Page 31 - Illustrated Pocket Dictionary of Chromatography

26 CAPILLARY FLOW

capillary flow The main transfer mechanism for the mobile phase
in a thin-layer chromatography plate. This action occurs because
of the free energy gain, DE, experienced by a solvent entering a
capillary:

DE =-2g V m r

where g is the surface tension of the mobile phase, V m is the molar
volume of the mobile phase, and r is the radius of the capillary.

capillary isoelectric focusing (CIEF) A technique in which a
capillary is filled with an established pH gradient solution and the
sample is moved, in the presence of solution ampholytes and an
applied electric field, to the pH at which its charge is effectively
neutralized.

carbon disulfide Molecular weight: 76.1; boiling point: 46.3°C;
refractive index (20°C): 1.6280; density (20°C): 1.26g/mL; viscosity
(20°C): 0.37cP; solubility in water (20°C): 0.22%; water solubility in
carbon disulfide (25°C): 0.01%; polarity index (P¢): 0.3. Very volatile,
highly toxic. Stench. Carbon disulfide is a solvent used in GC
for sample desorption from extremely nonpolar surfaces such as
charcoal.

S C S
Carbon disulfide
carbon load The amount of bonded phase chemically attached to
a support material, often determined through the elemental analysis
of the carbon level. Carbon load is expressed as the carbon weight
per support weight (w/w or w%). The larger the carbon load, the more
bonded phase is on the surface. Note that the elemental determina-
tion cannot determine between bonded phase (e.g., C18) and end-
capping; both are carbon-based. In general, for alkyl bonded phases,
the higher the carbon load the more hydrophobic the support
material.
carbon tetrachloride Molecular weight: 153.8; boiling point:
76.7°C; refractive index (20°C): 1.4601; density (20°C): 1.59g/mL;
o
viscosity (20°C): 0.97cP; UV cutoff: 263nm; eluotropic strength (e ):
on alumina—0.18, on silica—0.11; polarity index (P¢): 1.7; Hildebrand