1、Designation: D7704 11Standard Test Method forTotal Aldehydes in Styrene Monomer by PotentiometricTitration1This standard is issued under the fixed designation D7704; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、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 wet chemical determinationof aldehydes in styrene monomer. Aldehydes are calculatedand reported
3、 as benzaldehyde. The range of concentration forthis test method is 0.001 mass % to 0.030 mass %.1.2 In determining conformance of the test results using thismethod to applicable specifications, results shall be rounded offin accordance with the rounding-off method of Practice E29.1.3 The values sta
4、ted in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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 an
5、d health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD3437 Practice for Sampling and Handling Liquid CyclicProductsD6809 Guide for Quality Control and Quality AssuranceProcedures for
6、 Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications2.2 Other Documents:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120033. Summary of Test Method3.1 An alcoholic solution of hydroxylamine hydrochlor
7、ideis added to a specimen of styrene monomer. Active aldehydespresent react in accordance with Eq 1:RCHO 1 NH2OHHClRCHNOH 1 H2O 1 HCl (1)The amount of hydrochloric acid released, which is equiva-lent to the aldehyde present in the sample, is titrated withstandard alcoholic potassium hydroxide soluti
8、on.4. Significance and Use4.1 This test method is suitable for determining the quantityof aldehydes, both for quality control and quality assurance ofthe product.5. Interferences5.1 Ketones, if present, interfere by partially reacting withthe reagent.5.2 Methanol used in this procedure may partially
9、 react withaldehydes to form (hemi)acetals.6. Apparatus6.1 Titration Vessel, 150 mL.6.2 Combined pH Glass Electrode, dedicated for non-aqueous liquids.6.3 Stirring Bar,30mm.6.4 Titration Stand with stirrer.6.5 Pipets,25mL.6.6 Volumetric Flasks, 100 mL.6.7 Burets, 5 mL. (Microburets are preferred.)6.
10、8 Exchange Unit, 5 mL.6.9 Thermometers, capable of differentiating 1C at ambi-ent.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.07 on Styrene, Ethylbenzene and C9and C10Aromatic Hydr
11、o-carbons.Current edition approved March 1, 2011. Published March 2011. DOI: 10.1520/D770411.2For 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
12、Summary page onthe ASTM website.3Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/dodssp.daps.dla.mil.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States
13、.7. Reagents and Materials7.1 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 Chemical Society wheresuch specifications are available.
14、4Other 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.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type
15、 III of Specification D1193.7.3 Hydroxylamine Hydrochloride SolutionDissolve 20 gof hydroxylamine hydrochloride (NH2OHHCl) in 1 L ofmethanol. Take a portion of this volume (for example, 50 mL)and neutralize (to the first equivalency point) with potassiumhydroxide (KOH) in methanol (7.4). Record the
16、amount ofKOH required and the reading (in mV) of the electrode whenneutralized. For accuracy, repeat this procedure with a secondportion and average the amount of KOH required. Addneutralizing solution (KOH in methanol) to the remaining 900mL of hydroxylamine solution based on the average amountthat
17、 was calculated. Check neutrality regularly (for example,once a week) by either checking the reading of the electrode orby titration.7.4 Methanol, free of acids. If necessary, neutralize withpotassium hydroxide (KOH) solution (see 7.5), do not recordvolume. Use the same neutralizing method as mentio
18、ns in 7.3for hydroxylamine hydrochloride solution.7.5 Potassium Hydroxide, Standard Solution in Methanol(0.1 N)Dilute five times to a concentration of 0.02 N.Standardize against primary standard benzoic acid. Use acarbon dioxide scavenger (for example, sodalime) to preventcarbon dioxide from enterin
19、g the KOH solution.8. Hazards8.1 Consult the latest OSHAregulations, suppliers MaterialSafety Data Sheets, and local regulations regarding all mate-rials used in this test method.8.2 Sytrene monomer is flammable and polymerizes exo-thermally on contact with peroxides, mineral acids, and AlCl3.9. Sam
20、pling and Handling9.1 Collect the sample as directed in Practice D3437.10. Procedure10.1 Prepare the pH electrode according to the manufactur-ers instructions.10.2 Pipet 25.0 mL of the sample (Warningsee 8.2) and25 mL of methanol (7.4) into a 150-mL titration vessel withstirring bar.Add 0.2 mL of wa
21、ter.Add 25 mL of the neutralizedhydroxylamine hydrochloride solution and allow to stand 0.5 hwhile stirring. Titrate with the 0.02 N KOH/methanol solution,dispensed from a 5-mL buret, until the first equivalence point,and record the volume used.10.3 Since methanol may contain aldehydes, run a blankd
22、etermination on 25 mL of methanol (7.4), record the volumeused.10.4 Since styrene may contain acids, run a blank determi-nation by repeating 10.2 without adding the neutralized hy-droxylamine hydrochloride solution, record the volume used.11. Calculation11.1 Calculate the percentage of aldehydes as
23、benzaldehydeas follows:Aldehydes, mass % 5 A 2 B 2 C!/N 3 0.106!/25 3 D 3 100(2)where:A = KOH solution required for titration of the specimen,mL,B = KOH solution required for titration of the methanolblank, mL,C = KOH solution required for titration of styrene to checkfor acids, mL,N = normality of
24、KOH solution used, andD = density of styrene monomer.12. Report12.1 Report the aldehydes content to the nearest 0.001mass %.13. Precision and Bias13.1 RepeatabilityResults should not be suspect unlessthey differ by more than shown in Table 1. Results differing byless than “r” have a 95 % probability
25、 of being correct.13.2 ReproducibilityNo data available.13.3 BiasSince there is no accepted reference materialsuitable for determining the bias in this test method formeasuring aldehydes, bias has not been determined.14. Quality Guidelines14.1 Laboratories shall have a quality control system inplace
26、:14.1.1 Confirm the performance of the test instrument ortest method by analyzing a quality control sample followingthe guidelines of standard statistical quality control practices.14.1.2 A quality control sample is a stable material isolatedfrom the production process and representative of the samp
27、lebeing analyzed.14.1.3 When QA/QC protocols are already established inthe testing facility, these protocols are acceptable when theyconfirm the validity of test results.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the tes
28、ting 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 RepeatabilityAAldehyde Content, mass %
29、Repeatability, mass %0.004 0.00030.03 0.002ABased on 10 duplicate results obtained by the same operator on a single day.D7704 11214.1.4 When there are no QA/QC protocols established inthe testing facility, use the guidelines described in GuideD6809 or similar statistical quality control practices.15
30、. Keywords15.1 aldehyde content; aldehydes in styrene; benzaldehyde;styreneASTM 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
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