Waters ACQUITY UPLC M-Class System Manual page 104

D Solvent Considerations
Solvent miscibility: (Continued)
Polarity
Solvent
index
5.7 Methoxyethanol
6.2 Acetonitrile
6.2 Acetic acid
6.4 Dimethylformamide
6.5 Dimethylsulfoxide
6.6 Methanol
9.0 Water
Using miscibility numbers (M-numbers)
Use miscibility numbers (M-numbers) to predict the miscibility of a liquid
with a standard solvent.
To predict the miscibility of two liquids, subtract the smaller M-number value
from the larger M-number value.
• When the difference between the two M-numbers is 15 or less, the two
liquids are miscible, in all proportions, at 15°C.
• A difference of 16 indicates a critical solution temperature from 25 to
75 °C, with 50 °C as the optimal temperature.
• When the difference is 17 or greater, the liquids are immiscible, or their
critical solution temperature is above 75 °C.
Some solvents prove immiscible with solvents at both ends of the lipophilicity
scale. These solvents receive a dual M-number:
• The first number, always lower than 16, indicates the degree of
miscibility with highly lipophilic solvents.
• The second number applies to the opposite end of the scale. A large
difference between these two numbers indicates a limited range of
miscibility.
For example, some fluorocarbons are immiscible with all the standard
solvents and have M-numbers of 0 and 32. Two liquids with dual M-numbers
are usually miscible with each other.
104 March 10, 2014, 715003588 Rev. A
Viscosity Boiling
cP, 20 °C point °C
(@1 atm) (@1 atm)
1.72 124.6
0.37 81.6
1.26 117.9
0.90 153.0
2.24 189.0
0.60 64.7
1.00 100.0
Miscibility
λ Cutoff
number
(nm)
(M)
13 ––
11, 17 190
14 ––
12 ––
9 ––
12 210
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