The Scope of Application of the Karl Fischer Method

The Karl Fischer method can be used for a wide range of substances. However, this method relies on iodometric determination of the reaction between Karl Fischer reagent and water. Therefore, if the sample contains species that react with elemental iodine, the result will show a positive error, and if the sample contains species that produces elemental iodine by oxidation of iodine compounds, the result will show a negative error. The following table lists substances that can be directly titrated with Karl Fischer reagent, substances that cannot be directly titrated but can be titrated by adjustment according to the appropriate chemical reaction or process, and substances that react with Karl Fischer reagent and are not suitable for direct titration. Even if a substance cannot be titrated directly, its moisture content can be measured by indirect methods such as water vaporization.

Directly Titratable Compounds

Organic Compound

Hydrocarbons (saturated, unsaturated compounds)

Alcohols, polyols, phenols, ethers

Inert ketones (di-isopropyl ketone, etc.)

Inert aldehydes (formaldehyde, chloral, etc.)

Organic Acids, Hydroxy Acids, Amino Acids

Anhydride

Esters, lactones, inorganic acid esters

Amines (proteins, amides, anilines)

Nitriles, cyanides, cyanic acid derivatives

Nitro compounds, oximes, hydroxamic acids

Thiocyanates, thioethers, thioesters

Halogenated hydrocarbon, haloacyl

Sugars, organic salts and their hydrates

Inorganic Compound

Inorganic salts and their hydrates

Inorganic acid

Chelating compound

fertilizer

calcium carbonate

Polytungsten salt

Compounds That Have Been Specially Treated or Can Be Directly Titrated Under Certain Conditions

Although it is stated in previous references that these compounds can be directly titrated by the following treatment, it is necessary to check the following compounds.

Compounds that react with Karl Fischer reagents and cannot be directly titrated

organic compound

Ascorbic acid, diacyl peroxide

peracid, quinone

Inorganic compound

Sodium Sulfide, Sodium Peroxide

Chromate, dichromate

Iron oxide, nickel oxide, arsenic trioxide

Arsenate, arsenite, borate, boron oxide

bicarbonate, carbonate

metal hydroxide, metal oxide

Sulfites, Pyrosulfites

Sodium Nitrite, Thiosulfate

copper salt, stannous salt