1、Designation: E 1228 09Standard 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 year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the assay of organic peroxidesof the peroxy ester type.NOTE 1Other test methods for the assay of organic
3、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-dures, and safety precautions.1.3 The values stated in SI units are to be regarded as thestandard. No other units of measu
4、rement are included in thistest method.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 practices and determine the applica-bility of regulatory l
5、imitations 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 Industrial and Spe-cialty ChemicalsE 200 Practice for Pr
6、eparation, 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 PeroxideUsing Gas ChromatographyE 755 Test Method for Dicumyl Peroxide, Assay (LiquidChromatography)3. Terminol
7、ogy3.1 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. A solution of potassium iodideis added and the mix
8、ture 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 Peroxy esters are widely used as chemical intermedi-
9、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 iodine.7. Apparatus7.1 Iodine Flasks, 250-mL capaci
10、ty, 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. Reagents8.1 Purity of ReagentsReagent grade chemi
11、cals 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 Chemical1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and
12、is the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved April 1, 2009. Published April 2009. Originallyapproved in 1988. Last previous edition approved in 2003 as E 1228 - 94(2003)1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orconta
13、ct ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
14、Conshohocken, PA 19428-2959, United States.Society, where such specifications are available.3Other gradesmay be used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe accuracy of the determination.8.2 Purity of WaterUnless otherwi
15、se 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 (HCl) to 100 mL with water.8.6 Cupric Chloride Sol
16、ution, 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. Thisreagent should be freshly prepared just prior to
17、use.8.8 Sodium Thiosulfate Standard Solution, (0.1 meq/mL)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 fire and explosion hazards.Avoid contact withr
18、educing 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-ventilated area.10. Procedure10.1 Add 50 mL of isoprop
19、yl 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. (WarningThe quantity of the cupric chloride catalystsolution must be carefully measured in order to obtain repro-ducible results as
20、 the reagent also reacts with iodide to liberateiodine according to the following Eq 1:2Cu111 4I22 CuI 1 I2(1)The blank titration should be approximately 1.0 mL. The results should bediscarded and the analysis repeated if a significantly higher blank value isobtained.)10.3 Sparge the solution with a
21、 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 andmix. The approximate sample weight may be calculated
22、 asfollows:Sample mass, g 53.5 M2C3 1000(2)where:M = molecular weight of compound, andC = number of peroxide groups in the molecule.NOTE 3Volatile liquid peroxides may be diluted to a known volumewith isopropyl alcohol and aliquots taken for analysis.10.5 While maintaining a flow of nitrogen over th
23、e 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 the level of solution in the flask.NOTE 4The reactio
24、n 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 preheating the solution for 20s at 60C, the solution temperat
25、ure 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 water and titrate the solutionwith 0.1 meq/mL Na2S2O3
26、solution to the colorless end point.Record the number of millilitres required for the sampletitration.10.9 Subtract the number of millilitres required for titrationof a blank carried simultaneously through the entire procedureand calculate the assay value of the sample. (See Warning notein 10.2.)11.
27、 Calculation11.1 Calculate the assay as follows:assay, as % compound 5A 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 = meq/mL, normality of the Na2S2O3solution,C = number of peroxide g
28、roups 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 5This assay is based on the determination of active oxygenunder specified conditions. If other or
29、ganic 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 the compound to the nearest0.1
30、 %.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 LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharma
31、copeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.E122809213. Precision and Bias413.1 PrecisionThe following criteria should be used forjudging the acceptability of results: (see Note 6).13.1.1 Repeatability (Single Analyst)The standard devia-tion for a single de
32、termination has been estimated to be0.135 % at 14 DF. The 95 % limit for the difference betweentwo such runs is 0.4 %.13.1.2 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
33、at 6 DF. The 95 % limit for the difference between 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 %
34、 limit for the differencebetween two such averages is 0.7 %.13.2 BiasThe bias of this test method cannot be deter-mined due to the unavailability of suitable reference materials.NOTE 6The above precision estimates are based upon an interlabo-ratory study performed in 1987 on samples of t-butyl perbe
35、nzoate andt-butyl peracetate with manufacturers 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 determinations.Practice E 180 was used in developing these precision estimates.14. Keywor
36、ds14.1 active oxygen; iodometric; peroxides; peroxyestersSUMMARY OF CHANGESCommittee E15 has identified the location of selected changes to this standard since the last issue(E 1228 - 94(2003)1) that may impact the use of this standard. (April 1, 2009)(1) Updated units of measure to comply with the
37、InternationalSystem of Units (SI).(2) Added paragraph in Scope stating that the SI units are to beconsidered standard.(3) 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.
38、 Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed e
39、very five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible tec
40、hnical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho
41、cken, 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: E15-1036.E1228093
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