卡爾費休測水份

1.
Summary of Method
             方法概要

1.1
Scope
                          范圍
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.
          這個方法應用于游離水份、固體或液體有機物在卡爾費休溶劑中的可溶結合水。

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
            儀器設備
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.)
             試劑（除非另有說明，否則使用分析純的藥品）

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

能傳個附件上來嗎？？有點看不明白！！

Water in peanut oil, about 2%.
Weigh about 2 g of DI water in 98 g of peanut oil.

這個東西不好做啊，單位檢測過一些，結果不理想

國家標物中心現在有專做這個的標物，有三種規格