1、Designation: D7704 16Standard 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. Scope*1.1 This test method covers the wet chemical determinationof total aldehydes in styrene monomer. Total aldehydes arecalculated
3、 and reported as benzaldehyde. The Range of Con-centration for this test method is 0.004 weight % to 0.013weight %.1.2 Limit of Detection (LOD) and Limit of Quantification(LOQ) is 0.0006 and 0.0020 weight %, respectively1.3 In determining conformance of the test results using thismethod to applicabl
4、e specifications, results shall be rounded offin accordance with the rounding-off method of Practice E29.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard with the exception: weight % should be used ratherthan mass %.1.5 This
5、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 limitations prior to use.2. Referenced Documents2
6、.1 ASTM Standards:2D1193 Specification for Reagent WaterD3437 Practice for Sampling and Handling Liquid CyclicProductsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Con
7、formance with SpecificationsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other Documents:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120033. Summary of Test Method3.1 An alcoholic solution of hydroxylamine hydrochlorideis added to a sp
8、ecimen of styrene monomer. Active aldehydespresent react in accordance with Eq 1:RCHO1NH2OHHClRCHNOH1H2O1HCl (1)The amount of hydrochloric acid released, which is equiva-lent to the aldehyde present in the sample, is titrated withstandard alcoholic potassium hydroxide solution.4. Significance and Us
9、e4.1 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 react withaldehydes to f
10、orm (hemi)acetals.6. Apparatus6.1 Titration Vessel, 150 mL.6.2 Combined pH Glass Electrode, dedicated for non-aqueous liquids.6.3 Stirring Bar, 30 mm.6.4 Titration Stand with stirrer.6.5 Pipets, 25 mL.6.6 Volumetric Flasks, 100 mL.6.7 Burets, 5 mL. (Microburets are preferred.)6.8 Exchange Unit, 5 mL
11、.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 C9 and C10 AromaticHydrocarbons.Current edition approved June 1, 2016. Published October 2016. Original
12、lyapproved in 2011. Last previous edition approved in 2012 as D7704 12. DOI:10.1520/D7704-16.2For 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
13、Summary page onthe ASTM website.3Available from DLA Document Services, Building 4/D, 700 Robbins Ave.,Philadelphia, PA 19111-5094, http:/quicksearch.dla.mil.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh
14、ocken, PA 19428-2959. United States16.9 Thermometers, capable of differentiating 1C at ambi-ent.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
15、 onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.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 othe
16、rwise indicated, referencesto water shall be understood to mean reagent water as definedby Type 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 neutraliz
17、e (to the first equivalency point) with potassiumhydroxide (KOH) in methanol (7.4). Record the 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 (KO
18、H in methanol) to the remaining 900mL of hydroxylamine solution based on the average amountthat 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 hydr
19、oxide (KOH) solution (see 7.5), do not recordvolume. Use the same neutralizing method as mentioned 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 a
20、cid. Use acarbon dioxide scavenger (for example, sodalime) to preventcarbon dioxide from entering the KOH solution.8. Hazards8.1 Consult the latest OSHA regulations, suppliers SafetyData Sheets, and local regulations regarding all materials usedin this test method.8.2 Styrene monomer is flammable an
21、d polymerizes exo-thermally on contact with peroxides, mineral acids, and AlCl3.9. Sampling 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
22、 mL of methanol (7.4) into a 150-mL titration vessel withstirring bar.Add 0.2 mL of water.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 po
23、int,and record the volume used.10.3 Since methanol may contain aldehydes, run a blankdetermination 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
24、, record the volume used.11. Calculation11.1 Calculate the percentage of total aldehydes as benzal-dehyde as follows:Total Aldehydes, as benzaldehyde!, weight % 5A 2 B 2 C! 3 N 30.106! /253 D# 3100 (2)where:A = KOH solution required for titration of the specimen,mL,B = KOH solution required for titr
25、ation of the methanolblank, mL,C = KOH solution required for titration of styrene to checkfor acids, mL,N = normality of KOH solution used, andD = density of styrene monomer.12. Report12.1 Report the aldehydes content to the nearest0.001 weight %.13. Precision and Bias13.1 An ILS was conducted which
26、 included six laboratoriesanalyzing four samples twice. Practice E691 was followed forthe design and analysis of the data; the details are given inASTM Research Report RR:D16-1061.513.1.1 Repeatability Limit (r):13.1.1.1 Results should not be suspect unless they differ bymore than shown in Table 1.
27、Results differing by less than rhave a 95 % probability of being correct.13.1.2 Reproducibility Limit (R):13.1.2.1 Results submitted by two laboratories should notbe considered suspect unless they differ by more than R shownin Table 1. Results differing by less than R have a 95 %probability of being
28、 correct.13.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.13.3 The precision statement was determined through sta-tistical examination of 42 results, from a total of sixlabor
29、atories, on four styrene materials.4Reagent 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
30、., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1061. ContactASTM CustomerService at serviceastm.org.D7704
31、 16214. Quality Guidelines14.1 Laboratories shall have a quality control system inplace: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
32、is a stable material isolatedfrom the production process and representative of the samplebeing 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.14.1.4 When there are no QA/QC protocols es
33、tablished inthe testing facility, use the guidelines described in GuideD6809 or similar statistical quality control practices.15. Keywords15.1 aldehyde content; aldehydes in styrene; benzaldehyde;styreneSUMMARY OF CHANGESCommittee D16 has identified the location of selected changes to this standard
34、since the last issue (D770412)that may impact the use of this standard. (Approved June 1, 2016.)(1) Revised Section 1, ScopeRange of Concentrationadapted to ILS RoC, Limit of Detection (LOD) and Limit ofQuantification (LOQ) included.(2) Weight % will be used as standard, not mass %.(3) Updated Secti
35、on 13, Precision and Bias statement with datafrom interlaboratory study #875 of Test Method D7704.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 determ
36、ination 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 every five years andif not revised, either reapproved or w
37、ithdrawn. 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 technical committee, which you may attend. If you feel that
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39、ingle 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). Permission rights to photocopy the standard may also be secured from the Copyright
40、 Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 1 Total Aldehydes (as benzaldehyde, weight %)Material AverageARepeatabilityLimitReproducibilityLimitXrRStyrene monomer + 0.0010weight % benzaldehyde0.0046 0.0011 0.0053Styrene monomer + 0.0020weight % benzaldehyde0.0060 0.0016 0.0050Styrene monomer + 0.0050weight % benzaldehyde0.0074 0.0010 0.0106Styrene monomer + 0.0100weight % benzaldehyde0.0129 0.0006 0.0106AThe average of the laboratories calculated averages.D7704 163
