gel filtration 3

Resolution in Gel Filtration:
Final resolution, the degree of separation between peaks, is influenced by many factors:
the ratio of sample volume to column volume, flow rate, column dimensions, particle size particle size distribution, packing density, porosity of the particle and viscosity of the mobile phase. The success of gel filtration depends primarily on choosing conditions that give sufficient selectivity and counteract peak broadening effects during the separation.
Resolution (Rs) is defined by the following expression:

Vr2 – Vr1
Rs =
(W1 + W2)
2
Vr1 and Vr2 are the elution volumes for two adjacent peaks measured at the center of the peak. W1 and W2 are the respective peak widths.
(Vr2 – Vr1) represents the distance between the peaks and 1/2 (W1 + W2) the mean peak width of the two peaks as shown in Figure.
Resolution is a function of the selectivity of the medium and the efficiency of that medium to produce narrow peaks (minimal peak broadening) as illustrated in down figure. The efficiency of a packed column defines its ability to produce narrow symmetrical peaks during elution. Efficiency is particularly important in gel filtration in which separation takes place as only a single column volume of buffer passes through the column.
Efficiency is defined in terms of theoretical plates per meter (N):
N = 5.54 (Ve/W1/2)2 × 1000/L
Where:
Ve = peak elution (retention) volume
W1/2 = peak width at half peak height
L = bed height (mm)
Ve and W1/2 are in same units