Page 130 - Illustrated Pocket Dictionary of Chromatography

MOLECULAR WEIGHT CALIBRATION CURVE 129

CH 3
Si O Si CH 2 CH 2 CN
Surface O CH 3

CH 3
Si O Si CH 2 (CH 2 ) 16 CH 3
CH 3
Mixed-mode

mobile phase In HPLC, TLC, and CZE the mobile phase is a liquid
that moves through/past a stationary phase and causes separation. In
GC separations, the mobile phase is a gas (often called the carrier gas).

mobile-phase modifier See modifier.
mobility See electrophoretic mobility, m.

modifier A component added to the mobile phase, typically at a
low level, to alter its chemical and/or physical properties and enhance
the efficiency of the separation.

molar absorptivity, e A parameter that appears in Beer’s law (A
=ebC) and is a function of the degree of interaction that a specific
analyte has with the incident radiation at a known wavelength in a
defined solvent conditions (composition, pH, temperature, etc).
The units for e are L/[mol◊cm] (when b, the cell path length, is in
cm, and the concentration, C, is molarity). Another term used for
molar absorptivity is the molar extinction coefficient.

molarity, M A unit of measure of concentration; units are moles/
liter.

molecular imprinting The process of creating stationary phases
that have exact analyte negative images grafted onto them.
molecular weight calibration curve The plot of molecular
weight versus retention volume is typically used to characterize the
molecular weight distribution for polymeric sample. A representative
plot is shown below. The calibration curve should be made with a
series of standards that are comprised of the same material as that