ASTM D8063-2018 5625 Standard Test Method for Water in Purified Terephthalic Acid (PTA) by Volumetric Karl Fischer Titration.pdf

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1、Designation: D8063 18Standard Test Method forWater in Purified Terephthalic Acid (PTA) by Volumetric KarlFischer Titration1This standard is issued under the fixed designation D8063; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t

2、he 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 This test method covers the determination of water inpurified terephthalic acid (PTA) between 0.01 and 1.00

3、 %(w w) by Volumetric Karl Fischer Titration.1.2 In determining the conformance of the test results usingthis method to applicable specification, results shall be roundedoff in accordance with the rounding-off method of PracticeE29.1.3 The values stated in SI units are to be regarded asstandard. No

4、other units of measurement are included in thisstandard.1.4 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, health, and environmental practices and deter-mine

5、the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations is

6、sued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD4790 Terminology of Aromatic Hydrocarbons and RelatedChemicalsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic

7、Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE203 Test Method for Water Using Volumetric Karl FischerTitrationE300 Practice for Sampling In

8、dustrial ChemicalsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other Document:3OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.12003. Summary of Test Method3.1 A PTA sample is dissolved in a solvent (mixture ofmethanol and pyridine, in the

9、 range of 30 35 % methanol and70 65 % pyridine) and titrated with Karl Fischer reagent,which consists of iodine, sulfur dioxide, methanol and anorganic base.3.2 In the Karl Fischer reaction, water will react with iodineaccording to the following equation:H2O1I21SO213RN1CH3OH2RNHI1RNHSO4CH33.3 The vo

10、lume of Karl Fischer reagent consumed to titratethe sample is converted into the amount of water in the testPTA sample.4. Significance and Use4.1 The presence of water in PTA used for the production ofpolyester is undesirable because it reduces the purity of thePTA.4.2 Determining the amount of wate

11、r content remainingfrom the manufacture of PTA is often required. This testmethod is suitable for setting product specifications and for useas an internal quality control tool where these products areproduced or are used.5. Interference5.1 Certain compounds or classes of compounds interferewith the

12、accurate determination of water by the Karl Fischer1This test method is under the jurisdiction of ASTM Committee D16 onAromatic, Industrial, Specialty and Related Chemicals and is the direct responsi-bility of Subcommittee D16.02 on Oxygenated Aromatics.Current edition approved Jan. 1, 2018. Publish

13、ed May 2018. DOI: 10.1520/D8063-18.2For 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.3Available from U.S. Gover

14、nment Printing Office, Superintendent ofDocuments, 732 N. Capitol St., NW, Washington, DC 20401-0001, http:/www.access.gpo.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with

15、 internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1test method. They include aldehydes, keton

16、es, free halogens,ferric salts and strong oxidizing and reducing agents.6. Apparatus6.1 Karl Fischer Volumetric Titrator, consisting of a titra-tion cell, dual platinum electrode, magnetic stirrer, dispensingburette (2 or 5 mL) and control unit. Any Karl Fischer Titratorcapable of performing Volumet

17、ric Karl Fischer titrations withan electrometric end-point detector can be used in this method.6.2 Microlitre Syringe, 10 L.6.3 Pipette, 10 mL.6.4 Analytical Balance, capable of weighing to the nearest0.0001 g accurately.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall be

18、used in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of theAmericanChemical Society, where such specifications are available.4Other grades may be used, provided it is first ascertained thatthe reagent is of sufficiently high purity to per

19、mit its usewithout lessening the accuracy of the determination.7.2 WaterUnless otherwise indicated, references to watershall be understood to mean reagent water conforming to TypeII of Specification D1193.7.3 Karl Fischer Reagent (one component)may be pre-pared in the laboratory or purchased, contai

20、ning imidazole orpyridine, methanol, iodine and sulfur dioxide. The use ofpyridine-free reagents is recommended. These reagents are lesstoxic, less odorous, and more stable than those containingpyridine. The water equivalence of the Karl Fischer reagent is1 to 2 mg/mL. (WarningKF reagent contains to

21、xic com-pounds. It should be dispensed in a well-ventilated area. Caremust be exercised to avoid inhalation of the reagent or directcontact of the reagent with the skin.)7.4 PyridineLess than 0.05 % (w/w) water. (Warningodorous and harmful if inhaled, swallowed or absorbedthrough the skin. Perform o

22、perations in a hood to avoidpyridine fumes.).7.5 MethanolLess than 0.05 % (w/w) water. (Warninghighly flammable and harmful. May be fatal or cause blindnessif swallowed or inhaled.)7.6 Pyridine-Methanol Mixed Solventin the range of 30 35 % methanol and 70 65 % pyridine (v/v). (Warninghighly flammabl

23、e and vapor harmful.)7.7 Water Standard.7.8 5A Molecular Sieve35mmi.d., used for desiccationof methanol or pyridine solvent. Heating the molecular sieve to500C and cooling down in a desiccator is recommended.NOTE 1If water content in pyridine or methanol is higher than 0.05 %,50 g 5A may be added to

24、 500 mL pyridine or methanol for desiccation.8. Hazards8.1 Consult current federal regulations, suppliers SafetyData Sheets, and local regulations for all materials used in thistest method.9. Sampling9.1 Use only representative samples obtained as describedin Practice E300, unless otherwise specifie

25、d. Care must betaken to eliminate the introduction of water from samplingequipment and atmospheric moisture.9.2 Sample containers should be dry, sealed.9.3 The amount of PTA sample added into the titration cellis dependent upon the quantity of water in the sample. Table 1shows the recommended sample

26、 size. Other sample size maybe used as long as the dissolution of PTA in the pyridine-methanol mixed solvent is not compromised.10. Preparation of Apparatus10.1 Follow the manufacturers directions for preparation ofthe titration apparatus.11. Standardization11.1 Standardize the Karl Fischer reagent

27、daily or as nec-essary.11.2 Add an appropriate amount of pyridine-methanolmixed solvent to the clean, dry titration vessel to cover theelectrodes. The volume of solvent depends on the size of thetitration vessel and sample amount. The 50 mL solvent size for1 g sample and the recommended titer of the

28、 Karl Fischerreagent listed in Table 1 has been found to be satisfactory fortesting water in PTA and can be used as a guideline11.3 All joints and connections to the cell shall be sealed inorder to prevent atmospheric moisture from entering thetitration cell. Select a stirring speed that is sufficie

29、nt to createa well-defined vortex with the solvent.11.4 Pre-titrate the solvent according to the instrumentmanufacturers instructions so that all the moisture has beenremoved prior to introduction of the sample.11.5 Standardize the Karl Fischer reagent with water by thefollowing method:11.5.1 Fill u

30、p a 10 uL syringe with 5 mg water (7.2). Wipethe needle with a paper tissue to remove residual water fromthe needle and accurately measure the weight of the total(syringe plus water) to 0.0001 g. Inject the water into thepyridine-methanol mixed solvent in the titration vessel. Makesure that the tip

31、of the needle is below the liquid level. Reseal4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole,

32、 Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Recommended PTA Sample SizeExpected WaterContent, %Sample Size,gSolvent Volume,mLWaterEquivalence of theKarl FischerReagent, mg/mL0.05 1 50 12D8063 182the vessel

33、immediately, and reweigh the syringe to the nearest0.0001 g. Titrate the water with Karl Fischer reagent until thesteady endpoint is reached for at least 30 s and record theamount of Karl Fischer reagent consumed.11.6 Calculate the water equivalence of the Karl Fischerreagent as follows:F 5 WTwhere:

34、F = water equivalence of the Karl Fischer reagent, mg/mL,W = weight of water added, mg, andT = volume of Karl Fischer reagent required to titrate theadded water, mL.11.7 Repeat steps 11.2 11.6 three times, values of waterweight and water equivalence of the Karl Fischer reagentshould agree within 5 %

35、 relative. Otherwise, discard thecontents of the titration vessel and replace with fresh pyridine-methanol mixed solvent. Repeat the standardization procedure.11.8 Determine and record the mean value of water equiva-lence.11.9 Alternatively, water standard (7.7) can also be used forstandardization o

36、f the Karl Fishcer reagent. Calculate the waterequivalence of the Karl Fischer reagent as follows:F 5 D*ET (1)where:F = water equivalence of the Karl Fischer reagent, mg/mL,D = volume of water standard added, ml,E = concentration of water in water standard, mg/mL, andT = volume of Karl Fischer reage

37、nt required to titrate theadded water standard, mL.12. Procedure12.1 Prior to sample analysis, add an appropriate amount ofpyridine-methanol mixed solvent to the titration vessel andperform the procedure as described in 11.2 11.4.12.2 Weigh the PTA sample, to the nearest 0.0001 g, andquickly transfe

38、r the sample to the titration vessel. Care must betaken to make sure that the sample has been completelytransferred into the solvent.12.3 After the PTA sample is completely dissolved in thepyridine-methanol mixed solvent, titrate the sample with theKarl Fischer reagent until the endpoint is reached.

39、 Record thevolume of the Karl Fischer reagent used for the titration.NOTE 2Insufficient dissolution of PTA in solvent will produceincorrect results.12.4 Perform a blank correction by repeating steps 12.1 12.3 without adding PTA sample. The total analysis time mustinclude the time for sample dissolut

40、ion with a PTA sample.Record the volume of the Karl Fischer reagent used for thetitration.12.5 Alternatively, an automatic drift correction may beused to replace blank correction (12.4). Perform the automaticdrift correction in accordance with the instructions of themanufacturer. Automatic drift cor

41、rection is proven to workwell when background drift is low and stable.13. Calculations13.1 Calculate the water content of the sample as follows:Water content, mass% 5 C12 C2! 3 F 30.1Wwhere:C1= volume of Karl Fischer reagent required to titrate thesample (12.3), mL,C2= volume of Karl Fischer reagent

42、 required to titrate theblank (12.4 or 12.5), mL,F = water equivalence of Karl Fischer reagent, mg/mL, andW = weight of PTA sample, g.14. Report14.1 Report the following information in the report:14.1.1 The complete identification of the sample tested.14.1.2 Report the water content as a percentage,

43、 to thenearest 0.01 %.14.1.3 Any deviation from the procedure specified (forexample, detailed description of operating conditions).14.1.4 Any abnormal situations observed during the test.15. Precision and Bias515.1 The precision of this test method is based on anintralaboratory study of Test Method

44、D8063 conducted in2017. One laboratory tested one PTA sample for water. Everytest result represents an individual determination. The labora-tory reported 20 replicate results for each analysis/materialcombination in order to estimate the repeatability limits of thestandard. Practice E691 was followe

45、d for the design andanalysis of the repeatability data; the details are given inResearch Report RR: RR:D16-1064.15.2 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval repre

46、senting the critical difference between the two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.15.3 Repeatability limits are listed in Table 2.15.4 Reproducibility has not been determined and will bedetermined within fiv

47、e years.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1064. ContactASTM CustomerService at serviceastm.org.TABLE 2 Repeatability LimitsAverage(%)XRepeatabilityStandardDeviationSrRepeatabilityLimitrWatercontentBlankcorrecti

48、onmode0.10 0.006 0.02Driftcorrectionmode0.11 0.006 0.02D8063 18315.5 BiasAt the time of the study, the test specimenschosen for analysis were not accepted reference materialssuitable for determining the bias for the test method, thereforeno statement on bias is being made.16. Quality Guidelines16.1

49、Laboratories shall have a quality control system inplace.16.1.1 Confirm the performance of the test instrument ortest method by analyzing a quality control sample followingthe guidelines of standard statistical quality control practices.16.1.2 A quality control sample is a stable material isolatedfrom the production process and representative of the samplebeing analyzed.16.1.3 When QA/QC protocols are already established inthe testing facility, these protocols are acceptable when theyconfirm the validity of test results.16.1.4 When there ar