Page 16 - BR20828_E Accucore 0713S

Comparison of Column Pressure for Accucore
2.6 µm and Fully Porous 5, 3 and Sub-2 µm
From equation 1, it is clear that reducing the particle size
in the column significantly increases the observed
pressure drop across the column. The data in Figure 1
was generated on 100 × 2.1 mm columns, using a
mixture (1:1) of acetonitrile and water, at 30 °C column
temperature and running flow rates in the range 0.1 to
1 mL/min. The pressure measured on the Accucore
2.6 µm column is approximately half of that on the
sub-2 µm particle packed column and double that of the
3 µm particle packed column. Based on particle size
only, and given that the pressure drop across the column
is inversely proportional to the square of the particle
diameter, the ratio between the measured pressure on
the sub-2 µm and Accucore columns should be 1.9, and
between the 3 µm and Accucore should be 1.3. However,
column permeability also depends on the interstitial
porosity (as indicated in equation 1) and this parameter
accounts for the observed differences in measured
pressure ratios versus those predicted based only on
particle size.
Chromatographic systems that have the conventional
pressure limit of 400 bar will reduce the effective flow
rate range that can be used on a column packed with
small particles. On standard HPLC systems, sub-2 µm
particle packed columns can only be run at reduced flow
rates, often below the flow rate that provides the best
performance. However, the Accucore column used in this
comparison can be operated at 800 µL/min, double the
optimal flow rate, before it experiences the same issues.
Effect of Column Length and Column ID
on Pressure
Pressure is directly proportional to column length. The
data in Figure 2 was obtained when Accucore columns
with length of 30, 50, 100, 150 and 200 mm were run at
400 µL/min with a mobile phase of water/acetonitrile
(1:1) and the measured pressure matches well with the
predicted values.
Figure 1: Comparison of column pressure for Accucore 2.6 µm and fully porous 5, 3 and sub-2 µm. Columns: 100 × 2.1 mm; mobile phase:
water/acetonitrile (1:1); temperature: 30 °C; flow rate: 0.1 to 1.0 mL/min.
Figure 2: Pressure drop across Accucore 2.6 µm columns of different lengths, at a flow rate of 400 µL/min, mobile phase of
water/acetonitrile (1:1) and temperature of 30 °C.