1、Designation: E 298 08Standard Test Methods forAssay of Organic Peroxides1This standard is issued under the fixed designation E 298; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses
2、indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the assay of organic peroxides.Two procedures are given, depending upon the ease of reduc-tion:1.1.1 Sodium Iodide, Room Temperatu
3、re Test Method, fororganic peroxides easy to reduce, and1.1.2 Sodium Iodide, 60C Test Method, for organic perox-ides that are moderately stable.1.2 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.3 This standard does not purport
4、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.1.4 Review the current material safety data sheets
5、 (MSDS)for detailed information concerning toxicity, first-aid proce-dures, and safety precautions.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemic
6、alsE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis3. Significance and Use3.1 Organic peroxides are widely used as chemical interme-diates, catalysts, and initiators. These test methods provideprocedures for assaying organic peroxid
7、es to determine if theyare suitable for their intended use.4. Purity of Reagents4.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the Ame
8、rican Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.4.2 Unless otherwise indicated, references to water shall beun
9、derstood to mean Type II or Type III reagent water conform-ing to Specification D 1193.SODIUM IODIDE, ROOM TEMPERATURE TESTMETHOD5. Scope5.1 This test method covers the assay of organic peroxidesthat are easily reduced, such as hydroperoxides and diacylperoxides. Dialkyl peroxides do not react, whil
10、e peresters andbridge-type peroxides like ascaridole react slowly and incom-pletely.5.2 Specific peroxides that can be analyzed by this proce-dure include the following:5.2.1 Diacyl PeroxidesBenzoyl 2,4-dichlorobenzoyl,p-chlorobenzoyl, lauroyl, acetyl, and decanoyl peroxides.5.2.2 Dibasic Acid Perox
11、ideSuccinic acid peroxide.5.2.3 Ketone PeroxidesCyclohexanone peroxide and me-thyl ethyl ketone peroxide.5.2.4 Alkyl Hydroperoxidestert-Butylhydroperoxide and2,5-dimethylhexane-2,5-dihydroperoxide.6. Summary of Test Method6.1 A sample is dissolved in a mixture of methylenechloride and acetic acid. A
12、 saturated solution of sodium iodideis added and the mixture is allowed to react in the dark at roomtemperature for 15 min. The liberated iodine is then titratedwith standard sodium thiosulfate solution.1These test methods are under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty C
13、hemicals and are the direct responsibility of Subcommit-tee E15.01 on General Standards.Current edition approved April 1, 2008. Published May 2008. Originallyapproved in 1966. Last previous edition approved in 2001 as E 298 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orc
14、ontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testin
15、g 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.1*A Summary of Changes section appears at the end
16、of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Interferences7.1 Conjugated diolefins interfere by absorbing iodine.8. Apparatus8.1 Iodine Flasks, 250-mL, with stoppers.NOTE 1All glassware should be thoroughly clea
17、ned before use.9. Reagents9.1 Acetic Acid, Glacial.9.2 Carbon Dioxide, cylinder.9.3 Methylene Chloride.9.4 Sodium Iodide, Saturated SolutionPrepare a saturatedsolution of sodium iodide (NaI) in de-aerated water. Thissolution should be prepared just prior to use and kept in anamber bottle.9.5 Sodium
18、Thiosulfate, Standard Solution (0.1 meq/mL(N)Prepare and standardize a 0.1 meq/mL(N) solution ofsodium thiosulfate (Na2S2O3) in accordance with the appropri-ate sections of Practice E 200.9.6 Starch Indicator Solution (10 g/L), Prepare as describedin the appropriate sections of Practice E 200.9.7 Wa
19、ter, De-aeratedPass carbon dioxide (CO2) throughdistilled water for several minutes prior to use.10. Procedure10.1 Add 20 mL of acetic acid to a 250-mL iodine flask andsparge with a rapid flow of CO2for 2 min. Stopper the flaskand reserve for the sample.10.2 Accurately weigh a sample containing 3 to
20、 4 meq ofactive oxygen to the nearest 0.1 mg and transfer to the flask.Volatile liquid peroxides may be diluted to a known volumewith acetic acid and aliquots taken for analysis.NOTE 2The approximate weight of the sample to be used in theanalysis may be calculated as follows:Sample weight, g 5 3.5M/
21、2C 3 1000 (1)where:M = molecular weight of the compound, andC = number of peroxide groups in the molecule.10.3 Add 10 mL of methylene chloride and restopper. Swirlbriefly to dissolve the sample.10.4 Add 5 mL of freshly prepared saturated NaI solution.Restopper and swirl. Place a few millilitres of w
22、ater in the wellof the flask and allow to stand in the dark at room temperaturefor 15 min.10.5 Add 50 mL of de-aerated water and titrate with 0.1meq/mL (N)Na2S2O3solution until the solution is a pale strawcolor. Add 1 to 2 mL of starch solution and continue thetitration to the sharp disappearance of
23、 the blue color. Recordthe number of millilitres required for titration.10.6 Subtract the number of millilitres required for titrationof a blank carried through the entire procedure and calculatethe assay value of the sample.NOTE 3The blank titration should normally require 0.05 mL or less of0.1 meq
24、/mL (N)Na2S2O3solution. The results should be discarded andthe analysis repeated if high blank values are obtained.11. Calculation11.1 Calculate the assay as follows:Assay, as percent compound 5 A 2 B! 3 N 3 M 3 100/W 3 2C3 1000 (2)where:A =mLofNa2S2O3solution required for titration of thesample,B =
25、mLofNa2S2O3solution required for titration of theblank,N = meq/mL (N) of the Na2S2O3solution,C = number of peroxide groups in the molecule,M = molecular weight of the compound, andW = grams of sample used.11.2 Calculate the percent active oxygen in the compoundas follows:Active oxygen, % 5 A 2 B! 3
26、N 3 0.0083 100/W (3)11.3 If required, the percent active oxygen can be con-verted to a specific peroxide using the appropriate conversionfactor.Peroxide X,%5 % Active Oxygen in Peroxide X 3 F (4)where:F = conversion factor for Compound X.11.3.1 Conversion Factors for some common peroxides areas foll
27、ows:Cumene Hydroperoxide = 9.5125Benzoyl Peroxide = 15.140t-Butyl Hydroperoxide = 5.6328Lauroyl Peroxide = 24.91512. Report12.1 Report the assay value of the compound to the nearest0.01%.13. Precision and Bias413.1 The following criteria shall be used for judging theacceptability of results (Note 4)
28、:13.1.1 Repeatability (Single Analyst)The standard devia-tion for a single determination has been estimated to be0.047 % absolute at 36 df. The 95 % limit for the differencebetween two such determinations is 0.13 % absolute.13.1.2 Laboratory Precision (Within-Laboratory, Between-Days Variability)The
29、 standard deviation of results (each theaverage of duplicates) obtained by the same analyst ondifferent days, has been estimated to be 0.010 % absolute at 18df. The 95 % limit for the difference between two suchaverages is 0.028 % absolute.13.1.3 Reproducibility (Multilaboratory)The standard de-viat
30、ion of results (each the average of duplicates) obtained byanalysts in different laboratories has been estimated to be0.035 % absolute at 5 df. The 95 % limit for the differencebetween two such averages is 0.10 % absolute.NOTE 4These precision estimates are based on an interlaboratorystudy in which
31、3 samples were analyzed. One analyst in each of 6laboratories performed duplicate determinations and repeated them on a4Supporting data are available from ASTM Headquarters. Request RR: E15-1001.E298082second day, for a total of 72 determinations. Practice E 180 was used indeveloping these statement
32、s.13.2 BiasThe bias of this test method has not beendetermined due to the lack of suitable reference materials ormethodology.SODIUM IODIDE, 60C TEST METHOD14. Scope14.1 This test method covers the assay of organic peroxidesthat are moderately stable, such as peresters, di-acyl peroxides,and n-alkyl
33、peroxides. These peroxides react slowly withsodium iodide at room temperature, but do not require the useof hydroiodic acid.14.2 Specific peroxides that can be analyzed by this proce-dure include the following: t-butyl peracetate, t-butyl peroxy-isobutyrate, di-t-butyl diperphthalate, t-butyl perben
34、zoate, and2,2-bis(t-butylperoxy) butane.15. Summary of Test Method15.1 A sample is dissolved in glacial acetic acid. Saturatedsodium iodide solution is then added and the mixture isallowed to react for1hat60C. The liberated iodine is titratedwith standard sodium thiosulfate solution.16. Interference
35、s16.1 Conjugated diolefins interfere under the conditions ofanalysis by absorbing iodine.17. Apparatus17.1 Iodine Flasks, 250-mL with stopper (Note 1).17.2 Water Bath, maintained at 60 6 1C.18. Reagents18.1 Acetic Acid, Glacial.18.2 Carbon Dioxide, cylinder.18.3 Sodium Iodide, Saturated SolutionSee
36、9.4.18.4 Sodium Thiosulfate, Standard Solution (0.1 meq/mL(N)See 9.5.18.5 Starch Indicator SolutionSee 9.6.18.6 Water, De-aeratedSee 9.7.19. Procedure19.1 Add 20 mL of acetic acid to a 250-mL iodine flask andsparge with a rapid flow of carbon dioxide (CO2) for 2 min.Stopper the flask and reserve for
37、 the sample.19.2 Accurately weigh a sample containing 3 to 4 meq ofactive oxygen to the nearest 0.1 mg and transfer to the flask(Note 2).19.3 Add 5 mL of freshly prepared saturated NaI solution(Note 5). Restopper tightly and swirl. Place a few millilitres ofwater in the well of the flask and allow t
38、he flask to standpartially submerged in a water bath maintained at 60C for 1 h.NOTE 5Some peroxides may require the addition of a small amountof hydrochloric acid (HCl) to react completely in a reasonable time. In thiscase 1 mL of concentrated HCl shall be added to the solution just beforeit is plac
39、ed in the water bath.19.4 Remove the flask from the bath and cool to roomtemperature.19.5 Add 60 mL of de-aerated water and titrate with 0.1meq/mL (N)Na2S2O3solution until the solution is a pale strawcolor. Add 1 to 2 mL of starch solution and continue thetitration to the sharp disappearance of the
40、blue color. Recordthe number of millilitres required for titration.19.6 Subtract the number of millilitres required for titrationof a blank carried through the entire procedure and calculatethe assay value of the sample.NOTE 6The blank titration should normally require about 0.10 mL of0.1 meq/mL (N)
41、Na2S2O3solution. The results should be discarded andthe analysis repeated if high blank values are obtained.20. Calculation20.1 Calculate the assay as follows:Assay, as percent compound5 A 2 B! 3 N 3 M 3 100/W 3 2C3 1000 (5)where:A =mLofNa2S2O3solution required for titration of thesample,B =mLofNa2S
42、2O3solution required for titration of theblank,N = meq/mL (N) of the Na2S2O3solution,C = number of peroxide groups in the molecule,M = molecular weight of the compound, andW = grams of sample used.20.2 Calculate the percent of active oxygen in the com-pound as follows:Active oxygen, % 5 A 2 B! 3 N 3
43、 0.008/W 3 100 (6)20.3 If required, the percent active oxygen can be convertedto a specific peroxide using the appropriate conversion factor.See 11.3.21. Report21.1 Report the assay value of the compound to the nearest0.01 %.22. Precision and Bias422.1 The following criteria should be used in judgin
44、g theacceptability of results (Note 7):22.1.1 Repeatability (Single Analyst)The standard devia-tion for a single determination has been estimated to be0.080 % absolute at 24 df. The 95 % limit for the differencebetween two such determinations is 0.23 % absolute.22.1.2 Laboratory Precision (Within-La
45、boratory, Between-Days Variability)The standard deviation of results (eachthe average of duplicates) obtained by the same analyst ondifferent days, has been estimated to be 0.055 % absolute at 12df. The 95 % limit for the difference between two suchaverages is 0.15 % absolute.22.1.3 Reproducibility
46、(Multilaboratory)The standard de-viation of results (each the average of duplicates) obtained byanalysts in different laboratories has been estimated to be0.126 % absolute at 5 df. The 95 % limit for the differencebetween two such averages is 0.35 % absolute.E298083NOTE 7These precision estimates ar
47、e based on an interlaboratorystudy conducted in which 2 samples were analyzed. One analyst in eachof 6 laboratories performed duplicate determinations and repeated them ona second day, for a total of 48 determinations. Practice E 180 was used indeveloping these statements.22.2 BiasThe bias of this t
48、est method has not beendetermined due to the lack of suitable reference materials ormethodology.23. Keywords23.1 assay; iodometric; organic peroxide; peroxidesSUMMARY OF CHANGESSubcommittee E15.01 has identified the location of selected changes to this standard since the last issue(E 298-01) that ma
49、y impact the use of this standard.(1) Updated units of measure to comply with the InternationalSystem of Units (SI).(2) Added numbered paragraph in Scope stating that the SIunits are to be considered standard.(3) Deleted (Formerly called Repeatability) from the Precisionsections.(4) Added Summary of Changes section.ASTM 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 s
