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[jrzfcrmrnzr Uzlng Karl FKcher TK.ra'dnnz Steven K. MacLeod Control Division The Upjohn Company Kalamazoo, Ml 49001
Titration in protic media. The Karl Fischer reaction in protic media (i.e., alcohol) is shown below. 2ROH
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An accurate and precise moisture determination is often essential in resolving issues where water is involved. Water has been identified as a contaminant limiting the reactivity of products (e.g., monomers, various resins and coating materials, prepregs), a reactant limiting the lifetime of a material (e.g., halocarbons, acetylsalicylic acid), a medium for reaction between components in a mixture (e.g., pharmaceutical formulations), and as a factor limiting the accuracy of other measurements (e.g., mass balance). Although a number of chromatographic, spectroscopic, electronic, thermal, and wet chemical methods have been used to determine moisture, the Karl Fischer titration, originally described in 1935 (1), is the approach most widely used. This REPORT includes discussions of the reaction chemistry, side reactions, reagent composition, and experimental mechanics as well as the issues involved in assay development for the Karl Fischer titration.
Reaction chemistry The Karl Fischer titration has been extensively reviewed (2, 3). It has been suggested that different reactions occur, depending on the protic or aprotic nature of the medium (4, 5). 0003-2700/91/0363-557A/$02.50/0 1991 American Chemical Society ©
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