ASTM D2908-91(2017)
(Practice)Standard Practice for Measuring Volatile Organic Matter in Water by Aqueous-Injection Gas Chromatography
Standard Practice for Measuring Volatile Organic Matter in Water by Aqueous-Injection Gas Chromatography
SIGNIFICANCE AND USE
5.1 This practice is useful in identifying the major organic constituents in wastewater for support of effective in-plant or pollution control programs. Currently, the most practical means for tentatively identifying and measuring a range of volatile organic compounds is gas-liquid chromatography. Positive identification requires supplemental testing (for example, multiple columns, speciality detectors, spectroscopy, or a combination of these techniques).
SCOPE
1.1 This practice covers general guidance applicable to certain test methods for the qualitative and quantitative determination of specific organic compounds, or classes of compounds, in water by direct aqueous injection gas chromatography (1, 2, 3, 4).2
1.2 Volatile organic compounds at aqueous concentrations greater than about 1 mg/L can generally be determined by direct aqueous injection gas chromatography.
1.3 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.
1.4 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
Relations
Buy Standard
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: D2908 − 91 (Reapproved 2017)
Standard Practice for
Measuring Volatile Organic Matter in Water by Aqueous-
Injection Gas Chromatography
This standard is issued under the fixed designation D2908; 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 E355PracticeforGasChromatographyTermsandRelation-
ships
1.1 This practice covers general guidance applicable to
certain test methods for the qualitative and quantitative deter-
3. Terminology
mination of specific organic compounds, or classes of
compounds, in water by direct aqueous injection gas chroma-
3.1 Definitions—The following terms in this standard are
tography (1, 2, 3, 4).
defined in accordance with Terminology D1129. For defini-
tions of other chromatographic terms used in this standard,
1.2 Volatile organic compounds at aqueous concentrations
refer to Practice E355.
greater than about 1 mg/L can generally be determined by
direct aqueous injection gas chromatography. 3.1.1 “ghosting” or memory peaks, n—an interference,
showing as a peak, which appears at the same elution time as
1.3 This standard does not purport to address all of the
the organic component of previous analysis.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.1.2 internal standard, n—amaterialpresentinoraddedto
priate safety, health, and environmental practices and deter-
samplesinknownamounttoserveasareferencemeasurement.
mine the applicability of regulatory limitations prior to use.
3.1.3 noise,n—anextraneouselectronicsignalwhichaffects
1.4 This international standard was developed in accor-
baseline stability.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3.1.4 relative retention ratio, n—the retention time of the
Development of International Standards, Guides and Recom-
unknown component divided by the retention time of the
mendations issued by the World Trade Organization Technical
internal standard.
Barriers to Trade (TBT) Committee.
3.1.5 retention time, n—the time that elapses from the
introduction of the sample until the peak maximum is reached.
2. Referenced Documents
2.1 ASTM Standards:
4. Summary of Practice
D1129Terminology Relating to Water
D1192Guide for Equipment for Sampling Water and Steam
4.1 This practice defines the applicability of various col-
in Closed Conduits (Withdrawn 2003)
umns and conditions for the separation of naturally occurring
D1193Specification for Reagent Water
or synthetic organics or both, in an aqueous medium for
D3370Practices for Sampling Water from Closed Conduits
subsequent detection with a flame ionization detector. After
E260Practice for Packed Column Gas Chromatography
vaporization,theaqueoussampleiscarriedthroughthecolumn
by an inert carrier gas.The sample components are partitioned
betweenthecarriergasandastationaryliquidphaseonaninert
This practice is under the jurisdiction ofASTM Committee D19 on Water and
solidsupport.Thecolumneffluentisburnedinanair-hydrogen
is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
Organic Substances in Water.
flame. The ions released from combustion of the organic
Current edition approved Dec. 15, 2017. Published December 2017. Originally
components induce an increase in standing current which is
approved in 1970. Last previous edition approved in 2011 as D2908–91 (2011).
measured.Although this method is written for hydrogen flame
DOI: 10.1520/D2908-91R17.
detection, the basic technology is applicable to other detectors
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard.
if water does not interfere.
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
4.2 The elution times are characteristic of the various
Standards volume information, refer to the standard’s Document Summary page on
organiccomponentspresentinthesample,whilethepeakareas
the ASTM website.
are proportional to the quantities of the components.Adiscus-
The last approved version of this historical standard is referenced on
www.astm.org. sion of gas chromatography is presented in Practice E260.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2908 − 91 (2017)
5. Significance and Use increases due to the increasing temperature.An unsteady flow
will create an unstable baseline.
5.1 This practice is useful in identifying the major organic
7.1.2 Gas Transport Tubing—Newtubingshouldbewashed
constituents in wastewater for support of effective in-plant or
with a detergent solution, rinsed with Type I cold water, and
pollutioncontrolprograms.Currently,themostpracticalmeans
solvent rinsed to remove residual organic preservatives or
for tentatively identifying and measuring a range of volatile
lubricants. Ethanol is an effective solvent. The tubing is then
organic compounds is gas-liquid chromatography. Positive
dried by flushing with nitrogen. Drying can be accelerated by
identification requires supplemental testing (for example, mul-
installing the tubing in a gas chromatograph (GC) oven and
tiple columns, speciality detectors, spectroscopy, or a combi-
flowingnitrogenorotherinertgasthroughit,whileheatingthe
nation of these techniques).
oven to 50°C.
7.1.3 Gas Leaks—The gas system should be pressure
6. Interferences
checkeddailyforleaks.Tocheckforleaks,shutoffthedetector
6.1 Particulate Matter—Particulate or suspended matter
and pressurize the gas system to approximately 103 kPa (15
should be removed by centrifugation or membrane filtration if
psi) above the normal operating pressure. Then shut off the
components of interest are not altered. This pretreatment will
tank valve and observe the level of the pressure gauge. If the
prevent both plugging of syringes and formation of condensa-
preset pressure holds for 10 min, the system can be considered
tion nuclei.Acidification will often facilitate the dissolving of
leak-free. If the pressure drops, a leak is indicated and should
particulate matter, but the operator must determine that pH
be located and eliminated before proceeding further. A soap
adjustment does not alter the components to be determined.
solution may be used for determining the source of leaks, but
care must be exercised to avoid getting the solution inside the
6.2 Identical Retention Times—With any given column and
tubing or instrument since it will cause a long lasting, serious
operating conditions, one or more components may elute at
source of interference. Leaks may also occur between the
identical retention times. Thus a chromatographic peak is only
instrument gas inlet valve and flame tip. This may be checked
presumptive evidence of a single component. Confirmation
byremovingtheflametip,replacingitwithaclosedfittingand
requiresanalyseswithothercolumnswithvaryingphysicaland
rechecking for pressure stability as previously noted.
chemical properties, or spectrometric confirmation of the
7.1.4 Gas Flow—The gas flow can be determined with a
isolated peak, or both.
bubble flow meter. A micro-rotameter in the gas inlet line is
6.3 Acidification—Detection of certain groups of compo-
also helpful. It should be recalibrated after each readjustment
nentswillbeenhancedifthesampleismadeneutralorslightly
of the gas operating pressure.
acidic.Thismayminimizetheformationofnonvolatilesaltsin
cases such as the analysis of volatile organic acids and bases 7.2 Injection Port—The injection port usually is insulated
and certain chlorophenols. from the chromatographic oven and equipped with a separate
heater that will maintain a constant temperature. The tempera-
6.4 Ghosting—Ghosting is evidenced by an interference
ture of the injection port should be adjusted to approximately
peakthatoccursatthesametimeasthatforacomponentfrom
50°C above the highest boiling sample component. This will
a previous analysis but usually with less intensity. Ghosting
help minimize the elution time, as well as reduce peak tailing.
occurs because of organic holdup in the injection port. Re-
Should thermal decomposition of components be a problem,
peated Type I water washing with 5-µL injections between
theinjectionporttemperatureshouldbereducedappropriately.
sample runs will usually eliminate ghosting problems. The
Cleanliness of the injection port in some cases can be main-
baseline is checked at maximum sensitivity to assure that the
tained at a tolerable level by periodically raising the tempera-
interference has been eliminated. In addition to water
ture 25°C above the normal operating level. Use of disposable
injections, increasing the injection port temperature for a
glass inserts or periodic cleaning with chromic acid can be
period of time will often facilitate the elimination of ghosting
practiced with some designs. When using samples larger than
problems.
5µL,blowbackintothecarriergassupplyshouldbeprevented
6.4.1 Delayed Elution—Highly polar or high boiling com-
through use of a preheated capillary or other special design.
ponents may unpredictably elute several chromatograms later
When using 3.175-mm (0.125-in.) columns, samples larger
and therefore act as an interference. This is particularly true
than 5 µL may extinguish the flame depending on column
with complex industrial waste samples. A combination of
length, carrier gas flow, and injection temperature.
repeatedwaterinjectionsandelevatedcolumntemperaturewill
7.2.1 Septum—Organics eluting from the septum in the
eliminatethisproblem.Backflushvalvesshouldbeusedifthis
injection port have been found to be a source of an unsteady
problem is encountered often.
baseline when operating at high sensitivity. Septa should be
preconditioned. Insertion of a new septum in the injection port
7. Apparatus
at the end of the day for heating overnight will usually
7.1 Gas System:
eliminate these residuals. A separate oven operating at a
7.1.1 Gas Regulators—High-quality pressure regulators temperaturesimilartothatoftheinjectionportcanalsobeused
shouldbeusedtoensureasteadyflowofgastotheinstrument. to process the septa.The septa should be changed at least once
If temperature programming is used, differential flow control- a day to minimize gas leaks and sample blowback. Septa with
lers should be installed in the carrier gas line to prevent a TFE-fluorocarbonbackingsminimizeorganicbleedingandcan
decrease in flow as the pressure drop across the column be used safely for longer periods.
D2908 − 91 (2017)
7.2.2 On-Column Injection—Whileinjectionintotheheated former may be required in addition to the one incorporated
chamber for flash vaporization is the most common injection within the chromatographic instrument.
set-up, some analyses (for example, organic acids) are better
8. Reagents and Materials
performed with on-column injection to reduce ghosting and
peaktailingandtopreventdecompositionofthermallydegrad-
8.1 Purity of Reagents—Reagent grade chemicals shall be
able compounds. This capability should be built into the
used in all instances for gas purification, sample stabilization,
injection system. When using on-column injection a shorter
and other applications. Unless otherwise indicated, it is in-
columnlifemayoccurduetosolidbuildupintheinjectionend
tended that all reagents shall conform to the specifications of
of the column.
theCommitteeonAnalyticalReagentsoftheAmericanChemi-
cal Society, where such specifications are available. Other
7.3 Column Oven—The column ovens usually are insulated
grades may be used, provided it is first ascertained that the
separately from the injection port and the detector. The oven
reagent is of sufficiently high purity to permit its use without
should be equipped with a proportional heater and a squirrel-
lessening the accuracy of the determination.
cage blower to assure maximum temperature reproducibility
8.1.1 All chemicals used for internal standards shall be of
and uniformity throughout the oven. Reproducibility of oven
highest known purity.
temperature should be within 0.5°C.
7.3.1 Temperature Programming—Temperature program- 8.2 Purity of Water—Unless otherwise indicated, references
ming is desirable when the analysis involves the resolution of towatershallbeunderstoodtomeanreagentwaterconforming
organics with widely varying boiling points. The column oven to Type I of Specification D1193.
should be equipped with temperature programming be-
8.3 Carrier Gas System—Only gases of the highest purity
tween−15and350°C(orrangeofthemethod)withselectabil-
obtainable should be used in a chromatographic system desig-
ity of several programming rates between 1 and 20°/min
nated for trace-organic monitoring in water. The common
provided. The actual column temperature will lag somewhat
carrier gases used with a flame ionization detector (FID) are
behind the oven temperature at the faster programming rates.
helium and nitrogen. Trace contaminants in even the highest
Baseline drift will often occur because of increased higher
purity gases can often affect baseline stability and introduce
temperatures experienced during temperature programming.
noise. Absorption columns of molecular sieves (14 by 30-
This depends on the stability of the substrate and operating
mesh) and anhydrous calcium sulfate (CaSO , 8 mesh) in
temperature range. Temperatures that approach the maximum
series between the gas supply tank and the instrument will
limit of the liquid phase limit the operating range. Utilization
minimize the effect of trace impurities. These preconditioning
of dual matching columns and a differential electrometer can
columns,toremaineffective,mustbecleanedbybackflushing
minimize the effect of drift; however, the drift is reproducible
them with a clean gas (nitrogen, helium) at approximately
and does not interfere with the analysis in most cases.
200°C, or they must be replaced at regular intervals. Use of
catalytic purifiers is also effective (4).
7.4 Detector—The combination of high sensitivity and a
widelinearrangemakestheflameionizationdetector(FID)the
8.4 Column:
usual choice in trace aqueous analysis. The flame ionization
8.4.1 Column Tubing—For most organic analyses in aque-
detectorisrelativelyinsensitivetowatervaporandtomoderate
oussystems,stainlesssteelisthemostdesirablec
...
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D2908 − 91 (Reapproved 2017)
Standard Practice for
Measuring Volatile Organic Matter in Water by Aqueous-
Injection Gas Chromatography
This standard is issued under the fixed designation D2908; 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 E355 Practice for Gas Chromatography Terms and Relation-
ships
1.1 This practice covers general guidance applicable to
certain test methods for the qualitative and quantitative deter-
3. Terminology
mination of specific organic compounds, or classes of
compounds, in water by direct aqueous injection gas chroma-
3.1 Definitions—The following terms in this standard are
tography (1, 2, 3, 4).
defined in accordance with Terminology D1129. For defini-
tions of other chromatographic terms used in this standard,
1.2 Volatile organic compounds at aqueous concentrations
refer to Practice E355.
greater than about 1 mg/L can generally be determined by
direct aqueous injection gas chromatography. 3.1.1 “ghosting” or memory peaks, n—an interference,
showing as a peak, which appears at the same elution time as
1.3 This standard does not purport to address all of the
the organic component of previous analysis.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.1.2 internal standard, n—a material present in or added to
priate safety, health, and environmental practices and deter-
samples in known amount to serve as a reference measurement.
mine the applicability of regulatory limitations prior to use.
3.1.3 noise, n—an extraneous electronic signal which affects
1.4 This international standard was developed in accor-
baseline stability.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3.1.4 relative retention ratio, n—the retention time of the
Development of International Standards, Guides and Recom-
unknown component divided by the retention time of the
mendations issued by the World Trade Organization Technical
internal standard.
Barriers to Trade (TBT) Committee.
3.1.5 retention time, n—the time that elapses from the
introduction of the sample until the peak maximum is reached.
2. Referenced Documents
2.1 ASTM Standards:
4. Summary of Practice
D1129 Terminology Relating to Water
D1192 Guide for Equipment for Sampling Water and Steam
4.1 This practice defines the applicability of various col-
in Closed Conduits (Withdrawn 2003)
umns and conditions for the separation of naturally occurring
D1193 Specification for Reagent Water
or synthetic organics or both, in an aqueous medium for
D3370 Practices for Sampling Water from Closed Conduits
subsequent detection with a flame ionization detector. After
E260 Practice for Packed Column Gas Chromatography
vaporization, the aqueous sample is carried through the column
by an inert carrier gas. The sample components are partitioned
between the carrier gas and a stationary liquid phase on an inert
This practice is under the jurisdiction of ASTM Committee D19 on Water and
solid support. The column effluent is burned in an air-hydrogen
is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
Organic Substances in Water. flame. The ions released from combustion of the organic
Current edition approved Dec. 15, 2017. Published December 2017. Originally
components induce an increase in standing current which is
approved in 1970. Last previous edition approved in 2011 as D2908 – 91 (2011).
measured. Although this method is written for hydrogen flame
DOI: 10.1520/D2908-91R17.
detection, the basic technology is applicable to other detectors
The boldface numbers in parentheses refer to the list of references at the end of
this standard.
if water does not interfere.
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
4.2 The elution times are characteristic of the various
Standards volume information, refer to the standard’s Document Summary page on
organic components present in the sample, while the peak areas
the ASTM website.
4 are proportional to the quantities of the components. A discus-
The last approved version of this historical standard is referenced on
www.astm.org. sion of gas chromatography is presented in Practice E260.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2908 − 91 (2017)
5. Significance and Use increases due to the increasing temperature. An unsteady flow
will create an unstable baseline.
5.1 This practice is useful in identifying the major organic
7.1.2 Gas Transport Tubing—New tubing should be washed
constituents in wastewater for support of effective in-plant or
with a detergent solution, rinsed with Type I cold water, and
pollution control programs. Currently, the most practical means
solvent rinsed to remove residual organic preservatives or
for tentatively identifying and measuring a range of volatile
lubricants. Ethanol is an effective solvent. The tubing is then
organic compounds is gas-liquid chromatography. Positive
dried by flushing with nitrogen. Drying can be accelerated by
identification requires supplemental testing (for example, mul-
installing the tubing in a gas chromatograph (GC) oven and
tiple columns, speciality detectors, spectroscopy, or a combi-
flowing nitrogen or other inert gas through it, while heating the
nation of these techniques).
oven to 50°C.
7.1.3 Gas Leaks—The gas system should be pressure
6. Interferences
checked daily for leaks. To check for leaks, shut off the detector
6.1 Particulate Matter—Particulate or suspended matter
and pressurize the gas system to approximately 103 kPa (15
should be removed by centrifugation or membrane filtration if
psi) above the normal operating pressure. Then shut off the
components of interest are not altered. This pretreatment will
tank valve and observe the level of the pressure gauge. If the
prevent both plugging of syringes and formation of condensa-
preset pressure holds for 10 min, the system can be considered
tion nuclei. Acidification will often facilitate the dissolving of
leak-free. If the pressure drops, a leak is indicated and should
particulate matter, but the operator must determine that pH
be located and eliminated before proceeding further. A soap
adjustment does not alter the components to be determined.
solution may be used for determining the source of leaks, but
care must be exercised to avoid getting the solution inside the
6.2 Identical Retention Times—With any given column and
tubing or instrument since it will cause a long lasting, serious
operating conditions, one or more components may elute at
source of interference. Leaks may also occur between the
identical retention times. Thus a chromatographic peak is only
instrument gas inlet valve and flame tip. This may be checked
presumptive evidence of a single component. Confirmation
by removing the flame tip, replacing it with a closed fitting and
requires analyses with other columns with varying physical and
rechecking for pressure stability as previously noted.
chemical properties, or spectrometric confirmation of the
isolated peak, or both. 7.1.4 Gas Flow—The gas flow can be determined with a
bubble flow meter. A micro-rotameter in the gas inlet line is
6.3 Acidification—Detection of certain groups of compo-
also helpful. It should be recalibrated after each readjustment
nents will be enhanced if the sample is made neutral or slightly
of the gas operating pressure.
acidic. This may minimize the formation of nonvolatile salts in
cases such as the analysis of volatile organic acids and bases 7.2 Injection Port—The injection port usually is insulated
and certain chlorophenols. from the chromatographic oven and equipped with a separate
heater that will maintain a constant temperature. The tempera-
6.4 Ghosting—Ghosting is evidenced by an interference
ture of the injection port should be adjusted to approximately
peak that occurs at the same time as that for a component from
50°C above the highest boiling sample component. This will
a previous analysis but usually with less intensity. Ghosting
help minimize the elution time, as well as reduce peak tailing.
occurs because of organic holdup in the injection port. Re-
Should thermal decomposition of components be a problem,
peated Type I water washing with 5-µL injections between
the injection port temperature should be reduced appropriately.
sample runs will usually eliminate ghosting problems. The
Cleanliness of the injection port in some cases can be main-
baseline is checked at maximum sensitivity to assure that the
tained at a tolerable level by periodically raising the tempera-
interference has been eliminated. In addition to water
ture 25°C above the normal operating level. Use of disposable
injections, increasing the injection port temperature for a
glass inserts or periodic cleaning with chromic acid can be
period of time will often facilitate the elimination of ghosting
practiced with some designs. When using samples larger than
problems.
5 µL, blowback into the carrier gas supply should be prevented
6.4.1 Delayed Elution—Highly polar or high boiling com-
through use of a preheated capillary or other special design.
ponents may unpredictably elute several chromatograms later
When using 3.175-mm (0.125-in.) columns, samples larger
and therefore act as an interference. This is particularly true
than 5 µL may extinguish the flame depending on column
with complex industrial waste samples. A combination of
length, carrier gas flow, and injection temperature.
repeated water injections and elevated column temperature will
7.2.1 Septum—Organics eluting from the septum in the
eliminate this problem. Back flush valves should be used if this
injection port have been found to be a source of an unsteady
problem is encountered often.
baseline when operating at high sensitivity. Septa should be
preconditioned. Insertion of a new septum in the injection port
7. Apparatus
at the end of the day for heating overnight will usually
7.1 Gas System:
eliminate these residuals. A separate oven operating at a
7.1.1 Gas Regulators—High-quality pressure regulators temperature similar to that of the injection port can also be used
should be used to ensure a steady flow of gas to the instrument. to process the septa. The septa should be changed at least once
If temperature programming is used, differential flow control- a day to minimize gas leaks and sample blowback. Septa with
lers should be installed in the carrier gas line to prevent a TFE-fluorocarbon backings minimize organic bleeding and can
decrease in flow as the pressure drop across the column be used safely for longer periods.
D2908 − 91 (2017)
7.2.2 On-Column Injection—While injection into the heated former may be required in addition to the one incorporated
chamber for flash vaporization is the most common injection within the chromatographic instrument.
set-up, some analyses (for example, organic acids) are better
8. Reagents and Materials
performed with on-column injection to reduce ghosting and
peak tailing and to prevent decomposition of thermally degrad-
8.1 Purity of Reagents—Reagent grade chemicals shall be
able compounds. This capability should be built into the
used in all instances for gas purification, sample stabilization,
injection system. When using on-column injection a shorter
and other applications. Unless otherwise indicated, it is in-
column life may occur due to solid build up in the injection end
tended that all reagents shall conform to the specifications of
of the column.
the Committee on Analytical Reagents of the American Chemi-
cal Society, where such specifications are available. Other
7.3 Column Oven—The column ovens usually are insulated
grades may be used, provided it is first ascertained that the
separately from the injection port and the detector. The oven
reagent is of sufficiently high purity to permit its use without
should be equipped with a proportional heater and a squirrel-
lessening the accuracy of the determination.
cage blower to assure maximum temperature reproducibility
8.1.1 All chemicals used for internal standards shall be of
and uniformity throughout the oven. Reproducibility of oven
highest known purity.
temperature should be within 0.5°C.
7.3.1 Temperature Programming—Temperature program- 8.2 Purity of Water—Unless otherwise indicated, references
ming is desirable when the analysis involves the resolution of to water shall be understood to mean reagent water conforming
organics with widely varying boiling points. The column oven to Type I of Specification D1193.
should be equipped with temperature programming be-
8.3 Carrier Gas System—Only gases of the highest purity
tween −15 and 350°C (or range of the method) with selectabil-
obtainable should be used in a chromatographic system desig-
ity of several programming rates between 1 and 20°/min
nated for trace-organic monitoring in water. The common
provided. The actual column temperature will lag somewhat
carrier gases used with a flame ionization detector (FID) are
behind the oven temperature at the faster programming rates.
helium and nitrogen. Trace contaminants in even the highest
Baseline drift will often occur because of increased higher
purity gases can often affect baseline stability and introduce
temperatures experienced during temperature programming.
noise. Absorption columns of molecular sieves (14 by 30-
This depends on the stability of the substrate and operating
mesh) and anhydrous calcium sulfate (CaSO , 8 mesh) in
temperature range. Temperatures that approach the maximum
series between the gas supply tank and the instrument will
limit of the liquid phase limit the operating range. Utilization
minimize the effect of trace impurities. These preconditioning
of dual matching columns and a differential electrometer can
columns, to remain effective, must be cleaned by back flushing
minimize the effect of drift; however, the drift is reproducible
them with a clean gas (nitrogen, helium) at approximately
and does not interfere with the analysis in most cases.
200°C, or they must be replaced at regular intervals. Use of
catalytic purifiers is also effective (4).
7.4 Detector—The combination of high sensitivity and a
wide linear range makes the flame ionization detector (FID) the
8.4 Column:
usual choice in tra
...
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: D2908 − 91 (Reapproved 2011) D2908 − 91 (Reapproved 2017)
Standard Practice for
Measuring Volatile Organic Matter in Water by Aqueous-
Injection Gas Chromatography
This standard is issued under the fixed designation D2908; 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 practice covers general guidance applicable to certain test methods for the qualitative and quantitative determination
of specific organic compounds, or classes of compounds, in water by direct aqueous injection gas chromatography (1, 2, 3, 4).
1.2 Volatile organic compounds at aqueous concentrations greater than about 1 mg/L can generally be determined by direct
aqueous injection gas chromatography.
1.3 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.
1.4 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
D1192 Guide for Equipment for Sampling Water and Steam in Closed Conduits (Withdrawn 2003)
D1193 Specification for Reagent Water
D3370 Practices for Sampling Water from Closed Conduits
E260 Practice for Packed Column Gas Chromatography
E355 Practice for Gas Chromatography Terms and Relationships
3. Terminology
3.1 Definitions:Definitions
3.1.1 The following terms in this practice are defined in accordance with Terminology D1129.—The following terms in this
standard are defined in accordance with Terminology D1129. For definitions of other chromatographic terms used in this standard,
refer to Practice E355.
3.1.1 “ghosting” or memory peaks—peaks, n—an interference, showing as a peak, which appears at the same elution time as
the organic component of previous analysis.
3.1.2 internal standard—standard, n—a material present in or added to samples in known amount to serve as a reference
measurement.
3.1.3 noise—noise, n—an extraneous electronic signal which affects baseline stability.
3.1.4 relative retention ratio—ratio, n—the retention time of the unknown component divided by the retention time of the
internal standard.
3.1.5 retention time—time, n—the time that elapses from the introduction of the sample until the peak maximum is reached.
This practice 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 2011December 2017. Originally approved in 1970. Last previous edition approved in 20052011 as
D2908 – 91 (2011). (2005). DOI: 10.1520/D2908-91R11.10.1520/D2908-91R17.
The boldface numbers in parentheses refer to the list of references at the end of this practice.standard.
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.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2908 − 91 (2017)
3.2 For definitions of other chromatographic terms used in this practice, refer to Practice E355.
4. Summary of Practice
4.1 This practice defines the applicability of various columns and conditions for the separation of naturally occurring or
synthetic organics or both, in an aqueous medium for subsequent detection with a flame ionization detector. After vaporization,
the aqueous sample is carried through the column by an inert carrier gas. The sample components are partitioned between the
carrier gas and a stationary liquid phase on an inert solid support. The column effluent is burned in an air-hydrogen flame. The ions
released from combustion of the organic components induce an increase in standing current which is measured. Although this
method is written for hydrogen flame detection, the basic technology is applicable to other detectors if water does not interfere.
4.2 The elution times are characteristic of the various organic components present in the sample, while the peak areas are
proportional to the quantities of the components. A discussion of gas chromatography is presented in Practice E260.
5. Significance and Use
5.1 This practice is useful in identifying the major organic constituents in wastewater for support of effective in-plant or
pollution control programs. Currently, the most practical means for tentatively identifying and measuring a range of volatile
organic compounds is gas-liquid chromatography. Positive identification requires supplemental testing (for example, multiple
columns, speciality detectors, spectroscopy, or a combination of these techniques).
6. Interferences
6.1 Particulate Matter—Particulate or suspended matter should be removed by centrifugation or membrane filtration if
components of interest are not altered. This pretreatment will prevent both plugging of syringes and formation of condensation
nuclei. Acidification will often facilitate the dissolving of particulate matter, but the operator must determine that pH adjustment
does not alter the components to be determined.
6.2 Identical Retention Times—With any given column and operating conditions, one or more components may elute at identical
retention times. Thus a chromatographic peak is only presumptive evidence of a single component. Confirmation requires analyses
with other columns with varying physical and chemical properties, or spectrometric confirmation of the isolated peak, or both.
6.3 Acidification—Detection of certain groups of components will be enhanced if the sample is made neutral or slightly acidic.
This may minimize the formation of nonvolatile salts in cases such as the analysis of volatile organic acids and bases and certain
chlorophenols.
6.4 Ghosting—Ghosting is evidenced by an interference peak that occurs at the same time as that for a component from a
previous analysis but usually with less intensity. Ghosting occurs because of organic holdup in the injection port. Repeated Type
I water washing with 5-μL injections between sample runs will usually eliminate ghosting problems. The baseline is checked at
maximum sensitivity to assure that the interference has been eliminated. In addition to water injections, increasing the injection
port temperature for a period of time will often facilitate the elimination of ghosting problems.
6.4.1 Delayed Elution—Highly polar or high boiling components may unpredictably elute several chromatograms later and
therefore act as an interference. This is particularly true with complex industrial waste samples. A combination of repeated water
injections and elevated column temperature will eliminate this problem. Back flush valves should be used if this problem is
encountered often.
7. Apparatus
7.1 Gas System:
7.1.1 Gas Regulators—High-quality pressure regulators should be used to ensure a steady flow of gas to the instrument. If
temperature programming is used, differential flow controllers should be installed in the carrier gas line to prevent a decrease in
flow as the pressure drop across the column increases due to the increasing temperature. An unsteady flow will create an unstable
baseline.
7.1.2 Gas Transport Tubing—New tubing should be washed with a detergent solution, rinsed with Type I cold water, and solvent
rinsed to remove residual organic preservatives or lubricants. Ethanol is an effective solvent. The tubing is then dried by flushing
with nitrogen. Drying can be accelerated by installing the tubing in a gas chromatograph (GC) oven and flowing nitrogen or other
inert gas through it, while heating the oven to 50°C.
7.1.3 Gas Leaks—The gas system should be pressure checked daily for leaks. To check for leaks, shut off the detector and
pressurize the gas system to approximately 103 kPa (15 psi) above the normal operating pressure. Then shut off the tank valve and
observe the level of the pressure gauge. If the preset pressure holds for 10 min, the system can be considered leak-free. If the
pressure drops, a leak is indicated and should be located and eliminated before proceeding further. A soap solution may be used
for determining the source of leaks, but care must be exercised to avoid getting the solution inside the tubing or instrument since
it will cause a long lasting, serious source of interference. Leaks may also occur between the instrument gas inlet valve and flame
tip. This may be checked by removing the flame tip, replacing it with a closed fitting and rechecking for pressure stability as
previously noted.
D2908 − 91 (2017)
7.1.4 Gas Flow—The gas flow can be determined with a bubble flow meter. A micro-rotameter in the gas inlet line is also
helpful. It should be recalibrated after each readjustment of the gas operating pressure.
7.2 Injection Port—The injection port usually is insulated from the chromatographic oven and equipped with a separate heater
that will maintain a constant temperature. The temperature of the injection port should be adjusted to approximately 50°C above
the highest boiling sample component. This will help minimize the elution time, as well as reduce peak tailing. Should thermal
decomposition of components be a problem, the injection port temperature should be reduced appropriately. Cleanliness of the
injection port in some cases can be maintained at a tolerable level by periodically raising the temperature 25°C above the normal
operating level. Use of disposable glass inserts or periodic cleaning with chromic acid can be practiced with some designs. When
using samples larger than 5 μL, blowback into the carrier gas supply should be prevented through use of a preheated capillary or
other special design. When using 3.175-mm (0.125-in.) columns, samples larger than 5 μL may extinguish the flame depending
on column length, carrier gas flow, and injection temperature.
7.2.1 Septum—Organics eluting from the septum in the injection port have been found to be a source of an unsteady baseline
when operating at high sensitivity. Septa should be preconditioned. Insertion of a new septum in the injection port at the end of
the day for heating overnight will usually eliminate these residuals. A separate oven operating at a temperature similar to that of
the injection port can also be used to process the septa. The septa should be changed at least once a day to minimize gas leaks
and sample blowback. Septa with TFE-fluorocarbon backings minimize organic bleeding and can be used safely for longer periods.
7.2.2 On-Column Injection—While injection into the heated chamber for flash vaporization is the most common injection
set-up, some analyses (for example, organic acids) are better performed with on-column injection to reduce ghosting and peak
tailing and to prevent decomposition of thermally degradable compounds. This capability should be built into the injection system.
When using on-column injection a shorter column life may occur due to solid build up in the injection end of the column.
7.3 Column Oven—The column ovens usually are insulated separately from the injection port and the detector. The oven should
be equipped with a proportional heater and a squirrel-cage blower to assure maximum temperature reproducibility and uniformity
throughout the oven. Reproducibility of oven temperature should be within 0.5°C.
7.3.1 Temperature Programming—Temperature programming is desirable when the analysis involves the resolution of organics
with widely varying boiling points. The column oven should be equipped with temperature programming be-
tween − 15between −15 and 350°C (or range of the method) with selectability of several programming rates between 1 and
20°/min provided. The actual column temperature will lag somewhat behind the oven temperature at the faster programming rates.
Baseline drift will often occur because of increased higher temperatures experienced during temperature programming. This
depends on the stability of the substrate and operating temperature range. Temperatures that approach the maximum limit of the
liquid phase limit the operating range. Utilization of dual matching columns and a differential electrometer can minimize the effect
of drift; however, the drift is reproducible and does not interfere with the analysis in most cases.
7.4 Detector—The combination of high sensitivity and a wide linear range makes the flame ionization detector (FID) the usual
choice in trace aqueous analysis. The flame ionization detector is relatively insensitive to water vapor and to moderate temperature
changes if other operating parameters remain unchanged. If temperature programming is used, the detector should be isolated from
the oven and heated separately to ensure uniform detector temperature. The detector temperature should be set near the upper limit
of the programmed temperature to prevent condensation. The detector should also be shielded from air currents which could affect
the burning characteristics of the flame. Sporadic spiking in the baseline indicates detector contamination; cleaning, preferably with
diluted hydrochloric acid (HCl, 5 + 95), and an ultrasonic wash with water is necessary. Chromic acid also can be used if extreme
care is taken to keep exposure times short and if followed by thorough rinsing. Baseline noise may also be caused by dirty or
corroded electrical contacts at switches due to high impedance feedback.
7.5 Recorder—A strip-chart recorder is recommended to obtain a permanent chromatogram. Chart speeds should be adjustable
between 15 and 90 in./h.
7.6 Power Supply—A 105- to 125-V, a-c source of 60-Hz frequency supplying
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.