ASTM D6520-00
(Practice)Standard Practice for the Solid Phase Micro Extraction (SPME) of Water and its Headspace for the Analysis of Volatile and Semi-Volatile Organic Compounds
Standard Practice for the Solid Phase Micro Extraction (SPME) of Water and its Headspace for the Analysis of Volatile and Semi-Volatile Organic Compounds
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.
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 .
General Information
Relations
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
An American National Standard
Designation:D6520–00
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 D 6520; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope Sampling and Analysis of Water and Wastewater
D 4210 Practice for Intralaboratory Quality Control Proce-
1.1 This practice covers procedures for the extraction of
dures and a Discussion on Reporting Low-Level Data
volatile and semi-volatile organic compounds from water and
D 4448 Guide for Sampling Groundwater Monitoring
its headspace using solid-phase microextraction (SPME).
Wells
1.2 The compounds of interest must have a greater affinity
for the SPME-absorbent polymer or adsorbent or combinations
3. Summary of Practice
of these than the water or headspace phase in which they
3.1 This practice employs adsorbent/liquid or adsorbent/gas
reside.
extractiontoisolatecompoundsofinterest.Anaqueoussample
1.3 Not all of the analytes that can be determined by SPME
is added to a septum-sealed vial. The aqueous phase or its
are addressed in this practice. The applicability of the absor-
headspace is then exposed to an adsorbent coated on a fused
bent polymer, adsorbent, or combination thereof, to extract the
silica fiber. The fiber is desorbed in the heated injection port of
compound(s) of interest must be demonstrated before use.
a GC or GC-MS or the injector of an HPLC.
1.4 This practice provides sample extracts suitable for
3.2 The desorbed organic analytes may be analyzed using
quantitative or qualitative analysis by gas chromatography
instrumental methods for specific volatile or semi-volatile
(GC) or gas chromatography-mass spectrometry (GC-MS).
organic compounds. This practice does not include sample
1.5 Whereused,itistheresponsibilityoftheusertovalidate
extract clean-up procedures.
the application of SPME to the analysis of interest.
1.6 The values stated in SI units are to be regarded as the
4. Significance and Use
standard.
4.1 This practice provides a general procedure for the
1.7 This standard does not purport to address all of the
solid-phase microextraction of volatile and semi-volatile or-
safety concerns, if any, associated with its use. It is the
ganic compounds from an aqueous matrix or its headspace.
responsibility of the user of this standard to establish appro-
Solid sorbent extraction is used as the initial step in the
priate safety and health practices and determine the applica-
extraction of organic constituents for the purpose of quantify-
bility of regulatory limitations prior to use. For specific hazard
ing or screening for extractable organic compounds.
statements, see Section 9.
4.2 Typical detection limits that can be achieved using
SPME techniques with gas chromatography with flame ioniza-
2. Referenced Documents
tion detector (FID), electron capture detector (ECD), or with a
2.1 ASTM Standards:
2 mass spectrometer (MS) range from mg/L to µg/L. The
D 1129 Terminology Relating to Water
3 detection limit, linear concentration range, and sensitivity of
D 1193 Specification for Reagent Water
the test method for a specific organic compound will depend
D 3370 Practices for Sampling Water from Closed Con-
upon the aqueous matrix, the fiber phase, the sample tempera-
duits
ture, sample volume, sample mixing, and the determinative
D 3694 Practices for Preparation of Sample Containers and
technique employed.
for Preservation of Organic Constituents
4.3 SPME has the advantages of speed, no desorption
D 3856 Practice for Evaluating Laboratories Engaged in
solvent,simpleextractiondevice,andtheuseofsmallamounts
of sample.
4.3.1 Extraction devices vary from a manual SPME fiber
This practice is under the jurisdiction ofASTM Committee D-19 on Water and
holder to automated commercial device specifically designed
is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
Organic Substances in Water. for SPME.
Current edition approved Jan. 10, 2000. Published May 2000.
Annual Book of ASTM Standards, Vol 11.01.
3 4
Annual Book of ASTM Standards, Vol 11.02. Annual Book of ASTM Standards, Vol 11.04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6520–00
4.3.2 Listed below are examples of organic compounds that the sample and the specific instrumental analysis method used.
can be determined by this practice. This list includes both high Matrix interferences may be reduced by choosing an appropri-
and low boiling compounds. ate SPME adsorbing fiber.
Volatile Organic Compounds (1,2,3)
7. The Technique of SPME
Pesticides, General (4,5)
Organochlorine Pesticides (6)
7.1 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).
4.3.3 SPME may be used to screen water samples prior to
7.2 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.
5. Principles of SPME
7.3 Push the sheath with fiber retracted through the vial
5.1 SPME is an equilibrium technique where analytes are
septum and lower into the body of the vial. Inject the fiber into
not completely extracted from the matrix.With liquid samples,
theheadspaceortheaqueousportionofthesample(seeFig.2).
the recovery is dependent on the partitioning or equilibrium of
Generally, when 2-mL vials are used, headspace sampling
analytes among the three phases present in the sampling vial:
requires approximately 0.8 mL of sample and direct sampling
the aqueous sample and headspace (Phase 1), the fiber coating
requires 1.2 mL.
and aqueous sample (Phase 2), and the fiber coating and the
7.4 Organic compounds are absorbed onto the fiber phase
headspace (Phase 3):
for a predetermined time. This time can vary from less than 1
~Phase 1! K 5 C /C (1)
1 L g
min for volatile compounds with high diffusion rates such as
volatile organic solvents, to 30 min for compounds of low
~Phase 2! K 5 C /C (2)
2 F L volatility such as PAHs.
7.5 Withdraw the fiber into the protective sheath and pull
~Phase 3! K 5 C /C (3)
3 F G the sheath out of the sampling vial.
7.6 Immediately insert the sheath through the septum of the
whereC ,C andC are the concentrations of the analyte in
L G F
hot GC injector (see Fig. 3), push down the plunger, and insert
these phases.
the fiber into the injector liner where the analytes are thermally
5.1.1 Distribution of the analyte among the three phases can
desorbed and subsequently separated on the GC column.
be calculated using the following:
7.6.1 The blunt 23-gage septum-piercing needle of the
C V 5 C V 1 C V 1 C V (4)
0 L G G L L F F
SPME is best used with a septumless injector seal. These are
5.1.2 Concentration of analyte in fiber can be calculated
manufactured by several sources for specific GC injectors.
using the following:
C 5 C V K K //V 1 K V 1 K K V (5)
F 0 L 1 2 G 1 L 1 2 F
6. Interferences
6.1 Reagents, glassware, septa, fiber coatings and other
sample processing hardware may yield discrete artifacts or
elevated baselines that can cause poor precision and accuracy.
6.1.1 Glassware should be washed with detergent, rinsed
with water, and finally rinsed with distilled-in-glass acetone.
Air dry or in 103°C oven. Additional cleaning steps may be
required when the analysis requires levels of µg/L or below.
Once the glassware has been cleaned, it should be used
immediately or stored wrapped in aluminum foil (shiny side
out) or under a stretched sheet of PTFE-fluorocarbon.
6.1.2 Plastics other than PTFE-fluorocarbon should be
avoided. They are a significant source of interference and can
adsorb some organics.
6.1.3 Afield blank prepared from water and carried through
sampling, subsequent storage, and handling can serve as a
check on sources of interferences from the containers.
6.2 When performing analyses for specific organic com-
pounds, matrix interferences may be caused by materials and
NOTE 1—This figure is Fig. 5, p. 218, Vol 37, Advances in Chroma-
constituentsthatarecoextractedfromthesample.Theextentof
tography, 1997. Used with permission.
such matrix interferences will vary considerably depending on FIG. 1 SPME Fiber Holder Assembly
D6520–00
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.
7.6.3 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.
7.7 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).
7.8 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
FIG. 2 Process for Adsorption of Analytes from Sample Vial with
desorption with little or no analyte carryover.
SPME Fiber
8. Selection of Fiber Phase
8.1 The selection of the fiber phase depends on several
factors, including:
8.1.1 The media being extracted by the fiber, aqueous or
headspace,
8.1.2 The volatility of the analyte such as gas phase hydro-
carbons to semivolatile pesticides, and
8.1.3 The polarity of the analyte.
8.2 A selection of fiber phases and common applications is
shown in Table 1.
9. Apparatus
9.1 SPMEHolder,manualsamplingorautomatedsampling.
9.2 SPME Fiber Assembly.
9.3 SPME Injector Liner, that is, inserts for gas chromato-
graphs.
9.4 Septum Replacement Device, Merlin or Jade.
9.5 Vials, with septa and caps, for manual or automation.
FIG. 3 Injection Followed by Desorption of SPME Fiber in
For automation, use either 2- or 10–mL vials.
Injection Port of Chromatograph
10. Reagents
7.6.2 A conventional GC septum may be used with SPME. 10.1 PurityofWater—Unlessotherwiseindicated,reference
A septum lasts for 100 runs or more. To minimize septum towatershallbeunderstoodtomeanreagentwaterconforming
failure, install a new septum, puncture with a SPME sheath to Type II of Specification D 1193.
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
CarboxenY 1006-PDMS Bi-Polar Bi-polar light hydrocarbons, polar solvents, VOCs; sulfur gases, useful for air monitoring
DVB-CarboxenY—PDMS Bi-Polar volatiles
A
Phase more of a solid, so slower diffusion rates.
D6520–00
10.2 Chemicals, standard materials and surrogates should matrix. Mixing is much less effective for volatiles and is
be reagent orACS grade or better. When they are not available generally not required.
as reagent grade, they should have an assay of 90 % or better. 13.3 Matrix modification through the addition of salt to the
10.3 Sodium Chloride (NaCl), reagent grade, granular. aqueous phase may be used to drive polar compounds into the
headspace. It has very little effect on nonpolar compounds.
11. Hazards
Adding salts to the sample also minimizes matrix differences
when there are sample to sample variations in ionic strength
11.1 The toxicity and carcinogenicity of chemicals used in
13.4 Heating the sample is often used to increase the
this practice have not been precisely defined. Each chemical
sensitivity in static headspace; it is much less effective with
should be treated as a potential health hazard. Exposure to
SPME. The equilibrium tends to be shifted to the headspace
these chemicals should be minimized. Each laboratory is
rather than to the fiber.
responsible for maintaining awareness of OSHA regulations
13.5 Ratio of Liquid to Headspace—With nonpolar ana-
regarding safe handling of chemicals used in this practice.
lytes, the sensitivity is enhanced when the proportion of liquid
11.2 If using either solvent, the hazard of peroxide forma-
phaseisincreased.Themagnitudeoftheenhancementdepends
tion should be considered. Test for the presence of peroxide
upon the partition coefficient.
prior to use.
13.6 Vial Size—Larger sampling vials are not effective in
increasing the sensitivity if the relative volumes of headspace
12. Sample Handling
and liquid are the same. The precision of measurements is not
12.1 There are many procedures for acquiring representa-
affected by vial size with direct aqueous sampling.The relative
tive samples of water. The choice of procedure is site and
standard deviation of sampling the headspace is lower with the
analysis specific.There are severalASTM guides and practices
larger vials (>10 mL) than smaller ones (2 mL). Larger vials
for sampling. Two good sources are Practices D 3370 and
are easier to fill with solid and semisolid samples.
Guide D 4448.
13.7 Acidity of Sample—When determining acidic com-
12.2 The recommended sample size is 40 to 100 mL. More
pounds, such a
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.