Introduction
Chromatography is an analytical technique based on the separation
of molecules due to differences in their structure
and/or composition. In general, chromatography involves
moving a sample through the system over a stationary phase.
The molecules in the sample will have different affinities and
interactions with the stationary support, leading to separation
of molecules. Sample components that display stronger interactions
with the stationary phase will move more slowly
through the column than components with weaker interactions.
Different compounds can be separated from each other
as they move through the column. Chromatographic separations
can be carried out using a variety of stationary phases, including
immobilized silica on glass plates (thin-layer chromatography),
volatile gases (gas chromatography), paper (paper
chromatography) and liquids (liquid chromatography).
High-performance liquid chromatography (HPLC) is a type
of liquid chromatography used to separate and quantify compounds
that have been dissolved in solution. HPLC is used to
determine the amount of a specific compound in a solution.
For example, HPLC can be used to determine the amount of
morphine in a compounded solution. In HPLC and liquid
chromatography, where the sample solution is in contact with a
second solid or liquid phase, the different solutes in the sample
solution will interact with the stationary phase as described.
The differences in interaction with the column can help separate
different sample components from each other.