ASTM D6520-06(2012)

Standard Practice for the Solid Phase Micro Extraction (SPME) of Water and its Headspace for the Analysis of Volatile and Semi-Volatile Organic Compounds

SIGNIFICANCE AND USE
This practice provides a general procedure for the solid-phase microextraction of volatile and semi-volatile organic compounds from an aqueous matrix or its headspace. Solid sorbent extraction is used as the initial step in the extraction of organic constituents for the purpose of quantifying or screening for extractable organic compounds.
Typical detection limits that can be achieved using SPME techniques with gas chromatography with flame ionization detector (FID), electron capture detector (ECD), or with a mass spectrometer (MS) range from mg/L to μg/L. The detection limit, linear concentration range, and sensitivity of the test method for a specific organic compound will depend upon the aqueous matrix, the fiber phase, the sample temperature, sample volume, sample mixing, and the determinative technique employed.
SPME has the advantages of speed, no desorption solvent, simple extraction device, and the use of small amounts of sample.
Extraction devices vary from a manual SPME fiber holder to automated commercial device specifically designed for SPME.
Listed below are examples of organic compounds that can be determined by this practice. This list includes both high and low boiling compounds. The numbers in parentheses refer to references at the end of this standard.
Volatile Organic Compounds (1,2,3) Pesticides, General (4,5) Organochlorine Pesticides (6) Organophosphorous Pesticides (7,8) Polyaromatic Hydrocarbons (9,10) Polychlorinated biphenyls (10) Phenols (11) Nitrophenols (12) Amines (13)
SPME may be used to screen water samples prior to purge and trap extraction to determine if dilution is necessary, thereby eliminating the possibility of trap overload.
SCOPE
1.1 This practice covers procedures for the extraction of volatile and semi-volatile organic compounds from water and its headspace using solid-phase microextraction (SPME).
1.2 The compounds of interest must have a greater affinity for the SPME-absorbent polymer or adsorbent or combinations of these than the water or headspace phase in which they reside.
1.3 Not all of the analytes that can be determined by SPME are addressed in this practice. The applicability of the absorbent polymer, adsorbent, or combination thereof, to extract the compound(s) of interest must be demonstrated before use.
1.4 This practice provides sample extracts suitable for quantitative or qualitative analysis by gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS).
1.5 Where used, it is the responsibility of the user to validate the application of SPME to the analysis of interest.
1.6 The values stated in SI units are to be regarded as the standard.
1.7 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 and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 10.

General Information

• Status: Historical
• Publication Date: 14-Jun-2012
• 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 D6520-06 - Standard Practice for the Solid Phase Micro Extraction (SPME) of Water and its Headspace for the Analysis of Volatile and Semi-Volatile Organic Compounds
• Effective Date: 15-Jun-2012
• Replaced By: ASTM D6520-18 - Standard Practice for the Solid Phase Micro Extraction (SPME) of Water and its Headspace for the Analysis of Volatile and Semi-Volatile Organic Compounds
• Effective Date: 15-Dec-2018
• Referred By: ASTM D6889-03(2017) - Standard Practice for Fast Screening for Volatile Organic Compounds in Water Using Solid Phase Microextraction (SPME)
• Effective Date: 15-Jun-2012

Standards Content (Sample)

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: D6520 − 06 (Reapproved 2012)
Standard Practice for
the Solid Phase Micro Extraction (SPME) of Water and its
Headspace for the Analysis of Volatile and Semi-Volatile
Organic Compounds
This standard is issued under the fixed designation D6520; 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 D1193 Specification for Reagent Water
D3370 Practices for Sampling Water from Closed Conduits
1.1 This practice covers procedures for the extraction of
D3694 Practices for Preparation of Sample Containers and
volatile and semi-volatile organic compounds from water and
for Preservation of Organic Constituents
its headspace using solid-phase microextraction (SPME).
D3856 Guide for Management Systems in Laboratories
1.2 The compounds of interest must have a greater affinity
Engaged in Analysis of Water
for the SPME-absorbent polymer or adsorbent or combinations
D4210 Practice for Intralaboratory Quality Control Proce-
of these than the water or headspace phase in which they
dures and a Discussion on Reporting Low-Level Data
reside. 3
(Withdrawn 2002)
D4448 Guide for Sampling Ground-Water MonitoringWells
1.3 Not all of the analytes that can be determined by SPME
are addressed in this practice. The applicability of the absor-
3. Terminology
bent polymer, adsorbent, or combination thereof, to extract the
compound(s) of interest must be demonstrated before use.
3.1 Definitions—For definitions of terms used in this
practice, refer to Terminology D1129.
1.4 This practice provides sample extracts suitable for
quantitative or qualitative analysis by gas chromatography
4. Summary of Practice
(GC) or gas chromatography-mass spectrometry (GC-MS).
4.1 This practice employs adsorbent/liquid or adsorbent/gas
1.5 Whereused,itistheresponsibilityoftheusertovalidate
extractiontoisolatecompoundsofinterest.Anaqueoussample
the application of SPME to the analysis of interest.
is added to a septum-sealed vial. The aqueous phase or its
1.6 The values stated in SI units are to be regarded as the
headspace is then exposed to an adsorbent coated on a fused
standard.
silica fiber.The fiber is desorbed in the heated injection port of
a GC or GC-MS or the injector of an HPLC.
1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.2 The desorbed organic analytes may be analyzed using
responsibility of the user of this standard to establish appro-
instrumental methods for specific volatile or semi-volatile
priate safety and health practices and determine the applica-
organic compounds. This practice does not include sample
bility of regulatory limitations prior to use. For specific hazard
extract clean-up procedures.
statements, see Section 10.
5. Significance and Use
2. Referenced Documents
5.1 This practice provides a general procedure for the
2.1 ASTM Standards:
solid-phase microextraction of volatile and semi-volatile or-
D1129 Terminology Relating to Water
ganic compounds from an aqueous matrix or its headspace.
Solid sorbent extraction is used as the initial step in the
extraction of organic constituents for the purpose of quantify-
This practice is under the jurisdiction ofASTM Committee D19 on Water and
ing or screening for extractable organic compounds.
is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
Organic Substances in Water.
5.2 Typical detection limits that can be achieved using
Current edition approved June 15, 2012. Published June 2012. Originally
SPME techniques with gas chromatography with flame ioniza-
approved in 2000. Last previous edition approved in 2012 as D6520 – 06. DOI:
tion detector (FID), electron capture detector (ECD), or with a
10.1520/D6520-06R12.
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 last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6520 − 06 (2012)
mass spectrometer (MS) range from mg/L to µg/L. The Once the glassware has been cleaned, it should be used
detection limit, linear concentration range, and sensitivity of immediately or stored wrapped in aluminum foil (shiny side
the test method for a specific organic compound will depend out) or under a stretched sheet of PTFE-fluorocarbon.
upon the aqueous matrix, the fiber phase, the sample 7.1.2 Plastics other than PTFE-fluorocarbon should be
temperature, sample volume, sample mixing, and the determi- avoided. They are a significant source of interference and can
native technique employed. adsorb some organics.
7.1.3 Afield blank prepared from water and carried through
5.3 SPME has the advantages of speed, no desorption
sampling, subsequent storage, and handling can serve as a
solvent,simpleextractiondevice,andtheuseofsmallamounts
check on sources of interferences from the containers.
of sample.
5.3.1 Extraction devices vary from a manual SPME fiber 7.2 When performing analyses for specific organic
holder to automated commercial device specifically designed compounds, matrix interferences may be caused by materials
for SPME. and constituents that are coextracted from the sample. The
5.3.2 Listed below are examples of organic compounds that extent of such matrix interferences will vary considerably
depending on the sample and the specific instrumental analysis
can be determined by this practice. This list includes both high
and low boiling compounds. The numbers in parentheses refer methodused.Matrixinterferencesmaybereducedbychoosing
to references at the end of this standard. an appropriate SPME adsorbing fiber.
Volatile Organic Compounds (1,2,3)
8. The Technique of SPME
Pesticides, General (4,5)
Organochlorine Pesticides (6)
8.1 The technique of SPME uses a short, thin solid rod of
Organophosphorous Pesticides (7,8)
fused silica (typically 1-cm long and 0.11-µm outer diameter),
Polyaromatic Hydrocarbons (9,10)
Polychlorinated biphenyls (10) coated with a film (30 to 100 µM) of a polymer, copolymer,
Phenols (11)
carbonaceousadsorbent,oracombinationofthese.Thecoated,
Nitrophenols (12)
fused silica (SMPE fiber) is attached to a metal rod and the
Amines (13)
entire assembly is a modified syringe (see Fig. 1).
5.3.3 SPME may be used to screen water samples prior to
8.2 In the standby position, withdraw the fiber into a
purge and trap extraction to determine if dilution is necessary,
protective sheath. Place an aqueous sample containing organic
thereby eliminating the possibility of trap overload.
analytes or a solid containing organic volatiles into a vial, and
seal the vial with a septum cap.
6. Principles of SPME
6.1 SPME is an equilibrium technique where analytes are 8.3 Push the sheath with fiber retracted through the vial
septum and lower into the body of the vial. Inject the fiber into
not completely extracted from the matrix.With liquid samples,
the recovery is dependent on the partitioning or equilibrium of theheadspaceortheaqueousportionofthesample(seeFig.2).
Generally, when 2-mL vials are used, headspace sampling
analytes among the three phases present in the sampling vial:
the aqueous sample and headspace (Phase 1), the fiber coating requires approximately 0.8 mL of sample and direct sampling
requires 1.2 mL.
and aqueous sample (Phase 2), and the fiber coating and the
headspace (Phase 3):
Phase1 K 5 C /C (1)
~ !
1 L g
Phase2 K 5 C /C (2)
~ !
2 F L
~Phase3! K 5 C /C (3)
3 F G
where C ,C and C are the concentrations of the analyte in
L G F
these phases.
6.1.1 Distribution of the analyte among the three phases can
be calculated using the following:
C V 5 C V 1C V 1C V (4)
0 L G G L L F F
6.1.2 Concentration of analyte in fiber can be calculated
using the following:
C 5 C V K K /V 1K V 1K K V (5)
F 0 L 1 2 G 1 L 1 2 F
7. Interferences
7.1 Reagents, glassware, septa, fiber coatings and other
sample processing hardware may yield discrete artifacts or
elevated baselines that can cause poor precision and accuracy.
7.1.1 Glassware should be washed with detergent, rinsed
with water, and finally rinsed with distilled-in-glass acetone.
NOTE 1—This figure is Fig. 5, p. 218, Vol 37, Advances in
Air dry or in 103°C oven. Additional cleaning steps may be
Chromatography, 1997. Used with permission.
required when the analysis requires levels of µg/L or below. FIG. 1 SPME Fiber Holder Assembly
D6520 − 06 (2012)
8.6.2 A conventional GC septum may be used with SPME.
A septum lasts for 100 runs or more. To minimize septum
failure, install a new septum, puncture with a SPME sheath
three or four times, and remove and inspect the new septum.
Pull off and discard any loose particles of septum material, and
reinstall the septum.
8.6.3 The user should monitor the head pressure on the
chromatographic column as the fiber sheath enters and leaves
the injector to verify the integrity of the seal.Asubtle leak will
be indicated by unusual shifts in retention time or the presence
of air in a mass spectrometer.
8.7 Ensure that the injector liner used with SPME is not
packed or contains any physical obstructions that can interfere
withthefiber.Theinnerdiameteroftheinsertshouldoptimally
should be about 0.75 to 0.80 mm. Larger inserts (2 to 4 mm)
may result in broadening of early eluting peaks. SPME inserts
are available commercially and may be used for split or
splitless injection. With splitless injection, the vent is timed to
open at the end of the desorption period (usually 2 to 10 min).
FIG. 2 Process for Adsorption of Analytes from Sample Vial with
SPME Fiber
8.8 Injector temperature should be isothermal and normally
10 to 20°C below the temperature limit of the fiber or the GC
column (usually 200 to 280°C), or both. This provides rapid
8.4 Organic compounds are absorbed onto the fiber phase
desorption with little or no analyte carryover.
for a predetermined time. This time can vary from less than 1
min for volatile compounds with high diffusion rates such as
9. Selection of Fiber Phase
volatile organic solvents, to 30 min for compounds of low
9.1 The selection of the fiber phase depends on several
volatility such as PAHs.
factors, including:
8.5 Withdraw the fiber into the protective sheath and pull
9.1.1 The media being extracted by the fiber, aqueous or
the sheath out of the sampling vial.
headspace,
8.6 Immediately insert the sheath through the septum of the 9.1.2 The volatility of the analyte such as gas phase hydro-
carbons to semivolatile pesticides, and
hot GC injector (see Fig. 3), push down the plunger, and insert
the fiber into the injector liner where the analytes are thermally 9.1.3 The polarity of the analyte.
desorbed and subsequently separated on the GC column.
9.2 A selection of fiber phases and common applications is
8.6.1 The blunt 23-gage septum-piercing needle of the
shown in Table 1.
SPME is best used with a septumless injector seal. These are
manufactured by several sources for specific GC injectors.
10. Apparatus
10.1 SPME Holder, manual sampling or automated sam-
pling.
10.2 SPME Fiber Assembly.
10.3 SPME Injector Liner, that is, inserts for gas chromato-
graphs.
10.4 Septum Replacement Device, Merlin or Jade.
10.5 Vials, with septa and caps, for manual or automation.
For automation, use either 2- or 10–mL vials.
11. Reagents
11.1 Purity of Water—Unless otherwise indicated, reference
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.
11.2 Chemicals,standardmaterialsandsurrogatesshouldbe
reagent orACS grade or better. When they are not available as
reagent grade, they should have an assay of 90 % or better.
FIG. 3 Injection Followed by Desorption of SPME Fiber in Injec-
tion Port of Chromatograph 11.3 Sodium Chloride (NaCl), reagent grade, granular.
D6520 − 06 (2012)
TABLE 1 Commercially Available SPME Fibers for GC and GC/MS
Phase Polarity Features and Applications
Polydimethylsiloxane, 100 µM (PDMS) Non-polar High sample capacity, wide variety of applications; volatile organics to semivolatiles
PDMS, 30 µM Non-polar Semivolatiles, pesticides. Faster desorption, carryover minimized
PDMS, 7 µM Non-Polar Semivolatiles, higher desorption temperatures (320°C), reduces sample capacity
A
Polyacrylate, 85 µM Polar Phenols, polars, semivolatiles
Carbowax/divinyl benzene, 65 µM (CW-DVB) Polar Alcohols
CW-templated resin, 50 µM Polar Surfactants
PDMS-DVB, 65 µM Bi-Polar Alcohols, amines
PDMS-DVB, 60 µM Bi-Polar For HPLC, special more durable phase
Carboxen™ 1006-PDMS Bi-Polar Bi-polar light hydrocarbons, polar solvents, VOCs; sulfur gases, useful for air monitoring
DVB-Carboxen™—PDMS Bi-Polar volatiles
A
Phase more of a solid, so slower diffusion rates.
12. Hazards volatiles. Semi-volatiles are best extracted with SPME liquid
sampling. Headspace sampling is desirable if samples contain
12.1 The toxicity and carcinogenicity of chemicals used in
nonvolatile compounds such as salts, humic acids, or proteins.
this practice have not been precisely defined. Each chemical
should be treated as a potential health hazard. Exposure to
14.2 Sample mixing is effective in increasing the response
these chemicals should be minimized. Each laboratory is
of semi-volatile analytes. It reduces the equilibrium time for
responsible for maintaining awareness of OSHA regulations
the adsorption of the semi-volatile components. Mixing re-
regarding safe handling of chemicals used in this practice.
duces any analyte depleted area around the fiber phase and
12.2 If using either solvent, the hazard of peroxide forma- increases the diffusion of larger molecules from the aqueous
matrix. Mixing is much less effective for volatiles and is
tion should be considered. Test for the presence of peroxide
prior to use. generally not required.
14.3 Matrix modification through the addition of salt to the
13. Sample Handling
aqueous phase may be used to drive polar compounds into the
13.1 There are many procedures for acquiring representa-
headspace. It has very little effect on nonpolar compounds.
tive samples of water. The choice of procedure is site and
Adding salts to the sample also minimizes matrix differences
analysis specific.There are severalASTM guides and practices
when there are sample to sample variations i
...