EPA Document #: EPA/600/R-09/149
METHOD 538. DETERMINATION OF SELECTED ORGANIC CONTAMINANTS
IN DRINKING WATER BY DIRECT AQUEOUS INJECTION-
LIQUID CHROMATOGRAPHY/TANDEM MASS SPECTROMETRY
(DAI-LC/MS/MS)
Version 1.0
November 2009
J.A. Shoemaker
NATIONAL EXPOSURE RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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METHOD 538
DETERMINATION OF SELECTED ORGANIC CONTAMINANTS IN DRINKING
WATER BY DIRECT AQUEOUS INJECTION-LIQUID
CHROMATOGRAPHY/ TANDEM MASS SPECTROMETRY (DAI-LC/MS/MS)
1. SCOPE AND APPLICATION
1.1 This is a direct aqueous injection-liquid chromatography/tandem mass spectrometry
(DAI-LC/MS/MS) method for the determination of selected nonvolatile chemical
contaminants in drinking water. Accuracy and precision data have been generated in
reagent water, and finished ground and surface waters for the compounds listed in the
table below.
Chemical Abstract Services
Analvte Registry Number (CASRN)
Acephate 30560-19-1
Aldicarb 116-06-3
Aldicarb sulfoxide 1646-87-3
Dicrotophos 141-66-2
Diisopropyl methylphosphonate (DIMP) 1445-75-6
Fenamiphos sulfone 31972-44-8
Fenamiphos sulfoxide 31972-43-7
Methamidophos 10265-92-6
Oxydemeton-methyl 301-12-2
Quinoline 91-22-5
Thiofanox 39196-18-4
1.2 The Minimum Reporting Level (MRL) is the lowest analyte concentration that meets
Data Quality Objectives (DQOs) that are developed based on the intended use of this
method. The single laboratory lowest concentration MRL (LCMRL) is the lowest true
concentration for which the future recovery is predicted to fall, with high confidence
(99%), between 50 and 150% recovery. Single laboratory LCMRLs for analytes in
this method range from 0.011-1.5 |ig/L, and are listed in Table 5. The procedure used
to determine the LCMRL is described elsewhere.1
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1.3 Laboratories using this method will not be required to determine the LCMRLs, but will
need to demonstrate that their laboratory MRL meets the requirements described in
Section 9.2.4.
1.4 Determining the Detection Limit (DL) for analytes in this method is optional (Sect.
9.2.6). Detection limit is defined as the statistically calculated minimum concentration
that can be measured with 99% confidence that the reported value is greater than zero.2
The DL is compound dependent and is dependent on sample preparation, sample
matrix, fortification concentration, and instrument performance.
1.5 This method is intended for use by analysts skilled in the operation of LC/MS/MS
instruments and the interpretation of the associated data.
1.6 METHOD FLEXIBILITY - In recognition of technological advances in analytical
systems and techniques, the laboratory is permitted to modify the separation technique,
LC column, mobile phase composition, LC conditions and MS and MS/MS conditions
(Sect. 6.6, 9.4, 10.2, and 12.1). Changes may not be made to sample collection and
preservation (Sect. 8), or to the quality control requirements (Sect. 9). Method
modifications should be considered only to improve method performance.
Modifications that are introduced in the interest of reducing cost or sample processing
time, but result in poorer method performance, should not be used. Analvtes must be
adequately resolved chromatographically in order to permit the mass spectrometer to
dwell on a minimum number of compounds eluting within a retention time window.
Instrumental sensitivity (or signal-to-noise) will decrease if too many compounds are
permitted to elute within a retention time window. In all cases where method
modifications are proposed, the analyst must perform the procedures outlined in the
initial demonstration of capability (IDC, Sect. 9.2), verify that all Quality Control
(QC) acceptance criteria in this method (Sect. 9) are met, and that acceptable method
performance can be verified in a real sample matrix (Sect. 9.3.5).
NOTE: The above method flexibility section is intended as an abbreviated summation
of method flexibility. Sections 4-12 provide detailed information of specific
portions of the method that may be modified. If there is any perceived
conflict between the general method flexibility statement in Section 1.6 and
specific information in Sections 4-12, Sections 4-12 supersede Section 1.6.
2. SUMMARY OF METHOD
2.1 A 40-mL water sample is collected in a bottle containing sodium omadine and
ammonium acetate. An aliquot of the sample is placed in an autosampler vial and the
internal standards are added. A 50-jiL or larger injection is made into an LC equipped
with a Cig column that is interfaced to an MS/MS operated in the electrospray
ionization (ESI) mode. The analytes are separated and identified by comparing the
acquired mass spectra and retention times to reference spectra and retention times for
calibration standards acquired under identical LC/MS/MS conditions. The
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concentration of each analyte is determined by internal standard calibration using
procedural standards.
3. DEFINITIONS
3.1 ANALYSIS BATCH - A set of samples analyzed on the same instrument, not
exceeding a 24-hour period and including no more than 20 Field Samples, beginning
and ending with the analysis of the appropriate Continuing Calibration Check (CCC)
standards. Additional CCCs may be required depending on the length of the analysis
batch and/or the number of Field Samples.
3.2 CALTERATION STANDARD (CAL) - A solution prepared from the primary dilution
standard solution and/or stock standard solution and the internal standard(s). The CAL
solutions are used to calibrate the instrument response with respect to analyte
concentration.
3.3 COLLISIONALLY ACTIVATED DISSOCIATION (CAD) - The process of
converting the precursor ion's translational energy into internal energy by collisions
with neutral gas molecules to bring about dissociation into product ions.
3.4 CONTINUING CALIBRATION CHECK (CCC) - A calibration standard containing
the method analytes and internal standard(s). The CCC is analyzed periodically to
verify the accuracy of the existing calibration for those analytes.
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 of precision (Sect. 9.2.6), and
accurate quantitation is not expected at this level.2
3.6 FIELD DUPLICATES (FD1 and FD2) - Two separate samples collected at the same
time and place under identical circumstances, and treated exactly the same throughout
field and laboratory procedures. Analyses of FD1 and FD2 give a measure of the
precision associated with sample collection, preservation, and storage, as well as
laboratory procedures.
3.7 INTERNAL STANDARD (IS) - A pure chemical added to a standard solution in a
known amount(s) and used to measure the relative response of other method analytes
that are components of the same solution. The internal standard must be a chemical
that is structurally similar to the method analytes, has no potential to be present in
water samples, and is not a method analyte.
3.8 LABORATORY FORTIFIED BLANK (LFB) - A volume of reagent water or other
blank matrix to which known quantities of the method analytes and all the preservation
reagents are added in the laboratory. The LFB is analyzed exactly like a sample, and
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its purpose is to determine whether the methodology is in control, and whether the
laboratory is capable of making accurate and precise measurements.
3.9 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) - A preserved field
sample to which known quantities of the method analytes are added in the laboratory.
The LFSM is processed and analyzed exactly like a sample, and its purpose is to
determine whether the sample matrix contributes bias to the analytical results. The
background concentrations of the analytes in the sample matrix must be determined in
a separate sample and the measured values in the LFSM corrected for background
concentrations.
3.10 LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE (LFSMD) - A
duplicate of the Field Sample used to prepare the LFSM. The LFSMD is fortified, and
analyzed identically to the LFSM. The LFSMD is used instead of the Field Duplicate
to assess method precision when the occurrence of method analytes is low.
3.11 LABORATORY REAGENT BLANK (LRB) - An aliquot of reagent water or other
blank matrix that is treated exactly as a sample including exposure to all glassware,
equipment, solvents and reagents, sample preservatives, and internal standards that are
used in the analysis batch. The LRB is used to determine if method analytes or other
interferences are present in the laboratory environment, the reagents, or the apparatus.
3.12 LOWEST CONCENTRATION MINIMUM REPORTING LEVEL (LCMRL) - The
single laboratory LCMRL is the lowest true concentration for which a future recovery
is expected, with 99% confidence, to be between 50 and 150% recovery.1
3.13 MATERIAL SAFETY DATA SHEET (MSDS) - Written information provided by
vendors concerning a chemical's toxicity, health hazards, physical properties, fire, and
reactivity data including storage, spill, and handling precautions.
3.14 MINIMUM REPORTING LEVEL (MRL) - The minimum concentration that can be
reported as a quantitated value for a method analyte in a sample following analysis.
This defined concentration can be no lower than the concentration of the lowest
calibration standard for that analyte and can only be used if acceptable QC criteria for
this standard are met. A procedure for verifying a laboratory's MRL is provided in
Section 9.2.4.
3.15 PRECURSOR ION - For the purpose of this method, the precursor ion is the
protonated molecule ([M+H]+) or adduct ion of the method analyte. In MS/MS, the
precursor ion is mass selected and fragmented by collisionally activated dissociation to
produce distinctive product ions of smaller m/z.
3.16 PRIMARY DILUTION STANDARD (PDS) SOLUTION - A solution containing the
analytes prepared in the laboratory from stock standard solutions and diluted as needed
to prepare calibration solutions and other needed analyte solutions.
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3.17 PRODUCT ION - For the purpose of this method, a product ion is one of the fragment
ions produced in MS/MS by collisionally activated dissociation of the precursor ion.
3.18 QUALITY CONTROL SAMPLE (QCS) - A solution of method analytes of known
concentrations that is obtained from a source external to the laboratory and different
from the source of calibration standards. The QCS is used to check calibration
standard integrity.
3.19 STOCK STANDARD SOLUTION (SSS) - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed reference materials or
purchased from a reputable commercial source.
4. INTERFERENCES
4.1 All glassware must be meticulously cleaned. Wash glassware with detergent and tap
water, rinse with tap water, followed by a reagent water rinse. Non-volumetric
glassware can be heated in a muffle furnace at 400 °C for 2 h or solvent rinsed.
Volumetric glassware should be solvent rinsed and not be heated in an oven above
120 °C. Store clean glassware inverted, covered with foil, or capped.
4.2 Method interferences may be caused by contaminants in solvents, reagents (including
reagent water), sample bottles and caps, and other laboratory supplies or hardware that
lead to discrete artifacts and/or elevated baselines in the chromatograms. All items
such as these must be routinely demonstrated to be free from interferences (less than
1/3 the MRL for each method analyte) under the conditions of the analysis by
analyzing LRBs as described in Section 9.3.1. Subtracting blank values from
sample results is not permitted.
4.3 Matrix interferences may be caused by contaminants in the sample. The extent of
matrix interferences will vary considerably from source to source, depending upon the
nature of the water. Humic and/or fulvic material present in the sample at high levels
can cause enhancement and/or suppression in the electrospray ionization source.3"4
Total organic carbon (TOC) is a good indicator of humic content of the sample. Under
the LC conditions used during method development, matrix effects due to total organic
carbon (TOC), up to 8.7 mg/L, were not observed.
4.4 Relatively large quantities of the preservatives (Sect. 8.1.2) are added to sample
bottles. The potential exists for trace-level organic contaminants in these reagents.
Interferences from these sources should be monitored by analysis of LRBs (Sect.
9.3.1), particularly when new lots of reagents are acquired.
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5. SAFETY
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. A reference
file of MSDSs should be made available to all personnel involved in the chemical analyses.
Additional references to laboratory safety are available.5"7
6. EQUIPMENT AND SUPPLIES (Brand names and/or catalog numbers are included for
illustration only, and do not imply endorsement of the product.)
6.1 SAMPLE CONTAINERS - Amber glass bottles (40 mL or larger) fitted with teflon-
lined screw caps (Fisher Cat. No.: 02-912-377 or equivalent).
6.2 STANDARD SOLUTION STORAGE CONTAINERS - Amber glass bottles (10 mL
or larger) (Kimble Cat. No.: 60815-1965 or equivalent) fitted with teflon-lined screw
caps (Kimble Cat No.: 73802-15425 or equivalent).
6.3 AUTOSAMPLER VIALS - Amber glass 2.0-mL autosampler vials (National
Scientific Cat. No.: C4000-2W or equivalent) with caps (National Scientific Cat. No.:
C4000-53 or equivalent).
6.4 MICRO SYRINGES - Suggested sizes include 5, 10, 25, 50, 100, 250, 500 and
1000-jiL syringes.
6.5 ANALYTICAL BALANCE - Capable of weighing to the nearest 0.0001 g.
6.6 LIQUID CHROMATOGRAPHY (LC)/TANDEM MASS SPECTROMETER
(MS/MS) WITH DATA SYSTEM
6.6.1 LC SYSTEM - Instrument capable of reproducibly injecting at least 50-|iL
aliquots, and performing binary linear gradients at a constant flow rate near the
flow rate used for development of this method (0.3 mL/min). The LC must be
capable of pumping the ammonium formate/methanol mobile phase without the
use of a degasser which pulls vacuum on the mobile phase bottle (other types of
degassers are acceptable). Degassers which pull vacuum on the mobile phase
bottle will volatilize the ammonium formate mobile phase causing the analyte
peaks to shift to earlier retention times over the course of the analysis batch. The
use of a column heater is optional.
6.6.2 TANDEM MASS SPECTROMETER - The MS/MS instrument (Waters
Micromass Quattro Premier or equivalent) must be capable of positive ion ESI
near the suggested LC flow rate of 0.3 mL/min. The system must be capable of
performing MS/MS to produce unique product ions (Sect. 3.17) for the method
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analytes within retention time segments. A minimum of 10 scans across the
chromatographic peak is required to ensure adequate precision.
6.6.3 DATA SYSTEM - An interfaced data system is required to acquire, store, reduce,
and output mass spectral data. The computer software should have the capability
of processing stored LC/MS/MS data by recognizing an LC peak within any given
retention time window. The software must allow integration of the ion abundance
of any specific ion within specified time or scan number limits. The software
must be able to construct linear regressions or quadratic calibration curves, and
calculate analyte concentrations.
6.6.4 ANALYTICAL COLUMN - A Waters Atlantis T3 Cig column (2.1x150 mm)
packed with 5 jim dp Cig solid phase particles (Cat. No.: 36003736 or equivalent)
was used. Any column that provides adequate resolution, peak shape, capacity,
accuracy, and precision (Sect. 9) may be used.
7. REAGENTS AND STANDARDS
7.1 GASES, REAGENTS, AND SOLVENTS - Reagent grade or better chemicals should
be used. Unless otherwise indicated, it is intended that all reagents shall conform to
the specifications of the Committee on Analytical Reagents of the American Chemical
Society, where such specifications are available. Other grades may be used, provided
it is first determined that the reagent is of sufficiently high purity to permit its use
without lessening the quality of the determination.
7.1.1 REAGENT WATER - Purified water which does not contain any measurable
quantities of any method analytes or interfering compounds greater than 1/3 the
MRL for each method analyte of interest.
7.1.2 METHANOL (CH3OH, CAS#: 67-56-1) - High purity, demonstrated to be free of
analytes and interferences (Fisher Optima LC/MS grade, Cat. No.: A-456 or
equivalent).
7.1.3 AMMONIUM FORMATE (NH4CHO2, CAS#: 540-69-2) - High purity,
demonstrated to be free of analytes and interferences (Sigma-Aldrich LC/MS
grade, Cat. No.: 55674 or equivalent).
7.1.4 AMMONIUM ACETATE (NH4C2H3O2, CAS#: 631-61-8) - High purity,
demonstrated to be free of analytes and interferences (Sigma-Aldrich ACS grade,
Cat. No.: 238074 or equivalent).
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7.1.5 SODIUM OMADINE® (Sodium 2-pyridinethio-l-oxide, CAS#: 3811-73-2)-
High purity demonstrated to be free of analytes and interferences (Sigma-Aldrich
Cat. No.: H3261 or equivalent; Omadine is a registered trademark of Arch
Chemicals, Inc.).
7.1.6 20 mM AMMONIUM FORMATE/REAGENT WATER MOBILE PHASE - To
prepare 1 L, add 1.26 g ammonium formate to 1 L of reagent water. This solution
is prone to volatility losses and should be replaced at least every 48 hours.
7.1.7 2 M AMMONIUM ACETATE/REAGENT WATER - To prepare 100 mL, add
15.4 g ammonium acetate to a 100-mL volumentric flask. Dilute to volume with
reagent water. This solution should be kept refrigerated at <6°C and replaced at
least every two weeks due to potential volatility losses.
7.1.8 32 g/L SODIUM OMADINE® IN REAGENT WATER - To prepare 25 mL, add
0.80 g of sodium omadine to a 25-mL volumetric flask. Dilute to volume with
reagent water. This solution should be kept refrigerated at <6°C.
7.1.9 NITROGEN - Aids in aerosol generation of the ESI liquid spray and is used as
the collision gas in some MS/MS instruments. The nitrogen used should meet or
exceed instrument manufacturer's specifications.
7.1.10 ARGON - Used as the collision gas in MS/MS instruments. Argon should meet
or exceed instrument manufacturer's specifications. Nitrogen gas may be used as
the collision gas provided sufficient sensitivity (product ion formation) is
achieved.
7.2 STANDARD SOLUTIONS - When a compound purity is assayed to be 96% or
greater, the weight can be used without correction to calculate the concentration of the
stock standard. Solution concentrations listed in this section were used to develop this
method and are included as an example. Alternate concentrations may be used as
necessary depending on instrument sensitivity and the calibration range used.
Standards for sample fortification generally should be prepared in the smallest volume
that can be accurately measured to minimize the addition of excess organic solvent to
aqueous samples Even though stability times for standard solutions are
suggested in the following sections, laboratories should use standard QC
practices to determine when their standards need to be replaced.
7.2.1 INTERNAL (IS) STOCK STANDARD SOLUTIONS - This method uses the
five IS compounds listed in the table below. The internal standards were obtained
from Cambridge Isotopes Laboratories, except for methamidophos-de which was
obtained from EQ Laboratories. The IS(s) may be purchased from alternate
sources. Although alternate IS standards may be used provided they are
isotopically labeled compounds with similar functional groups as the method
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analytes, the analyst must have documented reasons for using alternate IS(s).
Alternate IS(s) must meet the QC requirements in Section 9.3.4.
Internal Standards
Methamidophos-de
Acephate-de
Oxydemeton-methyl-de
Quinoline-d?
Diisopropyl methylphosphonate-di4 (DIMP-di4)
7.2.1.1 IS STOCK STANDARD SOLUTIONS (100-1000 |ig/mL) - These IS stock
standards can be obtained as individual certified stock standard solutions.
During the development of this method, commercially obtained 100 |ig/mL
or 1000 |ig/mL stock standard solutions in acetonitrile or methanol were
used. IS stock standard solutions were stable for at least six months when
stored at -15 °C or less.
7.2.1.2 INTERNAL STANDARD PRIMARY DILUTION (IS PDS) STANDARD
(0.4-12.5 ng/|iL) - Prepare, or purchase commercially, the IS PDS at a
suggested concentration of 0.40-12.5 ng/|iL in acetonitrile. If prepared from
the individual stock standard solutions (Sect. 7.2.1.1), the table below can be
used as a guideline for preparing the IS PDS. The IS PDS has been shown
to be stable for at least six months when stored in amber glass bottles
(Sect. 6.2) at -4 °C. Fortification of the final 1-mL samples with 10 jiL of
this 0.40-12.5 ng/|iL solution (Sect. 11.2.1) will yield a concentration of
4-125 |ig/L of each IS in the 1-mL samples. The total volume of
acetonitrile added to the 1-mL sample should not exceed 2% to avoid
peak broadening of the early eluting analytes. Acetonitrile volumes in
excess of 2% may be used provided the laboratory can document that these
volumes do not adversely affect the peak shape of any of the method
analytes under the laboratories' operating conditions.
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IS
Methami dophos-de
Acephate-de
Oxydemeton-methyl-de
Quinoline-d?
Diisopropyl methylphosphonate-di4
Cone, of IS
Stock
(ug/mL)
100
100
100
1000
1000
Vol. of IS
Stock
(uL)
40
40
40
125
4.0
Final Cone, of
ISPDS
(ng/uL)a
0.40
0.40
0.40
12.5
0.40
a Final concentrations based upon preparing the IS PDS in a 10-mL volumetric and
diluting to the mark with acetonitrile.
7.2.2 ANALYTE STANDARD SOLUTIONS - Standard solutions may be prepared
from certified, commercially available solutions or from neat compounds. If the
neat compounds used to prepare solutions are of 96% or greater purity, the weight
may be used without correction for purity to calculate the concentration of the
stock standard. Solution concentrations listed in this section were used to
develop this method and are included as example concentrations With the
exception of dicrotophos and quinoline, the method development work was done
with commercially obtained stock standard solutions, which are readily available
from most suppliers of environmental standards. Quinoline was obtained from
Aldrich and dicrotophos from Chem Service as neat materials. At the time of
method development, DIMP was only available from Cerilliant CIL, Inc. Prepare
the Analyte Stock and Primary Dilution Standards as described below. Analysts
are permitted to use other PDS and calibration standard concentrations and
volumes as necessary to achieve adequate sensitivity.
7.2.2.1 ANALYTE STOCK STANDARD SOLUTION (SSS) (1 mg/mL, except as
noted) - If preparing from neat material, accurately weigh approximately
10 mg of pure material to the nearest 0.1 mg into a tared, 10-mL volumetric
flask. Dilute to the mark with methanol for a final concentration of
1 mg/mL. Repeat for each method analyte. In the case of quinoline,
accurately weigh approximately 20 mg of pure material to the nearest
0.1 mg into a tared, 1-mL volumetric flask. Dilute to the mark with
methanol for a final concentration of 20 mg/mL. These stock standards
were stable for at least six months when stored at -15 °C or less.
Alternatively, individual stock standards of the analytes in methanol or
acetonitrile may be purchased commercially. For the development of this
method, commercially purchased stock standards of 1 mg/mL were used to
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make primary dilution standards for all analytes except quinoline and
dicrotophos.
7.2.2.2 METHANOLIC ANALYTE PRIMARY DILUTION STANDARD (MEOH
PDS) SOLUTION (40 -1600 ng/jiL) - The analyte MEOH PDS contains all
the method analytes of interest at various concentrations in methanol. The
ESI and MS/MS response varies by compound; therefore, a mix of
concentrations may be needed in the analyte MEOH PDS. During method
development, the analyte MEOH PDS was prepared such that approximately
the same instrument response was obtained for all the analytes. The analyte
MEOH PDS is prepared (table below) by dilution of the combined analyte
SSSs with methanol in a 1-mL volumetric flask and is used to prepare the
analyte WATER PDS (Sect. 7.2.2.3). The analyte MEOH PDS has been
shown to be stable for six months when stored at -15 °C. Longer storage
times are acceptable provided appropriate QC measures are documented
demonstrating the analyte MEOH PDS stability.
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DEVIP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Analyte SSS
Cone.
(mg/niL)
1.0
1.0
1.0
1.0
1.0
1.0
21.6
1.0
1.0
1.0
1.0
Analyte SSS
Volume
(uL)
40
40
80
40
40
80
80
40
40
40
160
Final Analyte
MEOH PDS Cone.
(ng/nL)a
40
40
80
40
40
80
1728
40
40
40
160
"Final concentration calculation based upon a 1-mL final volume.
7.2.2.3 AQUEOUS ANALYTE PRIMARY DILUTION STANDARD (WATER
PDS) SOLUTION (0.25 -10.7 ng/|iL) - The analyte WATER PDS contains
all the method analytes of interest at various concentrations in reagent water
containing 10% methanol. The analyte WATER PDS is prepared by placing
62 jiL of the analyte MEOH PDS in a 10-mL volumetric flask and diluting
with reagent water containing 10% methanol and is used to prepare the CAL
standards, and fortify the LFBs, the LFSMs, the LFSMDs and FDs with the
method analytes. The analyte WATER PDS has been shown to be stable for
at least one month when stored at 4 °C. Longer storage times are acceptable
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provided appropriate QC measures are documented demonstrating the
analyte WATER PDS stability.
7.2.3 CALIBRATION STANDARDS (CAL) - Prepare a procedural calibration curve
from dilutions of the analyte WATER PDS in preserved reagent water. At least
five to seven calibration concentrations are required to prepare the initial
calibration curve spanning a 50 to 100-fold concentration range (Sect. 10.2).
Prepare the calibration standards, adding appropriate amounts of the ammonium
acetate and sodium omadine concentrated stocks (Sect. 7.1.7 and 7.1.8) as shown
in the table below. The target analyte concentrations found in Tables 5-11 can be
used as a starting point for determining the calibration range. An example of the
dilutions used to prepare the CALs, that were utilized to collect data in Section
17, is shown below. The lowest concentration CAL must be at or below the MRL,
which will depend on system sensitivity. The CALs may also be used as CCCs. If
stored in containers (Sect. 6.2), the aqueous standards must be refrigerated in the
same manner as the samples. A constant amount of the IS PDS is added to each
prepared CAL. This is accomplished for each CAL by taking 990 jiL of the final
CAL containing the 20 mM ammonium acetate and 64 mg/L sodium omadine,
and placing it in a 2.0-mL autosampler vial and adding 10 jiL of the IS PDS (Sect.
7.2.1.2). During method development, the CAL standards were shown to be
stable for at least two weeks when stored at <6 °C. Longer storage times are
acceptable provided appropriate QC measures are documented demonstrating the
CAL stability.
CAL
Level
1
2
3
4
5
6
7
Analyte
WATER
PDS
Cone.
(ng/uL)a
0.25
0.25
0.25
0.25
0.25
0.25
0.25
Analyte
WATER
PDS
Volume
(HL)
2
5
10
20
40
100
200
2M
Ammonium
Acetate Stock
Volume
(HL)
100
100
100
100
100
100
100
32g/L
Sodium
Omadine
Stock Volume
(HL)
20
20
20
20
20
20
20
Final
CAL
Std.
Cone.
(Hg/L)b
0.050
0.12
0.25
0.50
0.99
2.5
5.0
Final
Quinoline
Cone.
(Hg/L)b
2.1
5.4
11
21
43
107
214
Final
Aldicarb
Cone.
(Hg/L)b
0.10
0.25
0.50
0.99
2.0
5.0
10
Final
Thiofanox
Cone.
(Hg/L)b
0.20
0.50
0.99
2.0
4.0
9.9
20
a Quinoline = 10.7 ng/uL, Aldicarb and Aldicarb sulfoxide= 0.50 ng/uL, Thiofanox =1.0 ng/uL
b Final concentrations based upon preparing the CALs in a 10-mL volumetric and diluting to the mark with reagent
water.
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8. SAMPLE COLLECTION, PRESERVATION, AND STORAGE
8.1 SAMPLE BOTTLE PREPARATION
8.1.1
8.1.2
Samples must be collected in amber glass bottles fitted with PTFE-lined screw
caps (Sect. 6.1).
Prior to shipment to the field, ammonium acetate and sodium omadine must be
added to each amber bottle. If using the suggested 40-mL bottles (Sect. 6.1) to
collect a 40-mL aliquot, add 400 uL of the ammonium acetate concentrated stock
(Sect. 7.1.7) and 80 uL of the concentrated sodium omadine stock (Sect. 7.1.8). If
other collection volumes are used, adjust the amount of preservation reagent so
that the final concentrations of ammonium acetate and sodium omadine in the
sample containers are 1.5 g/L and 64 mg/L, respectively. Cap the vials to avoid
evaporation of the preservation reagents.
Compound
Sodium omadine
Ammonium acetate
Amount
64 mg/L
1.5 g/L
Purpose
Antimicrobial
Binds free chlorine
8.2 SAMPLE COLLECTION
8.2.1 Open the tap and allow the system to flush until the water temperature has
stabilized (approximately 3 to 5 min). Collect a representative sample from the
flowing stream using a beaker of appropriate size. Use this bulk sample to
generate individual samples as needed. Transfer a volume of approximately
40 mL into each collection container. Alternatively, collect the sample directly in
the sample bottle containing the preservatives.
8.2.2 When filling sample bottles, take care not to flush out the sample preservation
reagents. Samples do not need to be collected headspace free.
8.2.3 After collecting the sample, cap the bottle and agitate by hand to mix the sample
with the preservation reagents. Keep the sample sealed from time of collection
until analysis.
8.3 SAMPLE SHIPMENT AND STORAGE - Samples must be chilled during shipment
and must not exceed 10 °C during the first 48 hours after collection. Sample
temperature must be confirmed to be at or below 10 °C when the samples are received
at the laboratory. Samples stored in the lab must be held at or below 6 °C until
analysis, but should not be frozen.
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NOTE: Samples that are significantly above 10°C, at the time of collection, may
need to be iced or refrigerated for a period of time, in order to chill them
prior to shipping. This will allow them to be shipped with sufficient ice to
meet the above requirements.
NOTE: Samples that arrive at the laboratory on the same day of sample collection
(exclusively due to the close proximity of the sampling site to the
laboratory), may not yet have stabilized to 10°C or less when they arrive at
the lab. These samples are acceptable ONLY if packed on ice or with frozen
gel packs immediately after sample collection and hence, delivered while
samples are in the process of reaching an equilibrium temperature less than
10°C. These samples must contain the preservatives as described in Section
8.1.2.
8.4 SAMPLE HOLDING TIMES - Results of the sample storage stability study
(Table 12) indicated that all compounds listed in this method have adequate stability
for 14 days when collected, preserved, shipped and stored as described in Sections 8.1,
8.2, and 8.3. Therefore, aqueous samples must be analyzed within 14 days of
collection.
9. QUALITY CONTROL
9.1 QC requirements include the Initial Demonstration of Capability (IDC) and ongoing
QC requirements that must be met when preparing and analyzing Field Samples. This
section describes the QC parameters, their required frequencies, and the performance
criteria that must be met in order to meet EPA quality objectives. The QC criteria
discussed in the following sections are summarized in Tables 13 and 14. These QC
requirements are considered the minimum acceptable QC criteria. Laboratories are
encouraged to institute additional QC practices to meet their specific needs.
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 first generate an acceptable Initial Calibration following the
procedure outlined in Section 10.2.
9.2.1 INITIAL DEMONSTRATION OF LOW SYSTEM BACKGROUND - Any time
a new lot of solvents, reagents, and autosampler vials are used, it must be
demonstrated that an LRB is reasonably free of contamination and that the criteria
in Section 9.3.1 are met.
9.2.2 INITIAL DEMONSTRATION OF PRECISION (IDP) - Prepare and analyze four
to seven replicate LFBs (same as a CCC - Section 9.3.3) fortified near the
midrange of the initial calibration curve according to the procedure described in
Section 11. The sample preservative, as described in Section 8.1.2, must be added
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to these samples. The relative standard deviation (RSD) of the concentrations of
the replicate analyses must be less than 20%.
9.2.3 INITIAL DEMONSTRATION OF ACCURACY (IDA) - Using the same set of
replicate data generated for Section 9.2.2, calculate mean recovery. The mean
recovery of the replicate values must be within ± 30% of the true value.
9.2.4 MINIMUM REPORTING LEVEL (MRL) CONFIRMATION - Establish a target
concentration for the MRL based on the intended use of the method. The MRL
may be established by a laboratory for their specific purpose or may be set by a
regulatory agency. Establish an Initial Calibration following the procedure
outlined in Section 10.2. The lowest CAL standard used to establish the Initial
Calibration (as well as the low-level CCC, Section 10.3) 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.
9.2.4.1 Fortify and analyze seven replicate LFBs at the proposed MRL
concentration. These LFBs must contain all method preservatives described
in Section 8.1.2. Calculate the mean measured concentration (Mean) and
standard deviation for the method analytes in these replicates. Determine
the Half Range for the prediction interval of results (HRpiR) for each analyte
using the equation below
HRPIR =3.963s
where
s = the standard deviation
3.963 = a constant value for seven replicates.1
9.2.4.2 Confirm that the upper and lower limits for the Prediction Interval of Result
(PIR = Mean ±_ HRpm) meet the upper and lower recovery limits as shown
below
The Upper PIR Limit must be <150% recovery.
Mean + HR™ x 100% < 150%
FortifiedConcentrati on
The Lower PIR Limit must be > 50% recovery.
Mean - HRPIR
FortifiedConcentrati on
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9.2.4.3 The MRL is validated if both the Upper and Lower PIR Limits meet the
criteria described above (Sect. 9.2.4.2). If these criteria are not met, the
MRL has been set too low and must be confirmed again at a higher
concentration.
9.2.5 CALIBRATION CONFIRMATION - Analyze a QCS as described in
Section 9.3.7 to confirm the accuracy of the standards/calibration curve.
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 determine ifDL determination is required based upon the
intended use of the data.
Replicate analyses for this procedure should be done over at least three days (i.e.,
both the sample preparation and the LC/MS/MS analyses should be done over at
least three days). Prepare at least seven replicate LFBs at a concentration
estimated to be near the DL (e.g., three LFBs individually fortified on day one,
two LFBs individually fortified on day two, and two LFBs individually fortified
on day three). This concentration may be estimated by selecting a concentration
at two to five times the noise level. The DLs in Table 5 were calculated from
LFBs fortified at various concentrations as indicated in the table. The
appropriate fortification concentrations will be dependent upon the sensitivity of
the LC/MS/MS system used. All preservation reagents listed in Section 8.1.2
must also be added to these samples. Analyze the seven replicates through all
steps of Section 11.
NOTE: If an MRL confirmation data set meets these requirements, a DL may be
calculated from the MRL confirmation data, and no additional analyses
are necessary.
Calculate the DL using the following equation
J-^s_/_j — J xS I / 11 r\ r\r\\
(n-l,l-a=0.99)
where
s = standard deviation of replicate analyses
t (n-i, i-a=o.99)= Student's t value for the 99% confidence
level with n-l degrees of freedom
n = number of replicates.
NOTE: Do not subtract blank values when performing DL calculations. The DL
lination <
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r\
is a statistical determination of precision only. If the DL replicates are
-------
fortified at a low enough concentration, it is likely that they will not meet
the precision and accuracy criteria for CCCs, and may result in a
calculated DL that is higher than the fortified concentration. Therefore,
no precision and accuracy criteria are specified.
9.3 ONGOING QC REQUIREMENTS - This section summarizes the ongoing QC
criteria that must be followed when processing and analyzing Field Samples.
9.3.1 LABORATORY REAGENT BLANK (LRB) - An LRB is required with each
analysis batch (Sect. 3.1) to confirm that potential background contaminants are
not interfering with the identification or quantitation of method analytes. If the
LRB produces a peak within the retention time window of any analyte that would
prevent the determination of that analyte, determine the source of contamination
and eliminate the interference before processing samples. Background
contamination must be reduced to an acceptable level before proceeding.
Background from method analytes or other contaminants that interfere with the
measurement of method analytes must be below 1/3 of the MRL. Blank
contamination is estimated by extrapolation, if the concentration is below the
lowest CAL standard. This extrapolation procedure is not allowed for sample
results as it may not meet data quality objectives. If the method analytes are
detected in the LRB at concentrations equal to or greater than 1/3 the MRL, then
all data for the problem analyte(s) must be considered invalid for all samples in
the analysis batch.
9.3.2 CONTINUING CALIBRATION CHECK (CCC) - CCC standards, containing
the preservatives, are analyzed at the beginning of each analysis batch, after every
10 Field Samples, and at the end of the analysis batch. See Section 10.3 for
concentration requirements and acceptance criteria.
9.3.3 LABORATORY FORTIFIED BLANK (LFB) - Since this method utilizes
procedural calibration standards, which are fortified reagent waters, there is no
difference between the LFB and the CCC. Consequently, the analysis of a
separate LFB is not required as part of the ongoing QC. However, the acronym
LFB is used for clarity in the IDC.
9.3.4 INTERNAL STANDARDS (IS) - The analyst must monitor the peak areas of the
IS(s) in all injections during each analysis day. The IS peak areas in any
chromatographic run must be within 50-150% of the average IS areas in the most
recent calibration curve. If the IS areas in a chromatographic run do not meet
these criteria, inject a second aliquot from the same autosampler vial.
9.3.4.1 If the reinjected aliquot produces an acceptable IS response, report results
for that aliquot.
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9.3.4.2 If the reinjected aliquot fails the IS criterion, the analyst should check the
calibration by reanalyzing the most recently acceptable CAL standard. If
the CAL standard fails the criteria of Section 10.3, recalibration is in order
per Section 10.2. If the CAL standard is acceptable, report results obtained
from the reinjected aliquot, but annotate as "suspect/IS recovery."
Alternatively, prepare another aliquot of the sample as specified in Section
1 1.2 or collect a new sample and re-analyze.
9.3.5 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) - Analysis of an
LFSM is required in each analysis batch and is used to determine that the sample
matrix does not adversely affect method accuracy. Assessment of method
precision is accomplished by analysis of a Field Duplicate (FD) (Sect. 9.3.6);
however, infrequent occurrence of method analytes would hinder this assessment.
If the occurrence of method analytes in the samples is infrequent, or if historical
trends are unavailable, a second LFSM, or LFSMD, must be prepared and
analyzed from a duplicate of the Field Sample. Analysis batches that contain
LFSMDs will not require the analysis of a FD. If a variety of different sample
matrices are analyzed regularly, for example, drinking water from groundwater
and surface water sources, method performance should be established for each.
Over time, LFSM data should be documented by the laboratory for all routine
sample sources.
9.3.5.1 Within each analysis batch (Sect. 3.1), a minimum of one Field Sample is
fortified as an LFSM for every 20 Field Samples analyzed. The LFSM is
prepared by spiking a sample with an appropriate amount of the Analyte
WATER PDS (Sect. 7.2.2.3). Select a spiking concentration that is greater
than or equal to the matrix background concentration, if known. Use
historical data and rotate through the low, mid and high concentrations when
selecting a fortifying concentration.
9.3.5.2 Calculate the percent recovery (%R) for each analyte using the equation
%R =
where
A = measured concentration in the fortified sample
B = measured concentration in the unfortified sample
C = fortification concentration.
9.3.5.3 Analyte recoveries may exhibit matrix bias. For samples fortified at or
above their native concentration, recoveries should range between 70-130%,
except for low-level fortification near or at the MRL (within a factor of
two-times the MRL concentration) where 50-150% recoveries are
acceptable.
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9.3.5.4 If the accuracy of any analyte falls outside the designated range in the
LFSM, and the laboratory performance for that analyte is shown to be in
control in the CCCs, and the CCCs for the batch were not freshly prepared
on the day of analysis, the Analyte WATER PDS used to fortify the matrix
sample must be checked for analyte losses. Check the accuracy of the
Analyte WATER PDS by using it to prepare a fresh CCC. The fresh CCC
must meet the criteria in Section 10.3. If the fresh CCC does not meet the
criteria in Section 10.3, a new Analyte WATER PDS must be prepared and
the LFMS analysis repeated.
9.3.5.5 If the accuracy of any analyte falls outside the designated range, and the
laboratory performance for that analyte is shown to be in control in the
CCCs, as well as in the Analyte WATER PDS, the recovery is judged to be
matrix biased. The result for that analyte in the unfortified sample is labeled
"suspect/matrix" to inform the data user that the results are suspect due to
matrix effects.
9.3.6 FIELD DUPLICATE OR LABORATORY FORTIFIED SAMPLE MATRIX
DUPLICATE (FD or LFSMD) - Within each analysis batch (not to exceed 20
Field Samples, Sect. 3. 1), a minimum of one FD or LFSMD must be analyzed.
Duplicates check the precision associated with sample collection, preservation,
storage, and laboratory procedures. If method analytes are not routinely observed
in Field Samples, an LFSMD should be analyzed rather than an FD.
9.3.6. 1 Calculate the relative percent difference (RPD) for duplicate measurements
(FD1 and FD2) using the equation
RPD-- xlOO
9.3.6.2 RPDs for FDs should be <30%. Greater variability may be observed when
FDs have analyte concentrations that are within a factor of two of the MRL.
At these concentrations, FDs should have RPDs that are <50%. If the RPD
of any analyte falls outside the designated range, and the laboratory
performance for that analyte is shown to be in control in the CCC, the
recovery is judged to be matrix biased. The result for that analyte in the
unfortified sample is labeled "suspect/matrix" to inform the data user that
the results are suspect due to matrix effects.
9.3.6.3 If an LFSMD is analyzed instead of a FD, calculate the RPD for duplicate
LFSMs (LFSM and LFSMD) using the equation
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\LFSM -LFSMD\
-
9.3.6.4 RPDs for duplicate LFSMs should be <30% for samples fortified at or
above their native concentration. Greater variability may be observed when
LFSMs are fortified at analyte concentrations that are within a factor of two
of the MRL. LFSMs fortified at these concentrations should have RPDs
that are <50%. If the RPD of any analyte falls outside the designated range,
and the laboratory performance for that analyte is shown to be in control in
the CCC, the recovery is judged to be matrix biased. The result for that
analyte in the unfortified sample is labeled "suspect/matrix" to inform the
data user that the results are suspect due to matrix effects.
9.3.7 QUALITY CONTROL SAMPLES (QCS) - As part of the IDC (Sect. 9.2), each
time a new Analyte MEOH PDS (Sect. 7.2.2.2) is prepared, and at least quarterly,
analyze a QCS sample from a source different from the source of the CAL
standards. If a second vendor is not available, then a different lot of the standard
should be used. The QCS should be prepared near the midpoint of the calibration
range and analyzed as a CCC. Acceptance criteria for the QCS are identical to the
CCCs; the calculated amount for each analyte must be ± 30% of the expected
value. If measured analyte concentrations are not of acceptable accuracy, check
the entire analytical procedure to locate and correct the problem.
9.4 METHOD MODIFICATION QC REQUIREMENTS - The analyst is permitted to
modify LC columns, LC conditions, internal standards, and MS and MS/MS
conditions. Each time such method modifications are made, the laboratory must
confirm that the modifications provide acceptable method performance as defined in
the Sections 9 .4. 1-9 .4.3. Modifications to LC conditions should still produce
conditions such that co-elution of the method analytes is minimized to reduce the
probability of ESI suppression/enhancement effects.
9.4. 1 Each time method modifications are made, the analyst must repeat the procedures
of the IDC (Sect. 9.2) and verify that all QC criteria can be met in ongoing QC
samples (Sect. 9.3).
9.4.2 The analyst is also required to evaluate and document method performance for the
proposed method modifications in real matrices that span the range of waters that
the laboratory analyzes. This additional step is required because modifications
that perform acceptably in the IDC, which is conducted in reagent water, can fail
ongoing method QC requirements in real matrices. This is particularly important
for methods subject to matrix effects. If, for example, the laboratory analyzes
finished waters from both surface and groundwater municipalities, this
requirement can be accomplished by assessing precision and accuracy (Sects.
9.2.2 and 9.2.3) in a surface water with moderate to high Total Organic Carbon
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(TOC) (e.g., 2 mg/L or greater) and a hard groundwater (e.g., 250 mg/L or greater
as calcium carbonate).
9.4.3 The results of Sections 9.4.1 and 9.4.2 must be appropriately documented by the
analyst and should be independently assessed by the laboratory's Quality
Assurance (QA) officer prior to analyzing Field Samples.
9.4.3.1 When implementing method modifications, it is the responsibility of the
laboratory to closely review the results of ongoing QC, and in particular,
the results associated with the LFSMs (Sect. 9.3.5), FDs or LFSMDs
(Sect. 9.3.6), CCCs (Sect. 9.3.2), and the IS area counts (Sect. 9.3.4). If
repeated failures are noted, the modification must be abandoned.
10. CALIBRATION AND STANDARDIZATION
10.1 Demonstration and documentation of acceptable initial calibration is required before
any samples are analyzed. After the initial calibration is successful, a CCC is required
at the beginning and end of each period in which analyses are performed, and after
every tenth Field Sample.
10.2 INITIAL CALIBRATION
10.2.1 ESI-MS/MS TUNE
10.2.1.1 Calibrate the mass scale of the MS with the calibration compounds and
procedures prescribed by the manufacturer.
10.2.1.2 Optimize the [M+H]+ for each method analyte by infusing approximately
1.0-5.0 |ig/mL of each analyte (prepared in water containing 10% methanol)
directly into the MS at the chosen LC mobile phase flow rate
(approximately 0.3 mL/min). This tune can be done on a mix of the method
analytes. The MS parameters (voltages, temperatures, gas flows, etc.) are
varied until optimal analyte responses are determined. The method analytes
may have different optima requiring some compromise between the optima.
See Table 2 for ESI-MS conditions used in method development.
10.2.1.3 Optimize the product ion (Sect. 3.17) for each analyte by infusing
approximately 1.0-5.0 |ig/mL of each analyte (prepared in the initial mobile
phase conditions) directly into the MS at the chosen LC mobile phase flow
rate (approximately 0.3 mL/min). This tune can be done on a mix of the
method analytes. The MS/MS parameters (collision gas pressure, collision
energy, etc.) are varied until optimal analyte responses are determined. See
Table 4 for MS/MS conditions used in method development.
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10.2.2 Establish LC operating parameters that optimize resolution and peak shape.
Suggested LC conditions can be found in Table 1. The LC conditions listed in
Table 1 may not be optimum for all LC systems and may need to be optimized by
the analyst. 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 product ion in any co-eluting (or overlapping) peak(s).
NOTE: During method development, the LC flow was diverted to waste for the
first three minutes of the analysis. The flow was diverted to prevent
potential fouling of the ESI source from sample components including
preservatives. Laboratories are not required to divert the LC flow, but
more frequent maintenance may be necessary if the flow is not diverted
prior to elution of the first analyte.
10.2.3 Inject a mid-level CAL standard under LC/MS conditions to obtain the retention
times of each method analyte. Divide the chromatogram into retention time
windows so that each window contains one or more chromatographic peaks.
During MS/MS analysis, fragment a small number of selected precursor ions
([M+H]+; Sect. 3.15) for the analytes in each window and choose the most
abundant product ion. The product ions (also the quantitation ions) chosen during
method development are in Table 4, although these will be instrument dependent.
For maximum sensitivity during method development, small mass windows of
±0.5 daltons around the product ion mass were used for quantitation.
10.2.4 Inject a mid-level CAL standard under optimized LC/MS/MS conditions to ensure
that each method analyte is observed in its MS/MS window and that there are at
least 10 scans across the peak for optimum precision.
CAUTION: When acquiring MS/MS data, LC operating conditions must be
carefully reproduced for each analysis to provide reproducible
retention times. If this is not done, the correct ions will not be
monitored at the appropriate times. As a precautionary measure,
the chromatographic peaks in each window must not elute too close
to the edge of the segment time window.
10.2.5 Prepare a set of at least five CAL standards as described in Section 7.2.3. The
lowest concentration CAL standard must be at or below the MRL, which will
depend on system sensitivity. It is recommended that at least four of the CAL
standards are at a concentration greater than or equal to the MRL.
10.2.6 The LC/MS/MS system is calibrated using the IS technique. Use the LC/MS/MS
data system software to generate a linear regression or quadratic calibration curve
for each of the analytes. The curves may be concentration weighted, if necessary.
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10.2.7 CALIBRATION ACCEPTANCE CRITERIA - When quantitated using the initial
calibration curve, each calibration point, except the lowest point, for each analyte
should calculate to be within 70-130% of its true value. The lowest CAL point
should calculate to be within 50-150% of its true value. If these criteria cannot be
met, the analyst will have difficulty meeting ongoing QC criteria. It is
recommended that corrective action is taken to reanalyze the CAL standards,
restrict the range of calibration, or select an alternate method of calibration.
10.3 CONTINUING CALIBRATION CHECK (CCC) - Minimum daily calibration
verification is as follows. Verify the initial calibration at the beginning and end of
each group of analyses, and after every tenth sample during analyses. In this context,
a "sample" is considered to be a Field Sample. LRBs, CCCs, LFSMs, FDs and
LFSMDs are not counted as samples. The beginning CCC of each analysis batch must
be at or below the MRL in order to verify instrument sensitivity prior to any analyses.
If standards have been prepared such that all low CAL points are not in the same CAL
solution, it may be necessary to analyze two CAL standards to meet this requirement.
Alternatively, the analyte concentrations in the analyte PDS may be customized to
meet this criteria. Subsequent CCCs should alternate between a medium and high
concentration CAL standard.
10.3.1 Inject an aliquot of the appropriate concentration CAL standard and analyze with
the same conditions used during the initial calibration.
10.3.2 Determine that the absolute areas of the quantitation ions of the IS(s) are within
50-150% of the average areas measured in the most recent calibration. If any of
the IS areas has changed by more than these amounts, adjustments must be made
to restore system sensitivity. These adjustments may include cleaning of the MS
ion source, or other maintenance as indicated in Section 10.3.4. Major
instrument maintenance requires recalibration (Sect 10.2) and verification of
sensitivity by analyzing a CCC at or below the MRL (Sect 10.3). Control charts
are useful aids in documenting system sensitivity changes.
10.3.3 Calculate the concentration of each analyte in the CCC. The calculated amount
for each analyte for medium and high level CCCs must be within ± 30% of the
true value. The calculated amount for the lowest calibration point for each
analyte must be within ± 50% of the true value. If these conditions cannot be met,
then all data for the problem analyte must be considered invalid, and remedial
action should be taken (Sect. 10.3.4). This may require recalibration. Any Field
or QC Samples that have been analyzed since the last acceptable calibration
verification should be reanalyzed after adequate calibration has been restored,
with the following exception. If the CCC at the end of the batch fails because
the calculated concentration is greater than 130% (150% for the low-level
CCC) for a particular method analyte, and Field Samples show no detection
for that method analyte, non-detects may be reported without re-analysis.
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10.3.4 REMEDIAL ACTION - Failure to meet CCC QC performance criteria may
require remedial action. Major maintenance, such as cleaning the electrospray
probe, atmospheric pressure ionization source, cleaning the mass analyzer,
replacing the LC column, etc., requires recalibration (Sect 10.2) and verification
of sensitivity by analyzing a CCC at or below the MRL (Sect 10.3).
11. PROCEDURE
11.1. SAMPLE PREPARATION
11.1.1. Samples are preserved, collected and stored as presented in Section 8. All Field
and QC Samples must contain the preservatives listed in Section 8.1.2, including
theLRB.
11.1.2. In addition to the preservatives, if the sample is an LFSM or LFSMD, add the
necessary amount of analyte WATER PDS (Sect. 7.2.2.3). Cap and invert each
sample to mix.
NOTE: If the laboratory is concerned that a particular matrix may contain high
particulate levels that could cause clogging of the LC system, sample
filtration may be incorporated into the procedure. If filtering is
incorporated as part of the sample preparation, the first lot of filters must
be subjected to the procedures outlined in the IDC (Sect. 9.2) and meet
the acceptance criteria defined in Section 9.2 to ensure that they do not
introduce interferences or retain any of the method analytes. Verification
of subsequent lots of filters can be accomplished by examining a filtered
LRB and duplicate samples of filtered LFBs fortified at the MRL. The
filtered LFBs should calculate to be within ±50% of the true value. If the
LRB or the LFBs fail this evaluation, the full IDC will need to be
repeated with the new lot of filters. CAL standards and CCCs should not
be filtered in order to identify potential losses associated with the sample
filtration devices. During method development, Pall Gelman GUP
Acrodisc, 25 mm syringe filters with 0.45 jim GUP membranes (Cat.
No.: 4560T) were evaluated and found to pass all QC criteria. Other
filter materials may be used provided the QC criteria in Section 9 are
met.
11.2. SAMPLE ANALYSIS
11.2.1. Transfer a 990 jiL aliquot of the sample to an autosampler vial. Add 10 jiL of the
IS PDS (Sect. 7.2.1.2) to the autosampler vial. Cap and invert each vial to mix.
11.2.2. Establish operating conditions equivalent to those summarized in Tables 1-4 of
Section 17. Instrument conditions and columns should be optimized prior to the
initiation of the IDC.
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11.2.3. Establish an appropriate retention time window for each analyte. This should be
based on measurements of actual retention time variation for each method analyte
in CAL standard solutions analyzed on the LC over the course of time. A value
of plus or minus three times the standard deviation of the retention time, obtained
for each method analyte while establishing the initial calibration and completing
the IDC, can be used to calculate a suggested window size. However, the
experience of the analyst should weigh heavily on the determination of the
appropriate retention window size.
11.2.4. Calibrate the system by either the analysis of a set of CAL standards (Sect. 10.2)
or by confirming the existing calibration is still valid by analyzing a CCC as
described in Section 10.3. If establishing an initial calibration, complete the IDC
as described in Section 9.2.
11.2.5. Begin analyzing Field Samples, including QC samples, at their appropriate
frequency by injecting the same size aliquots (50 jiL was used in method
development) under the same conditions used to analyze the CAL standards.
11.2.6. At the conclusion of data acquisition, use the same software that was used in the
calibration procedure to identify peaks of interest in predetermined retention time
windows. Use the data system software to examine the ion abundances of the
peaks in the chromatogram. Identify an analyte by comparison of its retention
time with that of the corresponding method analyte peak in a reference standard.
Comparison of the MS/MS mass spectra is not particularly useful given the
limited ±0.5 dalton mass range around a single product ion for each method
analyte.
11.2.7. The analyst must not extrapolate beyond the established calibration range. If an
analyte peak area exceeds the range of the calibration curve, the new aliquot of
sample may be diluted with reagent water and the appropriate amount of IS
added. Re-inject the diluted sample. Incorporate the dilution factor into the final
concentration calculations. The resulting data should be documented as a
dilution, with an increased MRL.
12. DATA ANALYSIS AND CALCULATION
12.1. In validating this method, concentrations were calculated by measuring the product
ions listed in Table 4. Other product ions may be selected at the discretion of the
analyst.
12.2. Calculate analyte concentrations using the multipoint calibration established in
Section 10.2. Do not use daily calibration verification data to quantitate analytes in
samples.
538-26
-------
12.3 Prior to reporting the data, the chromatogram should be reviewed for any incorrect
peak identification or poor integration.
12.4 Calculations must utilize all available digits of precision, but final reported
concentrations should be rounded to an appropriate number of significant figures (one
digit of uncertainty), typically two, and not more than three significant figures.
13. METHOD PERFORMANCE
13.1 PRECISION, ACCURACY, AND MINIMUM REPORTING LEVELS - Tables for
these data are presented in Section 17. LCMRLs and DLs for each method analyte are
presented in Table 5. Precision and accuracy are presented for four tap water matrices:
reagent water (Tables 6 and 7); chlorinated surface water (Tables 8 and 9); chlorinated
(finished) ground water (Table 10); chlorinated surface water fortified with natural
organic matter (Table 11).
13.2 SAMPLE STORAGE STABILITY STUDIES - An analyte storage stability study was
conducted by fortifying the analytes into chlorinated surface water samples that were
collected, preserved, and stored as described in Section 8. The chlorinated surface
water was adjusted to pH=9.0 before adding the preservatives and analytes to simulate
the worst case scenario for compounds with potential to degrade under basic pH
conditions. The precision and mean recovery of analyses (n=7), conducted on Days 0,
7, and 14, are presented in Table 12.
13.3 MULTIPLE LABORATORY VERIFICATION - The performance of this method
was demonstrated by multiple laboratories, with accuracy and precision results similar
to those reported in Section 17. The authors wish to acknowledge the assistance of the
analysts and laboratories listed below for their participation in the multi-lab
demonstration.
13.3.1 Dr. Andrew Eaton and Mr. Ali Haghani of MWH Laboratories, Monrovia, CA.
13.3.2 Dr. Yongtao Li of Underwriters Laboratories, Inc., South Bend, IN.
13.3.3 Ms. Tiffany Payne and Mr. Ed George of Varian, Inc., Walnut Creek, CA.
14. POLLUTION PREVENTION
14.1 This method utilizes DAI-LC/MS/MS for the analysis of method analytes in water. It
requires the use of very small volumes of organic solvent and very small quantities of
pure analytes, thereby minimizing the potential hazards to both the analyst and the
environment.
14.2 For information about pollution prevention that may be applicable to laboratory
operations, consult "Less is Better: Laboratory Chemical Management for Waste
538-27
-------
Reduction" available from the American Chemical Society's Department of
Government Relations and Science Policy, 1155 16* Street N.W., Washington, D.C.,
20036 or on-line at http://membership.acs.Org/c/ccs/pub 9.htm (accessed November
2009).
15. WASTE MANAGEMENT
15.1 The analytical procedures described in this method generate relatively small amounts of
waste since only small amounts of reagents and solvents are used. The matrices of
concern are finished drinking water or source water. However, laboratory waste
management practices must 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. Also, compliance is
required with any sewage discharge permits and regulations, particularly the hazardous
waste identification rules and land disposal restrictions.
15.2 Local regulations may prohibit sink disposal of water containing sodium omadine.
Therefore, the laboratory should determine with local officials how to safely dispose of
Field and QC samples containing sodium omadine.
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. 2004,
40,281-288.
2. Glaser, J.A., D.L. Foerst, G.D. McKee, S.A. Quave, W.L. Budde, "Trace Analyses for
Wastewaters." Environ. Sci. Technol. 1981, 15, 1426-1435.
3. Leenheer, J.A., Rostad, C.E., Gates, P.M., Furlong, E.T., Ferrer, I. "Molecular Resolution
and Fragmentation of Fulvic Acid by Electrospray lonization/Multistage Tandem Mass
Spectrometry." Anal. Chem. 2001, 73, 1461-1471.
4. Cahill, J.D., Furlong E.T., Burkhardt, M.R., Kolpin, D., Anderson, L.G. "Determination of
Pharmaceutical Compounds in Surface- and Ground-Water Samples by Solid-Phase
Extraction and High-Performance Liquid Chromatography Electrospray lonization Mass
Spectrometry." J. Chromatogr. A 2004, 1041, 171-180.
5. "OSHA Safety and Health Standards, General Industry," (29CRF1910). Occupational Safety
and Health Administration, OSHA 2206, (Revised, July 1, 2001).
6. "Carcinogens-Working with Carcinogens," Publication No. 77-206, Department of Health,
Education, and Welfare, Public Health Service, Center for Disease Control, National Institute
of Occupational Safety and Health, Atlanta, Georgia, August 1977.
538-28
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7. "Safety in Academic Chemistry Laboratories," American Chemical Society Publication,
Committee on Chemical Safety, 7th Edition. Information on obtaining a copy is available at
http://membership.acs.org/C/CCS/pub_3.htm (accessed November, 2009). Also available by
request at OSS@acs.org.
538-29
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17. TABLES, DIAGRAMS, FLOWCHARTS AND VALIDATION DATA
TABLE 1. LC METHOD CONDITIONS
Time (min)
Initial
3.0
5.0
8.0
20
20.1
25
25.1
30
% 20 mM Ammonium Formate
90.0
90.0
70.0
70.0
30.0
10.0
10.0
90.0
90.0
% Methanol
10.0
10.0
30.0
30.0
70.0
90.0
90.0
10.0
10.0
Waters Atlantis® TS 2.1 x 150 mm packed with 5.0 jim Cig stationary phase
Flow rate of 0.3 mL/min
50 jiL injection
TABLE 2. ESI-MS METHOD CONDITIONS
ESI Conditions
Polarity
Capillary needle voltage
Cone gas flow
Nitrogen desolvation gas flow
Desolvation gas temp.
Positive ion
+4kV
lOOL/hr
lOOOL/hr
350°C
538-30
-------
TABLE 3. METHOD ANALYTE RETENTION TIMES (RTs), AND
SUGGESTED IS REFERENCES
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Methamidophos-de
Acephate-de
Oxydemeton-methyl-de
Quinoline-d?
DIMP-di4
Peak#
(Fig. 1)
2
4
5
7
8
9
11
13
14
15
16
1
3
6
10
12
RT
(min)
3.66
5.24
6.51
7.50
9.59
14.74
15.77
16.65
17.63
18.07
18.79
3.57
5.16
7.44
15.57
16.44
IS#
Ref
1
2
2
3
3
3
4
5
3
3
5
IS#1
IS#2
IS#3
IS#4
IS#5
538-31
-------
TABLE 4. MS/MS METHOD CONDITIONS
a,b
Segment0
1
1
2
2
3
O
4
4
4
4
5
1
1
2
4
4
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Methamidophos-de
Acephate-de
Oxydemeton-methyl-de
Quinoline-d?
DIMP-di4
Precursor Iond
(m/z)
142
184
207
247
238
208
130
181
320
336
219
148
190
253
137
195
Product Iond'e
(m/z)
94
143
132
169
112
89
77
97
233
266
57
97
149
175
81
99
Cone
Voltage
(v)
20
20
20
20
25
10
35
15
30
30
20
20
20
20
35
15
Collision
Energyf
(v)
15
15
10
15
15
15
30
10
25
20
20
15
15
15
30
15
An LC/MS/MS chromatogram of the analytes is shown in Figure 1.
b These conditions were optimized during method development and used to collect the data in
Section 17. Optimum conditions may vary on different LC/MS/MS instruments.
Segments are time durations in which single or multiple scan events occur.
Precursor and product ions listed in this table are nominal masses. During MS and MS/MS
optimization, the analyst should determine the precursor and product ion masses to one
decimal place by locating the apex of the mass spectral peak (e.g., m/z 141.9—>93.9 for
methamidophos). These precursor and product ion masses (with one decimal place) should be
used in the MS/MS method for all analyses.
e Ions used for quantitation purposes.
f Argon used as collision gas at a flow rate of 0.3 mL/min.
538-32
-------
TABLE 5. DLs AND LCMRLs IN REAGENT WATER
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified Cone.
(Hg/L)a
0.050
0.050
0.10
0.050
0.050
0.10
2.1
0.050
0.050
0.050
0.20
DLb
(HS/L)
0.017
0.019
0.060
0.010
0.025
0.030
1.2
0.014
0.034
0.0087
0.090
LCMRLC
(HS/L)
0.032
0.044
0.088
0.019
0.039
0.030
1.5
0.022
0.042
0.011
0.18
Spiking concentration used to determine DL.
' Detection limits were determined by analyzing eight replicates over three days according to
Section 9.2.6.
LCMRLs were calculated according to the procedure in reference 1.
TABLE 6. PRECISION AND ACCURACY IN REAGENT WATER FORTIFIED AT
0.05-2.1 ug/L (n=8)
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified Cone. (ug/L)
0.050
0.050
0.10
0.050
0.050
0.10
2.1
0.050
0.050
0.050
0.20
Mean % Recovery
107
96.0
96.9
105
114
106
94.0
103
118
108
112
% RSD
11
13
21
6.5
15
9.5
20
9.2
19
5.4
13
538-33
-------
TABLE 7. PRECISION AND ACCURACY IN REAGENT WATER FORTIFIED AT
0.99-43 ug/L (n=7)
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified Cone. (ug/L)
0.99
0.99
2.0
0.99
0.99
2.0
43
0.99
0.99
0.99
4.0
Mean % Recovery
105
107
105
96.0
95.9
97.1
101
101
94.5
92.3
93.2
% RSD
1.3
4.3
1.9
3.6
5.2
4.9
5.3
3.3
6.5
4.7
4.2
TABLE 8. PRECISION AND ACCURACY IN CHLORINATED SURFACE WATER
FORTIFIED AT 0.05-2.1 ug/L (n=7)
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified Cone. (ug/L)
0.050
0.050
0.10
0.050
0.050
0.10
2.1
0.050
0.050
0.050
0.20
Mean % Recovery
102
113
106
99.8
93.9
116
97.4
98.9
111
111
119
% RSD
20
18
18
14
16
15
19
15
16
18
14
538-34
-------
TABLE 9. PRECISION AND ACCURACY IN CHLORINATED SURFACE WATER
FORTIFIED AT 0.99-43 ug/La (n=7)
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified Cone. (ug/L)
0.99
0.99
2.0
0.99
0.99
2.0
43
0.99
0.99
0.99
4.0
Mean % Recovery
102
103
98.4
101
98.4
112
98.5
102
110
113
95.2
% RSD
2.4
3.2
2.5
2.7
3.5
2.1
3.7
2.7
3.5
3.9
3.3
TOC = 1.49 mg/L and hardness = 120 mg/L as calcium carbonate.
TABLE 10. PRECISION AND ACCURACY IN FORTIFIED CHLORINATED
GROUND WATER FORTIFIED AT 0.99-43 ug/La (n=7)
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified Cone. (ug/L)
0.99
0.99
2.0
0.99
0.99
2.0
43
0.99
0.99
0.99
4.0
Mean % Recovery
98.1
106
102
97.0
95.6
103
94.3
99.2
101
102
89.3
% RSD
7.0
4.4
5.8
5.2
5.3
5.9
7.6
4.5
7.9
7.3
2.4
TOC = 0.726 mg/L and hardness = 342 mg/L as calcium carbonate.
538-35
-------
TABLE 11. PRECISION AND ACCURACY IN CHLORINATED SURFACE WATER
CONTAINING NATURAL ORGANIC MATERIAL3 AND FORTIFIED
WITH ANALYTES AT 0.99-43 ug/L (n=5)
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified Cone. (ug/L)
0.99
0.99
2.0
0.99
0.99
2.0
43
0.99
0.99
0.99
4.0
Mean % Recovery
102
106
98.6
103
102
109
98.8
103
114
116
104
% RSD
2.5
3.8
4.0
3.5
3.4
3.1
3.0
1.8
3.1
3.2
4.9
Prepared using commercially available (International Humic Substances Society) aquatic
natural organic matter (NOM) isolated from the Suwannee River. The chlorinated surface
water was fortified with NOM to obtain a TOC measurement of 8.7 mg/L.
538-36
-------
TABLE 12. AQUEOUS SAMPLE HOLDING TIME DATA FOR SAMPLES FROM CHLORINATED SURFACE WATER ,
FORTIFIED WITH METHOD ANALYTES AND PRESERVED AND STORED ACCORDING TO SECTION 8
(n=7)
Analyte
Methamidophos
Acephate
Aldicarb sulfoxide
Oxydemeton-methyl
Dicrotophos
Aldicarb
Quinoline
DIMP
Fenamiphos sulfoxide
Fenamiphos sulfone
Thiofanox
Fortified
Cone.
(HS/L)
0.99
0.99
2.0
0.99
0.99
2.0
43
0.99
0.99
0.99
4.0
DayO
Mean %Rec
94.4
105
97.7
92.9
91.4
104
97.8
96.8
102
101
87.7
% RSD
2.8
3.3
2.9
3.4
5.7
4.4
2.6
2.7
4.4
4.3
2.9
Day 7
Mean %Rec
97.5
106
100
85.9
94.5
110
98.0
98.5
112
117
88.1
% RSD
1.9
4.4
6.2
2.5
2.9
3.7
4.0
3.6
3.3
3.0
3.0
Day 14
Mean %Rec
91.1
94.7
84.5
80.0
93.1
97.6
99.9
98.3
99.0
99.6
101
% RSD
2.5
4.1
3.2
2.3
4.6
2.6
2.4
1.2
3.0
2.6
2.9
TOC = 1.49 mg/L, pH=9.0 and hardness =120 mg/L as calcium carbonate.
538-37
-------
TABLE 13. INITIAL DEMONSTRATION OF CAPABILITY QUALITY CONTROL REQUIREMENTS
Method
Reference
Sect. 9.2.1
Sect. 9.2.2
Sect. 9.2.3
Sect. 9.2.4
Sect. 9.2.5
and 9.3.7
Sect. 9.2.6
Requirement
Initial Demonstration of
Low System Background
Initial Demonstration of
Precision (IDP)
Initial Demonstration of
Accuracy (IDA)
Minimum Reporting Limit
(MRL) Confirmation
Quality Control Sample
(QCS)
Detection Limit (DL)
Determination (optional)
Specification and Frequency
Analyze LRB prior to any other IDC steps and any
time a new lot of solvents, reagents, and autosampler
vials are used.
Analyze four to seven replicate LFBs fortified near
the mid-range calibration concentration.
Calculate mean recovery for replicates used in IDP.
Fortify and analyze seven replicate LFBs at the
proposed MRL concentration. Calculate the Mean
and the Half Range (HR). Confirm that the upper
and lower limits for the Prediction Interval of Result
(Upper PIR, and Lower PIR, Sect. 9.2.4.2) meet the
recovery criteria.
Analyze a standard from a second source, as
part of the IDC, each time a new Analyte MEOH
PDS (Sect. 7.2.2.2) is prepared, and at least
quarterly.
Over a period of three days, prepare a minimum of
seven replicate LFBs fortified at a concentration
estimated to be near the DL. Analyze the replicates
through all steps of the analysis. Calculate the DL
using the equation in Sect. 9.2.6.
Acceptance Criteria
Demonstrate that all method analytes are below 1/3 the MRL
and that possible interferences do not prevent the
identification and quantification of method analytes.
%RSDmustbe <20%
Mean recovery ± 30% of true value
Upper PIR < 150%
Lower PIR > 50%
Results must be within 70-130% of expected value.
Data from DL replicates are not required to meet method
precision and accuracy criteria. If the DL replicates are
fortified at a low enough concentration, it is likely that they
will not meet precision and accuracy criteria for CCCs.
NOTE: Table 13 is intended as an abbreviated summary of QC requirements provided as a convenience to the method user. Because the information has been
abbreviated to fit the table format, there may be issues that need additional clarification, or areas where important additional information from the method text
is needed. In all cases, the full text of the QC in Section 9 supersedes any missing or conflicting information in this table.
538-38
-------
TABLE 14. ONGOING QUALITY CONTROL REQUIREMENTS (SUMMARY)
Method
Reference
Sect. 8.1 -
Sect. 8.4
Sect. 9.3.1
Sect. 9.3.3
Sect. 9.3.4
Sect. 9.3.5
Sect. 9.3.6
Sect. 9.3.7
Sect. 10.2
Sect. 9.3.2
and Sect.
10.3
Requirement
Sample Holding Time
Laboratory Reagent
Blank (LRB)
Laboratory Fortified
Blank (LFB)
Internal Standard (IS)
Laboratory Fortified
Sample Matrix
(LFSM)
Laboratory Fortified
Sample Matrix
Duplicate (LFSMD) or
Field Duplicates (FD)
Quality Control
Sample (QCS)
Initial Calibration
Continuing Calibration
Check (CCC)
Specification and Frequency
14 days with appropriate preservation and storage as
described in Sections 8.1-8.4.
One LRB with each analysis batch of up to 20 Field
Samples.
LFB not required unless LFSM fails QC criteria (Sect.
9.3.5.4).
Internal standards are added to all standards and
samples including QC samples. Compare IS areas to
the average IS areas in the most recent calibration.
Analyze one LFSM per analysis batch (20 samples or
less) fortified with method analytes at a concentration
close to but greater than the native concentration, if
known. Calculate LFSM recoveries.
Analyze at least one FD or LFSMD with each analysis
batch (20 samples or less). An LFSMD may be
substituted for a FD when the frequency of detects are
low. Calculate RPDs.
Analyze at least quarterly or when preparing new
standards, as well as during the IDC.
Use IS calibration technique to generate linear or
quadratic calibration curves. Use at least five
standard concentrations. Check the calibration curve
as described in Sect. 10.2.7.
Verify initial calibration by analyzing a low level (at
the MRL or below) CCC prior to analyzing samples.
CCCs are then injected after every 10 samples and
after the last sample, rotating concentrations to cover
the calibrated range of the instrument.
Acceptance Criteria
Sample results are valid only if samples are analyzed within the sample holding
time.
Demonstrate that all method analytes are below 1/3 the MRL, and confirm that
possible interferences do not prevent quantification of method analytes. If
targets exceed 1/3 the MRL or if interferences are present, results for these
subject analytes in the analysis batch are invalid.
If an LFB must be analyzed due to failure of the LFSM, results of LFB analyses
must be 70-130% of the true value for each method analyte for all except the
lowest standard, which should be 50-150% of the true value.
Peak areas (or calculated concentrations) for all ISs in all injections must be
within ±50% of the average peak areas calculated during the most recent
calibration. If this criterion is not met, results are labeled "suspect/IS recovery."
See Sect. 9.3.5 for instructions on the interpretation of LFSM results.
See Sect. 9.3.6 for instructions on the interpretation of LFSMD or FD results.
Results must be within 70-130% of expected value.
When each CAL standard is calculated as an unknown using the calibration
curve, the analyte results should be 70-130% of the true value for all except the
lowest standard, which should be 50-150% of the true value.
Recovery for each analyte must be within 70-130% of the true value for all but
the lowest level of calibration. Recovery for each analyte in the lowest CAL
level CCC must be within 50-150% of the true value.
NOTE: Table 14 is intended as an abbreviated summary of QC requirements provided as a convenience to the method user. Because the information has been abbreviated
to fit the table format, there may be issues that need additional clarification, or areas where important additional information from the method text is needed. In all
cases, the full text of the QC in Section 8-10 supersedes any missing or conflicting information in this table.
538-39
-------
FIGURE 1. EXAMPLE CHROMATOGRAM FOR REAGENT WATER FORTIFIED WITH METHOD 538 ANALYTES
AT CONCENTRATION LEVELS INDICATED IN TABLE 7. NUMBERED PEAKS ARE IDENTIFIED IN
TABLE 3.
100 i
6.'
12
.o
o
*
1,2
3,4
5
1
9
. 10
8 A n,11
I A 11 JKU
|U
"
"
Uul"
4.0 6.0 8.0 10.0 12-0 14.0 16.0 18.0 20
Retention Time, mill
538-40
------- |