Karl Fischer & Potentiometric Titration Application Library
Ketones, Cyclohexanone – KF Coulometry, Cooled direct injection, Azeotropic distillation | Karl Fischer titrator AQ-300/MOICO-A19/EV-2000L
Water content of cyclohexanone 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⁻
Ketones and aldehydes would interfere the Karl Fischer reaction by side-reaction with methanol (formula (1)).
R₂CO + 2CH₃OH → R₂C(OCH₃)₂ + H₂O ・・・(1)
Therefore it is necessary to use methanol-free anode and cathode solution. There are commercially available reagents with a special composition for ketones and aldehydes. However, cyclohexanone has particularly a strong side reaction activity, so it is difficult to measure by direct injection method at room temperature. In the measurement of cyclohexanone, it is effective to lower the activity of side reaction by cooling or to separate cyclohexanone and water by distillation.
This application introduces an example for the water determination in cyclohexanone with cooled direct injection method and azeotropic distillation method
H₂O ＋ I₂ ＋ SO₂ ＋ 3RN ＋ CH₃OH → 2RN・HI ＋ RN・HSO₄CH₃
2RN・HI → I₂ ＋ 2RN ＋ 2H⁺ ＋ 2e⁻
Ketones and aldehydes would interfere the Karl Fischer reaction by side-reaction with methanol (formula (1)).
R₂CO + 2CH₃OH → R₂C(OCH₃)₂ + H₂O ・・・(1)
Therefore it is necessary to use methanol-free anode and cathode solution. There are commercially available reagents with a special composition for ketones and aldehydes. However, cyclohexanone has particularly a strong side reaction activity, so it is difficult to measure by direct injection method at room temperature. In the measurement of cyclohexanone, it is effective to lower the activity of side reaction by cooling or to separate cyclohexanone and water by distillation.
This application introduces an example for the water determination in cyclohexanone with cooled direct injection method and azeotropic distillation method
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
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
