2D-LC User Guide 365
14 Theoretical Background
Theoretical basis of 2D-LC
Resolution
A chromatographic separation can be optimized based on physical parameters
of the HPLC column such as particle size, pore size, morphology of the particles,
the length and diameter of the column, the solvent velocity, and the temperature.
In addition, the thermodynamics of a separation can be considered and the
properties of the solute and the stationary and mobile phases (percentage of
organic solvent, ion strength, and pH) can be manipulated to achieve the shortest
possible retention and highest selectivity.
1D-LC Resolution (R
S
) can be described as a function of three parameters:
• Column efficiency or theoretical plates (N),
• Selectivity (),
• Retention factor (k).
Figure 170 Resolution equation
This means that the selection of appropriate mobile and stationary phase
properties and temperature is critical in achieving a successful separation.
Resolution in a one-dimensional separation usually is measured with:
Following results of this formula are important in practice:
• R > 1.5
Peaks are completely baseline resolved
• R > 1
Difference in retention time is larger than peak broadening, and therefore peak
spacing is adequate to observe distinct component zones
• R < 0.5
Peaks are completely fused
R = Resolution
Δt = Difference in retention time maxima of two components
= Average standard deviation of two Gaussian peaks
To Next Page
Loading...
Need help?
General
