Karl Fischer & Potentiometric Titration Application Library
Drugs and Medicines – KF Coulometry, Thiamine Chloride Hydrochloride and Folic Acid | Karl Fischer titrator AQ-300/MOICO-A19
Water contents of drugs and medicines could be determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
When the moisture content is relatively high at the% level, the amount of sample added is as small as a few 10 mg. If the sample is in powder form, taking and adding samples with an “ultra-micro solid sampler” makes measurement easy and accurate. An example for water contents measurements of thiamine chloride hydrochloride and folic acid performed by with ultra-micro solid sampler are introduced here. The measurement method was determined with reference to Japanese Pharmacopeia. Reference
1) Japanese Pharmacopoeia Seventeenth Edition
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
When the moisture content is relatively high at the% level, the amount of sample added is as small as a few 10 mg. If the sample is in powder form, taking and adding samples with an “ultra-micro solid sampler” makes measurement easy and accurate. An example for water contents measurements of thiamine chloride hydrochloride and folic acid performed by with ultra-micro solid sampler are introduced here. The measurement method was determined with reference to Japanese Pharmacopeia. Reference
1) Japanese Pharmacopoeia Seventeenth Edition
Oil products – Fuel oil | Karl Fischer titrator AQ-300/MOICO-A19/EV-2000L
Water content of oil products are determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Generally the fuel oil does not interfere the Karl Fischer reaction and direct injection method could apply. Suitable anode solution is selected for dissolving oil samples.
It is known that some of the oil additives interfere Karl Fischer reaction. In that case, azeotropic distillation method with Oil evaporator is appropriate. Water is separated from oil sample by distillation and introduced to electrolytic cell with carrier gas.
ASTM D6304 : Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Generally the fuel oil does not interfere the Karl Fischer reaction and direct injection method could apply. Suitable anode solution is selected for dissolving oil samples.
It is known that some of the oil additives interfere Karl Fischer reaction. In that case, azeotropic distillation method with Oil evaporator is appropriate. Water is separated from oil sample by distillation and introduced to electrolytic cell with carrier gas.
ASTM D6304 : Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration
Nitriles | Karl Fischer titrator AQ-300/MOICO-A19
Water content of Nitriles could be determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Nitriles do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General use of anode solution contain methanol as solvent. When the sample like a long chain hydrocarbon has poor solubility in methanol, anode solution containing chloroform or hexanol or toluene is used.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Nitriles do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General use of anode solution contain methanol as solvent. When the sample like a long chain hydrocarbon has poor solubility in methanol, anode solution containing chloroform or hexanol or toluene is used.
Amines | Karl Fischer titrator AQ-300/MOICO-A19
Water content of amines could be determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
The amines change anode solution pH to basic. In the case of an amine with stronger basicity than benzylamine (pKa = 9.34¹)) as a guideline, there are such effects as the end point becomes unclear. Therefore, when measuring a strongly basic amine, add a neutralizing agent to the anode solution beforehand to suppress the influence of undesirable effect caused by adding the sample. This application introduces an example for the water determination in cyclohexylamine(liquid), diethanolamine(liquid) and imidazole(solid). Reference
1) H. K. Hall, J. Am. Chem. Soc. (1957) 79 5441.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
The amines change anode solution pH to basic. In the case of an amine with stronger basicity than benzylamine (pKa = 9.34¹)) as a guideline, there are such effects as the end point becomes unclear. Therefore, when measuring a strongly basic amine, add a neutralizing agent to the anode solution beforehand to suppress the influence of undesirable effect caused by adding the sample. This application introduces an example for the water determination in cyclohexylamine(liquid), diethanolamine(liquid) and imidazole(solid). Reference
1) H. K. Hall, J. Am. Chem. Soc. (1957) 79 5441.
Ethers and Esters | Karl Fischer titrator AQ-300/MOICO-A19
Water content of Ethers and Esters are determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Ethers and esters do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected from General-use or Oil in accordance with sample solubility. General-use anode solution contains methanol as solvent. When the sample has low solubility in methanol, the use of anode solution for oil is appropriate. One exception is a sample containing vinyl group, which reacts with KF reagent and interferes the titration. When fritless cell is used, cathode solution is not necessary.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Ethers and esters do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected from General-use or Oil in accordance with sample solubility. General-use anode solution contains methanol as solvent. When the sample has low solubility in methanol, the use of anode solution for oil is appropriate. One exception is a sample containing vinyl group, which reacts with KF reagent and interferes the titration. When fritless cell is used, cathode solution is not necessary.
Oil products | Karl Fischer titrator AQ-300/MOICO-A19/EV-2000L
Water content of Oil products are determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Kerosene and diesel oil do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution for Oil is selected to dissolve samples.
It is known that some of the oil additives interfere Karl Fischer reaction. In that case, azeotropic distillation method with Oil evaporator is appropriate. Water is separated from oil sample by distillation and introduced to electrolytic cell with carrier gas.
Mercaptanes and hydrogen sulfide in oil interfere Karl Fischer reaction. Since these side reactions occur quantitatively, water content result could be corrected with concentration of mercaptanes and hydrogen sulfide. 1 ppm of mercaptanes or hydrogen sulfide lead 0.3 ppm or 0.6 ppm higher water content respectively.
ASTM D6304 : Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration
ASTM E1064 : Standard Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titration
ASTM D4928 : Standard Test Method for Water in Crude Oils by Coulometric Karl Fischer Titration
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Kerosene and diesel oil do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution for Oil is selected to dissolve samples.
It is known that some of the oil additives interfere Karl Fischer reaction. In that case, azeotropic distillation method with Oil evaporator is appropriate. Water is separated from oil sample by distillation and introduced to electrolytic cell with carrier gas.
Mercaptanes and hydrogen sulfide in oil interfere Karl Fischer reaction. Since these side reactions occur quantitatively, water content result could be corrected with concentration of mercaptanes and hydrogen sulfide. 1 ppm of mercaptanes or hydrogen sulfide lead 0.3 ppm or 0.6 ppm higher water content respectively.
ASTM D6304 : Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration
ASTM E1064 : Standard Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titration
ASTM D4928 : Standard Test Method for Water in Crude Oils by Coulometric Karl Fischer Titration
Aromatic Hydrocarbon | Karl Fischer titrator AQ-300/MOICO-A19
Water content of Aromatic hydrocarbons are determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Aromatic hydrocarbons do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected from General-use or Oil in accordance with sample solubility. General-use anode solution contains methanol as solvent. When the sample has low solubility in methanol, the use of anode solution for oil is appropriate. When fritless cell is used, cathode solution is not necessary.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Aromatic hydrocarbons do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected from General-use or Oil in accordance with sample solubility. General-use anode solution contains methanol as solvent. When the sample has low solubility in methanol, the use of anode solution for oil is appropriate. When fritless cell is used, cathode solution is not necessary.
Alcohols | Karl Fischer titrator AQ-300/MOICO-A19
Water content of Alcohols is determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Alcohols do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General-use anode solution contains methanol as solvent. Alcohols with long carbon chain have low solubility in methanol. In that case, use of anode solution for oil is appropriate.
When fritless cell is used, cathode solution is not necessary.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Alcohols do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General-use anode solution contains methanol as solvent. Alcohols with long carbon chain have low solubility in methanol. In that case, use of anode solution for oil is appropriate.
When fritless cell is used, cathode solution is not necessary.
Hydrocarbon, Halogenated hydrocarbon | Karl Fischer titrator AQ-300/MOICO-A19
Water content of hydrocarbon and halogenated hydrocarbon could be determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Hydrocarbon and halogenated hydrocarbon do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General use of anode solution contain methanol as solvent. When the sample like a long chain hydrocarbon have poor solubility in methanol, anode solution containing chloroform or hexanol or toluene is used. When fritless cell is used, cathode solution is not necessary.
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Hydrocarbon and halogenated hydrocarbon do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General use of anode solution contain methanol as solvent. When the sample like a long chain hydrocarbon have poor solubility in methanol, anode solution containing chloroform or hexanol or toluene is used. When fritless cell is used, cathode solution is not necessary.
Determination of chloride ion in concrete | Autotitrator COM-A19
This report introduces an example of the determination of chloride ion in concrete. This measurement method is described in “Potentiometric titration method using chloride ion-selective electrode” of “JIS A 1154 Method of test for chloride ion content in hardened concrete”. Nitric acid is added to adjust the pH to 3 or less, and extract chloride ion with boiling. Cool to room temperature, filtrate to separate undissolved component and collect filtrated solution as sample. Chloride ion is determined by precipitation titration using a silver nitrate standard solution.
Determination of chloride ion in cement | Autotitrator COM-A19
This report introduces an example of the determination of chloride ion in cement. This measurement method is described in “Method for measuring chloride” of “Japanese industrial standard JIS R 5202 Method for chemical analysis of cements”. The sample is dissolved in nitric acid, a chloride ion standard solution and a hydrogen peroxide solution are added, and the sample is heat-treated, and then the measurement is performed by precipitation titration using a silver nitrate standard solution. The measurements are made by potentiometric titration using a chloride ion-selective electrode as the electrode for end point detection.
Determination of isocyanate (NCO) content in adhesives | Autotitrator COM-A19
Synthetic adhesives like hydrophilic macromolecule –Isocyanate type wood adhesives are consisted of base compound and cross-linker; the principal components of base compound are macromolecule aqueous solution or aqueous dispersing element, or those combination. The principal components of cross-linker is isocyanate compounds. The measurement procedure of isocyanate (NCO) content described in this report is standardized by JIS K 6806. NCO content is determined by the neutralization titration which excess di-n-butylamine is titrated with hydrochloric acid standard solution after sample and di-n-butylamine are mixed and reacted. A measurement example of potentiometric titration for NCO determination is introduced in this report.
ASTM D5155 : Standard Test Methods for Polyurethane Raw Materials: Determination of the Isocyanate Content of Aromatic Isocyanates
ASTM D5155 : Standard Test Methods for Polyurethane Raw Materials: Determination of the Isocyanate Content of Aromatic Isocyanates
