Development of Karl Fischer Reagents

II-1. Organic Compounds
4. Ethers
78
Key Points
The moisture content of ethers can be measured readily using direct
titration. End-points are stable and highly accurate analytical results are
obtainable. The behavior of ethers is similar to that of hydrocarbons.
Both volumetric and coulometric titration can be used.
With volumetric titration, the sample is dissolved in a general-use
dehydrated solvent and measured. Solubility may be inadequate with
ethers that have a high carbon number. In such cases we recommend
the use of dehydrated solvents formulated for use with oils.
In the ether group, the following compounds need special care:
Substances that have double bonding and cause interference - Vinyl
ether (Note 1)
For coulometric titration, add the sample to the electrolyte solution
(anolyte) and take the measurement. With most ethers, measurement
can be carried out without difficulty. With propylene oxide, however,
there is a limit to the quantity of sample that can be added (Note 2).
Examples of substances that can be measured directly:
Dimethyl ether, diethyl ether, isopropyl ether, ethylene oxide, tetramethylene
oxide, methyl carbitol, diethylene glycol, ethylene glycol dimethyl ether,
diphenyl ether, dioxane, tetrahydrofuran
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
General-use Dehydrated Solvent GEX (or MS) 25-50ml
Substance
�-Butyrolactam
Dioxane
Tetrahydrofuran
Propylene oxide
Ethyl vinyl ether
n-Butyl vinyl ether
2,3-Dihydrofuran
Dehydrated
solvent
General-use
"
"
"
"
"
"
Sample
quantity (g)
5.6364
4.9618
2.4548
4.3472
0.1833
0.1657
0.2647
Measurement
value (mg)
1.18
1.13
2.96
3.09
0.59
0.10
0.65
Moisture
content (ppm)
209
228
1206
711
3200
600
2400