1、Designation: E 1899 08Standard Test Method forHydroxyl Groups Using Reaction with p-ToluenesulfonylIsocyanate (TSI) and Potentiometric Titration withTetrabutylammonium Hydroxide1This standard is issued under the fixed designation E 1899; the number immediately following the designation indicates the
2、 year oforiginal adoption or, in the case of revision, the 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.1. Scope*1.1 This test method covers the determination of hydr
3、oxylgroups attached to primary and secondary carbon atoms inaliphatic and cyclic compounds and phenols. It is not suitablefor determination of hydroxyl groups attached to tertiarycarbon atoms. This test method is applicable to polyacetals,temperature sensitive materials, high solids polymer polyols,
4、and rigid polyols. Other available test methods listed in Note 1are not suitable for many of the sample types listed above.1.1.1 This test method is currently recommended for neutralrefined products. Successful application has been made, how-ever, to some in-process samples that contain an excess of
5、acidic species. Proper validation must be performed, of course,to show that the acidic species either does not interfere, or thatthe acidic species interference has been obviated.NOTE 1Other methods for determination of hydroxyl groups aregiven in Test Methods D 817, D 871, D 1957, D 2195, D 4252, D
6、 4273,D 4274, E 222, E 326, and E 335.1.2 Review the current appropriate Material Safety DataSheets (MSDS) for detailed information concerning toxicity,first aid procedures, and safety precautions.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are incl
7、uded 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 and health practices and determine the applica-bility of regulatory limitations prior
8、to use.For specific hazards see Section 9.2. Referenced Documents2.1 ASTM Standards:2D 817 Test Methods of Testing Cellulose Acetate Propi-onate and Cellulose Acetate ButyrateD 871 Test Methods of Testing Cellulose AcetateD 1193 Specification for Reagent WaterD 1957 Test Method for Hydroxyl Value of
9、 Fatty Oils andAcids3D 2195 Test Methods for PentaerythritolD 4252 Test Methods for Chemical Analysis of AlcoholEthoxylates and Alkylphenol EthoxylatesD 4273 Test Method for Polyurethane Raw Materials: De-termination of Primary Hydroxyl Content of PolyetherPolyolsD 4274 Test Methods for Testing Poly
10、urethane Raw Mate-rials: Determination of Hydroxyl Numbers of PolyolsE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty ChemicalsE 222 Test Methods for Hydroxyl Groups Using AceticAnhydride AcetylationE 300 Practice for Sampling Industri
11、al ChemicalsE 326 Test Method for Hydroxyl Groups by Phthalic Anhy-dride Esterification (Discontinued 2001)3E 335 Test Method for Hydroxyl Groups by PyromelliticDianhydride Esterification33. Terminology3.1 Definitions:3.1.1 hydroxyl number (OH#)the milligrams of potassiumhydroxide equivalent to the
12、hydroxyl content of1gofsample.1This 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 April 1, 2008. Published May 2008. Originallyapproved in 1997. Las
13、t previous edition approved in 2002 as E 1899 02.2For 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.3Withdrawn.1
14、*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1.1 DiscussionIn the case of a pure compound, thehydroxyl number is inversely proportional to the hydroxylequivalent
15、 weight and the molecular weight:equivalent weight g/equivalent!556100OH#(1)and:molecular weight g/mol!556100 3 number of OH groups per moleculeOH#4. Summary of Test Method4.1 According to a reaction given in Manser et al.4(see Fig.1) the hydroxyl group is reacted with excess p-toluenesulfonylisocya
16、nate (TSI), to form an acidic carbamate. Water is addedto convert unreacted isocyanate to sulfonamide, followed bydirect potentiometric titration of the acidic carbamate withtetrabutylammonium hydroxide (Bu4NOH) in nonaqueous me-dium.5. Significance and Use5.1 Hydroxyl is an important functional gro
17、up and knowl-edge of its content is required in many intermediate and enduse applications. This test method is for the determination ofprimary and secondary hydroxyl groups and can be used for theassay of compounds containing them.5.2 This test method has the following advantages overother hydroxyl
18、number methods: It is rapid (10 min), pyridine-free, ambient temperature, small sample size, applicable toextremely low hydroxyl numbers (1), and is amenable toautomation.6. Interferences6.1 Primary and secondary amines derivatize quantitativelywith the TSI reagent and contribute to the hydroxyl val
19、ue.6.2 High levels of water in the sample can interfere byconsuming reagent. The amount of excess TSI reagent pre-scribed by this test method is quite large, however, so thatrather high water levels can be accommodated. Optimumtitration curves are obtained, however, when the water is 1%.6.3 Any acid
20、ic species with a pKa value close to that of theacidic carbamate (formed between TSI and the hydroxylcompound), will contribute to the hydroxyl number and causehigh values. Excess base in a sample may potentially react withthe acidic carbamate to cause low hydroxyl number values. Ifthis test method
21、is to be used for samples other than neutralrefined products, the analyst must first validate this test methodon a case by case basis. For example, an in-process samplecontaining excess acid or base may be analyzed using TestMethod B of Test Methods E 222 , to establish concordance ofresults with th
22、e current TSI test method for that particularmatrix. The identities of acidic or basic species contained inin-process samples are frequently known, so that knownaddition of these moieties to the sample can establish whetheror not there is interference exhibited. For example, methanesulfonic acid tit
23、rates sufficiently before the acidic carbamateformed between TSI and ROH, and therefore does not inter-fere. At the other extreme, methacrylic acid titrates well afterthe acidic carbamate of interest and thus causes no interfer-ence.7. Apparatus7.1 Potentiometric Autotitrator, equipped with a 10 or2
24、0mL delivery buret. Ideally, the autotitrator should becapable of generating the potentiometric titration curve in thenormal and derivative modes with automatic marking of endpoints. However, an older model titrator without automaticmarking of end points was shown to give excellent hydroxylnumber re
25、sults obtained by manually evaluating the mid-pointof the normal “S” shaped curve.7.2 Glass Combination pH Electrode, consisting of a glasssensing membrane and Ag/AgCl internal reference element.7.3 Automatic Pipetter, 500 L.7.4 Glass or Plastic Beakers, 100 mL.7.5 Magnetic Stirrer and Stirring Bars
26、, (3-cm length isoptimum).7.6 Glass Pipet, 10 and 20 mL, Class A.7.7 Volumetric Flasks, 500 and 1000 mL.7.8 Analytical Balance, accurate to 0.1 mg.7.9 Standard Bulb Transfer Pipets, plastic, approximately15cm length.7.10 Graduated Cylinder, 10 mL, or Bottle Type VolumetricDispenser.8. Reagents8.1 Pu
27、rity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society, where such specifications are available.5Othergrades may be used, provided it is first ascertained that thereagent i
28、s of sufficiently high purity to permit its use withoutlessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean Type II or Type IIIreagent water as defined in Specification D 1193.8.3 Acetonitrile, HPLC Grade must be us
29、ed as it is suffi-ciently low in moisture so that molecular sieves are not neededto dry this solvent.8.4 2-Propanol, HPLC Grade.4Manser, G.E., Fletcher, R.W., and Knight, M.R., High Energy Binders FinalReport, Defense Technical Information Center, Ft. Belvoir, VA, Contract No.N00014-82-C-0800, p. 1-
30、3 of Appendix A, August, 1985.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., an
31、d the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Hydroxyl Group ReactionE 1899 0828.5 p-Toluenesulfonyl Isocyanate (TSI), 96 %Maintain anitrogen pad above this reagent after opening bottle.8.6 TSI ReagentPipet 20 mL of TSI into a
32、 dry 500-mLvolumetric flask half filled with acetonitrile. Dilute to the markwith acetonitrile and mix well. This reagent should be preparedfresh monthly.8.7 Potassium Hydrogen Phthalate, Primary Standard.8.8 Tetrabutylammonium Hydroxide (Bu4NOH), 1M Solu-tion in Methanol, 100 mL.8.9 Tetrabutylammon
33、ium Hydroxide (Titrant), 0.1 meq/mLPrepare by transferring the entire 100 mL of 1MBu4NOH in methanol (see 8.8) into a 1L volumetric flask thatis half filled with 2-propanol. Rinse the emptied bottle thatcontained the solution in 8.8 and transfer the rinsings to thecontents of the 1L volumetric flask
34、. Swirl contents and diluteto the mark with 2-propanol. Stopper the flask and mix well.Finally, transfer the flask contents to the buret reservoir of apotentiometric autotitrator and standardize the titrate versusdried (2 h, 120C) potassium hydrogen phthalate (KHP) asfollows: dissolve approximately
35、0.18 g of KHP, weighed to 0.1mg, in about 60 mLof water contained in a 100-mLbeaker. Stirseveral minutes to ensure complete dissolution of the KHP.Perform a potentiometric titration directly on the KHP solutionusing the 0.1 meq/mL Bu4NOH titrant. Perform three to fivestandardization titrations to ob
36、tain a reliable average value forthe 0.1 meq/mL Bu4NOH concentration.N 5KHP, g0.20423 3 Bu4NOH, mL(2)where:N = concentration of the 0.1 meq/mLBu4NOH expressed to four decimalplaces, andBu4NOH, mL = mL of this titrant to reach a potentiometricend point in the reaction with KHP.8.10 Methanol.8.11 Acet
37、one.9. Hazards9.1 p-Toluenesulfonyl Isocyanate (TSI) is harmful by inha-lation, in contact with skin and if swallowed. It may causesensitization by inhalation and skin contact. It reacts violentlywith water. It causes severe irritation. It is a Lachrymator. Incase of contact with eyes, rinse immedia
38、tely with plenty ofwater and seek medical advice. Never add water to thisproduct.9.2 Wear suitable protective clothing, gloves and eye/faceprotection when handling p-Toluenesulfonyl Isocyanate. Useonly in a chemical fume hood. Do not breathe vapor. Do not getin eyes, on skin, or on clothing.10. Samp
39、ling10.1 Special precautions may be necessary to ensure that arepresentative sample is taken for analysis. General guidelinesfor sampling may be found in Practice E 300. Samples whichare solids at room temperature should be heated in a lowtemperature oven to obtain a clear liquid prior to weighing.L
40、ow temperature (50 to 70C), should be tried first to avoidany undesirable changes in the sample. If higher temperaturesare required to melt the sample, for example, 110C, then thesample should be removed from the oven as soon as a clearliquid is obtained. After heating, invert the sample containertw
41、enty times to ensure complete homogenization. Samples thatare liquid at room temperature only require inversion mixing.11. Procedure11.1 Tare a 100-mL glass or plastic beaker on an analyticalbalance and transfer a sample to the beaker using a glass orplastic transfer pipet. The optimum weight of sam
42、ple isdetermined from the following relationship:sample, g540expected OH#(3)For expected OH# values of 2 or less, use 15 to 20 g ofsample.11.2 Using a graduated cylinder or other volumetric dis-penser, add 10 mL of acetonitrile. Then add a magnetic stirringbar and stir slowly on a magnetic stirrer u
43、ntil sample isdissolved (30 s is usually sufficient) (see Note 2).NOTE 2Although acetonitrile has been found to dissolve a wide rangeof sample types (and should be used where possible), tetrahydrofuran orpentene stabilized chloroform may be used as solvent for samples whichmay be insoluble in aceton
44、itrile. Alternatively, 3 mL of toluene may beused to dissolve a sample, followed immediately by addition of 7 mL ofacetonitrile. Superior potentiometric titration curves are obtained inacetonitrile media. If there are difficulties in titrating while using less polarsolvents, one may need to demonstr
45、ate the operation of the standardelectrode (Section 7.2) and confirm its functionality under these condi-tions. Substitution of a more solvent compatible potentiometric electrodecan be considered.11.3 Pipet 10 6 0.1 mL of TSI reagent into the samplesolution, cover beaker with a watch glass and stir
46、slowly on themagnetic stirrer for 5 min.11.4 Add 0.5 mLof water to destroy excess TSI reagent. Stirfor 1 min at slow speed.11.5 Add 30 mL of acetonitrile using a graduated cylinderor other volumetric dispenser.11.6 Using tissue paper, blot dry the end of the combinationpH electrode and buret deliver
47、y tube tip. Immerse electrodeand buret delivery tube tip into the sample solution, stir at amoderate speed, and begin the titration with 0.1 N standardizedBu4NOH solution. Follow instruction manual for the autotitra-tor and be certain that all bubbles are expunged from the buretbarrel and delivery t
48、ip tubing before beginning the titration. Asis the case in all potentiometric titrations, it is advantageous ifboth normal and derivative titration curves can be run simul-taneously, as complementary information can be gleaned fromboth modes regarding symmetry and spurious end points.Otherwise, the
49、analyst may choose which of the two modes touse. Ideally, the titration end point volumes are automaticallymarked.11.7 When the titration has been complete, raise the elec-trode and buret delivery tube tip. Rinse electrode and deliverytube tip with methanol or acetone. This removes residualadhering organic material. Next, rinse electrode and tip withwater and immerse the electrode in water to maintain goodhydration of electrode bulb between titrations.11.8 Record the volume in mL to the first potentiometricend point, V1, and volume to the second end point, V2.E 189
