Page 74 - Illustrated Pocket Dictionary of Chromatography

70 ETHYL ACETATE

(e.g., THF). Many ethers are unstable and readily form peroxides that,
if they become concentrated enough, can pose an explosion hazard.
As a consequence, many ethers have preservatives added to them that
prevent the buildup of peroxides in the solvent. Nevertheless, the lab-
oratory stock of ethers should be routinely used or replaced as per
the documented shelf life instructions of the manufacturer.

ethyl acetate Molecular weight: 88.1; boiling point: 77°C; refrac-
tive index (20°C): 1.3724; density (20°C): 0.90g/mL; viscosity (20°C):
o
0.45cP; UV cutoff: 260nm; eluotropic strength (e ): on alumina—0.58,
on silica—0.48; polarity index (P¢): 4.3; Hildebrand solubility parame-
ter (d): 9.1; solubility in water (20°C): 8.7%; water solubility in ethyl
acetate (20°C): 3.3%. Ethyl acetate is most commonly used in TLC,
liquid-liquid extractions, and sample preparation. Because of its mod-
erately high UV cutoff, its use in HPLC is as a low-percentage mobile-
phase component.

O

H 3 C OCH 2 CH 3
Ethyl acetate

ethyl ether, diethyl ether Molecular weight: 74.1; boiling point:
35°C; refractive index (20°C): 1.3524; density (20°C): 0.71g/mL; viscos-
o
ity (20°C): 0.24cP; UV cutoff: 215nm; eluotropic strength (e ): on
alumina—0.38, on silica—0.43; polarity index (P¢): 2.8; solubility in
water (20°C): 6.9%; water solubility in ethyl acetate (20°C): 1.3%. Ethyl
ether is a very common solvent used in liquid-liquid extraction because
of the ease with which it can be evaporated. It is also used to a lesser
degree in TLC and HPLC. Ethyl ether is prone to forming peroxides and
is often preserved with ethanol. High volatility and flammability make
special handling precautions necessary.

H 3 CH 2 COCH 2 CH 3
Ethyl ether

evaporative light-scattering detector (ELSD) Useful for ana-
lytes that are nonvolatile and have no chromophores or fluorophores.
In an ELSD the column effluent is nebulized, vaporized to produce