1、Designation: E 1616 94 (Reapproved 2002)e1Standard Test Method forAnalysis of Acetic Anhydride Using Gas Chromatography1This standard is issued under the fixed designation E 1616; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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.e1NOTEThe heading in the last column of Table 4 was editorially changed in May 2002.1. Scope1.1 This test method describ
3、es the determination of assayand impurities in acetic anhydride by gas chromatography. Theacetic anhydride should be at least 95 % pure.1.2 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 es
4、tablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardsstatements see Section 9.2. Referenced Documents2.1 ASTM Standards:E 355 Practice for Gas Chromatography Terms and Rela-tionships23. Terminology3.1 Definition
5、sFor definitions of terms used in this testmethod, see Practice E 355.4. Summary of Test Method4.1 The sample is injected onto a gas chromatographiccolumn. The components are separated as they pass throughthe column with helium carrier gas, their presence in theeffluent is detected by a flame ioniza
6、tion detector, and recordedas a chromatogram. The concentrations of sample componentsare calculated as weight percentages using area normalization.5. Significance and Use5.1 This test method provides for the determination of assayand impurities in acetic anhydride. Acetic anhydride is used asan inte
7、rmediate in many chemical processes. Its relativeconcentration affects the efficiency of these processes. This testmethod provides a test procedure for assay and impurityspecification acceptance as well as manufacturing control.6. Interferences6.1 This test method describes the chromatographic separ
8、a-tion of possible impurities in acetic anhydride. Other impuritiescould coelute with the known components and cause aninterference. Therefore, an efficient gas chromatographic col-umn in good condition should be used in order to ensure thenecessary chromatographic separations and proper peak shapes
9、so that good quantitative data may be obtained.6.2 This analysis is based upon the assumption that allcomponents are eluted from the gas chromatographic column.7. Apparatus7.1 Gas ChromatographAny gas chromatographequipped with a flame ionization detector and a split injectionsystem for use with cap
10、illary columns that can be operated atthe conditions given in Table 1.7.2 ColumnThe column must give satisfactory resolutionand proper peak shapes for the components listed in Fig. 1.Table 1 contains a description of a column that has been foundsatisfactory.7.3 Recorder/IntegratorElectronic integrat
11、ion is recom-mended for this analysis.7.4 Syringe, 10-L capacity.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemic
12、al Society wheresuch specifications are available.3Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.2 High-Purity Acetic Anhydride (99.8 % or GreaterPurity)It is important t
13、hat the acetic anhydride used toprepare calibration standards be as pure as possible. If the1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicalsand is the direct responsibility of SubcommitteeE15.02 on Product Standards.Current edition approved June
14、15, 1994. Published August 1994.2Annual Book of ASTM Standards, Vol 03.06.3Reagent 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 Laboratory
15、Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.acetic anhydride specified b
16、y this test method is not suitable forstandard preparation, it should be redistilled prior to use oranother source found. Note that American Chemical Societyreagent grade acetic anhydride may not be sufficiently pure forthis procedure. Its titration assay will include other anhydridespresent as well
17、 as acetic anhydride.8.3 Carrier GasChromatographic-grade helium.8.4 Detector Gas, airBreathing quality grade.8.5 Detector Gas, hydrogen99.95 % grade.8.6 Pure compounds for calibration could include aceticacid, ethylidene diacetate, mesityl oxide, and acetonitrile. Thepurity of all reagents should b
18、e 99 % or greater. If the purity isless than 99 %, the concentration and identification of impuri-ties must be known so that the composition of the standard canbe adjusted for the presence of the impurities.8.7 Propionic anhydride and propionic acid are not includedin the calibration of this test me
19、thod. The propionic anhydrideor propionic acid would react over time to form the mixedanhydride, acetic-propionic anhydride.9. Hazards9.1 Consult current Occupational Safety and Health Admin-istration (OSHA) regulations and suppliers Material SafetyData Sheets for all materials used in this test met
20、hod.9.2 Acetic anhydride is a corrosive, both as a liquid and avapor. It is severely damaging to the eyes and skin. It can causedelayed burns if not removed immediately.9.3 Acetic anhydride is combustible. Its vapor is flammablein the range from 2.7 to 10.3 volume % in air. Possible ignitionsources
21、shall be avoided.9.4 WarningAcetic anhydride reacts violently with wa-ter. Handle and dispose of all samples so as to minimize anycontact with water.10. Preparation of Apparatus10.1 Follow the manufacturers instructions for mountingand conditioning the column into the chromatograph andadjusting the
22、instrument to the conditions described in Table 1.Allow sufficient time for the equipment to reach equilibrium.11. Calibration11.1 Prior to standard preparation, the acetic anhydride usedto prepare the calibration standard must be analyzed todetermine purity. It is difficult to obtain acetic anhydri
23、de that isfree of detectable levels of acetic acid; however, with purifi-cation, the amount of acetic acid in the anhydride can beminimized. To perform this blank run, inject 1.0 L of theacetic anhydride onto the chromatographic column. Analyzethe blank in accordance with the conditions specified in
24、 Table1. If any impurity is present at a concentration of greater than0.05 % by area, it is advisable to purify the acetic anhydrideprior to use.11.1.1 The most likely impurity to remain in acetic anhy-dride, even after purification, is acetic acid. Retain the resultsof this blank run for later use
25、in the determination of responsefactors for the calibrated components noted in this test method.11.1.2 Relative retention times for possible components aregiven in Table 2 and a chromatogram is shown in Fig. 1.11.2 A calibration standard should be prepared containing atleast acetic acid and acetic a
26、nhydride. Other components maybe calibrated as needed. Approximate amounts are given inTable 3.11.2.1 During standard preparation, the exact amounts of allcomponents shall be recorded.11.3 After analyzing the acetic anhydride blank, analyze thecalibration standard described in 11.2. Inject 1.0 L of
27、thestandard onto the chromatographic column. Analyze the stan-dard in accordance with the conditions specified in Table 1.11.4 Calculate response factors to four decimal places for allcomponents relative to acetic anhydride using the followingequation:Fx5Wx!Rs!Ws!Rx2 Rb!(1)where:Fx= response factor
28、for Compound X relative to aceticanhydride,Wx= weight of Compound X, g,Rs= peak response of acetic anhydride,Ws= weight of acetic anhydride, g,Rx= peak resonse of Compound X in the standard, andRb= peak resonse of Compound X in the blank.The only components for which response factors are deter-mined
29、 are acetic acid, ethylidene diacetate, acetonitrile, andmesityl oxide. All other components are assigned relativeresponse factors of 1.0000.11.5 It is advisable that the determination of responsefactors be made on the basis of duplicate analyses.11.6 Response factors should be checked after any per
30、cep-tible change in column or instrument performance.12. Procedure12.1 Inject 1.0 L of sample onto the chromatographiccolumn.12.2 Record and integrate the chromatogram using theconditions given in Table 1.12.3 A typical chromatogram of acetic anhydride spikedTABLE 1 Instrument Conditions for Acetic
31、Anhydride AnalysisColumn:Tubing fused silicaStationary phase cross-linked methyl siliconeFilm thickness, m 0.52Length, m 50Inside diameter, mm 0.32Temperature, C:Inlet 250Detector 250Column 80Carrier Gas:HeliumInjection System:Split injection; 100:1 split ratioDetector:Flame ionizationDetector Gases
32、, mL/min:Hydrogen 30Air 350Helium, makeup 30E 16162with known impurities is shown in Fig. 1.13. Calculation13.1 Calculate the concentrations of sample componentsusing the following equation:Cx,% 5Fx!Rx!100!( Rx!Fx!(2)where:Cx= Compound X, weight %,Rx= peak response of Compound X,Fx= relative respons
33、e factor of Compound X deter-mined in 11.4, and( RxFx= sum of the individual component peak responses(Rx) multiplied by their relative response factors(Fx).14. Report14.1 Report the following information:14.1.1 Individual components to the nearest 0.01 weight %.14.1.2 For concentrations of impuritie
34、s less than 0.01weight %, report as 0.01 weight %.14.1.3 Acetic anhydride content to the nearest 0.01 weight%.15. Precision and Bias15.1 Precision:15.1.1 The precision data given in Table 4 were performedin one laboratory. An interlaboratory study to determinerepeatability and reproducibility has no
35、t been completed.15.1.2 The precision of this test method on samples ofapproximately 95 % acetic anhydride was determined. Twentysamples of acetic anhydride were split into two aliquots. These40 samples were randomly analyzed by any of 16 analystsusing one gas chromatograph and a chromatographic dat
36、asystem over a two week period in one laboratory. These resultsare given for Sample 1 in Table 4.15.1.3 The precision of this test method on samples ofgreater than 99 % acetic anhydride was determined. ThirtyFIG. 1 Chromatogram of Acetic Anhydride Spiked with Possible ImpuritiesTABLE 2 Relative Rete
37、ntion Times for Possible Impurities inAcetic AnhydrideComponent Relative Retention TimeKetene 0.62Acetonitrile 0.67Acetic acid 0.75Propionic acid 0.91Acetic anhydride 1.00Mesityl oxide 1.25Acetic propionic anhydride 1.29Ethylidene diacetate 1.90Propionic anhydride 1.98TABLE 3 Calibration Standard Co
38、mposition for Acetic AnhydrideAnalysisComponent Weight%Acetic acid 0.50 to 1.5Acetic anhydride 98.0 to 99.5Acetonitrile 0.01 to 0.05Ethylidene diacetate 0.01 to 0.05Mesityl oxide 0.01 to 0.05TABLE 4 Precision DataComponentAverageConcentration, %StandardDeviation95 %Limits, %Sample 1Acetic acid 4.24
39、0.039 0.11Acetic anhydride 95.24 0.043 0.12Acetic-propionic anhydride .20 0.004 0.01Ethylidene diacetate 0.07 0.003 0.01Sample 2Acetic anhydride 99.82 0.032 0.09E 16163samples of acetic anhydride were split into two aliquots. These60 samples were randomly analyzed by any of 20 analystsusing one gas
40、chromatograph and a chromatographic datasystem over a 20 day period in one laboratory. The results aregiven for Sample 2 in Table 4.15.2 BiasSince there is no accepted reference materialsuitable for determining the bias for this test method, bias hasnot been determined.16. Keywords16.1 acetic anhydr
41、ide; anhydride; gas chromatographyASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risko
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