1、Designation: F2013 10Standard Test Method forDetermination of Residual Acetaldehyde in PolyethyleneTerephthalate Bottle Polymer Using an Automated StaticHead-Space Sampling Device and a Capillary GC with aFlame Ionization Detector1This standard is issued under the fixed designation F2013; the number
2、 immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1
3、 This test method covers a gas chromatographic proce-dure for the determination of the ppm residual acetaldehyde(AA) present in poly(ethylene terephthalate) (PET) homo-polymers and co-polymers which are used in the manufactureof beverage bottles. This includes sample types of bothamorphous and solid
4、-stated pellet and preform samples, asopposed to the bottle test, Test Method D4509, an acetaldehydetest requiring 24 h of desorption time at 23C into the bottleheadspace and then the concentration of the headspace quan-tified by a similar GC method.1.2 The values stated in SI units are to be regard
5、ed asstandard. No other units of measurement are included in thisstandard.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
6、 the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4509 Test Methods for Determining the 24-Hour Gas(AIR) Space Acetaldehyde Content of Freshly Blown PETBottles3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Te
7、st Method3. Terminology3.1 The terms employed in this test method are commonlyused in normal laboratory practice and require no specialcomment.4. Summary of Test Method4.1 A specified size ( 1000 m) of granulated sample isweighed into a 20-mL head-space vial, sealed, and then heatedat 150C for 60 mi
8、n. After heating, the gas above the sealedsample of PET polymer is injected onto a capillary GC column.The acetaldehyde is separated, and the ppm of acetaldehyde iscalculated.5. Significance and Use5.1 This test method is of particular use as a quality controltool for a molding or synthesis operatio
9、n. Acetaldehyde is avolatile degradation product generated during melt processingof PET. Thus, it becomes trapped in the sidewalls of a moldedarticle and desorbs slowly into the contents packaged therein.In some foods and beverages AA can impart an off-taste that isundesirable, thus, it is important
10、 to know its concentration inPET articles that are to be used in food contact applications.5.2 The desorption conditions of 150 C for 60 min are suchthat no measurable AA is generated by the sample during thedesorption process.6. Sources of Error6.1 Abias is known to exist if the ratio of sample mas
11、s (mg)to head-space vial volume (mL) exceeds a value of ten.6.2 Acetaldehyde is very volatile and must be handledcarefully to avoid sample loss during the calibration procedure.Storing the standard vials in a refrigerator (4 6 2C) is a mustto minimize the error due to volatility.1This test method is
12、 under the jurisdiction of ASTM Committee F02 on FlexibleBarrier Packaging and is the direct responsibility of Subcommittee F02.15 onChemical/Safety Properties.Current edition approved Oct. 1, 2010. Published October 2010. Originallyapproved in 2000. Last previous edition published in 2005 as F2013
13、05. DOI:10.1520/F2013-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved versio
14、n of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Failure to achieve a tight seal on the head-space vial willresult in the loss of acetaldehyde during storage and desorp-ti
15、on, producing a false low value.6.4 Failure to grind the sample to the appropriate particlesize may lead to a false low value for residual AA due to theincreased path length for desorption.6.5 Samples submitted for “residual AA measurement”should be stored in a freezer ( 10C) until they are tested.F
16、ailure to do so can result in lower than expected results.6.6 Excessive grinding of samples can cause residual AAcontained therein to be desorbed. Extensive excessive grindingcan lead to actual melting of the polymer and AA generation.Samples which have been chilled in liquid nitrogen properlyshould
17、 only be in the grinder for ;30 s or less.7. Apparatus7.1 Gas Chromatograph, equipped with a flame ionizationdetector.7.2 Integrator or a PC with data acquisition software.7.3 Head-Space Sampler(a static head-space sampler).7.4 Column, 30-m by 0.53-mm inside diameter (DVB po-rous megabore capillary
18、column or equivalent).7.5 Vials, 20-mL, head-space, with 20-mm septa, 20-mmaluminum caps, and crimper for 20-mm caps.7.6 Crimper, 20-mm.7.7 Decrimper, 20-mm.7.8 Wiley Mill, equipped with an 800 to 1000-m screen, orequivalent.7.9 Syringe, (gas tight) calibrated, with certificate of cali-bration.7.10
19、Small Vacuum Cleaner, with hose attachment forcleaning.7.11 Analytical Balance, capable of accurately weighing toat least 60.0001 g.7.12 Hammer.7.13 Air for EID.7.14 Helium 99.9995 % purity as carrier gas.7.15 Hydrogen 99.9995 % purity for flame ionization detec-tor (FID) or can be used as carrier g
20、as.7.16 Spatular.7.17 Dewer flask.7.18 Glass jar or manila envelope.7.19 Wipe paper or tissue.7.20 Digital syringe, equipped with a 10-L glass syringe.8. Reagents and Materials8.1 Acetaldehyde (AA), 500 ppm AA in water (or 1000ppm), purchased certified standard.8.2 Liquid Nitrogen, plant grade (R-3,
21、 S-3).9. Calibration and StandardizationNOTE 1The following procedure should be performed and recordedonce every three months.9.1 Break open a certified AA standard ampule (ampulesmust be stored in a refrigerator) or prepare AA standard by theattached supplemental procedure. (See Appendix X5.)9.2 Us
22、ing the syringe, fill it by placing the tip in the liquidstandard and quickly moving the plunger up and down severaltime to evacuate any bubbles, then pull the plunger back pastthe 2.000-L mark to 2.200 to 2.250 L.9.3 Wipe the syringe needle with a tissue.9.4 Depress the plunger until the digital re
23、adout is 2.000 L.9.5 Smear the excess liquid that is on the syringe tip on theOUTSIDE of the headspace vial.9.6 Place the syringe inside of the vial so that the tip justtouches the bottom of the vial.9.7 Quickly inject the liquid standard into the vial and swirlthe syringe tip around the inside of t
24、he vial to smear all liquidon the vial walls.9.8 Remove the syringe and IMMEDIATELY cap the vial.9.9 Calculate the weight of AA based on the standardscertified value and a 2.000-L injection volume.NOTE 2Acetaldehyde is very volatile. The AA ampules must bestored in a refrigerator, and the standards
25、prepared immediately afterbreaking open an ampule.9.10 Analyze the working standard by the procedure de-scribed in Section 11, starting with 11.2.11.9.11 Calculate an AA response factor for the standard usingthe following equation:response factor of AA 5 Wt of AA in g/area of AA (1)NOTE 3Due to the
26、error associated with the certified standard,9.1-9.11 should be performed five times using five different standardampules.9.12 Average the five response factors obtained, and use thisvalue for the sample analyses.9.13 Manually enter the calculated response factor in thecalibration list of the integr
27、ator or data system.NOTE 4During a series of sample analyses, a periodic check ofinstrument performance is recommended by placing a few liquid standardsamples throughout the sample set. If these values fall out of theacceptable range as specified by the certificate of analysis, recalibration(9.1-9.1
28、2) should be performed.10. Sample Preparation10.1 Parisons or Preforms or PlaquesMay be cryogeni-cally ground whole, or can be broken into small pieces with ahammer (using liquid nitrogen) and then ground with the aid ofgrinding mill equipped with a 20-mesh or 1000-m screen.The grind should be thoro
29、ughly homogenized before samplingfor AA. If the appropriate size screen is not available on thelarge grinding mill, then it is suggested that the sample beground to 3 to 6 mm on the large mill and the samplethoroughly homogenized. A portion can then be taken to asmaller mill equipped with the 20-mes
30、h or 1000-m screenand cryogenically ground again before analysis.Again the finalsample should be thoroughly homogenized.10.2 PelletsMay be cryogenically ground in a smallgrinding mill using liquid nitrogen. The final sample should bethoroughly homogenized before sampling for analysis.NOTE 5Samples,
31、either preforms, plaques, or pellets, should bechilled in the liquid nitrogen for several minutes until the liquid nitrogenstops boiling and then dropped immediately into the grinder. Sampleshould be sufficiently ground in a few seconds. The grinder should not beallowed to operate more than 20 to 30
32、 s as in such cases undesirablesample heating can occur.F2013 10211. ProcedureNOTE 6Refer to the general operating manual for gas chromatograph,the head-space sampler, and the series integrator for instructions inperforming steps in this procedure.11.1 Adjust the gas chromatograph to the conditions
33、speci-fied in Appendix X1. Adjust the head-space sampler to theconditions in Appendix X2. Set the series integrator to theconditions in Appendix X3.11.2 Sample Analysis:11.2.1 Place 2 to 3 of polymer pellets (or crushed preform)into a small Dewar flask.11.2.2 Cover the polymer with 20 to 40 mL of li
34、quidnitrogen.11.2.3 Allow the polymer to chill under the liquid nitrogenfor approximately 3 min (or until most of the liquid N2 hasevaporated).11.2.4 Turn on the Wiley mill equipped with a 800 to1000-m screen.11.2.5 Slowly pour the remaining liquid nitrogen from theDewar flask through the Wiley mill
35、, followed by the chilledpolymer sample (tapping the sample may be required).11.2.6 Collect the ground polymer in a small glass jar orsmall manila envelope.11.2.7 Turn off the Wiley mill and clean it with a vacuumcleaner.11.2.8 Allow the ground polymer sample to come to roomtemperature (approximatel
36、y 10 min).11.2.9 Weigh approximately 0.2000 (6 0.0200) g, recordedto the nearest 0.0001 g, into a 20-mL head-space vial.11.2.10 Place a septum (with TFE-fluorocarbon side downtowards the inside of the vial) on the vial. Place an aluminumcap on top of the septum, and crimp the cap with a crimperUNTIL
37、 THE CAP CANNOT BE TURNED. Remove thecenter piece of the aluminum cap (if it exists).11.2.11 Place the vial in the appropriate position in thehead-space sampler.11.2.12 Set up head space sampler and a GC acquisitionprogram condition as listed in Table X1.1 and Table X2.1,following instrument operati
38、ng instructions from manufacturer.11.2.13 The head-space sampler will heat the sample for 60min at 150C and then automatically inject the head-space gasand start the gas chromatograph and integrator or data acqui-sition software.11.2.14 The final report will appear on the integrator or thedata syste
39、m when the GC is finished.11.2.15 Determine the peak area for the AA from integratoror data acquisition software.11.2.16 To determine the mass of AA from the sample, areaof AA multiplied by response factor.11.2.17 To determine the concentration in ppm of AA in thepolymer sample, divide the mass of A
40、A (reported in 11.2.16)by the sample weight in the vial (recorded in 11.2.9 as gramsof polymer).12. Calculation12.1 The AA response factor is calculated as described in9.11 and 9.12. The ppm of AA can be calculated manually bymultiplying the response factor and the area of the AA peak,and then divid
41、ing this number by the sample weight in the vial(in grams).13. Report13.1 Report the ppm or g/g of AA to two decimal places.14. Precision and Bias14.1 The following was taken from work completed by theInternational Society of Beverage Technologists (ISBT) sub-committee concerning standardization of
42、method to determineresidual AA in PET.14.2 The number of laboratories, materials, and determina-tions in this study meets the minimum requirements fordetermining precision in accordance with Practice E691.Acomplete report is on file at ASTM Headquarters.414.3 This round robin was conducted by having
43、 one labo-ratory mold PET preforms on a 48-cavity injection moldingmachine and selecting 6 of those cavities as the sample set.Even though these preforms all came from one PET sample(material), each cavity has its own unique AA value, and thus,were treated as six different materials.Also, two differ
44、ent typesof precision and bias were calculated, one based on eachlaboratory using their own calibration standard solution andanother when each laboratory calibrated with a “common”calibration standard.Practice E691 Study MinimumLaboratories: 6 6Materials: 6 4Determinations: 3 214.4 Precision and Bia
45、s With Each Laboratory Using TheirOwn Calibration StandardPrecision, characterized by re-peatability, Sr and r, and reproducibility, SR and R, has beendetermined for the materials to be as follows:Materials Average Sr SR r RMaterial A 5.21 0.1812 0.6403 0.5074 1.7928Material B 6.25 0.4060 0.7464 1.1
46、368 2.0899Material C 6.37 0.2880 0.6713 0.8066 1.8796Material D 7.21 0.3285 0.7743 0.9198 2.1680Material E 7.01 0.4217 0.8350 1.1808 2.3380Material F 5.88 0.3930 0.7168 1.1003 2.007114.4.1 Since the materials used in this study are all from onespecific type of material (PET), but have different AA l
47、evelsbecause they are from different cavities, it makes more sense tohave one set of precision values rather than one for each cavity.This will be derived by squaring each Sr and SR, averagingeach of Sr2and SR2across materials and taking the square root.Sr SR r R0.3466 0.7335 0.9705 2.053814.4.1.1 S
48、tandard Deviation (Sr)Sr is the square root ofthe average within laboratory variance.14.4.1.2 Standard Deviation (SR)SR is the square root ofthe sum of the within laboratory variance and between labo-ratory variance of the laboratory means.14.4.1.3 Repeatabilityr is the interval representing thelarg
49、est expected difference between two test results for the4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:F02-1015.F2013 103same material, obtained by the same operator using the sameequipment on the same day in the same laboratory.Adifferencelarger than r indicates more variation is present than expected.14.4.1.4 ReproducibilityR is the interval representing thelargest expected difference between two test results for thesame material, obtained by different operators using differe
