1、Designation: E1899 08E1899 16Standard Test Method forHydroxyl Groups Using Reaction with p-ToluenesulfonylIsocyanate (TSI) and Potentiometric Titration withTetrabutylammonium Hydroxide1This standard is issued under the fixed designation E1899; the number immediately following the designation indicat
2、es the 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 () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of
3、 hydroxyl groups attached to primary and secondary carbon atoms in aliphaticand cyclic compounds and phenols. It is not suitable for determination of hydroxyl groups attached to tertiary carbon atoms. Thistest method is applicable to polyacetals, temperature sensitive materials, high solids polymer
4、polyols, and rigid polyols. Otheravailable test methods listed in Note 1 are not suitable for many of the sample types listed above.1.1.1 This test method is currently recommended for neutral refined products. Successful application has been made, however,to some in-process samples that contain an e
5、xcess of acidic species. Proper validation must be performed, of course, to show thatthe acidic species either does not interfere, or that the acidic species interference has been obviated.NOTE 1Other methods for determination of hydroxyl groups are given in Test Methods D817, D871, D1957, D2195, D4
6、252, D4273, D4274, E222,E326, and E335.1.2 Review the current appropriate Material Safety Data Sheets (MSDS)(SDS) for detailed information concerning toxicity, firstaid procedures, and safety precautions.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement
7、are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated, with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations
8、 prior to use. For specific hazards see Section 9.For specific hazards see Section 9.2. Referenced Documents2.1 ASTM Standards:2D817 Test Methods of Testing Cellulose Acetate Propionate and Cellulose Acetate ButyrateD871 Test Methods of Testing Cellulose AcetateD1193 Specification for Reagent WaterD
9、1957 Test Method for Hydroxyl Value of Fatty Oils and Acids (Withdrawn 2007)3D2195 Test Methods for Pentaerythritol (Withdrawn 2011)3D4252 Test Methods for Chemical Analysis of Alcohol Ethoxylates and Alkylphenol EthoxylatesD4273 Test Method for Polyurethane Raw Materials: Determination of Primary H
10、ydroxyl Content of Polyether PolyolsD4274 Test Methods for Testing Polyurethane Raw Materials: Determination of Hydroxyl Numbers of PolyolsE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals(Withdrawn 2009)3E222 Test Methods for
11、Hydroxyl Groups Using Acetic Anhydride AcetylationE300 Practice for Sampling Industrial ChemicalsE326 Test Method for Hydroxyl Groups by Phthalic Anhydride Esterification (Discontinued 2001) (Withdrawn 2001)3E335 Test Method for Hydroxyl Groups by Pyromellitic Dianhydride Esterification (Withdrawn 2
12、002)31 This test method is under the jurisdiction of ASTM Committee E15 on Industrial and Specialty Chemicals and is the direct responsibility of Subcommittee E15.01 onGeneral Standards.Current edition approved April 1, 2008April 1, 2016. Published May 2008May 2016. Originally approved in 1997. Last
13、 previous edition approved in 20022008 asE1899 02.E1899 08. DOI: 10.1520/E1899-08.10.1520/E1899-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Docu
14、ment Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
15、it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears
16、at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Definitions:3.1.1 hydroxyl number (OH#)the milligrams of potassium hydroxide equivalent to the hydroxyl content of 1 g of sample.3.1.1.1 Disc
17、ussionIn the case of a pure compound, the hydroxyl number is inversely proportional to the hydroxyl equivalent weight and the molecularweight:equivalent weight g/equivalent!556100OH# (1)and:molecular weight g/mol!5561003number of OH groups per moleculeOH#4. Summary of Test Method4.1 According to a r
18、eaction given in Manser et al.4 (see Fig. 1) the hydroxyl group is reacted with excess p-toluenesulfonylisocyanate (TSI), to form an acidic carbamate. Water is added to convert unreacted isocyanate to sulfonamide, followed by directpotentiometric titration of the acidic carbamate with tetrabutylammo
19、nium hydroxide (Bu4NOH) in nonaqueous medium.5. Significance and Use5.1 Hydroxyl is an important functional group and knowledge of its content is required in many intermediate and end useapplications. This test method is for the determination of primary and secondary hydroxyl groups and can be used
20、for the assayof compounds containing them.5.2 This test method has the following advantages over other hydroxyl number methods: It is rapid (10 min), pyridine-free,ambient temperature, small sample size, applicable to extremely low hydroxyl numbers (1), and is amenable to automation.6. Interferences
21、6.1 Primary and secondary amines derivatize quantitatively with the TSI reagent and contribute to the hydroxyl value.6.2 High levels of water in the sample can interfere by consuming reagent. The amount of excess TSI reagent prescribed by thistest method is quite large, however, so that rather high
22、water levels can be accommodated. Optimum titration curves are obtained,however, when the water is 1 %.1 %.6.3 Any acidic species with a pKa value close to that of the acidic carbamate (formed betweenTSI and the hydroxyl compound),will contribute to the hydroxyl number and cause high values. Excess
23、base in a sample may potentially react with the acidiccarbamate to cause low hydroxyl number values. If this test method is to be used for samples other than neutral refined products,the analyst must first validate this test method on a case by case basis. For example, an in-process sample containin
24、g excess acidor base may be analyzed using Test Method B of Test Methods E222, to establish concordance of results with the current TSI testmethod for that particular matrix. The identities of acidic or basic species contained in in-process samples are frequently known,so that known addition of thes
25、e moieties to the sample can establish whether or not there is interference exhibited. For example,methane sulfonic acid titrates sufficiently before the acidic carbamate formed between TSI and ROH, and therefore does notinterfere.At the other extreme, methacrylic acid titrates well after the acidic
26、 carbamate of interest and thus causes no interference.7. Apparatus7.1 Potentiometric Autotitrator, equipped with a 1010- or 20mL20-mL delivery buret. Ideally, the autotitrator should becapable of generating the potentiometric titration curve in the normal and derivative modes with automatic marking
27、 of end points.4 Manser, G.E., Fletcher, R.W., and Knight, M.R., High Energy Binders Final Report, Defense Technical Information Center, Ft. Belvoir, VA, Contract No.N00014-82-C-0800, p. 1-3 of Appendix A, August, 1985.FIG. 1 Hydroxyl Group ReactionE1899 162However, an older model titrator without a
28、utomatic marking of end points was shown to give excellent hydroxyl number resultsobtained by manually evaluating the mid-point of the normal “S” shaped curve.7.2 Glass Combination pH Electrode, consisting of a glass sensing membrane and Ag/AgCl internal reference element.7.3 Automatic Pipetter, 500
29、 L.7.4 Glass or Plastic Beakers, 100 mL.7.5 Magnetic Stirrer and Stirring Bars, (3-cm length is optimum).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, approximately 15cm15-cm length
30、.7.10 Graduated Cylinder, 10 mL, or Bottle Type Volumetric Dispenser.8. Reagents8.1 Purity of ReagentsUnless otherwise indicated, it is intended that all reagents shall conform to the specifications of theCommittee onAnalytical Reagents of theAmerican Chemical Society, where such specifications are
31、available.5 Other grades maybe used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracyof the determination.8.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean Type II or Type II
32、I reagentwater as defined in Specification D D119311938.3 Acetonitrile, HPLC Grade must be used as it is sufficiently low in moisture so that molecular sieves are not needed to drythis solvent.8.4 2-Propanol, HPLC Grade.8.5 p-Toluenesulfonyl Isocyanate (TSI), 96 %Maintain a nitrogen pad above this r
33、eagent after opening bottle.8.6 TSI ReagentPipet 20 mL of TSI into a dry 500-mL volumetric flask half filled with acetonitrile. Dilute to the mark withacetonitrile and mix well. This reagent should be prepared fresh monthly.8.7 Potassium Hydrogen Phthalate, Primary Standard.8.8 Tetrabutylammonium Hy
34、droxide (Bu4NOH), 1M Solution in Methanol, 100 mL.8.9 Tetrabutylammonium Hydroxide (Titrant), 0.1 meq/mLPrepare by transferring the entire 100 mL of 1M Bu4NOH inmethanol (see 8.8) into a 1L1-L volumetric flask that is half filled with 2-propanol. Rinse the emptied bottle that contained thesolution i
35、n 8.8 and transfer the rinsings to the contents of the 1L1-L volumetric flask. Swirl contents and dilute to the mark with2-propanol. Stopper the flask and mix well. Finally, transfer the flask contents to the buret reservoir of a potentiometric autotitratorand standardize the titrate versus dried (2
36、 h, 120C) potassium hydrogen phthalate (KHP) as follows: dissolve approximately 0.18g of KHP, weighed to 0.1 mg, in about 60 mL of water contained in a 100-mL beaker. Stir several minutes to ensure completedissolution of the KHP. Perform a potentiometric titration directly on the KHP solution using
37、the 0.1 meq/mL Bu4NOH titrant.Perform three to five standardization titrations to obtain a reliable average value for the 0.1 meq/mL Bu4NOH concentration.N 5 KHP,g0.204233Bu4NOH,mL(2)where:N = concentration of the 0.1 meq/mL Bu4NOH expressed to four decimal places, andBu4NOH, mL = mL of this titrant
38、 to reach a potentiometric end point in the reaction with KHP.8.10 Methanol.8.11 Acetone.9. Hazards9.1 p-Toluenesulfonyl Isocyanate (TSI) is harmful by inhalation, in contact with skin and if swallowed. It may causesensitization by inhalation and skin contact. It reacts violently with water. It caus
39、es severe irritation. It is a Lachrymator. In caseof contact with eyes, rinse immediately with plenty of water and seek medical advice. Never add water to this product.5 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the tes
40、ting of reagents not listed bythe American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC),(USP), Rockville, MD.E1899 1639.2 Wear suitable protective c
41、lothing, gloves and eye/face protection when handling p-Toluenesulfonyl Isocyanate. Use only ina chemical fume hood. Do not breathe vapor. Do not get in eyes, on skin, or on clothing.10. Sampling10.1 Special precautions may be necessary to ensure that a representative sample is taken for analysis. G
42、eneral guidelines forsampling may be found in Practice E300. Samples which are solids at room temperature should be heated in a low temperatureoven to obtain a clear liquid prior to weighing. Low temperature (50 to 70C), should be tried first to avoid any undesirable changesin the sample. If higher
43、temperatures are required to melt the sample, for example, 110C, then the sample should be removed fromthe oven as soon as a clear liquid is obtained. After heating, invert the sample container twenty times to ensure completehomogenization. Samples that are liquid at room temperature only require in
44、version mixing.11. Procedure11.1 Tare a 100-mL glass or plastic beaker on an analytical balance and transfer a sample to the beaker using a glass or plastictransfer pipet. The optimum weight of sample is determined from the following relationship:sample,g5 40expected OH# (3)For expected OH# values o
45、f 2 or less, use 15 to 20 g of sample.11.2 Using a graduated cylinder or other volumetric dispenser, add 10 mL of acetonitrile. Then add a magnetic stirring bar andstir slowly on a magnetic stirrer until sample is dissolved (30 s is usually sufficient) (see Note 2).NOTE 2Although acetonitrile has be
46、en found to dissolve a wide range of sample types (and should be used where possible), tetrahydrofuran orpentene stabilized chloroform may be used as solvent for samples which may be insoluble in acetonitrile. Alternatively, 3 mL of toluene may be usedto dissolve a sample, followed immediately by ad
47、dition of 7 mLof acetonitrile. Superior potentiometric titration curves are obtained in acetonitrile media.If there are difficulties in titrating while using less polar solvents, one may need to demonstrate the operation of the standard electrode (Section 7.2) andconfirm its functionality under thes
48、e conditions. Substitution of a more solvent compatible potentiometric electrode can be considered.11.3 Pipet 10 6 0.1 mLof TSI reagent into the sample solution, cover beaker with a watch glass and stir slowly on the magneticstirrer for 5 min.11.4 Add 0.5 mL of water to destroy excess TSI reagent. S
49、tir for 1 min at slow speed.11.5 Add 30 mL of acetonitrile using a graduated cylinder or other volumetric dispenser.11.6 Using tissue paper, blot dry the end of the combination pH electrode and buret delivery tube tip. Immerse electrode andburet delivery tube tip into the sample solution, stir at a moderate speed, and begin the titration with 0.1 N standardized Bu4NOHsolution. Follow instruction manual for the autotitrator and be certain that all bubbles are expunged from the buret barrel anddelivery tip tubing before beginning the titration. As is the case
