B.14.1 Solvent miscibility
Before you change solvents, refer to the table below to determine solvent miscibility. Be aware of
these effects:
• Changes involving two miscible solvents can be made directly. Changes involving two
solvents that are not totally miscible (for example, from chloroform to water) require an
intermediate solvent like n-propanol.
• Temperature affects solvent miscibility. If you are running a high-temperature application,
consider the effect of the higher temperature on solvent solubility.
• Buffers dissolved in water can precipitate when mixed with organic solvents.
• When you switch from a strong buffer to an organic solvent, thoroughly flush the system with
distilled water before you add the organic solvent.
Note:
λ cutoff is the wavelength at which the absorbance of the solvent equals 1 AU.
Table B–2: Solvent miscibility
Polarity
index
Solvent
Viscosity cP,
20 °C (at 1
atm)
Boiling
point °C (at
1 atm)
Miscibility
number (M)
λ cutoff
(nm)
0.0
N-hexane
0.313
68.7
29
—
1.8
Triethylamine
0.38
89.5
26
—
4.2
Tetrahydrofuran (THF) 0.55
66.0
17
220
4.3
1-propanol
2.30
97.2
15
210
4.3
2-propanol
2.35
117.7
15
—
5.2
Ethanol
1.20
78.3
14
210
5.4
Acetone
0.32
56.3
15, 17
330
5.5
Benzyl alcohol
5.80
205.5
13
—
5.7
Methoxyethanol
1.72
124.6
13
—
6.2
Acetonitrile
0.37
81.6
11, 17
190
6.2
Acetic acid
1.26
117.9
14
—
6.4
Dimaethylformamide
0.90
153.0
12
—
6.5
Dimethlysulfoxide
2.24
189.0
9
—
6.6
Methanol
0.60
64.7
12
210
9.0
Water
1.00
100.0
—
—
B.14.1.1 Using miscibility numbers (M-numbers)
Use miscibility numbers (M-numbers) to predict the miscibility of a liquid with a standard solvent.
August 8, 2016, 715005049 Rev. C
Page 94
