ASTM D7731-17

Standard Test Method for Determination of Dipropylene Glycol Monobutyl Ether and Ethylene Glycol Monobutyl Ether in Sea Water by Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS)

SIGNIFICANCE AND USE
5.1 DPGBE and EGBE have a variety of residential and industrial applications such as cleaning formulations, surface coatings, inks, and cosmetics. These analytes may be released into the environment at levels that may be harmful to aquatic life.  
5.2 This test method has been investigated for use with reagent and sea water.
SCOPE
1.1 This test method covers the determination of dipropylene glycol monobutyl ether (DPGBE) and ethylene glycol monobutyl ether (EGBE) in sea water by direct injection using liquid chromatography (LC) and detection with tandem mass spectrometry (MS/MS). These analytes are qualitatively and quantitatively determined by this test method. This test method adheres to selected reaction monitoring (SRM) mass spectrometry.  
1.2 The detection verification level (DVL) and reporting range for DPGBE and EGBE are listed in Table 1.    
1.2.1 The DVL is required to be at a concentration at least 3 times below the reporting limit (RL) and have a signal/noise ratio greater than 3:1. Fig. 1 and Fig. 2 display the signal/noise ratio of the single reaction monitoring (SRM) transition.  
FIG. 1 Detection Verification Level Signal/Noise Ratio  
FIG. 2 Reporting Level (Calibration Standard) Signal/Noise Ratio  
1.2.2 The reporting limit is the concentration of the Level 1 calibration standard as shown in Table 4 for DPGBE and EGBE, taking into account the 20 % sample preparation dilution factor.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Dec-2017
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.06 - Methods for Analysis for Organic Substances in Water

Relations

• Replaces: ASTM D7731-11e1 - Standard Test Method for Determination of Dipropylene Glycol Monobutyl Ether and Ethylene Glycol Monobutyl Ether in Sea Water by Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS)
• Effective Date: 15-Dec-2017
• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D1129-06a - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006
• Refers: ASTM D1129-06ae1 - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006
• Refers: ASTM D2777-06 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Aug-2006
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D1129-06 - Standard Terminology Relating to Water
• Effective Date: 15-Feb-2006
• Refers: ASTM D1129-04e1 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2004
• Refers: ASTM D1129-04 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2004
• Refers: ASTM D1129-03a - Standard Terminology Relating to Water
• Effective Date: 10-Aug-2003
• Refers: ASTM D2777-03 - Standard Practice for Determination of Precision and Bias of Applicable Methods of Committee D-19 on Water
• Effective Date: 10-Aug-2003
• Refers: ASTM D1129-03 - Standard Terminology Relating to Water
• Effective Date: 10-Mar-2003

Overview

ASTM D7731-17 is a standardized test method developed by ASTM International for the determination of dipropylene glycol monobutyl ether (DPGBE) and ethylene glycol monobutyl ether (EGBE) in sea water. This method utilizes liquid chromatography with tandem mass spectrometry (LC/MS/MS) for both qualitative and quantitative analysis. By adhering to selected reaction monitoring (SRM) mass spectrometry, the standard aims to ensure accurate detection and reporting of these waterborne contaminants that originate from a range of industrial and residential applications.

DPGBE and EGBE have significant environmental impact when released into aquatic environments. ASTM D7731-17 provides laboratories, regulatory bodies, and industry professionals a reliable protocol to monitor and control the presence of these substances in marine ecosystems.

Key Topics

• Test Method Scope
  • Covers analysis of DPGBE and EGBE in sea water samples using direct injection LC/MS/MS.
  • Designed for both qualitative and quantitative determination with strict calibration and QC criteria.
  • Adheres to selected reaction monitoring (SRM) methodology for targeted detection.
  • Specifies use of SI units for results and includes detailed definitions of detection and reporting limits.
• Significance and Use
  • Highlights the widespread use of DPGBE and EGBE in products such as cleaning agents, coatings, inks, and cosmetics.
  • Stresses potential environmental risks, especially to aquatic life, from inadvertent release.
  • Test method validated for use with both reagent water and sea water matrices.
• Sample Handling and Analysis
  • Samples are collected in pre-cleaned glass vials and preserved at low temperatures prior to analysis.
  • Surrogate standards used to monitor procedural accuracy.
  • Detailed guidance on filtration, dilution, and injection to minimize contamination and ensure reproducibility.
• Calibration and Quality Control
  • Calibration curves built from multiple concentration levels.
  • Reporting and detection verification limits established based on robust signal-to-noise criteria.
  • Quality control includes method blanks, laboratory control samples, matrix spikes, and duplicate samples to ensure accuracy and precision.

Applications

ASTM D7731-17 is essential for:

• Environmental Monitoring: Detecting and quantifying glycol ether contaminants in sea water to assess pollution levels, guide remediation strategies, and conduct environmental impact assessments.
• Regulatory Compliance: Supporting governmental and industrial efforts to comply with water quality and chemical discharge regulations concerning hazardous organic compounds.
• Industrial Process Control: Enabling manufacturers of products containing DPGBE and EGBE, such as cleaners, paints, and inks, to monitor effluent and mitigate environmental risks.
• Research and Risk Assessment: Providing a scientifically sound approach for academics and environmental scientists studying the fate, transport, and impact of glycol ethers in marine environments.

Related Standards

• ASTM D1129: Terminology relating to water, foundational for understanding terms used in water analysis.
• ASTM D1193: Specification for reagent water, ensuring purity in laboratory procedures.
• ASTM D2777: Practice for determination of precision and bias in water analysis methods.
• EPA SW-846: Test methods for evaluating solid waste, offering reference quality control procedures relevant for laboratories.

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By following ASTM D7731-17, laboratories and environmental professionals can achieve sensitive, reliable, and standardized results for the measurement of dipropylene glycol monobutyl ether and ethylene glycol monobutyl ether in marine contexts. This promotes responsible environmental stewardship and regulatory compliance in the monitoring of potentially hazardous organic compounds in sea water.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D7731 −17
Standard Test Method for
Determination of Dipropylene Glycol Monobutyl Ether and
Ethylene Glycol Monobutyl Ether in Sea Water by Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS)
This standard is issued under the fixed designation D7731; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers the determination of dipropyl- 2.1 ASTM Standards:
ene glycol monobutyl ether (DPGBE) and ethylene glycol D1129Terminology Relating to Water
monobutyl ether (EGBE) in sea water by direct injection using D1193Specification for Reagent Water
liquid chromatography (LC) and detection with tandem mass D2777Practice for Determination of Precision and Bias of
spectrometry (MS/MS). These analytes are qualitatively and Applicable Test Methods of Committee D19 on Water
quantitativelydeterminedbythistestmethod.Thistestmethod 2.2 Other Standards:
adherestoselectedreactionmonitoring(SRM)massspectrom- EPAPublication SW-846Test Methods for Evaluating Solid
etry. Waste, Physical/Chemical Methods
1.2 The detection verification level (DVL) and reporting
3. Terminology
range for DPGBE and EGBE are listed in Table 1.
3.1 Definitions:
1.2.1 The DVL is required to be at a concentration at least
3.1.1 For definitions of terms used in this standard, refer to
3 times below the reporting limit (RL) and have a signal/noise
Terminology D1129.
ratiogreaterthan3:1.Fig.1andFig.2displaythesignal/noise
ratio of the single reaction monitoring (SRM) transition. 3.2 Definitions of Terms Specific to This Standard:
1.2.2 The reporting limit is the concentration of the Level 1
3.2.1 detection verification level, DVL, n—a concentration
calibration standard as shown in Table 4 for DPGBE and that has a signal/noise ratio greater than 3:1 and is at least 3
EGBE, taking into account the 20 % sample preparation
times below the reporting limit (RL).
dilution factor.
3.2.2 reporting limit, RL, n—the concentration of the
lowest-level calibration standard used for quantification.
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this 3.2.2.1 Discussion—In this test method, a 20-mL sample
aliquot is diluted to a 25-mL final volume after thoroughly
standard.
rinsing the collection vial with acetonitrile for quantitative
1.4 This standard does not purport to address all of the
transfer.Inthiscase,thelowestcalibrationlevelof100ppbfor
safety concerns, if any, associated with its use. It is the
EGBE would allow for a reporting limit of 125 ppb to be
responsibility of the user of this standard to establish appro-
achieved.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3.3 Abbreviations:
–3
1.5 This international standard was developed in accor- 3.3.1 mM—millimolar,1×10 moles/L
dance with internationally recognized principles on standard-
3.3.2 NA—no addition
ization established in the Decision on Principles for the
3.3.3 ND—non-detect
Development of International Standards, Guides and Recom-
3.3.4 ppb—parts per billion, µg/L
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
3.3.5 ppt—parts per trillion, ng/L
1 2
This test method is under the jurisdiction ofASTM Committee D19 on Water For referenced ASTM standards, visit the ASTM website, www.astm.org, or
andisthedirectresponsibilityofSubcommitteeD19.06onMethodsforAnalysisfor contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Organic Substances in Water. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 15, 2017. Published January 2018. Originally the ASTM website.
ε1 3
approved in 2011. Last previous edition approved in 2011 as D7731 – 11 . DOI: Available from NationalTechnical Information Service (NTIS), 5301 Shawnee
10.1520/D7731-17. Rd., Alexandria, VA 22312, http://www.ntis.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7731−17
TABLE 1 Detection Verification Level (DVL) and Reporting Range
6.4 Matrix interferences may be caused by contaminants in
DVL Reporting Range the sample. The extent of matrix interferences can vary
Analyte
(µg/L) (µg/L)
considerably from sample source depending on variations of
DPGBE 0.2 1–10
the sample matrix.
EGBE 25 125–1250
7. Apparatus
7.1 LC/MS/MS System:
4. Summary of Test Method
7.1.1 Liquid Chromatography System—Acomplete LC sys-
4.1 This is a performance-based method, and modifications
tem is needed in order to analyze samples. Any system that is
are allowed to improve performance.
capable of performing at the flows, pressures, controlled
4.2 ForDPGBEandEGBEanalysis,samplesareshippedto
temperatures, sample volumes, and requirements of the stan-
the lab between 0°C and 6°C and analyzed within 5 days of
dard may be used.
collection. The DOW MSDS sheet on DOWANOL*DPNB
7.1.2 Analytical Column—Waters XBridge, 2.1 × 150 mm,
glycol ether (DPGBE) (Issue Date: 06/18/2010) lists that the
3.5-µm particle size was used to develop this test method.Any
material is readily biodegradable. The Organisation for Eco-
columnthatachievesbaselineresolutionoftheseanalytesmay
nomicCo-OperationandDevelopment(OECD)302BTestlists
be used. Baseline resolution simplifies data analysis and can
96 % biodegradation in 28 days.
reduce the chance of ion suppression, leading to higher limits
of detection. The retention times and order of elution may
4.3 In the lab, the entire collected 20-mL sample is spiked
change depending on the column used and need to be moni-
with surrogate and brought to a volume of 25 mL with
tored.
acetonitrile. This prepared sample is then filtered using a
7.1.3 Tandem Mass Spectrometer System—A MS/MS sys-
syringe driven filter unit, and analyzed by LC/MS/MS. If
tem capable of SRM analysis. Any system that is capable of
visible oil is present, the prepared sample is allowed to settle
performing at the requirements in this procedure may be used.
resulting in an oil layer at the top of the 25-mL solution. A
portionoftheaqueous(bottom)layerisfiltered,leavingtheoil
7.2 Filtration Device:
layer behind, through a syringe driven filter assembly and
7.2.1 Hypodermic Syringe—A lock-tip glass syringe ca-
analyzed by LC/MS/MS.
pableofholdingaMillexHVSyringeDrivenFilterUnitPVDF
7,8
0.22 µm, or similar, may be used.
4.4 DPGBE, EGBE, and surrogate are identified by reten-
7.2.1.1 A25-mLlock-tip glass syringe size was used in this
tion time and one SRM transition. The target analytes and
test method.
surrogatearequantitatedusingtheSRMtransitionsutilizingan
7.2.2 Filter—Millex HV Syringe Driven Filter Unit PVDF
external calibration. The final report issued for each sample
0.22 µm, or similar, may be used.
lists the concentration of DPGBE, EGBE, and the surrogate
recovery.
8. Reagents and Materials
5. Significance and Use
8.1 Purity of Reagents—High Performance Liquid Chroma-
tography (HPLC) pesticide residue analysis and spectropho-
5.1 DPGBE and EGBE have a variety of residential and
industrial applications such as cleaning formulations, surface tometry grade chemicals shall be used in all tests. Unless
indicated otherwise, it is intended that all reagents shall
coatings, inks, and cosmetics. These analytes may be released
into the environment at levels that may be harmful to aquatic conform to the Committee on Analytical Reagents of the
American Chemical Society. Other reagent grades may be
life.
5.2 This test method has been investigated for use with
reagent and sea water.
AWatersAllianceHighPerformanceLiquidChromatography(HPLC)System,
a trademark of the Waters Corporation, Milford, MA, was used to develop this test
6. Interferences
method. All parameters in this test method are based on this system and may vary
depending on your instrument.
6.1 Methodinterferencesmaybecausedbycontaminantsin
The Waters XBridge is a trademark of the Waters Corporation, Milford, MA.
solvents, reagents, glassware, and other apparatus producing 6
A Waters Quattro micro API tandem quadrupole mass spectrometer, a trade-
markoftheWatersCorporation,Milford,MA,wasusedtodevelopthistestmethod.
discrete artifacts or elevated baselines. All of these materials
Allparametersinthistestmethodarebasedonthissystemandmayvarydepending
are demonstrated to be free from interferences by analyzing
on your instrument.
laboratory reagent blanks under the same conditions as
The sole source of supply of the Millex HV Syringe Driven Filter Unit PVDF
samples.
0.45 µm known to the committee at this time is Millipore Corporation, Catalog #
SLHV033NS. If you are aware of alternative suppliers, please provide this
6.2 All glassware is washed in hot water with detergent and
information to ASTM International Headquarters. Your comments will receive
rinsed in hot water followed by distilled water. Detergents
careful consideration at a meeting of the responsible technical committee, which
you may attend.
containing DPGBE or EGBE must not be used. The glassware
Millex is a trademark of Merck KGAA, Darmstadt, Germany.
is then dried and heated in an oven at 250°C for 15 to 30
Reagent Chemicals, American Chemical Society Specifications, American
minutes. All glassware is subsequently cleaned with acetone
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
followed by methanol. listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
6.3 All reagents and solvents should be pesticide residue
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
purity or higher to minimize interference problems. MD.
D7731−17
FIG. 1Detection Verification Level Signal/Noise Ratio
FIG. 2Reporting Level (Calibration Standard) Signal/Noise Ratio
D7731−17
used provided they are first determined to be of sufficiently 11. Preparation of Apparatus
highpuritytopermittheirusewithoutaffectingtheaccuracyof
11.1 Liquid Chromatograph Operating Conditions:
the measurements.
11.1.1 Injection volumes of all calibration standards and
8.2 Purity of Water—Unless otherwise indicated, references
samplesaremadeat100-µLvolume.Thefirstsampleanalyzed
towatershallbeunderstoodtomeanreagentwaterconforming
after the calibration curve is a blank to ensure there is no
toType1ofSpecificationD1193.Itmustbedemonstratedthat
carry-over. The gradient conditions for the liquid chromato-
this water does not contain contaminants at concentrations
graphareshowninTable2.Divertthecolumnflowawayfrom
sufficient to interfere with the analysis.
the electrospray source from 0 to 5 minutes after injection.
Flow diversion to waste may be done using the mass spec-
8.3 Gases—Ultrapure nitrogen and argon.
trometer divert valve. Divert tubing configurations vary from
8.4 Acetonitrile (CAS # 75-05-8).
manual injection. Sea water samples contain nonvolatile salts,
8.5 Methanol (CAS # 67-56-1).
the first 5 minute elution is diverted in order to keep the mass
spectrometer source clean.
8.6 Formic Acid (CAS # 64-18-6).
11.2 LC Conditions:
8.7 2–Propanol (CAS # 67-63-0).
11.2.1 Needle Wash Solvent—60 % Acetonitrile/40 %
8.8 DPGBE—DipropyleneGlycolMonobutylEther(CAS#
2-propanol.
29911-28-2).
11.2.2 Temperatures—Column, 30°C; sample compartment,
8.9 EGBE—Ethylene Glycol Monobutyl Ether (CAS # 111-
15°C.
76-2).
11.2.3 Seal Wash—60 % Acetonitrile/40 % 2-propanol.
8.10 n-NP2EO—normal-Nonylphenol Diethoxylate (CAS #
11.3 Mass Spectrometer Parameters:
Not available).
11.3.1 To acquire the maximum number of data points per
8.11 EGBE-D (2-butoxyethanol (1,1,2,2-D )) (Optional
4 4
SRM channel while maintaining adequate sensitivity, the tune
Surrogate, Unlabeled CAS # 111-76-2).
parameters may be optimized according to your instrument.
Each peak requires at least 10 scans per peak for adequate
9. Hazards
quantitation.ThisprocedurecontainsDPGBE,EGBE,andone
9.1 Normal laboratory safety applies to this test method.
surrogate which are in three SRM acquisition functions to
Analysts should wear safety glasses, gloves, and lab coats
optimize sensitivity. Variable parameters regarding retention
when working in the lab.Analysts should review the Material
times, SRM transitions, and cone and collision energies are
Safety Data Sheets (MSDS) for all reagents used in this test
shown in Table 3. Mass spectrometer parameters used in the
method.
development of this test method are listed here:
Capillary Voltage: 3.5 kV
10. Sampling
Cone: Variable depending on analyte (Table 3)
10.1 Sampling and Preservation–—Grab samples should be Extractor: 2 Volts
RF Lens: 0.2 Volts
collected in 20-mL pre-cleaned glass vials with TFE-
Source Temperature: 120°C
fluorocarbon–lined septa caps demonstrated to be free of
Desolvation Temperature: 350°C
Desolvation Gas Flow: 800 L/hr
interferences. The vial should be filled to approximately 20
Cone Gas Flow: 25 L/hr
mL.This may be just below the neck of the vial, depending on
Low Mass Resolution 1: 14.5
the vial manufacturer. This test method is based on a 20-mL
High Mass Resolution 1: 14.5
sample size per analysis. Each sample should be collected in Ion Energy 1: 0.5
Entrance Energy: –1
duplicate and a quadruplicate sample must be included with
Collision Energy: Variable depending on analyte (Table 3)
eachsamplebatchof10forMS/MSDqualitycontrolanalyses.
Exit Energy: 1
Low Mass Resolution 2: 14.5
Store samples between 0°C and 6°C from sample collection to
High Mass resolution 2: 14.5
sample preparation. Analyze the sample within five days of
Ion Energy 2: 0.8
collection.
Multiplier: 650
-3
Gas Cell Pirani Gauge: 7.0 × 10 Torr
Inter-Channel Delay: 0.1 seconds
Inter-Scan Delay: 0.1 seconds
Dwell: 0.1 seconds
Solvent Delay: 5 minutes
TABLE 2 Gradient Conditions for Liquid Chromatography
Percent 95 % Water/ 5 % Percent 2 % Formic Acid 95 %
Time (min) Flow (mL/min) Percent CH CN
CH CN Water/ 5 % CH CN
3 3
0.0 0.30 95 0 5
2.0 0.30 95 0 5
5.0 0.30 0 95 5
14.0 0.30 0 95 5
15.0 0.30 95 0 5
18.0 0.30 95 0 5
D7731−17
TABLE 3 Retention Times, SRM transitions, and Specific Mass Spectrometer Parameters
SRM Mass Transition
Analyte Retention time (min) Cone Voltage (Volts) Collision Energy (eV)
(Precursor > Product)
DPGBE 8.5 19 7 191.3 > 115.1
EGBE 7.6 13 5 119.1 > 62.9
n-NP2EO (Surrogate) 11.2 28 10 309.3 > 89.0
EGBE-D (Optional Surrogate) 7.6 13 5 123.0 > 66.8
12. Calibration and Standardization should be consulted to use the software correctly. The quanti-
tation method is set as an external calibration using the peak
12.1 The mass spectrometer must be calibrated in accor-
areas in ppb units. Concentrations may be calculated using the
dance with manufacturer specifications before analysis. In
data system software to generate linear regression or quadratic
order to obtain accurate analytical values through using this
calibration curves. Forcing the calibration curve through the
test method within the confidence limits, the following proce-
origin is not recommended.
dures must be followed when performing this test method.
12.2.4 Linear calibration may be used if the coefficient of
Prepare all solutions in the lab using Class A volumetric
determination, r , is >0.98 for the analyte. The point of origin
glassware.
is excluded and a fit weighting of 1/X is used in order to give
12.2 Calibration and Standardization—To calibrate the
more emphasis to the lower concentrations. If one of the
instrument, analyze six calibration standards and the DVL
calibration standards other than the high or low point causes
containing(nominalconcentrationsinTable4)DPGBE,EGBE
ther ofthecurvetobe<0.98,thispointmustbere-injectedor
and n-NP2EO.Acalibrationsolutionispreparedfromstandard
anewcalibrationcurvemustberegenerated.Iftheloworhigh
materials or they are purchased as certified solutions. Level 6
point, or both, is excluded, minimally a five-point curve is
calibration solution containing the targets and surrogate is
acceptable but the reporting range must be modified to reflect
prepared and aliquots of that solution are diluted to prepare
this change.
Levels 1 through 5 and the DVL. The following steps will
12.2.5 Quadratic calibration may be used if the coefficient
produce standards with the concentration values shown in
of determination, r , is >0.99 for the analyte. The point of
Table 4. The analyst is responsible for recording initial
origin is excluded, and a fit weighting of 1/X is used in order
component weights correctly and calculating and preparing
to give more emphasis to the lower concentrations. If one of
appropriate dilution calculations.
the calibration standards causes the curve to be <0.99, this
12.2.1 Prepare Level 6 calibration stock standard at 1000
point must be re-injected or a new calibration curve must be
ppb for EGBE, 8 ppb for DPGBE and 40 ppb for n-NP2EO in
regenerated. Minimally a six point curve is acceptable using a
80 % water/20 % acetonitrile. The EGBE and DPGBE con-
quadratic fit. Each calibration point used to generate the curve
centratedstocksolutionswerepreparedinmethanolatapproxi-
must have a calculated percent deviation less than 25 % from
mately 2-g/L concentration and the n-NP2EO surrogate con-
the generated curve.
centrated stock solution was prepared in acetonitrile at
12.2.6 The retention time window of the SRM transitions
approximately 0.5 g/L. The preparation of the stock standard
must be within5%ofthe retention time of the analyte in a
can be accomplished using different volumes and concentra-
midpointcalibrationstandard.Ifthisisnotthecase,re-analyze
tions of stock solutions as is accustomed in the individual
the calibration curve to determine if there was a shift in
laboratory. Depending on the prepared stock concentrations,
retention time during the analysis and re-inject the sample. If
the solubility at that concentration will have to be ensured.
the retention time is still incorrect in the sample, refer to the
12.2.2 Aliquots of Level 6 calibration stock standard are
analyte as an unknown.
then diluted with 80 % water/20 % acetonitrile to prepare the
desired calibration levels in 2-mL amber glass autosampler 12.2.7 A calibration midpoint check standard must be ana-
vials. The calibration vials must be used within 24 hours to lyzedattheendofeachbatchof20samplesorwithin24hours
ensure optimum results. Stock calibration standards are rou- after the initial calibration curve was generated. This end
tinelyreplacedeverysevendaysifnotpreviouslydiscardedfor calibration check should be the same calibration standard that
quality control failure. Calibration standards are not filtered. wasusedtogeneratetheinitialcurve.Theresultsfromtheend
12.2.3 Injecteachstandardandobtainitschromatogram.An calibration check standard must have a percent deviation less
external calibration technique is used to monitor the SRM than 35 % from the calculated concentration for the target
analytes and surrogates. If the results are not within these
transitions of each analyte. Calibration software is utilized to
conduct the quantitation of the target analytes and surrogates criteria,theproblemmustbecorrectedandeitherallsamplesin
using the SRM transition. The calibration software manual the batch must be re-analyzed against a new calibration curve
TABLE 4 Concentrations of Calibration Standards (PPB)
Analyte/Surrogate DVL LV1 LV2 LV3 LV4 LV5 LV6
DPGBE 0.20 0.80 1.6 2.4 3.2 4.0 8.0
EGBE 25 100 200 300 400 500 1000
n-NP2EO 1.0 4.0 8.0 12162040
(Surrogate)
D7731−17
or the affected results must be qualified with an indication that 12.4.1.1 n-NP2EO has been shown to be absorbed into the
they do not fall within the performance criteria of this test oillayeryieldinganon-detectasaresult.Ifoilispresentinthe
method. If the analyst inspects the vial containing the end sample, the recovery of the n-NP2EO surrogate may be very
calibration check standards and notices that the samples low or not detected at or above the reporting limit.
evaporated affecting the concentration, a new end calibration
12.5 Method Blank:
check standard may be made and analyzed. If this new end
12.5.1 Analyze a reagent water blank with each batch of 20
calibration check standard has a percent deviation less than 35
orfewersamples.TheconcentrationoftheDPGBEandEGBE
% from the calculated concentration for the target analyte and
foundintheblankmustbebelowtheDVL.Iftheconcentration
surrogate, the results may be reported unqualified.
of DPGBE or EGBE is found above this level, analysis of
12.3 If a laboratory has not performed the test before or if
samples is halted until the contamination is eliminated, and a
there has been a major change in the measurement system, for
blank shows no contamination at or above this level, or the
example,
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This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D7731 − 11 D7731 − 17
Standard Test Method for
Determination of Dipropylene Glycol Monobutyl Ether and
Ethylene Glycol Monobutyl Ether in Sea Water by Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS)
This standard is issued under the fixed designation D7731; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—This test method was changed editorially in August 2011.
1. Scope
1.1 This procedure test method covers the determination of Dipropylene Glycol Monobutyl Ether (DPGBE) and Ethylene
Glycol Monobutyl Etherdipropylene glycol monobutyl ether (DPGBE) and ethylene glycol monobutyl ether (EGBE) in sea water
by direct injection using liquid chromatography (LC) and detection with tandem mass spectrometry (MS/MS). These analytes are
qualitatively and quantitatively determined by this test method. This test method adheres to selected reaction monitoring (SRM)
mass spectrometry.
1.2 The Detection Verification Leveldetection verification level (DVL) and Reporting Rangereporting range for DPGBE and
EGBE are listed in Table 1.
1.2.1 The DVL is required to be at a concentration at least 3 times below the Reporting Limitreporting limit (RL) and have a
signal/noise ratio greater than 3:1. Fig. 1 and Fig. 2 display the signal/noise ratio of the single reaction monitoring (SRM)
transition.
1.2.2 The reporting limit is the concentration of the Level 1 calibration standard as shown in Table 4 for DPGBE and EGBE,
taking into account the 20% 20 % sample preparation dilution factor.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
2.2 Other Standards:
EPA publicationPublication SW-846 Test Methods for Evaluating Solid Waste, Physical/Chemical Methods
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.
This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
Organic Substances in Water.
Current edition approved May 1, 2011Dec. 15, 2017. Published June 2011January 2018. Originally approved in 2011. Last previous edition approved in 2011 as D7731
ε1
– 11 . DOI: 10.1520/D7731-11E01.10.1520/D7731-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from National Technical Information Service (NTIS), U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA, 22161 or at http://www.epa.gov/
epawaste/hazard/testmethods/index.htm5301 Shawnee Rd., Alexandria, VA 22312, http://www.ntis.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7731 − 17
TABLE 1 Detection Verification Level (DVL) and Reporting Range
DVL Reporting Range
Analyte
(μg/L) (μg/L)
DPGBE 0.2 1–10
EGBE 25 125–1250
3.2 Definitions:Definitions of Terms Specific to This Standard:
3.2.1 detection verification level, DVL, n—a concentration that has a signal/noise ratio greater than 3:1 and is at least 3 times
below the Reporting Limitreporting limit (RL).
3.2.2 reporting limit, RL, n—the concentration of the lowest-level calibration standard used for quantification.
3.2.2.1 Discussion—
In this test method, a 20 mL 20-mL sample aliquot is diluted to a 25 mL 25-mL final volume after thoroughly rinsing the collection
vial with acetonitrile for quantitative transfer. In this case, the lowest calibration level of 100 ppb for EGBE would allow for a
reporting limit of 125 ppb to be achieved.
3.3 Symbols:Abbreviations:
3.2.1 ppb—parts per billion, μg/L
–3
3.3.1 mM—millimolar, 1 × 10 moles/L
3.2.2 ppt—parts per trillion, ng/L
3.3.2 NA—no addition
-3
3.2.3 mM—millimolar, 1 x 10 moles/L
3.3.3 ND—non-detect
3.2.4 NA—no addition
3.3.4 ppb—parts per billion, μg/L
3.2.5 ND—non-detect
3.3.5 ppt—parts per trillion, ng/L
D7731 − 17
FIG. 1 Detection Verification Level Signal/Noise Ratio.Ratio
FIG. 2 Reporting Level (Calibration standard)Standard) Signal/Noise Ratio.Ratio
D7731 − 17
4. Summary of Test Method
4.1 This is a performance based performance-based method, and modifications are allowed to improve performance.
4.2 For DPGBE and EGBE analysis, samples are shipped to the lab between 0°C and 6°C and analyzed within 5 days of
collection. The DOW MSDS sheet on DOWANOL* DPNB DOWANOL*DPNB glycol ether (DPGBE) Issue(Issue Date:
06/18/201006/18/2010) lists that the material is readily biodegradable. The Organisation for Economic Co-Operation and
Development (OECD) 302B Test lists 96% 96 % biodegradation in 28 days.
4.3 In the lab, the entire collected 20 mL 20-mL sample is spiked with surrogate and brought to a volume of 25 mL with
acetonitrile. This prepared sample is then filtered using a syringe driven filter unit, and analyzed by LC/MS/MS. If visible oil is
present, the prepared sample is allowed to settle resulting in an oil layer at the top of the 25 mL 25-mL solution. A portion of the
aqueous (bottom) layer is filtered, leaving the oil layer behind, through a syringe driven filter assembly and analyzed by
LC/MS/MS.
4.4 DPGBE, EGBE, and surrogate are identified by retention time and one SRM transition. The target analytes and surrogate
are quantitated using the SRM transitions utilizing an external calibration. The final report issued for each sample lists the
concentration of DPGBE, EGBE, and the surrogate recovery.
5. Significance and Use
5.1 DPGBE and EGBE have a variety of residential and industrial applications such as cleaning formulations, surface coatings,
inks, and cosmetics. These analytes may be released into the environment at levels that may be harmful to aquatic life.
5.2 This test method has been investigated for use with reagent and sea water.
6. Interferences
6.1 Method interferences may be caused by contaminants in solvents, reagents, glassware, and other apparatus producing
discrete artifacts or elevated baselines. All of these materials are demonstrated to be free from interferences by analyzing laboratory
reagent blanks under the same conditions as samples.
6.2 All glassware is washed in hot water with detergent and rinsed in hot water followed by distilled water. Detergents
containing DPGBE or EGBE must not be used. The glassware is then dried and heated in an oven at 250°C for 15 to 30 minutes.
All glassware is subsequently cleaned with acetone followed by methanol.
6.3 All reagents and solvents should be pesticide residue purity or higher to minimize interference problems.
6.4 Matrix interferences may be caused by contaminants in the sample. The extent of matrix interferences can vary considerably
from sample source depending on variations of the sample matrix.
7. Apparatus
7.1 LC/MS/MS SystemLC/MS/MS System:
7.1.1 Liquid Chromatography System—A complete LC system is needed in order to analyze samples. Any system that is
capable of performing at the flows, pressures, controlled temperatures, sample volumes, and requirements of the standard may be
used.
7.1.2 Analytical Column—Waters- XBridge™,Waters XBridge, 2.1 x× 150 mm, 3.5 μm 3.5-μm particle size was used to
develop this test method. Any column that achieves baseline resolution of these analytes may be used. Baseline resolution
simplifies data analysis and can reduce the chance of ion suppression, leading to higher limits of detection. The retention times
and order of elution may change depending on the column used and need to be monitored.
7.1.3 Tandem Mass Spectrometer System—A MS/MS system capable of SRM analysis. Any system that is capable of
performing at the requirements in this procedure may be used.
7.2 Filtration Device:
7.2.1 Hypodermic syringe—Syringe—A Lock Tip Glass Syringe lock-tip glass syringe capable of holding a Millex®Millex HV
7,8
Syringe Driven Filter Unit PVDF 0.22 μm, or similar, may be used.
7.2.1.1 A 25 mL Lock Tip Glass Syringe 25-mL lock-tip glass syringe size was used in this test method.
A Waters Alliance High Performance Liquid Chromatography (HPLC) System System, a trademark of the Waters Corporation, Milford, MA, was used to develop this
test method. All parameters in this test method are based on this system and may vary depending on your instrument.
The Waters XBridge is a trademark of the Waters Corporation, Milford, MA.
A Waters Quattro micro API tandem quadrupole mass spectrometer spectrometer, a trademark of the Waters Corporation, Milford, MA, was used to develop this test
method. All parameters in this test method are based on this system and may vary depending on your instrument.
The sole source of supply of the Millex HV Syringe Driven Filter Unit PVDF 0.45 μm known to the committee at this time is Millipore Corporation, Catalog #
SLHV033NS. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration
at a meeting of the responsible technical committee, which you may attend.
Millex is a trademark of Merck KGAA, Darmstadt, Germany.
D7731 − 17
7.2.2 Filter—Millex®Millex HV Syringe Driven Filter Unit PVDF 0.22 μm (Millipore Corporation, Catalog #SLGV033NS) or
similarμm, or similar, may be used.
8. Reagents and Materials
8.1 Purity of Reagents—High Performance Liquid Chromatography (HPLC) pesticide residue analysis and spectrophotometry
grade chemicals shall be used in all tests. Unless indicated otherwise, it is intended that all reagents shall conform to the Committee
on Analytical Reagents of the American Chemical Society. Other reagent grades may be used provided they are first determined
to be of sufficiently high purity to permit their use without affecting the accuracy of the measurements.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to
ASTM Type 1 of Specification D1193. It must be demonstrated that this water does not contain contaminants at concentrations
sufficient to interfere with the analysis.
8.3 Gases—Ultrapure nitrogen and argon.
8.4 Acetonitrile (CAS # 75-05-8).
8.5 Methanol (CAS # 67-56-1).
8.6 Formic Acid (CAS # 64-18-6).
8.7 2–Propanol (CAS # 67-63-0).
8.8 DPGBE—Dipropylene Glycol Monobutyl Ether (CAS # 29911-28-2).
8.9 EGBE—Ethylene Glycol Monobutyl Ether (CAS# (CAS # 111-76-2).
8.10 n-NP2EO—normal- Nonylphenol Diethoxylate (CAS# normal-Nonylphenol Diethoxylate (CAS # Not available).
8.11 EGBE-D (2-butoxyethanol (1,1,2,2-D )) (Optional Surrogate, Unlabeled CAS# 111-76- 2).CAS # 111-76-2).
4 4
9. Hazards
9.1 Normal laboratory safety applies to this test method. Analysts should wear safety glasses, gloves, and lab coats when
working in the lab. Analysts should review the Material Safety Data Sheets (MSDS) for all reagents used in this test method.
10. Sampling
10.1 Sampling and Preservation–—Grab samples should be collected in 20 mL 20-mL pre-cleaned glass vials with Teflon®
lined TFE-fluorocarbon–lined septa caps demonstrated to be free of interferences. The vial should be filled to approximately 20
mL. This may be just below the neck of the vial, depending on the vial manufacturer. This test method is based on a 20 mL 20-mL
sample size per analysis. Each sample should be collected in duplicate and a quadruplicate sample must be included with each
sample batch of 10 for MS/MSD quality control analyses. Store samples between 0°C and 6°C from sample collection to sample
preparation. Analyze the sample within 5five days of collection.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, D.C.DC. For Suggestionssuggestions on the testing of reagents
not listed by the American Chemical Society, see AnnualAnalar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
and National Formulators,Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D7731 − 17
11. Preparation of Apparatus
11.1 Liquid Chromatograph Operating Conditions:
11.1.1 Injection volumes of all calibration standards and samples are made at 100 μL 100-μL volume. The first sample analyzed
after the calibration curve is a blank to ensure there is no carry-over. The gradient conditions for the liquid chromatograph are
shown in Table 2. Divert the column flow away from the electrospray source from 0 to 5 minutes after injection. Flow diversion
to waste may be done using the mass spectrometer divert valve. Divert tubing configurations vary from manual injection. Sea water
samples contain nonvolatile salts, the first 5 minute elution is diverted in order to keep the mass spectrometer source clean.
11.2 LC Conditions:
11.2.1 Needle Wash Solvent—60% Acetonitrile/40% 2-propanol60 % Acetonitrile/40 % 2-propanol.
11.2.2 Temperatures—Column, 30°C; Samplesample compartment, 15°C.
11.2.3 Seal Wash—60% Acetonitrile/40% 60 % Acetonitrile/40 % 2-propanol.
11.3 Mass Spectrometer Parameters:
11.3.1 To acquire the maximum number of data points per SRM channel while maintaining adequate sensitivity, the tune
parameters may be optimized according to your instrument. Each peak requires at least 10 scans per peak for adequate quantitation.
This procedure contains DPGBE, EGBE, and one surrogate which are in three SRM acquisition functions to optimize sensitivity.
Variable parameters regarding retention times, SRM transitions, and cone and collision energies are shown in Table 3Table 3. .
Mass spectrometer parameters used in the development of this test method are listed here:
Capillary Voltage: 3.5 kV
Cone: Variable depending on analyte (Table 3)
Extractor: 2 Volts
RF Lens: 0.2 Volts
Source Temperature: 120°C
Desolvation Temperature: 350°C
Desolvation Gas Flow: 800 L/hr
Cone Gas Flow: 25 L/hr
Low Mass Resolution 1: 14.5
High Mass Resolution 1: 14.5
Ion Energy 1: 0.5
Entrance Energy: -1
Collision Energy: Variable depending on analyte (Table 3)
Exit Energy: 1
Low Mass Resolution 2: 14.5
High Mass resolution 2: 14.5
Ion Energy 2: 0.8
Multiplier: 650
-3
Gas Cell Pirani Gauge: 7.0 x 10 Torr
Inter-Channel Delay: 0.1 seconds
Inter-Scan Delay: 0.1 seconds
Dwell: 0.1 seconds
Solvent Delay: 5 minutes
Capillary Voltage: 3.5 kV
Cone: Variable depending on analyte (Table 3)
Extractor: 2 Volts
RF Lens: 0.2 Volts
Source Temperature: 120°C
Desolvation Temperature: 350°C
Desolvation Gas Flow: 800 L/hr
Cone Gas Flow: 25 L/hr
Low Mass Resolution 1: 14.5
TABLE 2 Gradient Conditions for Liquid Chromatography
Percent 2% 2 % Formic Acid
Percent 95% Water/ 5% 95 %
Time (min) Flow (mL/min) Percent CH CN 95% Water/ 5% 95 % Water/ 5
Water/ 5 % CH CN
% CH CN
0.0 0.30 95 0 5
2.0 0.30 95 0 5
5.0 0.30 0 95 5
14.0 0.30 0 95 5
15.0 0.30 95 0 5
18.0 0.30 95 0 5
D7731 − 17
TABLE 3 Retention Times, SRM transitions, and Specific Mass Spectrometer Parameters
SRM Mass Transition
Analyte Retention time (min) Cone Voltage (Volts) Collision Energy (eV)
(Precursor > Product)
DPGBE 8.5 19 7 191.3 > 115.1
EGBE 7.6 13 5 119.1 > 62.9
n-NP2EO (Surrogate) 11.2 28 10 309.3 > 89.0
EGBE-D (Optional Surrogate) 7.6 13 5 123.0 > 66.8
High Mass Resolution 1: 14.5
Ion Energy 1: 0.5
Entrance Energy: –1
Collision Energy: Variable depending on analyte (Table 3)
Exit Energy: 1
Low Mass Resolution 2: 14.5
High Mass resolution 2: 14.5
Ion Energy 2: 0.8
Multiplier: 650
-3
Gas Cell Pirani Gauge: 7.0 × 10 Torr
Inter-Channel Delay: 0.1 seconds
Inter-Scan Delay: 0.1 seconds
Dwell: 0.1 seconds
Solvent Delay: 5 minutes
12. Calibration and Standardization
12.1 The mass spectrometer must be calibrated per in accordance with manufacturer specifications before analysis. In order to
obtain accurate analytical values through using this test method within the confidence limits, the following procedures must be
followed when performing thethis test method. Prepare all solutions in the lab using Class A volumetric glassware.
12.2 Calibration and Standardization—To calibrate the instrument, analyze six calibration standards and the DVL containing
(nominal concentrations in Table 4) DPGBE, EGBE and n-NP2EO. A calibration solution is prepared from standard materials or
they are purchased as certified solutions. Level 6 calibration solution containing the targets and surrogate is prepared and aliquots
of that solution are diluted to prepare Levels 1 through 5 and the DVL. The following steps will produce standards with the
concentration values shown in Table 4. The analyst is responsible for recording initial component weights correctly and calculating
and preparing appropriate dilution calculations.
12.2.1 Prepare Level 6 calibration stock standard at 1000 ppb for EGBE, 8 ppb for DPGBE and 40 ppb for n-NP2EO in 80%
water/20% 80 % water/20 % acetonitrile. The EGBE and DPGBE concentrated stock solutions were prepared in methanol at
approximately 2 g/L 2-g/L concentration and the n- NP2EO -NP2EO surrogate concentrated stock solution was prepared in
acetonitrile at approximately 0.5 g/L. The preparation of the stock standard can be accomplished using different volumes and
concentrations of stock solutions as is accustomed in the individual laboratory. Depending on the prepared stock concentrations,
the solubility at that concentration will have to be ensured.
12.2.2 Aliquots of Level 6 calibration stock standard are then diluted with 80% water/20% 80 % water/20 % acetonitrile to
prepare the desired calibration levels in 2 mL 2-mL amber glass autosampler vials. The calibration vials must be used within 24
hours to ensure optimum results. Stock calibration standards are routinely replaced every 7seven days if not previously discarded
for quality control failure. Calibration standards are not filtered.
12.2.3 Inject each standard and obtain its chromatogram. An external calibration technique is used to monitor the SRM
transitions of each analyte. Calibration software is utilized to conduct the quantitation of the target analytes and surrogates using
the SRM transition. The calibration software manual should be consulted to use the software correctly. The quantitation method
is set as an external calibration using the peak areas in ppb units. Concentrations may be calculated using the data system software
to generate linear regression or quadratic calibration curves. Forcing the calibration curve through the origin is not recommended.
12.2.4 Linear calibration may be used if the coefficient of determination, r , is >0.98 for the analyte. The point of origin is
excluded and a fit weighting of 1/X is used in order to give more emphasis to the lower concentrations. If one of the calibration
standards other than the high or low point causes the r of the curve to be <0.98, this point must be re-injected or a new calibration
curve must be regenerated. If the low and/or high point or high point, or both, is excluded, minimally a five point five-point curve
is acceptable but the reporting range must be modified to reflect this change.
TABLE 4 Concentrations of Calibration Standards (PPB)
Analyte/Surrogate DVL LV1 LV2 LV3 LV4 LV5 LV6
DPGBE 0.20 0.80 1.6 2.4 3.2 4.0 8.0
EGBE 25 100 200 300 400 500 1000
n-NP2EO 1.0 4.0 8.0 12 16 20 40
(Surrogate
n-NP2EO 1.0 4.0 8.0 12 16 20 40
(Surrogate)
D7731 − 17
12.2.5 Quadratic calibration may be used if the coefficient of determination, r , is >0.99 for the analyte. The point of origin is
excluded, and a fit weighting of 1/X is used in order to give more emphasis to the lower concentrations. If one of the calibration
standards causes the curve to be <0.99, this point must be re-injected or a new calibration curve must be regenerated. Minimally
a six point curve is acceptable using a quadratic fit. Each calibration point used to generate the curve must have a calculated percent
deviation less than 25% 25 % from the generated curve.
12.2.6 The retention time window of the SRM transitions must be within 5% 5 % of the retention time of the analyte in a
midpoint calibration standard. If this is not the case, re-analyze the calibration curve to determine if there was a shift in retention
time during the analysis and re-inject the sample. If the retention time is still incorrect in the sample, refer to the analyte as an
unknown.
12.2.7 A calibration midpoint check standard must be analyzed at the end of each batch of 20 samples or within 24 hours after
the initial calibration curve was generated. This end calibration check should be the same calibration standard that was used to
generate the initial curve. The results from the end calibration check standard must have a percent deviation less than 35% 35 %
from the calculated concentration for the target analytes and surrogates. If the results are not within these criteria, the problem must
be corrected and either all samples in the batch must be re-analyzed against a new calibration curve or the affected results must
be qualified with an indication that they do not fall within the performance criteria of thethis test method. If the analyst inspects
the vial containing the end calibration check standards and notices that the samples evaporated affecting the concentration, a new
end calibration check standard may be made and analyzed. If this new end calibration check standard has a percent deviation less
than 35% 35 % from the calculated concentration for the target analyte and surrogate, the results may be reported unqualified.
12.3 If a laboratory has not performed the test before or if there has been a major change in the measurement system, for
example, new analyst, new instrument, etc., a precision and bias study must be performed to demonstrate laboratory capability.
12.3.1 Analyze at least four replicates of a sam
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