1、Designation: E 1899 02Standard 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. Scope1.1 This test method covers the determination of hydro
3、xylgroups 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,a
4、nd 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 ofa
5、cidic 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 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 li
7、mitations prior to use.For specific hazards see Section 9.1.3 Review the current appropriate Material Safety DataSheets (MSDS) for detailed information concerning toxicity,first aid procedures, and safety precautions.2. Referenced Documents2.1 ASTM Standards:D 817 Methods of Testing Cellulose Acetat
8、e Propionate andCellulose Acetate Butyrate2D 871 Test Methods of Testing Cellulose Acetate2D 1193 Specification for Reagent Water3D 1957 Test Method for Hydroxyl Value of Fatty Oils andAcids2D 2195 Test Methods for Pentaerythritol4D 4252 Test Methods for Chemical Analysis of AlcoholEthoxylates and A
9、lkylphenol Ethoxylates5D 4273 Test Methods for Polyurethane Raw Materials:Determination of Primary Hydroxyl Content of PolyetherPolyols6D 4274 Test Methods for Testing Polyurethane Raw Mate-rials: Determination of Hydroxyl Numbers of Polyols6E 180 Practice for Determining the Precision of ASTMMethod
10、s for Analysis and Testing of Industrial Chemicals7E 222 Test Methods for Hydroxyl Groups Using AceticAnhydride Acylation7E 300 Standard Practice for Sampling Industrial Chemicals7E 326 Test Method for Hydroxyl Groups by PhthalicAnhydride Esterification7E 335 Test Method for Hydroxyl Groups by Pyrom
11、elliticDianhydride Esterification73. Terminology3.1 Definitions:3.1.1 hydroxyl number (OH#)the milligrams of potassiumhydroxide equivalent to the hydroxyl content of1gofsample.3.1.1.1 DiscussionIn the case of a pure compound, thehydroxyl number is inversely proportional to the hydroxylequivalent wei
12、ght and the molecular weight:equivalent weight g/equivalent!556100OH#(1)and:molecular weight g/mol!556100 3 number of OH groups per moleculeOH#1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and is the direct responsibility of SubcommitteeE15.01
13、 on General Standards.Current edition approved Oct. 10, 2002. Published December 2002. Originallypublished as E 1899-97. Last previous edition E 1899-97.2Annual Book of ASTM Standards, Vol 06.03.3Annual Book of ASTM Standards, Vol 11.01.4Annual Book of ASTM Standards, Vol 06.04.5Annual Book of ASTM
14、Standards, Vol 15.04.6Annual Book of ASTM Standards, Vol 08.02.7Annual Book of ASTM Standards, Vol 15.05.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 According to a reaction given in Manser, et al,8(se
15、e Fig.1) the hydroxyl group is reacted with excess p-toluenesulfonylisocyanate (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
16、me-dium.5. Significance and Use5.1 Hydroxyl is an important functional group 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
17、them.5.2 This test method has the following advantages overother hydroxyl 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 deriva
18、tize quantitativelywith the TSI reagent and contribute to the hydroxyl value.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. Optimu
19、mtitration curves are obtained, however, when the water is 1%.6.3 Any acidic 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
20、 acidic carbamate to cause low hydroxyl number values. Ifthis test method 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 TestM
21、ethod B of Test Methods E 222 , to establish concordance ofresults with the 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
22、not there is interference exhibited. For example, methanesulfonic acid titrates 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 interfe
23、r-ence.7. Apparatus7.1 Potentiometric Autotitrator, equipped with a 10 or20mL 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 au
24、tomaticmarking of end points was shown to give excellent hydroxylnumber results 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, 500L.7.
25、4 Glass or Plastic Beakers, 100-mL.7.5 Magnetic Stirrer and Stirring Bars, (3cm 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 Graduat
26、ed Cylinder, 10-mL, or Bottle Type VolumetricDispenser.8. Reagents8.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee on Analytical Reagents of the American Chemi-cal Society, where such specifications are available.9O
27、thergrades may be used, provided it is first ascertained that thereagent is 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
28、as defined in Specification D 1193.8.3 Acetonitrile, HPLC Grade must be used as it is suffi-ciently low in moisture so that molecular sieves are not neededto dry this solvent.8.4 2-Propanol, HPLC Grade.8.5 p-Toluenesulfonyl Isocyanate (TSI), 96 %Maintain anitrogen pad above this reagent after openin
29、g bottle.8.6 TSI ReagentPipet 20 mL of TSI into a 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
30、Solu-tion in Methanol, 100 mL.8.9 Tetrabutylammonium Hydroxide (Titrant), 0.1NPrepare by transferring the entire 100 mL of 1M Bu4NOH8Manser, 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
31、. 1-3 of Appendix A, August, 1985.9Reagent 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.
32、, and the United States Pharmacopeia andNational Formulary, U.S. Pharmacopeial Convention, Inc. (USPC). Rockville, MD.FIG. 1 Hydroxyl Group ReactionE 1899 022in methanol (see 8.8) into a 1L volumetric flask that is halffilled with 2-propanol. Rinse the emptied bottle that containedthe solution in 8.
33、8 and transfer the rinsings to the contents ofthe 1L volumetric flask. Swirl contents and dilute to the markwith 2-propanol. Stopper the flask and mix well. Finally,transfer the flask contents to the buret reservoir of a potentio-metric autotitrator and standardize the titrate versus dried (2 h,120C
34、) potassium hydrogen phthalate (KHP) as follows: dis-solve approximately 0.18 g of KHP, weighed to 0.1 mg, inabout 60 mL of water contained in a 100-mL beaker. Stirseveral minutes to ensure complete dissolution of the KHP.Perform a potentiometric titration directly on the KHP solutionusing the 0.1 N
35、 Bu4NOH titrant. Perform three to five stan-dardization titrations to obtain a reliable average value for the0.1 N Bu4NOH normality.N 5KHP, g0.20423 3 Bu4NOH, mL(2)where:N = normality of the 0.1 N Bu4NOH expressedto four decimal places, andBu4NOH, mL = mL of this titrant to reach a potentiometricend
36、 point in the reaction with KHP.8.10 Methanol.8.11 Acetone.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
37、Lachrymator. Incase of contact with eyes, rinse immediately 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 vap
38、or. Do not getin eyes, on skin, or on clothing.10. Sampling10.1 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 lowtemper
39、ature oven to obtain a clear liquid prior to weighing.Low 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 i
40、s obtained. After heating, invert the sample containertwenty 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 g
41、lass orplastic transfer pipet. The optimum weight of sample 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 magn
42、etic stirringbar and stir slowly on a magnetic stirrer until 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 use
43、d as solvent for samples whichmay be insoluble in acetonitrile. 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.11.3 Pipet 10 6 0.1 mL of TSI reagent in
44、to the samplesolution, cover beaker with a watch glass and stir slowly on themagnetic stirrer for 5 min.11.4 Add 0.5 mL of 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,
45、blot dry the end of the combinationpH electrode and buret delivery 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
46、that all bubbles are expunged from the buretbarrel and delivery tip 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
47、 modes regarding symmetry and spurious end points.Otherwise, the 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 delivery
48、tube 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 volu
49、me to the second end point, V2.Although pH values will not enter into the calculations, recordthe “apparent” pH values at each of the potentiometric inflec-tion points. They are useful reference points (see Note 3).NOTE 3A typical potentiometric titration curve (see Fig. 2), will havetwo or three inflections. The volume to V1is proportional to acidic speciesof the greatest strength and is reported to be related to age of reagent,catalysts present, and water in the sample. V1is usually 0.5 to 1.0 mL. Thedifference between V2and V1is related to the titration of the ac
