Page 115 - Illustrated Pocket Dictionary of Chromatography

112 ISO-OCTANE, 2,2,4-TRIMETHYLPENTANE

iso-octane, 2,2,4-trimethylpentane Molecular weight: 114.2;
boiling point: 99.2°C; refractive index (20°C): 1.3914; density (20°C):
0.69g/mL; viscosity (20°C): 0.50cP; UV cutoff: 215nm; eluotropic
o
strength (e ): on alumina—0.01, on silica—0.01; polarity index (P¢):
0.4; Hildebrand solubility parameter (d): 6.9; solubility in water (25°C):
0.0002% water; water solubility in iso-octane (20°C): 0.006%. Volatile
and flammable. Iso-octane is used as a solvent in GC analyses and as
solvent in HPLC and TLC.

CH 3 CH 3
CH 3 CCH 2 CHCH 3
CH 3
Iso-octane

isopropyl alcohol, 2-propanol (IPA) Molecular weight: 60.1;
boiling point: 82.3°C; refractive index (20°C): 1.3772; density (20°C):
0.79g/mL; viscosity (20°C): 2.4cP; UV cutoff: 205nm; eluotropic
o
strength (e ): on alumina—0.82, on silica—0.60; polarity index (P¢):
4.3; Hildebrand solubility parameter (d): 11.5. Miscible with water.
Volatile and flammable. IPA is known as a “universal” solvent in that
it is miscible with an extremely wide range of commonly used polar
and nonpolar solvents. [Note that this fact does not imply anything
about the solubility of salts and buffers in IPA.] Because of this quality,
IPA is used as the intermediate solvent when changing from HPLC
reversed-phase systems (i.e., aqueous/organic solvents) to normal-
phase systems (i.e., nonpolar solvents) and vise versa. IPA is also used
as a mobile-phase component in both reversed- and normal-phase LC
separation. However, the high viscosity of IPA-water mixtures in the
20–60% range lead to unacceptably high operating backpressure.

OH
CH 3 CHCH 3
Isopropyl alcohol