1、Designation: E203 08E203 16Standard Test Method forWater Using Volumetric Karl Fischer Titration1This standard is issued under the fixed designation E203; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 This test method is intended as a general guide
3、 for the application of the volumetric Karl Fischer (KF) titration fordetermining free water and water of hydration in most solid or liquid organic and inorganic compounds. This test method isdesigned for use with automatic titration systems capable of determining the KF titration end point potentio
4、metrically; however,a manual titration method for determining the end point visually is included as Appendix X1. Samples that are gaseous at roomtemperature are not covered (see Appendix X4). This test method covers the use of both pyridine and pyridine-free KF reagentsfor determining water by the v
5、olumetric titration. Determination of water using KF coulometric titration is not discussed. By properchoice of the sample size, KF reagent concentration and apparatus, this test method is suitable for measurement of water over awide concentration range, that is, parts per million to pure water.1.2
6、The values stated in SI units are to be regarded as standard.1.3 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 applicab
7、ility of regulatorylimitations prior to use. Specific warnings are given in 3.1 and 7.3.3.1.4 Review the current Material Safety Data Sheets (MSDS)(SDS) for detailed information concerning toxicity, first aidprocedures, and safety precautions for chemicals used in this test procedure.2. Referenced D
8、ocuments2.1 A list of existing ASTM Karl Fischer methods, their applications to various products, and the sponsoring committees isgiven in Appendix X3.2.2 ASTM Standards:2D789 Test Methods for Determination of Solution Viscosities of Polyamide (PA)D803 Test Methods for Testing Tall OilD890 Test Meth
9、od for Water in Liquid Pine ChemicalsD1123 Test Methods for Water in Engine Coolant Concentrate by the Karl Fischer Reagent MethodD1152 Specification for Methanol (Methyl Alcohol)D1193 Specification for Reagent WaterD1348 Test Methods for Moisture in CelluloseD1364 Test Method for Water in Volatile
10、Solvents (Karl Fischer Reagent Titration Method)D1533 Test Method for Water in Insulating Liquids by Coulometric Karl Fischer TitrationD1568 Test Methods for Sampling and Chemical Analysis of Alkylbenzene SulfonatesD1631 Test Method for Water in Phenol and Related Materials by the Iodine Reagent Met
11、hodD2072 Test Method for Water in Fatty Nitrogen Compounds (Withdrawn 2007)3D2575 Methods of Testing Polymerized Fatty Acids (Withdrawn 2007)3D3277 Test Methods for Moisture Content of Oil-Impregnated Cellulosic Insulation (Withdrawn 2010)3D3401 Test Methods for Water in Halogenated Organic Solvents
12、 and Their Admixtures1 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 Oct. 1, 2008April 1, 2016. Published November 2008May 2016. Originally ap
13、proved in 1962 as E203 62 T. Last previous edition approvedin 20012008 as E203 01.E203 08. DOI: 10.1520/E0203-08.10.1520/E0203-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume informati
14、on, refer to the standards Document 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 t
15、o the previous version. Becauseit 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 Summ
16、ary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D4017 Test Method for Water in Paints and Paint Materials by Karl Fischer MethodD4377 Test Method for Water in Crude Oils by Pot
17、entiometric Karl Fischer TitrationD4672 Test Method for Polyurethane Raw Materials: Determination of Water Content of PolyolsD4928 Test Method for Water in Crude Oils by Coulometric Karl Fischer TitrationD5460 Test Method for Rubber Compounding MaterialsWater in Rubber AdditivesD5530 Test Method for
18、 Total Moisture of Hazardous Waste Fuel by Karl Fischer TitrimetryD6304 Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric KarlFischer Titration (Withdrawn 2016)3E180 Practice for Determining the Precision of ASTM Methods for Analysis and Tes
19、ting of Industrial and Specialty Chemicals(Withdrawn 2009)3E1064 Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titration3. Summary of Test Method3.1 The sample, containing a maximum of 100 mg of water, is dissolved or dispersed in a suitable liquid and titrated with KFreagent,
20、 which consists of iodine, sulfur dioxide, organic base, and a solvent (typically an alcohol, such as methanol, ethyleneglycol, or 2-methoxyethanol). The titration end point is determined potentiometrically with a platinum electrode which senses asharp change in cell resistance when the iodine is re
21、duced by sulfur dioxide in the presence of water. (WarningKF reagentcontains four toxic compounds, namely, iodine, sulfur dioxide, pyridine or other organic bases, and methanol or glycol ether. Thereagent should be dispensed in a well-ventilated area. Care must be exercised to avoid inhalation of th
22、e reagent or direct contactof the reagent with the skin.Warning)KF reagent contains four toxic compounds, namely, iodine, sulfur dioxide, pyridine or otherorganic bases, and methanol or glycol ether. The reagent should be dispensed in a well-ventilated area. Care must be exercised toavoid inhalation
23、 of the reagent or direct contact of the reagent with the skin.)3.2 The general equation to this reaction is as follows:H2O1I21SO21ROH13RN.RNH!SO4R12RNH!I (1)where:RN = an organic base such as pyridine, andROH = alcohol.4. Significance and Use4.1 Titration techniques using KF reagent are one of the
24、most widely used for the determination of water.4.2 Although the volumetric KF titration can determine low levels of water, it is generally accepted that coulometric KFtitrations (see Test Method E1064) are more accurate for routine determination of very low levels of water. As a general rule, ifsam
25、ples routinely contain water concentrations of 500 mg/kg or less, the coulometric technique should be considered.4.3 Applications can be subdivided into two sections: (1) organic and inorganic compounds, in which water may be determineddirectly, and (2) compounds, in which water cannot be determined
26、 directly, but in which interferences may be eliminated bysuitable chemical reactions or modifications of the procedure. Further discussion of interferences is included in Section 5 andAppendix X2.4.4 Water can be determined directly in the presence of the following types of compounds:Organic Compou
27、ndsAcetals EthersAcids (Note 1) HalidesAcyl halides Hydrocarbons (saturated and unsaturated)Alcohols Ketones, stable (Note 4)Aldehydes, stable (Note 2) NitrilesAmides OrthoestersAmines, weak (Note 3) Peroxides (hydro, dialkyl)Anhydrides SulfidesDisulfides ThiocyanatesEsters ThioestersInorganic Compo
28、undsAcids (Note 5) Cupric oxideAcid oxides (Note 6) DesiccantsAluminum oxides Hydrazine sulfateAnhydrides Salts of organic and inorganic acids (Note 6)Barium dioxideCalcium carbonateNOTE 1Some acids, such as formic, acetic, and adipic acid, are slowly esterified. For high accuracy with pyridine-base
29、d reagents, use 30 to 50 %pyridine in methanol as the solvent. When using pyridine-free reagents, commercially available buffer solutions can be added to the sample prior toE203 162titration. With formic acid, it may be necessary to use methanol-free solvents and titrants (1).4NOTE 2Examples of stab
30、le aldehydes are formaldehyde, sugars, chloral, etc. Formaldehyde polymers contain water as methylol groups. Thiscombined water is not titrated. Addition of an excess of NaOCH3 in methanol permits release and titration of this combined water, after approximateneutralization of excess base with aceti
31、c acid (see Note 9).NOTE 3Weak amines are considered to be those with Kb value 2.4 105. Use salicylic acid-methanol solution (Section 7). Glacial acetic acid isapplicable in certain cases.NOTE 9Addition of acetic acid eliminates the interference.NOTE 10Ferric fluoride does not interfere. Reaction wi
32、th 8-hydroxyquinoline is reported to eliminate this interference (3).NOTE 11With pyridine-based reagent, add 1 mol/L SO2 in 1 + 1 pyridine-methanol or spent KF reagent. With pyridine-free reagents, the twocomponent reagent methods should be used and 1 mL of sulfuric acid is added to the solvent prio
33、r to titration (Note 15).NOTE 12Olefin addition reaction eliminates interferences (2). Oxidation with neutral iodine solution eliminates the interference of mercaptans (4).NOTE 13Sulfuric acid, above 92 %. Add the sample (10 g) to a large excess of pyridine (35 mL), swirl to dissolve precipitate, an
34、d titrate. Additionof 8 mL of 1 + 1 pyridine-dioxane/1 g of sample also is satisfactory, maintaining a homogeneous solution throughout the titration.5.3 If there is a question of compounds listed in 5.2 causing an interference, the recovery of spiked additions of water to thesample matrix should be
35、checked.5.4 Many materials react stoichiometrically with KF reagent. When their concentration is known, suitable corrections can beapplied. A list of such materials is given in Appendix X2.6. Apparatus6.1 Karl Fischer Volumetric Titrator,5 consisting of a titration cell, dual platinum electrode, mag
36、netic stirrer, dispensing buretand control unit. Many manufacturers of general purpose laboratory titrators offer optional accessories that allow their instrumentto perform KF titrations.7. Reagents7.1 Purity of ReagentsUse reagent grade chemicals in all tests. Unless otherwise indicated, all reagen
37、ts shall conform to thespecifications of the Committee onAnalytical Reagents of theAmerican Chemical Society6 where such specifications are available.Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use withoutlessening the accu
38、racy of the determination.7.2 Purity of WaterUnless otherwise indicated, references to water shall mean reagent water as defined by Type II and III ofSpecification D1193.4 The boldface numbers in parentheses refer to the list of references at the end of this test method.5 Automatic volumetric titrat
39、ors specifically designed for KF determinations are manufactured by many different companies. Models are available from EM Science,Metrohm, Mettler, Photovolt, Mitsubishi, and others.6 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggest
40、ions on the testing of reagents not listed bythe American Chemical Society, see Analar 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.E203 1637.3 Karl Fischer
41、 ReagentsTraditionally, pyridine was the organic base used in KF reagents. Pyridine-free formulations,however, are available now and are preferred by most KF instrument manufacturers for use with their equipment. These reagentsare less toxic, less odorous, and more stable than those containing pyrid
42、ine. The use of pyridine-free reagents is recommendedwhenever possible.7.3.1 Pyridine-Free Karl Fischer TitrantTypically consists of a mixture of an organic base, sulfur dioxide and iodinedissolved in a solvent such as methanol or 2-methoxyethanol. Reagents with titers of 1.00, 2.00, and 5.00 mg H2O
43、/mL can becommercially obtained.7.3.2 Pyridine-Free Karl Fischer SolventSolventAnhydrous methanol is the most frequently used solvent, however, otheralcohols including glycols and glycol ethers are used. Some commercially available solvents also contain an organic base andsulfur dioxide.7.3.3 Karl F
44、ischer Reagent Containing PyridineThe KF reagent may be either prepared in the laboratory or purchased. Twotypes of reagent are commonly used. Directions for preparing these and diluting if necessary, along with commercial sources ofsupply, are as follows: (WarningFollow standard precautions for han
45、dling toxic gases in preparing the reagents (1) or (2) asdescribed in 7.3.3.1 and 7.3.3.2. Carry out all operations in a hood. Wear rubber gloves and a face shield when handling pyridineand sulfur dioxide and when mixing chemicals. Special precautions must be observed when dispensing sulfur dioxide
46、to preventdrawback of the solution into the gas cylinder, which might cause an explosion. This is best accomplished by placing a trap in theline between the gas cylinder and absorption vessel.WarningFollow standard precautions for handling toxic gases in preparingthe reagents (1) or (2) as described
47、 in 7.3.3.1 and 7.3.3.2. Carry out all operations in a hood. Wear rubber gloves and a face shieldwhen handling pyridine and sulfur dioxide and when mixing chemicals. Special precautions must be observed when dispensingsulfur dioxide to prevent drawback of the solution into the gas cylinder, which mi
48、ght cause an explosion. This is best accomplishedby placing a trap in the line between the gas cylinder and absorption vessel.)7.3.3.1 Karl Fischer Reagent (Ethylene Glycol Monomethyl Ether Solution, 1 mL = 6 mg H2O) (2)For each litre of solution,dissolve 133 6 1 g iodine in 425 6 5 mL of pyridine i
49、n a dry glass-stoppered bottle. Add 425 6 5 mL of ethylene glycolmonomethyl ether. Cool to below 4C in an ice bath. Bubble 102 to 105 g of gaseous sulfur dioxide (SO2) into the cooled mixture.Determine the amount of SO2 added by the change in weight of the SO2 cylinder or the increase in volume (about 70 mL) of thereagent mixture. Alternatively, add about 70 mL of freshly drawn liquid SO2 in small increments. Mix well and set aside for atleast 12 h before using. (Warningsee 7.3.3.Warning) see 7.3.3.)7.3.3.2 Karl Fischer Reagent (Methanol Solut
