1.
Summary of Method
方法概要
1.1
Scope
范围
This method is applicable for determining free water or water of
hydration in solid or liquid organic homogenous compound that is soluble in KF solvents.
这个方法应用于游离水份、固体或液体有机物在卡尔费休溶剂中的可溶结合水。
1.2
Principle
原理
The sample is dissolved or dispersed in a suitable solvent and titrated with Karl Fischer reagent.
As long as water is present, the iodine will be reduced to colourless hydrogen iodide.
The end-point is the first appearance of free iodine, determined electrometrically.
1.3
Interferences
A number of substances and classes of compounds interfere in the determination of water by this titrimetric method.
This interference is associated with condensation or oxidation-reduction reactions.
The solubility of the sample in the solvent is another interference.
Samples that are insoluble or partially soluble in the testing solvent may lead to incomplete dissolution of its water into the solvent and thus resulting in an incomplete titration.
2.
Apparatus
仪器设备
2.1
with double platinum electrode (part.no. 6.0340.000)
2.2
Balance, readable to 0.001 g
2.3
Borosilicate glass sample vessel
2.4
Magnetic, Telfon-coated stirring bar
2.5
Metrohm 824 sample changer, or equivalent
2.6
Metrohm 665 dosimat, or equivalent
2.7
Aluminum foil (part.no. 6.2820.000)
3.
Reagents (Unless otherwise specified, analytical grade chemical should be used.)
试剂（除非另有说明，否则使用分析纯的药品）
3.1
Karl Fischer Reagents, commercially available
3.1.1
Karl Fischer Solvent - HYDRANAL Solvent (RDH 34800).
3.1.2
Karl Fischer Solvent - HYDRANAL Solvent CM (RDH 34812).
3.1.3
Karl Fischer titrant - HYDRANAL Titrant 5 (RDH 34801).
3.2
Chloroform
3.3
Self-prepared solvent
Two portion of chloroform is mixed with one portion of HYDRANAL Solvent (RDH 34800)
3.4
Deionized water
3.5
QC samples
3.4.1
Water in ethylene glycol, about 5%.
Weigh about 5 g of DI water in 95g of ethylene glycol.
3.4.2
Water in peanut oil, about 2%.
Weigh about 2 g of DI water in 98 g of peanut oil.
4.
Procedure
程序
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