1、Designation: E 203 01Standard Test Method forWater Using Volumetric Karl Fischer Titration1This standard is issued under the fixed designation E 203; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb
2、er in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method is intended as a general guide for theap
3、plication of the volumetric Karl Fischer (KF) titration fordetermining free water and water of hydration in most solid orliquid organic and inorganic compounds. This test method isdesigned for use with automatic titration systems capable ofdetermining the KF titration end point amperometrically;howe
4、ver, a manual titration method for determining the endpoint visually is included as Appendix X1. Samples that aregaseous at room temperature are not covered (see AppendixX4). This test method covers the use of both pyridine andpyridine-free KF reagents for determining water by the volu-metric titrat
5、ion. Determination of water using KF coulometrictitration is not discussed. By proper choice of the sample size,KF reagent concentration and apparatus, this test method issuitable for measurement of water over a wide concentrationrange, that is, parts per million to pure water.1.2 This standard does
6、 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. Specific warningsare given in 3.1 an
7、d 7.3.3.1.3 Review the current Material Safety Data Sheets (MSDS)for detailed information concerning toxicity, first aid proce-dures, and safety precautions for chemicals used in this testprocedure.2. Referenced Documents2.1 A list of existing ASTM Karl Fischer methods, theirapplications to various
8、products, and the sponsoring commit-tees is given in Appendix X3.2.2 ASTM Standards:D 789 Test Methods for Determination of Relative Viscos-ity, and Moisture Content of Polyamide (PA)2D 803 Test Methods for Testing Tall Oil3D 890 Test Method for Water in Liquid Naval Stores3D 1123 Test Methods for W
9、ater in Engine Coolant Concen-trate by the Karl Fischer Reagent Method4D 1152 Specification for Methanol (Methyl Alcohol)5D 1193 Specification for Reagent Water6D 1348 Test Methods for Moisture in Cellulose3D 1364 Test Method for Water in Volatile Solvents (FischerReagent Titration Method)5D 1533 Te
10、st Method for Water in Insulating Liquids byCoulometric Karl Fischer Titration7D 1568 Test Methods for Sampling and Chemical Analysisof Alkylbenzene Sulfonates8D 1631 Test Method for Water in Phenol and RelatedMaterials by the Iodine Reagent Method5D 2072 Test Method for Water in Fatty Nitrogen Com-
11、pounds3D 2575 Method for Testing Polymerized Fatty Acids3D 3277 Test Methods for Moisture Content of Oil-Impregnated Cellulosic Insulation7D 3401 Test Methods for Water in Halogenated OrganicSolvents and Their Adixtures9D 4017 Test Method for Water in Paints and Paint Materialsby Karl Fischer Method
12、10D 4377 Test Method for Water in Crude Oils by Potentio-metric Karl Fischer Titration11D 4672 Test Methods for Polyurethane Raw Materials-Determination of Water Content of Polyols12D 4928 Test Methods for Water in Crude Oils by Coulom-etric Karl Fischer Titration131This test method is under the jur
13、isdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and is the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved Oct. 10, 2001. Published December 2001. Originallypublished as E 203 62 T. Last previous edition E 203 96.2Annual Book of ASTM Sta
14、ndards, Vol 08.01.3Annual Book of ASTM Standards, Vol 06.03.4Annual Book of ASTM Standards, Vol 15.05.5Annual Book of ASTM Standards, Vol 06.04.6Annual Book of ASTM Standards, Vol 11.01.7Annual Book of ASTM Standards, Vol 10.03.8Annual Book of ASTM Standards, Vol 15.04.9Annual Book of ASTM Standards
15、, Vol 15.05.10Annual Book of ASTM Standards, Vol 06.01.11Annual Book of ASTM Standards, Vol 05.02.12Annual Book of ASTM Standards, Vol 08.03.13Annual Book of ASTM Standards, Vol 05.03.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D
16、 5460 Test Method for Rubber Compounding Materials-Water in Rubber Additives14D 5530 Test Method for Total Moisture of Hazardous WasteFuel by Karl Fischer Titrimetry15D 6304 Test Method for Determination of Water in Petro-leum Products, Lubricating Oils, and Additives by Coulo-metric Karl Fisher Tit
17、ration8E 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial Chemicals9E 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis9E 1064 Test Method for Water in Organic Liquids byCoulometric Karl
18、Fischer Titration93. 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 withKF reagent, which consists of iodine, sulfur dioxide, organicbase, and a solvent (typically an alcohol, such as methanol,ethylene glycol,
19、 or 2-methoxyethanol). The titration end pointis determined amperometrically with a platinum electrodewhich senses a sharp change in cell resistance when the iodineis reduced by sulfur dioxide in the presence of water.(WarningKF reagent contains four toxic compounds,namely, iodine, sulfur dioxide, p
20、yridine or other organic bases,and methanol or glycol ether. The reagent should be dispensedin a well-ventilated area. Care must be exercised to avoidinhalation of the reagent or direct contact of the reagent withthe skin.)3.2 The general equation to this reaction is as follows:H2O 1 I21 SO21 R8OH 1
21、 3 RN . RNH!SO4R8 1 2RNH!I (1)where:RN = an organic base such as pyridine, andR8OH = alcohol.4. Significance and Use4.1 Titration techniques using KF reagent are one of themost widely used for the determination of water.4.2 Although the volumetric KF titration can determine lowlevels of water, it is
22、 generally accepted that coulometric KFtitrations (see Test Method E 1064) are more accurate forroutine determination of very low levels of water. As a generalrule, if samples routinely contain water concentrations of 500ppm or less, the coulometric technique should be considered.4.3 Applications ca
23、n be subdivided into two sections: (1)organic and inorganic compounds, in which water may bedetermined directly, and (2) compounds, in which water cannotbe determined directly, but in which interferences may beeliminated by suitable chemical reactions or modifications ofthe procedure. Further discus
24、sion of interferences is includedin Section 5 and Appendix X2.4.4 Water can be determined directly in the presence of thefollowing types of compounds:Organic CompoundsAcetals EthersAcids (Note 1) HalidesAcyl halides Hydrocarbons (saturated and unsaturated)Alcohols Ketones, stable (Note 4)Aldehydes,
25、stable (Note 2) NitrilesAmides OrthoestersAmines, weak (Note 3) Peroxides (hydro, dialkyl)Anhydrides SulfidesDisulfides ThiocyanatesEsters ThioestersInorganic CompoundsAcids (Note 5) Cupric oxideAcid oxides (Note 6) DesiccantsAluminum oxides Hydrazine sulfateAnhydrides Salts of organic and inorganic
26、 acids (Note 6)Barium dioxideCalcium carbonateNOTE 1Some acids, such as formic, acetic, and adipic acid, are slowlyesterified. For high accuracy with pyridine-based reagents, use 30 to 50 %pyridine in methanol as the solvent. When using pyridine-free reagents,commercially available buffer solutions1
27、6can be added to the sample priorto titration. With formic acid, it may be necessary to use methanol-freesolvents and titrants (1).17NOTE 2Examples of stable aldehydes are formaldehyde, sugars,chloral, etc. Formaldehyde polymers contain water as methylol groups.This combined water is not titrated. A
28、ddition of an excess of NaOCH3inmethanol permits release and titration of this combined water, afterapproximate neutralization of excess base with acetic acid (see Note 9).NOTE 3Weak amines are considered to be those with Kbvalue2.4 3 105. Use salicylic acid-methanol solution (Section 7). Glacialace
29、tic acid is applicable in certain cases.NOTE 9Addition of acetic acid eliminates the interference.NOTE 10Ferric fluoride does not interfere. Reaction with8-hydroxyquinoline is reported to eliminate this interference (3).NOTE 11With pyridine-based reagent, add1MSO2in 1 + 1 pyridine-methanol or spent
30、KF reagent. With pyridine-free reagents, the twocomponent reagent methods should be used and 1 mL of sulfuric acid isadded to the solvent prior to titration (Note 15).NOTE 12Olefin addition reaction eliminates interferences (2). Oxida-tion with neutral iodine solution eliminates the interference of
31、mercaptans(4).NOTE 13Sulfuric acid, above 92 %. Add the sample (10 g) to a largeexcess of pyridine (35 mL), swirl to dissolve precipitate, and titrate.Addition of 8 mL of 1 + 1 pyridine-dioxane/1 g of sample also issatisfactory, maintaining a homogeneous solution throughout the titration.5.3 If ther
32、e is a question of compounds listed in 5.2 causingan interference, the recovery of spiked additions of water to thesample matrix should be checked.5.4 Many materials react stoichiometrically with KF re-agent. When their concentration is known, suitable correctionscan be applied. A list of such mater
33、ials is given in AppendixX2.6. Apparatus6.1 Karl Fischer Volumetric Titrator,18consisting of a titra-tion cell, dual platinum electrode, magnetic stirrer, dispensingburet and control unit. Many manufacturers of general purposelaboratory titrators offer optional accessories that allow theirinstrument
34、 to perform KF titrations.7. Reagents7.1 Purity of ReagentsUse reagent grade chemicals in alltests. Unless otherwise indicated, all reagents shall conform tothe specifications of the Committee on Analytical Reagents ofthe American Chemical Society19where such specifications areavailable. Other grade
35、s may be used, provided it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the determi-nation.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall mean reagent water as defined by Type II and IIIof Specificatio
36、n D 1193.7.3 Karl Fischer ReagentsTraditionally, pyridine was theorganic base used in KF reagents. Pyridine-free formulations,however, are available now and are preferred by most KFinstrument manufacturers for use with their equipment. Thesereagents are less toxic, less odorous, and more stable than
37、 thosecontaining pyridine. The use of pyridine-free reagents isrecommended whenever possible.7.3.1 Pyridine-Free Karl Fischer TitrantTypically con-sists 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,
38、 2.00, and 5.00 mg H2O/mL can becommercially obtained.7.3.2 Pyridine-Free Karl Fischer Solvent20Anhydrousmethanol is the most frequently used solvent, however, otheralcohols including glycols and glycol ethers are used. Somecommercially available solvents also contain an organic baseand sulfur dioxi
39、de.7.3.3 Karl Fischer Reagent Containing PyridineThe KFreagent may be either prepared in the laboratory or purchased.Two types of reagent are commonly used. Directions forpreparing these and diluting if necessary, along with commer-cial sources of supply, are as follows: (WarningFollowstandard preca
40、utions for handling toxic gases in preparing thereagents (1)or(2) as described in 7.3.3.1 and 7.3.3.2. Carry outall operations in a hood. Wear rubber gloves and a face shieldwhen handling pyridine and sulfur dioxide and when mixingchemicals. Special precautions must be observed when dis-pensing sulf
41、ur dioxide to prevent drawback of the solution intothe gas cylinder, which might cause an explosion. This is bestaccomplished by placing a trap in the line between the gascylinder and absorption vessel.)7.3.3.1 Karl Fischer Reagent (Ethylene Glycol MonomethylEther Solution,1mL=6mgH2O) (2)For each li
42、tre ofsolution, dissolve 133 6 1 g iodine in 425 6 5 mL of pyridinein a dry glass-stoppered bottle. Add 425 6 5 mL of ethyleneglycol monomethyl ether. Cool to below 4C in an ice bath.Bubble 102 to 105 g of gaseous sulfur dioxide (SO2) into thecooled mixture. Determine the amount of SO2added by thech
43、ange in weight of the SO2cylinder or the increase in volume(about 70 mL) of the reagent mixture. Alternatively, add about70 mL of freshly drawn liquid SO2in small increments. Mixwell and set aside for at least 12 h before using. (Warningsee 7.3.3.)7.3.3.2 Karl Fischer Reagent (Methanol Solution,1mL=
44、6mg H2O)For each litre of solution, dissolve 133 6 1gofiodine in 4256 5 mL of pyridine in a dry, glass-stopperedbottle. Add 425 6 5 mL of methanol. Cool the mixture in anice bath to below 4C. Bubble 102 to 105 g of gaseous sulfurdioxide (SO2) into the cooled mixture. Determine the amountof SO2added
45、by the change in weight of the SO2cylinder orthe increase in volume (about 70 mL) of the reagent mixture.Alternatively, add about 70 mL of freshly drawn liquid SO2insmall increments. Mix well and set aside for at least 12 hbefore using. (Warningsee 7.3.3.)7.3.3.3 Karl Fischer Reagent (Ethylene Glyco
46、l MonomethylSolution, Stabilized,1mL=6mgH2O).21,227.3.3.4 Karl Fischer Reagent, DilutePrepare more dilute18Automatic volumetric titrators specifically designed for KF determinations aremanufactured by many different companies. Models are available from EM Science,Metrohm, Mettler, Photovolt, Mitsubi
47、shi, and others.19Reagent 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., and the United
48、States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.20Pyridine-free KF reagents can be purchased from Cresent Chemical, JT Baker,EM Science, GFS Chemicals, and others.21Fisher Scientific Co., Catalog No. SK 3-500 has been found satisfactory forthis pur
49、pose.22Mallinckrodt Catalog No. 5651 has been found satisfactory for this purpose.E 2033solutions of the KF reagent by diluting with the proper solventas follows:Desired Strength, mg H2O/mL Litres of Diluent to Add/litre of 6 mg/mL KF reagent3 0.852 1.61 3.20.5 5.7These dilute solutions cannot be prepared by simple propor-tion, since water added with the diluent must be accounted for.The volumes to add, indicated above, are calculated assumingthe diluent contains 0.05 % water.7.4 Methanol, Standard (1 mL = 1 mg H2O)23This solu-tion can be stored conveniently
