of each valve. Pull air through the valves under full 

vacuum. Do not omit this step. The manifold valves and delivery tubes hold enough water to cause 

retention time shifts when analyzing the final extract.

11.4 Cartridge Elution

When all valves are dry, release the vacuum on the extraction manifold and place 2 mL volumetric tubes 

under each sample position. Return the dried cartridges to the same position on the manifold used 

during sample loading. (Attach a dry, 3 mL reservoir to each Waters AC-2 cartridge. It is not necessary to 

reverse the cartridges.) Measure approximately 2.3 mL of elution solvent and add this volume to each 

reservoir. Soak each cartridge for 1 minute then elute in a slow, dropwise manner. Aspirate each 

cartridge completely. The extracts should not have a visible water layer. Typically, approximately 1.8 mL 

of elution solvent is recovered.

11.5 Internal Standard Addition

Add an aliquot of the internal standard PDS (Sect. 7.6.1) to each extract. For method development work, 

a 10 μL aliquot of the 50 μg/mL internal standard PDS was added to each 2 mL extract for a final 

concentration of 0.25 μg/mL. Bring each extract to volume with the 5% methanol in DCM elution 

solvent.

11.6 Extract Drying

Add approximately 2 cm3 of sodium sulfate directly to the 2 mL volumetric tube. Estimate this volume of 

salt by filling the 2 mL volumetric until the solid level reaches just under or at the 2 mL mark. The liquid 

level will rise close to the ground glass section of the volumetric, but should not overflow. Stopper 

securely and vortex for 10 seconds. Allow the desiccant to remain in contact with the solvent for 

15 minutes. Using a disposable pipette, transfer the supernatant to a 2 mL autosampler vial. (Condition 

the sodium sulfate at 400 °C for four hours just prior to use with this method. Repeat the conditioning 

process at least once per month and more frequently in humid weather.)

11.7 Analysis of Sample Extracts

Establish GC/MS operating conditions per the guidance in Section 10.1. Analyze an archived, unfortified 

extract to condition the GC inlet and column. This step is optional; however, the authors believe it is an 

expedient means of “conditioning” the analytical system, especially after maintenance or an extended 

period of disuse. Establish a valid initial calibration following the procedures in Section 10.2 or confirm 

that the existing calibration is still valid by analyzing a low-level CCC. If establishing an initial calibration 

for the first time, complete the IDC prior to analyzing field samples. Analyze field and QC samples in a 

properly sequenced Analysis Batch as described in Section 11.8.

11.8 The Analysis Batch

An Analysis Batch is a sequence of samples that is analyzed on the same instrument during a 24 hour 

period that begins and ends with the analysis of CCCs. The Analysis Batch must not have more than 20 
25

field samples. QC samples, such as the LRB, LFB, FD, LFSM, and LFSMD, are not counted as part of the 

20-sample limit. The purpose of the field sample limit is to ensure that a low-level CCC and an LRB are 

repeated on a regular and frequent basis. Analytical conditions for the Analysis Batch must be the same 

as those applied during calibration.

11.8.1 Initial CCC

After a valid calibration is established, begin every Analysis Batch by analyzing a low-level CCC at, or 

below, the MRL. The calculated concentration of the method analytes in this CCC must be within plus or 

minus 50% of the true value. The calculated concentration of the surrogate analytes must be within plus 

or minus 30%. The initial CCC must pass the plus or minus 50% internal standard area criterion 

(Sect. 10.3.1). The initial CCC confirms that the calibration curve is valid.

11.8.2 Field and QC Samples

After the initial CCC, continue the Analysis Batch by analyzing an LRB, followed by field and QC samples.

11.8.3 CCC Frequency

Analyze a mid- or high-level CCC after every tenth field sample. QC samples, such as the LRB, LFB, FD, 

LFSM, and LFSMD, are not counted when determining the required frequency of CCCs.

11.8.4 Final CCC

The last injection of the Analysis Batch must be a mid- or high-level CCC. The acquisition start time of the 

final CCC must be within 24 hours of the acquisition start time of the low-level CCC at the beginning of 

the Analysis Batch. More than one Analysis Batch within a 24 hour period is permitted. An Analysis 

Batch may contain field and QC samples from multiple extraction batches.

11.8.5 Initial Calibration Frequency

A full calibration curve is not required before starting a new Analysis Batch. A previous calibration can be 

confirmed by running an initial, low-level CCC followed by an LRB. If a new calibration curve is analyzed, 

an Analysis Batch run immediately thereafter must begin with a low-level CCC and an LRB.

12 Data Analysis and Calculations

12.1 Establish Retention Time Windows

Select an appropriate retention time window for each analyte to identify them in QC and field sample 

chromatograms. Base this assignment on measurements of actual retention time variation for each 

compound in standard solutions analyzed on the GC/MS over the course of time. The suggested 

variation is plus or minus three times the standard deviation of the retention time for each compound 

for a series of injections. The injections from the initial calibration and from the IDC may be used to 

calculate the retention time window. However, the experience of the analyst should weigh heavily on 

the determination of an appropriate range.

12.2 Identify Analytes by Retention Time

Initially, identify each analyte by comparison of its retention time with that of the corresponding analyte 

peak in a recent initial calibration standard or CCC. Use the same software settings established during 

the calibration procedure and the predetermined retention time windows.

12.3 Confirm Analyte Identifications

Examine the SIM spectrum for each analyte. Use appropriate background subtraction to remove ions 

contributed by co-eluting matrix components. For each analyte identified by retention time, at least one 
26

confirmation ion must be present. The abundance of the confirmation ions relative to the quantitation 

ion should agree within an absolute 20 percent of the relative abundance in the spectrum taken from a 

recent calibration standard. For example, if an ion has a relative abundance of 30 percent in the 

calibration standard, its abundance in the sample spectrum should be in the range of 10 to 50 percent. 

Only confirmation ions that exhibit greater than 30% relative abundance to the quantitation ion in the 

mass spectrum of the calibration standard must meet this criterion. Knowledge of sample history and 

the experience of the analyst are important factors that may aid analyte confirmation.

12.4 Compound Quantitation

Calculate analyte concentrations using the multipoint calibration. Report only those values that fall 

between the MRL and the highest calibration standard. Calculations should be rounded to an 

appropriate number of significant figures, typically two, but not more than three. Do not base 

quantitation of samples on response factors calculated from CCCs.

12.5 Data Review

Prior to reporting data, the chromatograms must be reviewed for incorrect peak identification or 

improper integration. Prior to reporting data, the laboratory is responsible for verifying that QC 

requirements have been met and that any appropriate qualifier is assigned.

12.6 Exceeding the Calibration Range

The analyst must not extrapolate beyond the established calibration range. If an analyte result exceeds 

the range of the initial calibration curve, dilute the extract with elution solvent containing the required 

concentration of internal standards. Re-inject the diluted sample. Incorporate the dilution factor into 

final concentration calculations. The resulting data must be annotated as a dilution, and the reported 

MRLs must reflect the dilution factor. Report surrogate recoveries observed in the undiluted sample.

13 Method Performance

13.1 Precision, Accuracy, and LCMRL Results

Tables for these data are presented in Section 17. LCMRLs are presented for each of two SPE formats: 

Waters AC-2, 400 mg cartridges (Table 4) and UCT EU-541, 600 mg cartridges (Table 8). For each of these 

formats, single-laboratory precision and accuracy data are presented for three water matrixes: reagent 

water (Waters AC-2: Table 5 and UCT EU-541: Table 9), finished ground water (Waters AC-2: Table 6 and 

UCT EU-541: Table 10), and finished surface water (Waters AC-2: Table 7 and UCT EU 541: Table 11). 

Figure 4 and Figure 5 are reconstructed ion chromatograms of extracts (Waters AC-2 format) obtained 

from drinking water using the GC/MS conditions employed during method development.

13.2 Analyte Stability Study

Chlorinated (finished) surface water samples were inoculated with diluted, microbial-rich water from an 

ambient source, and fortified with 0.80 μg/L of 1,4-dioxane and 4.0 μg/L of 2-propen-1-ol, 1-butanol and 

2-methoxyethanol. These samples were preserved and stored as required in this method. The percent 

change from the initial analyzed concentration observed after 7, 14, 21, and 28 days is presented in 

Section 17, Table 12.
27

13.3 Extract Storage Stability

Extract storage stability studies were conducted on extracts obtained from chlorinated surface water 

fortified with the method analytes (Sect. 13.2). The percent change from the initial analyzed 

concentration observed after 7, 14, 21, and 28 days storage is presented in Section 17, Table 13.

14 Pollution Prevention

For information about pollution prevention applicable to laboratory operations described in this 

method, consult: Less is Better, Guide to Minimizing Waste in Laboratories, a web-based resource 

available from the American Chemical Society at www.acs.org.

15 Waste Management

The Agency requires that laboratory waste management practices be consistent with all applicable rules 

and regulations, and that laboratories protect the air, water, and land by minimizing and controlling all 

releases from fume hoods and bench operations. In addition, compliance is required with any sewage 

discharge permits and regulations, particularly the hazardous waste identification rules and land 

disposal restrictions.

16 References

1. US EPA Document # 815-R-05-006, “Statistical Protocol for the Determination of the SingleLaboratory Lowest Concentration Minimum Reporting Level (LCMRL) and Validation of Laboratory 

Performance at or Below the Minimum Reporting Level (MRL)”, Office of Water, November 2004.

2. US EPA Document # EPA 815-R-11-001 , “Technical Basis for the Lowest Concentration Minimum 

Reporting Level (LCMRL) Calculator”, Office of Water, December 2010.
28

17 Tables, Figures, and Method performance Data

Table 1. 4-Bromofluorobenzene (BFB) Mass Intensity Criteria

m/z Required Intensity (relative abundance)

95 Base peak, 100% relative abundance

96 5 to 9% of m/z 95

173 Less than 2% of m/z 174

174 Greater than 50% of m/z 95

175 5 to 9% of m/z 174

176 Greater than 95% but less than 105% of m/z 174

177 5 to 10% of m/z 176

Table 2. Gas Chromatography/Mass Spectrometry (GC/MS) Conditions

Parameter Conditionsa

Column Phenomenex (Torrance, CA) ZB-WAX plus: 30 meter, 0.25 mm i.d., 0.5 

μm film thickness (df)

Inlet liner 4-mm i.d., single-gooseneck, deactivated glass with deactivated glass 

wool

Inlet conditions 200 °C, pulsed splitless injection mode: 10 psig until 0.5 minutes, purge 

flow (split) on at 0.5 minutes @ 100 mL/min

Injection volume 1 μL using a 10 μL syringe

Column flow rate 0.9 mL/min in constant flow mode, helium carrier gas

GC temperature program 30 °C for 0.5 min, 10 °C/min to 110 °C, hold 0 min, 25 °C/min to 200 °C, 

hold 6 min

Solvent delay 9.8 min before activating filaments in the electron impact source

MS source temperature 230 °C

MS quadrupole 

temperature

150 °C

GC/MS interface Direct, 200 °C

a. The chromatograms presented in Figures 2–5 were obtained under these conditions.
29

Table 3. Retention Times, Quantitation Ions, and Internal Standard Assignmentsa

Analyte SIM Window 

(minutes)

RTb Q-Ionc Confirmation

Ionsc

ISc Reference

Filament delay 9.8

Internal standard (IS): 

1,4-dioxane-d8

9.8 – 10.6 10.29 96 64, 46 ---

1,4-dioxane 9.8 – 10.6 10.31 88 87, 58, 57 1,4-dioxane-d8

Surrogate: 2-propen-1-ol-d6 10.6 – 12.1 11.16 61d 63, 46 chlorobenzene-d5

2-propen-1-ol 10.6 – 12.1 11.26 57 58, 55, 39 chlorobenzene-d5

Surrogate: 1-butanol-d10 10.6 – 12.1 11.71 64 63, 50, 46 chlorobenzene-d5

1-butanol 10.6 – 12.1 11.87 56 55, 43, 41 chlorobenzene-d5

2-methoxyethanol 12.1 – 22.5 12.50 45 76, 47, 58 chlorobenzene-d5

Internal standard: 

chlorobenzene-d5

12.1 – 22.5 13.14 117 76, 119 ---

a. These quantitation ions are appropriate for the column used to generate method performance data.

See Figures 2–5 for reconstructed ion chromatograms (RICs) and extracted ion current profiles 

(EICPs) obtained during collection of the method performance data.

b. RT = retention time observed using Phenomenex Zebron ZB-WAX plus column.

c. Dwell times vary between 20 and 40 ms.

d. This mass corresponds to C3D4HO+. rather than the expected fragment, C3D5O+., m/z 62.

Table 4. LCMRL Results for the Waters AC-2 SPE Formata

Analyte LCMRL Fortification Levels (μg/L) Calculated LCMRL (μg/L)

1,4-dioxane 0.0, 0.040, 0.070, 0.10, 0.20, 0.30, 0.40, 0.50 0.074

2-propen-1-ol 0.0, 0.20, 0.35, 0.50, 1.0, 1.5, 2.0, 2.5 0.30

1-butanol 0.0, 0.20, 0.35, 0.50, 1.0, 1.5, 2.0, 2.5 0.44

2-methoxyethanol 0.0, 0.20, 0.35, 0.50, 1.5, 1.0, 2.0, 2.5 0.37

a. LCMRL = lowest concentration minimum reporting limit; SPE = solid phase extraction.

Table 5. Precision and Accuracy Data for Reagent Water: Waters AC-2 SPE Formata

Analyte Fortification

(μg/L)b

Mean %Rc

(n=7)

%RSDc Fortification

(μg/L)

Mean %R

(n=5)

%RSD

1,4-dioxane 0.40 102 3.9 8.0 96.8 2.0

2-propen-1-ol 2.0 88.1 4.4 40 90.8 1.1

1-butanol 2.0 97.0 2.6 40 92.2 1.8

2-methoxyethanol 2.0 93.3 3.0 40 92.4 1.6

Surrogate: 

2-propen-1-ol-d6

10 92.6 3.3 10 92.2 0.94

Surrogate: 

1-butanol-d10

10 95.5 2.3 10 92.7 1.1

a. SPE = solid phase extraction.

b. The MRL was confirmed at these concentrations during collection of the method performance data.

c. %R = percent recovery; %RSD = percent relative standard deviation.
30

Table 6. Precision and Accuracy Data for Ground Water: Waters AC-2 SPE Formata

Analyte Fortification

(μg/L)b

Mean %Rc,d

(n=5)

%RSDd Fortification

(μg/L)

Mean %Rc

(n=5)

%RSD 

1,4-dioxane 0.40 104 3.0 8.0 98.5 2.2

2-propen-1-ol 2.0 93.0 2.7 40 92.5 2.4

1-butanol 2.0 86.4 1.8 40 92.3 2.0

2-methoxyethanol 2.0 83.3 1.2 40 92.8 2.0

Surrogate: 

2-propen-1-ol-d6

10 93.5 2.3 10 93.1 1.5

Surrogate: 

1-butanol-d10

10 95.1 1.7 10 92.7 1.7

a. Ground water physical parameters: pH = 7.8; total hardness = 337 mg/L (as CaCO3); free chlorine = 

0.60 mg/L, total chlorine = 0.86 mg/L; SPE = solid phase extraction.

b. The MRL was confirmed at these concentrations during collection of the method performance data.

c. Recoveries corrected for native levels in the unfortified matrix. 

d. %R = percent recovery; %RSD = percent relative standard deviation.

Table 7. Precision and Accuracy Data for Surface Water: Waters AC-2 SPE Formata

Analyte Fortification

(μg/L)b

Mean %Rc,d

(n=5)

%RSDd Fortification

(μg/L)

Mean %Rc

(n=5)

%RSD

1,4-dioxane 0.40 94.1 3.2 8.0 93.0 4.3

2-propen-1-ol 2.0 87.6 1.2 40 89.1 3.7

1-butanol 2.0 79.0 3.1 40 87.7 3.4

2-methoxyethanol 2.0 86.6 2.8 40 89.2 3.8

Surrogate: 

2-propen-1-ol-d6

10 88.0 1.2 10 88.9 2.9

Surrogate: 

1-butanol-d10

10 87.5 2.4 10 88.6 2.8

a. Surface water physical parameters: pH = 7.3; total organic carbon (TOC) = 2.28 mg/L; free chlorine = 

1.06 mg/L, total chlorine = 1.51 mg/L; SPE = solid phase extraction.

b. The MRL was confirmed at these concentrations during collection of the method performance data.

c. Recoveries corrected for native levels in the unfortified matrix. 

d. %R = percent recovery; %RSD = percent relative standard deviation.

Table 8. LCMRL Results for the UCT EU-541 SPE Formata

Analyte LCMRL Fortification Levels (μg/L) Calculated LCMRL (μg/L)

1,4-dioxane 0, 0.048, 0.070, 0.10, 0.20, 0.30, 0.40, 0.48 0.090

2-propen-1-ol 0, 0.16, 0.24, 0.35, 0.50, 1.0, 1.5, 2.0, 2.4 0.17

1-butanol 0, 0.24, 0.35, 0.50, 1.0, 1.5, 2.0, 2.4 0.61

2-methoxyethanol 0, 0.24, 0.35, 0.50, 1.0, 1.5, 2.0, 2.4 0.30

a. LCMRL = lowest concentration minimum reporting limit; SPE = solid phase extraction.
31

Table 9. Precision and Accuracy Data for Reagent Water: UCT EU-541 SPE Formata

Analyte Fortification

(μg/L)b

Mean %Rc

(n=5)

%RSDc Fortification

(μg/L)

Mean %R

(n=5)

%RSD

1,4-dioxane 0.40 96.2 3.7 8.0 93.7 2.3

2-propen-1-ol 2.0 84.3 5.7 40 86.7 4.2

1-butanol 2.0 97.1 0.84 40 91.8 1.9

2-methoxyethanol 2.0 86.2 8.2 40 86.4 3.4

Surrogate: 

2-propen-1-ol-d6

10 84.4 6.7 10 87.4 2.9

Surrogate: 

1-butanol-d10

10 90.1 1.8 10 92.3 1.6

a. SPE = solid phase extraction.

b. The MRL was confirmed at these concentrations during collection of the method performance data.

c. %R = percent recovery; %RSD = percent relative standard deviation.

Table 10. Precision and Accuracy Data for Ground Water: UCT EU-541 SPE Formata

Analyte Fortification

(μg/L)b

Mean %Rc,d

(n=5)

%RSDd Fortification

(μg/L)

Mean %Rc

(n=5)

%RSD 

1,4-dioxane 0.40 102 2.7 8.0 96.3 4.9

2-propen-1-ol 2.0 84.7 0.83 40 83.9 0.96

1-butanol 2.0 82.0 1.2 40 89.4 2.4

2-methoxyethanol 2.0 87.4 1.3 40 82.7 1.5

Surrogate: 

2-propen-1-ol-d6

10 84.3 2.0 10 82.9 2.0

Surrogate: 

1-butanol-d10

10 90.1 1.1 10 89.4 2.5

a. Ground water physical parameters: pH = 7.8; total hardness = 337 mg/L (as CaCO3); free chlorine = 

0.60 mg/L, total chlorine = 0.86 mg/L; SPE = solid phase extraction.

b. The MRL was confirmed at these concentrations during collection of the method performance data.

c. Recoveries corrected for native levels in the unfortified matrix. 

d. %R = percent recovery; %RSD = percent relative standard deviation.
32

Table 11. Precision and Accuracy Data for Surface Water: UCT EU-541 SPE Formata

Analyte Fortification

(μg/L)b

Mean %Rc,d

(n=5)

%RSDd Fortification

(μg/L)

Mean %Rc

(n=5)

%RSD

1,4-dioxane 0.40 96.3 3.1 8.0 101 5.0

2-propen-1-ol 2.0 92.2 3.1 40 88.1 1.0

1-butanol 2.0 84.2 5.5 40 89.7 2.1

2-methoxyethanol 2.0 93.7 1.8 40 85.7 1.2

Surrogate: 

2-propen-1-ol-d6

10 90.4 1.9 10 86.2 1.4

Surrogate: 

1-butanol-d10

10 92.4 2.3 10 90.2 1.6

a. Surface water physical parameters: pH = 7.3; total organic carbon (TOC) = 2.28 mg/L; free chlorine = 

1.06 mg/L, total chlorine = 1.51 mg/L; SPE = solid phase extraction.

b. The MRL was confirmed at these concentrations during collection of the method performance data.

c. Recoveries corrected for native levels in the unfortified matrix.

d. %R = percent recovery; %RSD = percent relative standard deviation.
33

Table 12. Aqueousa Sample Holding Time Data (n=4)

Analyte Fortified 

Conc. (μg/L)

Day Zero

Mean

(μg/L)

Day 

Zero 

%RSD

Day 7 

%Changeb

Day 7 

%RSD

Day 14

%Change

Day 14 

%RSD

Day 21

%Change

Day 21 

%RSD

Day 28

%Change

Day 28 

%RSD

1,4-dioxane 0.80 0.78 4.6 0.19 3.7 -1.8 2.7 -2.6 4.2 -0.59 6.0

2-propen-1-ol 4.0 3.5 3.2 0.53 2.0 -3.2 1.8 -3.7 2.2 -2.4 3.5

1-butanol 4.0 3.6 2.6 -1.5 2.2 -8.1 2.2 -6.8 4.2 -4.8 4.2

2-methoxyethanol 4.0 3.4 3.5 -1.2 2.6 -2.0 2.0 -0.47 3.7 0.24 2.8

a. Finished water from a surface water source. Physical parameters: pH = 7.3; total organic carbon (TOC) = 2.28 mg/L; free chlorine = 1.06 

mg/L, total chlorine = 1.51 mg/L.

b. %Change = percent change from Day Zero calculated as follows: (Day X mean concentration – Day Zero mean concentration) / Day Zero 

mean concentration * 100%, where X is the analysis day.

Table 13. Holding Time Data for Sample Extracts (n=4)

Analyte Fortified 

Conc. (μg/L)

Day Zero

Mean

(μg/L)

Day 

Zero 

%RSD

Day 7

%Changea

Day 7 

%RSD

Day 14

%Change

Day 14 

%RSD

Day 21

%Change

Day 21 

%RSD

Day 28

%Change

Day 28 

%RSD

1,4-dioxane 0.80 0.76 2.7 2.5 5.9 7.5 8.4 1.9 4.9 1.7 6.6

2-propen-1-ol 4.0 3.4 1.8 2.3 2.3 1.4 2.9 0.35 2.4 3.1 2.6

1-butanol 4.0 3.4 2.2 1.7 2.4 0.42 1.6 1.9 2.4 2.5 2.6

2-methoxyethanol 4.0 3.4 2.0 2.8 2.7 1.1 1.2 2.5 2.6 2.9 2.6

a. %Change = percent change from Day Zero calculated as follows: (Day X mean concentration – Day Zero mean concentration) / Day Zero 

mean concentration * 100%, where X is the analysis day.
34

Table 14. Initial Demonstration of Capability (IDC) Quality Control Requirements

Method 

Reference

Requirement Specification and Frequency Acceptance Criteria

Section 

9.1

Optimize SPE 

cartridge drying

parameters

For each extraction format Extract must be visibly dry. Retention 

times must match those observed for

calibration standards.

Section 

9.2.1

Demonstration 

of low system 

background

Analyze a Laboratory Reagent Blank

after the high calibration standard 

during the IDC calibration.

Demonstrate that all method analytes 

are less than one-third of the Minimum 

Reporting Level (MRL).

Section 

9.2.2

Demonstration 

of precision

Extract and analyze 5 replicate 

Laboratory Fortified Blanks (LFBs)

near the mid-range concentration.

Percent relative standard deviation 

must be ≤20%.

Section 

9.2.3

Demonstration 

of accuracy

Calculate mean recovery for 

replicates used in Section 9.2.2.

Mean recovery within ±30% of the true 

value.

Section 

9.2.4

MRL 

confirmation

Fortify and analyze 7 replicate LFBs 

at the proposed MRL concentration. 

Confirm that the Upper Prediction 

Interval of Results (PIR) and Lower 

PIR meet the recovery criteria.

Upper PIR ≤150%

Lower PIR ≥50%

Section 

9.2.5

Quality Control 

Sample (QCS)

Analyze mid-level QCS. Results must be within ±20% of the 

true value.

Table 15. Ongoing Quality Control Requirements

Method 

Reference

Requirement Specification and Frequency Acceptance Criteria

Section 

10.1.1

Bromofluorobenzene 

(BFB) Tune Check

1μg/mL in elution solvent in full 

scan mode with each initial 

calibration, or after major mass 

spectrometer service.

Table 1, Section 17

Section 

10.2

Initial calibration Use the internal standard 

calibration technique to generate 

a linear or quadratic calibration 

curve. Use at least 6 standard 

concentrations. Evaluate the 

calibration curve as described in 

Section 10.2.3.

When each calibration standard is 

calculated as an unknown using the 

calibration curve, the lowest level 

standard should be within ±50% of 

the true value. All other points 

should be within ±30% of the true 

value.

Section 

9.3.1

Laboratory Reagent 

Blank (LRB)

Include one LRB with each 

Extraction Batch. Analyze one LRB 

with each Analysis Batch.

Demonstrate that all method 

analytes are below one-third the 

Minimum Reporting Level (MRL), 

and that possible interference from 

reagents and glassware do not 

prevent identification and 

quantitation of method analytes.
35

Method 

Reference

Requirement Specification and Frequency Acceptance Criteria

Section 

9.3.3

Laboratory Fortified 

Blank

Include one LFB with each 

Extraction Batch.

For analytes fortified at 

concentrations ≤2 x the MRL, the 

result must be within ±50% of the 

true value; ±30% of the true value if 

fortified at concentrations greater 

than 2 x the MRL.

Section 

10.3

Continuing 

Calibration Check 

(CCC)

Verify initial calibration by 

analyzing a low-level CCC at the 

beginning of each Analysis Batch. 

Subsequent CCCs are required 

after every tenth field sample and 

to complete the batch.

The lowest level CCC must be within 

±50% of the true value. All other 

points must be within ±30% of the 

true value.

Section 

9.3.5

Internal standards 

(IS)

Internal standards are added to all 

standards and sample extracts.

Peak area counts for each IS must 

be within ±30% of the area in the 

most recent CCC, and ±50% of the 

average peak area in the initial 

calibration.

Section 

9.3.6

Surrogate analytes Surrogates are added to all field 

samples and QC samples prior to 

extraction.

70% to 130% recovery

Section 

9.3.7

Laboratory Fortified 

Sample Matrix 

(LFSM)

Include one LFSM per Extraction 

Batch. Fortify the LFSM with 

method analytes at a 

concentration close to but greater 

than the native concentrations (if 

known).

For analytes fortified at 

concentrations ≤2 x the MRL, the 

result must be within ±50% of the 

true value; ±30% of the true value if 

fortified at concentrations greater 

than 2 x the MRL.

Section 

9.3.8

Laboratory Fortified 

Sample Matrix 

Duplicate (LFSMD) or 

Field Duplicate (FD)

Include at least one LFSMD or FD 

with each Extraction Batch.

For LFSMDs or FDs, relative percent 

differences must be ≤30% (≤50% if 

concentration ≤2 x the MRL).

Section 

9.3.9

QC failures 

associated with 

retention time shifts

Evaluate retention times for 

analytes, surrogates, and internal 

standards failing QC criteria.

Retention times of the method 

analytes must be within the 

windows determined using dry 

calibration standards (Sect. 12.1). 

SPE drying procedures must be 

optimized for each extraction 

format (Sect. 9.1).

Section 

9.3.10

Quality Control 

Sample (QCS)

Analyze a QCS at least quarterly. Results must be ±20% of the true 

value.
36

Figure 1. Drying apparatus and proper placement of rotameter in flow path
37

Figure 2. Reconstructed ion chromatogram (RIC), SIM mode, for calibration standard
38

Figure 3. Extracted ion current profiles for calibration standard; concentrations as listed
39

Figure 4. RIC, SIM mode, for unfortified drinking water from a surface water source
40

Figure 5. RIC, SIM mode, for unfortified drinking water from a ground water source