1、Designation: D 4526 96 (Reapproved 2007)Standard Practice forDetermination of Volatiles in Polymers by Static HeadspaceGas Chromatography1This standard is issued under the fixed designation D 4526; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 Headspace gas chromatography (GC) involves the de-termination of volatile components in a
3、 polymer solution bygas chromatography of a vapor phase in thermal equilibriumwith the sample matrix. Volatiles in finely ground insolublepolymers can also be determined with and without an extract-ing solvent.1.2 This practice provides two procedures:1.2.1 Procedure AAutomatic headspace analysis.1.
4、2.2 Procedure BManual injection headspace analysis.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of
5、regulatory limitations prior to use. Specific precau-tionary statements are given in Section 6.NOTE 1There is no equivalent ISO standard.2. Referenced Documents2.1 ASTM Standards:2D 4322 Test Method for Residual Acrylonitrile MonomerStyrene-Acrylonitrile Copolymers and Nitrile Rubber byHeadspace Gas
6、 ChromatographyE 260 Practice for Packed Column Gas ChromatographyE 355 Practice for Gas Chromatography Terms and Rela-tionshipsE 594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fluid Chromatography3. Significance and Use3.1 For various reasons, one may want to measur
7、e the levelof unreacted or residual monomer, water, or other volatilecomponents in a polymer sample.3.2 Volatiles of interest are often at trace concentrations.Headspace analysis is suited for determination of these tracecomponents which often cannot be determined by conventionalgas chromatography b
8、ecause of sample decomposition orinterferences.3.3 For polymer analysis, sample treatment for headspaceanalysis is simpler than conventional gas chromatography,where precipitation steps may be required to prevent polymercontamination of the chromatographic column.3.4 This headspace practice will be
9、able to determinequalitatively any component with sufficient vapor pressure. Itis capable of yielding semiquantitative results and can be usedfor relative comparisons between samples.4. Apparatus4.1 Gas Chromatograph, equipped with an appropriatedetector and backflush valve.4.1.1 For Procedure A, an
10、 Automated Headspace Sam-pler,3,4including backflush capability, thermostated sampletray, and associated accessories fulfill these requirements whileproviding for automatic sequential sampling of headspacevapors.4.1.2 Procedure B requires the following additional equip-ment:4.1.2.1 Constant-Temperat
11、ure Bath, capable of maintaining90 6 1C.4.1.2.2 Gas-Tight Gas Chromatographic Syringes, whichcan be heated to 90C for sampling and injection.4.1.2.3 Valve, 6-port for backflush assembly.NOTE 2Appropriate detectors could include the following:(a) Flame ionization (FID) for general organic volatiles,(
12、b) Electron capture (EC) for halogenated species,(c) Nitrogen-phosphorous (NPD) for acrylonitrile,(d) Thermal conductivity (TC) for water, and(e) Hall electroconductivity or photoionization (PID) for vinyl chlo-ride.1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the
13、direct responsibility of Subcommittee D20.70 on Analytical Methods.Current edition approved Sept. 1, 2007. Published November 2007. Originallyapproved in 1985. Last previous edition approved in 2001 as D 4526 - 97(2001)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontac
14、t ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The sole source of supply of the apparatus known to the committee at this timeis Perkin-Elmer Corp., Main Ave., Norwalk, CT 06856.4If you
15、are aware of alternative suppliers, please provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.1*A Summary of Changes section appears at the end of this standard.Copyri
16、ght ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Copyright by ASTM Intl (all rights reserved); Wed Jan 21 22:31:53 EST 2009Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.4.2 Chromatog
17、raphic Columns:4.2.1 Packed Column AnalysisColumn packings4,5foundto be useful for residual monomers (for example, acrylonitrile,vinyl chloride) include Chromosorb or Porapak porous poly-mer packings, 0.4 % Carbowax 1500 liquid phase on CarbopakC support, or 0.19 % picric acid on Carbopak C support.
18、 Othercolumns can be used after it is determined that they give therequired resolution and accuracy for the component of interest.4.2.2 Capillary Column AnalysisChoose a column ca-pable of achieving the required resolution for the componentsof interest. For example, for acrylonitrile monomer, the co
19、lumnof choice is a Quadrex 0072, 25m 3 0.32mm internaldiameter fused silica.4,64.3 Integrator, recorder (5mV full scale), computing inte-grator or appropriate computer data station and softwarecapable of measuring and storing peak area data.4.4 Headspace Vials, septa, ring closures, and vial sealer.
20、4.5 Analytical Balance, capable of weighing to 60.0001 g.4.6 Soap Film Flowmeter and Stopwatch, or other means ofmeasuring gas flow rates.4.7 Pressure Regulators for all required gas cylinders.4.8 Filter-Dryer Assemblies for each required gas cylinder.5. Reagents and Materials5.1 Solvent, Reagent Gr
21、ade, or Best AvailableThe solventshould be free of interferences at the retention time of volatilecompounds determined by this technique. Typical polymersolvents include water, dimethylformamide (DMF), dimethy-lacetamide (DMAC), propylene carbonate, ando-dichlorobenzene. These solvents are readily b
22、ackflushedfrom most chromatographic columns.NOTE 3Volatile contaminants can often be removed by sparging withan inert gas for 24 to 48 h.5.2 Nitrogen, oxygen-free.NOTE 4Helium may also be used as the carrier gas and argon/methaneis the preferred carrier gas for use with electron capture detectors.5.
23、3 Hydrogen, prepurified, for use with flame ionizationdetectors.5.4 Air, breathing or water pumped, for use with flameionization or nitrogen-phosphorus detectors.5.5 Standards, best available, for volatile compounds to beanalyzed using this technique.6. Safety Precautions6.1 Volatiles such as vinyl
24、chloride and acrylonitrile shouldnot be released to the laboratory atmosphere. Prepare standardsand handle samples in a well-ventilated fume hood.6.2 Some of the recommended solvents are flammable.Dimethylacetamide is also absorbed through the skin, so avoidcontact.6.3 Be careful not to come into co
25、ntact with heated chro-matograph parts, such as the detector, column, rotating sampletray, hot sample bottles, etc.6.4 Once heated, sample vials containing polymer volatilesare under pressure. After analysis, vent the pressure with ahypodermic syringe needle connected to a charcoal slug orvented hoo
26、d before removing vials from the constant tempera-ture bath.7. Storage and Sampling7.1 To prevent loss of volatiles from polymer pellets, orresin, store in tightly sealed jars with minimal headspace orheat-sealed pouches constructed of an outer polyester layer, analuminum foil middle layer, and a po
27、lyolefin inner sealinglayer.7.2 For rolled polymer film samples, discard 3 to5moffilmbefore taking the sample for headspace analysis becausevolatiles can be lost by diffusion through the outer film layers.7.3 Powdered resin samples (for example, poly(vinyl chlo-ride) can be weighed directly into a t
28、ared headspace vial. A4-g sample (weighed to the nearest 0.0001 g) should beadequate for determination of many volatiles at the parts permillion (ppm) levels using sensitive ionization detectors.7.4 Polymer pellets or granules and film samples can bedissolved, depending on chemistry of polymer, to f
29、acilitateattaining thermal equilibrium in a reasonable period of time.These samples are weighed (0.56 0.001 g) into headspacevials, then dissolved in 10 mL of an appropriate solvent. Usingionization detection, these 5 % solutions provide sensitivity formany volatiles at ppm levels. Sample size can b
30、e increased toattain sensitivity at lower levels.NOTE 5Freeze grinding polymer pellets or granules with liquidnitrogen and screening through a thirty-mesh screen often works as wellas testing powdered resin. However, some volatiles may be lost even atthese low temperatures.NOTE 6This technique of sa
31、mple preparation requires analysis of thesolvent blank to ensure freedom from interferences at volatile componentretention times.NOTE 7Increased sample sizes can result in viscous solutions. Warm-ing these solutions is often necessary to ensure complete sample dissolu-tion.8. Preparation of the Gas
32、Chromatograph8.1 Refer to Recommended Practice E 260 and the operatorand service manuals of the instrument being used for detailsregarding column installation, flow rate adjustment, and opti-mization of detector sensitivity.8.2 Refer to Practices E 355 and E 594 for information onterms, relationship
33、s, and procedures for testing flame ioniza-tion detectors.8.3 Install the chromatographic column in the instrumentoven. If solvent backflush is to be used, the front portion of thecolumn consists of a short length (3 ft) connected with a lowdead volume tee to the longer analytical column section. Fi
34、g. 1shows a typical backflush assembly for a gas chromatographdesigned for manual headspace analysis.8.4 Adjust the carrier gas flow rate to obtain the samecolumn flow in the analysis and backflush chromatographicmodes.8.5 Switch off the detector combustion gases before discon-necting the column fro
35、m the detector to avoid buildup of anexplosive gas mixture in the GC oven.5The sole source of supply of the apparatus known to the committee at this timeis Supelco, Inc., P.O. Box 628, 146 S. Water St., Bellefonte, PA 16823.6The sole source of supply of the apparatus known to the committee at this t
36、imeis Quadrex Corp., P.O. Box 3881, Woodbridge, CT 06525.D 4526 96 (2007)2Copyright by ASTM Intl (all rights reserved); Wed Jan 21 22:31:53 EST 2009Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.8.6 Condition the column at a temperature that
37、is 10 to 20Cabove the expected operating temperature. With ionizationdetectors, the column should not be connected to the detectorduring the overnight conditioning period.8.7 After conditioning, connect the column to the detectorand optimize detector gas flow (air, hydrogen) for maximumsensitivity.8
38、.8 Set temperatures as follows:8.8.1 Chromatograph Oven (Column), as appropriate.8.8.2 Dosing Needle, 10C above column temperature.8.8.3 Injection Block, 10C above column temperature.8.8.4 Detector, 10C above column temperature.8.8.5 Temperature Bath, 90 to 120C (depending on com-ponent volatility a
39、nd rated bath temperature).9. Procedures9.1 Procedure AAutomated Sample Analysis:9.1.1 Prepare sample solutions in accordance with thecriteria of Section 7, then equilibrate solutions for at least 1 hin the thermostatted sample tray.9.1.2 Optimize analyzer injection time to give maximumsignal. Injec
40、tion times from 6 to 9 s are suitable for mostdeterminations at the ppm level.9.1.3 Adjust the analysis and backflush times consistentwith fast analysis time and freedom from solvent interferences.9.2 Procedure BManual Injection:9.2.1 Prepare sample solutions in accordance with thecriteria of Sectio
41、n 7, then equilibrate solutions for at least 1 hin a constant-temperature bath.9.2.2 Using a warm gas syringe, inject 1.0 mL of theequilibrated sample headspace into the gas chromatographprepared in Section 8.NOTE 8The syringe can be kept warm in a 90C oven betweensamplings.9.2.3 Switch backflush va
42、lve to VENT position 1 min afterelution of the latest volatile component of interest. Backflushtime should be four times as long as the forward flow time.9.2.4 At the end of the predetermined backflush time, returnthe valve to the ANALYSIS position.FIG. 1 Typical 6-Port Valve Backflush AssemblyD 452
43、6 96 (2007)3Copyright by ASTM Intl (all rights reserved); Wed Jan 21 22:31:53 EST 2009Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.9.2.5 Allow at least 2 min for baseline equilibration be-tween samples.10. Report10.1 Report the following in
44、formation:10.1.1 Sample identification,10.1.2 Sample preparation; equilibration time and tempera-ture,10.1.3 Method of calibration, and10.1.4 Concentration of desired volatile components.11. Keywords11.1 gas chromatography; headspace; polymers; volatilesSUMMARY OF CHANGESCommittee D20 has identified
45、 the location of selected changes to this standard since the last issue(D 4526 - 97(2001)e1) that may impact the use of this standard.(1) Five year review with no changes.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedi
46、n this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and mu
47、st be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of th
48、eresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C70
49、0, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 4526 96 (2007)4Copyright by ASTM Intl (all rights reserved); Wed Jan 21 22:31:53 EST 2009Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.
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