1、Designation: D7884 13Standard Test Method forDetermination of 4-Carboxybenzaldehyde and p-Toluic Acidin Purified Terephthalic Acid by Reverse Phase HighPerformance Liquid Chromatography1This standard is issued under the fixed designation D7884; the number immediately following the designation indica
2、tes 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 method covers the determination of
3、 the4-Carboxybenzaldehyde (4-CBA) and p-Toluic acid (p-TOL)in purified terephthalic acid (PTA) by reverse phase highperformance liquid chromatography (HPLC). This method isapplicable for 4-CBAfrom 2 to 500 mg/kg and for p-TOL from10 to 500 mg/kg, respectively.1.2 In determining the conformance of th
4、e 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 standard does not pu
5、rport 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 Standards:2D
6、1193 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 Conformance with Speci
7、ficationsE177 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:3EN ISO 8213 Chemical products for indust
8、rial useSampling techniquesSolid chemical products in theform of particles varying from powders to coarse lumps2.3 Other Document:4OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.12003. Summary of Test Method3.1 Reverse Phase HPLC MethodPTAsample is dissolvedin ammonium hydroxide solution, and
9、 a fixed volume of thissolution is injected into a high performance liquid chromato-graph equipped with a UV detector. A C18 chemically bondedcolumn is used to separate the impurities 4-CBA and p-TOLfrom PTA. The external standard calibration is used forquantification.4. Significance and Use4.1 The
10、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 imparts color-ation to the polymer due to thermal instability.4.2 Determining the amount of 4-CBA and p-TOL remain-ing from the manufacture of PTA is o
11、ften required. This testmethod is suitable for setting specifications and for use as aninternal quality control tool where these products are producedor are used.5. Apparatus5.1 High Performance Liquid Chromatograph (HPLC)any HPLC capable of pumping the mobile phase at flow rates1This test method is
12、 under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and 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/D7884-13.2For referenced ASTM standards, visit the AS
13、TM 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 American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 1003
14、6, http:/www.ansi.org.4Available from U.S. Government 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 States1b
15、etween 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 4-CBAand 10mg/kg p-TOL.5.2 Sample Injection Systemcapable of inject
16、ing 1 to 25L, using either partial or full loop mode, with a repeatabilityof 61%.5.3 DetectorVariable Wavelength Ultraviolet PhotometricDetector (VWD), Multi-wavelength Detector, or PhotometricDiode Array Detector (PDA)capable of operating at 240 and254 nm.5.4 Column Ovenany suitable HPLC column ove
17、n (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 A stainless steel HPLC column packed with an octa-decylsilane (C18) chemically bonded silica stationary phase issuitable. See Ta
18、ble 1 for recommended operating conditions.5.6.2 A C18 column with different dimensions (innerdiameter, length, particle size, etc.) that provides adequateresolution to quantitate 4-CBAand p-TOLin a PTAsample canalso be used.5.7 Analytical Balancereadable to 60.0001 g.5.8 Sample FilterA disposable s
19、yringe filter made ofcellulose acetate, with a pore size between 0.22 and 0.45 m,and is chemically inert to aqueous solutions, is recommendedfor the removal of particulate matter from the sample solution.6. Reagents and Materials6.1 Purity of ReagentsUnless otherwise indicated, it isintended that al
20、l reagents shall conform to the reagent gradespecification for analytical reagents of the American ChemicalSociety, where such specifications are available.5Other gradesmay be used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe
21、 performance or accuracy of the determination. 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 Hydroxide25 to 28 %.6.3 Phosphoric AcidHPLC grade.6.4 AcetonitrileHPLC grade. (WarningAcetoni
22、trile isflammable and hazardous in case of skin or eye contact,ingestion, or inhalation.)6.5 WaterHPLC grade.6.6 Ammonium Hydroxide Solutionammonium hydroxidemixed with water as 1:1 (V:V).6.7 PTA Standard for CalibrationA certified PTA calibra-tion standard with known amounts of 4-CBA and p-TOL isre
23、quired. If it is not commercially 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.6.8 Mobile Phase:6.8.1 0.06 % H3PO4Solution:Acetonitrile = 82:18Pipette 0.6 mL H3PO4into a 1
24、000 mL volumetric flask with900 mL of water and make up to the mark with water to give0.06 % H3PO4solution. Mix 820 mL of H3PO4solution and180 mL of acetonitrile. Methanol could be used as an alterna-tive to acetonitrile in the mobile phase.NOTE 2It is recommended to degas and filter the mobile phas
25、e beforeuse; 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
26、Specimens, and Test Units8.1 Use only representative samples obtained as describedin EN ISO 8213, unless otherwise specified.9. Preparation of Apparatus9.1 Set up the pump, sample injection system, column,oven, detector, and chromatography data system in accordancewith the manufacturers instructions
27、. Adjust the instrument tothe recommended conditions described in Table 1, allowingsufficient time for the equipment to reach equilibrium which isindicated by a stable horizontal baseline. For a new column, 4to 6 hours of equilibration time may be required.NOTE 3Separation between peaks of 4-CBA and
28、 PTA can beoptimized by carefully varying the aqueous-organic ratio and flow rate.NOTE 4It has been found for a reverse-phase HPLC, separationbetween 4-CBA and PTA can be improved by adding a certain amount oftrifluoroacetic acid (TFA) in acetonitrile water solution as a mobile phase.NOTE 5A gradien
29、t 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, add 3 mL of ammonium hydroxide5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For sugge
30、stions on the testing of reagents notlisted by the American Chemical Society, 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
31、ConditionsColumn C18Stationary phaseOctadecylsilane chemicallybonded silicaParticle size 5 mMaterial of column stainless steelLength of column 150 mmInner diameter 45 mmMobile phase0.06 % H3PO4solution:acetonitrile = 82:18Flow rate 1.0 mL/minUV detector254 nm for 4-CBA240 nm for p-TOLInjection amoun
32、t 20 LColumn temperature 40CD7884 132solution, and 7 mL water to dissolve PTA completely. Thenaccurately transfer the resulting solution to a 250 mL volumet-ric flask, and dilute with water to the mark. Inject 20 L of thecalibration standard solution into chromatograph for analysis.Record chromatogr
33、am and peak area values for 4-CBA andp-TOL respectively with data system.NOTE 6It is recommended that a calibration standard be run afterevery ten samples to check the stability of the chromatograph system.11. Procedure11.1 Weigh, to the nearest 0.0001 g, about 0.5 g of PTAsample, repeat the remaini
34、ng steps in 10.1, 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
35、of 4-CBA or p-TOL inmg/kg, using the following equation:X 5msACsmAs(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
36、p-TOL in the 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 proce
37、dure specified (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 Bias614.1 The precision of this test method is based on anintralaboratory study of Test Method D7884 conducted in
38、2012. One laboratory tested one PTA sample and 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 o
39、f thestandard. Practice E691 was followed for the design andanalysis of the repeatability data; the details are given inResearch Report RR:D16-1048.14.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for
40、 that material; “r”istheinterval representing 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
41、, 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.15. Quality Guidelines15.1 Laboratories shall have a quality control system inplace.6Supporting data have been filed at ASTM
42、 International Headquarters and maybe obtained by requesting Research Report RR:D16-1048. ContactASTM CustomerService at serviceastm.org.FIG. 1 Chromatogram of a PTA Sample (Reverse Phase HPLC)1PTA, 24-CBA, 3p-TOLD7884 13315.1.1 Confirm the performance of the test instrument ortest method by analyzi
43、ng a quality 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 test
44、ing facility, 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 a
45、cid; 4-Carboxybenzaldehyde;p-Toluic acid; high performance liquid chromatograph;reverse-phase HPLCANNEX(Mandatory Information)A1. RECOMMENDED PROCEDURE FOR CALIBRATION OF PTA SAMPLEWhen a PTA standard with known amounts of 4-CBA and p-TOL is not available, a PTA sample with granularity of 80 to 160
46、m, contain-ing 4-CBA and p-TOL at concentrations of 10 to 25 mg/kg and 100 to 200 mg/kg, respectively, may be analyzed to determine the concen-trations of 4-CBA and p-TOL by using the following standard addition method. This PTA sample with calibrated concentrations of 4-CBAand p-TOL can be used as
47、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, about 0.0250 g of 4-CBA in a 25 mLbeaker, add some water and a few drops of ammonium
48、hydroxide solution, and stir until 4-CBA is completely dis-solved. Adjust the pH value of the solution to 67 by usingphosphoric acid solution. Then accurately transfer the resultingsolution to a 50 mL volumetric flask and dilute with water tothe mark to give a 500 g/mL 4-CBA stock solution. Thendilu
49、te with water 50 times to 10 g/mL.NOTE A1.1Care must be taken to ensure a quantitative transfer of thesolution from the beaker, and also any material that is removed by the pHprobe, into the 50 mL volumetric flask.A1.2.2 Calibration Standard p-TOL (80 g/mL)Weigh, tothe nearest 0.0001 g, about 0.0200 g of p-TOL, following stepsin A1.2.1 to give a 400 g/mL p-TOL stock solution. Thendilute with water five times to 80 g/mL.A1.2.3 PTA Spiked SolutionsAccurately weigh 0.500 60.001 g of PTA in five 25 mL beakers each and follow s
