ASTM D4128-18

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.
Designation: D4128 − 06 (Reapproved 2012) D4128 − 18
Standard Guide for
Identification and Quantitation of Organic Compounds in
Water by Combined Gas Chromatography and Electron
Impact Mass Spectrometry
This standard is issued under the fixed designation D4128; 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.
1. Scope
1.1 This guide covers the identification and quantitation of organic compounds by gas chromatography/mass spectrometry
(GC-MS) (electron impact) that are present or extracted from water and are capable of passing through a gas chromatograph
without alteration. The guide is intended primarily for solutions for which 1 ng or more of any component of interest can be
introduced onto a gas chromatographic column. This guide has the advantage of providingThis guide can be used to provide
tentative identifications of volatile and semi-volatile organics, but is restricted to (a) compounds for which reference spectra can
be obtained and (b) compounds that can be separated by gas chromatography (GC). These restrictions are imposed on the guide,
but are not a limitation of the technique. The guide is written for, but not restricted to, for analysis using automated data acquisition
and handling.
1.2 Guidelines have been included for quantitation using ASTM Test Methods D3871, D3973, and other GC-MS volatile/
semivolatile procedures used for environmental analysis . A detection amount of 1 ng can only be considered approximate. The
actual detection limits for each component must be determined in each laboratory. Actual detection amounts will vary with the
complexity of the matrix, the kind and condition of the GC-MS system, the sample preparation technique chosen, and the
application of cleanup techniques to the sample extract, if any. Lower levels of detection can be achieved using modern sensitive
instruments or with selected ion monitoring (SIM). To determine the interlaboratory detection estimate (IDE) and the
interlaboratory quantitation estimate (IQE), follow Practices D6091 and D6512.
1.3 The guide is applicable to the identification of many organic constituents of natural and treated waters. It includes all modes
of sample introduction, including injection of organic extracts, direct aqueous injection, and purge and trap techniques.
1.4 The guide is applicable to either packed or capillary column gas chromatography, including wide-bore capillary columns.
Because of their greatly enhanced resolution, capillary columns are strongly recommended.chromatography.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
1.7 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:
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
This guide 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 June 15, 2012Dec. 15, 2018. Published August 2012January 2019. Originally published in 1982. Last previous edition approved in 20062012
as D4128 – 06.D4128 – 06 (2012). DOI: 10.1520/D4128-06R12.10.1520/D4128-18.
U.S. EPA Methods 624 and 82608260C (volatiles) and U.S. EPA Methods 625 and 82708270D (semivolatiles) are suitable for quantitation.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4128 − 18
D1192 Guide for Equipment for Sampling Water and Steam in Closed Conduits (Withdrawn 2003)
D1193 Specification for Reagent Water
D2908 Practice for Measuring Volatile Organic Matter in Water by Aqueous-Injection Gas Chromatography
D3370 Practices for Sampling Water from Flowing Process Streams
D3694 Practices for Preparation of Sample Containers and for Preservation of Organic Constituents
D3871 Test Method for Purgeable Organic Compounds in Water Using Headspace Sampling
D3973 Test Method for Low-Molecular Weight Halogenated Hydrocarbons in Water
D5175 Test Method for Organohalide Pesticides and Polychlorinated Biphenyls in Water by Microextraction and Gas
Chromatography
D5316 Test Method for 1,2-Dibromoethane and 1,2-Dibromo-3-Chloropropane in Water by Microextraction and Gas
Chromatography
D5317 Test Method for Determination of Chlorinated Organic Acid Compounds in Water by Gas Chromatography with an
Electron Capture Detector
D5789 Practice for Writing Quality Control Specifications for Standard Test Methods for Organic Constituents (Withdrawn
2002)
D6091 Practice for 99 %/95 % Interlaboratory Detection Estimate (IDE) for Analytical Methods with Negligible Calibration
Error
D6512 Practice for Interlaboratory Quantitation Estimate
E260 Practice for Packed Column Gas Chromatography
E355 Practice for Gas Chromatography Terms and Relationships
2.2 U.S. Environmental Protection Agency:EPA Documents:
EPA Method 524.2–1995 Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/
Mass Spectrometry
EPA Method 624–1984 Purgeables
EPA Method 625–1984 Base/Neutrals and Acids
6,7
SW-846 Method 8270c8270D Semivolatile Organic Compounds by Gas Chromatography (GC-MS)
6,7
SW-846 Method 8260b8260C Volatile Organic Compounds by Gas Chromatography (GC-MS)
Methods for the Determination of Organic Compounds in Drinking Water-Supplement I, EPA/600/4-90/020, July 1990
Methods for the Determination of Organic Compounds in Drinking Water-Supplement II, EPA/600/R-92/129, August 1990
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms relating to water used in this standard, refer to Terminology D1129. For definitions of terms
relating to gas chromatography used in this standard, refer to Practice E355.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 characteristic ion, n—usually the primary ion in the mass spectrum used to measure response for quantitation purposes.
When there are interferences in the mass chromatogram of a primary ion, a secondary characteristic ion must be used for
quantitation.
3.2.2 volatile organicconfirmed identification, compound—n—an organic compound that can be readily separated from water by
inert gas sparging and thermally desorbed onto a GC column or is readily amenable to direct aqueous injection GC. The
compounds must elute from the column within its temperature range without alteration of the structure of the in order to confirm
a tentative identification, both the GC retention time and the mass spectrum of a compound shall uniquely match those of a
reference compound as demonstrated by co-injection of the authentic standard with the tentatively identified compound.
3.2.3 semi-volatile organicmass chromatogram, compound—n—an organic(see Discussion) compound that can be separated
from water by extraction, either liquid/liquid or solid phase, undergo volume adjustment, and be injected onto a GC. The
compounds must elute from the column within its temperature range without alteration of the structure of the compound.—a
limited mass RGC, or mass chromatogram, represents the intensities of ion currents for only those ions having particular mass to
charge ratios. It is a means of quickly scanning a complex RGC plot to locate peaks which could be specific compounds or types
of compounds. However, a complete mass spectrum is required for tentative identification.
3.2.3.1 Discussion—
The last approved version of this historical standard is referenced on www.astm.org.
Available from United States Environmental Protection Agency (EPA), William Jefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460,
http://www.epa.gov.
Available from National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161.5301 Shawnee Rd., Alexandria, VA 22312,
http://www.ntis.gov.
SW 846 can be found online at http://www.epa.gov/epaoswer/hazwaste/test/main.htm. https://www.epa.gov/hw-sw846.
D4128 − 18
There are several synonyms in current use for mass chromatogram. These include: mass fragmentogram, extracted ion current
profile, and limited mass reconstructed gas chromatogram.
3.1.3 tentative identification—all identifications are considered tentative until confirmed by co-injection of an authentic
reference compound showing identical retention time and similar mass spectra. (Tentative identification based on library matches
only are subjected to false positives.)
3.2.4 match—match, n—two criteria must be satisfied to verify a comparison of a sample component to a standard match: (1)
elution of the sample component at the same retention time as the standard component as shown by co-injection or standard
addition, and (2) correspondence of the sample component and the standard component mass spectrum. If co-elution of interfering
components prohibits accurate assignment of the sample component retention time from the total ion chromatogram, the retention
time should be assigned by using extracted ion current profiles for ions unique to the component of interest. To meet the second
criteria, all ions present in the authentic mass spectra at a relative intensity greater than 10 % (whereas the most abundant ion in
the spectrum equals 100 %) must be present in the sample spectrum; the relative intensities of these ions must agree within6
20 %within 620 % between the standard and sample spectra. (As an example, for an ion with an abundance of 50 % in the standard
spectra, the corresponding sample abundance must be between 30 % and 70 %.) However, there may be additional peaks in the
sample mass spectrum caused by co-eluting interfering components that are not present in the reference mass spectrum.
3.1.5 confirmed identification—in order to confirm a tentative identification, both the GC retention time and the mass spectrum
of a compound shall uniquely match those of a reference compound as demonstrated by co-injection of the authentic standard with
the tentatively identified compound.
3.2.5 reconstructed gas chromatogram (see(RGC), Note n—1) (RGC)—an (see Discussion)—an RGC is the computer output
representing either the summed intensities of all scanned ion intensities or a sample of the total current in the ion beam for each
spectrum scan plotted against the corresponding spectrum number. Generally, it can be correlated with a flame ionization detector
gas chromatogram.
NOTE 1—There are many synonyms in common use for RGC. These include: total ionization plot, total ionization current trace, reconstructed ion
chromatogram, total ion current profile, and total ion chromatogram.
3.2.5.1 Discussion—
There are many synonyms in common use for RGC. These include: total ionization plot, total ionization current trace,
reconstructed ion chromatogram, total ion current profile, and total ion chromatogram.
3.2.6 reference compounds—compounds, n—these are authentic materials used to obtain mass spectra, gas chromatographic
retention data, and response factors. The operator can prepare the standards or they can be prepared commercially. Quality control
solutions should be prepared independently from the calibration solutions. Quantitation methods may also require surrogate spiking
solutions to determine extraction efficiency.
3.2.7 mass chromatogram (seesemi-volatile organic compound, Note n—2)—a limited mass RGC, or mass chromatogram,
represents the intensities of ion currents for only those ions having particular mass to charge ratios. It is a means of quickly
scanning a complex RGC plot to locate peaks which could be specific compounds or types of compounds. However, a complete
mass spectrum is required for tentative identification.an organic compound that can be separated from water by extraction, either
liquid/liquid or solid phase, undergo volume adjustment, and be injected onto a GC. The compounds must elute from the column
within its temperature range without alteration of the structure of the compound.
NOTE 2—There are several synonyms in current use for mass chromatogram. These include: mass fragmentogram, extracted ion current profile, and
limited mass reconstructed gas chromatogram.
3.2.8 tentative identification, n—all identifications are considered tentative until confirmed by co-injection of an authentic
reference compound showing identical retention time and similar mass spectra. (Tentative identification based on library matches
only are subjected to false positives.)
3.2.9 characteristic ion—volatile organic compound, n—usually the primary ion in the mass spectrum used to measure response
for quantitation purposes. When there are interferences in the mass chromatogram of a primary ion, a secondary characteristic ion
must be used for quantitation. an organic compound that can be readily separated from water by inert gas sparging and thermally
desorbed onto a GC column or is readily amenable to direct aqueous injection GC. The compounds must elute from the column
within its temperature range without alteration of the structure of the compound.
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3.2 Definitions:
3.2.1 For definitions of terms relating to water used in this guide, refer to definitions in D1129. For definitions of terms relating
to gas chromatography used in this guide, refer to Practice E355.
4. Summary of Practice
4.1 The guide consists of the introduction of organic compounds from water into a GC-MS for mass spectral identification and
guidelines to determine concentration. Volatile organic compounds are typically introduced through a purge-and-trap sample
introduction device, although volatile compounds can also be introduced by direct aqueous injection. Semi-volatile compounds are
typically introduced as organic extracts from an extracted sample by syringe. A component’s spectrum is recorded as the
component elutes from the chromatographic column. The tentative identification of a sample component is based on its mass
spectrum and supported by its GC retention data. This tentative identification may be confirmed by co-injection of an authentic
standard yielding an identical retention time and a similar mass spectrum.
5. Significance and Use
5.1 With the common occurrence in water of organic compounds, some of which are toxic, it is often necessary to identify the
specific compounds present and to determine the concentration.
6. Interferences
6.1 Sample alteration and losses of the component of interest are not true interferences, but are a source of trouble in performing
a qualitative GC-MS analysis. Examples of component loss are: decomposition, polymerization, adsorption, and both volatilization
prior to introduction into the GC and non-volatilization after introduction into the GC. In addition, GC-MS interface plugging can
lead to apparent losses.
6.2 Chromatographically unresolved compounds or instrumental background which co-elutes with the compounds of interest
can interfere with this guide. These interferences can change the apparent mass spectrum of the compound of interest, thereby
making tentative identification difficult.
6.3 Other interferences, such as background GC peaks due to contaminated sample preparation reagent blanks, GC columns,
instrumentation or column bleed, are common problems that the analyst must strive to understand and eliminate.
6.4 Isomeric compounds may be difficult to separate by GC and the mass spectra of isomers are frequently identical within
experimental error. This could lead to either ambiguity in identification or to actual incorrect identification in some cases. The
analyst must be aware of this potential problem.
6.5 When attempting to identify compounds in water samples containing large numbers of compounds, particularly complex
mixtures such as petroleum products, great care must be exercised to determine that candidate unknown mass spectra are free of
interfering peaks as possible. Judicious background-subtraction can assist in this endeavor. Additional information can be gathered
by examining the extracted ion current profiles of the major mass spectral peaks in the candidate spectrum. Frequently, the
occurrence of contaminated spectra can be determined by noting differences in the profiles of several mass chromatograms that
do not exactly fit the profiles of the peaks of the compound of interest. These may be co-eluting interferences. However, it is rarely
possible to completely eliminate all interferences from complex samples, and the analyst must be aware of this in interpreting
unknowns against reference spectra.
7. Apparatus
7.1 GC-MS/DS—A gas chromatograph interfaced to a mass spectrometer having electron impact ionization capability is used.
Most modern GC-MS systems are typically controlled by a data system for computerized instrument control of data acquisition
and data reduction. Capillary columns are preferred with most GC-MS systems although packed GC columns may be used.
7.2 Apparatus required to extract organic compounds from water and concentrate them in a small volume of organic
solvent—Required to Extract Organic Compounds from Water and Concentrate Them in a Small Volume of Organic Solvent—This
apparatus includes a 2-L separatory funnel for batch extractions or 1-L continuous liquid-liquid extractor and facilities for
Kuderna-Danish concentration. Liquid-liquid extraction for volatile organic constituents can be conducted using the apparatus
specified in Test Method D3973.
7.3 Apparatus for purge-and-trapPurge-and-Trap GC-MS sample introduction—Sample Introduction—See Test Method D3871
or EPA Method 524.2.Methods 524.2 or 8260C.
7.4 Microsyringe, 10-μL.
Consult operation manuals from manufacturers of GC-MS or GC-MS/DS systems.
D4128 − 18
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. 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. For trace
analysis using organic solvents for liquid-liquid extraction or elution from solid sorbents, solvents specified as distilled-in-glass,
nano-grade, or pesticide-grade frequently have lower levels of interfering impurities. In all cases, sufficient reagent blanks must
be processed with the samples to ensure that all compounds of interest are not present in blanks due to reagents or glassware. Other
grades of reagents may be used, providing it is first ascertained that the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water that meets the
purity specifications of Type I or Type II water presented in Specification D1193. This water must be shown not to contain
contaminants at concentrations sufficient to interfere with the analysis.
8.3 Reference compounds shall be of known purity; impurity peaks shall not interfere with the compound of interest.
8.4 Reference spectra for tentative identifications may be obtained from commercially available mass spectral libraries such as
the electronic EPA/NIST/NIH Mass Spectral Library or from various publications. Many GC-MS/DS contain libraries of
reference spectra as well as software required to match unknown spectra to these libraries. User libraries of compounds of interest
may be generated from reference compounds run on the same instrument used for unknown analysis and under the same
conditions. User libraries allow faster and more accurate tentative identifications than large generalized libraries. Reference spectra
for confirmed identifications are determined under the same conditions for sample analysis by co-injecting the reference
compounds with the sample extract, or adding the reference compounds to aqueous samples, and confirming both the co-elution
of the unknown and reference compounds and their matched mass spectra.
8.5 Gas Chromatography Column—All-inclusive guidelines for GC column selection do not exist. Each analysis requires
careful consideration of the column used (see Note 31). Bonded phase fused silica capillary columns have proven remarkably
popular and successful. are commonly used. For examples, consult other ASTM test methods, such as Test Methods D5175,
D5316, D5317, or US EPA methods. Liquid phases for GC columns used in direct aqueous injection analysis shall conform to
Practice D2908.
NOTE 1—General guidelines for column selection can be found in GC or column suppliers’ literature and textbooks.
8.6 The following chemicals may be used in this guide.
8.6.1 Methyl Stearate.
8.6.2 Malathion.
8.6.3 bis-(pentafluorophenyl)Phenyl Phosphine.
8.6.4 decafluorotriphenyl phosphine (DFTPP).
8.6.5 bromofluorobenzene (BFB).
8.6.6 Isopropyl Alcohol.
8.6.7 Methylene Chloride.
8.6.8 Methyl Hexanoate.
8.6.9 N-Methyl-2-Pyrrolidone.
9. Hazards
9.1 Warning—Due care shall be exercised in handling samples to minimize operator exposure to all chemicals including
solvents, standards, and reagents. Solvents are a particular source of hazard because of the large quantities used in many sample
preparation procedures. General practice regarding the proper use of a gas chromatograph/mass spectrometer system can be found
in the manufacturer’s operation manual. Since potentially toxic materials may be handled, all effluent and vent gases from any
source should be vented in an environmentally safe manner. Possible sources to be considered include split gas from GC exhaust,
gas from vacuum pumps, and waste containers.Warning: Due care shall be exercised in handling samples to minimize operator
exposure to all chemicals including solvents, standards, and reagents. Solvents are a particular source of hazard because of the large
quantities used in many sample preparation procedures. General practice regarding the proper use of a gas chromatograph/mass
spectrometer system can be found in the manufacturer’s operation manual. Since potentially toxic materials may be handled, all
effluent and vent gases from any source should be vented in an environmentally safe manner. Possible sources to be considered
include s
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