Chemistry Reference
In-Depth Information
are critical to the type of separations illustrated in Figure 3.3. Figure 3.3 shows
six overlaid chromatograms of a method requiring critical resolution of a series of
minor components. Without accurate and precise mobile phase generation and sol-
vent delivery, this critical resolution could not be maintained. Isocratic conditions,
if desired for the final method, can be determined from gradient conditions, and of
course still be run on the gradient system.
3.4.1 hPlc S
yStemS
for
c
olumn
And
m
ethod
S
coutIng
Method and column scouting is a method development approach commonly used to
investigate potential starting conditions for further method optimization. A typical
HPLC system used to generate the kind of results obtained in Figures 3.2 and 3.3
and run scouting experiments is shown in Figure 3.4. Most major LC manufacturers'
systems can be similarly configured into a resulting method development workhorse
system to generate the kind of results obtained in Figure 3.3 and run column scouting
experiments where the mobile phase can be varied over a range of conditions, includ-
ing organic content and pH. In addition to the basic solvent and sample manager, sys-
tems for method development are often configured with solvent and column switching
valves, a column oven, and multiple detector capabilities (Section 3.4.6). For the most
part, photodiode array (PDA) and single quadrupole mass spectrometry (MS) are
the most useful detectors for method development. Other useful detectors include
evaporative light scattering (ELSD) or corona charged aerosol (CAD). Systems con-
figured in this manner are capable of delivering mobile phases consisting of different
A6
A1
A3
A4
A5
A2
A
BCD
Solvent selector valve
Software controlled
column switching valve
FIgure 3.4
Example of a typical HPLC system configured for method development.
(Reprinted from HPLC method development for pharmaceuticals, Volume 8 of
Separation
Science and Technology
, S. Ahuja, Editor, Chapter 6, Contemporary liquid chromatographic
systems for method development, p. 151, 2007.)
