Page 145 - Illustrated Pocket Dictionary of Chromatography

145
PERMEABILITY, B o
pellicular Defines a particle that has a solid nonporous core and a
thin porous coating atop the core. Pellicular materials are ideal for
use in precolumns or in separations that do not require high overall
efficiencies.

pentane Molecular weight: 72.2; boiling point: 36.1°C; refractive
index (20°C): 1.3575; density (20°C): 0.63g/mL; viscosity (20°C):
o
0.23cP; UV cutoff: 190nm; eluotropic strength (e ): on alumina—0.0,
on silica—0.0; polarity index (P¢): 0.0; solubility in water (20°C): 0.04%;
water solubility in pentane (20°C): 0.009%, Extremely volatile and
flammable. Pentane is rarely used in HPLC or TLC because of its very
high volatility. It is more commonly used as a sample solvent of GC.

CH 3 CH 2 CH 2 CH 2 CH 3
Pentane

perfluorotributylamine (PFTBA) A compound commonly used
in the calibration and tuning of a quadrapole MS detector coupled to
a GC.

(CF 3 CF 2 CF 2 CF 2 ) 3 N
PFTBA

perfusion chromatography An LC technique that is used for
the separation of macromolecules. It uses support material that has
very large pores (≥300 Å) so that the macromolecules can access
them.

permeation The ability of an analyte to enter/exit pores in the
packing material; implies that there is no interaction of the analyte
with the packing material surface. Permeation is the primary “reten-
tion” mechanism that is sought in size exclusion separations.

A measure of the resistance a column generates
permeability, B o
to the flow of mobile phase through it and is mathematically described
as:
2
B o = [d e 3 ] 180 [1 - ] e 2
p
where e is the porosity and d p is the particle diameter.