1、Designation: E 1228 94 (Reapproved 2003)e1Standard Test Method forAssay of Peroxy EstersCatalyzed Iodometric Procedure1This standard is issued under the fixed designation E 1228; 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.e1NOTE“Between Days Variability” was dropped from the title of 13.1.2 editorially in October 2003.1. Scope1.1 This test m
3、ethod covers the assay of organic peroxidesof the peroxy ester type.NOTE 1Other test methods for the assay of organic peroxides aregiven in Test Methods E 298, E 475, and E 755.1.2 Review the current material safety data sheets (MSDS)for detailed information concerning toxicity, first aid proce-dure
4、s, and safety precautions.1.3 The values stated in SI units are to be regarded as thestandard.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 and health pra
5、ctices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstatements are given in Section 9.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of I
6、ndustrial ChemicalsE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysisE 298 Test Methods for Assay of Organic PeroxidesE 475 Test Method for Assay of Di-tert-Butyl Peroxide byGas Chromatographic AnalysisE 755 Test Method for Assay of D
7、icumyl Peroxide byLiquid Chromatography3. Terminology3.1 Definitions:3.1.1 active oxygenthe oxidizing power present in organicperoxides expressed as oxygen (equivalent weight 8.00).4. Summary of Test Method4.1 A sample is dissolved in a mixture of isopropyl alcohol,acetic acid, and cupric chloride.
8、A solution of potassium iodideis added and the mixture is briefly heated, then allowed to reactin the dark at room temperature for 30 min. The cupric ioncatalyzes the reduction of the peroxide and the liberated iodineis titrated with standard sodium thiosulfate solution.5. Significance and Use5.1 Pe
9、roxy esters are widely used as chemical intermedi-ates, catalysts, and initiators. This test method provides aprocedure for assaying peroxy esters to determine if they aresuitable for their intended use.6. Interferences6.1 Conjugated diolefins interfere under the conditions ofanalysis by absorbing i
10、odine.7. Apparatus7.1 Iodine Flasks, 250-mL capacity, with stoppers.NOTE 2All glassware should be cleaned thoroughly with dichromatecleaning solution before use.7.2 Beakers, 1-mL capacity, glass or PTFE.7.3 Buret, 50-mL capacity, graduated in 0.1-mL subdivi-sions.7.4 Water Bath, maintained at 60C.8.
11、 Reagents8.1 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 Com-mittee on Analytical Reagents of the American ChemicalSociety, where such specifications are available.3Other g
12、rades1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and is the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved Dec. 15, 1994. Published February 1995. Originallypublished as E 1228 88. Last previous edi
13、tion E 1228 88.2For 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. .3Reagent Chemicals, American Chemical Societ
14、y 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, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial
15、 Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.may be used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe accuracy of th
16、e determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean Type II or III reagentwater conforming to Specification D 1193.8.3 Acetic Acid, glacial.8.4 Isopropyl Alcohol.8.5 Hydrochloric Acid, (1:100)Dilute 1.0 mL of concen-trated hydrochloric acid (
17、HCl) to 100 mL with water.8.6 Cupric Chloride Solution, 1 %Dilute 1.0 g of anhy-drous cupric chloride (CuCl2) to 100 mL with water. Add 1.0mL of 1:100 HCl and mix. The solution should be clear.8.7 Potassium Iodide Solution, 50 %Dissolve 25 g ofpotassium iodide (KI) in 25 mL of de-aerated water. This
18、reagent should be freshly prepared just prior to use.8.8 Sodium Thiosulfate Standard Solution, (0.1 N)Prepare and standardize in accordance with the appropriatesections of Practice E 200.8.9 Nitrogen Gas, oxygen-free.9. Hazards9.1 Organic peroxides are strong oxidizing agents andpresent potential fi
19、re and explosion hazards. Avoid contact withreducing agents and sources of heat, sparks, or open flames.Reactivity varies widely and some compounds may explodewhen shocked. Organic peroxides are irritating to the skin,eyes, and mucous membranes. Avoid bodily contact and handleonly in a well-ventilat
20、ed area.10. Procedure10.1 Add 50 mL of isopropyl alcohol and 15 mL of aceticacid to a 250-mL iodine flask. A graduate can be used for theseadditions.10.2 Pipet 1.00 mL of 1 % cupric chloride solution into theflask.NOTE 3Caution: The quantity of the cupric chloride catalyst solutionmust be carefully
21、measured in order to obtain reproducible results as thereagent also reacts with iodide to liberate iodine according to thefollowing Eq 1:2Cu111 4I2 2 CuI 1 I2(1)The blank titration should be approximately 1.0 mL. Theresults should be discarded and the analysis repeated if asignificantly higher blank
22、 value is obtained.10.3 Sparge the solution with a rapid flow of nitrogen for 2min, then stopper the flask and reserve.10.4 Accurately weigh a sample containing 3 to 4 meq ofactive oxygen in a 1-mL beaker. Transfer the beaker containingthe sample to the prepared flask and immediately restopper andmi
23、x. The approximate sample weight may be calculated asfollows:Sample weight, g 53.5 M2C3 1000(2)where:M = molecular weight of compound, andC = number of peroxide groups in the molecule.NOTE 4Volatile liquid peroxides may be diluted to a known volumewith isopropyl alcohol and aliquots taken for analys
24、is.10.5 While maintaining a flow of nitrogen over the solution,add 5 mL (graduate) of freshly prepared 50 % KI solution, andthen immediately restopper and swirl to mix.10.6 Place the flask in a water bath maintained at 60C for20 s while gently swirling. The level of water in the bath shouldbe above
25、the level of solution in the flask.NOTE 5The reaction is temperature sensitive. If the temperature of thesolution is above 25C, a 30-min reaction time is generally sufficient formost peresters. If the temperature of the solution is less than 25C, alonger reaction period may be required. By preheatin
26、g the solution for 20s at 60C, the solution temperature is high enough to obtain completereaction in 30 min with minor variation in the ambient laboratorytemperature.10.7 Remove the flask from the bath and allow to stand in adark location at room temperature for 30 min.10.8 Add 50-mL of de-aerated w
27、ater and titrate the solutionwith 0.1 N Na2S2O3solution to the colorless end point. Recordthe number of milliliters required for the sample titration.10.9 Subtract the number of milliliters required for titrationof a blank carried simultaneously through the entire procedureand calculate the assay va
28、lue of the sample. (See Note 3.)11. Calculation11.1 Calculate the assay as follows:assay, as % compound5 A 2 B! 3 N 3 M 3 100#/W 3 2C 3 1000!(3)where:A =Na2S2O3solution required for titration of the sample,mL,B =Na2S2O3solution required for titration of the blank,mL,N = normality of the Na2S2O3solut
29、ion,C = number of peroxide groups in the molecule,M = molecular weight of the ground, andW = sample used, g.11.2 Calculate the percent of active oxygen in the com-pound as follows:active oxygen, % 5A 2 B! 3 N 3 0.008# 3 100W(4)NOTE 6This assay is based on the determination of active oxygenunder spec
30、ified conditions. If other organic peroxides are present asimpurities and release equivalent amounts of active oxygen under thesame conditions, their concentrations must be determined by appropriateHPLC or GC procedures and the results corrected accordingly.12. Report12.1 Report the assay value of t
31、he compound to the nearest0.1 %.13. Precision and Bias13.1 PrecisionThe following criteria should be used forjudging the acceptability of results: (see Note 7).13.1.1 Repeatability (Single Analyst)The standard devia-tion for a single determination has been estimated to be0.135 % at 14 DF. The 95 % l
32、imit for the difference betweentwo such runs is 0.4 %.E 1228 94 (2003)e1213.1.2 Laboratory PrecisionThe standard deviation ofresults (each the average of duplicates), obtained by the sameanalyst on different days, has been estimated to be 0.141 %absolute at 6 DF. The 95 % limit for the difference be
33、tween twosuch averages is 0.4 % absolute.13.1.3 Reproducibility (Multilaboratory)The standard de-viation of results (each the average of duplicates), obtained byanalysts in different laboratories, has been estimated to be0.236 % absolute at 3 DF. The 95 % limit for the differencebetween two such ave
34、rages is 0.7 %.13.2 BiasThe bias of this test method cannot be deter-mined due to the unavailability of suitable reference materials.NOTE 7The above precision estimates are based upon an interlabo-ratory study performed in 1987 on samples of t-butyl perbenzoate andt-butyl peracetate with manufacture
35、rs assays of 98.3 % and 51.0 %,respectively. One analyst in each of four laboratories performed duplicatedeterminations and repeated one day later, for a total of 32 determina-tions.4Practice E 180 was used in developing these precision estimates.14. Keywords14.1 active oxygen; iodometric; peroxides
36、; peroxyestersASTM 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 riskof infringement of su
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39、e ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).4Supporting data are available from ASTM Headquarters. Request RR: E-1036.E 1228 94 (2003)e13
