1、Designation: D7883 13Standard Test Method forDetermination of 4-Carboxybenzaldehyde and p-Toluic Acidin Purified Terephthalic Acid by Weak Anion Exchange HighPerformance Liquid Chromatography1This standard is issued under the fixed designation D7883; the number immediately following the designation
2、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 This test method2covers the determinat
3、ion of the4-Carboxybenzaldehyde (4-CBA) and p-Toluic acid (p-TOL)in purified terephthalic acid (PTA) by weak anion exchangehigh performance liquid chromatography (HPLC). Thismethod is applicable for 4-CBA from 2 to 500 mg/kg and forp-TOL from 10 to 500 mg/kg, respectively.1.2 In determining the conf
4、ormance 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 other units of measurement are included in thisstandard.1.4 This standar
5、d 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM
6、 Standards:3D1193 Specification for Reagent WaterD4790 Terminology of Aromatic Hydrocarbons and RelatedChemicalsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conforman
7、ce with SpecificationsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE682 Practice for Liquid Chromatography Terms and Rela-tionshipsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Document:4EN ISO 8213 Chemical produc
8、ts for industrial useSampling techniquesSolid chemical products in theform of particles varying from powders to coarse lumps2.3 Other Document:5OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.12003. Summary of Test Method3.1 Weak Anion Exchange HPLC MethodPTA sample isdissolved in ammonium hyd
9、roxide solution. After pHadjustment, a fixed volume of this solution is injected into ahigh performance liquid chromatograph equipped with a UVdetector. An anion-exchange column is used to separate theimpurities 4-CBA and p-TOL from PTA. The external standardcalibration is used for quantification.4.
10、 Significance and Use4.1 The presence of 4-CBA and p-TOL in PTA used for theproduction of polyester is undesirable because they can slowdown the polymerization process, and 4-CBA is also impartingcoloration to the polymer due to thermal instability.4.2 Determining the amount of 4-CBA and p-TOL remai
11、n-ing from the manufacture of PTA is often required. This testmethod is suitable for setting specifications and could be usedas an internal quality control tool where these products areproduced or are used.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and
12、Related Chemicals and is the direct responsibility ofSubcommittee D16.02 on Oxygenated Aromatics.Current edition approved Aug. 1, 2013. Published October 2013. DOI: 10.1520/D7883-13.2This standard is based on SH/T 1612.7-1995 Purified terephthalic acid forindustrial usedetermination of p-Toluic Acid
13、, 4-Carboxybenzaldehyde-HPLC,copyright SINOPEC, 22 Chaoyangmen North Street, Chaoyang District, Beijing,China 100728. A copy of SH/T 1612.7-1995 may be obtained from ChinaPetrochemical Press, www.sinopec-.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer S
14、ervice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.5Available from U.S. Governme
15、nt Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Apparatus5.1 High Performance Liquid Chromatograp
16、h (HPLC)any HPLC capable of pumping the mobile phase at flow ratesbetween 0.1 and 2.0 mL/min, with a pressure between 0 and 40MPa and a pulsation of less than 1 % full scale deflection underthe test conditions described in Table 1. The S/N (signal tonoise) ratio should be 3:1 or greater for 2 mg/kg
17、4-CBAand 10mg/kg p-TOL.5.2 Sample Injection Systemcapable of injecting 1 to 25L, using either partial or full loop mode, with a repeatabilityof 61%.5.3 Detector, Variable Wavelength Ultraviolet PhotometricDetector (VWD), Multi-wavelength Detector, or PhotometricDiode Array Detector (PDA), capable of
18、 operating at 236 and258 nm.5.4 Column Ovenany suitable HPLC column oven (blockheating or air circulating) capable of maintaining a constanttemperature of 61C within the range of 20 to 70C.5.5 Chromatography Data System.5.6 HPLC Columns:5.6.1 Guard Columna stainless steel column placed infront of th
19、e analytical column is recommended. A column,packed with the same stationary phase as the analyticalcolumn, 3 to 5 mm ID and 50 to 100 mm length, has beenfound to be satisfactory. Other hydrophilic chemically-bondedsilica stationary phases can also be used.5.6.2 Analytical Columna stainless steel HP
20、LC columnpacked with amino-bonded silica stationary phase is suitable.See Table 1 for recommended operating conditions.5.7 Analytical Balancereadable to 60.0001 g.5.8 pH Meter.5.9 Sample Filtera disposable syringe filter made ofcellulose acetate, with a pore size between 0.22 and 0.45 m,and is chemi
21、cally inert to aqueous solutions, is recommendedfor the removal of particulate matter from the sample solution.5.10 Vacuum Filtercapable of filtering mobile phase.6. Reagents and Materials6.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the reagent g
22、radespecification for analytical reagents of the American ChemicalSociety, where such specifications are available.6Other gradesmay be used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe performance or accuracy of the determina
23、tion. Reagentchemicals shall be used for all tests.NOTE 1Calibration and detection limits of this test method can bebiased by the purity of the reagents.6.2 Ammonium Dihydrogen Phosphate(WarningAmmonium dihydrogen phosphate may cause irritation withonly minor residual injury.)6.3 Ammonium Hydroxide,
24、 25 to 28 % (wt).6.4 Phosphoric Acid, 82 % (wt).6.5 AcetonitrileHPLC grade. (WarningAcetonitrile isflammable and hazardous in case of skin and eye contact,ingestion or inhalation.)6.6 MethanolHPLC grade. (WarningMethanol ishighly flammable and toxic by inhalation, ingestion or skincontact.)6.7 Water
25、HPLC grade.6.8 Ammonium Hydroxide Solutionammonium hydroxidemixed with water as 1:1 (V:V).6.9 Phosphoric Acid Solutionphosphoric acid mixed withwater as 1:4 (V:V).6.10 PTA Calibration StandardAcertified PTAcalibrationstandard with known amounts of 4-CBA and p-TOL is re-quired. If it is not commercia
26、lly available, please refer toAnnex A1 for determining the concentrations of 4-CBA andp-TOL in a PTA sample. The calibrated PTA sample can beserved as a PTA calibration standard.6.11 Mobile Phase:6.11.1 0.1 Mol/L NH4H2PO4Solution: Acetonitrile (orMethanol) = 9:1 (v/v)Dissolve approximately 11.50 g o
27、fammonium dihydrogen phosphate in 850 mL of water, adjustpH to 4.3 by using phosphoric acid solution. Transfer theresulting solution to a 1000 mL volumetric flask, add 100 mLof acetonitrile or methanol, dilute with water to the mark.NOTE 2It is recommended to degas and filter the mobile phase before
28、use. Degassing can be done conveniently, on-line or off-line by heliumsparging, vacuum degassing or ultrasonic agitation.7. Hazards7.1 Consult current federal regulations, suppliers MaterialSafety Data Sheets, and local regulations for all materials usedin this test method.8. Sampling, Test Specimen
29、s, and Test Units8.1 Use only representative samples obtained as describedin EN ISO 8213, unless otherwise specified.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical S
30、ociety, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Recommended Operating ConditionsColumn Weak Alkali Anion ExchangeStationary phase (-NMe2) ch
31、emically bonded silicaParticle size 3 mMaterial of column stainless steelLength of column 50 mmInner diameter 45 mmMobile phase0.1 mol/L NH4H2PO4solution:acetonitrile(or methanol) =9:1Flow rate 0.81.2 mL/minUV detector258 nm for 4-CBA236 nm for p-TOLInjection amount 20 LColumn temperature 3040CD7883
32、 1329. Preparation of Apparatus9.1 Set up the pump, sample injection system, column,oven, detector, and chromatography data system in accordancewith the manufacturers instructions. Adjust the instrument tothe conditions described in Table 1, allowing sufficient time forthe equipment to reach equilib
33、rium which is indicated by astable horizontal baseline. For a new column, four to six hoursof equilibration time may be required.NOTE 3A gradient mobile phase can also be used for improvingchromatograph.10. Calibration10.1 Weigh, to the nearest 0.0001 g, about 0.5 g of PTAstandard in a 25 mL beaker,
34、 add 3 mL of ammonium hydroxidesolution and 7 mL water, to dissolve PTA completely. Adjustthe pH value of the solution to 67 by using the phosphoricacid solution. Then accurately transfer the resulting solution toa 50 mL volumetric flask, and dilute with water to the mark.When operating conditions a
35、re steady, inject 20 L of thecalibration standard solution into chromatograph for analysis.Record chromatogram and the peak area values for 4-CBA andp-TOL respectively with the data system.NOTE 4Care must be taken to ensure a quantitative transfer of thesolution from the beaker, and also any materia
36、l that is removed by the pHprobe, into the 50 mL volumetric flask. It is recommended that acalibration standard be run after every ten samples to check the stabilityof the chromatograph system.11. Procedure11.1 Weigh, to the nearest 0.0001 g, about 0.5 g PTAsample, repeat the remaining steps in 10.1
37、, and record peakarea values of 4-CBA and p-TOL respectively. After eachanalysis, rinse the column with mobile phase until the baselineis stabilized for the next run. The representative chromato-grams of a PTA sample is shown in Fig. 1.12. Calculation12.1 Calculate the concentration of 4-CBA or p-TO
38、L inmg/kg, using the following equation:X 5ms A Csm As(1)where:X = concentration of 4-CBA or p-TOL in the PTA sample,mg/kg,A = peak area of 4-CBA or p-TOL in the PTA sample,m = weight of the PTA sample, g,As= peak area of 4-CBA or p-TOL in the PTA standard,Cs= concentration of 4-CBA or p-TOL in the
39、PTA standard,mg/kg,ms= weight of the PTA standard, g.13. Report13.1 Report the value of 4-CBAor p-TOL content in mg/kg,to the nearest 1.0 mg/kg.13.2 Report the following information in the report:13.2.1 The complete identification of the sample tested.13.2.2 Any deviation from the procedure specifie
40、d (forexample, detailed description of column and operating condi-tions).13.2.3 Results of the test.13.2.4 Any abnormal situations observed during the test.14. Precision and Bias714.1 The precision of this test method is based on anintralaboratory study of Test Method D7883 conducted in7Supporting d
41、ata have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1047. ContactASTM CustomerService at serviceastm.org.FIG. 1 Chromatogram of a PTA Sample (weak anion exchange HPLC)14-CBA, 2p-TOL, 3PTAD7883 1332012. One laboratory tested one PTA sample an
42、d one qualifiedterephthalic acid (QTA) sample for 4-CBA and p-TOL. 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 followed for
43、 the design andanalysis of the repeatability data; the details are given inResearch Report RR:D16-1047.14.1.1 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 representing
44、 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.14.1.1.1 Repeatability limits are listed in Table 2.14.1.2 BiasAt the time of the study, the test specimenschosen for analysis were
45、not accepted reference materialssuitable for determining the bias for the test method, thereforeno statement on bias is being made.15. Quality Guidelines15.1 Laboratories shall have a quality control system inplace.15.1.1 Confirm the performance of the test instrument ortest method by analyzing a qu
46、ality control sample followingthe guidelines of standard statistical quality control practices.15.1.2 A quality control sample is a stable material isolatedfrom the production process and representative of the samplebeing analyzed.15.1.3 When QA/QC protocols are already established inthe testing fac
47、ility, these protocols are acceptable when theyconfirm the validity of test results.15.1.4 When there are no QA/QC protocols established inthe testing facility, use the guidelines described in GuideD6809 or similar statistical quality control practices.16. Keywords16.1 purified terephthalic acid; 4-
48、Carboxybenzaldehyde;p-Toluic acid; high performance liquid chromatograph; weakanion exchange HPLCANNEX(Mandatory Information)A1. RECOMMENDED PROCEDURE FOR CALIBRATION OF PTA SAMPLEINTRODUCTIONWhen a PTA standard with known amounts of 4-CBA and p-TOL is not available, a PTA samplewith granularity of
49、80 to 160 m, containing 4-CBA and p-TOL at concentrations of 10 to 25 mg/kgand 100 to 200 mg/kg, respectively, may be analyzed to determine the concentrations of 4-CBA andp-TOL by using the following standard addition method. This PTA sample with calibratedconcentrations of 4-CBA and p-TOL can be used as the PTA standard for sample analysis.A1.1 Reagents and MaterialsA1.1.1 4-CBAPurity 98.0 %.A1.1.2 P-TOLPurity 98.0 %.A1.2 Calibration SolutionsA1.2.1 Calibration Standard 4-CBA (10 g/mL)Weigh, tothe nearest 0.0001 g,
