Page 37 - Illustrated Pocket Dictionary of Chromatography

32 CHLORINATED SOLVENTS

celluloses), (4) Chiral affinity proteins (e.g., bovine serum albumin),
and (5) Ligand exchangers (e.g., amino acids fully complexed with
transition metal ions such as copper).

chlorinated solvents Chlorinated solvents have found extensive
use as liquid-liquid extraction solvents (e.g., carbon tetrachloride,
chloroform, methylene chloride), as sample solvents in GC (methyl-
ene chloride), and as mobile-phase components in LC and TLC (chlo-
roform, methylene chloride, butyl chloride) and SEC (chlorobenzene
and 1,2-dichlorobenzene, 1,2,4-trichlorobenzene). It should be noted
that many chloroalkane solvents are unstable (e.g., methylene chlo-
ride, chloroform) and decompose into free radical compounds and
HCl. Both the free radical compounds and HCl can be reactive toward
analytes and cause degradation of columns. To counteract this, many
manufacturers add “preservatives” such as amylene and cyclohexene
that are present to react with the decomposition products. Aromatic
chlorinated solvents (e.g., chlorobenzene) are stable and are often
used in high-temperature SEC analyses. The biggest drawback to their
use is their incompatibility with UV detectors, because the cutoff
wavelength is typically 290nm or above.

1-chlorobutane See n-butyl chloride.
chloroform Molecular weight: 119.4; boiling point: 61°C; refractive
index (20°C): 1.4458; density (20°C): 1.49g/mL; viscosity (20°C):
o
0.57cP; UV cutoff: 245nm; eluotropic strength (e ): on alumina—
0.40, on silica—0.26; polarity index (P¢): 4.1; Hildebrand solubility
parameter (d): 9.2; solubility in water (20°C): 0.8%; water solubility in
chloroform (20°C): 0.056%. Very volatile. Chloroform is frequently
used in liquid-liquid extractions, is routinely used as a sample solvent
in GC and TLC applications, and receives limited use in HPLC and
SEC applications. Because of its susceptibility for degradation,
chloroform is sold with amylene and ethanol (up to 2%) added as
preservative.

CHCl 3
Chloroform

chlorosilanes A class of compounds having the general structure: