Determination of Water Content By Karl Fischer Method in 2-Propylamine
Product Group
Amines
Section Overview
General Information for Water Determination in Amines
Weakly alkaline amines pose no problems in the water determination after Karl Fischer and can be titrated according to standard methods. For strongly alkaline amines, the buffer capacity of the Karl Fischer solution is not sufficient. A shift of pH into the alkaline range leads to a side reaction of the iodine. This can be recognized by the dragging end points, or a continuous consumption of iodine solution, respectively. If turn-off criteria are reached nevertheless, the result is too high. This side reaction, caused by the disproportionation of iodine molecules above pH 8, can be avoided through additional buffering of the working medium with a weak acid. Aquastar® buffer solution for strong bases, benzoic or salicylic acid, is the most suitable because, unlike acetic acid, they do not show any tendency for esterification in the Karl Fischer solution. The acids are added to the solvent prior to titration and can even be employed in excess. Some amines react with the Karl Fischer solution. Measures to suppress or overcome this side reaction are, for example, titration in methanol-free working media, utilization of small sample sizes, as well as titration to a fast end point.
Methods for Water Determination in Isopropyl Amine Sample
2-Propylamine has fairly strong alkaline properties. Titration with two-component reagents is preferred due to the better buffering of the Karl Fischer solvent. Through the addition of Aquastar® buffer solution for strong bases, benzoic - or salicylic acid, the amount of substance that can be determined in the Karl Fischer solvent increases.
One-Component Volumetric Karl Fischer Titration
Karl Fischer Reagents:
- Karl Fischer Titrant
Aquastar® - CombiTitrant 5 (1.88005) - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 5 mg water
or
Aquastar® - CombiTitrant 2 (1.88002) - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 2 mg water - Karl Fischer Solvent
20 mL Aquastar® - CombiMethanol (1.88009) - Solvent for volumetric Karl Fischer titration with one component reagents, max. 0.01 % water
and
30 mL Aquastar® - buffer solution for strong bases (1.88036)- buffer for volumetric KF titration
Titration Parameters:
Default titration settings, e.g.: I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion for fast titration: drift < 30 µL/min
Sample size:
1 mL
Titration Procedure:
The titration medium is first placed into the cell and titrated dry by means of the titrant. Then the sample is added with a syringe (exact sample weight determination by weighing the syringe before and after injection), and the titration is started. Titration is carried out to fast end point.
Two-Component Volumetric Karl Fischer Titration
Karl Fischer Reagents:
- Karl Fischer Titrant
Aquastar® - Titrant 5 (1.88010) - Titrant for volumetric titration with two component reagents, 1 mL = approx. 5 mg water
or
Aquastar® - Titrant 2 (1.88011) - Titrant for volumetric titration with two component reagents, 1 mL = approx. 2 mg water - Karl Fischer Solvent
20 mL Aquastar® - Solvent (1.88015) - Solvent for volumetric titration with two component reagents
and
30 mL Aquastar® - buffer solution for strong bases (1.88036) - buffer for volumetric KF titration
Titration Parameters:
Default titration settings, e.g.,:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion for fast titration: drift < 30 µL/min
Sample size:
1 mL
Titration Procedure:
The titration medium is first placed into the cell and titrated dry by means of the titrant. Then the sample is added with a syringe (exact sample weight determination by weighing the syringe before and after injection), and the titration is started. Titration is carried out to fast end point.
Coulometric Karl Fischer Titration (With Diaphragm)
Karl Fischer Reagents:
- Catholyte
5 mL Aquastar® - CombiCoulomat frit (1.09255) - Coulometric Karl Fischer reagent for cells with diaphragm
- Anolyte
100 mL Aquastar® - CombiCoulomat frit (1.09255) - Coulometric Karl Fischer reagent for cells with diaphragm
and
20 g benzoic acid (1.00136) - as buffer substance
Titration Parameters:
Default coulometer settings for cell with diaphragm:
For end point indication, e.g.:
I(pol) = 5 - 10 µA, U(EP) = 50 - 100 mV
Stop criterion for fast titration: drift < 15 µg/min
Sample size:
0.5 mL
Titration Procedure:
The Karl-Fischer reagent is placed into the cathode and anode compartments of the titration cell with a diaphragm. The coulometer is started, and the solvent is titrated dry. After preliminary titration and stabilization of drift, the sample is injected into the titration cell with a syringe (exact sample weight determination by weighing the syringe before and after injection), and the water determination is started. Titration is carried out to fast end point.
Coulometric Karl Fischer Titration (Without Diaphragm)
Karl Fischer Reagents:
- Working medium
100 mL Aquastar® - CombiCoulomat fritless (1.09257) - Coulometric Karl Fischer reagent for cells with or without diaphragm
and
20 g benzoic acid (1.00136) - as a buffer substance
Titration Parameters:
Default coulometer settings for cells without a diaphragm:
For end point indication, e.g.:
I(pol) = 5 - 10 µA, U(EP) = 50 - 100 mV
Stop criterion for fast titration: drift < 15 µg/min
Sample size:
0.5 mL
Titration Procedure:
The Karl-Fischer reagent is placed into the titration cell without a diaphragm. The coulometer is started, and the solvent is titrated dry. After preliminary titration and stabilization of drift, the sample is injected into the titration cell with a syringe (exact sample weight determination by weighing the syringe before and after injection), and the water determination is started. Titration is carried out to fast end point.
계속 읽으시려면 로그인하거나 계정을 생성하세요.
계정이 없으십니까?