METHOD 524.4 MEASUREMENT OF PURGEABLE 

ORGANIC COMPOUNDS IN WATER 

BY GAS CHROMATOGRAPHY/MASS 

SPECTROMETRY USING NITROGEN 

PURGE GAS
Questions concerning this document should be addressed to: 

Steven C. Wendelken, PhD

U.S. EPA, OGWDW/SRMD/TSC, 26 W. Martin Luther King Dr. Cincinnati, OH 45219 

Phone: (513) 569-7491 

wendelken.steve@epa.gov

Office of Water (MS-140)

EPA 815-R-13-002

May 2013
Foreword

This method was prepared under the direction of David J. Munch and Steven C. Wendelken, PhD of the 

Technical Support Center within the U.S. EPA Office of Water. Shaw Environmental Inc. provided 

support under EPA contracts EP-C-06-031and EP-C-12-013. The following are acknowledged for their 

support in development of this method:

Tom Hartlein, Tekmar (Teledyne Technologies, Inc.)

Roger Bardsley, Tekmar (Teledyne Technologies, Inc.)

Laura Chambers, OI Analytical

John George, Bruker Corporation

Yongtao Li, Underwriters Laboratories, Inc.

Bill Davis, Underwriters Laboratories, Inc.

Dr. Andrew Eaton, Eurofins Eaton Analtyical

Kipp Phelan, Eurofins Eaton Analytical
524.4-1

METHOD 524.4

MEASUREMENT OF PURGEABLE ORGANIC COMPOUNDS IN WATER BY GAS 

CHROMATOGRAPHY/MASS SPECTROMETRY USING NITROGEN PURGE GAS

1. SCOPE AND APPLICATION

1.1 This is a gas chromatography/mass spectrometry (GC/MS) method for the determination of 

purgeable organic compounds in finished drinking waters. Discontinuous scanning modes 

such as selected ion monitoring (SIM) and selected ion storage (SIS) are permitted for 

determining selected analytes that are monitored at levels too low for the full scan detection 

mode. Precision and accuracy data have been generated for the method analytes in reagent 

water, drinking water from a groundwater source and drinking water from a surface water

source. The single laboratory Lowest Concentration Minimum Reporting Level (LCMRL) 

has also been determined in reagent water. The following compounds can be determined 

using this method:

Analyte

Chemical Abstract Services Registry 

Number (CASRN)

1,1,1,2-tetrachloroethane 630-20-6

1,1,1-trichloroethane 71-55-6

1,1,2,2-tetrachloroethane 79-34-5

1,1,2-trichloroethane 79-00-5

1,1-dichloroethane 75-34-3

1,1-dichloroethene 75-35-4

1,1-dichloropropene 563-58-6

1,2,3-trichlorobenzene 87-61-6

1,2,3-trichloropropane 96-18-4

1,2,4-trichlorobenzene 120-82-1

1,2,4-trimethylbenzene 95-63-6

1,2-dibromo-3-chloropropane 96-12-8

1,2-dibromoethane 106-93-4

1,2-dichlorobenzene 95-50-1

1,2-dichloroethane 107-06-2

1,2-dichloropropane 78-87-5

1,3,5-trimethylbenzene 108-67-8

1,3-butadiene 106-99-0

1,3-dichlorobenzene 541-73-1

1,3-dichloropropane 142-28-9

1,4-dichlorobenzene 106-46-7

1-chlorobutane 109-69-3

2-chlorotoluene 95-49-8

4-chlorotoluene 106-43-4
524.4-2

Analyte

Chemical Abstract Services Registry 

Number (CASRN)

4-isopropyltoluene 99-87-6

allyl chloride 107-05-1

benzene 71-43-2

bromobenzene 108-86-1

bromochloromethane 74-97-5

bromodichloromethane 75-27-4

bromoform 75-25-2

bromomethane 74-83-9

carbon disulfide 75-15-0

carbon tetrachloride 56-23-5

chlorobenzene 108-90-7

chlorodifluoromethane 75-45-6

chloroform 67-66-3

chloromethane 74-87-3

cis-1,2-dichloroethene 156-59-2

cis-1,3-dichloropropene 10061-01-5

dibromochloromethane 124-48-1

dibromomethane 74-95-3

dichlorodifluoromethane 75-71-8

diethyl ether 60-29-7

diisopropyl ether (DIPE) 108-20-3

ethyl methacrylate 97-63-2

ethylbenzene 100-41-4

hexachlorobutadiene 87-68-3

hexachloroethane 67-72-1

isopropylbenzene 98-82-8

methyl acetate 79-20-9

methyl iodide 74-88-4

methylene chloride 75-09-2

methyl-t-butyl ether (MtBE) 1634-04-4

m-xylene 108-38-3

naphthalene 91-20-3

n-butylbenzene 104-51-8

n-propylbenzene 103-65-1

o-xylene 95-47-6

pentachloroethane 76-01-7

p-xylene 106-42-3

sec-butylbenzene 135-98-8

styrene 100-42-5

t-amyl ethyl ether (TAEE) 919-94-8
524.4-3

Analyte

Chemical Abstract Services Registry 

Number (CASRN)

t-amyl methyl ether (TAME) 994-05-8

t-butyl alcohol (TBA) 75-65-0

t-butyl ethyl ether (ETBE) 637-92-3

t-butylbenzene 98-06-6

tetrachloroethene 127-18-4

tetrahydrofuran 109-99-9

toluene 108-88-3

trans-1,2-dichloroethene 156-60-5

trans-1,3-dichloropropene 10061-02-6

trichloroethene 79-01-6

trichlorofluoromethane 75-69-4

vinyl chloride 75-01-4

1.2 The ranges for purge-and-trap parameters specified in Section 9.1 are applicable to the use of 

nitrogen purge gas; helium may not be used. The mass spectrometry conditions described in 

this method were developed using a gas chromatograph (GC) interfaced to a quadrupole mass 

spectrometer (MS).

1.3 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%. Single laboratory LCMRLs for the 

analytes in this method ranged from 0.10 to 0.62 microgram per liter (μg/L) in the full scan 

mode (Table 6). Single laboratory LCMRLs were also determined for selected analytes in the 

selected ion monitoring (SIM) mode (Table 10). The procedure used to determine the 

LCMRL is described elsewhere.1

1.4 Laboratories using this method are not required to determine LCMRLs, but they must

demonstrate that the minimum reporting level (MRL) for each analyte meets the requirements 

described in Section 9.2.4.

1.5 Detection limit (DL) is defined as the statistically calculated minimum concentration that can 

be measured with 99% confidence that the reported value is greater than zero.

2

 The DL is 

dependent on sample matrix, fortification concentration and instrument performance. Determining the DL for analytes in this method is optional (Sect. 9.2.6). DLs for method analytes 

fortified into reagent water ranged from 0.026 to 0.18 μg/L in the full scan mode. These 

values are presented in Table 6. DLs were also determined for selected analytes in SIM mode 

(Table 10).

1.6 This method is intended for use by analysts skilled in the technique of purge-and-trap 

concentration, the operation of GC/MS instrumentation and the interpretation of the 

associated data.

1.7 METHOD FLEXIBILITY – To accommodate technological advances in analytical 

instrumentation and techniques, the laboratory is permitted to modify purge-and-trap

parameters and the GC/MS conditions. Because the purge-and-trap technique has a 

significant number of analyst-chosen parameters and because it employs a procedural 
524.4-4

calibration, the authors have determined an acceptable range of purge-and-trap conditions that 

may be used (Sect. 9.1) and a means by which to evaluate method modifications (Sect. 9.4). 

Changes may not be made to sample collection and preservation (Sect. 8) or to the 

quality control (QC) requirements (Sect. 9). Modifications that are introduced solely in the 

interest of reducing cost or sample processing time, but result in poorer method performance, 

may not be used. The option to operate the MS in SIM or SIS mode is restricted to analytes 

that cannot be effectively analyzed in full scan mode, e.g., 1,2-dibromoethane and 1,2-

dibromo-3-chloropropane. The SIM detection mode should not be used to enhance analyte 

signal for instrumentation that is not properly optimized and maintained. Compliance 

monitoring for trihalomethanes (THMs) must be conducted in the full scan detection mode. 

In all cases where allowed method modifications are made, 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 (Tables 12 and 13) are met and verify method 

performance in real sample matrices (Sect. 9.4.4).

NOTE: This description of method flexibility is a brief summary. Additional specific detail 

is provided throughout the method, which supersedes the above general guidance.

2. SUMMARY OF METHOD

Headspace-free samples are collected in amber, glass vials with polytetrafluoroethylene (PTFE)-

faced septa. Samples are dechlorinated with ascorbic acid and the pH is adjusted with maleic acid. 

A 5.0-milliliter (mL) aliquot of the sample is transferred to a glass sparging vessel along with 

appropriate amounts of internal standard and quality control compounds. The method analytes are 

purged from the water using nitrogen and trapped on a sorbent material. After purging, the trap 

may be dry purged for a short period to remove water. The trap is then heated and backflushed with

GC carrier gas to transfer the analytes directly into the gas chromatographic inlet. The inlet is 

operated in the split mode in order to achieve the desired desorb flow rates and further reduce water

transmission. Analytes are transferred onto a capillary GC column, which is temperature 

programmed to optimize the separation of method analytes. Compounds eluting from the GC are 

directed into a mass spectrometer for detection and quantitation. The method analytes are identified 

by comparing the acquired mass spectra and retention times to reference spectra and retention 

times. The concentration of each analyte is calculated using the internal standard technique and 

response curves obtained via procedural calibration (Sect. 3.18).

3. DEFINITIONS

3.1 ANALYSIS BATCH – A sequence of samples, analyzed within a 24-hour period, including

no more than 20 field samples. Each Analysis Batch must also include all required QC 

samples, which do not contribute to the maximum field sample total of 20. The required QC 

samples include:

Laboratory Reagent Blank (LRB),

Continuing Calibration Check (CCC) Standards,

Laboratory Fortified Sample Matrix (LFSM) and

Laboratory Fortified Sample Matrix Duplicate or Field Duplicate (LFSMD or FD).
524.4-5

3.2 CALIBRATION STANDARD – An aqueous solution of the method analytes prepared from

the Primary Dilution Standard solution. The calibration standard solutions are used to 

calibrate the instrument response with respect to analyte concentration.

3.3 CONTINUING CALIBRATION CHECK (CCC) – A calibration standard containing the 

method analytes, internal standards and surrogate analytes, which is analyzed periodically to 

verify the accuracy of the existing calibration.

3.4 DESORB FLOW RATE – The rate at which gas is passed through the sorbent trap during the 

desorb cycle. The desorb flow rate is approximately equal to the total flow rate through the 

GC inlet (mL/min).

3.5 DETECTION LIMIT (DL) – The minimum concentration of an analyte that can be identified, 

measured and reported with 99% confidence that the analyte concentration is greater than 

zero. This is a statistical determination (Sect. 9.2.6) and accurate quantitation is not expected 

at this level.

3.6 DRY PURGE VOLUME – The total volume of purge gas (mL) bypassing the sparging vessel 

and passing through the sorbent trap during the dry purge cycle (used as a moisture control 

measure).

3.7 FIELD DUPLICATE (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 FDs. For the purposes of this method, 

FDs 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. FDs are used to prepare Laboratory Fortified Sample Matrix (Sect. 3.11) and 

Laboratory Fortified Sample Matrix Duplicate (Sect. 3.12) QC samples. 

3.8 FIELD REAGENT BLANK (FRB) – An aliquot of reagent water that is placed in a sample 

container in the laboratory and treated as a sample in all respects, including shipment to the 

sampling site, exposure to sampling site conditions, storage, preservation and all analytical 

procedures. The purpose of the FRB is to determine if method analytes or other interferences 

are introduced into the samples during transport and storage.

3.9 INTERNAL STANDARD (IS) – A pure compound added to all standard solutions, field 

samples and QC samples in a known amount. Each internal standard is assigned to a specific 

analyte or multiple analytes and is used to measure relative response.

3.10 LABORATORY FORTIFIED BLANK (LFB) – An aliquot of reagent water to which known 

quantities of the method analytes are added. The LFB is analyzed in the same manner as a 

sample, including the preservation procedures in Section 8. The LFB is used during the Initial 

Demonstration of Capability to verify method performance for precision and accuracy.

3.11 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – A FD to which known 

quantities of the method analytes are added. The LFSM is processed and analyzed as a

sample and its purpose 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.
524.4-6

3.12 LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE (LFSMD) – A second FD, 

of the same sample used to prepare the LFSM, which is fortified identically to the LFSM. 

The LFSMD is used instead of the FD to assess method precision and accuracy when the 

occurrence of the method analytes is infrequent. For this method, separate field samples are 

required for preparing fortified matrix so that sampling error is included in the precision 

estimate.

3.13 LABORATORY REAGENT BLANK (LRB) – An aliquot of reagent water containing the 

preservatives, internal standards and surrogate analytes. The LRB is used to determine if the 

method analytes or interferences are introduced from the laboratory environment, the reagents 

or glassware. The LRB is also used to test for cross contamination in the purge-and-trap 

system.

3.14 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

3.15 MATERIAL SAFETY DATA SHEETS (MSDS) – 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.

3.16 MINIMUM REPORTING LEVEL (MRL) – The minimum concentration that can be reported 

by a laboratory as a quantified value for the method analyte in a sample following analysis. 

This concentration must meet the criteria defined in Section 9.2.4 and must be no lower than 

the concentration of the lowest calibration standard for each method analyte.

3.17 PRIMARY DILUTION STANDARD (PDS) – A solution containing the method analytes (or 

internal standards and surrogate analytes) prepared in the laboratory from Stock Standard 

Solutions and diluted as needed to prepare calibration standards and sample fortification

solutions.

3.18 PROCEDURAL CALIBRATION – A calibration technique in which calibration standards are 

processed through the entire method, including sample preparation, addition of preservatives, 

extraction and concentration.

3.19 PURGE FLOW RATE – The rate (mL/min) that the purge gas flows through the sparging 

vessel during the purge cycle.

3.20 PURGE VOLUME – The total volume of purge gas (mL) that flows through the sparging

vessel during the purge cycle.

3.21 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.

3.22 REAGENT WATER – Purified water that does not contain any measurable quantity of the 

method analytes or interfering compounds at or above 1⁄2 the MRL.
524.4-7

3.23 STOCK STANDARD SOLUTION (SSS) – A concentrated solution containing one or more 

of the method analytes that is prepared in the laboratory using assayed reference materials or 

purchased from a reputable commercial source, so that the concentration and purity of 

analytes are traceable to certificates of analysis.

3.24 SURROGATE ANALYTE – A pure analyte which is extremely unlikely to be found in any 

sample and which is added to a sample aliquot in a known amount before analysis. Surrogates 

are measured with the same procedures used to measure other sample components. Because 

surrogates are present in every sample, they provide a means of assessing method 

performance for a specific purge-and-trap analysis cycle.

4. INTERFERENCES

4.1 SAMPLE CONTAINERS, SHIPPING AND STORAGE – Volatile organic compounds 

(VOCs) present in ambient air, shipping containers and in the laboratory environment may 

permeate the PTFE-lined septa of the sample vials or be present at high concentrations in the 

headspace of the vial (especially if the vials were prepared in a laboratory). Contamination 

from these sources is evaluated by analyzing FRBs as described in Section 9.3.9.

4.2 PURGE-AND-TRAP SYSTEM – Commercially available purge-and-trap concentrators and 

autosamplers have complex sample paths that are subject to cross contamination, which is 

commonly referred to as “carryover.” Carryover is controlled by minimizing the transfer line 

length from the autosampler to the sparging vessel and optimizing the bake cycle and rinse

cycle parameters. The potential for carryover in the purge-and-trap system is evaluated during 

the Initial Demonstration of Capability by analyzing the highest concentration calibration 

standard followed by a LRB.

4.3 REAGENTS – All laboratory reagents must be routinely demonstrated to be free of

interferences under the conditions of the analysis. This may be accomplished by analyzing 

LRBs and meeting the acceptance criterion as described in Section 9.3.1.

4.3.1 REAGENT WATER – Analysts may observe common laboratory contaminants, such 

as methylene chloride, in reagent water. Boiling and/or sparging reagent water with 

nitrogen is recommended. If possible, prepare aqueous standards and blanks in a 

laboratory environment isolated from ambient sources of VOCs. 

4.3.2 METHANOL – Traces of ketones, methylene chloride and other organic solvents 

could be present in methanol. Use purge-and-trap-grade methanol with this method.

4.3.3 PRESERVATION REAGENTS – The potential exists for trace-level organic 

contaminants in the preservation reagents. Interferences from these sources must be 

monitored by analysis of LRBs when new lots of reagents are acquired.

4.3.4 SORBENT MATERIALS – Sorbent traps must be carefully evaluated because some 

traps, when heated, have been reported to produce small amounts of VOCs, 

particularly with extended use. For example, toluene may be detected the first time a 

trap is desorbed during a work shift. For this reason, a short bake cycle prior to 

beginning an analysis sequence is recommended. In addition, carbon-based traps, 
524.4-8

recommended for use with nitrogen purge by this method (Section 6.8.2), commonly 

produce chloromethane and bromomethane when heated. This phenomenon is caused 

by the reaction of methanol with the adsorbent materials when the trap is heated in

the desorb mode. The quantity of methanol used to prepare aqueous samples should 

be minimized and background levels of chloromethane and bromomethane should be 

carefully monitored in LRBs analyzed with each Analysis Batch. Background levels 

may preclude quantitation of these two analytes in SIM mode.

4.3.5 PURGE GAS SUPPLY – Nitrogen used to purge samples is a potential source of 

contamination. Trace VOCs in the purge gas, supply lines or the gas supply system 

(including the regulator) can concentrate on the sorbent trap. High-purity gas 

supplies and high-purity gas regulators are recommended to minimize contamination 

from these sources. Purge gas filters should be regenerated or replaced at the 

intervals specified by the manufacturers.

4.4 MATRIX INTERFERENCES – Matrix interferences are caused by contaminants that are 

present in the sample. The extent of matrix interferences will vary considerably from source 

to source depending upon the nature of the water. The analysis of LFSM (Sect. 9.3.7) 

provides evidence for the presence (or absence) of matrix effects.

5. SAFETY

5.1 The toxicity or carcinogenicity of each reagent used in this method has not been precisely 

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

chemicals should be minimized. Each laboratory is responsible for maintaining an awareness 

of OSHA regulations regarding safe handling of chemicals used in this method.3 A reference 

file of MSDSs should be made available to all personnel involved in the analysis.

5.2 Pure standard materials and Stock Standard Solutions of the method compounds should be 

handled with suitable personal protection equipment.

4

6. EQUIPMENT AND SUPPLIES

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

endorsement of the product. These references do not preclude the use of other vendors or supplies.

6.1 SAMPLE CONTAINERS – Clean, amber volatile organic analysis (VOA) vials fitted with 

PTFE-faced silicone septa and polypropylene screw caps (I-Chem Cat. No. S146–0040 or 

equivalent). 

6.2 MICRO SYRINGES – Suggested sizes include 2.0, 5.0, 10 and 25 μL.

6.3 PURGE-AND-TRAP SYRINGES – 5-mL glass syringes with PTFE Luer-Lok fitting

(Hamilton Model No. 1005 TLL or equivalent) for manual loading of samples into a sparging

vessel.

6.4 SYRINGE VALVE – two-position syringe valves with Luer ends (Supelco Cat. No. 20926 or 

equivalent) for use in sealing purge-and-trap syringes (Sect. 6.3).
524.4-9

6.5 VOLUMETRIC FLASKS – Class A, suggested sizes include 50, 100 and 200 mL for 

preparation of calibration standards.

6.6 ANALYTICAL BALANCE – Capable of weighing to the nearest 0.0001 gram (g).

6.7 MICRO-REACTION VESSEL – 0.3-, 1.0-, 2.0-, 5.0-mL sizes (Supelco Cat Nos. 33291, 

33293, 33295, 33299 or equivalent) equipped with Mininert Valves [Supelco Cat No. 33301

(15 millimeter (mm) for 0.3-, 1.0- and 2.0-mL vials) and Cat No. 33303 (20 mm for 5.0-mL 

vials)]. These vials are recommended for storage of Stock Standard Solutions and Primary 

Dilution Standards (PDS) prepared in methanol.

6.8 PURGE-AND-TRAP SYSTEM – Any purge-and-trap unit that is capable of being 

electronically interfaced to the GC and that is capable of meeting the method QC 

requirements outlined in Section 9 is permitted. The concentrator(s) may be equipped with an 

autosampler. Moisture control modules are permitted but not required.

6.8.1 SPARGING VESSEL – Instruments must be equipped with a sparging vessel 

specifically designed for purging a 5-mL sample volume. A glass frit should be 

installed at the base of the sample chamber so the purge gas passes through the water 

column as finely divided bubbles with a diameter of less than 3 mm at the origin.

NOTE: Larger sparging vessels are not allowed. While the larger sample volume 

could result in the transfer of more analyte to the trap, purging efficiency decreases 

unless the purge volume is increased proportionally. While the procedural calibration 

technique corrects for this, lower purging efficiency decreases method precision. In 

addition, larger purge volumes could result in the transfer of more water vapor to the 

trap, placing increased demand on moisture control strategies.

 

6.8.2 SORBENT TRAP – Purge-and-trap manufacturers typically recommend specific 

sorbent traps for use with their instruments. Any trap design is acceptable provided 

the data acquired meet all QC criteria described in Section 9.

During method development studies using nitrogen purge, traps containing Tenax, 

silica gel and coconut charcoal in series yielded lower recoveries for most of the 

method analytes when compared directly to the recoveries obtained using a helium 

purge. A trap containing Tenax, silica gel and carbon molecular sieve (CMS) 

exhibited similar poor performance. Thus, traps containing Tenax, silica gel and 

coconut charcoal or Tenax, silica gel and CMS may not be used in this method. 

Traps containing synthetic carbon adsorbent media (Supelco Vocarb® 3000 or

equivalent) are recommended for use with this method.

6.8.3 TRANSFER LINE – Silcosteel® or equivalent heated transfer line used to transfer the 

desorbed analytes from the purge-and-trap concentrator to the injection port of the 

GC. 

6.8.4 SAMPLE HEATER – A sparging vessel heater is optional. Resistance or infrared 

heaters may be used.
524.4-10

6.8.5 REFRIGERATED AUTOSAMPLER – Vial autosamplers must be capable of 

maintaining samples at a temperature of 10 °C or lower. Verify the temperature of 

field samples placed in the autosampler using an external thermocouple or 

thermometer (inserted into a vial containing water) during the IDC and at least 

quarterly. This temperature must not be altered after collecting the initial calibration 

because it may change analyte purging efficiencies.

6.8.6 STANDARD ADDITION MODULE – Automated device incorporated into vial 

autosamplers capable of fortifying internal standards and surrogate analytes directly 

into the sparging vessel. A standard addition module is recommended when vial 

autosamplers are used in the method.

6.8.7 TANDEM PURGE-AND-TRAP OPERATION – A technique allowing use of two 

purge-and-trap concentrators configured in tandem. The IDC procedure (Sect. 9.2)

must be conducted for each concentrator. In addition, this option requires separate

QC samples for each sample path (Sect. 9.3), separate calibrations (Sect. 10) and the 

use of a marker compound (Sect. 10, Note) to uniquely identify the sample path.

6.9 GAS CHROMATOGRAPHY MASS SPECTROMETRY SYSTEM/DATA SYSTEM 

(GC/MS/DS)

6.9.1 GC INJECTOR AND OVEN – The GC must be capable of temperature programming 

and must be equipped with a standard split/splitless injector and a flow controller that 

is compatible with purge-and-trap analysis. In this configuration, the purge-and-trap 

effluent is plumbed directly to the carrier gas inlet line of a split/splitless injection 

port. The injection port is operated in split mode to achieve the desired desorb flow 

rate and reduce water transmission. A deactivated glass liner (Restek Cat. No. 20972 

or equivalent) is recommended to minimize dead volume and active sites within the

GC inlet.

6.9.2 FUSED SILICA CAPILLARY GC COLUMN – Laboratories must use a column 

specifically designed for analysis of volatile organic compounds by purge-and-trap.

The column must have an i.d. of 0.32 mm or less to be compatible with operation in 

the split mode (Sect. 6.9.1). The column must be capable of resolving the method 

analytes so that a unique quantitation ion is available for each analyte.

 

6.9.3 GC/MS INTERFACE – The mass spectrometer must have sufficient vacuum 

pumping capacity to allow the direct feed of the analytical column to the ion source.

6.9.4 MASS SPECTROMETER (MS) – The MS must be capable of electron ionization 

(EI) at a nominal energy of 70 electron volts (eV) and must be operated in the 

positive ion mode. An ion-trap mass spectrometer, tuned to produce mass spectra 

that approximate standard, library spectra obtained under EI conditions, may be used. 

The instrument must be capable of obtaining at least six scans during the elution of 

each chromatographic peak. Seven to ten scans across chromatographic peaks are 

recommended. The spectrometer must produce a mass spectrum that meets all 

criteria in Table 1 when 4-bromofluorobenzene (BFB) is introduced into the GC/MS 

(Sect. 10.1.1).
524.4-11

6.9.5 DATA SYSTEM – An interfaced data system is required to acquire, store, reduce and

output mass spectral data. The computer software must have the capability of 

processing stored GC/MS data by recognizing a GC peak within any given retention 

time window, comparing the mass spectra from the GC peak with spectral data in a 

user-created data base and generating a list of tentatively identified compounds with 

their retention times and scan numbers. The software must allow integration of the 

ion abundance of any specific ion between specified time or scan number limits. The 

software must also allow construction of linear or second-order regression calibration 

curves and calculation of concentrations using the internal standard technique.

7. REAGENTS AND STANDARDS

7.1 REAGENTS AND SOLVENTS – Reagent grade or better chemicals must be used. Unless 

otherwise indicated, all reagents should conform to the specifications of the Committee on 

Analytical Reagents of the American Chemical Society (ACS), when such specifications are 

available. Other grades may be used as long as the reagent is of sufficiently high purity to 

permit its use without negatively affecting data quality. 

7.1.1 HELIUM – Ultra High Purity (99.999%) or equivalent, for use as GC carrier gas.

7.1.2 NITROGEN – Ultra High Purity (99.999%) or equivalent, for use as purge gas.

7.1.3 REAGENT WATER – Purified water which does not contain any measurable 

quantities of any method analytes or interfering compounds at or above 1⁄2 the MRL 

for each compound of interest.

7.1.4 METHANOL (CH3OH, CAS# 67-56-1) – Purge-and-trap grade, demonstrated to be 

free of analytes and interferences (Burdick & Jackson Brand® for Purge-and-trap

Analysis Cat. No. 232 or equivalent).

7.1.5 ASCORBIC ACID (C6H8O6, CAS# 50-81-7) – Dechlorinating agent, demonstrated to 

be free of analytes and interferences (Alfa Aesar Cat. No. A15613 or equivalent).

7.1.6 MALEIC ACID (C4H4O4, CAS# 110-16-7) – Used as a preservative and to lower pH 

for the purpose of preventing dehydrohalogenation of chlorinated analytes. High 

purity, demonstrated to be free of analytes and interferences (Sigma Cat. No. M0375 

or equivalent).

7.1.7 SODIUM THIOSULFATE (Na2S2O3, CAS# 7772-98-7) – Optional dechlorinating 

agent when sampling only for THMs (Sigma Cat. No. 563188 or equivalent).

7.2 STOCK STANDARD SOLUTIONS – Certified mixes of the 524.4 method analytes, the 

internal standards and the surrogate analytes are recommended. Users may prepare stock 

standards of the liquid and solid analytes, if not available as certified solutions, following the 

guidance provided in this section. After opening the sealed ampoules, store commercial

mixes in micro-reaction vials with Mininert caps (Sect. 6.7) at a temperature of -10 °C or 

lower. After transfer replace vendor-supplied stock solutions within one month.
524.4-12

NOTE: Methyl iodide may degrade faster than other liquid analytes. Monitor the area of this 

compound relative to the internal standard, 1, 4-difluorobenzene. Replace the stock standard 

if methyl iodide shows evidence of degradation.

7.2.1 INTERNAL STANDARD STOCK SOLUTIONS (ISSS) (1000 to 2500 μg/mL) –

This method uses three internal standards: 1,4-difluorobenzene (CAS# 540-36-3), 

chlorobenzene-d5 (CAS# 3114-55-4) and 1,4-dichlorobenzene-d4 (CAS# 3855-82-1). 

7.2.2 SURROGATE STOCK STANDARDS (SURSS) (1000 to 2500 μg/mL) – This 

method uses three surrogate analytes: methyl-t-butyl-ether-d3 (CAS# 29366-08-3), 

bromofluorobenzene (BFB) (CAS# 460-00-4) and 1,2-dichlorobenzene-d4 (CAS#

2199-69-1).

7.2.3 ANALYTE STOCK STANDARD SOLUTIONS – Obtain the analytes listed in the 

table in Section 1.1 as certified mixes in methanol or as neat standards if necessary. 

7.2.4 PREPARATION INSTRUCTIONS FOR LIQUID ANALYTES – Prepare the stock 

standards individually at 10 mg/mL. Using an analytical balance, obtain a tare weight 

for a VOA vial containing 20-mL of purge-and-trap-grade methanol. To achieve the

10 mg/L nominal concentration, calculate the volume of the liquid analyte 

corresponding to 200 mg. Carefully measure this volume with a 250-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.

7.2.5 PREPARATION INSTRUCTIONS FOR SOLID ANALYTES - Prepare the stock 

standards individually at 10 mg/mL by weighing 200 mg of each solid analyte into a 

40-mL VOA vial and diluting to 20 mL with purge-and-trap-grade methanol. For 

semi-solid and other difficult to transfer materials, insert the entire weigh boat into a 

VOA vial containing 20-mL of methanol. If the measured mass of analyte is not 

exactly 200 mg, adjust the volume of methanol to achieve a nominal concentration of 

10 mg/mL. 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.

7.2.6 STORAGE OF INDIVIDUAL STOCK STANDARDS - Store stock standards in the 

VOA vials in which they were prepared. Stock standard solutions of liquid and solid 

analytes prepared in-house are estimated to be stable for at least six months if stored at 

-10 °C or colder. However, such solutions may be stable for longer periods depending 

on the analyte. Laboratories must use accepted QC practices to determine when stock 

standards need to be replaced. 

7.3 PRIMARY DILUTION STANDARDS (PDS) – Prepare Primary Dilution Standards by 

combining and diluting appropriate volumes of the stock standards with purge-and-trap-grade 

methanol.

7.3.1 INTERNAL STANDARD AND SURROGATE PRIMARY DILUTION 

STANDARD (IS/surrogate PDS) – Prepare a combined internal standard and 
524.4-13

surrogate PDS from the ISSS and SURSS. Field samples and calibration standards 

must contain the same concentration of internal standards and surrogates and the 

quantity of methanol added should be minimized. Between one and 5 μL per 5-mL 

sample is recommended. An IS/surrogate PDS concentration that results in the 

aqueous concentration falling in the mid-range of the initial calibration, e.g., 5 μg/L in 

full scan mode and 0.5 μg/L in SIM mode is recommended. Store the IS/surrogate 

PDS in a glass vial with Teflon-lined septa at a temperature of -10 °C or colder. 

However, if the autosampler has a sealed reservoir on the standard addition module

IS/surrogate PDS may be held at room temperature for extended periods (several 

months).

7.3.2 ANALYTE PRIMARY DILUTION STANDARD (analyte PDS) – The analyte PDS is 

used to prepare the calibration standards and to fortify LFBs, LFSMs and LFSMDs 

with the method analytes. The analyte PDS is prepared by combining appropriate 

volumes of the analyte stock standard solutions to achieve concentrations appropriate 

for preparing aqueous calibration standards and fortifying samples. Choose 

concentrations such that at least 2 μL of the PDS is transferred to achieve the desired 

aqueous concentration in the standard or QC samples; however, minimize the volume 

of methanol used. Methanol reacts to produce chloromethane and bromomethane 

when traps containing synthetic-carbon adsorbent materials are heated (Sect. 4.3.4).

During method development, PDS solutions ranged in concentration from 10 μg/mL to 

400 μg/mL. Lower concentrations of the analyte PDS may be necessary when 

conducting analyses in SIM mode. Store analyte PDS solutions in micro-reaction vials 

with Mininert caps at a temperature of -10 °C or colder. PDS solutions which contain 

gases must be replaced after one week; those which do not contain gases may be 

stored for up to one month.

7.4 CALIBRATION STANDARDS – Prepare procedural calibration standards by diluting the 

analyte PDS into reagent water containing the method preservatives (Sect. 8.1). A constant 

concentration of each internal standard and surrogate analyte is added to each calibration 

standard, either manually or by use of an automated standard addition module (Sect. 6.8.6). 

The lowest concentration calibration standard must be at or below the MRL. Additionally, 

these calibration standards may be used as CCCs. The dilution factors for calibration 

standards used to collect method performance data in Section 17 are provided in the tables 

below. 

Typical concentrations for aqueous calibration standards used during method development in 

full scan mode 

CALa Level Analyte PDS Conc. (μg/mL) Analyte PDS

Volume (μL) Final CAL Std. Volume (L) Final CAL Std. Conc.(μg/L)

1 10 5.0 0.100 0.50

2 10 10 0.100 1.0

3 100 2.0 0.100 2.0

4 100 5.0 0.100 5.0

5 400 2.5 0.100 10

6 400 5.0 0.100 20

7 400 10 0.100 40 a CAL = calibration standard.
524.4-14

Typical concentrations for aqueous calibration standards used during method development in 

SIM mode 

CAL Level Analyte PDS Conc. (μg/mL) Analyte PDS

Volume (μL) Final CAL Std. Volume (L) Final CAL Std. Conc.(ng/L)

1 0.1 10 0.100 10

2 1.0 2.5 0.100 25

3 1.0 5.0 0.100 50

4 1.0 10 0.100 100

5 10 2.0 0.100 200

6 10 5.0 0.100 500

7 10 10 0.100 1,000

7.5 GC/MS TUNE CHECK SOLUTION, BFB (CAS# 460-00-4) – Use the IS/surrogate analyte 

PDS (Sect. 7.3.1).

8. SAMPLE COLLECTION, PRESERVATION and STORAGE

8.1 SAMPLE COLLECTION

8.1.1 Prior to shipment to the field, ascorbic acid and maleic acid must be added to each 

sample bottle. Cap the vials tightly to avoid spillage of the preservation reagents. If 

using a 40-mL vial, add 25 mg of ascorbic acid and 200 mg of maleic acid. If other 

collection volumes are used, adjust the amount of the preservation reagents so that the 

final concentrations of ascorbic acid and maleic acid in the sample containers are 

0.625 g/L and 5 g/L, respectively. Using narrow-range pH paper, periodically verify 

that sample pH is ~2 for each sample source.

8.1.2 If a sample foams vigorously when added to a VOA vial containing maleic and 

ascorbic acids, discard the sample. Collect another sample for that location, but do 

not add the method preservatives. Document these samples as “not acidified.” 

Unpreserved samples must be analyzed within 24 hours of collection.

8.1.3 If sampling only for the THMs, samples may be preserved with sodium thiosulfate. 

Add 3 mg to each 40-mL VOA vial prior to sample collection. Do not add ascorbic 

or maleic acid when employing this preservation option.

NOTE: If the residual chlorine is likely to be present at greater than 5 mg/L, a 

determination of the chlorine concentration may be necessary. Add an additional 25 

mg of ascorbic acid or 3 mg of sodium thiosulfate per each 5 mg/L of residual 

chlorine for each 40-mL of sample.

8.1.4 Grab samples must be collected in accordance with standard sampling practices.5

 

When sampling from a cold water tap, remove the aerator, open the tap and allow the 

system to flush until the water temperature has stabilized (approximately 3 to 5 

minutes). Fill sample bottles to overflowing, but take care not to flush out the rapidly 

dissolving solid preservatives. No air bubbles should pass through the sample as the 

bottle is filled or be trapped in the sample when the bottle is sealed.
524.4-15

8.1.5 When sampling from an open body of water, fill a beaker with water collected from a 

representative area. Use this bulk sample to generate individual samples and Field 

replicates as needed.

8.2 FIELD REAGENT BLANK (FRB)

8.2.1 A FRB must accompany each sample set unless only THMs are being analyzed. At 

the laboratory, add the sample preservatives to the FRB sample bottle, fill with 

reagent water and ship the FRB with the sampling kits. Do not open the FRB in the 

field; the FRB must remain sealed until analysis. Since total THMs would be 

expected to be present in nearly all disinfected drinking water samples, field blank 

analysis is not required when reporting positive results for total THMs. This 

exception to the analysis of field blanks only applies to the analysis of total THMs as 

disinfection byproducts (DBPs). Positive results for all other chemicals observed 

must be accompanied by the analysis of a field blank to confirm that the positive 

result was not the result of contamination during sample handling or shipment.

8.2.2 Add the sample preservatives at the laboratory to prepare sample containers for the

field samples. The same lots of ascorbic acid and maleic acid must be used for the 

FRB and the field samples.

8.3 FIELD DUPLICATES – At a minimum, collect all samples in duplicate. Adequate replicate

samples in the analytical batch will need to be collected to fulfill QC requirements for LFSMs

and LFSMDs or FDs. 

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. Samples must be confirmed 

to be at or below 10 °C when they are received at the laboratory. In the laboratory, samples 

must be stored at or below 6 °C, protected from light and isolated from ambient sources of 

VOCs. When resident in the autosampler, samples must be held at 10 °C or lower. Samples 

must not be frozen.

8.5 SAMPLE HOLDING TIMES – Analyze samples as soon as possible. Samples that are 

collected and stored as described in Section 8.1 and 8.4 must be analyzed within 14 days of 

collection. 

9. QUALITY CONTROL

QC requirements include the Initial Demonstration of Capability 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, Tables 12 and 13. These QC requirements are considered

the minimum acceptable QC criteria. Laboratories are encouraged to institute additional QC 

practices to meet their specific needs. Compliance with the requirements of the IDC must be 

demonstrated for each analyte that the laboratory intends to report using full scan MS and for each 

analyte that the laboratory intends to report in the SIM or SIS detection mode.

9.1 METHOD MODIFICATIONS – The analyst is permitted to select purge-and-trap and GC

conditions appropriate for the available instrumentation. However, five key parameters are 
524.4-16

restricted to prescribed ranges. These ranges are summarized in the table below. If the 

chosen parameters fall within the “recommended” ranges, the laboratory may proceed with 

the IDC. If values outside the “recommended” ranges are selected for any one of these five

parameters, the laboratory must demonstrate equivalent performance in accordance with the 

guidelines provided in Section 9.4 and then the analyst must repeat the procedures of the IDC. 

However, values for the five key parameters must never exceed the “allowable” ranges listed 

in the table below. In addition, sample size cannot be varied from the 5-mL volume 

prescribed in this method. All other parameters including the remaining concentrator 

conditions, GC conditions and MS conditions may be varied without restriction. 

Parameter Recommended Allowable

Minimum Maximum Minimum Maximum

Sample temperature Ambient 40 oC Ambient 60 °C

Purge flow rate 40 mL/min 55 mL/min 20 mL/min 80 mL/min

Purge volume 360 mL 520 mL 320 mL 520 mL

Desorb time 1 min 1 min 0.5 min 2 min

Purge volume + dry purge volume 360 mL 720 mL 320 mL 720 mL

NOTE: The “recommended” values provided equivalent response factors and internal 

standard areas compared to helium purge. The “allowable” limits resulted in a wider variation 

in response factors compared to helium purge; however, operation within this range may be 

appropriate for limited analyte lists and other concentrator designs. Sample temperature is 

limited to 60 oC to avoid acid-catalyzed decomposition of method analytes. See Table 2 in 

Section 17 for typical values for purge-and-trap parameters.

9.2 INITIAL DEMONSTRATION OF CAPABILITY (IDC) – The IDC must be successfully 

performed prior to analyzing any field samples. Prior to conducting the IDC, the analyst must 

meet the calibration requirements outlined in Section 10. The IDC must be completed for 

each concentrator and trap. For example, if dual concentrators are interfaced to a single 

GC/MS, perform the IDC for each system. If a new trap is installed with sorbent materials 

different from the original trap, repeat the IDC. Requirements for the IDC are described in the

following sections and are summarized in Table 12.

9.2.1 DEMONSTRATION OF LOW SYSTEM BACKGROUND – Analyze a LRB. 

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

NOTE: The system must be checked for carryover by analyzing a LRB immediately 

following the highest calibration standard. If this LRB does not meet the criteria 

outlined in Section 9.3.1, then carryover is present and the cause must be identified 

and eliminated.

9.2.2 DEMONSTRATION OF PRECISION – Prepare and analyze seven replicate LFBs. 

Fortify these samples near the midrange of the initial calibration curve. The method 

preservation reagents must be added to the LFBs as described in Section 8.1. The 

percent relative standard deviation (%RSD) of the concentrations of the replicate 

analyses must be ≤20% for all method analytes.
524.4-17

100

AverageConcentration

Standard Deviation of Measured Concentrations % RSD = ×

9.2.3 DEMONSTRATION OF ACCURACY – Calculate the average percent recovery 

using the same set of replicate data generated for Section 9.2.2. The average recovery 

of the replicate analyses must be within +20% of the true value.

100

Fortified Concentration

AverageMeasured Concentration % Recovery = ×

9.2.4 MINIMUM REPORTING LEVEL (MRL) CONFIRMATION – Establish a target 

concentration for the MRL based on the intended use of the data. The lowest 

calibration standard used to establish the initial calibration (as well as the low-level 

Continuing Calibration Check) must be at or below the concentration of the MRL. 

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

QC requirements. Confirm the MRL following the procedure outlined below.

NOTE: Method analytes that are consistently present in the background (e.g., 

methylene chloride, TBA, chloromethane and bromomethane) should be reported as 

detected in field samples only after careful evaluation of the background levels. In 

such cases, an MRL must be established at a value no less than three times the 

standard deviation of the mean LRB concentration or three times the mean LRB 

concentration, whichever is greater. This guidance is intended to minimize the 

occurrence of reporting false positive results.

9.2.4.1 Fortify 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. Calculate the mean (Mean) and standard deviation 

(S) for these replicates. Determine the Half Range for the Prediction 

Interval of Results (HRPIR) using the equation below

HRPIR = 3.963S

where S is the standard deviation and 3.963 is a constant value for seven 

replicates.1

9.2.4.2 Confirm that the Upper and Lower limits for the Prediction Interval of 

Results (PIR = Mean + HRPIR) meet the upper and lower recovery limits as 

shown below.

The Upper PIR Limit must be ≤150% recovery.

Mean HR

FortifiedConcentration

PIR +

× 100 ≤ 150%

The Lower PIR Limit must be ≥50% recovery.
524.4-18

Mean HR

FortifiedConcentration

PIR − × 100 ≥ 50%

9.2.4.3 The MRL is validated if both the Upper and Lower PIR Limits meet the 

criteria described above. 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 mid-level Quality Control 

Sample (Sect. 9.3.10) to confirm the accuracy of the primary calibration standards.

9.2.6 DETECTION LIMIT DETERMINATION (optional) – While DL determination is 

not a specific requirement of this method, it may be required by various regulatory 

bodies associated with compliance monitoring. It is the responsibility of the 

laboratory to ascertain whether DL determination is required based upon the 

intended use of the data.

Analyses for this procedure must be done over at least three days. Prepare at least 

seven replicate LFBs. Fortify the LFBs at a concentration estimated to be near the 

DL. This fortification level may be estimated by selecting a concentration at two to 

five times the noise level. The method preservatives must be added to the samples as 

described in Section 8.1. Process the seven replicates through all steps of Section 11.

NOTE: If a data set used for the MRL confirmation step of the IDC meets these 

requirements, a DL may be calculated from the MRL confirmation data and no 

additional analyses are necessary.

Calculate the DL using the following equation:

DL = S x t(n-1,1-α = 0.99)

where

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

freedom (for seven replicate determinations, the Student’s t value 

is 3.143 at a 99% confidence level),

n = number of replicates and

S = standard deviation of replicate analyses.

NOTE: Do not subtract blank values when performing DL calculations.

9.3 ONGOING QC REQUIREMENTS – This section describes the ongoing QC procedures that 

must be followed when processing and analyzing field samples. Table 13 summarizes these 

requirements.

9.3.1 LABORATORY REAGENT BLANK (LRB) – Analyze a LRB with each Analysis 

Batch. The LRB must contain the method preservatives, the internal standards and

surrogate analytes at the same concentration used to fortify all field samples and 
524.4-19

calibration standards. Background from method analytes or contaminants that interfere with the measurement of method analytes must be less than 1⁄2 the MRL. If the 

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 LRB values from sample results 

is not permitted.

NOTE: 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, blank contamination levels may be estimated by 

extrapolation when the concentration is below the MRL.

NOTE: 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 are valid.

THMs are excluded from this requirement.

NOTE: The LRB test in the IDC may be particularly difficult to pass for compounds 

analyzed using the SIM detection mode. For analytes monitored in SIM mode, the 

laboratory should restrict the high calibration point to 1.0 or 2.0 μg/L and consider 

other techniques such as using a dedicated sparge vessel and more aggressive recycle 

parameters. If possible, select MRLs that allow monitoring goals to be achieved, but 

that are well above typical blank values.

9.3.2 CONTINUING CALIBRATION CHECK (CCC) – Analyze CCC standards at the 

beginning of each Analysis Batch, after every ten field samples and at the end of the 

Analysis Batch. See Section 10.2 for concentration requirements and acceptance 

criteria.

9.3.3 LABORATORY FORTIFIED BLANK (LFB) – Because this method utilizes 

procedural calibration standards, which are fortified reagent waters, there is no 

difference between the LFB and the CCC standards. Consequently, the analysis of a 

separate LFB is not required as part of the ongoing QC; however, the term “LFB” is 

used for clarity in the IDC.

9.3.4 MS TUNE CHECK – The procedure for conducting the MS Tune Check for BFB is 

found in Section 10.1.1. Acceptance criteria for the MS Tune Check are summarized 

in Section 17, Table 1. The MS Tune Check must be performed prior to establishing 

and/or re-establishing an initial calibration (Sect. 10.1) and each time a major change 

is made to the mass spectrometer. Daily BFB analysis is not required.

9.3.5 INTERNAL STANDARDS (IS) – The analyst must monitor the peak areas of the 

internal standards in all injections of the Analysis Batch. The IS responses (peak 

area) in any chromatographic run must not deviate from the response in the most 

recent CCC by more than +30% and must not deviate by more than +50% from the 
524.4-20

average area measured during initial analyte calibration. 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 If the IS criteria are met in the CCC but not the sample, reanalyze the 

sample (FD) in a subsequent Analysis Batch. If the IS area fails to meet the 

acceptance criteria in the FD, but passes in the most recent CCC, report the 

sample results as “suspect/matrix.”

9.3.5.2 If both the original sample and the CCC fail the IS criteria, take corrective 

action beginning with an extended bake cycle for the GC column and the 

concentrator trap. Area counts may decrease as the rate of water entering 

the mass spectrometer exceeds the capacity of the pumping system to 

remove it. Additional measures such as clipping the inlet side of the GC 

column and cleaning the MS source may be indicated. Verify the integrity 

of the IS solution and the fortification technique. Perform the appropriate 

instrument maintenance and then reanalyze the sample (FD) in a subsequent 

Analysis Batch. If the IS area fails to meet the acceptance criteria in the FD, 

but passes in the most recent CCC, report the sample results as 

“suspect/matrix.”

9.3.6 SURROGATE RECOVERY – The surrogate analytes are fortified into all calibration 

standards, field samples and QC samples prior to purge-and-trap analysis. Calculate 

the percent recovery (%R) for each surrogate using the following equation:

100

B

A %R ×



 



 =

where

A = calculated surrogate concentration for the QC or field sample and

B = fortified concentration of the surrogate.

9.3.6.1 Surrogate recovery must be in the range of 70% to 130%. When surrogate 

recovery from a field sample, blank or QC sample is less than 70% or 

greater than 130% check: 1) calculations to locate possible errors, 2) the 

integrity of the surrogate analyte solution and the fortification technique, 

3) contamination and 4) instrument calibration. Also, see corrective action 

options in Section 9.3.5.2. Correct the problem and reanalyze the sample in 

a subsequent Analysis Batch using the appropriate FD.

9.3.6.2 If the repeat analysis meets the surrogate recovery criterion, only report data 

for the FD.

9.3.6.3 If the FD fails the surrogate recovery criterion after corrective action has 

been taken, report all data for that sample as “suspect/surrogate recovery.”

9.3.7 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – Within each Analysis 

Batch, analyze a minimum of one LFSM. The native concentrations of the analytes 
524.4-21

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

measured values in the LFSM. If a variety of different sample matrices are analyzed 

regularly, for example, drinking water from ground water and surface water sources, 

performance data must be collected for each source.

9.3.7.1 Prepare the LFSM by fortifying a FD with an appropriate amount of an

analyte PDS (Sect. 7.3.2). Select a spiking concentration that is greater than 

or equal to the native background concentration, if known. 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 and rotate through low, medium and high calibration 

concentrations when selecting a fortifying concentration.

NOTE: If the presence of DBPs (e.g., THMs) precludes selection of an 

appropriate fortification level for the majority of the method analytes, the 

DBPs may be ignored. For example, if the analyst wishes to estimate 

accuracy and precision at 1.0 μg/L and chloroform is present in the native 

matrix at 10 μg/L, chloroform is fortified at only 10% of its native 

concentration. In such cases, recovery results for the DBPs may fail the 

acceptance criteria for LFSM. Appropriately qualify the QC result when 

this occurs. If the laboratory is analyzing specifically for DBPs or does not 

wish to exclude them, select a fortification level based on the DPB

concentrations in the native sample such that the final DBP results fall 

within the calibration range.

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

( ) 100

C

A - B %R = ×

where

A = measured concentration in the fortified sample

B = measured concentration in the unfortified sample and

C = fortification concentration.

9.3.7.3 Recoveries for samples fortified at concentrations near or at the MRL 

(within a factor of two times the MRL concentration) must be within +50% 

of the true value. Recoveries for samples fortified at all other concentrations 

must be within +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, the recovery is judged matrix biased. 

The result for that analyte in the unfortified sample is labeled 

“suspect/matrix.”

NOTE: 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. This 
524.4-22

situation and the LRB are the only permitted uses of analyte results below 

the MRL.

9.3.8 FIELD DUPLICATE OR LABORATORY FORTIFIED SAMPLE MATRIX 

DUPLICATE (FD or LFSMD) – Within each Analysis Batch, analyze a minimum of 

one FD or one LFSM Duplicate. If method analytes are not routinely observed in 

field samples, analyze an LFSMD rather than an FD.

9.3.8.1 Calculate the relative percent difference (RPD) for duplicate measurements 

(FD1 and FD2) using the equation:

( ) 100

FD FD /2

FD FD

RPD

1 2

1 2

×

+

− =

9.3.8.2 RPDs for FDs must be ≤30%. Greater variability may be observed when 

FDs have analyte concentrations that are near or at the MRL (within a factor 

of two times the MRL concentration). At these concentrations, FDs must

have RPDs that are ≤50%. If the RPD of an analyte falls outside the 

designated range and the laboratory performance for the analyte is in control 

in the CCC, the precision is judged matrix influenced. The result from the 

unfortified sample is labeled “suspect/matrix.”

9.3.8.3 If an LFSMD is analyzed instead of a FD, calculate the RPD for the LFSM 

and LFSMD using the equation:

9.3.8.4 RPDs for duplicate LFSMs must be ≤30%. Greater variability may be 

observed when fortified LFSMs have analyte concentrations that are near or 

at the MRL (within a factor of two times the MRL concentration). LFSMs 

at these concentrations must have RPDs that are ≤50%. If the RPD of an

analyte falls outside the designated range and the laboratory performance for 

that analyte is in control in the CCC, the precision is judged matrix

influenced. The result from the unfortified sample is labeled 

“suspect/matrix.”

9.3.9 FIELD REAGENT BLANK (FRB) – FRBs must be analyzed if compounds other 

than commonly occurring DBPs, such as THMs, are detected in field samples. 

Qualify the result for any analyte that is detected in both a field sample and in the 

associated FRB as “probable contribution from shipping and storage.” Subtracting 

FRB values from sample results is not permitted.

9.3.10 QUALITY CONTROL SAMPLE (QCS) – A QCS must be evaluated as part of the 

IDC and repeated at least quarterly. Fortify the QCS near the midpoint of the 

calibration range. The acceptance criteria for the QCS are the same as the mid-level

and high-level CCCs (Sect. 10.2.1). If the accuracy for any analyte fails the recovery 

( ) 100

LFSM LFSMD /2

LFSM LFSMD

RPD ×

+

− =
524.4-23

criterion, check the standard preparation process, stock standard sources and the 

purity of neat materials used to prepare the stock standards to locate and correct the 

problem.

9.4 METHOD MODIFICATION QC REQUIREMENTS – The analyst is permitted to modify the 

five key purge-and-trap parameters (sample temperature, purge flow rate, purge volume, 

desorb time and dry purge volume). The analyst is not permitted to modify sample collection 

or preservation, change the QC requirements of the method or increase the sample volume 

above 5 mL. Do not add or delete QC compounds from the list prescribed in the method: ISs 

(Sect. 7.2.1) and surrogates (Sect. 7.2.2). If modified parameters fall outside of the 

“recommended” minimum and maximum for one of the five key parameters the laboratory

must confirm that the new parameters provide acceptable method performance as defined in 

the following subsections.

9.4.1 The new parameters must fall within the “allowable” minimum and maximum limits 

specified in Section 9.1. Values outside these limits are not permitted.

9.4.2 Perform an initial calibration procedure (Sect. 10.1) for the method analytes that the 

laboratory intends to report using conditions that fall within the “recommended” 

ranges as presented in Section 9.1. Determine relative response factors (RRF) for 

each analyte averaged over the entire calibration range.

( ) ( )

IS(area) Analyte (μg/L)

Analyte area IS μg/L RRF

×

× =

9.4.3 Optimize the purge-and-trap system using the proposed method modifications. 

Analyze three mid-level calibration standards and calculate mean RRFs for each 

method analyte. If all of the response factors observed using the modified conditions 

are ≥70% of the initial calibration response factors obtained using the 

“recommended” method conditions (Sect. 9.4.2), then the modified method 

parameters are permitted. Repeat the procedures of the IDC (Sect. 9.2) employing the 

modified parameters.

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

proposed method modifications in real matrices that span the range of waters that the 

laboratory analyzes. This additional step is required because modifications that 

perform acceptably in the IDC, which is conducted in reagent water, could fail 

ongoing method QC requirements in real matrices. If, for example, the laboratory 

analyzes drinking water from both surface and ground water municipalities, this 

requirement can be accomplished by assessing precision and accuracy (Sects. 9.2.2 

and 9.2.3) in a surface water with moderate to high total organic carbon (e.g., 2 mg/L 

or greater) and a hard ground water [e.g., 250 mg/L as calcium carbonate (CaCO3)

equivalent or greater].

9.4.5 The results of Sections 9.4.3 and 9.4.4 must be appropriately documented by the 

analyst and should be independently assessed by the laboratory’s QA officer prior to 

analyzing field samples.
524.4-24

9.4.6 When implementing method modifications, it is the responsibility of the laboratory to 

closely review the results of ongoing QC and in particular, the results associated with 

the LFSM (Sect. 9.3.7), LFSMD (Sect. 9.3.8), CCCs (Sect. 9.3.2) and the IS area 

counts (Sect. 9.3.5). If repeated failures are noted, the modification must be 

abandoned.

10. CALIBRATION AND STANDARDIZATION

Demonstration and documentation of acceptable analyte calibration is required before performing 

the IDC (Sect. 9.2) and prior to analyzing field samples. Verification of the MS calibration and the 

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

performed. 

NOTE: For tandem concentrators or older systems that utilize multiple sparging vessels and/or 

traps, a separate calibration and all required QC samples must be analyzed on each sample path. In 

addition, a qualitative marker compound must be added to all samples to uniquely identify the 

sample path and ensure that samples are matched to the proper calibration and QC results. For 

example, fluorobenzene could be added to all samples analyzed on the second sample path of a 

tandem concentrator system.

10.1 PURGE-AND-TRAP GC/MS OPTIMIZATION AND INITIAL CALIBRATION – An initial 

calibration requires optimizing purge-and-trap and GC/MS conditions, confirming that the 

instrument meets the BFB tune check criteria and the preparation and analysis of at least 

seven calibration standards to determine the calibration curve. Calibration must be performed 

using peak areas and the internal standard technique. Calibration using peak heights and

external standard calibration are not permitted.

10.1.1 MS TUNE/MS TUNE CHECK– Calibrate the mass and abundance scales of the MS 

utilizing calibration compounds and procedures recommended by the manufacturer 

with any modifications necessary to meet tuning requirements. Introduce BFB (Sect. 

7.5) into the GC/MS system. Acquire a mass spectrum using the same scan range 

employed for full scan sample analyses. 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 scan(s) 

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 Table 1, the MS must be retuned to 

meet all criteria before proceeding with the initial calibration.

10.1.2 PURGE-AND-TRAP CONDITIONS – Establish purge-and-trap parameters 

following the manufacturer’s recommendations. Make sure that the sample 

temperature, purge flow rate, purge volume, desorb time and dry purge volume are 

within the “allowable” ranges specified in section 9.1. Optimize purge-and-trap 

parameters to maximize purging efficiency and minimize the transmission of water to 

the GC/MS system.

10.1.3 GC CONDITIONS – Establish GC operating conditions appropriate for the GC 

column dimensions by optimizing the split ratio and temperature program. Generally, 

the required split ratio is inversely proportional to column diameter. The user must 
524.4-25

balance the need to transfer enough of the method analytes to achieve the desired 

MRLs and the need to reduce water transmission from the purge-and-trap 

concentrator. The split ratio will also affect the chromatographic peak profile of the 

most volatile method analytes, commonly referred to as “gases.” Sufficient

resolution and symmetrical peak profiles with minimal tailing for these analytes must

be achieved to enable accurate and precise integration. A mass chromatogram of the 

gases obtained during method development is provided in Figure 1. The GC program 

must be optimized to provide adequate resolution of the method analytes as defined in 

the following subsections.

10.1.3.1 If possible, optimize chromatographic conditions such that a unique 

quantitation ion is available for each analyte that is free from interference 

due to an identical fragment ion in any co-eluting (or overlapping) peak(s).

10.1.3.2 If a unique quantitation ion of sufficient intensity to set the desired MRL is 

not available, overlap with an identical ion from an overlapping analyte is 

permitted, providing that at least a 50% valley between the mass peaks is 

achieved.

10.1.4 FULL SCAN MS CONDITIONS – Select a scan range that allows the acquisition of 

a mass spectrum for each of the method analytes, which includes all of the major 

fragments mass-to-charge ratio (m/z) 35 and above. However, during elution of the 

water/carbon dioxide peak, the analyst is permitted to begin the scan at m/z 45 to 

eliminate the appearance of these matrix components in the baseline.

10.1.5 SIM MS CONDITIONS – In SIM mode, choose one primary quantitation ion and at 

least one secondary ion. If possible, select a second confirmation ion. Additional 

ions may be monitored that demonstrate a unique characteristic in the mass spectrum 

such as a halogen cluster. Verify that the primary ion is free from interference (Sect. 

10.1.3.1 and Sect. 10.1.3.2) due to an identical fragment ion in any overlapping 

peak(s). 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 proper window during each Analysis Batch. Make this observation by viewing 

the mass chromatogram of the quantitation ion for each SIM analyte in the CCC 

analyzed at the beginning and end of each Analysis Batch. This requirement does not 

preclude continuous operation by sequencing multiple Analysis Batches; however, 

the entire Analysis Batch is invalid if one or more analyte peaks drift outside of 

designated SIM windows in either of these CCCs. For large analyte lists, minimize 

the number of ions monitored in each chromatographic window to ensure adequate 

sensitivity to meet the desired MRL. During method development, five SIM 

windows were used as indicated in Section 17, Table 5.

10.1.6 ALTERNATING FULL AND SIM SCAN MODES – Alternating full and SIM scan 

functions during a single sample acquisition is permitted if the minimum number of 

scans across each GC peak acquired in this mode is maintained, i.e., six scans as 

specified in Section 6.9.4 in each full and SIM scan modes.

10.1.7 CALIBRATION STANDARDS – Prepare a set of at least seven calibration standards

as described in Section 7.4. The lowest concentration of the calibration standards
524.4-26

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 (Sect. 9.2), i.e., 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. 

10.1.8 CALIBRATION – 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 inverse 

concentration-weighted quadratic curves. Suggested internal standard assignments

and quantitation ions for each method analyte evaluated in full scan mode are 

presented in Table 4. Suggested internal standard assignments and quantitation ions 

for each method analyte evaluated in SIM mode are presented in Table 5. 

NOTE: Because the surrogate analytes are added at a single concentration level to the 

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

10.1.9 FORCING ZERO – Forcing the calibration curve through the origin is not 

recommended. However, zero must be forced for method analytes (e.g., common 

laboratory contaminants and for carbon-based traps, potentially chloromethane and 

bromomethane) if they are consistently detected in the Laboratory Reagent Blanks. 

Forcing zero allows for a better estimate of the background level of blank 

contaminants. An accurate estimate of background contamination is necessary to set 

MRLs for method analytes when blank levels are problematic (Sect. 9.2.4).

10.1.10 CALIBRATION ACCEPTANCE CRITERIA – The initial calibration is validated by 

calculating the concentration of the analytes for each of the analyses used to generate 

the calibration curve by use of the regression equations. Calibration points that are 

≤MRL must calculate to be within +50% of their true value. All other calibration 

points must calculate to be within +30% of their true value. If these criteria cannot be 

met, the analyst will have difficulty meeting ongoing QC criteria. In this case, 

corrective action such as reanalyzing the calibration standards, restricting the range of 

calibration or performing instrument maintenance is recommended.

10.2 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.

10.2.1 Calculate the concentration of each analyte in the CCC. Each analyte in the CCC

fortified at ≤MRL must calculate to be within +50% of its true value. At all other 

levels, each analyte, including the surrogate analytes, must calculate to be within

+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 
524.4-27

are still within holding time must be reanalyzed after an acceptable calibration has 

been restored. 

10.2.2 REMEDIAL ACTION – Failure to meet QC performance criteria for CCCs requires 

remedial action. Acceptable method performance may be restored simply by 

recalibrating in accordance with the guidelines in Section 10.1 and verifying

sensitivity by analyzing a CCC at or below the MRL. Because of the volatile nature 

of the method analytes, PDS have limited shelf life. Prepare a fresh PDS and repeat 

the CCC before contemplating instrument maintenance. If internal standard and 

calibration failures persist, maintenance such as extended bake cycles for both the 

purge-and-trap concentrator and the GC/MS, clipping the GC column, replacing the 

concentrator trap and cleaning the MS source may be required. Following major 

maintenance, the analyst must return to the initial calibration step (Sect. 10.1).

11. PROCEDURE

Important aspects of this analytical procedure include proper sample collection and storage 

(Section 8), ensuring that the instrument is properly calibrated (Section 10) and that all required 

QC elements are included (Section 9). This method is designed for a 5-mL sample volume. The 

concentration of the internal standards and surrogate analytes must be the same in the samples as 

in the calibration standards. In the laboratory, maintain field samples, QC samples and calibration 

standards at or below 6 °C at all times while in storage. While resident in the autosampler 

awaiting analysis, samples must be maintained at less than or equal to 10 °C. Do not store samples 

in the autosampler longer than the time required to complete the Analysis Batch.

11.1 SAMPLE PREPARATION: SYRINGE METHOD – For concentrators with a single 

sparging vessel and autosamplers with multiple sparging vessels, load the sample (or 

previously prepared calibration standard) by use of a 5-mL syringe. If the purge cycle will 

be initiated immediately after this step, warm the sample to room temperature. Remove the 

plunger from two syringes and attach a closed syringe valve. Open the VOA vial and

carefully pour the sample into the syringe barrel to just short of overflowing. Replace the 

syringe plunger, invert the syringe and compress the sample. Open the syringe valve and

vent any residual air while adjusting the sample volume to 5 mL. Add the internal 

standard/surrogate analyte PDS to the sample through the syringe valve. Immediately load 

the sample into the sparging vessel. 

NOTE: Do not store samples in syringes or prepare QC samples by filling two syringes. A 

second VOA vial (i.e., a FD) is required as a means of ensuring that a back up sample is 

available and for preparing FD, LFSM and LFSMD QC samples.

11.1.1 PREPARATION OF LFSM and LFSMD: SYRINGE METHOD – Three 40-mL 

vials (FDs) are required for a sample and its associated LFSM and LFSMD. Fortify 

two of the samples using an analyte PDS of appropriate concentration by injecting 

through the syringe valve. Add the internal standards and surrogates as directed in 

Section 11.1.

11.1.2 FIELD DUPLICATE: SYRINGE METHOD – Fill a 5-mL syringe with the selected 

FD and fortify with internal standards and surrogates. Analyze FDs at the frequency 

specified in Section 9.3.8.
524.4-28

11.2 SAMPLE PREPARATION: VIAL AUTOSAMPLER METHOD – Activate the cooling 

mechanism of the refrigerated autosampler and allow it to reach the temperature set point. 

Remove samples from cold storage and immediately load them into the vial autosampler. 

Prepare the IS/surrogate fortification solution at a concentration appropriate for the 

automated standard addition device.

11.2.1 PREPARATION OF LFSM and LFSMD FOR VIAL AUTOSAMPLERS – Three 

40-mL vials (FDs) are required for a sample and its associated LFSM and LFSMD. 

Fortify two of the samples using an analyte PDS of appropriate concentration by 

puncturing the septa of each vial with a syringe. Allow time for the compounds to 

disperse homogeneously within the sample. Assume that the sample volume is 40 

mL or estimate the typical volume of a 40-mL vial in use at your laboratory. 

Fortification may be accomplished by use of a standard addition module if the 

autosampler is so equipped.

11.2.2 FDs FOR VIAL AUTOSAMPLERS – Load the appropriate FD vial into the 

autosampler. Analyze FDs at the frequency specified in Section 9.3.8.

11.3 PURGE-AND-TRAP ANALYSIS

11.3.1 Establish purge-and-trap and GC/MS operating conditions per the guidance in 

Section 10.1.

11.3.2 Bake the concentrator trap and GC column to remove contaminants that may have 

collected in the system. This step is especially important if the analytical system has 

been idle for more than a few hours.

11.3.3 Initiate the purge cycle and autosampler sequence. After the purge cycle, preheat the 

trap as recommended by the manufacturer. Start the data acquisition at the 

beginning of the desorb cycle. Bake the trap and rinse the sparging vessel and 

autosampler delivery lines using settings optimized to minimize sample carryover. 

NOTE: The method preservatives cause the water column in the sparging vessel to 

appear effervescent during the purge cycle. This is normal and no adverse effects 

occur as a result of the effervescence.

11.4 THE ANALYSIS BATCH – Establish a valid initial calibration following the procedures 

outlined in Section 10.1 and confirm that the calibration is still valid by analyzing a CCC at 

or below the MRL as described in Section 10.2. Alternately, verify that an existing 

calibration, established for a previous Analysis Batch, is valid by analyzing a CCC at or 

below the MRL. Next, analyze a LRB. Continue the Analysis Batch by analyzing aliquots 

of field and QC samples at appropriate frequencies (Section 9.3), employing the optimized

conditions used to acquire the initial calibration. Analyze a mid- or high-level CCC after 

every ten field samples and at the end each Analysis Batch.

NOTE: Each Analysis Batch must begin with the analysis of a CCC at or below the MRL 

for each analyte that the laboratory intends to report, followed by the analysis of a LRB. 

This is true whether or not an initial calibration is analyzed. After 20 field samples, the low-
524.4-29

level CCC and the LRB must be repeated to begin a new Analysis Batch. The acquisition 

start time of the mid-level CCC at the end of the Analysis Batch must be within 24 hours of 

the acquisition start time of the low-level CCC at the beginning of the Analysis Batch. 

Multiple Analysis Batches within a 24-hour period are permitted. Do not count QC samples 

(LRBs, FRBs, FDs, LFSMs, LFSMDs) when calculating the frequency of CCCs that are 

required during an Analysis Batch.

12. DATA ANALYSIS AND CALCULATIONS

12.1 COMPOUND IDENTIFICATION – Establish 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 (Sect. 9.2) 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.

12.1.1 At the conclusion of data acquisition, use the same software settings established 

during the calibration procedure to identify peaks of interest in the predetermined 

retention time windows. Initially, identify an analyte by comparison of its retention 

time with that of the corresponding analyte peak in a recent initial calibration 

standard or CCC.

12.1.2 Some GC/MS programs use spectra matching criteria when collecting data in full 

scan mode based on the comparison of field sample spectra (after background 

subtraction if necessary) to a reference spectrum in the user-created database. This 

database should be created prior to conducting the IDC from spectra obtained for a 

mid-level to high-level calibration standard and updated as necessary. If available, 

this feature may be utilized as a secondary identification routine; however, the 

primary criterion must be based on the analyte retention time.

12.2 COMPOUND CONFIRMATION FULL SCAN MODE – In general, all ions that are present 

above 30 percent relative abundance in the mass spectrum of the user-generated database 

must be present in the mass spectrum of the sample component and must agree within an 

absolute 20 percent of the relative abundance in the reference spectrum. For example, if an 

ion has a relative abundance of 30 percent in the standard spectrum, its abundance in the 

sample spectrum must be in the range of 10 to 50 percent. Some ions, particularly the 

molecular ion, are of special importance and should be evaluated even if they are below 30 

percent relative abundance.

NOTE: Compound identification is more challenging when sample components are not 

resolved chromatographically and produce mass spectra containing ions contributed by more 

than one analyte. When GC peaks obviously represent more than one sample component 

(i.e., broadened peak with shoulder(s) or valley between two or more maxima), characteristic

analyte spectra may be obtained by examining the spectra of individual scans across the peak 

and then applying appropriate background subtraction. When analytes co-elute (i.e., only 

one GC peak is apparent), the identification criteria may be met but each analyte spectrum 

will contain extraneous ions contributed by the co-eluting compound.
524.4-30

12.3 COMPOUND CONFIRMATION SIM MODE – In SIM mode, each confirmation ion should

be present. For each analyte identified by retention time, 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 analyzed in SIM mode. 

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.

12.4 COMPOUND QUANTITATION – Calculate analyte concentrations using the multipoint 

calibration established in Section 10.1. Report only those values that fall between the MRL 

and the highest calibration standard.

12.4.1 Calculations must use all available digits of precision, but final reported 

concentrations should be rounded to an appropriate number of significant figures (one 

digit of uncertainty); this is typically two and not more than three, significant figures.

12.4.2 Prior to reporting data, the chromatograms must be reviewed for incorrect peak 

identification or improper integration.

12.4.3 Prior to reporting data, the laboratory is responsible for assuring that QC 

requirements have been met and that any appropriate qualifier is assigned.

12.5 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 FD using reagent water containing the method preservatives. 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.

13. METHOD PERFORMANCE

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

endorsement of the product. These references do not preclude the use of other vendors or supplies.

13.1 PRECISION, ACCURACY AND DETECTION LIMITS – The method performance data 

presented in Section 17 were collected using a Tekmar Stratum Purge-and-trap Concentrator 

with a Tekmar AQUATek 70 Vial Autosampler interfaced to an Agilent 6890 Plus GC and an 

Agilent 5973 MS. Table 2 lists the purge-and-trap conditions used to gather the method 

performance data presented in Section 17. GC/MS conditions for the Agilent system are 

presented in Table 3. Table 4 presents the quantitation ions employed in full scan mode 

appropriate for the Restek Rtx®-VMS column (no interference from overlapping peaks) for 

each analyte, internal standard and surrogate analyte, suggested internal standard assignments

and observed retention times associated with the method performance results. Table 5 lists 

the method analytes for which method performance data were collected in the SIM mode; 

primary quantitation ions, confirmation ions and internal standard references are provided. 

Single laboratory LCMRLs and DLs determined in full scan mode are listed in Table 6. 

Single laboratory precision and accuracy data obtained in full scan mode are presented for 

three water matrices: reagent water (Table 7), chlorinated (finished) ground water (Table 8)

and chlorinated (finished) surface water (Table 9). LCMRLs and DLs obtained in SIM mode 
524.4-31

for selected method analytes are presented in Table 10. Figure 1 depicts an extracted ion 

chromatogram of the method analytes that are gases at room temperature acquired in full scan 

mode. Figures 2 and 3 are total ion chromatograms of the method analytes in reagent water

and drinking water obtained under the conditions employed during method development in 

full scan mode. Figure 4 depicts an extracted ion chromatogram of the method analytes that 

are gases at room temperature acquired in SIM mode. Figure 5 is a total ion chromatogram of 

the method analytes in reagent water obtained under the conditions employed during method 

development in SIM mode.

13.2 SAMPLE STORAGE STABILITY STUDIES – An analyte storage stability study was 

conducted during the development of EPA Method 524.3 by fortifying the analytes (20 μg/L 

of each analyte) into a chlorinated surface water that was collected, preserved and stored as 

described in Section 8. The average recovery of triplicate analyses, conducted on Days 0, 7

and 14 are presented in Table 11. These results are reproduced in Method 524.4 to document 

that storage stability for the method analytes has been demonstrated.

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 website.

15. WASTE MANAGEMENT

The analytical procedures described in this method generate relatively small amounts of waste since 

only small amounts of reagents and solvents are used. The matrix of concern is finished drinking 

water. However, the Agency requires that laboratory waste management practices be conducted 

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. Winslow, S. D.; Pepich, B. V.; Martin, J. J.; Hallberg, G. R.; Munch D. J.; Frebis, C. P.; 

Hedrick, E. J.; Krop, R. A. Statistical Procedures for Determination and Verification of 

Minimum Reporting Levels for Drinking Water Methods. Environ. Sci. Technol. 2006; 40, 

281-288. 

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

Wastewaters. Environ. Sci. Technol. 1981; 15, 1426-1435.

3. Occupational Exposures to Hazardous Chemicals in Laboratories, 29 CFR 1910.1450,

Occupational Safety and Health Administration.

4. Safety in Academic Chemistry Laboratories; American Chemical Society Publication;

Committee on Chemical Safety: 7th Edition, 2003.
524.4-32

5. Standard Practice for Sampling Water from Closed Conduits; ASTM Annual Book of 

Standards, Section 11, Volume 11.01, D3370-07; American Society for Testing and Materials: 

Philadelphia, PA, 2007.
524.4-33

17. TABLES, DIAGRAMS, FLOWCHARTS and VALIDATION DATA

The conditions listed in the tables of this section were used to collect method performance data at EPA. 

They do not represent any form of guidance for acceptable parameter settings. Refer to the relevant 

sections of the method for guidance on optimizing and selecting purge-and-trap and GC/MS conditions.

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. PURGE-AND-TRAP CONDITIONS USED FOR METHOD PERFORMANCE 

RESULTS

Parameter Conditionsa

Sample volume 5 mL

Sample purge temperature 40 oC

Trap Supelco K-Trap (Vocarb® 3000)

Purge cycle 40 mL/min for 11 min

Condenser purge temperature 20 oC

Dry purge 100 mL/min for 3 min

Desorb preheat temperature 250 oC

Desorb cycle 260 oC for 1.0 min

Bake rinse cycles Sparging vessel and autosampler sample path rinsed twice

Bake cycle 260 oC for 6 min @ 200 mL/min a The chromatograms presented in Figures 2 and 3 were obtained under these conditions.
524.4-34

TABLE 3. GAS CHROMATOGRAPHY/MASS SPECTROMETRY (GC/MS) CONDITIONS

FOR METHOD PERFORMANCE RESULTS

Parameter Conditionsa

Column Restek Rtx®-VMS 30 meter, 0.25 mm i.d., 1.4 μm df

Inlet liner 1-mm i.d., deactivated glass

Inlet conditions 30:1 split ratio, 200 °C, helium carrier gas, column flow rate: 0.9 mL/min

GC temperature program 45 °C for 4.5 min, 12 oC/min to 100 °C, hold 0 min, 25 °C to 240 °C, 

hold 3.32 min

Solvent delay 1.5 min before activating filaments in the electron impact source

MS source temperature 230 oC

MS quadrupole temperature 150 °C

GC/MS interface Direct, 240 oC

Full scan window 1 m/z 47 to 150 (1.7 to 2.9 min)

Full scan window 2 m/z 35 to 260 (2.9 min to 18 min)

SIM parameters multiple retention time windows; dwell times set to allow seven to 10 

scans across chromatographic peaks

TABLE 4. RETENTION TIMES, RECOMMENDED QUANTITATION IONS and

SUGGESTED INTERNAL STANDARD REFERENCES FOR FULL SCAN MODEa

Analyte Peak no. Fig.’s 2a, 2b, 2c RT Q-Ion ISb Reference

dichlorodifluoromethane 1 1.84 85 1

chlorodifluoromethane 2 1.90 51 1

chloromethane 3 2.05 50 1

vinyl chloride 4 2.10 62 1

1,3-butadiene 5 2.11 54 1

bromomethane 6 2.40 94 1

trichlorofluoromethane 7 2.66 101 1

diethyl ether 8 2.98 59 1

1,1-dichloroethene 9 3.18 96 1

carbon disulfide 10 3.23 76 1

methyl iodide 11 3.36 142 1

allyl chloride 12 3.74 76 1

methylene chloride 13 3.87 84 1

trans-1,2-dichloroethene 14 4.08 96 1

methyl acetate 15 4.10 43 1

methyl-t-butyl ether-d3 (surrogate #1) 16 4.21 76 1

methyl-t-butyl ether (MtBE) 17 4.23 73 1

t-butyl alcohol (TBA) 18 4.38 59 1

diisopropyl ether (DIPE) 19 4.77 45 1

1,1-dichloroethane 20 4.94 63 1

t-butyl ethyl ether (ETBE) 21 5.29 59 1

cis-1,2-dichloroethene 22 5.68 96 1

bromochloromethane 23 5.95 128 1
524.4-35

Analyte Peak no. Fig.’s 2a, 2b, 2c RT Q-Ion ISb Reference

chloroform 24 6.05 83 1

carbon tetrachloride 25 6.22 117 1

tetrahydrofuran 26 6.26 72 1

1,1,1-trichloroethane 27 6.32 97 1

1,1-dichloropropene 28 6.48 110 1

1-chlorobutane 29 6.55 56 1

benzene 30 6.80 78 1

t-amyl methyl ether (TAME) 31 6.96 73 1

1,2-dichloroethane 32 7.06 62 1

trichloroethene 33 7.53 132 1

1,4-difluorobenzene (IS #1) 34 7.58 114 1

t-amyl ethyl ether (TAEE) 35 7.85 59 1

dibromomethane 36 8.05 93 1

1,2-dichloropropane 37 8.18 63 1

bromodichloromethane 38 8.26 83 1

cis-1,3-dichloropropene 39 9.06 75 1

toluene 40 9.32 92 2

tetrachloroethene 41 9.73 166 2

trans-1,3-dichloropropene 42 9.78 75 2

ethyl methacrylate 43 9.96 69 2

1,1,2-trichloroethane 44 9.94 83 2

dibromochloromethane 45 10.12 129 2

1,3-dichloropropane 46 10.21 76 2

1,2-dibromoethane 47 10.35 107 2

chlorobenzene-d5 (IS #2) 48 10.82 117 2

chlorobenzene 49 10.84 112 2

ethylbenzene 50 10.86 91 2

1,1,1,2-tetrachloroethane 51 10.90 131 2

m-xylene 52 10.99 106 2

p-xylene 53 10.99 106 2

o-xylene 54 11.36 106 2

styrene 55 11.41 104 2

bromoform 56 11.43 173 2

isopropylbenzene 57 11.62 105 2

4-bromofluorobenzene (surrogate #2) 58 11.85 95 3

bromobenzene 59 11.94 156 3

n-propylbenzene 60 11.96 91 3

1,1,2,2-tetrachloroethane 61 12.01 83 3

2-chlorotoluene 62 12.08 126 3

1,3,5-trimethylbenzene 63 12.11 105 3

1,2,3-trichloropropane 64 12.12 110 3

4-chlorotoluene 65 12.21 91 3

t-butylbenzene 66 12.35 134 3

pentachloroethane 67 12.38 167 3
524.4-36

Analyte Peak no. Fig.’s 2a, 2b, 2c RT Q-Ion ISb Reference

1,2,4-trimethylbenzene 68 12.40 105 3

sec-butylbenzene 69 12.49 105 3

4-isopropyltoluene 70 12.59 119 3

1,3-dichlorobenzene 71 12.66 146 3

1,4-dichlorobenzene-d4 (IS #3) 72 12.71 152 3

1,4-dichlorobenzene 73 12.72 146 3

n-butylbenzene 74 12.90 134 3

hexachloroethane 75 13.02 166 3

1,2-dichlorobenzene-d4 (surrogate #3) 76 13.03 152 3

1,2-dichlorobenzene 77 13.04 146 3

1,2-dibromo-3-chloropropane 78 13.61 157 3

hexachlorobutadiene 79 14.05 225 3

1,2,4-trichlorobenzene 80 14.08 180 3

naphthalene 81 14.31 128 3

1,2,3-trichlorobenzene 82 14.44 180 3 a These quantitation ions are appropriate for the column used to generate method performance data. The user must 

verify that the quantitation ions selected for their column are unique and free from interference due to overlapping 

method analytes.

b IS = internal standard.

TABLE 5. RETENTION TIMES, RECOMMENDED QUANTITATION IONS, 

CONFIRMATION IONS, SUGGESTED INTERNAL STANDARD REFERENCES, EXAMPLE 

CHROMATOGRAPHIC WINDOWS and DWELL TIMES FOR SIM MODEa

Analyte Peak no. Fig.’s 5a, 

5b, 5c

RT Q-Ion Confirmation

Ions

ISb

Reference Windowc

chlorodifluoromethane 1 1.87 51 67 1

1

chloromethane 2 2.03 50 52 1

vinyl chloride 3 2.09 62 64 1

1,3-butadiene 4 2.10 54 53 1

bromomethane 5 2.39 94 96 1

1,1-dichloroethene 6 3.18 96 61, 98 1

methylene chloride 7 3.87 84 49 1

trans-1,2-dichloroethene 8 4.07 96 61 1

2

methyl-t-butyl ether-d3 (surrogate #1) 9 4.20 76 57 1

methyl-t-butyl ether (MtBE) 10 4.22 73 57 1

1,1-dichloroethane 11 4.94 63 65 1

cis-1,2-dichloroethene 12 5.68 96 61 1

bromochloromethane 13 5.96 128 130 1

chloroform 14 6.05 83 85 1

carbon tetrachloride 15 6.22 117 119 1

1,1,1-trichloroethane 16 6.31 97 99 1

benzene 17 6.79 78 77 1

1,2-dichloroethane 18 7.06 62 64 1

3

trichloroethene 19 7.54 132 130, 95 1
524.4-37

Analyte Peak no. Fig.’s 5a, 

5b, 5c

RT Q-Ion Confirmation

Ions

ISb

Reference Windowc

1,4-difluorobenzene (IS #1) 20 7.59 114 63 1

1,2-dichloropropane 21 8.19 63 65 1

bromodichloromethane 22 8.26 83 85 1

toluene 23 9.32 92 91 2

tetrachloroethene 24 9.74 166 164 2

1,1,2-trichloroethane 25 9.95 83 97 2

dibromochloromethane 26 10.12 129 127 2

4

1,2-dibromoethane 27 10.35 107 109 2

chlorobenzene-d5 (IS #2) 28 10.83 117 - 2

chlorobenzene 29 10.84 112 114 2

ethylbenzene 30 10.86 91 106 2

1,1,1,2-tetrachloroethane 31 10.90 131 133 2

m-xylene 32 11.00 106 91 2

p-xylene 33 11.00 106 91 2

o-xylene 34 11.36 106 91 2

styrene 35 11.41 104 103, 78 2

bromoform 36 11.43 173 175 2

4-bromofluorobenzene (surrogate #2) 37 11.85 95 174 3

5

n-propylbenzene 38 11.96 91 120 3

1,2,3-trichloropropane 39 12.12 110 112, 75 3

sec-butylbenzene 40 12.49 105 134 3

1,4-dichlorobenzene-d4 (IS #3) 41 12.71 152 - 3

1,4-dichlorobenzene 42 12.73 146 148 3

1,2-dichlorobenzene-d4 (surrogate #3) 43 13.03 152 - 3

1,2-dichlorobenzene 44 13.04 146 148 3

1,2-dibromo-3-chloropropane 45 13.61 157 155, 75 3

1,2,4-trichlorobenzene 46 14.08 180 182 3 a These quantitation ions are appropriate for the column used to generate method performance data. The user must 

verify that the quantitation ions selected for their column are unique and free from interference due to overlapping 

method analytes.

b IS = internal standard. c Chromatographic window (also termed group number or period); dwell time for each ion is 10 milliseconds.

TABLE 6. LOWEST CONCENTRATION MINIMUM REPORTING LEVELS (LCMRLs) AND 

DETECTION LIMITS (DLs) FOR FULL SCAN MODEa

Analyte LCMRL, μg/L DL Fortification, μg/L DL, μg/L

dichlorodifluoromethane 0.33 0.25 0.12

chlorodifluoromethane 0.16 0.25 0.059

chloromethane 0.16 0.10 0.077

vinyl chloride 0.15 0.25 0.063

1,3-butadiene 0.33 0.10 0.055

bromomethane 0.28 0.25 0.099

trichlorofluoromethane 0.23 0.25 0.083
524.4-38

Analyte LCMRL, μg/L DL Fortification, μg/L DL, μg/L

diethyl ether 0.35 0.25 0.070

1,1-dichloroethene 0.18 0.25 0.14

carbon disulfide 0.20 0.10 0.078

methyl iodide 0.24 0.25 0.099

allyl chloride 0.26 0.25 0.12

methylene chloride 0.15 0.25 0.18

trans-1,2-dichloroethene 0.29 0.25 0.12

methyl acetate 0.21 0.25 0.12

methyl-t-butyl ether (MtBE) 0.17 0.10 0.042

t-butyl alcohol (TBA) 0.33 0.25 0.11

diisopropyl ether (DIPE) 0.10 0.10 0.029

1,1-dichloroethane 0.14 0.10 0.095

t-butyl ethyl ether (ETBE) 0.12 0.10 0.033

cis-1,2-dichloroethene 0.21 0.10 0.083

bromochloromethane 0.56 0.25 0.092

chloroform 0.16 0.10 0.070

carbon tetrachloride 0.14 0.10 0.073

tetrahydrofuran 0.49 0.10 0.063

1,1,1-trichloroethane 0.17 0.10 0.060

1,1-dichloropropene 0.50 0.25 0.14

1-chlorobutane 0.10 0.10 0.053

benzene 0.11 0.10 0.028

t-amyl methyl ether (TAME) 0.16 0.10 0.054

1,2-dichloroethane 0.23 0.10 0.027

trichloroethene 0.13 0.10 0.078

t-amyl ethyl ether (TAEE) 0.13 0.10 0.050

dibromomethane 0.18 0.25 0.13

1,2-dichloropropane 0.17 0.10 0.088

bromodichloromethane 0.19 0.25 0.081

cis-1,3-dichloropropene 0.13 0.10 0.050

toluene 0.13 0.10 0.031

tetrachloroethene 0.27 0.25 0.059

trans-1,3-dichloropropene 0.20 0.25 0.095

ethyl methacrylate 0.11 0.25 0.10

1,1,2-trichloroethane 0.38 0.10 0.048

dibromochloromethane 0.23 0.25 0.10

1,3-dichloropropane 0.12 0.10 0.098

1,2-dibromoethane 0.13 0.10 0.090

chlorobenzene 0.20 0.10 0.050

ethylbenzene 0.15 0.10 0.026

1,1,1,2-tetrachloroethane 0.18 0.10 0.081

m- and p-xylene 0.30 0.20 0.11

o-xylene 0.26 0.25 0.11

styrene 0.20 0.10 0.033

bromoform 0.26 0.25 0.14

isopropylbenzene 0.12 0.10 0.028

bromobenzene 0.19 0.10 0.066
524.4-39

Analyte LCMRL, μg/L DL Fortification, μg/L DL, μg/L

n-propylbenzene 0.18 0.10 0.045

1,1,2,2-tetrachloroethane 0.15 0.10 0.067

2-chlorotoluene 0.26 0.10 0.088

1,3,5-trimethylbenzene 0.12 0.10 0.037

1,2,3-trichloropropane 0.42 0.25 0.13

4-chlorotoluene 0.23 0.10 0.082

t-butylbenzene 0.25 0.25 0.16

pentachloroethane 0.29 0.25 0.16

1,2,4-trimethylbenzene 0.18 0.10 0.055

sec-butylbenzene 0.24 0.10 0.052

4-isopropyltoluene 0.16 0.10 0.064

1,3-dichlorobenzene 0.20 0.10 0.049

1,4-dichlorobenzene 0.19 0.10 0.029

n-butylbenzene 0.30 0.10 0.094

hexachloroethane 0.62 0.25 0.14

1,2-dichlorobenzene 0.14 0.10 0.056

1,2-dibromo-3-chloropropane 0.44 0.25 0.15

hexachlorobutadiene 0.34 0.10 0.086

1,2,4-trichlorobenzene 0.15 0.10 0.071

naphthalene 0.14 0.10 0.044

1,2,3-trichlorobenzene 0.16 0.10 0.042 a LCMRLs calculated according to the procedure in reference 1 with the following modification: Instead of 

evaluating seven replicates at four concentration levels, LCMRLs are now obtained by analyzing four replicates at 

seven concentration levels.
524.4-40

TABLE 7. PRECISION AND ACCURACY OF METHOD ANALYTES FORTIFIED AT 0.50, 

1.0 AND 10 μg/L IN REAGENT WATER FOR FULL SCAN MODE

Analyte

Fortified Conc. = 0.50 μg/L

(n=7)

Fortified Conc. = 1.0 μg/L

(n=7)

Fortified Conc. = 10 μg/L

(n=7)

Mean % Recovery RSDa Mean % Recovery RSD Mean % Recovery RSD

dichlorodifluoromethane 77.4 8.5 82.8 17 104 6.3

chlorodifluoromethane 127 4.1 122 4.7 110 7.1

chloromethane 88.8 14 102 3.3 108 5.5

vinyl chloride 103 8.7 106 6.0 109 6.5

1,3-butadiene 107 8.3 106 6.7 110 6.5

bromomethane 111 6.7 104 5.3 110 6.8

trichlorofluoromethane 105 9.0 104 8.2 111 6.9

diethyl ether 120 13 108 5.9 112 5.2

1,1-dichloroethene 108 7.9 93.2 5.3 103 6.0

carbon disulfide 93.6 6.4 92.3 6.0 98.9 6.6

methyl iodide 95.5 7.3 93.9 6.5 105 5.6

allyl chloride 76.1 5.6 84.2 6.1 100 8.0

methylene chloride 69.2 11 84.5 15 102 6.3

trans-1,2-dichloroethene 108 6.5 104 3.2 100 6.5

methyl acetate 88.9 11 89.6 12 103 4.3

methyl-t-butyl ether 

(MtBE) 97.5 8.9 97.6 3.5 103 5.2

t-butyl alcohol (TBA) 45.7 31 75.8 13 105 4.6

diisopropyl ether (DIPE) 90.5 3.5 96.2 2.5 103 5.2

1,1-dichloroethane 89.4 5.3 91.6 5.8 102 5.1

t-butyl ethyl ether (ETBE) 91.3 4.8 97.0 3.8 103 4.8

cis-1,2-dichloroethene 84.1 8.5 94.2 5.6 102 6.5

bromochloromethane 93.8 13 96.5 4.9 104 6.0

chloroform 90.1 4.5 97.3 4.3 103 5.5

carbon tetrachloride 83.0 9.7 92.4 3.9 100 5.2

tetrahydrofuran 86.6 21 93.5 8.9 100 5.1

1,1,1-trichloroethane 79.3 4.3 91.1 6.3 102 5.7

1,1-dichloropropene 99.7 6.6 95.6 6.7 97.6 8.1

1-chlorobutane 91.5 8.2 92.3 7.1 100 7.2

benzene 81.6 3.5 93.6 4.6 102 6.4

t-amyl methyl ether 

(TAME) 98.9 3.9 98.4 3.0 102 5.2

1,2-dichloroethane 105 4.0 102 4.5 104 4.3

trichloroethene 99.6 5.2 103 4.9 103 6.3

t-amyl ethyl ether (TAEE) 91.4 3.6 94.1 1.8 104 5.2

dibromomethane 89.0 12 93.8 6.1 104 5.4

1,2-dichloropropane 85.1 6.3 92.4 6.0 102 6.0

bromodichloromethane 87.3 8.5 97.1 3.7 104 4.7

cis-1,3-dichloropropene 83.9 3.9 92.7 3.5 102 5.9

toluene 85.6 3.4 92.0 6.5 102 4.4

tetrachloroethene 74.3 12 87.2 5.8 102 6.3

trans-1,3-dichloropropene 77.4 7.4 90.1 5.6 103 5.4

ethyl methacrylate 90.9 9.1 93.7 5.3 103 5.2

1,1,2-trichloroethane 97.6 7.0 101 8.5 104 3.7

dibromochloromethane 90.7 5.2 95.7 3.7 102 4.8

1,3-dichloropropane 93.0 2.7 96.4 4.0 105 3.9

1,2-dibromoethane 75.1 7.6 89.5 4.5 104 4.4

chlorobenzene 82.6 4.8 93.4 3.3 104 5.2

ethylbenzene 87.1 3.9 93.8 3.8 102 5.4
524.4-41

Analyte

Fortified Conc. = 0.50 μg/L

(n=7)

Fortified Conc. = 1.0 μg/L

(n=7)

Fortified Conc. = 10 μg/L

(n=7)

Mean % Recovery RSDa Mean % Recovery RSD Mean % Recovery RSD

1,1,1,2-tetrachloroethane 83.0 5.9 94.1 3.6 104 5.1

m- and p-xylene 82.6 7.0 93.3 2.9 102 4.5

o-xylene 77.3 5.6 94.3 2.7 103 5.6

styrene 88.2 8.1 95.3 3.3 102 5.3

bromoform 80.6 6.8 91.0 3.9 103 6.2

isopropylbenzene 83.1 2.8 93.6 3.0 103 5.3

bromobenzene 91.9 4.1 96.8 5.0 102 5.7

n-propylbenzene 89.7 4.1 96.3 2.1 100 6.1

1,1,2,2-tetrachloroethane 96.2 8.3 97.9 4.6 102 5.4

2-chlorotoluene 95.0 5.2 98.2 2.2 100 6.2

1,3,5-trimethylbenzene 87.4 4.4 94.9 1.8 102 5.8

1,2,3-trichloropropane 84.2 7.6 92.9 8.4 102 6.6

4-chlorotoluene 83.2 4.4 94.2 1.3 100 5.7

t-butylbenzene 86.9 8.7 92.4 6.9 102 6.0

pentachloroethane 87.6 12 89.9 5.8 100 5.8

1,2,4-trimethylbenzene 87.0 5.0 94.1 1.8 101 6.0

sec-butylbenzene 81.4 3.6 93.3 3.6 101 6.1

4-isopropyltoluene 84.5 5.9 95.5 2.4 102 6.6

1,3-dichlorobenzene 84.5 5.9 92.2 2.0 100 5.9

1,4-dichlorobenzene 86.6 4.2 97.2 3.3 102 5.7

n-butylbenzene 73.5 6.8 93.0 5.0 103 6.2

hexachloroethane 81.1 16 94.7 5.3 102 6.1

1,2-dichlorobenzene 83.0 6.2 96.6 3.4 103 5.6

1,2-dibromo-3-

chloropropane 80.5 10 90.9 7.1 103 5.7

hexachlorobutadiene 64.2 6.0 85.7 6.6 100 6.9

1,2,4-trichlorobenzene 90.7 5.3 91.9 2.1 100 5.2

naphthalene 88.0 2.9 94.0 3.2 102 5.7

1,2,3-trichlorobenzene 86.8 8.7 92.4 4.0 101 5.5 a RSD = relative standard deviation.
524.4-42

TABLE 8. PRECISION AND ACCURACY OF METHOD ANALYTES FORTIFIED AT 0.50, 

1.0 AND 10 μg/L IN DRINKING WATER FROM A GROUND WATER SOURCEa FOR FULL 

SCAN MODE

Analyte

Native 

Conc., μg/L 

(n=3)

Fortified Conc. = 0.50 

μg/L (n=7)

Fortified Conc. = 1.0 

μg/L (n=7)

Fortified Conc. = 10 

μg/L (n=7)

Mean % 

Recoveryb RSDc Mean % Recoveryb RSD Mean % Recoveryb RSD

dichlorodifluoromethane N.D. 112 2.8 95.0 5.6 104 4.1

chlorodifluoromethane N.D. 80.7 8.9 91.4 6.8 105 4.5

chloromethane N.D. 90.7 4.5 92.3 9.2 105 2.5

vinyl chloride N.D. 98.9 6.9 97.3 5.0 103 3.2

1,3-butadiene N.D. 66.1 16 84.3 5.9 101 4.0

bromomethane N.D. 115 7.3 115 8.4 127 10

trichlorofluoromethane N.D. 101 5.4 101 5.8 103 3.6

diethyl ether N.D. 101 5.6 103 9.0 103 1.4

1,1-dichloroethene N.D. 89.6 11 91.1 12 97.8 3.1

carbon disulfide N.D. 88.8 8.7 93.7 5.4 99.9 2.5

methyl iodide N.D. 81.0 18 81.6 11 105 8.5

allyl chloride N.D. 92.0 13 99.2 12 96.7 4.6

methylene chloride 0.39 73.7 10 97.8 11 100 3.4

trans-1,2-dichloroethene N.D. 82.2 19 91.2 8.2 102 3.4

methyl acetate N.D. 96.5 7.3 86.9 15 98.6 2.1

methyl-t-butyl ether 

(MtBE) N.D. 80.6 12 86.2 5.1 97.9 1.5

t-butyl alcohol (TBA) N.D. 92.3 9.7 97.9 9.4 91.3 2.0

diisopropyl ether (DIPE) N.D. 95.3 3.6 97.8 7.4 98.9 1.9

1,1-dichloroethane N.D. 86.0 10 93.9 5.7 99.8 2.9

t-butyl ethyl ether (ETBE) N.D. 81.4 5.7 91.2 3.3 98.1 2.2

cis-1,2-dichloroethene N.D. 87.3 9.4 94.8 4.3 97.1 2.5

bromochloromethane N.D. 101 9.5 104 7.0 97.2 3.3

chloroform 3.48 d 3.5 d 1.9 97.4 1.7

carbon tetrachloride N.D. 71.0 8.4 86.2 10 98.7 0.87

tetrahydrofuran N.D. 127 8.3 128.5 4.4 98.3 2.7

1,1,1-trichloroethane N.D. 90.2 8.5 98.7 5.5 99.9 2.8

1,1-dichloropropene N.D. 100 6.6 97.4 8.2 99.6 3.3

1-chlorobutane N.D. 94.7 9.1 98.9 4.7 101 3.2

benzene N.D. 84.5 7.3 93.0 4.7 98.6 2.6

t-amyl methyl ether 

(TAME) N.D. 97.3 4.2 92.3 8.7 94.5 2.4

1,2-dichloroethane N.D. 95.2 7.4 103 7.1 99.6 2.3

trichloroethene N.D. 83.6 6.8 91.9 6.3 98.3 2.7

t-amyl ethyl ether (TAEE) N.D. 89.0 8.8 96.4 5.4 96.3 1.7

dibromomethane N.D. 89.0 12 96.4 7.6 97.5 2.1

1,2-dichloropropane N.D. 85.5 7.2 93.9 6.8 96.4 1.6

bromodichloromethane 5.09 78.4d 1.5 75.5d 1.5 97.4 1.9

cis-1,3-dichloropropene N.D. 90.1 6.7 94.7 7.7 95.1 1.4

toluene N.D. 91.1 5.8 94.3 4.9 97.7 1.8

tetrachloroethene N.D. 93.5 12 95.3 11 97.3 2.9

trans-1,3-dichloropropene N.D. 82.4 6.4 92.0 11 95.8 3.2

ethyl methacrylate N.D. 94.0 8.8 91.9 8.3 94.4 1.7

1,1,2-trichloroethane N.D. 100 7.0 98.5 8.5 96.0 2.7

dibromochloromethane 6.08 d 1.8 d 3.5 97.6 1.4

1,3-dichloropropane N.D. 87.2 5.1 93.0 8.1 96.3 2.5

1,2-dibromoethane N.D. 99.0 8.0 98.8 9.1 95.8 3.1
524.4-43

Analyte

Native 

Conc., μg/L 

(n=3)

Fortified Conc. = 0.50 

μg/L (n=7)

Fortified Conc. = 1.0 

μg/L (n=7)

Fortified Conc. = 10 

μg/L (n=7)

Mean % 

Recoveryb RSDc Mean % Recoveryb RSD Mean % Recoveryb RSD

chlorobenzene N.D. 89.3 2.5 96.0 6.0 94.8 1.4

ethylbenzene N.D. 84.8 8.9 92.5 7.4 97.6 1.2

1,1,1,2-tetrachloroethane N.D. 90.9 7.2 94.9 7.9 94.5 1.6

m- and p-xylene N.D. 92.6 5.6 94.0 4.7 96.7 1.6

o-xylene N.D. 93.7 5.5 99.1 8.2 96.8 2.4

styrene N.D. 88.3 6.6 90.5 3.5 96.0 2.1

bromoform 2.17 d 4.5 d 4.5 92.1 2.6

isopropylbenzene N.D. 85.9 3.6 93.7 5.6 98.2 1.8

bromobenzene N.D. 78.2 11 94.0 6.4 92.7 2.5

n-propylbenzene N.D. 85.9 5.0 96.2 7.3 96.9 3.6

1,1,2,2-tetrachloroethane N.D. 96.4 6.8 99.2 7.2 92.6 1.8

2-chlorotoluene N.D. 83.3 4.8 93.8 8.1 93.2 2.9

1,3,5-trimethylbenzene N.D. 85.4 5.1 95.9 6.3 96.6 3.4

1,2,3-trichloropropane N.D. 92.5 10 96.8 10 93.3 2.9

4-chlorotoluene N.D. 84.5 6.1 93.1 8.6 93.6 2.5

t-butylbenzene N.D. 76.7 11 89.8 6.5 97.6 4.1

pentachloroethane N.D. 97.6 7.7 99.8 6.3 93.8 3.1

1,2,4-trimethylbenzene N.D. 90.9 4.9 98.0 5.5 95.8 3.1

sec-butylbenzene N.D. 85.9 1.8 97.6 4.7 97.3 3.3

4-isopropyltoluene N.D. 85.1 5.6 97.0 4.7 96.7 3.4

1,3-dichlorobenzene N.D. 88.6 4.5 98.0 7.0 93.6 2.0

1,4-dichlorobenzene N.D. 86.5 2.9 94.9 7.3 92.7 2.3

n-butylbenzene N.D. 87.0 3.6 95.8 5.9 95.2 3.1

hexachloroethane N.D. 99.5 15 103 10 97.6 4.4

1,2-dichlorobenzene N.D. 89.6 7.1 95.6 7.0 92.9 2.4

1,2-dibromo-3-

chloropropane N.D. 92.2 13 95.8 5.3 92.5 2.6

hexachlorobutadiene N.D. 80.8 6.1 91.7 6.8 94.8 3.6

1,2,4-trichlorobenzene N.D. 82.1 3.3 92.1 6.0 92.5 2.5

naphthalene N.D. 95.4 4.1 93.2 5.2 92.8 2.0

1,2,3-trichlorobenzene N.D. 101 5.0 95.6 6.8 91.4 2.6 a Ground water physical parameters: pH = 7.61; hardness = 350 milligrams/liter (mg/L) (as CaCO3); free chlorine = 

0.77 mg/L. b Recoveries corrected for native levels in the unfortified matrix. c RSD = relative standard deviation. d Fortified at less than 1⁄2 the concentration in the native matrix.
524.4-44

TABLE 9. PRECISION AND ACCURACY OF METHOD ANALYTES FORTIFIED AT 0.50, 

1.0 AND 10 μg/L IN DRINKING WATER FROM A SURFACE WATER SOURCEa FOR FULL 

SCAN MODE

Analyte

Native 

Conc., μg/L

(n=3)

Fortified Conc. = 0.50 

μg/L (n=7)

Fortified Conc. = 1.0 

μg/L (n=7)

Fortified Conc. = 10 

μg/L (n=7)

Mean % 

Recoveryb RSDc Mean % Recoveryb RSD Mean % Recoveryb RSD

dichlorodifluoromethane N.D. 90.5 10 90.7 3.7 103 2.8

chlorodifluoromethane N.D. 102 9.9 97.3 5.3 105 3.1

chloromethane N.D. 96.7 7.1 94.0 6.4 102 3.0

vinyl chloride N.D. 104 6.3 105 4.5 106 3.1

1,3-butadiene N.D. 109 5.5 97.9 8.7 104 3.0

bromomethane N.D. 108 8.5 104 9.1 116 5.3

trichlorofluoromethane N.D. 94.4 4.8 94.7 4.7 106 2.9

diethyl ether N.D. 104 8.3 104 4.7 104 3.7

1,1-dichloroethene N.D. 97.9 10 97.7 6.8 98.2 3.2

carbon disulfide N.D. 94.6 5.9 93.7 7.2 99.7 2.3

methyl iodide N.D. 85.1 7.5 86.3 6.0 95.2 3.2

allyl chloride N.D. 104 9.4 92.9 4.0 96.3 3.7

methylene chloride N.D. 104 9.1 102 6.1 102 2.2

trans-1,2-dichloroethene N.D. 100 11 89.8 12 97.7 3.0

methyl acetate N.D. 110 8.6 104 9.4 107 2.8

methyl-t-butyl ether 

(MtBE) N.D. 87.0 9.3 91.9 4.0 99.5 2.9

t-butyl alcohol (TBA) N.D. 91.8 7.6 99.7 4.6 107 3.0

diisopropyl ether (DIPE) N.D. 85.5 4.0 90.4 5.7 100 2.2

1,1-dichloroethane N.D. 95.1 5.1 92.4 4.3 98.9 3.2

t-butyl ethyl ether (ETBE) N.D. 84.2 4.1 87.6 3.6 99.4 2.0

cis-1,2-dichloroethene N.D. 97.3 5.5 96.6 7.5 101 2.5

bromochloromethane N.D. 90.8 16 98.3 8.3 103 2.1

chloroform 19.4 d 2.0 d 6.1 86.0 2.2

carbon tetrachloride N.D. 86.0 8.6 89.4 5.1 101 1.4

tetrahydrofuran N.D. 84.5 14 97.7 6.5 103 2.7

1,1,1-trichloroethane N.D. 84.9 7.5 89.3 7.2 97.7 2.9

1,1-dichloropropene N.D. 92.6 15 90.5 4.2 96.3 4.6

1-chlorobutane N.D. 92.3 8.7 91.0 7.9 99.3 2.2

benzene N.D. 94.6 7.8 96.2 4.6 99.4 2.1

t-amyl methyl ether 

(TAME) N.D. 80.8 9.8 88.8 8.7 100 2.6

1,2-dichloroethane N.D. 94.7 8.7 90.8 3.5 99.8 1.8

trichloroethene N.D. 89.4 10 90.5 7.1 99.2 1.9

t-amyl ethyl ether (TAEE) N.D. 59.5 7.1 83.1 3.4 104 2.3

dibromomethane N.D. 91.4 7.9 93.6 7.1 99.5 2.9

1,2-dichloropropane N.D. 86.3 7.3 90.9 7.6 99.3 2.1

bromodichloromethane 20.3 d 1.6 d 3.4 87.4 2.4

cis-1,3-dichloropropene N.D. 97.1 8.3 93.1 6.5 98.6 2.1

toluene N.D. 82.5 6.7 86.1 4.4 97.5 1.9

tetrachloroethene N.D. 80.3 7.1 83.5 5.9 93.6 1.5

trans-1,3-dichloropropene N.D. 91.3 7.1 92.3 5.1 97.2 3.9

ethyl methacrylate N.D. 84.4 5.1 89.5 4.5 98.3 2.5

1,1,2-trichloroethane N.D. 79.8 11 88.0 8.5 101 1.0

dibromochloromethane 16.1 d 1.3 d 3.0 99.6 2.7

1,3-dichloropropane N.D. 87.6 8.5 91.6 4.3 98.5 2.3

1,2-dibromoethane N.D. 80.8 4.9 83.9 5.6 97.7 3.0
524.4-45

Analyte

Native 

Conc., μg/L

(n=3)

Fortified Conc. = 0.50 

μg/L (n=7)

Fortified Conc. = 1.0 

μg/L (n=7)

Fortified Conc. = 10 

μg/L (n=7)

Mean % 

Recoveryb RSDc Mean % Recoveryb RSD Mean % Recoveryb RSD

chlorobenzene N.D. 73.9 6.6 86.0 3.1 97.2 2.1

ethylbenzene N.D. 79.8 4.9 84.7 4.6 96.3 2.2

1,1,1,2-tetrachloroethane N.D. 75.5 6.2 83.3 5.9 95.9 3.8

m- and p-xylene N.D. 80.1 4.2 86.8 3.3 98.3 2.0

o-xylene N.D. 75.6 7.2 81.0 4.3 97.0 1.3

styrene N.D. 82.3 7.0 89.2 3.2 96.5 2.7

bromoform 3.63 d 3.5 d 4.0 96.0 2.4

isopropylbenzene N.D. 73.6 6.0 82.4 5.7 97.7 2.1

bromobenzene N.D. 79.0 11 86.1 7.5 95.7 3.7

n-propylbenzene N.D. 64.9 6.9 82.2 3.6 97.0 3.1

1,1,2,2-tetrachloroethane N.D. 74.1 8.0 86.3 4.7 96.9 4.6

2-chlorotoluene N.D. 81.7 6.2 86.0 4.1 95.8 2.8

1,3,5-trimethylbenzene N.D. 74.3 8.4 85.5 4.1 97.8 3.2

1,2,3-trichloropropane N.D. 86.3 8.0 87.4 7.7 96.6 5.1

4-chlorotoluene N.D. 69.9 11 79.7 5.8 97.2 2.8

t-butylbenzene N.D. 69.4 13 84.8 9.1 97.4 4.1

pentachloroethane N.D. 72.0 10 84.3 8.2 96.4 3.7

1,2,4-trimethylbenzene N.D. 77.8 4.8 86.0 6.1 97.8 2.9

sec-butylbenzene N.D. 64.5 5.5 80.7 5.7 99.1 2.6

4-isopropyltoluene N.D. 64.0 3.8 79.6 6.9 98.4 2.8

1,3-dichlorobenzene N.D. 77.3 10 84.4 8.8 97.3 2.5

1,4-dichlorobenzene N.D. 70.5 4.2 86.2 5.5 97.4 2.4

n-butylbenzene N.D. 69.4 12 80.9 9.5 99.1 3.7

hexachloroethane N.D. 89.3 14 93.3 10 99.7 2.9

1,2-dichlorobenzene N.D. 71.3 5.5 82.4 5.5 97.3 4.1

1,2-dibromo-3-

chloropropane N.D. 73.2 11 87.8 8.6 95.9 4.0

hexachlorobutadiene N.D. 59.2 14 75.7 8.4 98.5 3.6

1,2,4-trichlorobenzene N.D. 70.9 8.2 83.2 3.0 97.0 3.6

naphthalene N.D. 68.3 4.5 83.1 6.0 101 4.5

1,2,3-trichlorobenzene N.D. 72.3 10 82.8 4.6 97.0 5.1 a Surface water physical parameters: pH = 7.20; hardness = 152 milligrams/liter (mg/L) (as CaCO3); free chlorine = 

1.85 mg/L. b Recoveries corrected for native levels in the unfortified matrix. c RSD = relative standard deviation.

d Fortified at less than 1⁄2 the concentration in the native matrix.
524.4-46

TABLE 10. LOWEST CONCENTRATION MINIMUM REPORTING LEVELS (LCMRLs) 

AND DETECTION LIMITS (DLs) FOR SIM MODEa

Analyte LCMRL, μg/L DL Fortification, μg/L DL, μg/L

chlorodifluoromethane 0.027 0.025 0.006

chloromethane Not determined: significant background levels from trap materials (See Section 4.3.4)

vinyl chloride 0.048 0.025 0.007

1,3-butadiene 0.028 0.025 0.008

bromomethane Not determined: significant background levels from trap materials (See Section 4.3.4)

1,1-dichloroethene 0.061 0.050 0.009

methylene chloride Not determined: significant background levels from ambient sources

trans-1,2-dichloroethene 0.028 0.025 0.014

methyl-t-butyl ether (MtBE) 0.012 0.025 0.009

1,1-dichloroethane 0.011 0.025 0.007

cis-1,2-dichloroethene 0.040 0.040 0.037

bromochloromethane 0.060 0.040 0.013

chloroform 0.032 0.025 0.015

carbon tetrachloride 0.033 0.025 0.008

1,1,1-trichloroethane 0.039 0.025 0.009

benzene 0.022 0.025 0.012

1,2-dichloroethane 0.029 0.025 0.012

trichloroethene 0.037 0.025 0.012

1,2-dichloropropane 0.043 0.040 0.011

bromodichloromethane 0.027 0.025 0.011

toluene 0.034 0.025 0.009

tetrachloroethene 0.025 0.025 0.011

1,1,2-trichloroethane 0.029 0.025 0.010

dibromochloromethane 0.016 0.025 0.006

1,2-dibromoethane 0.048 0.025 0.023

chlorobenzene 0.036 0.025 0.009

ethylbenzene 0.013 0.025 0.009

1,1,1,2-tetrachloroethane 0.059 0.025 0.011

m-xylene and p-xylene 0.17 0.025 0.020

o-xylene 0.037 0.025 0.016

styrene 0.018 0.025 0.012

bromoform 0.021 0.025 0.008

n-propylbenzene 0.022 0.025 0.010

1,2,3-trichloropropane 0.033 0.040 0.028

sec-butylbenzene 0.019 0.025 0.011

1,4-dichlorobenzene 0.026 0.025 0.012

1,2-dichlorobenzene 0.025 0.025 0.013

1,2-dibromo-3-chloropropane 0.069 0.040 0.033

1,2,4-trichlorobenzene 0.030 0.025 0.013 a LCMRLs calculated according to the procedure in reference 1 with the following modification: Instead of 

evaluating seven replicates at four concentration levels, LCMRLs are now obtained by analyzing four replicates at 

seven concentration levels.
524.4-47

TABLE 11. SAMPLE HOLDING TIME DATA FOR METHOD ANALYTES FORTIFIED AT 

20 μg/L IN A CHLORINATED SURFACE WATERa (n=3 SAMPLES)

Analyte

Day 0 Day 7 Day 14

Mean % 

Recovery RSDb Mean % Recovery RSD Mean % Recovery RSD

dichlorodifluoromethane 110 2.2 107 2.5 111 3.9

chlorodifluoromethane 112 2.0 109 0.63 107 0.87

chloromethane 114 0.88 110 1.1 112 2.0

vinyl chloride 117 0.99 113 1.6 116 0.87

1,3-butadiene 116 1.3 106 1.9 105 4.6

bromomethane 117 6.9 116 3.5 114 2.5

trichlorofluoromethane 114 0.54 116 2.9 117 2.4

diethyl ether 110 1.2 106 1.5 113 1.0

1,1-dichloroethene 106 0.94 107 0.62 111 2.3

carbon disulfide 108 0.58 106 1.9 107 3.0

methyl iodide 106 1.3 106 0.33 101 0.93

allyl chloride 108 0.57 100 0.73 101 1.0

methylene chloride 106 0.17 106 0.55 108 0.92

trans-1,2-dichloroethene 107 0.89 103 1.8 107 1.5

methyl acetate 105 3.4 101 0.32 83.2 4.0

methyl-t-butyl ether (MtBE) 104 0.92 101 0.049 105 0.79

t-butyl alcohol (TBA) 105 3.2 104 2.9 105 1.8

diisopropyl ether (DIPE) 107 0.71 109 0.72 109 0.65

1,1-dichloroethane 109 1.0 108 0.82 111 0.74

t-butyl ethyl ether (ETBE) 105 0.30 107 0.53 107 0.89

cis-1,2-dichloroethene 106 0.66 105 0.67 108 0.71

bromochloromethane 104 0.64 104 1.4 105 0.45

chloroform 102 0.56 100 0.91 107 0.97

carbon tetrachloride 108 1.4 109 1.2 116 2.2

tetrahydrofuran 102 1.4 98.4 1.5 101 1.7

1,1,1-trichloroethane 109 0.70 109 0.89 115 0.94

1,1-dichloropropene 110 0.24 107 1.5 108 1.5

1-chlorobutane 114 0.25 111 1.1 115 0.90

benzene 108 0.63 106 1.2 109 0.57

t-amyl methyl ether (TAME) 105 0.56 107 0.45 107 0.59

1,2-dichloroethane 108 2.1 105 0.59 108 1.2

trichloroethene 105 0.28 105 0.85 107 0.16

t-amyl ethyl ether (TAEE) 107 0.31 108 0.73 107 0.69

dibromomethane 106 1.5 105 0.42 107 0.33

1,2-dichloropropane 108 0.48 106 0.21 109 0.78

bromodichloromethane 105 0.85 104 1.2 109 1.2

cis-1,3-dichloropropene 106 0.33 98.5 1.0 96.7 1.2

toluene 109 1.3 108 0.46 110 1.2

tetrachloroethene 110 2.4 106 1.1 111 2.7

trans-1,3-dichloropropene 106 1.9 99.1 0.94 96.4 0.30

ethyl methacrylate 108 1.4 104 0.56 105 1.5

1,1,2-trichloroethane 105 1.8 103 0.93 106 2.1

dibromochloromethane 104 0.99 104 0.98 107 0.98

1,3-dichloropropane 108 1.0 104 0.10 106 1.2

1,2-dibromoethane 104 1.7 104 1.3 106 0.72

chlorobenzene 108 1.4 106 0.36 109 1.1

ethylbenzene 115 1.1 110 0.33 116 1.4

1,1,1,2-tetrachloroethane 106 1.6 106 0.35 110 0.92

m- and p-xylene 114 1.3 110 0.70 114 2.3
524.4-48

Analyte

Day 0 Day 7 Day 14

Mean % 

Recovery RSDb Mean % Recovery RSD Mean % Recovery RSD

o-xylene 113 0.83 109 0.87 115 0.79

styrene 111 1.3 106 0.62 108 1.7

bromoform 103 1.8 101 1.7 108 1.5

isopropylbenzene 118 1.2 114 0.81 123 1.5

bromobenzene 109 0.38 104 1.9 107 1.8

n-propylbenzene 122 1.3 111 2.0 119 2.1

1,1,2,2-tetrachloroethane 108 0.63 100 1.5 103 0.83

2-chlorotoluene 115 0.65 107 1.9 112 2.1

1,3,5-trimethylbenzene 121 1.2 111 1.4 120 1.7

1,2,3-trichloropropane 106 1.6 102 2.5 102 1.4

4-chlorotoluene 113 4.1 106 1.8 110 2.0

t-butylbenzene 123 0.84 115 1.3 129 0.38

pentachloroethane 109 2.2 103 3.0 112 0.47

1,2,4-trimethylbenzene 120 0.99 110 2.0 118 1.5

sec-butylbenzene 125 1.5 115 1.8 129 1.9

4-isopropyltoluene 123 1.3 112 2.4 123 2.6

1,3-dichlorobenzene 113 0.85 105 1.7 109 1.5

1,4-dichlorobenzene 113 1.1 104 2.0 107 1.7

n-butylbenzene 122 1.3 106 3.6 111 6.5

hexachloroethane 123 0.42 115 0.82 132 1.6

1,2-dichlorobenzene 111 0.82 104 1.7 108 1.0

1,2-dibromo-3-

chloropropane 105 1.9 99.1 1.9 103 2.4

hexachlorobutadiene 122 2.5 112 3.6 124 2.1

1,2,4-trichlorobenzene 114 1.3 102 2.3 105 3.0

naphthalene 112 0.77 103 1.0 107 2.1

1,2,3-trichlorobenzene 114 0.53 103 1.7 108 2.0 a Surface water physical parameters: pH = 7.43; hardness = 154 milligrams/liter (mg/L) (as CaCO3); free chlorine = 

2.7 mg/L; total chlorine = 3.7 mg/L.

b RSD = relative percent deviation.
524.4-49

TABLE 12. INITIAL DEMONSTRATION OF CAPABILITY (IDC) QUALITY CONTROL 

REQUIREMENTS

Method 

Reference Requirement Specification and Frequency Acceptance Criteria

Section 

9.2.1

Demonstration of 

low system 

background

Analyze a Laboratory Reagent Blank

(LRB) prior to any other IDC steps.

Demonstrate that all method analytes are

<1⁄2 of the Minimum Reporting Level 

(MRL) and that possible interferences from 

reagents and glassware do not prevent the 

identification and quantitation of method

analytes.

Section

9.2.1

Test for system 

carryover

Analyze a LRB after the high calibration 

standard during the IDC calibration.

Demonstrate that the method analytes are

<1⁄2 of the MRL.

Section 

9.2.2

Demonstration of 

precision

Analyze 7 replicate Laboratory Fortified 

Blanks (LFBs) fortified near the 

midrange concentration.

Percent relative standard deviation must be 

≤20%.

Section 

9.2.3

Demonstration of 

accuracy

Calculate average recovery for replicates 

used in Section 9.2.2.

Mean recovery within +20% 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 

(Sect. 9.2.4.2) 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 +30% of the true value.
524.4-50

TABLE 13. ONGOING QUALITY CONTROL REQUIREMENTS

Method 

Reference Requirement Specification and Frequency Acceptance Criteria

Section 

10.1 Initial calibration

Use the internal standard calibration 

technique to generate a linear or 

quadratic calibration curve. Use at 

least 7 standard concentrations. 

Validate the calibration curve as 

described in Section 10.1.10.

When each calibration standard is 

calculated as an unknown using the 

calibration curve, the lowest level 

standard must be within +50% of the 

true value. All other points must be 

within +30% of the true value.

Section 

9.3.1

Laboratory Reagent 

Blank (LRB)

Analyze one LRB with each Analysis

Batch.

Demonstrate that all method analytes 

are below 1⁄2 the Minimum Reporting 

Level (MRL) and that possible 

interference from reagents and 

glassware do not prevent identification 

and quantitation of method analytes.

Section 

10.2

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 10 field 

samples and after the last field sample 

in a batch.

The lowest level CCC must be within 

+50% of the true value. All other 

points must be within +30% of the 

true value.

Results for field samples that are not 

bracketed by acceptable CCCs are 

invalid.

Section

9.3.5 Internal standard (IS) Internal standards are added to all 

standards and samples.

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 

analysis.

70% to 130% recovery

Section 

9.3.7

Laboratory Fortified 

Sample Matrix 

(LFSM)

Analyze one LFSM per Analysis 

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. All 

other analytes must be within +30% of 

the true value.

Section 

9.3.8

Laboratory Fortified 

Sample Matrix Duplicate (LFSMD) or 

Field Duplicate (FD)

Analyze at least one LFSMD or FD

with each Analysis Batch.

For LFSMDs or FDs, relative percent 

differences must be ≤30% (≤50% if 

concentration ≤2 x the MRL.).

Section 

9.3.9

Field Reagent Blank 

(FRB)

Analyze FRB if method analytes are 

detected in field samples (except 

disinfection byproducts).

Qualify results of any analyte detected 

in both field samples and the FRB.

Section 

9.3.10

Quality Control 

Sample (QCS)

Analyze mid-level QCS at least

quarterly.

Results must be +30% of the true 

value.
524.4-51

Figure 1. Mass chromatograms of "gases" in full scan mode @ 10 μg/L.
524.4-52

Figure 2a. Reconstructed total ion chromatogram full scan mode: 10-μg/L procedural calibration standard. See Table 4 for peak 

number to peak name cross reference.
524.4-53

Figure 2b. Reconstructed total ion chromatogram full scan mode: 10-μg/L procedural calibration standard. See Table 4 for peak 

number to peak name cross reference.
524.4-54

Figure 2c. Reconstructed total ion chromatogram full scan mode: 10-μg/L procedural calibration standard. See Table 4 for peak 

number to peak name cross reference.
524.4-55

Figure 3. Reconstructed total ion chromatogram full scan mode: method analytes fortified into drinking water @ 10 μg/L.
524.4-56

Figure 4. Mass chromatograms of "gases" in SIM mode @ 1.0 μg/L.
524.4-57

Figure 5a. Reconstructed total ion chromatogram SIM mode: 1.0-μg/L procedural calibration standard. See Table 5 for peak 

number to peak name cross reference.
524.4-58

Figure 5b. Reconstructed total ion chromatogram SIM mode: 1.0-μg/L procedural calibration standard. See Table 5 for peak 

number to peak name cross reference.
524.4-59

Figure 5c. Reconstructed total ion chromatogram SIM mode: 1.0-μg/L procedural calibration standard. See Table 5 for peak 

number to peak name cross reference.